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>

1 files changed, 4 insertions, 6 deletions

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 250cb5e1af48..3294f547c481 100644
--- 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;