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igmp: avoid two atomic ops in igmp_rcv()
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in_dev_get() -> __in_dev_get_rcu() in a rcu protected function.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Eric Dumazet authored and David S. Miller committed Jun 8, 2010
1 parent 6601850 commit 9a57a9d
Showing 1 changed file with 4 additions and 6 deletions.
10 changes: 4 additions & 6 deletions net/ipv4/igmp.c
Original file line number Diff line number Diff line change
Expand Up @@ -916,18 +916,19 @@ static void igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
read_unlock(&in_dev->mc_list_lock);
}

/* called in rcu_read_lock() section */
int igmp_rcv(struct sk_buff *skb)
{
/* This basically follows the spec line by line -- see RFC1112 */
struct igmphdr *ih;
struct in_device *in_dev = in_dev_get(skb->dev);
struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
int len = skb->len;

if (in_dev == NULL)
goto drop;

if (!pskb_may_pull(skb, sizeof(struct igmphdr)))
goto drop_ref;
goto drop;

switch (skb->ip_summed) {
case CHECKSUM_COMPLETE:
Expand All @@ -937,7 +938,7 @@ int igmp_rcv(struct sk_buff *skb)
case CHECKSUM_NONE:
skb->csum = 0;
if (__skb_checksum_complete(skb))
goto drop_ref;
goto drop;
}

ih = igmp_hdr(skb);
Expand All @@ -957,7 +958,6 @@ int igmp_rcv(struct sk_buff *skb)
break;
case IGMP_PIM:
#ifdef CONFIG_IP_PIMSM_V1
in_dev_put(in_dev);
return pim_rcv_v1(skb);
#endif
case IGMPV3_HOST_MEMBERSHIP_REPORT:
Expand All @@ -971,8 +971,6 @@ int igmp_rcv(struct sk_buff *skb)
break;
}

drop_ref:
in_dev_put(in_dev);
drop:
kfree_skb(skb);
return 0;
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