net/http: request.Method is wrong when path start by //

[Eraac]

What version of Go are you using (go version)?

$ go version
go version go1.11.4 darwin/amd64

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/kevin/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/kevin/code/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/Cellar/go/1.11.4/libexec"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.11.4/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/kevin/code/go/src/gitlab.com/cyclesinfos/consumer/station-state/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/43/45xhjfkn0xbbr4flsgzh879h0000gn/T/go-build866475413=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

send post request with url start with two // (tbh it's was a mistake)

What did you expect to see?

server receive a post request

What did you see instead?

server receive a get request

Code

package main

import (
	"fmt"
	"net/http"
	"net/http/httputil"
	"time"
)

func main() {
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		fmt.Printf("method: %s\n", r.Method)
	})

	go func(){_ = http.ListenAndServe(":8080", http.DefaultServeMux)}()

	client := http.Client{Timeout: time.Second}
	req, _ := http.NewRequest(http.MethodPost, "http://localhost:8080//route", nil)
	_, _ = client.Do(req)

	time.Sleep(time.Millisecond * 500)

	bs, _ := httputil.DumpRequest(req, false)
	fmt.Printf("\n----\n%s", string(bs))
}

Output

method: GET

----
POST //route HTTP/1.1
Host: localhost:8080

[agnivade]

/cc @bradfitz

[Gnouc]

@Eraac With this patch:

diff --git a/src/net/http/server.go b/src/net/http/server.go
index aa9c3f5d2e..88f53ff5ac 100644
--- a/src/net/http/server.go
+++ b/src/net/http/server.go
@@ -2336,7 +2336,11 @@ func (mux *ServeMux) Handler(r *Request) (h Handler, pattern string) {
                _, pattern = mux.handler(host, path)
                url := *r.URL
                url.Path = path
-               return RedirectHandler(url.String(), StatusMovedPermanently), pattern
+               status := StatusMovedPermanently
+               if r.Method != "GET" || r.Method != "HEAD" {
+                       status = StatusTemporaryRedirect
+               }
+               return RedirectHandler(url.String(), status), pattern
        }
 
        return mux.handler(host, r.URL.Path)

You will get expected result.

But IMHO, we should return 500 error with a message like redirect with form data without user interaction won't be perform. HTTP spec requires response to a request other than GET or HEAD, the user agent MUST NOT automatically redirect the request unless it can be confirmed by the user

How do you think @bradfitz ?