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net/tsdial: assume all connections are affected if no default route is present

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If this happens, it results in us pessimistically closing more
connections than might be necessary, but is more correct since we won't
"miss" a change to the default route interface and keep trying to send
data over a nonexistent interface, or one that can't reach the internet.

Updates tailscale/corp#19124

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: Ia0b8b04cb8cdcb0da0155fd08751c9dccba62c1a
This commit is contained in:
Andrew Dunham 2024-04-17 10:59:30 -04:00
parent 9e1c86901b
commit 375617c5c8
1 changed files with 15 additions and 1 deletions
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16
net/tsdial/tsdial.go
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@ -142,10 +142,16 @@ func (d *Dialer) SetNetMon(netMon *netmon.Monitor) {
}
var (
metricLinkChangeConnClosed = clientmetric.NewCounter("tsdial_linkchange_closes")
metricLinkChangeConnClosed = clientmetric.NewCounter("tsdial_linkchange_closes")
metricChangeDeltaNoDefaultRoute = clientmetric.NewCounter("tsdial_changedelta_no_default_route")
)
func (d *Dialer) linkChanged(delta *netmon.ChangeDelta) {
// Track how often we see ChangeDeltas with no DefaultRouteInterface.
if delta.New.DefaultRouteInterface == "" {
metricChangeDeltaNoDefaultRoute.Add(1)
}
d.mu.Lock()
defer d.mu.Unlock()
var anyClosed bool
@ -179,6 +185,14 @@ func changeAffectsConn(delta *netmon.ChangeDelta, conn net.Conn) bool {
delta.Old.HTTPProxy != delta.New.HTTPProxy {
return true
}
// In a few cases, we don't have a new DefaultRouteInterface (e.g. on
// Android; see tailscale/corp#19124); if so, pessimistically assume
// that all connections are affected.
if delta.New.DefaultRouteInterface == "" {
return true
}
if !delta.New.HasIP(lip) && delta.Old.HasIP(lip) {
// Our interface with this source IP went away.
return true