When a tsnet.Server dials its own Tailscale IP, TCP SYN packets are
silently dropped. In inject(), outbound packets with dst=self fail the
shouldSendToHost check and fall through to WireGuard, which has no peer
for the node's own address.
Fix this by detecting self-addressed packets in inject() using isLocalIP
and delivering them back into gVisor's network stack as inbound packets
via a new DeliverLoopback method on linkEndpoint. The outbound packet
must be re-serialized into a new PacketBuffer because outbound packets
have their headers parsed into separate views, but DeliverNetworkPacket
expects raw unparsed data.
Updates #18829
Signed-off-by: James Tucker <james@tailscale.com>
James Tucker
0fb207c3d0