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tailscale/net/interfaces/interfaces_darwin.go

75 lines
1.8 KiB
Go

// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package interfaces
import (
"errors"
"os/exec"
"go4.org/mem"
"inet.af/netaddr"
"tailscale.com/util/lineread"
"tailscale.com/version"
)
/*
Parse out 10.0.0.1 from:
$ netstat -r -n -f inet
Routing tables
Internet:
Destination Gateway Flags Netif Expire
default 10.0.0.1 UGSc en0
default link#14 UCSI utun2
10/16 link#4 UCS en0 !
10.0.0.1/32 link#4 UCS en0 !
...
*/
func likelyHomeRouterIPDarwinExec() (ret netaddr.IP, ok bool) {
if version.IsMobile() {
// Don't try to do subprocesses on iOS. Ends up with log spam like:
// kernel: "Sandbox: IPNExtension(86580) deny(1) process-fork"
// This is why we have likelyHomeRouterIPDarwinSyscall.
return ret, false
}
cmd := exec.Command("/usr/sbin/netstat", "-r", "-n", "-f", "inet")
stdout, err := cmd.StdoutPipe()
if err != nil {
return
}
if err := cmd.Start(); err != nil {
return
}
defer cmd.Wait()
var f []mem.RO
lineread.Reader(stdout, func(lineb []byte) error {
line := mem.B(lineb)
if !mem.Contains(line, mem.S("default")) {
return nil
}
f = mem.AppendFields(f[:0], line)
if len(f) < 3 || !f[0].EqualString("default") {
return nil
}
ipm, flagsm := f[1], f[2]
if !mem.Contains(flagsm, mem.S("G")) {
return nil
}
ip, err := netaddr.ParseIP(string(mem.Append(nil, ipm)))
if err == nil && isPrivateIP(ip) {
ret = ip
// We've found what we're looking for.
return stopReadingNetstatTable
}
return nil
})
return ret, !ret.IsZero()
}
var stopReadingNetstatTable = errors.New("found private gateway")