igmp: refine skb allocations

IGMP allocates MTU sized skbs. This may fail for large MTU (order-2
allocations), so add a fallback to try lower sizes.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 4 deletions

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 50f6bc1a002a..e0e77e297de3 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -300,6 +300,8 @@ igmp_scount(struct ip_mc_list *pmc, int type, int gdeleted, int sdeleted)
         return scount;
 }
 
+#define igmp_skb_size(skb) (*(unsigned int *)((skb)->cb))
+
 static struct sk_buff *igmpv3_newpack(struct net_device *dev, int size)
 {
         struct sk_buff *skb;
@@ -308,9 +310,16 @@ static struct sk_buff *igmpv3_newpack(struct net_device *dev, int size)
         struct igmpv3_report *pig;
         struct net *net = dev_net(dev);
 
-        skb = alloc_skb(size + LL_ALLOCATED_SPACE(dev), GFP_ATOMIC);
-        if (skb == NULL)
-                return NULL;
+        while (1) {
+                skb = alloc_skb(size + LL_ALLOCATED_SPACE(dev),
+                                GFP_ATOMIC | __GFP_NOWARN);
+                if (skb)
+                        break;
+                size >>= 1;
+                if (size < 256)
+                        return NULL;
+        }
+        igmp_skb_size(skb) = size;
 
         {
                 struct flowi fl = { .oif = dev->ifindex,
@@ -399,7 +408,7 @@ static struct sk_buff *add_grhead(struct sk_buff *skb, struct ip_mc_list *pmc,
         return skb;
 }
 
-#define AVAILABLE(skb) ((skb) ? ((skb)->dev ? (skb)->dev->mtu - (skb)->len : \
+#define AVAILABLE(skb) ((skb) ? ((skb)->dev ? igmp_skb_size(skb) - (skb)->len : \
         skb_tailroom(skb)) : 0)
 
 static struct sk_buff *add_grec(struct sk_buff *skb, struct ip_mc_list *pmc,