tree 4e41be5e40ec6982ee4b6f8d11ec6a9b6bd56998
parent 56defd4dc08f361bdf74c6cb457aebb1ccf442d1
author Eric Dumazet <eric.dumazet@gmail.com> 1272406400 -0700
committer Paul Gortmaker <paul.gortmaker@windriver.com> 1331737085 -0400

net: sk_add_backlog() take rmem_alloc into account

commit c377411f2494a931ff7facdbb3a6839b1266bcf6 upstream.

Current socket backlog limit is not enough to really stop DDOS attacks,
because user thread spend many time to process a full backlog each
round, and user might crazy spin on socket lock.

We should add backlog size and receive_queue size (aka rmem_alloc) to
pace writers, and let user run without being slow down too much.

Introduce a sk_rcvqueues_full() helper, to avoid taking socket lock in
stress situations.

Under huge stress from a multiqueue/RPS enabled NIC, a single flow udp
receiver can now process ~200.000 pps (instead of ~100 pps before the
patch) on a 8 core machine.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>