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authorEric Dumazet <edumazet@google.com>2012-05-31 21:00:26 +0000
committerDavid S. Miller <davem@davemloft.net>2012-06-01 14:22:11 -0400
commit7433819a1eefd4e74711fffd6d54e30a644ef240 (patch)
tree62ced5e44f740d4d641d7719ae4a4ac0c91f4748
parent8139cp/8139too: terminate the eeprom access with the right opmode (diff)
downloadlinux-dev-7433819a1eefd4e74711fffd6d54e30a644ef240.tar.xz
linux-dev-7433819a1eefd4e74711fffd6d54e30a644ef240.zip
tcp: do not create inetpeer on SYNACK message
Another problem on SYNFLOOD/DDOS attack is the inetpeer cache getting larger and larger, using lots of memory and cpu time. tcp_v4_send_synack() ->inet_csk_route_req() ->ip_route_output_flow() ->rt_set_nexthop() ->rt_init_metrics() ->inet_getpeer( create = true) This is a side effect of commit a4daad6b09230 (net: Pre-COW metrics for TCP) added in 2.6.39 Possible solution : Instruct inet_csk_route_req() to remove FLOWI_FLAG_PRECOW_METRICS Before patch : # grep peer /proc/slabinfo inet_peer_cache 4175430 4175430 192 42 2 : tunables 0 0 0 : slabdata 99415 99415 0 Samples: 41K of event 'cycles', Event count (approx.): 30716565122 + 20,24% ksoftirqd/0 [kernel.kallsyms] [k] inet_getpeer + 8,19% ksoftirqd/0 [kernel.kallsyms] [k] peer_avl_rebalance.isra.1 + 4,81% ksoftirqd/0 [kernel.kallsyms] [k] sha_transform + 3,64% ksoftirqd/0 [kernel.kallsyms] [k] fib_table_lookup + 2,36% ksoftirqd/0 [ixgbe] [k] ixgbe_poll + 2,16% ksoftirqd/0 [kernel.kallsyms] [k] __ip_route_output_key + 2,11% ksoftirqd/0 [kernel.kallsyms] [k] kernel_map_pages + 2,11% ksoftirqd/0 [kernel.kallsyms] [k] ip_route_input_common + 2,01% ksoftirqd/0 [kernel.kallsyms] [k] __inet_lookup_established + 1,83% ksoftirqd/0 [kernel.kallsyms] [k] md5_transform + 1,75% ksoftirqd/0 [kernel.kallsyms] [k] check_leaf.isra.9 + 1,49% ksoftirqd/0 [kernel.kallsyms] [k] ipt_do_table + 1,46% ksoftirqd/0 [kernel.kallsyms] [k] hrtimer_interrupt + 1,45% ksoftirqd/0 [kernel.kallsyms] [k] kmem_cache_alloc + 1,29% ksoftirqd/0 [kernel.kallsyms] [k] inet_csk_search_req + 1,29% ksoftirqd/0 [kernel.kallsyms] [k] __netif_receive_skb + 1,16% ksoftirqd/0 [kernel.kallsyms] [k] copy_user_generic_string + 1,15% ksoftirqd/0 [kernel.kallsyms] [k] kmem_cache_free + 1,02% ksoftirqd/0 [kernel.kallsyms] [k] tcp_make_synack + 0,93% ksoftirqd/0 [kernel.kallsyms] [k] _raw_spin_lock_bh + 0,87% ksoftirqd/0 [kernel.kallsyms] [k] __call_rcu + 0,84% ksoftirqd/0 [kernel.kallsyms] [k] rt_garbage_collect + 0,84% ksoftirqd/0 [kernel.kallsyms] [k] fib_rules_lookup Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Hans Schillstrom <hans.schillstrom@ericsson.com> Cc: Jesper Dangaard Brouer <brouer@redhat.com> Cc: Neal Cardwell <ncardwell@google.com> Cc: Tom Herbert <therbert@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/ipv4/inet_connection_sock.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 95e61596e605..f9ee7417f6a0 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -377,7 +377,8 @@ struct dst_entry *inet_csk_route_req(struct sock *sk,
flowi4_init_output(fl4, sk->sk_bound_dev_if, sk->sk_mark,
RT_CONN_FLAGS(sk), RT_SCOPE_UNIVERSE,
- sk->sk_protocol, inet_sk_flowi_flags(sk),
+ sk->sk_protocol,
+ inet_sk_flowi_flags(sk) & ~FLOWI_FLAG_PRECOW_METRICS,
(opt && opt->opt.srr) ? opt->opt.faddr : ireq->rmt_addr,
ireq->loc_addr, ireq->rmt_port, inet_sk(sk)->inet_sport);
security_req_classify_flow(req, flowi4_to_flowi(fl4));