gro: fix different skb headrooms
Packets entering GRO might have different headrooms, even for a given flow (because of implementation details in drivers, like copybreak). We cant force drivers to deliver packets with a fixed headroom. 1) fix skb_segment() skb_segment() makes the false assumption headrooms of fragments are same than the head. When CHECKSUM_PARTIAL is used, this can give csum_start errors, and crash later in skb_copy_and_csum_dev() 2) allocate a minimal skb for head of frag_list skb_gro_receive() uses netdev_alloc_skb(headroom + skb_gro_offset(p)) to allocate a fresh skb. This adds NET_SKB_PAD to a padding already provided by netdevice, depending on various things, like copybreak. Use alloc_skb() to allocate an exact padding, to reduce cache line needs: NET_SKB_PAD + NET_IP_ALIGN bugzilla : https://bugzilla.kernel.org/show_bug.cgi?id=16626 Many thanks to Plamen Petrov, testing many debugging patches ! With help of Jarek Poplawski. Reported-by: Plamen Petrov <pvp-lsts@fs.uni-ruse.bg> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> CC: Jarek Poplawski <jarkao2@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -2573,6 +2573,10 @@ struct sk_buff *skb_segment(struct sk_buff *skb, int features)
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__copy_skb_header(nskb, skb);
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nskb->mac_len = skb->mac_len;
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/* nskb and skb might have different headroom */
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if (nskb->ip_summed == CHECKSUM_PARTIAL)
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nskb->csum_start += skb_headroom(nskb) - headroom;
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skb_reset_mac_header(nskb);
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skb_set_network_header(nskb, skb->mac_len);
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nskb->transport_header = (nskb->network_header +
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@ -2702,8 +2706,8 @@ int skb_gro_receive(struct sk_buff **head, struct sk_buff *skb)
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} else if (skb_gro_len(p) != pinfo->gso_size)
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return -E2BIG;
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headroom = skb_headroom(p);
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nskb = netdev_alloc_skb(p->dev, headroom + skb_gro_offset(p));
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headroom = NET_SKB_PAD + NET_IP_ALIGN;
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nskb = alloc_skb(headroom + skb_gro_offset(p), GFP_ATOMIC);
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if (unlikely(!nskb))
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return -ENOMEM;
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