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wgengine, ipn/ipnlocal: route PeerForIP through LocalBackend's live data

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userspaceEngine.PeerForIP read from e.netMap.Peers and
e.lastCfgFull.Peers, both of which go stale when peers arrive via
netmap deltas (which skip Engine.SetNetworkMap and Engine.Reconfig).
Every PeerForIP caller (Engine.Ping, the TSMP disco-key handler,
pendopen diagnostics, tsdial.Dialer.UseNetstackForIP, and
LocalBackend.GetPeerEndpointChanges) would report "no matching peer"
for freshly-added peers.

Fix it the same way SetPeerByIPPacketFunc fixed the outbound packet
hot path: have LocalBackend install a callback that reads the live
nodeBackend. nb.NodeByAddr is built from both SelfNode and Peers
(updateNodeByAddrLocked), so a single lookup covers the common case
with IsSelf set when the matched node ID is SelfNode's. The subnet-
route / exit-node-default-route slow path goes through a new
Engine.PeerKeyForIP that exposes the engine's AllowedIPs BART table
(the same table the outbound packet hot path already consults, with
exit-node selection honored), and resolves the matched key back to a
NodeView via the live nodeBackend.

Updates #12542

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Change-Id: I0d4b0d8997c8e796b7367c46b49b61d4fdc717b0
This commit is contained in:
Brad Fitzpatrick
2026-06-23 14:37:15 -07:00
committed by Brad Fitzpatrick
parent e9ae398199
commit d4f2917c1b
5 changed files with 392 additions and 58 deletions
Download Patch File Download Diff File Expand all files Collapse all files
wgengine/userspace.go
+35 -57
View File
@@ -35,7 +35,6 @@ import (
"tailscale.com/net/netmon"
"tailscale.com/net/packet"
"tailscale.com/net/sockstats"
"tailscale.com/net/tsaddr"
"tailscale.com/net/tsdial"
"tailscale.com/net/tstun"
"tailscale.com/syncs"
@@ -124,6 +123,11 @@ type userspaceEngine struct {
// the per-packet wgdev callback without locking.
peerByIPRoute atomic.Pointer[bart.Table[key.NodePublic]]
// peerForIP, if non-nil, is the callback installed via
// [userspaceEngine.SetPeerForIPFunc]. PeerForIP delegates to it
// for the cold-path control lookups (Ping, TSMP, pendopen, etc).
peerForIP atomic.Pointer[func(netip.Addr) (_ PeerForIP, ok bool)]
lastCfgFull wgcfg.Config
lastRouter *router.Config
lastDNSConfig dns.ConfigView // or invalid if none
@@ -1571,65 +1575,39 @@ func (e *userspaceEngine) ProbeLocks() {
e.wgLock.Unlock()
}
// PeerForIP returns the Node in the wireguard config
// that's responsible for handling the given IP address.
//
// If none is found in the wireguard config but one is found in
// the netmap, it's described in an error.
//
// peerForIP acquires both e.mu and e.wgLock, but neither at the same
// time.
func (e *userspaceEngine) PeerForIP(ip netip.Addr) (ret PeerForIP, ok bool) {
e.mu.Lock()
nm := e.netMap
e.mu.Unlock()
// SetPeerForIPFunc installs the callback used by [userspaceEngine.PeerForIP].
// See [Engine.SetPeerForIPFunc].
func (e *userspaceEngine) SetPeerForIPFunc(fn func(netip.Addr) (PeerForIP, bool)) {
if fn == nil {
e.peerForIP.Store(nil)
return
}
e.peerForIP.Store(&fn)
}
if nm == nil {
// PeerKeyForIP looks up ip in the engine's AllowedIPs table
// ([userspaceEngine.peerByIPRoute]). See [Engine.PeerKeyForIP].
func (e *userspaceEngine) PeerKeyForIP(ip netip.Addr) (pk key.NodePublic, route netip.Prefix, ok bool) {
if !ip.IsValid() {
return pk, route, false
}
rt := e.peerByIPRoute.Load()
if rt == nil {
return pk, route, false
}
route, pk, ok = rt.LookupPrefixLPM(netip.PrefixFrom(ip, ip.BitLen()))
return pk, route, ok
}
// PeerForIP returns the node responsible for handling the given IP.
// It delegates to the callback installed via [SetPeerForIPFunc]; engines
// without an installed callback return (zero, false).
func (e *userspaceEngine) PeerForIP(ip netip.Addr) (ret PeerForIP, ok bool) {
if !ip.IsValid() {
return ret, false
}
// Check for exact matches before looking for subnet matches.
// TODO(bradfitz): add maps for these. on NetworkMap?
for _, p := range nm.Peers {
for i := range p.Addresses().Len() {
a := p.Addresses().At(i)
if a.Addr() == ip && a.IsSingleIP() && tsaddr.IsTailscaleIP(ip) {
return PeerForIP{Node: p, Route: a}, true
}
}
}
addrs := nm.GetAddresses()
for i := range addrs.Len() {
if a := addrs.At(i); a.Addr() == ip && a.IsSingleIP() && tsaddr.IsTailscaleIP(ip) {
return PeerForIP{Node: nm.SelfNode, IsSelf: true, Route: a}, true
}
}
e.wgLock.Lock()
defer e.wgLock.Unlock()
// TODO(bradfitz): this is O(n peers). Add ART to netaddr?
var best netip.Prefix
var bestKey key.NodePublic
for _, p := range e.lastCfgFull.Peers {
for _, cidr := range p.AllowedIPs {
if !cidr.Contains(ip) {
continue
}
if !best.IsValid() || cidr.Bits() > best.Bits() {
best = cidr
bestKey = p.PublicKey
}
}
}
// And another pass. Probably better than allocating a map per peerForIP
// call. But TODO(bradfitz): add a lookup map to netmap.NetworkMap.
if !bestKey.IsZero() {
for _, p := range nm.Peers {
if p.Key() == bestKey {
return PeerForIP{Node: p, Route: best}, true
}
}
if fn := e.peerForIP.Load(); fn != nil {
return (*fn)(ip)
}
return ret, false
}
wgengine/wgengine.go
+37 -1
View File
@@ -100,9 +100,45 @@ type Engine interface {
ResetAndStop() (*Status, error)
// PeerForIP returns the node to which the provided IP routes,
// if any. If none is found, (nil, false) is returned.
// if any. If none is found, (zero, false) is returned.
//
// Despite the name, it can return the self node (with
// PeerForIP.IsSelf set). It handles Tailscale IPs, subnet-routed
// IPs, and exit-node global internet IPs, returning whichever
// node would handle that traffic.
//
// This is the cold path used by Ping, TSMP, pendopen diagnostics,
// and debug endpoints. It uses the same underlying data structures
// as the wireguard-go outbound packet path
// ([Engine.SetPeerByIPPacketFunc]), but is slower because it
// returns richer data (a full NodeView, the matched route prefix,
// and the IsSelf flag) requiring extra lookups.
//
// In production, the lookup is implemented by LocalBackend and
// plumbed in via [Engine.SetPeerForIPFunc]; the engine itself holds
// no peer-lookup state on this path.
PeerForIP(netip.Addr) (_ PeerForIP, ok bool)
// SetPeerForIPFunc installs a callback used by [Engine.PeerForIP].
// It parallels [Engine.SetPeerByIPPacketFunc] but serves the
// cold-path control lookups (Ping, TSMP, pendopen diagnostics,
// [tsdial.Dialer.UseNetstackForIP], debug endpoints).
//
// If fn is nil, PeerForIP returns (zero, false) for every IP.
//
// LocalBackend installs a func backed by the live nodeBackend for
// exact-match and self addresses, with [Engine.PeerKeyForIP]
// supplying the subnet-route / exit-node fallback.
SetPeerForIPFunc(fn func(netip.Addr) (_ PeerForIP, ok bool))
// PeerKeyForIP returns the peer's NodePublic and the matched prefix
// for the longest-prefix match of ip in the engine's AllowedIPs
// table (the wireguard config most recently installed via
// [Engine.Reconfig]). Exit-node selection is honored: an unselected
// exit node's 0.0.0.0/0 is not matched. It is the same table the
// outbound packet hot path consults via [Engine.SetPeerByIPPacketFunc].
PeerKeyForIP(netip.Addr) (_ key.NodePublic, _ netip.Prefix, ok bool)
// GetFilter returns the current packet filter, if any.
GetFilter() *filter.Filter