vlan: allow nested vlan_do_receive()

commit 2425717b27eb (net: allow vlan traffic to be received under bond)
broke ARP processing on vlan on top of bonding.

       +-------+
eth0 --| bond0 |---bond0.103
eth1 --|       |
       +-------+

52870.115435: skb_gro_reset_offset <-napi_gro_receive
52870.115435: dev_gro_receive <-napi_gro_receive
52870.115435: napi_skb_finish <-napi_gro_receive
52870.115435: netif_receive_skb <-napi_skb_finish
52870.115435: get_rps_cpu <-netif_receive_skb
52870.115435: __netif_receive_skb <-netif_receive_skb
52870.115436: vlan_do_receive <-__netif_receive_skb
52870.115436: bond_handle_frame <-__netif_receive_skb
52870.115436: vlan_do_receive <-__netif_receive_skb
52870.115436: arp_rcv <-__netif_receive_skb
52870.115436: kfree_skb <-arp_rcv

Packet is dropped in arp_rcv() because its pkt_type was set to
PACKET_OTHERHOST in the first vlan_do_receive() call, since no eth0.103
exists.

We really need to change pkt_type only if no more rx_handler is about to
be called for the packet.

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

2 files changed, 7 insertions, 4 deletions

diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c
index f1f2f7bb666..163397f1fd5 100644
--- a/net/8021q/vlan_core.c
+++ b/net/8021q/vlan_core.c
@@ -4,7 +4,7 @@
 #include <linux/netpoll.h>
 #include "vlan.h"
 
-bool vlan_do_receive(struct sk_buff **skbp)
+bool vlan_do_receive(struct sk_buff **skbp, bool last_handler)
 {
         struct sk_buff *skb = *skbp;
         u16 vlan_id = skb->vlan_tci & VLAN_VID_MASK;
@@ -13,7 +13,10 @@ bool vlan_do_receive(struct sk_buff **skbp)
 
         vlan_dev = vlan_find_dev(skb->dev, vlan_id);
         if (!vlan_dev) {
-                if (vlan_id)
+                /* Only the last call to vlan_do_receive() should change
+                 * pkt_type to PACKET_OTHERHOST
+                 */
+                if (vlan_id && last_handler)
                         skb->pkt_type = PACKET_OTHERHOST;
                 return false;
         }
diff --git a/net/core/dev.c b/net/core/dev.c
index edcf019c056..6ba50a1e404 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3283,18 +3283,18 @@ another_round:
 ncls:
 #endif
 
+        rx_handler = rcu_dereference(skb->dev->rx_handler);
         if (vlan_tx_tag_present(skb)) {
                 if (pt_prev) {
                         ret = deliver_skb(skb, pt_prev, orig_dev);
                         pt_prev = NULL;
                 }
-                if (vlan_do_receive(&skb))
+                if (vlan_do_receive(&skb, !rx_handler))
                         goto another_round;
                 else if (unlikely(!skb))
                         goto out;
         }
 
-        rx_handler = rcu_dereference(skb->dev->rx_handler);
         if (rx_handler) {
                 if (pt_prev) {
                         ret = deliver_skb(skb, pt_prev, orig_dev);