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ipn/{ipnlocal,localapi}: ensure watcher is installed before /watch-ipn-bus/ responds with 200

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This change delays the first flush in the /watch-ipn-bus/ handler
until after the watcher has been successfully installed on the IPN
bus. It does this by adding a new onWatchAdded callback to
LocalBackend.WatchNotifications().

Without this, the endpoint returns a 200 almost immediatly, and
only then installs a watcher for IPN events.  This means there's a
small window where events could be missed by clients after calling
WatchIPNBus().

Fixes tailscale/corp#8594.

Signed-off-by: salman <salman@tailscale.com>
This commit is contained in:
salman
2023-01-17 20:59:03 +00:00
committed by salman
parent 3eb986fe05
commit eec734a578
3 changed files with 48 additions and 5 deletions
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14
ipn/ipnlocal/local.go
View File

@@ -1802,13 +1802,17 @@ func (b *LocalBackend) readPoller() {
//
// WatchNotifications blocks until ctx is done.
//
// The provided fn will only be called with non-nil pointers. The caller must
// not modify roNotify. If fn returns false, the watch also stops.
// The provided onWatchAdded, if non-nil, will be called once the watcher
// is installed.
//
// The provided fn will be called for each notification. It will only be
// called with non-nil pointers. The caller must not modify roNotify. If
// fn returns false, the watch also stops.
//
// Failure to consume many notifications in a row will result in dropped
// notifications. There is currently (2022-11-22) no mechanism provided to
// detect when a message has been dropped.
func (b *LocalBackend) WatchNotifications(ctx context.Context, mask ipn.NotifyWatchOpt, fn func(roNotify *ipn.Notify) (keepGoing bool)) {
func (b *LocalBackend) WatchNotifications(ctx context.Context, mask ipn.NotifyWatchOpt, onWatchAdded func(), fn func(roNotify *ipn.Notify) (keepGoing bool)) {
ch := make(chan *ipn.Notify, 128)
origFn := fn
@@ -1858,6 +1862,10 @@ func (b *LocalBackend) WatchNotifications(ctx context.Context, mask ipn.NotifyWa
b.mu.Unlock()
}()
if onWatchAdded != nil {
onWatchAdded()
}
if ini != nil {
if !fn(ini) {
return