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Commit f35d9d8a authored by Rusty Russell's avatar Rusty Russell
Browse files

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



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: default avatarRusty Russell <rusty@rustcorp.com.au>
Acked-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9135f190

drivers/net/virtio_net.c

+1 −10
Original line number Diff line number Diff line
@@ -83,18 +83,9 @@ static void receive_skb(struct net_device *dev, struct sk_buff *skb, 


	if (hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {

		pr_debug("Needs csum!\n");

		skb->ip_summed = CHECKSUM_PARTIAL;

		skb->csum_start = hdr->csum_start;

		skb->csum_offset = hdr->csum_offset;

		if (skb->csum_start > skb->len - 2

		    || skb->csum_offset > skb->len - 2) {

			if (net_ratelimit())

				printk(KERN_WARNING "%s: csum=%u/%u len=%u\n",

				       dev->name, skb->csum_start,

				       skb->csum_offset, skb->len);

		if (!skb_partial_csum_set(skb,hdr->csum_start,hdr->csum_offset))

			goto frame_err;

	}

	}



	if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {

		pr_debug("GSO!\n");

include/linux/skbuff.h

+1 −0
Original line number Diff line number Diff line
@@ -1810,5 +1810,6 @@ static inline void skb_forward_csum(struct sk_buff *skb) 
		skb->ip_summed = CHECKSUM_NONE;

}



bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off);

#endif	/* __KERNEL__ */

#endif	/* _LINUX_SKBUFF_H */

net/core/skbuff.c

+29 −0
Original line number Diff line number Diff line
@@ -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);