robustsession: do not write to session after it was deleted

stapelberg · stapelberg · commit feb3cb921fab · 2025-07-16T17:13:39.000+02:00
stopAndMaybeNotify() is not safe to call after the robustsession was deleted,
as notifications are written to the robustsession’s channel, which is closed.

Instead, use stopWithoutNotifying() after session deletion.
diff --git a/robustsession/robustsession.go b/robustsession/robustsession.go
@@ -543,12 +543,16 @@ func (us *unavailabilityState) start() {
 	})
 }
 
-func (us *unavailabilityState) stopAndMaybeNotify() {
+func (us *unavailabilityState) stopWithoutNotifying() {
 	if us.timer == nil {
 		return
 	}
 	us.timer.Stop()
 	us.timer = nil
+}
+
+func (us *unavailabilityState) stopAndMaybeNotify() {
+	us.stopWithoutNotifying()
 	if us.hasNotified() {
 		us.session.injectUnavailabilityMessage("RobustIRC connectivity restored!")
 	}
@@ -693,7 +697,7 @@ func (s *RobustSession) getMessages() {
 		// server fails.
 		time.Sleep(time.Duration(250+rand.Int63n(250)) * time.Millisecond)
 	}
-	unavailability.stopAndMaybeNotify()
+	unavailability.stopWithoutNotifying()
 }
 
 // SessionId returns a string that identifies the session. It should be used in

Original file line number	Diff line number	Diff line change
`@@ -543,12 +543,16 @@ func (us *unavailabilityState) start() {`
`543`	`543`	`})`
`544`	`544`	`}`
`545`	`545`
`546`		`-func (us *unavailabilityState) stopAndMaybeNotify() {`
	`546`	`+func (us *unavailabilityState) stopWithoutNotifying() {`
`547`	`547`	`if us.timer == nil {`
`548`	`548`	`return`
`549`	`549`	`}`
`550`	`550`	`us.timer.Stop()`
`551`	`551`	`us.timer = nil`
	`552`	`+}`
	`553`	`+`
	`554`	`+func (us *unavailabilityState) stopAndMaybeNotify() {`
	`555`	`+ us.stopWithoutNotifying()`
`552`	`556`	`if us.hasNotified() {`
`553`	`557`	`us.session.injectUnavailabilityMessage("RobustIRC connectivity restored!")`
`554`	`558`	`}`
`@@ -693,7 +697,7 @@ func (s *RobustSession) getMessages() {`
`693`	`697`	`// server fails.`
`694`	`698`	`time.Sleep(time.Duration(250+rand.Int63n(250)) * time.Millisecond)`
`695`	`699`	`}`
`696`		`- unavailability.stopAndMaybeNotify()`
	`700`	`+ unavailability.stopWithoutNotifying()`
`697`	`701`	`}`
`698`	`702`
`699`	`703`	`// SessionId returns a string that identifies the session. It should be used in`