From ca55158c6ecb7832a6ad80ac44a14d23bab8cdfc Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 3 Jun 2010 09:03:58 +0000 Subject: [PATCH] rps: tcp: fix rps_sock_flow_table table updates I believe a moderate SYN flood attack can corrupt RFS flow table (rps_sock_flow_table), making RPS/RFS much less effective. Even in a normal situation, server handling short lived sessions suffer from bad steering for the first data packet of a session, if another SYN packet is received for another session. We do following action in tcp_v4_rcv() : sock_rps_save_rxhash(sk, skb->rxhash); We should _not_ do this if sk is a LISTEN socket, as about each packet received on a LISTEN socket has a different rxhash than previous one. -> RPS_NO_CPU markers are spread all over rps_sock_flow_table. Also, it makes sense to protect sk->rxhash field changes with socket lock (We currently can change it even if user thread owns the lock and might use rxhash) This patch moves sock_rps_save_rxhash() to a sock locked section, and only for non LISTEN sockets. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp_ipv4.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 202cf09c4cd4..fe193e53af44 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1555,6 +1555,7 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb) #endif if (sk->sk_state == TCP_ESTABLISHED) { /* Fast path */ + sock_rps_save_rxhash(sk, skb->rxhash); TCP_CHECK_TIMER(sk); if (tcp_rcv_established(sk, skb, tcp_hdr(skb), skb->len)) { rsk = sk; @@ -1579,7 +1580,9 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb) } return 0; } - } + } else + sock_rps_save_rxhash(sk, skb->rxhash); + TCP_CHECK_TIMER(sk); if (tcp_rcv_state_process(sk, skb, tcp_hdr(skb), skb->len)) { @@ -1672,8 +1675,6 @@ process: skb->dev = NULL; - sock_rps_save_rxhash(sk, skb->rxhash); - bh_lock_sock_nested(sk); ret = 0; if (!sock_owned_by_user(sk)) {