batman-adv: Fix potentially broken skb network header access

The two commits noted below added calls to ip_hdr() and ipv6_hdr(). They
need a correctly set skb network header.

Unfortunately we cannot rely on the device drivers to set it for us.
Therefore setting it in the beginning of the according ndo_start_xmit
handler.

Fixes: 1d8ab8d3c176 ("batman-adv: Modified forwarding behaviour for multicast packets")
Fixes: ab49886e3da7 ("batman-adv: Add IPv4 link-local/IPv6-ll-all-nodes multicast support")
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index c002961da75d..926292d5ffa8 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -202,6 +202,7 @@ static int batadv_interface_tx(struct sk_buff *skb,
         int gw_mode;
         enum batadv_forw_mode forw_mode;
         struct batadv_orig_node *mcast_single_orig = NULL;
+        int network_offset = ETH_HLEN;
 
         if (atomic_read(&bat_priv->mesh_state) != BATADV_MESH_ACTIVE)
                 goto dropped;
@@ -214,14 +215,18 @@ static int batadv_interface_tx(struct sk_buff *skb,
         case ETH_P_8021Q:
                 vhdr = vlan_eth_hdr(skb);
 
-                if (vhdr->h_vlan_encapsulated_proto != ethertype)
+                if (vhdr->h_vlan_encapsulated_proto != ethertype) {
+                        network_offset += VLAN_HLEN;
                         break;
+                }
 
                 /* fall through */
         case ETH_P_BATMAN:
                 goto dropped;
         }
 
+        skb_set_network_header(skb, network_offset);
+
         if (batadv_bla_tx(bat_priv, skb, vid))
                 goto dropped;