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>
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 202cf09..fe193e5 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1555,6 +1555,7 @@
#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 @@
}
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 @@
skb->dev = NULL;
- sock_rps_save_rxhash(sk, skb->rxhash);
-
bh_lock_sock_nested(sk);
ret = 0;
if (!sock_owned_by_user(sk)) {