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virtio: Implement skb_partial_csum_set, for setting partial csums on untrusted packets.

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Use it in virtio_net (replacing buggy version there), it's also going
to be used by TAP for partial csum support.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Rusty Russell
2008-02-04 23:49:54 -05:00
parent 9135f1901e
commit f35d9d8aae
3 changed files with 31 additions and 10 deletions
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29
net/core/skbuff.c
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@@ -2461,6 +2461,34 @@ int skb_cow_data(struct sk_buff *skb, int tailbits, struct sk_buff **trailer)
return elt;
}
/**
* skb_partial_csum_set - set up and verify partial csum values for packet
* @skb: the skb to set
* @start: the number of bytes after skb->data to start checksumming.
* @off: the offset from start to place the checksum.
*
* For untrusted partially-checksummed packets, we need to make sure the values
* for skb->csum_start and skb->csum_offset are valid so we don't oops.
*
* This function checks and sets those values and skb->ip_summed: if this
* returns false you should drop the packet.
*/
bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off)
{
if (unlikely(start > skb->len - 2) ||
unlikely((int)start + off > skb->len - 2)) {
if (net_ratelimit())
printk(KERN_WARNING
"bad partial csum: csum=%u/%u len=%u\n",
start, off, skb->len);
return false;
}
skb->ip_summed = CHECKSUM_PARTIAL;
skb->csum_start = skb_headroom(skb) + start;
skb->csum_offset = off;
return true;
}
EXPORT_SYMBOL(___pskb_trim);
EXPORT_SYMBOL(__kfree_skb);
EXPORT_SYMBOL(kfree_skb);
@@ -2497,3 +2525,4 @@ EXPORT_SYMBOL(skb_append_datato_frags);
EXPORT_SYMBOL_GPL(skb_to_sgvec);
EXPORT_SYMBOL_GPL(skb_cow_data);
EXPORT_SYMBOL_GPL(skb_partial_csum_set);