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Commit 43170c4e authored by Ilan Tayari's avatar Ilan Tayari Committed by David S. Miller
Browse files

gso: Validate assumption of frag_list segementation 



Commit 07b26c94 ("gso: Support partial splitting at the frag_list
pointer") assumes that all SKBs in a frag_list (except maybe the last
one) contain the same amount of GSO payload.

This assumption is not always correct, resulting in the following
warning message in the log:
    skb_segment: too many frags

For example, mlx5 driver in Striding RQ mode creates some RX SKBs with
one frag, and some with 2 frags.
After GRO, the frag_list SKBs end up having different amounts of payload.
If this frag_list SKB is then forwarded, the aforementioned assumption
is violated.

Validate the assumption, and fall back to software GSO if it not true.

Change-Id: Ia03983f4a47b6534dd987d7a2aad96d54d46d212
Fixes: 07b26c94 ("gso: Support partial splitting at the frag_list pointer")
Signed-off-by: default avatarIlan Tayari <ilant@mellanox.com>
Signed-off-by: default avatarIlya Lesokhin <ilyal@mellanox.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 918b7024

net/core/skbuff.c

+14 −4
Original line number Diff line number Diff line
@@ -3082,22 +3082,32 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb, 
	if (sg && csum && (mss != GSO_BY_FRAGS))  {

		if (!(features & NETIF_F_GSO_PARTIAL)) {

			struct sk_buff *iter;

			unsigned int frag_len;



			if (!list_skb ||

			    !net_gso_ok(features, skb_shinfo(head_skb)->gso_type))

				goto normal;



			/* Split the buffer at the frag_list pointer.

			 * This is based on the assumption that all

			 * buffers in the chain excluding the last

			 * containing the same amount of data.

			/* If we get here then all the required

			 * GSO features except frag_list are supported.

			 * Try to split the SKB to multiple GSO SKBs

			 * with no frag_list.

			 * Currently we can do that only when the buffers don't

			 * have a linear part and all the buffers except

			 * the last are of the same length.

			 */

			frag_len = list_skb->len;

			skb_walk_frags(head_skb, iter) {

				if (frag_len != iter->len && iter->next)

					goto normal;

				if (skb_headlen(iter))

					goto normal;



				len -= iter->len;

			}



			if (len != frag_len)

				goto normal;

		}



		/* GSO partial only requires that we trim off any excess that