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wgengine/magicsock: send CallMeMaybeVia for relay endpoints (#16360)

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If we acted as the allocator we are responsible for signaling it to the
remote peer in a CallMeMaybeVia message over DERP.

Updates tailscale/corp#27502

Signed-off-by: Jordan Whited <jordan@tailscale.com>
This commit is contained in:
Jordan Whited 2025-06-23 16:13:58 -07:00 committed by GitHub
parent a589863d61
commit 31eebdb0f8
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1 changed files with 34 additions and 4 deletions
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38
wgengine/magicsock/relaymanager.go
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@ -30,8 +30,9 @@ import (
//
// [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.
// never attempt to acquire those mutexes synchronously from its runLoop(),
// including synchronous calls back towards [Conn] or [endpoint] methods that
// acquire them.
type relayManager struct {
initOnce sync.Once
@ -584,9 +585,37 @@ func (r *relayManager) handleNewServerEndpointRunLoop(newServerEndpoint newRelay
byServerDisco[newServerEndpoint.se.ServerDisco] = work
r.handshakeWorkByServerDiscoVNI[sdv] = work
if newServerEndpoint.server.IsValid() {
// Send CallMeMaybeVia to the remote peer if we allocated this endpoint.
go r.sendCallMeMaybeVia(work.ep, work.se)
}
go r.handshakeServerEndpoint(work)
}
// sendCallMeMaybeVia sends a [disco.CallMeMaybeVia] to ep over DERP. It must be
// called as part of a goroutine independent from runLoop(), for 2 reasons:
// 1. it acquires ep.mu (refer to [relayManager] docs for reasoning)
// 2. it makes a networking syscall, which can introduce unwanted backpressure
func (r *relayManager) sendCallMeMaybeVia(ep *endpoint, se udprelay.ServerEndpoint) {
ep.mu.Lock()
derpAddr := ep.derpAddr
ep.mu.Unlock()
epDisco := ep.disco.Load()
if epDisco == nil || !derpAddr.IsValid() {
return
}
callMeMaybeVia := &disco.CallMeMaybeVia{
ServerDisco: se.ServerDisco,
LamportID: se.LamportID,
VNI: se.VNI,
BindLifetime: se.BindLifetime.Duration,
SteadyStateLifetime: se.SteadyStateLifetime.Duration,
AddrPorts: se.AddrPorts,
}
ep.c.sendDiscoMessage(epAddr{ap: derpAddr}, ep.publicKey, epDisco.key, callMeMaybeVia, discoVerboseLog)
}
func (r *relayManager) handshakeServerEndpoint(work *relayHandshakeWork) {
done := relayEndpointHandshakeWorkDoneEvent{work: work}
r.ensureDiscoInfoFor(work)
@ -779,8 +808,9 @@ func (r *relayManager) allocateSingleServer(ctx context.Context, wg *sync.WaitGr
se, err := doAllocate(ctx, server, [2]key.DiscoPublic{ep.c.discoPublic, remoteDisco.key})
if err == nil {
relayManagerInputEvent(r, ctx, &r.newServerEndpointCh, newRelayServerEndpointEvent{
ep: ep,
se: se,
ep: ep,
se: se,
server: server, // we allocated this endpoint (vs CallMeMaybeVia reception), mark it as such
})
return
}