macvlan: handle fragmented multicast frames

Fragmented multicast frames are delivered to a single macvlan port,
because ip defrag logic considers other samples are redundant.

Implement a defrag step before trying to send the multicast frame.

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

1 files changed, 36 insertions, 0 deletions

diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 0e0ab98abc6f..763589ad673d 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -682,6 +682,42 @@ int ip_defrag(struct sk_buff *skb, u32 user)
 }
 EXPORT_SYMBOL(ip_defrag);
 
+struct sk_buff *ip_check_defrag(struct sk_buff *skb, u32 user)
+{
+        const struct iphdr *iph;
+        u32 len;
+
+        if (skb->protocol != htons(ETH_P_IP))
+                return skb;
+
+        if (!pskb_may_pull(skb, sizeof(struct iphdr)))
+                return skb;
+
+        iph = ip_hdr(skb);
+        if (iph->ihl < 5 || iph->version != 4)
+                return skb;
+        if (!pskb_may_pull(skb, iph->ihl*4))
+                return skb;
+        iph = ip_hdr(skb);
+        len = ntohs(iph->tot_len);
+        if (skb->len < len || len < (iph->ihl * 4))
+                return skb;
+
+        if (ip_is_fragment(ip_hdr(skb))) {
+                skb = skb_share_check(skb, GFP_ATOMIC);
+                if (skb) {
+                        if (pskb_trim_rcsum(skb, len))
+                                return skb;
+                        memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
+                        if (ip_defrag(skb, user))
+                                return NULL;
+                        skb->rxhash = 0;
+                }
+        }
+        return skb;
+}
+EXPORT_SYMBOL(ip_check_defrag);
+
 #ifdef CONFIG_SYSCTL
 static int zero;