[PATCH] ipv6: Don't depend on per socket memory for neighbour discovery messages

[PATCH] ipv6: Don't depend on per socket memory for neighbour discovery messages

[Thomas Graf]

Allocating skbs when sending out neighbour discovery messages
currently uses sock_alloc_send_skb() based on a per net namespace
socket and thus share a socket wmem buffer space.

If a netdevice is temporarily unable to transmit due to carrier
loss or for other reasons, the queued up ndisc messages will cosnume
all of the wmem space and will thus prevent from any more skbs to
be allocated even for netdevices that are able to transmit packets.

The number of neighbour discovery messages sent is very limited,
simply use alloc_skb() and don't depend on any socket wmem space any
longer.

This patch has orginally been posted by Eric Dumazet in a modified
form.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
---
 net/ipv6/ndisc.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index b3b5730..bf028a7 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -370,16 +370,12 @@ static struct sk_buff *ndisc_alloc_skb(struct net_device *dev,
 {
 	int hlen = LL_RESERVED_SPACE(dev);
 	int tlen = dev->needed_tailroom;
-	struct sock *sk = dev_net(dev)->ipv6.ndisc_sk;
 	struct sk_buff *skb;
-	int err;
 
-	skb = sock_alloc_send_skb(sk,
-				  hlen + sizeof(struct ipv6hdr) + len + tlen,
-				  1, &err);
+	skb = alloc_skb(hlen + sizeof(struct ipv6hdr) + len + tlen, GFP_ATOMIC);
 	if (!skb) {
-		ND_PRINTK(0, err, "ndisc: %s failed to allocate an skb, err=%d\n",
-			  __func__, err);
+		ND_PRINTK(0, err, "ndisc: %s failed to allocate an skb\n",
+			  __func__);
 		return NULL;
 	}
 
-- 
1.8.3.1

Re: [PATCH] ipv6: Don't depend on per socket memory for neighbour discovery messages

[Hannes Frederic Sowa]

On Wed, Aug 28, 2013 at 01:07:25AM +0200, Thomas Graf wrote:
> Allocating skbs when sending out neighbour discovery messages
> currently uses sock_alloc_send_skb() based on a per net namespace
> socket and thus share a socket wmem buffer space.
> 
> If a netdevice is temporarily unable to transmit due to carrier
> loss or for other reasons, the queued up ndisc messages will cosnume
> all of the wmem space and will thus prevent from any more skbs to
> be allocated even for netdevices that are able to transmit packets.
> 
> The number of neighbour discovery messages sent is very limited,
> simply use alloc_skb() and don't depend on any socket wmem space any
> longer.
> 
> This patch has orginally been posted by Eric Dumazet in a modified
> form.
> 
> Signed-off-by: Thomas Graf <tgraf@suug.ch>
> Cc: Eric Dumazet <eric.dumazet@gmail.com>

Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>

This fixes a real bug (I also had this issue) and thus would propose it
for stable, too.

Thanks!

Re: [PATCH] ipv6: Don't depend on per socket memory for neighbour discovery messages

[Eric Dumazet]

On Wed, 2013-08-28 at 01:07 +0200, Thomas Graf wrote:
> Allocating skbs when sending out neighbour discovery messages
> currently uses sock_alloc_send_skb() based on a per net namespace
> socket and thus share a socket wmem buffer space.
> 
> If a netdevice is temporarily unable to transmit due to carrier
> loss or for other reasons, the queued up ndisc messages will cosnume
> all of the wmem space and will thus prevent from any more skbs to
> be allocated even for netdevices that are able to transmit packets.
> 
> The number of neighbour discovery messages sent is very limited,
> simply use alloc_skb() and don't depend on any socket wmem space any
> longer.
> 
> This patch has orginally been posted by Eric Dumazet in a modified
> form.
> 
> Signed-off-by: Thomas Graf <tgraf@suug.ch>
> Cc: Eric Dumazet <eric.dumazet@gmail.com>
> ---

Seems good to me, thanks !

Acked-by: Eric Dumazet <edumazet@google.com>