Revert "ipv4: use skb coalescing in defragmentation"

This reverts commit 3cc4949269e01f39443d0fcfffb5bc6b47878d45.

There is nothing wrong with coalescing during defragmentation, it
reduces truesize overhead and simplifies things for the receiving
socket (no fraglist walk needed).

However, it also destroys geometry of the original fragments.
While that doesn't cause any breakage (we make sure to not exceed largest
original size) ip_do_fragment contains a 'fastpath' that takes advantage
of a present frag list and results in fragments that (in most cases)
match what was received.

In case its needed the coalescing could be done later, when we're sure
the skb is not forwarded.  But discussion during NFWS resulted in
'lets just remove this for now'.

Orabug: 25819103

Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 14fe22e334623e451b5592193415c644005461ea)

Acked-by: Rama Nichanamatlu <rama.nichanamatlu@oracle.com>
Signed-off-by: Venkat Venkatsubra <venkat.x.venkatsubra@oracle.com>
Conflicts:
	net/ipv4/ip_fragment.c

diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 7440d2ee712cd6d0cb97b401599f0ef487431c03..ca4acede5776048f6ac52e738afaaa5357aabb01 100644 (file)
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -508,7 +508,6 @@ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
        int len;
        int ihlen;
        int err;
-       int sum_truesize;
        u8 ecn;
 
        ipq_kill(qp);
@@ -576,32 +575,19 @@ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
                add_frag_mem_limit(qp->q.net, clone->truesize);
        }
 
+       skb_shinfo(head)->frag_list = head->next;
        skb_push(head, head->data - skb_network_header(head));
 
-       sum_truesize = head->truesize;
-       for (fp = head->next; fp;) {
-               bool headstolen;
-               int delta;
-               struct sk_buff *next = fp->next;
-
-               sum_truesize += fp->truesize;
+       for (fp=head->next; fp; fp = fp->next) {
+               head->data_len += fp->len;
+               head->len += fp->len;
                if (head->ip_summed != fp->ip_summed)
                        head->ip_summed = CHECKSUM_NONE;
                else if (head->ip_summed == CHECKSUM_COMPLETE)
                        head->csum = csum_add(head->csum, fp->csum);
-
-               if (skb_try_coalesce(head, fp, &headstolen, &delta)) {
-                       kfree_skb_partial(fp, headstolen);
-               } else {
-                       if (!skb_shinfo(head)->frag_list)
-                               skb_shinfo(head)->frag_list = fp;
-                       head->data_len += fp->len;
-                       head->len += fp->len;
-                       head->truesize += fp->truesize;
-               }
-               fp = next;
+               head->truesize += fp->truesize;
        }
-       sub_frag_mem_limit(qp->q.net, sum_truesize);
+       sub_frag_mem_limit(qp->q.net, head->truesize);
 
        head->next = NULL;
        head->dev = dev;