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 <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -1555,6 +1555,7 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
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#endif
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if (sk->sk_state == TCP_ESTABLISHED) { /* Fast path */
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sock_rps_save_rxhash(sk, skb->rxhash);
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TCP_CHECK_TIMER(sk);
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if (tcp_rcv_established(sk, skb, tcp_hdr(skb), skb->len)) {
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rsk = sk;
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@ -1579,7 +1580,9 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
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}
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return 0;
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}
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}
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} else
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sock_rps_save_rxhash(sk, skb->rxhash);
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TCP_CHECK_TIMER(sk);
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if (tcp_rcv_state_process(sk, skb, tcp_hdr(skb), skb->len)) {
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@ -1672,8 +1675,6 @@ process:
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skb->dev = NULL;
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sock_rps_save_rxhash(sk, skb->rxhash);
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bh_lock_sock_nested(sk);
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ret = 0;
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if (!sock_owned_by_user(sk)) {
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