x/mobile: Calling net.Listen fails on Android 11+

[wlynxg]

Go version

go version go1.20.11 darwin/arm64

Output of go env in your module/workspace:

GO111MODULE="on"
GOARCH="arm64"
GOBIN=""
GOCACHE="/Users/xxxx/Library/Caches/go-build"
GOENV="/Users/xxxx/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="arm64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/xxxx/go/pkg/mod"
GONOPROXY="sum.golang.google.cn"
GONOSUMDB="sum.golang.google.cn"
GOOS="darwin"
GOPATH="/Users/xxxx/go"
GOPRIVATE=""
GOPROXY="https://goproxy.cn,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_arm64"
GOVCS=""
GOVERSION="go1.20.11"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/xxxx/Desktop/xxxx/gomobile/go.mod"
GOWORK=""
CGO_CFLAGS="-O2 -g"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-O2 -g"
CGO_FFLAGS="-O2 -g"
CGO_LDFLAGS="-O2 -g"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/tl/pjq29cdd6s53760n3zjwwr3c0000gn/T/go-build3441012208=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

package mobile

import (
	"fmt"
	"log"
	"net"
	"net/netip"
	"syscall"

	"github.com/wlynxg/anet"
)

func Greetings(name string) string {
	anet.SetAndroidVersion(14)
	allifaces, err := anet.Interfaces()
	if err != nil {
		return fmt.Sprintf("Error: %s!", err)
	}
	s := ""

	for _, iface := range allifaces {
		s += iface.Name
		addrs, err := anet.InterfaceAddrsByInterface(&iface)
		if err != nil {
			s += fmt.Sprintf("Error: %s", err) + "\n"
		} else {
			s += fmt.Sprintf("%s \n", addrs)
		}

		for _, addr := range addrs {
			parseAddr, err := netip.ParsePrefix(addr.String())
			if err != nil {
				continue
			}

			if parseAddr.Addr().Is4() || parseAddr.Addr().IsMulticast() {
				continue
			}

			addr := fmt.Sprintf("[%s%%%s]:0", parseAddr.Addr().String(), iface.Name)

			_, err = net.Listen("tcp", addr)
			if err != nil {
				log.Printf("listen %s error: %s", addr, err)
			}
		}
	}
	return fmt.Sprintf("Hello, %s!", s)
}

What did you see happen?

listen [fe80::d461:24ff:fe95:d487%wlan0]:0 error: listen tcp [fe80::d461:24ff:fe95:d487%wlan0]:0: bind: invalid argument
listen [fe80::b6ee:d454:7f5b:6fe%rmnet_data1]:0 error: listen tcp [fe80::b6ee:d454:7f5b:6fe%rmnet_data1]:0: bind: invalid argument
listen [fe80::64bd:d9ff:fe5b:92a6%dummy0]:0 error: listen tcp [fe80::64bd:d9ff:fe5b:92a6%dummy0]:0: bind: invalid argument
listen [fe80::e0f1:31ff:fe88:8eb%ifb0]:0 error: listen tcp [fe80::e0f1:31ff:fe88:8eb%ifb0]:0: bind: invalid argument
listen [fe80::6cbb:96ff:fe13:ff68%ifb1]:0 error: listen tcp [fe80::6cbb:96ff:fe13:ff68%ifb1]:0: bind: invalid argument
listen [fe80::b0a1:c3ff:fe6d:c67%ifb2]:0 error: listen tcp [fe80::b0a1:c3ff:fe6d:c67%ifb2]:0: bind: invalid argument
listen [fe80::d41b:7750:b2d1:8fc6%rmnet_data0]:0 error: listen tcp [fe80::d41b:7750:b2d1:8fc6%rmnet_data0]:0: bind: invalid argument
listen [fe80::84bb:a6ff:cd2d:2ff1%rmnet_data3]:0 error: listen tcp [fe80::84bb:a6ff:cd2d:2ff1%rmnet_data3]:0: bind: invalid argument
listen [fe80::5bec:aaaf:e221:d681%rmnet_data4]:0 error: listen tcp [fe80::5bec:aaaf:e221:d681%rmnet_data4]:0: bind: invalid argument

What did you expect to see?

listen success

[gabyhelp]

Similar Issues

• syscall: accept(2) syscall blocked on Android, use accept4(2) instead #45767
• x/mobile: network unreachable on Android 10+ via Network request API #52702
• net: conn.WriteToUDP([]byte("not ok"), addr) #34758
• net.ListenIP: failed when network is ip:50 #49612
• x/mobile: Calling net.InterfaceAddrs() fails on Android SDK 30 #40569
• x/mobile: fix net.Interface() and net.InterfaceAddrs() in Android11 version #61089
• x/mobile: #20722
• net.Dial fails with an ip6 addres - connect: invalid argument #43950
• net: "127.0.0.1:" should be an invalid tcp4 address for ResolveTCPAddr #56144
• net: tips all.bash test failed: interface_test.go:74: route ip+net: invalid network interface name #14706

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[wlynxg]

The error comes from https://github.com/torvalds/linux/blob/e5b3efbe1ab1793bb49ae07d56d0973267e65112/net/ipv6/af_inet6.c#L364

In my code, I specified the zone name, and go needs to obtain the corresponding relationship between zone name and zone index from zoneCache when parsing.
The data in zoneCache comes from

go/src/net/interface.go

Line 217 in 4f77a83

if ift, err = interfaceTable(0); err != nil {

,
but because there is a problem when go calls interfaceTable on the Android side #40569,
go fails when doing zone name -> zone index mapping, so in order to pass a valid zone id to the socket

I fixed this problem in anet: wlynxg/anet@a8525cb

[Zxilly]

It might be possible to commit these changes to the standard library.

[wlynxg]

It might be possible to commit these changes to the standard library.

This is difficult in some ways because the changes are tied to the Android version.

[vikulin]

The error comes from https://github.com/torvalds/linux/blob/e5b3efbe1ab1793bb49ae07d56d0973267e65112/net/ipv6/af_inet6.c#L364

In my code, I specified the zone name, and go needs to obtain the corresponding relationship between zone name and zone index from zoneCache when parsing. The data in zoneCache comes from

go/src/net/interface.go

Line 217 in 4f77a83

if ift, err = interfaceTable(0); err != nil {

,
but because there is a problem when go calls interfaceTable on the Android side #40569,
go fails when doing zone name -> zone index mapping, so in order to pass a valid zone id to the socket

I fixed this problem in anet: wlynxg/anet@a8525cb

How to get zone id ? I noticed that Android works with scope id for link local addresses not with zone name:
https://developer.android.com/reference/java/net/Inet6Address

[wlynxg]

@vikulin The zone id is actually the index of the interface

go/src/net/interface.go

Line 43 in 9d33956

Index int // positive integer that starts at one, zero is never used

.
In fact, when passing the zone id, you can choose the name

go/src/net/interface.go

Line 263 in 9d33956

index, ok = zoneCache.toIndex[name]

or directly pass the index

go/src/net/interface.go

Line 267 in 9d33956

index, _, _ = dtoi(name)

[vikulin]

@wlynxg I'm not sure that zone id is what I'm looking for. Obviously zone id = 46 is not the index since the Android device never had so many interfaces. Linux devices return interface names - this is where the difference. Code is expecting interface name but getting scope id.

nBytes, rcm, fromAddr, err := m.sock.ReadFrom(bs)
from := fromAddr.(*net.UDPAddr)
log.Infoln(from.String())

returns

[fe80::33d6:4970:9c23:5f7c%46]:9001

[wlynxg]

@vikulin The network card index numbers do not necessarily need to be in order, as long as they are unique. You can make your own rules. You can directly output iface.Index to view their ids.
When using c for ipv6 socket, the zone id passed is the index of the network.

[dr2chase]

@hyangah @ianlancetaylor