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control/controlclient: improve filter on netmap updates (#19308)

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The previous filters would allow for a handful of subtle issues such as
updating the last seen date when the key or online status had not
changed, and making online keys unconditionally make an engine update.

These have been fixed along side making no change updates from TSMP into
a no-op for the engine so we don't have to reconfigure.

A bunch of additional testing has been added as well.

Updates #12639

Signed-off-by: Claus Lensbøl <claus@tailscale.com>
This commit is contained in:
Claus Lensbøl
2026-04-14 08:43:07 -04:00
committed by GitHub
parent 0afaa29503
commit 27f1d4c15d
2 changed files with 240 additions and 41 deletions
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control/controlclient/map.go
+30 -8
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@@ -298,7 +298,12 @@ func (ms *mapSession) handleNonKeepAliveMapResponse(ctx context.Context, resp *t
ms.patchifyPeersChanged(resp)
ms.removeUnwantedDiscoUpdates(resp)
ms.removeUnwantedDiscoUpdates(resp, viaTSMP)
// TSMP learned key was rejected, no need to do any more work in the engine.
if viaTSMP && len(resp.PeersChangedPatch) == 0 {
return nil
}
ms.removeUnwantedDiscoUpdatesFromFullNetmapUpdate(resp)
ms.updateStateFromResponse(resp)
@@ -407,7 +412,7 @@ type updateStats struct {
// removeUnwantedDiscoUpdates goes over the patchified updates and reject items
// where the node is offline and has last been seen before the recorded last seen.
func (ms *mapSession) removeUnwantedDiscoUpdates(resp *tailcfg.MapResponse) {
func (ms *mapSession) removeUnwantedDiscoUpdates(resp *tailcfg.MapResponse, viaTSMP bool) {
ms.peersMu.RLock()
defer ms.peersMu.RUnlock()
@@ -422,17 +427,33 @@ func (ms *mapSession) removeUnwantedDiscoUpdates(resp *tailcfg.MapResponse) {
continue
}
existingNode, ok := ms.peers[change.NodeID]
// Accept if:
// - Node is online.
if *change.Online {
// - Cannot find the peer, don't have enough data.
if !ok {
acceptedDiscoUpdates = append(acceptedDiscoUpdates, change)
continue
}
existingNode, ok := ms.peers[change.NodeID]
// Reject if:
// - key was learned via tsmp AND,
// - existing node is online AND,
// - key did not change.
// Here to avoid a deeper reconfig in the case where we get a TSMP key
// exchange while that node is already in a connected state (from the view
// of the control plane). This is meant to keep the node stable, avoiding a
// reconfiguration of the node deeper down in the engine.
// With this, we are avoiding updating the LastSeen and Online fields from
// TSMP updates when that is not relevant, overall making the connection
// state change less, and updating the engine less.
if viaTSMP && existingNode.Online().Get() &&
*change.DiscoKey == existingNode.DiscoKey() {
continue
}
// Accept if:
// - Cannot find the peer, don't have enough data
if !ok {
// - Node is online.
if *change.Online {
acceptedDiscoUpdates = append(acceptedDiscoUpdates, change)
continue
}
@@ -497,8 +518,9 @@ func (ms *mapSession) removeUnwantedDiscoUpdatesFromFullNetmapUpdate(resp *tailc
continue
}
// Overwrite the key in the full netmap update.
// Overwrite the key and last seen in the full netmap update.
peer.DiscoKey = existingNode.DiscoKey()
*peer.LastSeen = existingNode.LastSeen().Get()
}
}