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Commit ab6e3feb authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: No dst refcounting in ip_queue_xmit() 



TCP outgoing packets can avoid two atomic ops, and dirtying
of previously higly contended cache line using new refdst
infrastructure.

Note 1: loopback device excluded because of !IFF_XMIT_DST_RELEASE
Note 2: UDP packets dsts are built before ip_queue_xmit().

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4a94445c

net/ipv4/ip_output.c

+7 −2
Original line number Diff line number Diff line
@@ -318,10 +318,12 @@ int ip_queue_xmit(struct sk_buff *skb) 
	struct ip_options *opt = inet->opt;

	struct rtable *rt;

	struct iphdr *iph;

	int res;



	/* Skip all of this if the packet is already routed,

	 * f.e. by something like SCTP.

	 */

	rcu_read_lock();

	rt = skb_rtable(skb);

	if (rt != NULL)

		goto packet_routed;
@@ -359,7 +361,7 @@ int ip_queue_xmit(struct sk_buff *skb) 
		}

		sk_setup_caps(sk, &rt->u.dst);

	}

	skb_dst_set(skb, dst_clone(&rt->u.dst));

	skb_dst_set_noref(skb, &rt->u.dst);



packet_routed:

	if (opt && opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
@@ -391,9 +393,12 @@ int ip_queue_xmit(struct sk_buff *skb) 
	skb->priority = sk->sk_priority;

	skb->mark = sk->sk_mark;



	return ip_local_out(skb);

	res = ip_local_out(skb);

	rcu_read_unlock();

	return res;



no_route:

	rcu_read_unlock();

	IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);

	kfree_skb(skb);

	return -EHOSTUNREACH;