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net: generalize skb_segment()

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While implementing GSO/TSO support for IPIP, I found skb_segment()
was assuming network header was immediately following mac header.

Its not really true in the case inet_gso_segment() is stacked :
By the time tcp_gso_segment() is called, network header points
to the inner IP header.

Let's instead assume nothing and pick the current offsets found in
original skb, we have skb_headers_offset_update() helper for that.

Also move the csum_start update inside skb_headers_offset_update()

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2013-10-19 11:42:54 -07:00 committed by David S. Miller
parent b917eb155c
commit 030737bcc3
1 changed files with 5 additions and 17 deletions
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22
net/core/skbuff.c
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@ -903,6 +903,9 @@ EXPORT_SYMBOL(skb_clone);
static void skb_headers_offset_update(struct sk_buff *skb, int off)
{
/* Only adjust this if it actually is csum_start rather than csum */
if (skb->ip_summed == CHECKSUM_PARTIAL)
skb->csum_start += off;
/* {transport,network,mac}_header and tail are relative to skb->head */
skb->transport_header += off;
skb->network_header += off;
@ -1109,9 +1112,6 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
#endif
skb->tail += off;
skb_headers_offset_update(skb, nhead);
/* Only adjust this if it actually is csum_start rather than csum */
if (skb->ip_summed == CHECKSUM_PARTIAL)
skb->csum_start += nhead;
skb->cloned = 0;
skb->hdr_len = 0;
skb->nohdr = 0;
@ -1176,7 +1176,6 @@ struct sk_buff *skb_copy_expand(const struct sk_buff *skb,
NUMA_NO_NODE);
int oldheadroom = skb_headroom(skb);
int head_copy_len, head_copy_off;
int off;
if (!n)
return NULL;
@ -1200,11 +1199,7 @@ struct sk_buff *skb_copy_expand(const struct sk_buff *skb,
copy_skb_header(n, skb);
off = newheadroom - oldheadroom;
if (n->ip_summed == CHECKSUM_PARTIAL)
n->csum_start += off;
skb_headers_offset_update(n, off);
skb_headers_offset_update(n, newheadroom - oldheadroom);
return n;
}
@ -2837,14 +2832,7 @@ struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features)
__copy_skb_header(nskb, skb);
nskb->mac_len = skb->mac_len;
/* nskb and skb might have different headroom */
if (nskb->ip_summed == CHECKSUM_PARTIAL)
nskb->csum_start += skb_headroom(nskb) - headroom;
skb_reset_mac_header(nskb);
skb_set_network_header(nskb, skb->mac_len);
nskb->transport_header = (nskb->network_header +
skb_network_header_len(skb));
skb_headers_offset_update(nskb, skb_headroom(nskb) - headroom);
skb_copy_from_linear_data_offset(skb, -tnl_hlen,
nskb->data - tnl_hlen,