relayUDP started a goroutine for every domain-addressed datagram and
each lookup opened its own netstack UDP endpoint, so the lookups in
flight were bounded only by the client's send rate: one proxy user could
grow the panel by gigabytes and exhaust the outbound stack's ports,
stalling every user of that outbound.
One association may now have 32 datagrams waiting on DNS and drops the
rest, a cached name is delivered from the reader loop without a lookup,
and resolveTunnelVia takes one of 1024 process-wide slots before it
opens an endpoint, which also covers the TCP CONNECT path.
MHSanaei
bc2c64d901