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wgengine/magicsock: enable setting relay epAddr's as bestAddr (#16229)

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relayManager can now hand endpoint a relay epAddr for it to consider
as bestAddr.

endpoint and Conn disco ping/pong handling are now VNI-aware.

Updates tailscale/corp#27502
Updates tailscale/corp#29422

Signed-off-by: Jordan Whited <jordan@tailscale.com>
This commit is contained in:
Jordan Whited
2025-06-09 13:17:14 -07:00
committed by GitHub
parent 4456f77af7
commit 67b1693c13
5 changed files with 215 additions and 64 deletions
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45
wgengine/magicsock/relaymanager.go
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@@ -24,6 +24,11 @@ import (
// relayManager manages allocation, handshaking, and initial probing (disco
// ping/pong) of [tailscale.com/net/udprelay.Server] endpoints. The zero value
// is ready for use.
//
// [relayManager] methods can be called by [Conn] and [endpoint] while their .mu
// mutexes are held. Therefore, in order to avoid deadlocks, [relayManager] must
// never attempt to acquire those mutexes, including synchronous calls back
// towards [Conn] or [endpoint] methods that acquire them.
type relayManager struct {
initOnce sync.Once
@@ -164,6 +169,7 @@ func (r *relayManager) runLoop() {
}
type relayHandshakeDiscoMsgEvent struct {
conn *Conn // for access to [Conn] if there is no associated [relayHandshakeWork]
msg disco.Message
disco key.DiscoPublic
from netip.AddrPort
@@ -366,7 +372,7 @@ func (r *relayManager) handleRxHandshakeDiscoMsgRunLoop(event relayHandshakeDisc
ok bool
)
apv := addrPortVNI{event.from, event.vni}
switch event.msg.(type) {
switch msg := event.msg.(type) {
case *disco.BindUDPRelayEndpointChallenge:
work, ok = r.handshakeWorkByServerDiscoVNI[serverDiscoVNI{event.disco, event.vni}]
if !ok {
@@ -392,7 +398,29 @@ func (r *relayManager) handleRxHandshakeDiscoMsgRunLoop(event relayHandshakeDisc
// Update state so that future ping/pong will route to 'work'.
r.handshakeWorkAwaitingPong[work] = apv
r.addrPortVNIToHandshakeWork[apv] = work
case *disco.Ping, *disco.Pong:
case *disco.Ping:
// Always TX a pong. We might not have any associated work if ping
// reception raced with our call to [endpoint.relayEndpointReady()], so
// err on the side of enabling the remote side to use this path.
//
// Conn.handlePingLocked() makes efforts to suppress duplicate pongs
// where the same ping can be received both via raw socket and UDP
// socket on Linux. We make no such efforts here as the raw socket BPF
// program does not support Geneve-encapsulated disco, and is also
// disabled by default.
vni := virtualNetworkID{}
vni.set(event.vni)
go event.conn.sendDiscoMessage(epAddr{ap: event.from, vni: vni}, key.NodePublic{}, event.disco, &disco.Pong{
TxID: msg.TxID,
Src: event.from,
}, discoVerboseLog)
work, ok = r.addrPortVNIToHandshakeWork[apv]
if !ok {
// No outstanding work tied to this [addrPortVNI], return early.
return
}
case *disco.Pong:
work, ok = r.addrPortVNIToHandshakeWork[apv]
if !ok {
// No outstanding work tied to this [addrPortVNI], discard.
@@ -436,9 +464,13 @@ func (r *relayManager) handleHandshakeWorkDoneRunLoop(done relayEndpointHandshak
return
}
// This relay endpoint is functional.
// TODO(jwhited): Set it on done.work.ep.bestAddr if it is a betterAddr().
// We also need to conn.peerMap.setNodeKeyForEpAddr(), and ensure we clean
// it up when bestAddr changes, too.
vni := virtualNetworkID{}
vni.set(done.work.se.VNI)
addr := epAddr{ap: done.pongReceivedFrom, vni: vni}
// ep.relayEndpointReady() must be called in a new goroutine to prevent
// deadlocks as it acquires [endpoint] & [Conn] mutexes. See [relayManager]
// docs for details.
go done.work.ep.relayEndpointReady(addr, done.latency)
}
func (r *relayManager) handleNewServerEndpointRunLoop(newServerEndpoint newRelayServerEndpointEvent) {
@@ -613,6 +645,9 @@ func (r *relayManager) handshakeServerEndpoint(work *relayHandshakeWork) {
// latency, so send another ping. Since the handshake is
// complete we do not need to send an answer in front of this
// one.
//
// We don't need to TX a pong, that was already handled for us
// in handleRxHandshakeDiscoMsgRunLoop().
txPing(msgEvent.from, nil)
case *disco.Pong:
at, ok := sentPingAt[msg.TxID]