net/dns: add a health warning when Linux /etc/resolv.conf is overwritten
"sync"
"time"
+ "tailscale.com/health"
"tailscale.com/net/dns/resolvconffile"
"tailscale.com/types/logger"
"tailscale.com/util/dnsname"
@@ -293,10 +294,10 @@ func (m *directManager) setWant(want []byte) {
m.wantResolvConf = want
}
+var warnTrample = health.NewWarnable()
+
// checkForFileTrample checks whether /etc/resolv.conf has been trampled
// by another program on the system. (e.g. a DHCP client)
-//
-// For now (2022-11-12) this only logs on changes in state.
func (m *directManager) checkForFileTrample() {
m.mu.Lock()
want := m.wantResolvConf
@@ -313,13 +314,13 @@ func (m *directManager) checkForFileTrample() {
return
}
if bytes.Equal(cur, want) {
+ warnTrample.Set(nil)
if lastWarn != nil {
m.mu.Lock()
m.lastWarnContents = nil
m.mu.Unlock()
m.logf("trample: resolv.conf again matches expected content")
}
- // TODO(bradfitz): register with health package that all is well
return
}
if bytes.Equal(cur, lastWarn) {
@@ -336,7 +337,7 @@ func (m *directManager) checkForFileTrample() {
show = show[:1024]
}
m.logf("trample: resolv.conf changed from what we expected. did some other program interfere? current contents: %q", show)
- // TODO(bradfitz): register with health package that something is wrong
+ warnTrample.Set(errors.New("Linux DNS config not ideal. /etc/resolv.conf overwritten. See https://tailscale.com/s/dns-fight"))
}
func (m *directManager) SetDNS(config OSConfig) (err error) {
