From 7433819a1eefd4e74711fffd6d54e30a644ef240 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 31 May 2012 21:00:26 +0000 Subject: [PATCH] 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 Cc: Hans Schillstrom Cc: Jesper Dangaard Brouer Cc: Neal Cardwell Cc: Tom Herbert Signed-off-by: David S. Miller --- net/ipv4/inet_connection_sock.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) 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)); -- 2.30.2