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fix: Only send tailnet nodes updates with preferred DERP #7387

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Merged
merged 1 commit into from
May 4, 2023
Merged

fix: Only send tailnet nodes updates with preferred DERP #7387

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8 changes: 8 additions & 0 deletions tailnet/conn.go
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Original file line number Diff line number Diff line change
Expand Up @@ -631,6 +631,14 @@ func (c *Conn) sendNode() {
return
}
node := c.selfNode()
// Conn.UpdateNodes will skip any nodes that don't have the PreferredDERP
// set to non-zero, since we cannot reach nodes without DERP for discovery.
// Therefore, there is no point in sending the node without this, and we can
// save ourselves from churn in the tailscale/wireguard layer.
if node.PreferredDERP == 0 {
c.logger.Debug(context.Background(), "skipped sending node; no PreferredDERP", slog.F("node", node))
return
}
nodeCallback := c.nodeCallback
if nodeCallback == nil {
return
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30 changes: 30 additions & 0 deletions tailnet/conn_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -165,3 +165,33 @@ func TestTailnet(t *testing.T) {
w2.Close()
})
}

// TestConn_PreferredDERP tests that we only trigger the NodeCallback when we have a preferred DERP server.
func TestConn_PreferredDERP(t *testing.T) {
t.Parallel()
ctx, cancel := context.WithTimeout(context.Background(), testutil.WaitShort)
defer cancel()
logger := slogtest.Make(t, nil).Leveled(slog.LevelDebug)
derpMap := tailnettest.RunDERPAndSTUN(t)
conn, err := tailnet.NewConn(&tailnet.Options{
Addresses: []netip.Prefix{netip.PrefixFrom(tailnet.IP(), 128)},
Logger: logger.Named("w1"),
DERPMap: derpMap,
})
require.NoError(t, err)
defer func() {
err := conn.Close()
require.NoError(t, err)
}()
// buffer channel so callback doesn't block
nodes := make(chan *tailnet.Node, 50)
conn.SetNodeCallback(func(node *tailnet.Node) {
nodes <- node
})
select {
case node := <-nodes:
require.Equal(t, 1, node.PreferredDERP)
case <-ctx.Done():
t.Fatal("timed out waiting for node")
}
}