PCBGROUP + RSS: problem establishing an outgoing TCP connection

[Andriy Gapon]

This happens on an EC2 instance with ixv driver.
When I try to establish an outgoing TCP connection I see the following exchange.
Local side sends SYN, it receives SYN+ACK and immediately sends RST.
I tracked this down to in_pcblookup_mbuf() failing to find the corresponding inpcb.

I dug a bit deeper and this is my understanding of the issue.

When tcp_connect() calls in_pcbrehash() the inpcb gets placed into a group
determined by in_pcbgroup_bytuple() [see in_pcbgroup_update and
in_pcbgroup_byinpcb].  The inpcb does not have INP_RSS_BUCKET_SET.  Both
addresses and ports are populated at that time.

When the reply packet is received, in_pcblookup_mbuf() uses in_pcbgroup_byhash()
to look up the group because the packet has M_HASHTYPE_RSS_TCP_IPV4.
The problem is that in_pcbgroup_byhash() returns a different group and the inpcb
cannot be found.

I am very new to this code, so I would appreciate any help with further
debugging and root causing the problem.

Thank you!

-- 
Andriy Gapon