Revert "ipv4: use skb coalescing in defragmentation" (14fe22e3) · Commits · 戴 / test

This reverts commit . 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'. 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>

net/ipv4/ip_fragment.c

+6 −20

Original line number	Diff line number	Diff line
		@@ -522,7 +522,6 @@ 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);
		@@ -590,32 +589,19 @@ static int ip_frag_reasm(struct ipq qp, struct sk_buff prev,
		add_frag_mem_limit(&qp->q, 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;
		}
		sub_frag_mem_limit(&qp->q, sum_truesize);
		sub_frag_mem_limit(&qp->q, head->truesize);

		head->next = NULL;
		head->dev = dev;

Admin message