--rc; Listening on IPv4+v6 Socket instead only IPv4

ncw · October 1, 2021, 2:28pm

This behaviour comes from the Go standard library which rclone uses...

I made an issue here

github.com/golang/go

net: Listen("tcp", "0.0.0.0:1234") binds to IPv6 addresses

opened 02:28PM - 01 Oct 21 UTC

closed 04:54PM - 04 Oct 21 UTC

ncw

NeedsInvestigation FrozenDueToAge

### What version of Go are you using (`go version`)? <pre> go version go1.17….1 linux/amd64 </pre> ### Does this issue reproduce with the latest release? Yes ### What operating system and processor architecture are you using (`go env`)? <details><summary><code>go env</code> Output</summary><br><pre> GO111MODULE="" GOARCH="amd64" GOBIN="" GOCACHE="/home/ncw/.cache/go-build" GOENV="/home/ncw/.config/go/env" GOEXE="" GOEXPERIMENT="" GOFLAGS="" GOHOSTARCH="amd64" GOHOSTOS="linux" GOINSECURE="" GOMODCACHE="/home/ncw/go/pkg/mod" GONOPROXY="" GONOSUMDB="" GOOS="linux" GOPATH="/home/ncw/go" GOPRIVATE="" GOPROXY="https://proxy.golang.org,direct" GOROOT="/opt/go/go1.17" GOSUMDB="sum.golang.org" GOTMPDIR="" GOTOOLDIR="/opt/go/go1.17/pkg/tool/linux_amd64" GOVCS="" GOVERSION="go1.17.1" GCCGO="/usr/bin/gccgo" AR="ar" CC="gcc" CXX="g++" CGO_ENABLED="1" GOMOD="/dev/null" 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 -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build3014442064=/tmp/go-build -gno-record-gcc-switches" </pre></details> ### What did you do? Run this program ```go package main import ( "fmt" "log" "net" "os" "os/exec" "strings" ) func main() { if len(os.Args) != 2 { log.Fatalf("Syntax: %s bind_address", os.Args[0]) } bindAddr := os.Args[1] go func() { _, err := net.Listen("tcp", bindAddr) if err != nil { log.Fatalf("net.Listen failed: %v", err) } }() // Read netstat cmd := exec.Command("netstat", "-tuanp") out, err := cmd.Output() if err != nil { log.Fatal(err) } // Print netstat lines with our PID in pid := fmt.Sprint(os.Getpid()) for _, line := range strings.Split(string(out), "\n") { if strings.Contains(line, pid) { fmt.Println(line) } } } ``` I get this ``` $ ./listen-bug 127.0.0.1:1234 tcp 0 0 127.0.0.1:1234 0.0.0.0:* LISTEN 3179765/./listen-bu $ ./listen-bug 0.0.0.0:1234 tcp6 0 0 :::1234 :::* LISTEN 3179773/./listen-bu ``` Note the second of these is listening on IPv6 even though we explictly gave it an IPv4 bind address. ### What did you expect to see? I expected to see it not binding to IPv6 addresses, something like this ``` $ ./listen-bug 0.0.0.0:1234 tcp 0 0 0.0.0.0:1234 0.0.0.0:* LISTEN 3179765/./listen-bu ``` ### What did you see instead? I see it binding to IPv4 and IPv6 addresses ``` $ ./listen-bug 0.0.0.0:1234 tcp6 0 0 :::1234 :::* LISTEN 3179773/./listen-bu ``` This was originally discussed in the [rclone forum](https://forum.rclone.org/t/rc-listening-on-ipv4-v6-socket-instead-only-ipv4/26768)