net/

http_loader.rs

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */

use std::collections::HashSet;
use std::iter::FromIterator;
use std::sync::Arc as StdArc;
use std::time::{Duration, SystemTime};

use async_recursion::async_recursion;
use content_security_policy::percent_encoding::{AsciiSet, CONTROLS, utf8_percent_encode};
use devtools_traits::ChromeToDevtoolsControlMsg;
use embedder_traits::{AuthenticationResponse, GenericEmbedderProxy};
use futures::{TryFutureExt, TryStreamExt, future};
use headers::authorization::Basic;
use headers::{
    AccessControlAllowCredentials, AccessControlAllowHeaders, AccessControlAllowMethods,
    AccessControlMaxAge, AccessControlRequestMethod, Authorization, CacheControl, ContentLength,
    HeaderMapExt, IfModifiedSince, LastModified, Pragma, Referer, StrictTransportSecurity,
    UserAgent,
};
use http::header::{
    self, ACCEPT, ACCESS_CONTROL_ALLOW_ORIGIN, ACCESS_CONTROL_REQUEST_HEADERS, AUTHORIZATION,
    CONTENT_ENCODING, CONTENT_LANGUAGE, CONTENT_LOCATION, CONTENT_TYPE, HeaderValue, RANGE,
    WWW_AUTHENTICATE,
};
use http::{HeaderMap, Method, Request as HyperRequest, StatusCode};
use http_body_util::combinators::BoxBody;
use http_body_util::{BodyExt, Full};
use hyper::Response as HyperResponse;
use hyper::body::{Bytes, Frame};
use hyper::ext::ReasonPhrase;
use hyper::header::{HeaderName, TRANSFER_ENCODING};
use ipc_channel::IpcError;
use ipc_channel::ipc::{self, IpcSender};
use ipc_channel::router::ROUTER;
use log::{debug, error, info, log_enabled, warn};
use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
use net_traits::blob_url_store::UrlWithBlobClaim;
use net_traits::fetch::headers::get_value_from_header_list;
use net_traits::http_status::HttpStatus;
use net_traits::policy_container::{EmbedderPolicyValue, RequestPolicyContainer};
use net_traits::pub_domains::{is_same_site, reg_suffix};
use net_traits::request::{
    BodyChunkRequest, BodyChunkResponse, CacheMode, CredentialsMode, Destination, Initiator,
    Origin, RedirectMode, Referrer, Request, RequestBuilder, RequestClient, RequestMode,
    ResponseTainting, ServiceWorkersMode, TraversableForUserPrompts, get_cors_unsafe_header_names,
    is_cors_non_wildcard_request_header_name, is_cors_safelisted_method,
    is_cors_safelisted_request_header,
};
use net_traits::response::{CacheState, RedirectTaint, Response, ResponseBody, ResponseType};
use net_traits::{
    CookieSource, DOCUMENT_ACCEPT_HEADER_VALUE, NetworkError, RedirectEndValue, RedirectStartValue,
    ReferrerPolicy, ResourceAttribute, ResourceFetchTimingContainer, ResourceTimeValue,
    TlsSecurityInfo, TlsSecurityState,
};
use parking_lot::{Mutex, RwLock};
use profile_traits::mem::{Report, ReportKind};
use profile_traits::path;
#[cfg(feature = "tracing")]
use profile_traits::trace_span;
use rustc_hash::FxHashMap;
use servo_base::cross_process_instant::CrossProcessInstant;
use servo_base::generic_channel::GenericSharedMemory;
use servo_base::id::{BrowsingContextId, HistoryStateId, PipelineId};
use servo_url::{ImmutableOrigin, ServoUrl};
use tokio::sync::mpsc::{
    Receiver as TokioReceiver, Sender as TokioSender, UnboundedReceiver, UnboundedSender, channel,
    unbounded_channel,
};
use tokio_stream::wrappers::ReceiverStream;
#[cfg(feature = "tracing")]
use tracing::Instrument;

use crate::async_runtime::spawn_task;
use crate::connector::{
    CertificateErrorOverrideManager, ServoClient, TlsHandshakeInfo, create_tls_config,
};
use crate::cookie::ServoCookie;
use crate::cookie_storage::CookieStorage;
use crate::decoder::Decoder;
use crate::devtools::{
    prepare_devtools_request, send_request_to_devtools, send_response_values_to_devtools,
};
use crate::embedder::NetToEmbedderMsg;
use crate::fetch::cors_cache::CorsCache;
use crate::fetch::fetch_params::FetchParams;
use crate::fetch::headers::{SecFetchDest, SecFetchMode, SecFetchSite, SecFetchUser};
use crate::fetch::methods::{Data, DoneChannel, FetchContext, Target, main_fetch};
use crate::hsts::HstsList;
use crate::http_cache::{
    CacheKey, CachedResourcesOrGuard, HttpCache, construct_response, invalidate_cached_resources,
    refresh,
};
use crate::resource_thread::{AuthCache, AuthCacheEntry};
use crate::websocket_loader::start_websocket;

/// The various states an entry of the HttpCache can be in.
#[derive(Clone, Debug, Eq, PartialEq)]
pub enum HttpCacheEntryState {
    /// The entry is fully up-to-date,
    /// there are no pending concurrent stores,
    /// and it is ready to construct cached responses.
    ReadyToConstruct,
    /// The entry is pending a number of concurrent stores.
    PendingStore(usize),
}

pub struct HttpState {
    pub hsts_list: RwLock<HstsList>,
    pub cookie_jar: RwLock<CookieStorage>,
    pub http_cache: HttpCache,
    pub auth_cache: RwLock<AuthCache>,
    pub history_states: RwLock<FxHashMap<HistoryStateId, Vec<u8>>>,
    pub client: ServoClient,
    pub override_manager: CertificateErrorOverrideManager,
    pub embedder_proxy: GenericEmbedderProxy<NetToEmbedderMsg>,
}

impl HttpState {
    pub(crate) fn memory_reports(&self, suffix: &str, ops: &mut MallocSizeOfOps) -> Vec<Report> {
        vec![
            Report {
                path: path!["memory-cache", suffix],
                kind: ReportKind::ExplicitJemallocHeapSize,
                size: self.http_cache.size_of(ops),
            },
            Report {
                path: path!["hsts-list", suffix],
                kind: ReportKind::ExplicitJemallocHeapSize,
                size: self.hsts_list.read().size_of(ops),
            },
        ]
    }

    async fn request_authentication(
        &self,
        request: &Request,
        response: &Response,
    ) -> Option<AuthenticationResponse> {
        // We do not make an authentication request for non-WebView associated HTTP requests.
        let webview_id = request.target_webview_id?;
        let for_proxy = response.status == StatusCode::PROXY_AUTHENTICATION_REQUIRED;

        // If this is not actually a navigation request return None.
        if request.mode != RequestMode::Navigate {
            return None;
        }

        let (sender, receiver) = tokio::sync::oneshot::channel();
        self.embedder_proxy
            .send(NetToEmbedderMsg::RequestAuthentication(
                webview_id,
                request.url(),
                for_proxy,
                sender,
            ));
        receiver.await.ok()?
    }
}

/// Step 11 of <https://fetch.spec.whatwg.org/#concept-fetch>.
pub(crate) fn set_default_accept(request: &mut Request) {
    // Step 11. If request’s header list does not contain `Accept`, then:
    if request.headers.contains_key(header::ACCEPT) {
        return;
    }

    // Step 11.2. If request’s initiator is "prefetch", then set value to the document `Accept` header value.
    let value = if request.initiator == Initiator::Prefetch {
        DOCUMENT_ACCEPT_HEADER_VALUE
    } else {
        // Step 11.3. Otherwise, the user agent should set value to the first matching statement,
        // if any, switching on request’s destination:
        match request.destination {
            Destination::Document | Destination::Frame | Destination::IFrame => {
                DOCUMENT_ACCEPT_HEADER_VALUE
            },
            Destination::Image => {
                HeaderValue::from_static("image/png,image/svg+xml,image/*;q=0.8,*/*;q=0.5")
            },
            Destination::Json => HeaderValue::from_static("application/json,*/*;q=0.5"),
            Destination::Style => HeaderValue::from_static("text/css,*/*;q=0.1"),
            // Step 11.1. Let value be `*/*`.
            _ => HeaderValue::from_static("*/*"),
        }
    };

    // Step 11.4. Append (`Accept`, value) to request’s header list.
    request.headers.insert(header::ACCEPT, value);
}

fn set_default_accept_encoding(headers: &mut HeaderMap) {
    if headers.contains_key(header::ACCEPT_ENCODING) {
        return;
    }

    // TODO(eijebong): Change this once typed headers are done
    headers.insert(
        header::ACCEPT_ENCODING,
        HeaderValue::from_static("gzip, deflate, br, zstd"),
    );
}

/// <https://w3c.github.io/webappsec-referrer-policy/#referrer-policy-state-no-referrer-when-downgrade>
fn no_referrer_when_downgrade(referrer_url: ServoUrl, current_url: ServoUrl) -> Option<ServoUrl> {
    // Step 1
    if referrer_url.is_potentially_trustworthy() && !current_url.is_potentially_trustworthy() {
        return None;
    }
    // Step 2
    strip_url_for_use_as_referrer(referrer_url, false)
}

/// <https://w3c.github.io/webappsec-referrer-policy/#referrer-policy-strict-origin>
fn strict_origin(referrer_url: ServoUrl, current_url: ServoUrl) -> Option<ServoUrl> {
    // Step 1
    if referrer_url.is_potentially_trustworthy() && !current_url.is_potentially_trustworthy() {
        return None;
    }
    // Step 2
    strip_url_for_use_as_referrer(referrer_url, true)
}

/// <https://w3c.github.io/webappsec-referrer-policy/#referrer-policy-strict-origin-when-cross-origin>
fn strict_origin_when_cross_origin(
    referrer_url: ServoUrl,
    current_url: ServoUrl,
) -> Option<ServoUrl> {
    // Step 1
    if referrer_url.origin() == current_url.origin() {
        return strip_url_for_use_as_referrer(referrer_url, false);
    }
    // Step 2
    if referrer_url.is_potentially_trustworthy() && !current_url.is_potentially_trustworthy() {
        return None;
    }
    // Step 3
    strip_url_for_use_as_referrer(referrer_url, true)
}

/// <https://html.spec.whatwg.org/multipage/#schemelessly-same-site>
fn is_schemelessy_same_site(site_a: &ImmutableOrigin, site_b: &ImmutableOrigin) -> bool {
    // Step 1
    if !site_a.is_tuple() && !site_b.is_tuple() && site_a == site_b {
        true
    } else if site_a.is_tuple() && site_b.is_tuple() {
        // Step 2.1
        let host_a = site_a.host().map(|h| h.to_string()).unwrap_or_default();
        let host_b = site_b.host().map(|h| h.to_string()).unwrap_or_default();

        let host_a_reg = reg_suffix(&host_a);
        let host_b_reg = reg_suffix(&host_b);

        // Step 2.2-2.3
        (site_a.host() == site_b.host() && host_a_reg.is_empty()) ||
            (host_a_reg == host_b_reg && !host_a_reg.is_empty())
    } else {
        // Step 3
        false
    }
}

/// <https://w3c.github.io/webappsec-referrer-policy/#strip-url>
fn strip_url_for_use_as_referrer(mut url: ServoUrl, origin_only: bool) -> Option<ServoUrl> {
    const MAX_REFERRER_URL_LENGTH: usize = 4096;
    // Step 2
    if url.is_local_scheme() {
        return None;
    }
    // Step 3-6
    {
        let url = url.as_mut_url();
        let _ = url.set_username("");
        let _ = url.set_password(None);
        url.set_fragment(None);
        // Note: The result of serializing referrer url should not be
        // greater than 4096 as specified in Step 6 of
        // https://w3c.github.io/webappsec-referrer-policy/#determine-requests-referrer
        if origin_only || url.as_str().len() > MAX_REFERRER_URL_LENGTH {
            url.set_path("");
            url.set_query(None);
        }
    }
    // Step 7
    Some(url)
}

/// <https://w3c.github.io/webappsec-referrer-policy/#referrer-policy-same-origin>
fn same_origin(referrer_url: ServoUrl, current_url: ServoUrl) -> Option<ServoUrl> {
    // Step 1
    if referrer_url.origin() == current_url.origin() {
        return strip_url_for_use_as_referrer(referrer_url, false);
    }
    // Step 2
    None
}

/// <https://w3c.github.io/webappsec-referrer-policy/#referrer-policy-origin-when-cross-origin>
fn origin_when_cross_origin(referrer_url: ServoUrl, current_url: ServoUrl) -> Option<ServoUrl> {
    // Step 1
    if referrer_url.origin() == current_url.origin() {
        return strip_url_for_use_as_referrer(referrer_url, false);
    }
    // Step 2
    strip_url_for_use_as_referrer(referrer_url, true)
}

/// <https://w3c.github.io/webappsec-referrer-policy/#determine-requests-referrer>
pub fn determine_requests_referrer(
    referrer_policy: ReferrerPolicy,
    referrer_source: ServoUrl,
    current_url: ServoUrl,
) -> Option<ServoUrl> {
    match referrer_policy {
        ReferrerPolicy::EmptyString | ReferrerPolicy::NoReferrer => None,
        ReferrerPolicy::Origin => strip_url_for_use_as_referrer(referrer_source, true),
        ReferrerPolicy::UnsafeUrl => strip_url_for_use_as_referrer(referrer_source, false),
        ReferrerPolicy::StrictOrigin => strict_origin(referrer_source, current_url),
        ReferrerPolicy::StrictOriginWhenCrossOrigin => {
            strict_origin_when_cross_origin(referrer_source, current_url)
        },
        ReferrerPolicy::SameOrigin => same_origin(referrer_source, current_url),
        ReferrerPolicy::OriginWhenCrossOrigin => {
            origin_when_cross_origin(referrer_source, current_url)
        },
        ReferrerPolicy::NoReferrerWhenDowngrade => {
            no_referrer_when_downgrade(referrer_source, current_url)
        },
    }
}

fn set_request_cookies(
    url: &ServoUrl,
    headers: &mut HeaderMap,
    cookie_jar: &RwLock<CookieStorage>,
) {
    let mut cookie_jar = cookie_jar.write();
    cookie_jar.remove_expired_cookies_for_url(url);
    if let Some(cookie_list) = cookie_jar.cookies_for_url(url, CookieSource::HTTP) {
        headers.insert(
            header::COOKIE,
            HeaderValue::from_bytes(cookie_list.as_bytes()).unwrap(),
        );
    }
}

fn set_cookie_for_url(cookie_jar: &RwLock<CookieStorage>, request: &ServoUrl, cookie_val: &str) {
    let mut cookie_jar = cookie_jar.write();
    let source = CookieSource::HTTP;

    if let Some(cookie) = ServoCookie::from_cookie_string(cookie_val, request, source) {
        cookie_jar.push(cookie, request, source);
    }
}

fn set_cookies_from_headers(
    url: &ServoUrl,
    headers: &HeaderMap,
    cookie_jar: &RwLock<CookieStorage>,
) {
    for cookie in headers.get_all(header::SET_COOKIE) {
        let cookie_bytes = cookie.as_bytes();
        if !ServoCookie::is_valid_name_or_value(cookie_bytes) {
            continue;
        }
        if let Ok(cookie_str) = std::str::from_utf8(cookie_bytes) {
            set_cookie_for_url(cookie_jar, url, cookie_str);
        }
    }
}

fn build_tls_security_info(handshake: &TlsHandshakeInfo, hsts_enabled: bool) -> TlsSecurityInfo {
    // Simplified security state determination:
    // Servo uses rustls, which only supports TLS 1.2+ and secure cipher suites (GCM, ChaCha20-Poly1305).
    // rustls does NOT support TLS 1.0, TLS 1.1, SSL, or weak ciphers (RC4, 3DES, CBC, etc).
    // Therefore, any successful TLS connection is secure by design.
    //
    // We only check for missing handshake information as a defensive measure.

    let state = if handshake.protocol_version.is_none() || handshake.cipher_suite.is_none() {
        // Missing handshake information indicates an incomplete or failed connection
        TlsSecurityState::Insecure
    } else {
        // rustls guarantees TLS 1.2+ with secure ciphers
        TlsSecurityState::Secure
    };

    TlsSecurityInfo {
        state,
        weakness_reasons: Vec::new(), // rustls never negotiates weak crypto
        protocol_version: handshake.protocol_version.clone(),
        cipher_suite: handshake.cipher_suite.clone(),
        kea_group_name: handshake.kea_group_name.clone(),
        signature_scheme_name: handshake.signature_scheme_name.clone(),
        alpn_protocol: handshake.alpn_protocol.clone(),
        certificate_chain_der: handshake.certificate_chain_der.clone(),
        certificate_transparency: None,
        hsts: hsts_enabled,
        hpkp: false,
        used_ech: handshake.used_ech,
        used_delegated_credentials: false,
        used_ocsp: false,
        used_private_dns: false,
    }
}

fn auth_from_cache(
    auth_cache: &RwLock<AuthCache>,
    origin: &ImmutableOrigin,
) -> Option<Authorization<Basic>> {
    if let Some(auth_entry) = auth_cache.read().entries.get(&origin.ascii_serialization()) {
        let user_name = &auth_entry.user_name;
        let password = &auth_entry.password;
        Some(Authorization::basic(user_name, password))
    } else {
        None
    }
}

/// Messages from the IPC route to the fetch worker,
/// used to fill the body with bytes coming-in over IPC.
enum BodyChunk {
    /// A chunk of bytes.
    Chunk(GenericSharedMemory),
    /// Body is done.
    Done,
}

/// The stream side of the body passed to hyper.
enum BodyStream {
    /// A receiver that can be used in Body::wrap_stream,
    /// for streaming the request over the network.
    Chunked(TokioReceiver<Result<Frame<Bytes>, hyper::Error>>),
    /// A body whose bytes are buffered
    /// and sent in one chunk over the network.
    Buffered(UnboundedReceiver<BodyChunk>),
}

/// The sink side of the body passed to hyper,
/// used to enqueue chunks.
enum BodySink {
    /// A Tokio sender used to feed chunks to the network stream.
    Chunked(TokioSender<Result<Frame<Bytes>, hyper::Error>>),
    /// A Crossbeam sender used to send chunks to the fetch worker,
    /// where they will be buffered
    /// in order to ensure they are not streamed them over the network.
    Buffered(UnboundedSender<BodyChunk>),
}

impl BodySink {
    fn transmit_bytes(&self, bytes: GenericSharedMemory) {
        match self {
            BodySink::Chunked(sender) => {
                let sender = sender.clone();
                spawn_task(async move {
                    let _ = sender
                        .send(Ok(Frame::data(Bytes::copy_from_slice(&bytes))))
                        .await;
                });
            },
            BodySink::Buffered(sender) => {
                let _ = sender.send(BodyChunk::Chunk(bytes));
            },
        }
    }

    fn close(&self) {
        match self {
            BodySink::Chunked(_) => { /* no need to close sender */ },
            BodySink::Buffered(sender) => {
                let _ = sender.send(BodyChunk::Done);
            },
        }
    }
}

fn request_body_stream_closed_error(action: &str) -> NetworkError {
    NetworkError::Crash(format!(
        "Request body stream has already been closed while trying to {action}."
    ))
}

fn log_request_body_stream_closed(action: &str, error: Option<&IpcError>) {
    match error {
        Some(error) => {
            error!("Request body stream has already been closed while trying to {action}: {error}")
        },
        None => error!("Request body stream has already been closed while trying to {action}."),
    }
}

fn log_fetch_terminated_send_failure(terminated_with_error: bool, context: &str) {
    warn!(
        "Failed to notify request-body stream termination state ({terminated_with_error}) while {context} because the receiver was already dropped."
    );
}

const FRAGMENT: &AsciiSet = &CONTROLS.add(b'|').add(b'{').add(b'}');

#[allow(clippy::too_many_arguments)]
#[servo_tracing::instrument(skip_all, fields(url=url.as_str()))]
/// This sets up the callback infrastructure to send body frames to `body_sender` and fires the client request.
async fn obtain_response(
    client: &ServoClient,
    url: &ServoUrl,
    method: &Method,
    request_headers: &mut HeaderMap,
    body_sender: Option<StdArc<Mutex<Option<IpcSender<BodyChunkRequest>>>>>,
    source_is_null: bool,
    pipeline_id: &Option<PipelineId>,
    request_id: Option<&str>,
    destination: Destination,
    is_xhr: bool,
    context: &FetchContext,
    fetch_terminated: UnboundedSender<bool>,
    browsing_context_id: Option<BrowsingContextId>,
) -> Result<(HyperResponse<Decoder>, Option<ChromeToDevtoolsControlMsg>), NetworkError> {
    let mut headers = request_headers.clone();

    let devtools_bytes = StdArc::new(Mutex::new(vec![]));

    // https://url.spec.whatwg.org/#percent-encoded-bytes
    let encoded_url = utf8_percent_encode(url.as_str(), FRAGMENT).to_string();

    let request = if let Some(chunk_requester) = body_sender {
        let (sink, stream) = if source_is_null {
            // Step 4.2 of https://fetch.spec.whatwg.org/#concept-http-network-fetch
            // TODO: this should not be set for HTTP/2(currently not supported?).
            headers.insert(TRANSFER_ENCODING, HeaderValue::from_static("chunked"));

            let (sender, receiver) = channel(1);
            (BodySink::Chunked(sender), BodyStream::Chunked(receiver))
        } else {
            // Note: Hyper seems to already buffer bytes when the request appears not stream-able,
            // see https://github.com/hyperium/hyper/issues/2232#issuecomment-644322104
            //
            // However since this doesn't appear documented, and we're using an ancient version,
            // for now we buffer manually to ensure we don't stream requests
            // to servers that might not know how to handle them.
            let (sender, receiver) = unbounded_channel();
            (BodySink::Buffered(sender), BodyStream::Buffered(receiver))
        };

        obtain_response_setup_router_callback(
            devtools_bytes.clone(),
            chunk_requester,
            sink,
            fetch_terminated,
        )?;

        let body = match stream {
            BodyStream::Chunked(receiver) => {
                let stream = ReceiverStream::new(receiver);
                BoxBody::new(http_body_util::StreamBody::new(stream))
            },
            BodyStream::Buffered(mut receiver) => {
                // Accumulate bytes received over IPC into a vector.
                let mut body = vec![];
                loop {
                    match receiver.recv().await {
                        Some(BodyChunk::Chunk(bytes)) => {
                            body.extend_from_slice(&bytes);
                        },
                        Some(BodyChunk::Done) => break,
                        None => warn!("Failed to read all chunks from request body."),
                    }
                }
                Full::new(body.into()).map_err(|_| unreachable!()).boxed()
            },
        };
        HyperRequest::builder()
            .method(method)
            .uri(encoded_url)
            .body(body)
    } else {
        HyperRequest::builder()
            .method(method)
            .uri(encoded_url)
            .body(
                http_body_util::Empty::new()
                    .map_err(|_| unreachable!())
                    .boxed(),
            )
    };

    // TODO(#21261) connect_start: set if a persistent connection is *not* used and the last non-redirected
    // fetch passes the timing allow check
    let connect_start = CrossProcessInstant::now();
    context.timing.set_attributes(&[
        ResourceAttribute::DomainLookupStart,
        ResourceAttribute::ConnectStart(connect_start),
    ]);

    // TODO: We currently don't know when the handhhake before the connection is done
    // so our best bet would be to set `secure_connection_start` here when we are currently
    // fetching on a HTTPS url.
    if url.scheme() == "https" {
        context
            .timing
            .set_attribute(ResourceAttribute::SecureConnectionStart);
    }

    let mut request = match request {
        Ok(request) => request,
        Err(error) => return Err(NetworkError::HttpError(error.to_string())),
    };
    *request.headers_mut() = headers.clone();

    let connect_end = CrossProcessInstant::now();
    context
        .timing
        .set_attribute(ResourceAttribute::ConnectEnd(connect_end));

    let request_id = request_id.map(|v| v.to_owned());
    let pipeline_id = *pipeline_id;
    let closure_url = url.clone();
    let method = method.clone();
    let send_start = CrossProcessInstant::now();

    let host = request.uri().host().unwrap_or("").to_owned();
    let override_manager = context.state.override_manager.clone();
    let headers = headers.clone();
    let is_secure_scheme = url.is_secure_scheme();

    // Generally, we use a persistent connection, so we will also set other PerformanceResourceTiming
    //   attributes to this as well (domain_lookup_start, domain_lookup_end, connect_start, connect_end,
    //   secure_connection_start)
    context
        .timing
        .set_attribute(ResourceAttribute::RequestStart);

    let client_future = client
        .request(request)
        .and_then(move |res| {
            let send_end = CrossProcessInstant::now();

            // TODO(#21271) response_start: immediately after receiving first byte of response

            let msg = if let Some(request_id) = request_id {
                if let Some(pipeline_id) = pipeline_id {
                    if let Some(browsing_context_id) = browsing_context_id {
                        Some(prepare_devtools_request(
                            request_id,
                            closure_url,
                            method.clone(),
                            headers,
                            Some(devtools_bytes.lock().clone()),
                            pipeline_id,
                            (connect_end - connect_start).unsigned_abs(),
                            (send_end - send_start).unsigned_abs(),
                            destination,
                            is_xhr,
                            browsing_context_id,
                        ))
                    } else {
                        debug!("Not notifying devtools (no browsing_context_id)");
                        None
                    }
                    // TODO: ^This is not right, connect_start is taken before contructing the
                    // request and connect_end at the end of it. send_start is takend before the
                    // connection too. I'm not sure it's currently possible to get the time at the
                    // point between the connection and the start of a request.
                } else {
                    debug!("Not notifying devtools (no pipeline_id)");
                    None
                }
            } else {
                debug!("Not notifying devtools (no request_id)");
                None
            };

            future::ready(Ok((
                Decoder::detect(res.map(|r| r.boxed()), is_secure_scheme),
                msg,
            )))
        })
        .map_err(move |error| {
            warn!("network error: {error:?}");
            NetworkError::from_hyper_error(
                &error,
                override_manager.remove_certificate_failing_verification(host.as_str()),
            )
        });

    #[cfg(feature = "tracing")]
    {
        client_future.instrument(trace_span!("HyperRequest")).await
    }

    #[cfg(not(feature = "tracing"))]
    {
        client_future.await
    }
}

/// Setup the callback mechanism to forward chunks from the request received to the `chunk_requester`.
fn obtain_response_setup_router_callback(
    devtools_bytes: StdArc<Mutex<Vec<u8>>>,
    chunk_requester: StdArc<Mutex<Option<IpcSender<BodyChunkRequest>>>>,
    sink: BodySink,
    fetch_terminated: UnboundedSender<bool>,
) -> Result<(), NetworkError> {
    let (body_chan, body_port) = ipc::channel().unwrap();

    {
        let mut lock = chunk_requester.lock();
        if let Some(chunk_requester) = lock.as_mut() {
            if let Err(error) = chunk_requester.send(BodyChunkRequest::Connect(body_chan)) {
                log_request_body_stream_closed("connect to the request body stream", Some(&error));
                return Err(request_body_stream_closed_error(
                    "connect to the request body stream",
                ));
            }

            // https://fetch.spec.whatwg.org/#concept-request-transmit-body
            // Request the first chunk, corresponding to Step 3 and 4.
            if let Err(error) = chunk_requester.send(BodyChunkRequest::Chunk) {
                log_request_body_stream_closed(
                    "request the first request body chunk",
                    Some(&error),
                );
                return Err(request_body_stream_closed_error(
                    "request the first request body chunk",
                ));
            }
        } else {
            log_request_body_stream_closed("connect to the request body stream", None);
            return Err(request_body_stream_closed_error(
                "connect to the request body stream",
            ));
        }
    }

    ROUTER.add_typed_route(
        body_port,
        Box::new(move |message| {
            info!("Received message");
            let bytes = match message.unwrap() {
                BodyChunkResponse::Chunk(bytes) => bytes,
                BodyChunkResponse::Done => {
                    // Step 3, abort these parallel steps.
                    if fetch_terminated.send(false).is_err() {
                        log_fetch_terminated_send_failure(
                            false,
                            "handling request body completion",
                        );
                    }
                    sink.close();

                    return;
                },
                BodyChunkResponse::Error => {
                    // Step 4 and/or 5.
                    // TODO: differentiate between the two steps,
                    // where step 5 requires setting an `aborted` flag on the fetch.
                    if fetch_terminated.send(true).is_err() {
                        log_fetch_terminated_send_failure(
                            true,
                            "handling request body stream error",
                        );
                    }
                    sink.close();

                    return;
                },
            };

            devtools_bytes.lock().extend_from_slice(&bytes);

            // Step 5.1.2.2, transmit chunk over the network,
            // currently implemented by sending the bytes to the fetch worker.
            sink.transmit_bytes(bytes);

            // Step 5.1.2.3
            // Request the next chunk.
            let mut chunk_requester = chunk_requester.lock();
            if let Some(chunk_requester) = chunk_requester.as_mut() {
                if let Err(error) = chunk_requester.send(BodyChunkRequest::Chunk) {
                    log_request_body_stream_closed(
                        "request the next request body chunk",
                        Some(&error),
                    );
                    if fetch_terminated.send(true).is_err() {
                        log_fetch_terminated_send_failure(
                            true,
                            "handling failure to request the next request body chunk",
                        );
                    }
                    sink.close();
                }
            } else {
                log_request_body_stream_closed("request the next request body chunk", None);
                if fetch_terminated.send(true).is_err() {
                    log_fetch_terminated_send_failure(
                        true,
                        "handling a closed request body stream while requesting the next chunk",
                    );
                }
                sink.close();
            }
        }),
    );

    Ok(())
}

/// [HTTP fetch](https://fetch.spec.whatwg.org/#concept-http-fetch)
#[async_recursion]
#[allow(clippy::too_many_arguments)]
pub(crate) async fn http_fetch(
    fetch_params: &mut FetchParams,
    cache: &mut CorsCache,
    cors_flag: bool,
    cors_preflight_flag: bool,
    authentication_fetch_flag: bool,
    target: Target<'async_recursion>,
    done_chan: &mut DoneChannel,
    context: &FetchContext,
) -> Response {
    // This is a new async fetch, reset the channel we are waiting on
    *done_chan = None;
    // Step 1. Let request be fetchParams’s request.
    let request = &mut fetch_params.request;

    // Step 2. Let response and internalResponse be null.
    let mut response: Option<Response> = None;

    // Step 3. If request’s service-workers mode is "all", then
    if request.service_workers_mode == ServiceWorkersMode::All {
        // TODO: Substep 1
        // Set response to the result of invoking handle fetch for request.

        // Substep 2
        if let Some(ref res) = response {
            // Subsubstep 1
            // TODO: transmit body for request

            // Subsubstep 2
            // nothing to do, since actual_response is a function on response

            // Subsubstep 3
            if (res.response_type == ResponseType::Opaque && request.mode != RequestMode::NoCors) ||
                (res.response_type == ResponseType::OpaqueRedirect &&
                    request.redirect_mode != RedirectMode::Manual) ||
                (res.url_list.len() > 1 && request.redirect_mode != RedirectMode::Follow) ||
                res.is_network_error()
            {
                return Response::network_error(NetworkError::ConnectionFailure);
            }

            // Subsubstep 4
            // TODO: set response's CSP list on actual_response
        }
    }

    // Step 4. If response is null, then:
    if response.is_none() {
        // Step 4.1. If makeCORSPreflight is true and one of these conditions is true:
        if cors_preflight_flag {
            let method_cache_match = cache.match_method(request, request.method.clone());

            // There is no method cache entry match for request’s method using request, and either
            // request’s method is not a CORS-safelisted method or request’s use-CORS-preflight flag
            // is set.
            let method_mismatch = !method_cache_match &&
                (!is_cors_safelisted_method(&request.method) || request.use_cors_preflight);

            // There is at least one item in the CORS-unsafe request-header names with request’s
            // header list for which there is no header-name cache entry match using request.
            let header_mismatch = request.headers.iter().any(|(name, value)| {
                !cache.match_header(request, name) &&
                    !is_cors_safelisted_request_header(&name, &value)
            });

            // Then:
            if method_mismatch || header_mismatch {
                // Step 4.1.1. Let preflightResponse be the result of running
                // CORS-preflight fetch given request.
                let preflight_response = cors_preflight_fetch(request, cache, context).await;
                // Step 4.1.2. If preflightResponse is a network error, then return preflightResponse.
                if let Some(error) = preflight_response.get_network_error() {
                    return Response::network_error(error.clone());
                }
            }
        }

        // Step 4.2. If request’s redirect mode is "follow",
        // then set request’s service-workers mode to "none".
        if request.redirect_mode == RedirectMode::Follow {
            request.service_workers_mode = ServiceWorkersMode::None;
        }

        // Step 4.3. Set response and internalResponse to the result of
        // running HTTP-network-or-cache fetch given fetchParams.
        let mut fetch_result = http_network_or_cache_fetch(
            fetch_params,
            authentication_fetch_flag,
            cors_flag,
            done_chan,
            context,
        )
        .await;

        // Step 4.4. If request’s response tainting is "cors" and a CORS check for request
        // and response returns failure, then return a network error.
        if cors_flag && cors_check(&fetch_params.request, &fetch_result).is_err() {
            return Response::network_error(NetworkError::CorsGeneral);
        }

        // Step 4.5. If the TAO check for request and response returns failure,
        // then set request’s timing allow failed flag.
        if let Err(()) = tao_check(&fetch_params.request, &fetch_result) {
            context.timing.inner().mark_timing_check_failed();
        }
        fetch_result.return_internal = false;
        response = Some(fetch_result);
    }

    let request = &mut fetch_params.request;

    // response is guaranteed to be something by now
    let mut response = response.unwrap();

    // Step 5: If either request’s response tainting or response’s type is "opaque",
    // and the cross-origin resource policy check with request’s origin, request’s client,
    // request’s destination, and internalResponse returns blocked, then return a network error.
    if (request.response_tainting == ResponseTainting::Opaque ||
        response.response_type == ResponseType::Opaque) &&
        request.client.as_ref().is_some_and(|client| {
            cross_origin_resource_policy_check(
                &request.origin,
                client,
                &response,
                ForNavigation::No,
            ) == CrossOriginResourcePolicy::Blocked
        })
    {
        return Response::network_error(NetworkError::CrossOriginResponse);
    }

    // Step 6. If internalResponse’s status is a redirect status:
    if response
        .actual_response()
        .status
        .try_code()
        .is_some_and(is_redirect_status)
    {
        // TODO Step 6.1. If request is a navigation request, then append to a request’s navigation
        // timing allow values list given request and internalResponse.

        // Step 6.2. If internalResponse’s status is not 303, request’s body is non-null,
        // and the connection uses HTTP/2, then user agents may, and are even encouraged to,
        // transmit an RST_STREAM frame.
        if response.actual_response().status != StatusCode::SEE_OTHER {
            // TODO: send RST_STREAM frame
        }

        // Step 6.3. Switch on request’s redirect mode:
        response = match request.redirect_mode {
            // Step 6.3."error".1. Set response to a network error.
            RedirectMode::Error => Response::network_error(NetworkError::RedirectError),
            RedirectMode::Manual => {
                // Step 6.3."manual".1. If request’s mode is "navigate", then set fetchParams’s controller’s
                // next manual redirect steps to run HTTP-redirect fetch given fetchParams and response.
                if request.mode == RequestMode::Navigate {
                    // TODO: We don't implement Fetch controller. Instead, we update the location url
                    // of the response here and don't call `http_redirect_fetch`. That's get called later.
                    // Once we have a fetch controller here, we should update the code as specced.
                    let location_url =
                        location_url_for_response(&response, request.current_url().fragment());
                    response.actual_response_mut().location_url = location_url;
                    response
                } else {
                    // Step 6.3."manual".2. Otherwise, set response to an opaque-redirect filtered
                    // response whose internal response is internalResponse.
                    response.to_filtered(ResponseType::OpaqueRedirect)
                }
            },
            RedirectMode::Follow => {
                // TODO Step 6.3."follow".1. Run the WebDriver BiDi response completed steps with
                // request and response.
                // set back to default
                response.return_internal = true;

                // Step 6.3."follow".2. Set response to the result of running HTTP-redirect fetch
                // given fetchParams and response.
                http_redirect_fetch(
                    fetch_params,
                    cache,
                    response,
                    cors_flag,
                    target,
                    done_chan,
                    context,
                )
                .await
            },
        };
    }

    // set back to default
    response.return_internal = true;
    context
        .timing
        .set_attribute(ResourceAttribute::RedirectCount(
            fetch_params.request.redirect_count as u16,
        ));

    response.resource_timing = context.timing.clone();

    // Step 7. Return response
    response
}

/// <https://fetch.spec.whatwg.org/#concept-tao-check>
fn tao_check(request: &Request, response: &Response) -> Result<(), ()> {
    // Step 1. Assert: request’s origin is not "client".
    let Origin::Origin(ref request_origin) = request.origin else {
        unreachable!("origin cannot be \"client\" at this point");
    };

    // Step 2. If request’s timing allow failed flag is set, then return failure.

    // Step 3. Let values be the result of getting, decoding, and splitting `Timing-Allow-Origin`
    // from response’s header list.
    let values: Vec<&str> = response
        .headers
        .get_all("Timing-Allow-Origin")
        .iter()
        .map(|header_value| header_value.to_str().unwrap_or(""))
        .collect();

    // Step 4. If values contains "*", then return success.
    if values.contains(&"*") {
        return Ok(());
    }

    // Step 5. If values contains the result of serializing a request origin with request, then
    // return success.
    if values
        .iter()
        .any(|header_str| *header_str == request_origin.ascii_serialization())
    {
        return Ok(());
    }

    // Step 6. If request’s mode is "navigate" and request’s current URL’s origin is not same origin
    // with request’s origin, then return failure.
    if request.mode == RequestMode::Navigate && request.current_url().origin() != *request_origin {
        return Err(());
    }

    // Step 7. If request’s response tainting is "basic", then return success.
    if request.response_tainting == ResponseTainting::Basic {
        return Ok(());
    }

    // Step 8. Return failure.
    Err(())
}

// Convenience struct that implements Drop, for setting redirectEnd on function return
struct RedirectEndTimer(Option<ResourceFetchTimingContainer>);

impl RedirectEndTimer {
    fn neuter(&mut self) {
        self.0 = None;
    }
}

impl Drop for RedirectEndTimer {
    fn drop(&mut self) {
        let RedirectEndTimer(resource_fetch_timing_opt) = self;

        resource_fetch_timing_opt.as_ref().map_or((), |t| {
            t.set_attribute(ResourceAttribute::RedirectEnd(RedirectEndValue::Zero));
        })
    }
}

/// <https://fetch.spec.whatwg.org/#request-body-header-name>
static REQUEST_BODY_HEADER_NAMES: &[HeaderName] = &[
    CONTENT_ENCODING,
    CONTENT_LANGUAGE,
    CONTENT_LOCATION,
    CONTENT_TYPE,
];

/// <https://fetch.spec.whatwg.org/#concept-response-location-url>
fn location_url_for_response(
    response: &Response,
    request_fragment: Option<&str>,
) -> Option<Result<ServoUrl, String>> {
    // Step 1. If response’s status is not a redirect status, then return null.
    assert!(
        response
            .actual_response()
            .status
            .try_code()
            .is_some_and(is_redirect_status)
    );
    // Step 2. Let location be the result of extracting header list values given `Location` and response’s header list.
    let mut location = response
        .actual_response()
        .headers
        .get(header::LOCATION)
        .and_then(|header_value| {
            HeaderValue::to_str(header_value)
                .map(|location_string| {
                    // Step 3. If location is a header value, then set location to the result of parsing location with response’s URL.
                    ServoUrl::parse_with_base(response.actual_response().url(), location_string)
                        .map_err(|error| error.to_string())
                })
                .ok()
        });

    // Step 4. If location is a URL whose fragment is null, then set location’s fragment to requestFragment.
    if let Some(Ok(ref mut location)) = location &&
        location.fragment().is_none()
    {
        location.set_fragment(request_fragment);
    }
    // Step 5. Return location.
    location
}

/// [HTTP redirect fetch](https://fetch.spec.whatwg.org/#http-redirect-fetch)
#[async_recursion]
pub async fn http_redirect_fetch(
    fetch_params: &mut FetchParams,
    cache: &mut CorsCache,
    mut response: Response,
    cors_flag: bool,
    target: Target<'async_recursion>,
    done_chan: &mut DoneChannel,
    context: &FetchContext,
) -> Response {
    let mut redirect_end_timer = RedirectEndTimer(Some(context.timing.clone()));

    // Step 1. Let request be fetchParams’s request.
    let request = &mut fetch_params.request;

    // Step 2. Let internalResponse be response, if response is not a filtered response; otherwise response’s internal response.
    assert!(response.return_internal);

    // Step 3. Let locationURL be internalResponse’s location URL given request’s current URL’s fragment.
    let location_url = location_url_for_response(&response, request.current_url().fragment());
    response.actual_response_mut().location_url = location_url.clone();

    let location_url = match location_url {
        // Step 4. If locationURL is null, then return response.
        None => return response,
        // Step 5. If locationURL is failure, then return a network error.
        Some(Err(err)) => {
            return Response::network_error(NetworkError::ResourceLoadError(
                "Location URL parse failure: ".to_owned() + &err,
            ));
        },
        // Step 6. If locationURL’s scheme is not an HTTP(S) scheme, then return a network error.
        Some(Ok(url)) if !matches!(url.scheme(), "http" | "https") => {
            return Response::network_error(NetworkError::UnsupportedScheme);
        },
        Some(Ok(url)) => url,
    };

    // Step 1 of https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-fetchstart
    // TODO: check origin and timing allow check
    // start_time should equal redirect_start if nonzero; else fetch_start
    // updates start_time only if redirect_start is nonzero (implying TAO)
    context.timing.set_attributes(&[
        ResourceAttribute::RedirectStart(RedirectStartValue::FetchStart),
        ResourceAttribute::FetchStart,
        ResourceAttribute::StartTime(ResourceTimeValue::FetchStart),
        ResourceAttribute::StartTime(ResourceTimeValue::RedirectStart),
    ]);

    // Step 7: If request’s redirect count is 20, then return a network error.
    if request.redirect_count >= 20 {
        return Response::network_error(NetworkError::TooManyRedirects);
    }

    // Step 8: Increase request’s redirect count by 1.
    request.redirect_count += 1;

    // Step 9. If request’s mode is "cors", locationURL includes credentials,
    // and request’s origin is not same origin with locationURL’s origin, then return a network error.
    let same_origin = match request.origin {
        Origin::Origin(ref origin) => *origin == location_url.origin(),
        Origin::Client => panic!(
            "Request origin should not be client for {}",
            request.current_url()
        ),
    };

    let has_credentials = has_credentials(&location_url);

    if request.mode == RequestMode::CorsMode && !same_origin && has_credentials {
        return Response::network_error(NetworkError::CorsCredentials);
    }

    if cors_flag && location_url.origin() != request.current_url().origin() {
        request.origin = Origin::Origin(ImmutableOrigin::new_opaque());
    }

    // Step 10. If request’s response tainting is "cors" and locationURL includes credentials, then return a network error.
    if cors_flag && has_credentials {
        return Response::network_error(NetworkError::CorsCredentials);
    }

    // Step 11: If internalResponse’s status is not 303, request’s body is non-null, and request’s
    // body’s source is null, then return a network error.
    if response.actual_response().status != StatusCode::SEE_OTHER &&
        request.body.as_ref().is_some_and(|b| b.source_is_null())
    {
        return Response::network_error(NetworkError::ConnectionFailure);
    }

    // Step 12. If one of the following is true
    if response
        .actual_response()
        .status
        .try_code()
        .is_some_and(|code| {
            // internalResponse’s status is 301 or 302 and request’s method is `POST`
            ((code == StatusCode::MOVED_PERMANENTLY || code == StatusCode::FOUND) &&
                request.method == Method::POST) ||
                // internalResponse’s status is 303 and request’s method is not `GET` or `HEAD`
                (code == StatusCode::SEE_OTHER &&
                    request.method != Method::HEAD &&
                    request.method != Method::GET)
        })
    {
        // Step 12.1. Set request’s method to `GET` and request’s body to null.
        request.method = Method::GET;
        request.body = None;
        // Step 12.2. For each headerName of request-body-header name, delete headerName from request’s header list.
        for name in REQUEST_BODY_HEADER_NAMES {
            request.headers.remove(name);
        }
    }

    // Step 13: If request’s current URL’s origin is not same origin with locationURL’s origin, then
    // for each headerName of CORS non-wildcard request-header name, delete headerName from
    // request’s header list.
    if location_url.origin() != request.current_url().origin() {
        // This list currently only contains the AUTHORIZATION header
        // https://fetch.spec.whatwg.org/#cors-non-wildcard-request-header-name
        request.headers.remove(AUTHORIZATION);
    }

    // Step 14: If request’s body is non-null, then set request’s body to the body of the result of
    // safely extracting request’s body’s source.
    if let Some(body) = request.body.as_mut() {
        body.extract_source();
    }

    // Steps 15-17 relate to timing, which is not implemented 1:1 with the spec.

    // Step 18: Append locationURL to request’s URL list.
    request
        .url_list
        .push(UrlWithBlobClaim::from_url_without_having_claimed_blob(
            location_url,
        ));

    // Step 19: Invoke set request’s referrer policy on redirect on request and internalResponse.
    set_requests_referrer_policy_on_redirect(request, response.actual_response());

    // Step 20: Let recursive be true.
    // Step 21: If request’s redirect mode is "manual", then...
    let recursive_flag = request.redirect_mode != RedirectMode::Manual;

    // Step 22: Return the result of running main fetch given fetchParams and recursive.
    let fetch_response = main_fetch(
        fetch_params,
        cache,
        recursive_flag,
        target,
        done_chan,
        context,
    )
    .await;

    // TODO: timing allow check
    context.timing.set_attribute(ResourceAttribute::RedirectEnd(
        RedirectEndValue::ResponseEnd,
    ));
    redirect_end_timer.neuter();

    fetch_response
}

/// [HTTP network or cache fetch](https://fetch.spec.whatwg.org/#concept-http-network-or-cache-fetch)
#[async_recursion]
#[servo_tracing::instrument(skip_all,fields(url=fetch_params.request.url().as_str()))]
async fn http_network_or_cache_fetch(
    fetch_params: &mut FetchParams,
    authentication_fetch_flag: bool,
    cors_flag: bool,
    done_chan: &mut DoneChannel,
    context: &FetchContext,
) -> Response {
    // Step 2. Let httpFetchParams be null.
    let http_fetch_params: &mut FetchParams;
    let mut fetch_params_copy: FetchParams;

    // Step 3. Let httpRequest be null. (See step 8 for initialization)

    // Step 4. Let response be null.
    let mut response: Option<Response> = None;

    // Step 7. Let the revalidatingFlag be unset.
    let mut revalidating_flag = false;

    // TODO(#33616): Step 8. Run these steps, but abort when fetchParams is canceled:
    // Step 8.1. If request’s traversable for user prompts is "no-traversable"
    // and request’s redirect mode is "error", then set httpFetchParams to fetchParams and httpRequest to request.
    let http_request = if fetch_params.request.traversable_for_user_prompts ==
        TraversableForUserPrompts::NoTraversable &&
        fetch_params.request.redirect_mode == RedirectMode::Error
    {
        http_fetch_params = fetch_params;
        &mut http_fetch_params.request
    }
    // Step 8.2 Otherwise:
    else {
        // Step 8.2.1 - 8.2.3: Set httpRequest to a clone of request
        // and Set httpFetchParams to a copy of fetchParams.
        fetch_params_copy =
            std::mem::replace(fetch_params, FetchParams::new(fetch_params.request.clone()));
        http_fetch_params = &mut fetch_params_copy;

        &mut http_fetch_params.request
    };

    // Step 8.3: Let includeCredentials be true if one of:
    let include_credentials = match http_request.credentials_mode {
        // request’s credentials mode is "include"
        CredentialsMode::Include => true,
        // request’s credentials mode is "same-origin" and request’s response tainting is "basic"
        CredentialsMode::CredentialsSameOrigin
            if http_request.response_tainting == ResponseTainting::Basic =>
        {
            true
        },
        _ => false,
    };

    // Step 8.4: If Cross-Origin-Embedder-Policy allows credentials with request returns false, then
    // set includeCredentials to false.
    // TODO(#33616): Requires request's client object

    // Step 8.5 Let contentLength be httpRequest’s body’s length, if httpRequest’s body is non-null;
    // otherwise null.
    let content_length = http_request
        .body
        .as_ref()
        .and_then(|body| body.len().map(|size| size as u64));

    // Step 8.6 Let contentLengthHeaderValue be null.
    let mut content_length_header_value = None;

    // Step 8.7 If httpRequest’s body is null and httpRequest’s method is `POST` or `PUT`,
    // then set contentLengthHeaderValue to `0`.
    if http_request.body.is_none() && matches!(http_request.method, Method::POST | Method::PUT) {
        content_length_header_value = Some(0);
    }

    // Step 8.8 If contentLength is non-null, then set contentLengthHeaderValue to contentLength,
    // serialized and isomorphic encoded.
    // NOTE: The header will later be serialized using HeaderMap::typed_insert
    if let Some(content_length) = content_length {
        content_length_header_value = Some(content_length);
    };

    // Step 8.9 If contentLengthHeaderValue is non-null, then append (`Content-Length`, contentLengthHeaderValue)
    // to httpRequest’s header list.
    if let Some(content_length_header_value) = content_length_header_value {
        http_request
            .headers
            .typed_insert(ContentLength(content_length_header_value));
    }

    // Step 8.10 If contentLength is non-null and httpRequest’s keepalive is true, then:
    if http_request.keep_alive &&
        let Some(content_length) = content_length
    {
        // Step 8.10.1. Let inflightKeepaliveBytes be 0.
        // Step 8.10.2. Let group be httpRequest’s client’s fetch group.
        // Step 8.10.3. Let inflightRecords be the set of fetch records
        // in group whose request’s keepalive is true and done flag is unset.
        let in_flight_keep_alive_bytes: u64 = context
            .in_flight_keep_alive_records
            .lock()
            .get(
                &http_request
                    .pipeline_id
                    .expect("Must always set a pipeline ID for keep-alive requests"),
            )
            .map(|records| {
                // Step 8.10.4. For each fetchRecord of inflightRecords:
                // Step 8.10.4.1. Let inflightRequest be fetchRecord’s request.
                // Step 8.10.4.2. Increment inflightKeepaliveBytes by inflightRequest’s body’s length.
                records
                    .iter()
                    .map(|record| {
                        if record.request_id == http_request.id {
                            // Don't double count for this request. We have already added it in
                            // `fetch::methods::fetch_with_cors_cache`
                            0
                        } else {
                            record.keep_alive_body_length
                        }
                    })
                    .sum()
            })
            .unwrap_or_default();
        // Step 8.10.5. If the sum of contentLength and inflightKeepaliveBytes is greater than 64 kibibytes, then return a network error.
        if content_length + in_flight_keep_alive_bytes > 64 * 1024 {
            return Response::network_error(NetworkError::TooManyInFlightKeepAliveRequests);
        }
    }

    // Step 8.11: If httpRequest’s referrer is a URL, then:
    match http_request.referrer {
        Referrer::ReferrerUrl(ref http_request_referrer) |
        Referrer::Client(ref http_request_referrer) => {
            // Step 8.11.1: Let referrerValue be httpRequest’s referrer, serialized and isomorphic
            // encoded.
            if let Ok(referer) = http_request_referrer.as_str().parse::<Referer>() {
                // Step 8.11.2: Append (`Referer`, referrerValue) to httpRequest’s header list.
                http_request.headers.typed_insert(referer);
            } else {
                // This error should only happen in cases where hyper and rust-url disagree
                // about how to parse a referer.
                // https://github.com/servo/servo/issues/24175
                error!("Failed to parse {} as referrer", http_request_referrer);
            }
        },
        _ => {},
    };

    // Step 8.12 Append a request `Origin` header for httpRequest.
    append_a_request_origin_header(http_request);

    // Step 8.13 Append the Fetch metadata headers for httpRequest.
    append_the_fetch_metadata_headers(http_request);

    // Step 8.14: If httpRequest’s initiator is "prefetch", then set a structured field value given
    // (`Sec-Purpose`, the token "prefetch") in httpRequest’s header list.
    if http_request.initiator == Initiator::Prefetch &&
        let Ok(value) = HeaderValue::from_str("prefetch")
    {
        http_request.headers.insert("Sec-Purpose", value);
    }

    // Step 8.15: If httpRequest’s header list does not contain `User-Agent`, then user agents
    // should append (`User-Agent`, default `User-Agent` value) to httpRequest’s header list.
    if !http_request.headers.contains_key(header::USER_AGENT) {
        http_request
            .headers
            .typed_insert::<UserAgent>(context.user_agent.parse().unwrap());
    }

    // Steps 8.16 to 8.18
    append_cache_data_to_headers(http_request);

    // Step 8.19: If httpRequest’s header list contains `Range`, then append (`Accept-Encoding`,
    // `identity`) to httpRequest’s header list.
    if http_request.headers.contains_key(header::RANGE) &&
        let Ok(value) = HeaderValue::from_str("identity")
    {
        http_request.headers.insert("Accept-Encoding", value);
    }

    // Step 8.20: Modify httpRequest’s header list per HTTP. Do not append a given header if
    // httpRequest’s header list contains that header’s name.
    // `Accept`, `Accept-Charset`, and `Accept-Language` must not be included at this point.
    http_request.headers.remove(header::HOST);
    // unlike http_loader, we should not set the accept header here
    set_default_accept_encoding(&mut http_request.headers);

    let current_url = http_request.current_url();

    // Step 8.21: If includeCredentials is true, then:
    // TODO some of this step can't be implemented yet
    if include_credentials {
        // Substep 1
        // TODO http://mxr.mozilla.org/servo/source/components/net/http_loader.rs#504
        // XXXManishearth http_loader has block_cookies: support content blocking here too
        set_request_cookies(
            &current_url,
            &mut http_request.headers,
            &context.state.cookie_jar,
        );
        // Substep 2
        if !http_request.headers.contains_key(header::AUTHORIZATION) {
            // Substep 3
            let mut authorization_value = None;

            // Substep 4
            if let Some(basic) = auth_from_cache(&context.state.auth_cache, &current_url.origin()) &&
                (!http_request.use_url_credentials || !has_credentials(&current_url))
            {
                authorization_value = Some(basic);
            }

            // Substep 5
            if authentication_fetch_flag &&
                authorization_value.is_none() &&
                has_credentials(&current_url)
            {
                authorization_value = Some(Authorization::basic(
                    current_url.username(),
                    current_url.password().unwrap_or(""),
                ));
            }

            // Substep 6
            if let Some(basic) = authorization_value {
                http_request.headers.typed_insert(basic);
            }
        }
    }

    // TODO(#33616) Step 8.22 If there’s a proxy-authentication entry, use it as appropriate.
    let should_wait = {
        // Enter critical section on cache entry.
        let mut cache_guard = block_for_cache_ready(
            context,
            http_request,
            done_chan,
            &mut revalidating_flag,
            &mut response,
        )
        .await;

        // TODO(#33616): Step 9. If aborted, then return the appropriate network error for fetchParams.

        // Step 10. If response is null, then:
        if response.is_none() {
            // Step 10.1 If httpRequest’s cache mode is "only-if-cached", then return a network error.
            if http_request.cache_mode == CacheMode::OnlyIfCached {
                // Exit critical section of cache entry.
                return Response::network_error(NetworkError::CacheError);
            }

            // Step 10.2 Let forwardResponse be the result of running HTTP-network fetch given httpFetchParams,
            // includeCredentials, and isNewConnectionFetch.
            drop(cache_guard);
            let forward_response =
                http_network_fetch(http_fetch_params, include_credentials, done_chan, context)
                    .await;

            let http_request = &mut http_fetch_params.request;
            let request_key = CacheKey::new(http_request);
            cache_guard = context
                .state
                .http_cache
                .get_or_guard(request_key.clone())
                .await;
            // Step 10.3 If httpRequest’s method is unsafe and forwardResponse’s status is in the range 200 to 399,
            // inclusive, invalidate appropriate stored responses in httpCache, as per the
            // "Invalidating Stored Responses" chapter of HTTP Caching, and set storedResponse to null.
            if forward_response.status.in_range(200..=399) && !http_request.method.is_safe() {
                if let Some(guard) = cache_guard.try_as_mut() {
                    invalidate_cached_resources(guard);
                }
                context
                    .state
                    .http_cache
                    .invalidate_related_urls(http_request, &forward_response, &request_key)
                    .await;
            }

            // Step 10.4 If the revalidatingFlag is set and forwardResponse’s status is 304, then:
            if revalidating_flag && forward_response.status == StatusCode::NOT_MODIFIED {
                // Ensure done_chan is None,
                // since the network response will be replaced by the revalidated stored one.
                *done_chan = None;
                if let Some(guard) = cache_guard.try_as_mut() {
                    response = refresh(http_request, forward_response.clone(), done_chan, guard);
                }

                if let Some(response) = &mut response {
                    response.cache_state = CacheState::Validated;
                }
            }

            // Step 10.5 If response is null, then:
            if response.is_none() {
                // Step 10.5.1 Set response to forwardResponse.
                let forward_response = response.insert(forward_response);

                // Per https://httpwg.org/specs/rfc9111.html#response.cacheability we must not cache responses
                // if the No-Store directive is present
                if http_request.cache_mode != CacheMode::NoStore {
                    // Step 10.5.2 Store httpRequest and forwardResponse in httpCache, as per the
                    //             "Storing Responses in Caches" chapter of HTTP Caching.
                    cache_guard.insert(http_request, forward_response);
                }
            }
            false
        } else {
            true
        }
    }; // Exit Critical Section on cache entry

    if should_wait {
        // If the cache constructed a response, and that is still receiving from the network,
        // we must wait for it to finish in case it is still receiving from the network.
        // Note: this means only the fetch from which the original network response originated
        // will be able to stream it; all others receive a cached response in one chunk.
        wait_for_inflight_requests(done_chan, &mut response).await;
    }

    let http_request = &mut http_fetch_params.request;
    let mut response = response.unwrap();

    // Step 11. Set response’s URL list to a clone of httpRequest’s URL list.
    response.url_list = http_request
        .url_list
        .iter()
        .map(|claimed_url| claimed_url.url())
        .collect();

    // Step 12. If httpRequest’s header list contains `Range`, then set response’s range-requested flag.
    if http_request.headers.contains_key(RANGE) {
        response.range_requested = true;
    }

    // Step 13. Set response’s request-includes-credentials to includeCredentials.
    response.request_includes_credentials = include_credentials;

    // Step 14. If response’s status is 401, httpRequest’s response tainting is not "cors",
    // includeCredentials is true, and request’s window is an environment settings object, then:
    // TODO(#33616): Figure out what to do with request window objects
    // NOTE: Requiring a WWW-Authenticate header here is ad-hoc, but seems to match what other browsers are
    // doing. See Step 14.1.
    if response.status.try_code() == Some(StatusCode::UNAUTHORIZED) &&
        !cors_flag &&
        include_credentials &&
        response.headers.contains_key(WWW_AUTHENTICATE)
    {
        // TODO: Step 14.1 Spec says requires testing on multiple WWW-Authenticate headers

        let request = &mut fetch_params.request;

        // Step 14.2 If request’s body is non-null, then:
        if request.body.is_some() {
            // TODO Implement body source
        }

        // Step 14.3 If request’s use-URL-credentials flag is unset or isAuthenticationFetch is true, then:
        if !request.use_url_credentials || authentication_fetch_flag {
            let Some(credentials) = context
                .state
                .request_authentication(request, &response)
                .await
            else {
                return response;
            };

            if let Err(err) = request
                .current_url_mut()
                .set_username(&credentials.username)
            {
                error!("error setting username for url: {:?}", err);
                return response;
            };

            if let Err(err) = request
                .current_url_mut()
                .set_password(Some(&credentials.password))
            {
                error!("error setting password for url: {:?}", err);
                return response;
            };
        }

        // Make sure this is set to None,
        // since we're about to start a new `http_network_or_cache_fetch`.
        *done_chan = None;

        // Step 14.4 Set response to the result of running HTTP-network-or-cache fetch given fetchParams and true.
        response = http_network_or_cache_fetch(
            fetch_params,
            true, /* authentication flag */
            cors_flag,
            done_chan,
            context,
        )
        .await;
    }

    // Step 15. If response’s status is 407, then:
    if response.status == StatusCode::PROXY_AUTHENTICATION_REQUIRED {
        let request = &mut fetch_params.request;
        // Step 15.1 If request’s traversable for user prompts is "no-traversable", then return a network error.

        if request.traversable_for_user_prompts == TraversableForUserPrompts::NoTraversable {
            return Response::network_error(NetworkError::ResourceLoadError(
                "Can't find Window object".into(),
            ));
        }

        // (Step 15.2 does not exist, requires testing on Proxy-Authenticate headers)

        // TODO(#33616): Step 15.3 If fetchParams is canceled, then return
        // the appropriate network error for fetchParams.

        // Step 15.4 Prompt the end user as appropriate in request’s window
        // window and store the result as a proxy-authentication entry.
        let Some(credentials) = context
            .state
            .request_authentication(request, &response)
            .await
        else {
            return response;
        };

        // Store the credentials as a proxy-authentication entry.
        let entry = AuthCacheEntry {
            user_name: credentials.username,
            password: credentials.password,
        };
        {
            let mut auth_cache = context.state.auth_cache.write();
            let key = request.current_url().origin().ascii_serialization();
            auth_cache.entries.insert(key, entry);
        }

        // Make sure this is set to None,
        // since we're about to start a new `http_network_or_cache_fetch`.
        *done_chan = None;

        // Step 15.5 Set response to the result of running HTTP-network-or-cache fetch given fetchParams.
        response = http_network_or_cache_fetch(
            fetch_params,
            false, /* authentication flag */
            cors_flag,
            done_chan,
            context,
        )
        .await;
    }

    // TODO(#33616): Step 16. If all of the following are true:
    // * response’s status is 421
    // * isNewConnectionFetch is false
    // * request’s body is null, or request’s body is non-null and request’s body’s source is non-null
    // then: [..]

    // Step 17. If isAuthenticationFetch is true, then create an authentication entry for request and the given realm.
    if authentication_fetch_flag {
        // TODO(#33616)
    }

    // Step 18. Return response.
    response
}

/// If the cache is not ready to construct a response, wait.
///
/// The cache is not ready if a previous fetch checked the cache, found nothing,
/// and moved on to a network fetch, and hasn't updated the cache yet with a pending resource.
///
/// Note that this is a different workflow from the one involving `wait_for_cached_response`.
/// That one happens when a fetch gets a cache hit, and the resource is pending completion from the network.
#[servo_tracing::instrument(skip_all)]
async fn block_for_cache_ready<'a>(
    context: &'a FetchContext,
    http_request: &mut Request,
    done_chan: &mut DoneChannel,
    revalidating_flag: &mut bool,
    response: &mut Option<Response>,
) -> CachedResourcesOrGuard<'a> {
    let entry_key = CacheKey::new(http_request);
    let guard_result = context.state.http_cache.get_or_guard(entry_key).await;

    match guard_result {
        CachedResourcesOrGuard::Guard(_) => {
            *done_chan = None;
        },
        CachedResourcesOrGuard::Value(ref cached_resources) => {
            // TODO(#33616): Step 8.23 Set httpCache to the result of determining the
            // HTTP cache partition, given httpRequest.
            // Step 8.25.1 Set storedResponse to the result of selecting a response from the httpCache,
            //              possibly needing validation, as per the "Constructing Responses from Caches"
            //              chapter of HTTP Caching, if any.
            let stored_response = construct_response(http_request, done_chan, cached_resources);
            // Step 8.25.2 If storedResponse is non-null, then:
            if let Some(response_from_cache) = stored_response {
                let response_headers = response_from_cache.response.headers.clone();
                // Substep 1, 2, 3, 4
                let (cached_response, needs_revalidation) =
                    match (http_request.cache_mode, &http_request.mode) {
                        (CacheMode::ForceCache, _) => (Some(response_from_cache.response), false),
                        (CacheMode::OnlyIfCached, &RequestMode::SameOrigin) => {
                            (Some(response_from_cache.response), false)
                        },
                        (CacheMode::OnlyIfCached, _) |
                        (CacheMode::NoStore, _) |
                        (CacheMode::Reload, _) => (None, false),
                        (_, _) => (
                            Some(response_from_cache.response),
                            response_from_cache.needs_validation,
                        ),
                    };

                if needs_revalidation {
                    *revalidating_flag = true;
                    // Substep 5
                    if let Some(http_date) = response_headers.typed_get::<LastModified>() {
                        let http_date: SystemTime = http_date.into();
                        http_request
                            .headers
                            .typed_insert(IfModifiedSince::from(http_date));
                    }
                    if let Some(entity_tag) = response_headers.get(header::ETAG) {
                        http_request
                            .headers
                            .insert(header::IF_NONE_MATCH, entity_tag.clone());
                    }
                } else {
                    // Substep 6
                    *response = cached_response;
                    if let Some(response) = response {
                        response.cache_state = CacheState::Local;
                    }
                }
                if response.is_none() {
                    // Ensure the done chan is not set if we're not using the cached response,
                    // as the cache might have set it to Some if it constructed a pending response.
                    *done_chan = None;
                }
            }
        },
    }
    guard_result
}

/// Wait for a cached response from channel.
/// Happens when a fetch gets a cache hit, and the resource is pending completion from the network.
async fn wait_for_inflight_requests(done_chan: &mut DoneChannel, response: &mut Option<Response>) {
    if let Some(ref mut ch) = *done_chan {
        // The cache constructed a response with a body of ResponseBody::Receiving.
        // We wait for the response in the cache to "finish",
        // with a body of either Done or Cancelled.
        assert!(response.is_some());

        loop {
            match ch.1.recv().await {
                Some(Data::Payload(_)) => {},
                Some(Data::Done) => break, // Return the full response as if it was initially cached as such.
                Some(Data::Cancelled) => {
                    // The response was cancelled while the fetch was ongoing.
                    break;
                },
                _ => panic!("HTTP cache should always send Done or Cancelled"),
            }
        }
    }
    // Set done_chan back to None, it's cache-related usefulness ends here.
    *done_chan = None;
}

/// <https://fetch.spec.whatwg.org/#cross-origin-resource-policy-check>
///
/// This is obtained from [cross_origin_resource_policy_check]
#[derive(PartialEq)]
enum CrossOriginResourcePolicy {
    Allowed,
    Blocked,
}

enum ForNavigation {
    #[expect(dead_code)]
    Yes,
    No,
}

/// <https://fetch.spec.whatwg.org/#cross-origin-resource-policy-check>
fn cross_origin_resource_policy_check(
    origin: &Origin,
    request_client: &RequestClient,
    response: &Response,
    for_navigation: ForNavigation,
) -> CrossOriginResourcePolicy {
    // Step 1. Set forNavigation to false if it is not given.
    //
    // That's the default value of the enum

    // Step 2. Let embedderPolicy be settingsObject’s policy container’s embedder policy.
    let RequestPolicyContainer::PolicyContainer(ref policy_container) =
        request_client.policy_container
    else {
        return CrossOriginResourcePolicy::Blocked;
    };

    let embedder_policy = &policy_container.embedder_policy;

    // Step 3. If the cross-origin resource policy internal check with origin, "unsafe-none",
    // response, and forNavigation returns blocked, then return blocked.
    if cross_origin_resource_policy_internal_check(
        origin,
        EmbedderPolicyValue::UnsafeNone,
        response,
        &for_navigation,
    ) == CrossOriginResourcePolicy::Blocked
    {
        return CrossOriginResourcePolicy::Blocked;
    }

    // TODO Step 4. If the cross-origin resource policy internal check with origin,
    // embedderPolicy’s report only value, response, and forNavigation returns blocked, then queue
    // a cross-origin embedder policy CORP violation report with response, settingsObject,
    // destination, and true.

    // Step 5. If the cross-origin resource policy internal check with origin, embedderPolicy’s
    // value, response, and forNavigation returns allowed, then return allowed.
    if cross_origin_resource_policy_internal_check(
        origin,
        embedder_policy.value,
        response,
        &for_navigation,
    ) == CrossOriginResourcePolicy::Allowed
    {
        return CrossOriginResourcePolicy::Allowed;
    }

    // TODO Step 6. Queue a cross-origin embedder policy CORP violation report with response,
    // settingsObject, destination, and false.

    // Step 7. Return blocked.
    CrossOriginResourcePolicy::Blocked
}

/// <https://fetch.spec.whatwg.org/#cross-origin-resource-policy-internal-check>
fn cross_origin_resource_policy_internal_check(
    origin: &Origin,
    embedder_policy_value: EmbedderPolicyValue,
    response: &Response,
    for_navigation: &ForNavigation,
) -> CrossOriginResourcePolicy {
    // Step 1. If forNavigation is true and embedderPolicyValue is "unsafe-none", then return allowed.
    if let ForNavigation::Yes = for_navigation &&
        let EmbedderPolicyValue::UnsafeNone = embedder_policy_value
    {
        return CrossOriginResourcePolicy::Allowed;
    }

    // Step 2. Let policy be the result of getting `Cross-Origin-Resource-Policy` from response’s header list.
    let policy = response
        .headers
        .get(HeaderName::from_static("cross-origin-resource-policy"))
        .and_then(|h| h.to_str().ok());

    // Step 3. If policy is neither `same-origin`, `same-site`, nor `cross-origin`, then set policy to null.
    let policy = policy
        .filter(|&s| s == "same-origin" || s == "same-site" || s == "cross-origin")
        // Step 4. If policy is null, then switch on embedderPolicyValue:
        .or(match embedder_policy_value {
            // Do nothing.
            EmbedderPolicyValue::UnsafeNone => None,
            // Set policy to `same-origin`.
            EmbedderPolicyValue::RequireCorp => Some("same-origin"),
        });

    // Step 5. Switch on policy:
    match policy {
        Some("same-origin") => {
            // If origin is same origin with response’s URL’s origin, then return allowed.
            if let Origin::Origin(request_origin) = origin &&
                response
                    .url()
                    .is_some_and(|url| request_origin == &url.origin())
            {
                return CrossOriginResourcePolicy::Allowed;
            }

            // Otherwise, return blocked.
            CrossOriginResourcePolicy::Blocked
        },
        Some("same-site") => {
            if let Some(response_url) = response.url() {
                // If all of the following are true
                // origin is schemelessly same site with response’s URL’s origin
                // origin’s scheme is "https" or response’s URL’s scheme is not "https"
                if let Origin::Origin(request_origin) = origin &&
                    is_schemelessy_same_site(request_origin, &response_url.origin()) &&
                    (request_origin.scheme() == Some("https") ||
                        response_url.scheme() != "https")
                {
                    return CrossOriginResourcePolicy::Allowed;
                }
            }
            // Otherwise, return blocked.
            CrossOriginResourcePolicy::Blocked
        },
        // null / 'cross-origin'
        // Return allowed.
        _ => CrossOriginResourcePolicy::Allowed,
    }
}

// Convenience struct that implements Done, for setting responseEnd on function return
struct ResponseEndTimer(Option<ResourceFetchTimingContainer>);

impl ResponseEndTimer {
    fn neuter(&mut self) {
        self.0 = None;
    }
}

impl Drop for ResponseEndTimer {
    fn drop(&mut self) {
        let ResponseEndTimer(resource_fetch_timing_opt) = self;

        resource_fetch_timing_opt.as_ref().map_or((), |t| {
            t.set_attribute(ResourceAttribute::ResponseEnd);
        })
    }
}

/// [HTTP network fetch](https://fetch.spec.whatwg.org/#http-network-fetch)
#[servo_tracing::instrument(skip_all,fields(url=fetch_params.request.url().as_str()))]
async fn http_network_fetch(
    fetch_params: &mut FetchParams,
    credentials_flag: bool,
    done_chan: &mut DoneChannel,
    context: &FetchContext,
) -> Response {
    let mut response_end_timer = ResponseEndTimer(Some(context.timing.clone()));

    // Step 1: Let request be fetchParams’s request.
    let request = &mut fetch_params.request;

    // TODO Step 2. If request’s client is offline, then return a network error.

    // TODO Step 3. Let response be null.

    // TODO Step 4. Let timingInfo be fetchParams’s timing info.

    // TODO Step 5. Let networkPartitionKey be the result of determining the network partition key
    // given request.

    let url = request.current_url();
    let request_id = request.id.0.to_string();
    if log_enabled!(log::Level::Info) {
        info!("{:?} request for {}", request.method, url);
        for header in request.headers.iter() {
            debug!(" - {:?}", header);
        }
    }

    // XHR uses the default destination; other kinds of fetches (which haven't been implemented yet)
    // do not. Once we support other kinds of fetches we'll need to be more fine grained here
    // since things like image fetches are classified differently by devtools
    let is_xhr = request.destination == Destination::None;

    // The receiver will receive true if there has been an error streaming the request body.
    let (fetch_terminated_sender, mut fetch_terminated_receiver) = unbounded_channel();

    let body = request.body.as_ref().map(|body| body.clone_stream());

    if body.is_none() {
        // There cannot be an error streaming a non-existent body.
        // However in such a case the channel will remain unused
        // and drop inside `obtain_response`.
        // Send the confirmation now, ensuring the receiver will not dis-connect first.
        let _ = fetch_terminated_sender.send(false);
    }

    let browsing_context_id = request.target_webview_id.map(Into::into);

    // Step 6. Let newConnection be "yes" if forceNewConnection is true; otherwise "no".

    // Step 7. Switch on request’s mode:
    let (res, msg) = match &request.mode {
        // Let connection be the result of obtaining a WebSocket connection, given request’s current URL.
        RequestMode::WebSocket {
            protocols,
            original_url: _,
        } => {
            // https://fetch.spec.whatwg.org/#websocket-opening-handshake

            let (resource_event_sender, dom_action_receiver) = {
                let mut websocket_chan = context.websocket_chan.as_ref().unwrap().lock();
                (
                    websocket_chan.sender.clone(),
                    websocket_chan.receiver.take().unwrap(),
                )
            };

            let mut tls_config = create_tls_config(
                context.ca_certificates.clone(),
                context.ignore_certificate_errors,
                context.state.override_manager.clone(),
            );
            tls_config.alpn_protocols = vec!["http/1.1".to_string().into()];

            let response = match start_websocket(
                context.state.clone(),
                resource_event_sender,
                protocols,
                request,
                tls_config,
                dom_action_receiver,
            )
            .await
            {
                Ok(response) => response,
                Err(error) => {
                    return Response::network_error(NetworkError::WebsocketConnectionFailure(
                        format!("{error:?}"),
                    ));
                },
            };

            let response = response.map(|r| match r {
                Some(body) => Full::from(body).map_err(|_| unreachable!()).boxed(),
                None => http_body_util::Empty::new()
                    .map_err(|_| unreachable!())
                    .boxed(),
            });
            (Decoder::detect(response, url.is_secure_scheme()), None)
        },
        // Let connection be the result of obtaining a connection, given networkPartitionKey,
        // request’s current URL, includeCredentials, and newConnection.
        _ => {
            let response_future = obtain_response(
                &context.state.client,
                &url,
                &request.method,
                &mut request.headers,
                body,
                request
                    .body
                    .as_ref()
                    .is_some_and(|body| body.source_is_null()),
                &request.pipeline_id,
                Some(&request_id),
                request.destination,
                is_xhr,
                context,
                fetch_terminated_sender,
                browsing_context_id,
            );

            // This will only get the headers, the body is read later
            let (res, msg) = match response_future.await {
                Ok(wrapped_response) => wrapped_response,
                Err(error) => return Response::network_error(error),
            };
            (res, msg)
        },
    };

    if log_enabled!(log::Level::Info) {
        debug!("{:?} response for {}", res.version(), url);
        for header in res.headers().iter() {
            debug!(" - {:?}", header);
        }
    }

    // Check if there was an error while streaming the request body.
    //
    match fetch_terminated_receiver.recv().await {
        Some(true) => return Response::network_error(NetworkError::ConnectionFailure),
        Some(false) => {},
        _ => warn!("Failed to receive confirmation request was streamed without error."),
    }

    let timing = context.timing.inner().clone();
    let mut response = Response::new(url.clone(), timing);

    if let Some(handshake_info) = res.extensions().get::<TlsHandshakeInfo>() {
        let mut hsts_enabled = url
            .host_str()
            .is_some_and(|host| context.state.hsts_list.read().is_host_secure(host));

        if url.scheme() == "https" &&
            let Some(sts) = res.headers().typed_get::<StrictTransportSecurity>()
        {
            // max-age > 0 enables HSTS, max-age = 0 disables it (RFC 6797 Section 6.1.1)
            hsts_enabled = sts.max_age().as_secs() > 0;
        }
        response.tls_security_info = Some(build_tls_security_info(handshake_info, hsts_enabled));
    }

    let status_text = res
        .extensions()
        .get::<ReasonPhrase>()
        .map(ReasonPhrase::as_bytes)
        .or_else(|| res.status().canonical_reason().map(str::as_bytes))
        .map(Vec::from)
        .unwrap_or_default();
    response.status = HttpStatus::new(res.status(), status_text);

    info!("got {:?} response for {:?}", res.status(), request.url());
    response.headers = res.headers().clone();
    response.referrer = request.referrer.to_url().cloned();
    response.referrer_policy = request.referrer_policy;

    let res_body = response.body.clone();

    // We're about to spawn a future to be waited on here
    let (done_sender, done_receiver) = unbounded_channel();
    *done_chan = Some((done_sender.clone(), done_receiver));

    let devtools_sender = context.devtools_chan.clone();
    let cancellation_listener = context.cancellation_listener.clone();
    if cancellation_listener.cancelled() {
        return Response::network_error(NetworkError::LoadCancelled);
    }

    *res_body.lock() = ResponseBody::Receiving(vec![]);
    let res_body2 = res_body.clone();

    if let Some(ref sender) = devtools_sender &&
        let Some(m) = msg
    {
        send_request_to_devtools(m, sender);
    }

    let done_sender2 = done_sender.clone();
    let done_sender3 = done_sender.clone();
    let timing_ptr2 = context.timing.clone();
    let timing_ptr3 = context.timing.clone();
    let devtools_request = request.clone();
    let url1 = devtools_request.url();
    let url2 = url1.clone();

    let status = response.status.clone();
    let headers = response.headers.clone();
    let devtools_chan = context.devtools_chan.clone();

    spawn_task(
        res.into_body()
            .try_fold(res_body, move |res_body, chunk| {
                if cancellation_listener.cancelled() {
                    *res_body.lock() = ResponseBody::Done(vec![]);
                    let _ = done_sender.send(Data::Cancelled);
                    return future::ready(Err(std::io::Error::new(
                        std::io::ErrorKind::Interrupted,
                        "Fetch aborted",
                    )));
                }
                if let ResponseBody::Receiving(ref mut body) = *res_body.lock() {
                    let bytes = chunk;
                    body.extend_from_slice(&bytes);
                    let _ = done_sender.send(Data::Payload(bytes.to_vec()));
                }
                future::ready(Ok(res_body))
            })
            .and_then(move |res_body| {
                debug!("successfully finished response for {:?}", url1);
                let mut body = res_body.lock();
                let completed_body = match *body {
                    ResponseBody::Receiving(ref mut body) => std::mem::take(body),
                    _ => vec![],
                };
                let devtools_response_body = completed_body.clone();
                *body = ResponseBody::Done(completed_body);
                send_response_values_to_devtools(
                    Some(headers),
                    status,
                    Some(devtools_response_body),
                    CacheState::None,
                    &devtools_request,
                    devtools_chan,
                );
                timing_ptr2.set_attribute(ResourceAttribute::ResponseEnd);
                let _ = done_sender2.send(Data::Done);
                future::ready(Ok(()))
            })
            .map_err(move |error| {
                if let std::io::ErrorKind::InvalidData = error.kind() {
                    debug!("Content decompression error for {:?}", url2);
                    let _ = done_sender3.send(Data::Error(NetworkError::DecompressionError));
                    let mut body = res_body2.lock();

                    *body = ResponseBody::Done(vec![]);
                }
                debug!("finished response for {:?}", url2);
                let mut body = res_body2.lock();
                let completed_body = match *body {
                    ResponseBody::Receiving(ref mut body) => std::mem::take(body),
                    _ => vec![],
                };
                *body = ResponseBody::Done(completed_body);
                timing_ptr3.set_attribute(ResourceAttribute::ResponseEnd);
                let _ = done_sender3.send(Data::Done);
            }),
    );

    // TODO these substeps aren't possible yet
    // Substep 1

    // Substep 2

    // TODO Read request

    // Step 6-11
    // (needs stream bodies)

    // Step 13
    // TODO this step isn't possible yet (CSP)

    // Step 14, update the cached response, done via the shared response body.

    // TODO this step isn't possible yet
    // Step 15
    if credentials_flag {
        set_cookies_from_headers(&url, &response.headers, &context.state.cookie_jar);
    }
    context
        .state
        .hsts_list
        .write()
        .update_hsts_list_from_response(&url, &response.headers);

    // TODO these steps
    // Step 16
    // Substep 1
    // Substep 2
    // Sub-substep 1
    // Sub-substep 2
    // Sub-substep 3
    // Sub-substep 4
    // Substep 3

    // Step 16

    // Ensure we don't override "responseEnd" on successful return of this function
    response_end_timer.neuter();
    response
}

/// [CORS preflight fetch](https://fetch.spec.whatwg.org#cors-preflight-fetch)
async fn cors_preflight_fetch(
    request: &Request,
    cache: &mut CorsCache,
    context: &FetchContext,
) -> Response {
    // Step 1. Let preflight be a new request whose method is `OPTIONS`, URL list is a clone
    // of request’s URL list, initiator is request’s initiator, destination is request’s destination,
    // origin is request’s origin, referrer is request’s referrer, referrer policy is request’s
    // referrer policy, mode is "cors", and response tainting is "cors".
    let mut preflight = RequestBuilder::new(
        request.target_webview_id,
        request.current_url_with_blob_claim(),
        request.referrer.clone(),
    )
    .method(Method::OPTIONS)
    .origin(match &request.origin {
        Origin::Client => {
            unreachable!("We shouldn't get Client origin in cors_preflight_fetch.")
        },
        Origin::Origin(origin) => origin.clone(),
    })
    .pipeline_id(request.pipeline_id)
    .initiator(request.initiator)
    .destination(request.destination)
    .referrer_policy(request.referrer_policy)
    .mode(RequestMode::CorsMode)
    .response_tainting(ResponseTainting::CorsTainting)
    .policy_container(match &request.policy_container {
        RequestPolicyContainer::Client => {
            unreachable!("We should have a policy container for request in cors_preflight_fetch")
        },
        RequestPolicyContainer::PolicyContainer(policy_container) => policy_container.clone(),
    })
    .url_list(
        request
            .url_list
            .iter()
            .map(|claimed_url| claimed_url.url())
            .collect(),
    )
    .build();

    // Step 2. Append (`Accept`, `*/*`) to preflight’s header list.
    preflight
        .headers
        .insert(ACCEPT, HeaderValue::from_static("*/*"));

    // Step 3. Append (`Access-Control-Request-Method`, request’s method) to preflight’s header list.
    preflight
        .headers
        .typed_insert::<AccessControlRequestMethod>(AccessControlRequestMethod::from(
            request.method.clone(),
        ));

    // Step 4. Let headers be the CORS-unsafe request-header names with request’s header list.
    let headers = get_cors_unsafe_header_names(&request.headers);

    // Step 5 If headers is not empty, then:
    if !headers.is_empty() {
        // 5.1 Let value be the items in headers separated from each other by `,`
        // TODO(36451): replace this with typed_insert when headers fixes headers#207
        preflight.headers.insert(
            ACCESS_CONTROL_REQUEST_HEADERS,
            HeaderValue::from_bytes(itertools::join(headers.iter(), ",").as_bytes())
                .unwrap_or(HeaderValue::from_static("")),
        );
    }

    // Step 6. Let response be the result of running HTTP-network-or-cache fetch given a
    // new fetch params whose request is preflight.
    let mut fetch_params = FetchParams::new(preflight);
    let response =
        http_network_or_cache_fetch(&mut fetch_params, false, false, &mut None, context).await;

    // Step 7. If a CORS check for request and response returns success and response’s status is an ok status, then:
    if cors_check(request, &response).is_ok() && response.status.code().is_success() {
        // Step 7.1 Let methods be the result of extracting header list values given
        // `Access-Control-Allow-Methods` and response’s header list.
        let mut methods = if response
            .headers
            .contains_key(header::ACCESS_CONTROL_ALLOW_METHODS)
        {
            match response.headers.typed_get::<AccessControlAllowMethods>() {
                Some(methods) => methods.iter().collect(),
                // Step 7.3 If either methods or headerNames is failure, return a network error.
                None => {
                    return Response::network_error(NetworkError::CorsAllowMethods);
                },
            }
        } else {
            vec![]
        };

        // Step 7.2 Let headerNames be the result of extracting header list values given
        // `Access-Control-Allow-Headers` and response’s header list.
        let header_names = if response
            .headers
            .contains_key(header::ACCESS_CONTROL_ALLOW_HEADERS)
        {
            match response.headers.typed_get::<AccessControlAllowHeaders>() {
                Some(names) => names.iter().collect(),
                // Step 7.3 If either methods or headerNames is failure, return a network error.
                None => {
                    return Response::network_error(NetworkError::CorsAllowHeaders);
                },
            }
        } else {
            vec![]
        };

        debug!(
            "CORS check: Allowed methods: {:?}, current method: {:?}",
            methods, request.method
        );

        // Step 7.4 If methods is null and request’s use-CORS-preflight flag is set,
        // then set methods to a new list containing request’s method.
        if methods.is_empty() && request.use_cors_preflight {
            methods = vec![request.method.clone()];
        }

        // Step 7.5 If request’s method is not in methods, request’s method is not a CORS-safelisted method,
        // and request’s credentials mode is "include" or methods does not contain `*`, then return a network error.
        if methods
            .iter()
            .all(|method| *method.as_str() != *request.method.as_ref()) &&
            !is_cors_safelisted_method(&request.method) &&
            (request.credentials_mode == CredentialsMode::Include ||
                methods.iter().all(|method| method.as_ref() != "*"))
        {
            return Response::network_error(NetworkError::CorsMethod);
        }

        debug!(
            "CORS check: Allowed headers: {:?}, current headers: {:?}",
            header_names, request.headers
        );

        // Step 7.6 If one of request’s header list’s names is a CORS non-wildcard request-header name
        // and is not a byte-case-insensitive match for an item in headerNames, then return a network error.
        if request.headers.iter().any(|(name, _)| {
            is_cors_non_wildcard_request_header_name(name) &&
                header_names.iter().all(|header_name| header_name != name)
        }) {
            return Response::network_error(NetworkError::CorsAuthorization);
        }

        // Step 7.7 For each unsafeName of the CORS-unsafe request-header names with request’s header list,
        // if unsafeName is not a byte-case-insensitive match for an item in headerNames and request’s credentials
        // mode is "include" or headerNames does not contain `*`, return a network error.
        let unsafe_names = get_cors_unsafe_header_names(&request.headers);
        let header_names_set: HashSet<&HeaderName> = HashSet::from_iter(header_names.iter());
        let header_names_contains_star = header_names
            .iter()
            .any(|header_name| header_name.as_str() == "*");
        for unsafe_name in unsafe_names.iter() {
            if !header_names_set.contains(unsafe_name) &&
                (request.credentials_mode == CredentialsMode::Include ||
                    !header_names_contains_star)
            {
                return Response::network_error(NetworkError::CorsHeaders);
            }
        }

        // Step 7.8 Let max-age be the result of extracting header list values given
        // `Access-Control-Max-Age` and response’s header list.
        let max_age: Option<Duration> = response
            .headers
            .typed_get::<AccessControlMaxAge>()
            .map(|acma| acma.into());

        // Step 7.9 If max-age is failure or null, then set max-age to 5.
        let max_age = max_age.unwrap_or(Duration::from_secs(5));

        // Step 7.10 If max-age is greater than an imposed limit on max-age, then set max-age to the imposed limit.
        // TODO: Need to define what an imposed limit on max-age is

        // Step 7.11 If the user agent does not provide for a cache, then return response.
        // NOTE: This can be ignored, we do have a CORS cache

        // Step 7.12 For each method in methods for which there is a method cache entry match using request,
        // set matching entry’s max-age to max-age.
        // Step 7.13 For each method in methods for which there is no method cache entry match using request,
        // create a new cache entry with request, max-age, method, and null.
        for method in &methods {
            cache.match_method_and_update(request, method.clone(), max_age);
        }

        // Step 7.14 For each headerName in headerNames for which there is a header-name cache entry match using request,
        // set matching entry’s max-age to max-age.
        // Step 7.15 For each headerName in headerNames for which there is no header-name cache entry match using request,
        // create a new cache entry with request, max-age, null, and headerName.
        for header_name in &header_names {
            cache.match_header_and_update(request, header_name, max_age);
        }

        // Step 7.16 Return response.
        return response;
    }

    // Step 8 Return a network error.
    Response::network_error(NetworkError::CorsGeneral)
}

/// [CORS check](https://fetch.spec.whatwg.org#concept-cors-check)
fn cors_check(request: &Request, response: &Response) -> Result<(), ()> {
    // Step 1. Let origin be the result of getting `Access-Control-Allow-Origin` from response’s header list.
    let Some(origins) =
        get_value_from_header_list(ACCESS_CONTROL_ALLOW_ORIGIN.as_str(), &response.headers)
    else {
        // Step 2. If origin is null, then return failure.
        return Err(());
    };
    let origin = origins.into_iter().map(char::from).collect::<String>();

    // Step 3. If request’s credentials mode is not "include" and origin is `*`, then return success.
    if request.credentials_mode != CredentialsMode::Include && origin == "*" {
        return Ok(());
    }

    // Step 4. If the result of byte-serializing a request origin with request is not origin, then return failure.
    if serialize_request_origin(request).to_string() != origin {
        return Err(());
    }

    // Step 5. If request’s credentials mode is not "include", then return success.
    if request.credentials_mode != CredentialsMode::Include {
        return Ok(());
    }

    // Step 6. Let credentials be the result of getting `Access-Control-Allow-Credentials` from response’s header list.
    let credentials = response
        .headers
        .typed_get::<AccessControlAllowCredentials>();

    // Step 7. If credentials is `true`, then return success.
    if credentials.is_some() {
        return Ok(());
    }

    // Step 8. Return failure.
    Err(())
}

fn has_credentials(url: &ServoUrl) -> bool {
    !url.username().is_empty() || url.password().is_some()
}

fn is_no_store_cache(headers: &HeaderMap) -> bool {
    headers.contains_key(header::IF_MODIFIED_SINCE) |
        headers.contains_key(header::IF_NONE_MATCH) |
        headers.contains_key(header::IF_UNMODIFIED_SINCE) |
        headers.contains_key(header::IF_MATCH) |
        headers.contains_key(header::IF_RANGE)
}

/// <https://fetch.spec.whatwg.org/#redirect-status>
fn is_redirect_status(status: StatusCode) -> bool {
    matches!(
        status,
        StatusCode::MOVED_PERMANENTLY |
            StatusCode::FOUND |
            StatusCode::SEE_OTHER |
            StatusCode::TEMPORARY_REDIRECT |
            StatusCode::PERMANENT_REDIRECT
    )
}

/// <https://fetch.spec.whatwg.org/#serializing-a-request-origin>
fn serialize_request_origin(request: &Request) -> headers::Origin {
    // Step 1. Assert: request’s origin is not "client".
    let Origin::Origin(origin) = &request.origin else {
        panic!("origin cannot be \"client\" at this point in time");
    };

    // Step 2. If request’s redirect-taint is not "same-origin", then return "null".
    if request.redirect_taint_for_request() != RedirectTaint::SameOrigin {
        return headers::Origin::NULL;
    }

    // Step 3. Return request’s origin, serialized.
    serialize_origin(origin)
}

/// Step 3 of <https://fetch.spec.whatwg.org/#serializing-a-request-origin>.
pub fn serialize_origin(origin: &ImmutableOrigin) -> headers::Origin {
    match origin {
        ImmutableOrigin::Opaque(_) => headers::Origin::NULL,
        ImmutableOrigin::Tuple(scheme, host, port) => {
            // Note: This must be kept in sync with `Origin::ascii_serialization()`, which does not
            // use the port number when a default port is used.
            let port = match (scheme.as_ref(), port) {
                ("http" | "ws", 80) | ("https" | "wss", 443) | ("ftp", 21) => None,
                _ => Some(*port),
            };

            // TODO: Ensure that hyper/servo don't disagree about valid origin headers
            headers::Origin::try_from_parts(scheme, &host.to_string(), port)
                .unwrap_or(headers::Origin::NULL)
        },
    }
}

/// <https://fetch.spec.whatwg.org/#append-a-request-origin-header>
#[expect(
    clippy::collapsible_match,
    reason = "The current way follows the spec more closely"
)]
fn append_a_request_origin_header(request: &mut Request) {
    // Step 1. Assert: request’s origin is not "client".
    let Origin::Origin(request_origin) = &request.origin else {
        panic!("origin cannot be \"client\" at this point in time");
    };

    // Step 2. Let serializedOrigin be the result of byte-serializing a request origin with request.
    let mut serialized_origin = serialize_request_origin(request);

    // Step 3. If request’s response tainting is "cors" or request’s mode is "websocket",
    //         then append (`Origin`, serializedOrigin) to request’s header list.
    if request.response_tainting == ResponseTainting::CorsTainting ||
        matches!(request.mode, RequestMode::WebSocket { .. })
    {
        request.headers.typed_insert(serialized_origin);
    }
    // Step 4. Otherwise, if request’s method is neither `GET` nor `HEAD`, then:
    else if !matches!(request.method, Method::GET | Method::HEAD) {
        // Step 4.1 If request’s mode is not "cors", then switch on request’s referrer policy:
        if request.mode != RequestMode::CorsMode {
            match request.referrer_policy {
                ReferrerPolicy::NoReferrer => {
                    // Set serializedOrigin to `null`.
                    serialized_origin = headers::Origin::NULL;
                },
                ReferrerPolicy::NoReferrerWhenDowngrade |
                ReferrerPolicy::StrictOrigin |
                ReferrerPolicy::StrictOriginWhenCrossOrigin => {
                    // If request’s origin is a tuple origin, its scheme is "https", and
                    // request’s current URL’s scheme is not "https", then set serializedOrigin to `null`.
                    if let ImmutableOrigin::Tuple(scheme, _, _) = &request_origin &&
                        scheme == "https" &&
                        request.current_url().scheme() != "https"
                    {
                        serialized_origin = headers::Origin::NULL;
                    }
                },
                ReferrerPolicy::SameOrigin => {
                    // If request’s origin is not same origin with request’s current URL’s origin,
                    // then set serializedOrigin to `null`.
                    if *request_origin != request.current_url().origin() {
                        serialized_origin = headers::Origin::NULL;
                    }
                },
                _ => {
                    // Otherwise, do nothing.
                },
            };
        }

        // Step 4.2. Append (`Origin`, serializedOrigin) to request’s header list.
        request.headers.typed_insert(serialized_origin);
    }
}

/// <https://w3c.github.io/webappsec-fetch-metadata/#abstract-opdef-append-the-fetch-metadata-headers-for-a-request>
fn append_the_fetch_metadata_headers(r: &mut Request) {
    // Step 1. If r’s url is not an potentially trustworthy URL, return.
    if !r.url().is_potentially_trustworthy() {
        return;
    }

    // Step 2. Set the Sec-Fetch-Dest header for r.
    set_the_sec_fetch_dest_header(r);

    // Step 3. Set the Sec-Fetch-Mode header for r.
    set_the_sec_fetch_mode_header(r);

    // Step 4. Set the Sec-Fetch-Site header for r.
    set_the_sec_fetch_site_header(r);

    // Step 5. Set the Sec-Fetch-User header for r.
    set_the_sec_fetch_user_header(r);
}

/// Steps 8.16 to 8.18 in [HTTP network or cache fetch](https://fetch.spec.whatwg.org/#concept-http-network-or-cache-fetch)
fn append_cache_data_to_headers(http_request: &mut Request) {
    match http_request.cache_mode {
        // Step 8.16: If httpRequest’s cache mode is "default" and httpRequest’s header list
        // contains `If-Modified-Since`, `If-None-Match`, `If-Unmodified-Since`, `If-Match`, or
        // `If-Range`, then set httpRequest’s cache mode to "no-store".
        CacheMode::Default if is_no_store_cache(&http_request.headers) => {
            http_request.cache_mode = CacheMode::NoStore;
        },

        // Note that the following steps (8.17 and 8.18) are being considered for removal:
        // https://github.com/whatwg/fetch/issues/722#issuecomment-1420264615

        // Step 8.17: If httpRequest’s cache mode is "no-cache", httpRequest’s prevent no-cache
        // cache-control header modification flag is unset, and httpRequest’s header list does not
        // contain `Cache-Control`, then append (`Cache-Control`, `max-age=0`) to httpRequest’s
        // header list.
        // TODO: Implement request's prevent no-cache cache-control header modification flag
        // https://fetch.spec.whatwg.org/#no-cache-prevent-cache-control
        CacheMode::NoCache if !http_request.headers.contains_key(header::CACHE_CONTROL) => {
            http_request
                .headers
                .typed_insert(CacheControl::new().with_max_age(Duration::from_secs(0)));
        },

        // Step 8.18: If httpRequest’s cache mode is "no-store" or "reload", then:
        CacheMode::Reload | CacheMode::NoStore => {
            // Step 8.18.1: If httpRequest’s header list does not contain `Pragma`, then append
            // (`Pragma`, `no-cache`) to httpRequest’s header list.
            if !http_request.headers.contains_key(header::PRAGMA) {
                http_request.headers.typed_insert(Pragma::no_cache());
            }

            // Step 8.18.2: If httpRequest’s header list does not contain `Cache-Control`, then
            // append (`Cache-Control`, `no-cache`) to httpRequest’s header list.
            if !http_request.headers.contains_key(header::CACHE_CONTROL) {
                http_request
                    .headers
                    .typed_insert(CacheControl::new().with_no_cache());
            }
        },

        _ => {},
    }
}

/// <https://w3c.github.io/webappsec-fetch-metadata/#abstract-opdef-set-dest>
fn set_the_sec_fetch_dest_header(r: &mut Request) {
    // Step 1. Assert: r’s url is a potentially trustworthy URL.
    debug_assert!(r.url().is_potentially_trustworthy());

    // Step 2. Let header be a Structured Header whose value is a token.
    // Step 3. If r’s destination is the empty string, set header’s value to the string "empty".
    // Otherwise, set header’s value to r’s destination.
    let header = r.destination;

    // Step 4. Set a structured field value `Sec-Fetch-Dest`/header in r’s header list.
    r.headers.typed_insert(SecFetchDest(header));
}

/// <https://w3c.github.io/webappsec-fetch-metadata/#abstract-opdef-set-mode>
fn set_the_sec_fetch_mode_header(r: &mut Request) {
    // Step 1. Assert: r’s url is a potentially trustworthy URL.
    debug_assert!(r.url().is_potentially_trustworthy());

    // Step 2. Let header be a Structured Header whose value is a token.
    // Step 3. Set header’s value to r’s mode.
    let header = &r.mode;

    // Step 4. Set a structured field value `Sec-Fetch-Mode`/header in r’s header list.
    r.headers.typed_insert(SecFetchMode::from(header));
}

/// <https://w3c.github.io/webappsec-fetch-metadata/#abstract-opdef-set-site>
fn set_the_sec_fetch_site_header(r: &mut Request) {
    // The webappsec spec seems to have a similar issue as
    // https://github.com/whatwg/fetch/issues/1773
    let Origin::Origin(request_origin) = &r.origin else {
        panic!("request origin cannot be \"client\" at this point")
    };

    // Step 1. Assert: r’s url is a potentially trustworthy URL.
    debug_assert!(r.url().is_potentially_trustworthy());

    // Step 2. Let header be a Structured Header whose value is a token.
    // Step 3. Set header’s value to same-origin.
    let mut header = SecFetchSite::SameOrigin;

    // TODO: Step 3. If r is a navigation request that was explicitly caused by a
    // user’s interaction with the user agent, then set header’s value to none.

    // Step 5. If header’s value is not none, then for each url in r’s url list:
    if header != SecFetchSite::None {
        for url in &r.url_list {
            // Step 5.1 If url is same origin with r’s origin, continue.
            if url.origin() == *request_origin {
                continue;
            }

            // Step 5.2 Set header’s value to cross-site.
            header = SecFetchSite::CrossSite;

            // Step 5.3 If r’s origin is not same site with url’s origin, then break.
            if !is_same_site(request_origin, &url.origin()) {
                break;
            }

            // Step 5.4 Set header’s value to same-site.
            header = SecFetchSite::SameSite;
        }
    }

    // Step 6. Set a structured field value `Sec-Fetch-Site`/header in r’s header list.
    r.headers.typed_insert(header);
}

/// <https://w3c.github.io/webappsec-fetch-metadata/#abstract-opdef-set-user>
fn set_the_sec_fetch_user_header(r: &mut Request) {
    // Step 1. Assert: r’s url is a potentially trustworthy URL.
    debug_assert!(r.url().is_potentially_trustworthy());

    // Step 2. If r is not a navigation request, or if r’s user-activation is false, return.
    // TODO user activation
    if !r.is_navigation_request() {
        return;
    }

    // Step 3. Let header be a Structured Header whose value is a token.
    // Step 4. Set header’s value to true.
    let header = SecFetchUser;

    // Step 5. Set a structured field value `Sec-Fetch-User`/header in r’s header list.
    r.headers.typed_insert(header);
}

/// <https://w3c.github.io/webappsec-referrer-policy/#set-requests-referrer-policy-on-redirect>
fn set_requests_referrer_policy_on_redirect(request: &mut Request, response: &Response) {
    // Step 1: Let policy be the result of executing § 8.1 Parse a referrer policy from a
    // Referrer-Policy header on actualResponse.
    let referrer_policy: ReferrerPolicy = response
        .headers
        .typed_get::<headers::ReferrerPolicy>()
        .into();

    // Step 2: If policy is not the empty string, then set request’s referrer policy to policy.
    if referrer_policy != ReferrerPolicy::EmptyString {
        request.referrer_policy = referrer_policy;
    }
}