net, x/net/route: ParseRIB fail to parse utun up InterfaceMessage

[ruokeqx]

Go version

go version go1.22.6 darwin/amd64

Output of go env in your module/workspace:

GO111MODULE='on'
GOARCH='amd64'
GOBIN=''
GOCACHE='/Users/ruokeqx/Library/Caches/go-build'
GOENV='/Users/ruokeqx/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMODCACHE='/Users/ruokeqx/go/pkg/mod'
GOOS='darwin'
GOPATH='/Users/ruokeqx/go'
GOPROXY='https://goproxy.cn,direct'
GOROOT='/usr/local/opt/go1.22'
GOSUMDB='off'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/opt/go1.22/pkg/tool/darwin_amd64'
GOVCS=''
GOVERSION='go1.22.6'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='clang'
CXX='clang++'
CGO_ENABLED='1'
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 x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/d8/c7cqtvp515v7tn7xmvv6v2m00000gn/T/go-build3070326303=/tmp/go-build -gno-record-gcc-switches -fno-common'

What did you do?

try parse message from AF_ROUTE socket.

unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, unix.AF_UNSPEC)
msgs, err := route.ParseRIB(route.RIBTypeRoute, data[:n])

What did you see happen?

ParseRIB skip Interface message that indicate utun interface up

// data fetch from AF_ROUTE socket
data := []byte{112, 0, 5, 14, 0, 0, 0, 0, 81, 128, 0, 0, 28, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 220, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 237, 0, 107, 103, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}

since no RTA_IFP flag

func (w *wireFormat) parseInterfaceMessage(_ RIBType, b []byte) (Message, error) {
...
	if attrs&syscall.RTA_IFP == 0 {
		return nil, nil
	}
...
}

not sure if it is intended

What did you expect to see?

should return InterfaceMessage with Index and flags?

[gabyhelp]

Related Issues

• x/net/route: ParseRIB fails with errMessageTooShort on an AF_ROUTE message from Darwin #44740 (closed)
• x/net/route: parseInterfaceMessage broken on Dragonfly #46674
• x/net/route: TestFetchAndParseRIB failure on freebsd-386-12_0 builder #37320
• affected/package: syscall on darwin amd64 — macOS 13.0 darwin xnu #56861 (closed)
• x/net/route: TestFetchAndParseRIB fails on IPv4-only or IPv6-only kernel #19298 (closed)
• x/net/route: ParseRIB panics on message from Darwin #70528 (closed)

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

[dmitshur]

CC @neild, @ianlancetaylor.

[ianlancetaylor]

Currently the code ensures that m.Name is set in the returned InterfaceMessage. If we permit a message for which RTA_IFP is not set, then the Name field won't be set. In the standard library's net package, that in turn will mean returning a value of type net.Interface for which the Name field is not set. How should programs handle an unnamed interface? Why is the name not being returned?

[gabyhelp]

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these findings and fix any that you think are appropriate to fix.

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I'm just a bot; you probably know better than I do whether these findings really need fixing.
_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[ruokeqx]

Currently the code ensures that m.Name is set in the returned InterfaceMessage. If we permit a message for which RTA_IFP is not set, then the Name field won't be set. In the standard library's net package, that in turn will mean returning a value of type net.Interface for which the Name field is not set. How should programs handle an unnamed interface? Why is the name not being returned?

Hi, this message can be easily reproduced in my mbp(macOS 15.2).

1. go run main.go

package main

import (
	"fmt"
	"os"

	"golang.org/x/sys/unix"
)

func main() {
	routeSocket, err := unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, unix.AF_UNSPEC)
	if err != nil {
		return
	}

	data := make([]byte, os.Getpagesize())
	for {
		n, err := unix.Read(routeSocket, data)
		if err != nil {
			return
		}

		if data[3] != unix.RTM_IFINFO {
			continue
		}

		fmt.Printf("%d:%v\n", n, data[:n])
	}
}

2. sudo ifconfig utun0 mtu 1500 up

BTW, i have test for many times in my mbp, all message from NET_RT_IFLIST with RTM_IFINFO type has RTA_IFP, not guarantee in all platform.

Maybe filter work should after getting interfaceMessages in standard library? ParseRIB itself just return basic message

[ianlancetaylor]

What does the ifconfig program print for the interface? Does it give it a name?

[ruokeqx]

What does the ifconfig program print for the interface? Does it give it a name?

ifconfig print nothing, it didn't give interface a name. utun0 exists when the system starts, it already has a name.

[gopherbot]

Change https://go.dev/cl/641855 mentions this issue: net: permit Interface with no Name