From: Menglong Dong <dong.mengl...@zte.com.cn>
'before(*seq, TCP_SKB_CB(skb)->seq) == true' means that one or more
skbs are lost somehow. Once this happen, it seems that it will
never recover automatically. As a result, a warning will be printed
and a '-EAGAIN' will be returned in non-block mode.
As a general suituation, users call 'poll' on a socket and then receive
skbs with 'recv' in non-block mode. This mode will make every
arriving skb of the socket trigger a warning. Plenty of skbs will cause
high rate of kernel log.
Besides, WARN is for indicating kernel bugs only and should not be
user-triggable. Replace it with 'net_warn_ratelimited' here.
Signed-off-by: Menglong Dong <dong.mengl...@zte.com.cn>
---
net/ipv4/tcp.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index b2bc3d7fe9e8..5e38dfd03036 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2093,11 +2093,12 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg,
size_t len, int nonblock,
/* Now that we have two receive queues this
* shouldn't happen.
*/
- if (WARN(before(*seq, TCP_SKB_CB(skb)->seq),
- "TCP recvmsg seq # bug: copied %X, seq %X,
rcvnxt %X, fl %X\n",
- *seq, TCP_SKB_CB(skb)->seq, tp->rcv_nxt,
- flags))
+ if (unlikely(before(*seq, TCP_SKB_CB(skb)->seq))) {
+ net_warn_ratelimited("TCP recvmsg seq # bug:
copied %X, seq %X, rcvnxt %X, fl %X\n",
+ *seq,
TCP_SKB_CB(skb)->seq, tp->rcv_nxt,
+ flags);
break;
+ }
offset = *seq - TCP_SKB_CB(skb)->seq;
if (unlikely(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
@@ -2108,9 +2109,11 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg,
size_t len, int nonblock,
goto found_ok_skb;
if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
goto found_fin_ok;
- WARN(!(flags & MSG_PEEK),
- "TCP recvmsg seq # bug 2: copied %X, seq %X,
rcvnxt %X, fl %X\n",
- *seq, TCP_SKB_CB(skb)->seq, tp->rcv_nxt, flags);
+
+ if (!(flags & MSG_PEEK))
+ net_warn_ratelimited("TCP recvmsg seq # bug 2:
copied %X, seq %X, rcvnxt %X, fl %X\n",
+ *seq,
TCP_SKB_CB(skb)->seq, tp->rcv_nxt,
+ flags);
}
/* Well, if we have backlog, try to process it now yet. */
--
2.25.1
