Enable full-duplex for HTTP/1.1

caddyconfig/httpcaddyfile/serveroptions.go

@@ -41,6 +41,7 @@ type serverOptions struct {
 	IdleTimeout          caddy.Duration
 	KeepAliveInterval    caddy.Duration
 	MaxHeaderBytes       int
+	EnableFullDuplex     bool
 	Protocols            []string
 	StrictSNIHost        *bool
 	TrustedProxiesRaw    json.RawMessage
@@ -157,6 +158,12 @@ func unmarshalCaddyfileServerOptions(d *caddyfile.Dispenser) (any, error) {
 				}
 				serverOpts.MaxHeaderBytes = int(size)
 
+			case "enable_full_duplex":
+				if d.NextArg() {
+					return nil, d.ArgErr()
+				}
+				serverOpts.EnableFullDuplex = true
+
 			case "log_credentials":
 				if d.NextArg() {
 					return nil, d.ArgErr()
@@ -327,6 +334,7 @@ func applyServerOptions(
 		server.IdleTimeout = opts.IdleTimeout
 		server.KeepAliveInterval = opts.KeepAliveInterval
 		server.MaxHeaderBytes = opts.MaxHeaderBytes
+		server.EnableFullDuplex = opts.EnableFullDuplex
 		server.Protocols = opts.Protocols
 		server.StrictSNIHost = opts.StrictSNIHost
 		server.TrustedProxiesRaw = opts.TrustedProxiesRaw

caddytest/integration/caddyfile_adapt/global_server_options_single.txt

@@ -11,6 +11,7 @@
 			idle 30s
 		}
 		max_header_size 100MB
+		enable_full_duplex
 		log_credentials
 		protocols h1 h2 h2c h3
 		strict_sni_host
@@ -45,6 +46,7 @@ foo.com {
 					"write_timeout": 30000000000,
 					"idle_timeout": 30000000000,
 					"max_header_bytes": 100000000,
+					"enable_full_duplex": true,
 					"routes": [
 						{
 							"match": [

modules/caddyhttp/duplex_go120.go

@@ -0,0 +1,25 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build !go1.21
+
+package caddyhttp
+
+import (
+	"net/http"
+)
+
+func enableFullDuplex(w http.ResponseWriter) {
+	// Do nothing, Go 1.20 and earlier do not support full duplex
+}

modules/caddyhttp/duplex_go121.go

@@ -0,0 +1,25 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build go1.21
+
+package caddyhttp
+
+import (
+	"net/http"
+)
+
+func enableFullDuplex(w http.ResponseWriter) {
+	http.NewResponseController(w).EnableFullDuplex()
+}

modules/caddyhttp/server.go

@@ -82,6 +82,12 @@ type Server struct {
 	// HTTP request headers.
 	MaxHeaderBytes int `json:"max_header_bytes,omitempty"`
 
+	// Enable full-duplex communication for HTTP/1.1 requests.
+	// Only has an effect if Caddy was built with Go 1.21 or later.
+	//
+	// TODO: This is an EXPERIMENTAL feature. Subject to change or removal.
+	EnableFullDuplex bool `json:"enable_full_duplex,omitempty"`
+
 	// Routes describes how this server will handle requests.
 	// Routes are executed sequentially. First a route's matchers
 	// are evaluated, then its grouping. If it matches and has
@@ -264,6 +270,14 @@ func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	repl := caddy.NewReplacer()
 	r = PrepareRequest(r, repl, w, s)
 
+	// enable full-duplex for HTTP/1, ensuring the entire
+	// request body gets consumed before writing the response
+	if s.EnableFullDuplex {
+		// TODO: Remove duplex_go12*.go abstraction once our
+		// minimum Go version is 1.21 or later
+		enableFullDuplex(w)
+	}
+
 	// encode the request for logging purposes before
 	// it enters any handler chain; this is necessary
 	// to capture the original request in case it gets