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wgengine/magicsock: make Conn.Send() lazyEndpoint aware (#16465)

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A lazyEndpoint may end up on this TX codepath when wireguard-go is
deemed "under load" and ends up transmitting a cookie reply using the
received conn.Endpoint.

Updates tailscale/corp#20732
Updates tailscale/corp#30042

Signed-off-by: Jordan Whited <jordan@tailscale.com>
This commit is contained in:
Jordan Whited
2025-07-07 08:45:13 -07:00
committed by GitHub
parent 84eac7b8de
commit 540eb05638
1 changed files with 15 additions and 6 deletions
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21
wgengine/magicsock/magicsock.go
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@@ -1363,12 +1363,18 @@ func (c *Conn) Send(buffs [][]byte, ep conn.Endpoint, offset int) (err error) {
metricSendDataNetworkDown.Add(n)
return errNetworkDown
}
if ep, ok := ep.(*endpoint); ok {
switch ep := ep.(type) {
case *endpoint:
return ep.send(buffs, offset)
case *lazyEndpoint:
// A [*lazyEndpoint] may end up on this TX codepath when wireguard-go is
// deemed "under handshake load" and ends up transmitting a cookie reply
// using the received [conn.Endpoint] in [device.SendHandshakeCookie].
if ep.src.ap.Addr().Is6() {
return c.pconn6.WriteBatchTo(buffs, ep.src, offset)
}
return c.pconn4.WriteBatchTo(buffs, ep.src, offset)
}
// If it's not of type *endpoint, it's probably *lazyEndpoint, which means
// we don't actually know who the peer is and we're waiting for wireguard-go
// to switch the endpoint. See go/corp/20732.
return nil
}
@@ -1702,6 +1708,11 @@ func (c *Conn) receiveIP(b []byte, ipp netip.AddrPort, cache *epAddrEndpointCach
}
// TODO(jwhited): reuse [lazyEndpoint] across calls to receiveIP()
// for the same batch & [epAddr] src.
//
// TODO(jwhited): implement [lazyEndpoint] integration to call
// [endpoint.noteRecvActivity], which triggers just-in-time
// wireguard-go configuration of the peer, prior to peer lookup
// within wireguard-go.
return &lazyEndpoint{c: c, src: src}, size, true
}
cache.epAddr = src
@@ -1709,8 +1720,6 @@ func (c *Conn) receiveIP(b []byte, ipp netip.AddrPort, cache *epAddrEndpointCach
cache.gen = de.numStopAndReset()
ep = de
}
// TODO(jwhited): consider the implications of not recording this receive
// activity due to an early [lazyEndpoint] return above.
now := mono.Now()
ep.lastRecvUDPAny.StoreAtomic(now)
ep.noteRecvActivity(src, now)