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Message-ID: <1495011889.2644.5.camel@redhat.com>
Date: Wed, 17 May 2017 11:04:49 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Andrei Vagin <avagin@...nvz.org>,
"David S. Miller" <davem@...emloft.net>
Cc: netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net-next] net: fix __skb_try_recv_from_queue to return
the old behavior
On Tue, 2017-05-16 at 21:47 -0700, Andrei Vagin wrote:
> This function has to return NULL on a error case, because there is a
> separate error variable.
>
> The offset has to be changed only if skb is returned
>
> Cc: Paolo Abeni <pabeni@...hat.com>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: David S. Miller <davem@...emloft.net>
> Fixes: 65101aeca522 ("net/sock: factor out dequeue/peek with offset cod")
> Signed-off-by: Andrei Vagin <avagin@...nvz.org>
> ---
> net/core/datagram.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/net/core/datagram.c b/net/core/datagram.c
> index a4592b4..bc46118 100644
> --- a/net/core/datagram.c
> +++ b/net/core/datagram.c
> @@ -170,20 +170,21 @@ struct sk_buff *__skb_try_recv_from_queue(struct sock *sk,
> struct sk_buff **last)
> {
> struct sk_buff *skb;
> + int _off = *off;
>
> *last = queue->prev;
> skb_queue_walk(queue, skb) {
> if (flags & MSG_PEEK) {
> - if (*off >= skb->len && (skb->len || *off ||
> + if (_off >= skb->len && (skb->len || _off ||
> skb->peeked)) {
> - *off -= skb->len;
> + _off -= skb->len;
> continue;
> }
> if (!skb->len) {
> skb = skb_set_peeked(skb);
> if (unlikely(IS_ERR(skb))) {
> *err = PTR_ERR(skb);
> - return skb;
> + return NULL;
> }
> }
> *peeked = 1;
> @@ -193,6 +194,7 @@ struct sk_buff *__skb_try_recv_from_queue(struct sock *sk,
> if (destructor)
> destructor(sk, skb);
>
> }
> + *off = _off;
> return skb;
> }
> return NULL;
> @@ -253,8 +255,6 @@ struct sk_buff *__skb_try_recv_datagram(struct sock *sk, unsigned int flags,
>
> *peeked = 0;
> do {
> - int _off = *off;
> -
> /* Again only user level code calls this function, so nothing
> * interrupt level will suddenly eat the receive_queue.
> *
> @@ -263,8 +263,10 @@ struct sk_buff *__skb_try_recv_datagram(struct sock *sk, unsigned int flags,
> */
> spin_lock_irqsave(&queue->lock, cpu_flags);
> skb = __skb_try_recv_from_queue(sk, queue, flags, destructor,
> - peeked, &_off, err, last);
> + peeked, off, &error, last);
> spin_unlock_irqrestore(&queue->lock, cpu_flags);
> + if (error)
> + goto no_packet;
> if (skb)
> return skb;
>
Thank you for catching this so early!
If __skb_try_recv_from_queue() updates the offset if/only if the skb is
returned, than we can also add something like the following ?
(only compile tested, should not bring any functional changes, only
code cleanup)
BTW can you please share some entry pointer/walk-through for the CRIU
tests ? I'd like to try to integrate them in my workflow, thank you!
Paolo
---
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 8ad5862..e65c7ed 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1555,16 +1555,13 @@ struct sk_buff *__skb_recv_udp(struct sock *sk, unsigned int flags,
error = -EAGAIN;
*peeked = 0;
do {
- int _off = *off;
-
spin_lock_bh(&queue->lock);
skb = __skb_try_recv_from_queue(sk, queue, flags,
udp_skb_destructor,
- peeked, &_off, err,
+ peeked, off, err,
&last);
if (skb) {
spin_unlock_bh(&queue->lock);
- *off = _off;
return skb;
}
@@ -1578,20 +1575,17 @@ struct sk_buff *__skb_recv_udp(struct sock *sk, unsigned int flags,
* the sk_receive_queue lock if fwd memory scheduling
* is needed.
*/
- _off = *off;
spin_lock(&sk_queue->lock);
skb_queue_splice_tail_init(sk_queue, queue);
skb = __skb_try_recv_from_queue(sk, queue, flags,
udp_skb_dtor_locked,
- peeked, &_off, err,
+ peeked, off, err,
&last);
spin_unlock(&sk_queue->lock);
spin_unlock_bh(&queue->lock);
- if (skb) {
- *off = _off;
+ if (skb)
return skb;
- }
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