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ipn/ipnlocal: introduce the concept of client-side-reachability (#17367)

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The control plane will sometimes determine that a node is not online,
while the node is still able to connect to its peers. This patch
doesn’t solve this problem, but it does mitigate it.

This PR introduces the `client-side-reachability` node attribute that
switches the node to completely ignore the online signal from control.

In the future, the client itself should collect reachability data from
active Wireguard flows and Tailscale pings.

Updates #17366
Updates tailscale/corp#30379
Updates tailscale/corp#32686

Signed-off-by: Simon Law <sfllaw@tailscale.com>
This commit is contained in:
Simon Law
2025-10-02 16:01:55 -07:00
committed by GitHub
parent 24e38eb729
commit cd523eae52
4 changed files with 118 additions and 2 deletions
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ipn/ipnlocal/local.go
+10 -2
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@@ -7240,6 +7240,10 @@ func suggestExitNode(report *netcheck.Report, nb *nodeBackend, prevSuggestion ta
// the lowest latency to this device. For peers without a DERP home, we look for
// geographic proximity to this device's DERP home.
func suggestExitNodeUsingDERP(report *netcheck.Report, nb *nodeBackend, prevSuggestion tailcfg.StableNodeID, selectRegion selectRegionFunc, selectNode selectNodeFunc, allowList set.Set[tailcfg.StableNodeID]) (res apitype.ExitNodeSuggestionResponse, err error) {
// TODO(sfllaw): Context needs to be plumbed down here to support
// reachability testing.
ctx := context.TODO()
netMap := nb.NetMap()
if report == nil || report.PreferredDERP == 0 || netMap == nil || netMap.DERPMap == nil {
return res, ErrNoPreferredDERP
@@ -7248,7 +7252,7 @@ func suggestExitNodeUsingDERP(report *netcheck.Report, nb *nodeBackend, prevSugg
// since the netmap doesn't include delta updates (e.g., home DERP or Online
// status changes) from the control plane since the last full update.
candidates := nb.AppendMatchingPeers(nil, func(peer tailcfg.NodeView) bool {
if !peer.Valid() || !peer.Online().Get() {
if !peer.Valid() || !nb.PeerIsReachable(ctx, peer) {
return false
}
if allowList != nil && !allowList.Contains(peer.StableID()) {
@@ -7367,6 +7371,10 @@ var ErrNoNetMap = errors.New("no network map, try again later")
// the node’s [tailcfg.Location]. To be eligible for consideration, the node
// must have NodeAttrSuggestExitNode in its CapMap.
func suggestExitNodeUsingTrafficSteering(nb *nodeBackend, allowed set.Set[tailcfg.StableNodeID]) (apitype.ExitNodeSuggestionResponse, error) {
// TODO(sfllaw): Context needs to be plumbed down here to support
// reachability testing.
ctx := context.TODO()
nm := nb.NetMap()
if nm == nil {
return apitype.ExitNodeSuggestionResponse{}, ErrNoNetMap
@@ -7386,7 +7394,7 @@ func suggestExitNodeUsingTrafficSteering(nb *nodeBackend, allowed set.Set[tailcf
if !p.Valid() {
return false
}
if !p.Online().Get() {
if !nb.PeerIsReachable(ctx, p) {
return false
}
if allowed != nil && !allowed.Contains(p.StableID()) {