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 <[e-mail]>
Signed-off-by: Eric Dumazet <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/macvlan.c

···
 
 	port = macvlan_port_get_rcu(skb->dev);
 	if (is_multicast_ether_addr(eth->h_dest)) {
+		skb = ip_check_defrag(skb, IP_DEFRAG_MACVLAN);
+		if (!skb)
+			return RX_HANDLER_CONSUMED;
 		src = macvlan_hash_lookup(port, eth->h_source);
 		if (!src)
 			/* frame comes from an external address */

include/net/ip.h

···
 	IP_DEFRAG_VS_OUT,
 	IP_DEFRAG_VS_FWD,
 	IP_DEFRAG_AF_PACKET,
+	IP_DEFRAG_MACVLAN,
 };
 
 int ip_defrag(struct sk_buff *skb, u32 user);
+#ifdef CONFIG_INET
+struct sk_buff *ip_check_defrag(struct sk_buff *skb, u32 user);
+#else
+static inline struct sk_buff *ip_check_defrag(struct sk_buff *skb, u32 user)
+{
+	return skb;
+}
+#endif
 int ip_frag_mem(struct net *net);
 int ip_frag_nqueues(struct net *net);
 

net/ipv4/ip_fragment.c

···
 }
 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;
 

net/packet/af_packet.c

···
 	return f->arr[cpu % num];
 }
 
-static struct sk_buff *fanout_check_defrag(struct sk_buff *skb)
-{
-#ifdef CONFIG_INET
-	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, IP_DEFRAG_AF_PACKET))
-				return NULL;
-			skb->rxhash = 0;
-		}
-	}
-#endif
-	return skb;
-}
-
 static int packet_rcv_fanout(struct sk_buff *skb, struct net_device *dev,
 			     struct packet_type *pt, struct net_device *orig_dev)
 {
···
 	case PACKET_FANOUT_HASH:
 	default:
 		if (f->defrag) {
-			skb = fanout_check_defrag(skb);
+			skb = ip_check_defrag(skb, IP_DEFRAG_AF_PACKET);
 			if (!skb)
 				return 0;
 		}