From: Soheil Hassas Yeganeh <soh...@google.com>
Only when ICMP packets are enqueued onto the error queue,
sk_err is also set. Before f5f99309fa74 (sock: do not set sk_err
in sock_dequeue_err_skb), a subsequent error queue read
would set sk_err to the next error on the queue, or 0 if empty.
As no error types other than ICMP set this field, sk_err should
not be modified upon dequeuing them.
Only for ICMP errors, reset the (racy) sk_err. Some applications,
like traceroute, rely on it and go into a futile busy POLLERR
loop otherwise.
In principle, sk_err has to be set while an ICMP error is queued.
Testing is_icmp_err_skb(skb_next) approximates this without
requiring a full queue walk. Applications that receive both ICMP
and other errors cannot rely on this legacy behavior, as other
errors do not set sk_err in the first place.
Fixes: f5f99309fa74 (sock: do not set sk_err in sock_dequeue_err_skb)
Signed-off-by: Soheil Hassas Yeganeh <soh...@google.com>
Signed-off-by: Willem de Bruijn <will...@google.com>
---
net/core/skbuff.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index d1d1a5a..8dad391 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3714,20 +3714,29 @@ int sock_queue_err_skb(struct sock *sk, struct sk_buff
*skb)
}
EXPORT_SYMBOL(sock_queue_err_skb);
+static bool is_icmp_err_skb(const struct sk_buff *skb)
+{
+ return skb && (SKB_EXT_ERR(skb)->ee.ee_origin == SO_EE_ORIGIN_ICMP ||
+ SKB_EXT_ERR(skb)->ee.ee_origin == SO_EE_ORIGIN_ICMP6);
+}
+
struct sk_buff *sock_dequeue_err_skb(struct sock *sk)
{
struct sk_buff_head *q = &sk->sk_error_queue;
- struct sk_buff *skb, *skb_next;
+ struct sk_buff *skb, *skb_next = NULL;
+ bool icmp_next = false;
unsigned long flags;
- int err = 0;
spin_lock_irqsave(&q->lock, flags);
skb = __skb_dequeue(q);
if (skb && (skb_next = skb_peek(q)))
- err = SKB_EXT_ERR(skb_next)->ee.ee_errno;
+ icmp_next = is_icmp_err_skb(skb_next);
spin_unlock_irqrestore(&q->lock, flags);
- if (err)
+ if (is_icmp_err_skb(skb) && !icmp_next)
+ sk->sk_err = 0;
+
+ if (skb_next)
sk->sk_error_report(sk);
return skb;
--
2.8.0.rc3.226.g39d4020
