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net: ip: push gso skb forwarding handling down the stack

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Doing the segmentation in the forward path has one major drawback:

When using virtio, we may process gso udp packets coming
from host network stack.  In that case, netfilter POSTROUTING
will see one packet with udp header followed by multiple ip
fragments.

Delay the segmentation and do it after POSTROUTING invocation
to avoid this.

Fixes: fe6cc55f3a ("net: ip, ipv6: handle gso skbs in forwarding path")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Florian Westphal
2014-05-05 15:00:43 +02:00
committed by David S. Miller
parent 418a31561d
commit c7ba65d7b6
2 changed files with 48 additions and 53 deletions
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50
net/ipv4/ip_forward.c
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@@ -56,53 +56,6 @@ static bool ip_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu)
return true;
}
static bool ip_gso_exceeds_dst_mtu(const struct sk_buff *skb)
{
unsigned int mtu;
if (skb->local_df || !skb_is_gso(skb))
return false;
mtu = ip_dst_mtu_maybe_forward(skb_dst(skb), true);
/* if seglen > mtu, do software segmentation for IP fragmentation on
* output. DF bit cannot be set since ip_forward would have sent
* icmp error.
*/
return skb_gso_network_seglen(skb) > mtu;
}
/* called if GSO skb needs to be fragmented on forward */
static int ip_forward_finish_gso(struct sk_buff *skb)
{
struct dst_entry *dst = skb_dst(skb);
netdev_features_t features;
struct sk_buff *segs;
int ret = 0;
features = netif_skb_dev_features(skb, dst->dev);
segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
if (IS_ERR(segs)) {
kfree_skb(skb);
return -ENOMEM;
}
consume_skb(skb);
do {
struct sk_buff *nskb = segs->next;
int err;
segs->next = NULL;
err = dst_output(segs);
if (err && ret == 0)
ret = err;
segs = nskb;
} while (segs);
return ret;
}
static int ip_forward_finish(struct sk_buff *skb)
{
@@ -114,9 +67,6 @@ static int ip_forward_finish(struct sk_buff *skb)
if (unlikely(opt->optlen))
ip_forward_options(skb);
if (ip_gso_exceeds_dst_mtu(skb))
return ip_forward_finish_gso(skb);
return dst_output(skb);
}