httpserver: Add experimental H2C support (#3289)

* reverse_proxy: Initial attempt at H2C transport/client support (#3218)

I have not tested this yet

* Experimentally enabling H2C server support (closes #3227)

See also #3218

I have not tested this

* reverseproxy: Clean up H2C transport a bit

* caddyhttp: Update godoc for h2c server; clarify experimental status

* caddyhttp: Fix trailers when recording responses (fixes #3236)

* caddyhttp: Tweak h2c config settings and docs
This commit is contained in:
Matt Holt 2020-05-05 12:33:21 -06:00 committed by GitHub
parent 96d6d277a4
commit 41c7bd27b4
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 63 additions and 1 deletions

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@ -27,6 +27,8 @@ import (
"github.com/caddyserver/caddy/v2/modules/caddytls"
"github.com/lucas-clemente/quic-go/http3"
"go.uber.org/zap"
"golang.org/x/net/http2"
"golang.org/x/net/http2/h2c"
)
func init() {
@ -282,6 +284,14 @@ func (app *App) Start() error {
Handler: srv,
}
// enable h2c if configured
if srv.AllowH2C {
h2server := &http2.Server{
IdleTimeout: time.Duration(srv.IdleTimeout),
}
s.Handler = h2c.NewHandler(srv, h2server)
}
for _, lnAddr := range srv.Listen {
listenAddr, err := caddy.ParseNetworkAddress(lnAddr)
if err != nil {

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@ -584,6 +584,7 @@ func (h *Handler) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
// tls_trusted_ca_certs <cert_files...>
// keepalive [off|<duration>]
// keepalive_idle_conns <max_count>
// versions <versions...>
// }
//
func (h *HTTPTransport) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
@ -701,6 +702,12 @@ func (h *HTTPTransport) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
h.KeepAlive.MaxIdleConns = num
h.KeepAlive.MaxIdleConnsPerHost = num
case "versions":
h.Versions = d.RemainingArgs()
if len(h.Versions) == 0 {
return d.ArgErr()
}
default:
return d.Errf("unrecognized subdirective %s", d.Val())
}

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@ -82,11 +82,16 @@ type HTTPTransport struct {
// The size of the read buffer in bytes.
ReadBufferSize int `json:"read_buffer_size,omitempty"`
// The versions of HTTP to support. Default: ["1.1", "2"]
// The versions of HTTP to support. As a special case, "h2c"
// can be specified to use H2C (HTTP/2 over Cleartext) to the
// upstream (this feature is experimental and subject to
// change or removal). Default: ["1.1", "2"]
Versions []string `json:"versions,omitempty"`
// The pre-configured underlying HTTP transport.
Transport *http.Transport `json:"-"`
h2cTransport *http2.Transport
}
// CaddyModule returns the Caddy module information.
@ -110,6 +115,28 @@ func (h *HTTPTransport) Provision(ctx caddy.Context) error {
}
h.Transport = rt
// if h2c is enabled, configure its transport (std lib http.Transport
// does not "HTTP/2 over cleartext TCP")
if sliceContains(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
DialTLS: func(network, addr string, _ *tls.Config) (net.Conn, error) {
// TODO: no context, thus potentially wrong dial info
return net.Dial(network, addr)
},
AllowHTTP: true,
}
if h.Compression != nil {
h2t.DisableCompression = !*h.Compression
}
h.h2cTransport = h2t
}
return nil
}
@ -182,6 +209,13 @@ func (h *HTTPTransport) NewTransport(_ caddy.Context) (*http.Transport, error) {
// RoundTrip implements http.RoundTripper.
func (h *HTTPTransport) RoundTrip(req *http.Request) (*http.Response, error) {
h.SetScheme(req)
// if H2C ("HTTP/2 over cleartext") is enabled and the upstream request is
// HTTP/2 without TLS, use the alternate H2C-capable transport instead
if req.ProtoMajor == 2 && req.URL.Scheme == "http" && h.h2cTransport != nil {
return h.h2cTransport.RoundTrip(req)
}
return h.Transport.RoundTrip(req)
}

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@ -111,6 +111,17 @@ type Server struct {
// This field is not subject to compatibility promises.
ExperimentalHTTP3 bool `json:"experimental_http3,omitempty"`
// Enables H2C ("Cleartext HTTP/2" or "H2 over TCP") support,
// which will serve HTTP/2 over plaintext TCP connections if
// a client support it. Because this is not implemented by the
// Go standard library, using H2C is incompatible with most
// of the other options for this server. Do not enable this
// only to achieve maximum client compatibility. In practice,
// very few clients implement H2C, and even fewer require it.
// This setting applies only to unencrypted HTTP listeners.
// ⚠️ Experimental feature; subject to change or removal.
AllowH2C bool `json:"allow_h2c,omitempty"`
primaryHandlerChain Handler
errorHandlerChain Handler
listenerWrappers []caddy.ListenerWrapper