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reverse proxy: use http.Protocols to handle h2c requests #6990

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reverse proxy: use http.Protocols to handle h2c requests #6990

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49 changes: 15 additions & 34 deletions modules/caddyhttp/reverseproxy/httptransport.go
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Original file line number Diff line number Diff line change
Expand Up @@ -159,8 +159,7 @@ type HTTPTransport struct {
// `HTTPS_PROXY`, and `NO_PROXY` environment variables.
NetworkProxyRaw json.RawMessage `json:"network_proxy,omitempty" caddy:"namespace=caddy.network_proxy inline_key=from"`

h2cTransport *http2.Transport
h3Transport *http3.Transport // TODO: EXPERIMENTAL (May 2024)
h3Transport *http3.Transport // TODO: EXPERIMENTAL (May 2024)
}

// CaddyModule returns the Caddy module information.
Expand Down Expand Up @@ -436,12 +435,6 @@ func (h *HTTPTransport) NewTransport(caddyCtx caddy.Context) (*http.Transport, e
rt.DisableCompression = !*h.Compression
}

if slices.Contains(h.Versions, "2") {
if err := http2.ConfigureTransport(rt); err != nil {
return nil, err
}
}

// configure HTTP/3 transport if enabled; however, this does not
// automatically fall back to lower versions like most web browsers
// do (that'd add latency and complexity, besides, we expect that
Expand All @@ -459,25 +452,22 @@ func (h *HTTPTransport) NewTransport(caddyCtx caddy.Context) (*http.Transport, e
return nil, fmt.Errorf("if HTTP/3 is enabled to the upstream, no other HTTP versions are supported")
}

// if h2c is enabled, configure its transport (std lib http.Transport
// does not "HTTP/2 over cleartext TCP")
if slices.Contains(h.Versions, "h2c") {
// crafting our own http2.Transport doesn't allow us to utilize
// most of the customizations/preferences on the http.Transport,
// because, for some reason, only http2.ConfigureTransport()
// is allowed to set the unexported field that refers to a base
// http.Transport config; oh well
h2t := &http2.Transport{
// kind of a hack, but for plaintext/H2C requests, pretend to dial TLS
DialTLSContext: func(ctx context.Context, network, address string, _ *tls.Config) (net.Conn, error) {
return dialContext(ctx, network, address)
},
AllowHTTP: true,
// if h2/c is enabled, configure it explicitly
if slices.Contains(h.Versions, "2") || slices.Contains(h.Versions, "h2c") {
if err := http2.ConfigureTransport(rt); err != nil {
return nil, err
}
if h.Compression != nil {
h2t.DisableCompression = !*h.Compression

// DisableCompression from h2 is configured by http2.ConfigureTransport
// Likewise, DisableKeepAlives from h1 is used too.

// Protocols field is only used when the request is not using TLS,
// http1/2 over tls is still allowed
if slices.Contains(h.Versions, "h2c") {
rt.Protocols = new(http.Protocols)
rt.Protocols.SetUnencryptedHTTP2(true)
rt.Protocols.SetHTTP1(false)
}
h.h2cTransport = h2t
}

return rt, nil
Expand All @@ -492,15 +482,6 @@ func (h *HTTPTransport) RoundTrip(req *http.Request) (*http.Response, error) {
return h.h3Transport.RoundTrip(req)
}

// if H2C ("HTTP/2 over cleartext") is enabled and the upstream request is
// HTTP without TLS, use the alternate H2C-capable transport instead
if req.URL.Scheme == "http" && h.h2cTransport != nil {
// There is no dedicated DisableKeepAlives field in *http2.Transport.
// This is an alternative way to disable keep-alive.
req.Close = h.Transport.DisableKeepAlives
return h.h2cTransport.RoundTrip(req)
}

return h.Transport.RoundTrip(req)
}

Expand Down
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