netdev - [PATCH net-next 1/2] net: ipv4: fix list processing on L3 slave devices

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Date:   Thu, 5 Jul 2018 15:47:39 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     <davem@...emloft.net>
CC:     <netdev@...r.kernel.org>
Subject: [PATCH net-next 1/2] net: ipv4: fix list processing on L3 slave
 devices

If we have an L3 master device, l3mdev_ip_rcv() will steal the skb, but
 we were returning NET_RX_SUCCESS from ip_rcv_finish_core() which meant
 that ip_list_rcv_finish() would keep it on the list.  Instead let's
 move the l3mdev_ip_rcv() call into the caller, so that our response to
 a steal can be different in the single packet path (return
 NET_RX_SUCCESS) and the list path (forget this packet and continue).

Fixes: 5fa12739a53d net: ipv4: listify ip_rcv_finish
Signed-off-by: Edward Cree <ecree@...arflare.com>
---
 net/ipv4/ip_input.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index 14ba628b2761..1a3b6f32b1c9 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -316,13 +316,6 @@ static int ip_rcv_finish_core(struct net *net, struct sock *sk,
 	struct rtable *rt;
 	int err;
 
-	/* if ingress device is enslaved to an L3 master device pass the
-	 * skb to its handler for processing
-	 */
-	skb = l3mdev_ip_rcv(skb);
-	if (!skb)
-		return NET_RX_SUCCESS;
-
 	if (net->ipv4.sysctl_ip_early_demux &&
 	    !skb_dst(skb) &&
 	    !skb->sk &&
@@ -408,8 +401,16 @@ static int ip_rcv_finish_core(struct net *net, struct sock *sk,
 
 static int ip_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
-	int ret = ip_rcv_finish_core(net, sk, skb);
+	int ret;
+
+	/* if ingress device is enslaved to an L3 master device pass the
+	 * skb to its handler for processing
+	 */
+	skb = l3mdev_ip_rcv(skb);
+	if (!skb)
+		return NET_RX_SUCCESS;
 
+	ret = ip_rcv_finish_core(net, sk, skb);
 	if (ret != NET_RX_DROP)
 		ret = dst_input(skb);
 	return ret;
@@ -545,6 +546,12 @@ static void ip_list_rcv_finish(struct net *net, struct sock *sk,
 		struct dst_entry *dst;
 
 		list_del(&skb->list);
+		/* if ingress device is enslaved to an L3 master device pass the
+		 * skb to its handler for processing
+		 */
+		skb = l3mdev_ip_rcv(skb);
+		if (!skb)
+			continue;
 		if (ip_rcv_finish_core(net, sk, skb) == NET_RX_DROP)
 			continue;