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types/result, util/lineiter: add package for a result type, use it

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This adds a new generic result type (motivated by golang/go#70084) to
try it out, and uses it in the new lineutil package (replacing the old
lineread package), changing that package to return iterators:
sometimes over []byte (when the input is all in memory), but sometimes
iterators over results of []byte, if errors might happen at runtime.

Updates #12912
Updates golang/go#70084

Change-Id: Iacdc1070e661b5fb163907b1e8b07ac7d51d3f83
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick
2024-11-04 20:49:40 -08:00
committed by Brad Fitzpatrick
parent 809a6eba80
commit 01185e436f
20 changed files with 290 additions and 139 deletions
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37
net/netmon/interfaces_linux.go
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@ -23,7 +23,7 @@ import (
"go4.org/mem"
"golang.org/x/sys/unix"
"tailscale.com/net/netaddr"
"tailscale.com/util/lineread"
"tailscale.com/util/lineiter"
)
func init() {
@ -32,11 +32,6 @@ func init() {
var procNetRouteErr atomic.Bool
// errStopReading is a sentinel error value used internally by
// lineread.File callers to stop reading. It doesn't escape to
// callers/users.
var errStopReading = errors.New("stop reading")
/*
Parse 10.0.0.1 out of:
@ -52,44 +47,42 @@ func likelyHomeRouterIPLinux() (ret netip.Addr, myIP netip.Addr, ok bool) {
}
lineNum := 0
var f []mem.RO
err := lineread.File(procNetRoutePath, func(line []byte) error {
for lr := range lineiter.File(procNetRoutePath) {
line, err := lr.Value()
if err != nil {
procNetRouteErr.Store(true)
log.Printf("interfaces: failed to read /proc/net/route: %v", err)
return ret, myIP, false
}
lineNum++
if lineNum == 1 {
// Skip header line.
return nil
continue
}
if lineNum > maxProcNetRouteRead {
return errStopReading
break
}
f = mem.AppendFields(f[:0], mem.B(line))
if len(f) < 4 {
return nil
continue
}
gwHex, flagsHex := f[2], f[3]
flags, err := mem.ParseUint(flagsHex, 16, 16)
if err != nil {
return nil // ignore error, skip line and keep going
continue // ignore error, skip line and keep going
}
if flags&(unix.RTF_UP|unix.RTF_GATEWAY) != unix.RTF_UP|unix.RTF_GATEWAY {
return nil
continue
}
ipu32, err := mem.ParseUint(gwHex, 16, 32)
if err != nil {
return nil // ignore error, skip line and keep going
continue // ignore error, skip line and keep going
}
ip := netaddr.IPv4(byte(ipu32), byte(ipu32>>8), byte(ipu32>>16), byte(ipu32>>24))
if ip.IsPrivate() {
ret = ip
return errStopReading
break
}
return nil
})
if errors.Is(err, errStopReading) {
err = nil
}
if err != nil {
procNetRouteErr.Store(true)
log.Printf("interfaces: failed to read /proc/net/route: %v", err)
}
if ret.IsValid() {
// Try to get the local IP of the interface associated with