tcp: gso: fix truesize tracking (0d08c42c) · Commits · 戴 / test

commit ("tcp: gso: do not generate out of order packets") had an heuristic that can trigger a warning in skb_try_coalesce(), because skb->truesize of the gso segments were exactly set to mss. This breaks the requirement that skb->truesize >= skb->len + truesizeof(struct sk_buff); It can trivially be reproduced by : ifconfig lo mtu 1500 ethtool -K lo tso off netperf As the skbs are looped into the TCP networking stack, skb_try_coalesce() warns us of these skb under-estimating their truesize. Signed-off-by:

Eric Dumazet <edumazet@google.com> Reported-by:

Alexei Starovoitov <ast@plumgrid.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/ipv4/tcp_offload.c

+5 −8

Original line number	Diff line number	Diff line
		@@ -18,6 +18,7 @@ struct sk_buff tcp_tso_segment(struct sk_buff skb,
		netdev_features_t features)
		{
		struct sk_buff *segs = ERR_PTR(-EINVAL);
		unsigned int sum_truesize = 0;
		struct tcphdr *th;
		unsigned int thlen;
		unsigned int seq;
		@@ -102,13 +103,7 @@ struct sk_buff tcp_tso_segment(struct sk_buff skb,
		if (copy_destructor) {
		skb->destructor = gso_skb->destructor;
		skb->sk = gso_skb->sk;
		/* {tcp\|sock}_wfree() use exact truesize accounting :
		* sum(skb->truesize) MUST be exactly be gso_skb->truesize
		* So we account mss bytes of 'true size' for each segment.
		* The last segment will contain the remaining.
		*/
		skb->truesize = mss;
		gso_skb->truesize -= mss;
		sum_truesize += skb->truesize;
		}
		skb = skb->next;
		th = tcp_hdr(skb);
		@@ -125,7 +120,9 @@ struct sk_buff tcp_tso_segment(struct sk_buff skb,
		if (copy_destructor) {
		swap(gso_skb->sk, skb->sk);
		swap(gso_skb->destructor, skb->destructor);
		swap(gso_skb->truesize, skb->truesize);
		sum_truesize += skb->truesize;
		atomic_add(sum_truesize - gso_skb->truesize,
		&skb->sk->sk_wmem_alloc);
		}

		delta = htonl(oldlen + (skb_tail_pointer(skb) -

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