igmp: avoid two atomic ops in igmp_rcv()

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>

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 250cb5e..3294f54 100644 (file)
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -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:
@@ -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);
@@ -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:
@@ -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;