mirror of
https://github.com/tailscale/tailscale.git
synced 2024-12-03 06:56:41 +00:00
109 lines
2.4 KiB
Go
109 lines
2.4 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
|
|
// SPDX-License-Identifier: BSD-3-Clause
|
|
|
|
package dns
|
|
|
|
import (
|
|
"bytes"
|
|
"context"
|
|
|
|
"github.com/illarion/gonotify/v2"
|
|
"tailscale.com/health"
|
|
)
|
|
|
|
func (m *directManager) runFileWatcher() {
|
|
ctx, cancel := context.WithCancel(m.ctx)
|
|
defer cancel()
|
|
in, err := gonotify.NewInotify(ctx)
|
|
if err != nil {
|
|
// Oh well, we tried. This is all best effort for now, to
|
|
// surface warnings to users.
|
|
m.logf("dns: inotify new: %v", err)
|
|
return
|
|
}
|
|
|
|
const events = gonotify.IN_ATTRIB |
|
|
gonotify.IN_CLOSE_WRITE |
|
|
gonotify.IN_CREATE |
|
|
gonotify.IN_DELETE |
|
|
gonotify.IN_MODIFY |
|
|
gonotify.IN_MOVE
|
|
|
|
if err := in.AddWatch("/etc/", events); err != nil {
|
|
m.logf("dns: inotify addwatch: %v", err)
|
|
return
|
|
}
|
|
for {
|
|
events, err := in.Read()
|
|
if ctx.Err() != nil {
|
|
return
|
|
}
|
|
if err != nil {
|
|
m.logf("dns: inotify read: %v", err)
|
|
return
|
|
}
|
|
var match bool
|
|
for _, ev := range events {
|
|
if ev.Name == resolvConf {
|
|
match = true
|
|
break
|
|
}
|
|
}
|
|
if !match {
|
|
continue
|
|
}
|
|
m.checkForFileTrample()
|
|
}
|
|
}
|
|
|
|
var resolvTrampleWarnable = health.Register(&health.Warnable{
|
|
Code: "resolv-conf-overwritten",
|
|
Severity: health.SeverityMedium,
|
|
Title: "Linux DNS configuration issue",
|
|
Text: health.StaticMessage("Linux DNS config not ideal. /etc/resolv.conf overwritten. See https://tailscale.com/s/dns-fight"),
|
|
})
|
|
|
|
// checkForFileTrample checks whether /etc/resolv.conf has been trampled
|
|
// by another program on the system. (e.g. a DHCP client)
|
|
func (m *directManager) checkForFileTrample() {
|
|
m.mu.Lock()
|
|
want := m.wantResolvConf
|
|
lastWarn := m.lastWarnContents
|
|
m.mu.Unlock()
|
|
|
|
if want == nil {
|
|
return
|
|
}
|
|
|
|
cur, err := m.fs.ReadFile(resolvConf)
|
|
if err != nil {
|
|
m.logf("trample: read error: %v", err)
|
|
return
|
|
}
|
|
if bytes.Equal(cur, want) {
|
|
m.health.SetHealthy(resolvTrampleWarnable)
|
|
if lastWarn != nil {
|
|
m.mu.Lock()
|
|
m.lastWarnContents = nil
|
|
m.mu.Unlock()
|
|
m.logf("trample: resolv.conf again matches expected content")
|
|
}
|
|
return
|
|
}
|
|
if bytes.Equal(cur, lastWarn) {
|
|
// We already logged about this, so not worth doing it again.
|
|
return
|
|
}
|
|
|
|
m.mu.Lock()
|
|
m.lastWarnContents = cur
|
|
m.mu.Unlock()
|
|
|
|
show := cur
|
|
if len(show) > 1024 {
|
|
show = show[:1024]
|
|
}
|
|
m.logf("trample: resolv.conf changed from what we expected. did some other program interfere? current contents: %q", show)
|
|
m.health.SetUnhealthy(resolvTrampleWarnable, nil)
|
|
}
|