[PATCH batadv v2 1/3] batman-adv: fix TX priority extraction for BATADV_FORW_MCAST

batadv_mcast_forw_mode_by_count() pushs the skb->data for BATADV_FORW_MCAST
forwarding via batadv_mcast_forw_mcsend(). But the
batadv_skb_set_priority() expects the ethernet header directly before
(skb->data + offset). With the moved skb->data, just some random data would
be accessed to get the priority data.

Move the batadv_skb_set_priority() before the decision about the handling
multicast packets and potential header modifications.

Fixes: be9b0169c840 ("batman-adv: mcast: implement multicast packet generation")
Signed-off-by: Sven Eckelmann <[email protected]>
---
 net/batman-adv/mesh-interface.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/batman-adv/mesh-interface.c b/net/batman-adv/mesh-interface.c
index b2c8febe..20582fe0 100644
--- a/net/batman-adv/mesh-interface.c
+++ b/net/batman-adv/mesh-interface.c
@@ -300,6 +300,8 @@ static netdev_tx_t batadv_interface_tx(struct sk_buff *skb,
 	if (batadv_compare_eth(ethhdr->h_dest, ectp_addr))
 		goto dropped;
 
+	batadv_skb_set_priority(skb, 0);
+
 	gw_mode = READ_ONCE(bat_priv->gw.mode);
 	if (is_multicast_ether_addr(ethhdr->h_dest)) {
 		/* if gw mode is off, broadcast every packet */
@@ -333,6 +335,9 @@ static netdev_tx_t batadv_interface_tx(struct sk_buff *skb,
 
 send:
 		if (do_bcast && !is_broadcast_ether_addr(ethhdr->h_dest)) {
+			/* WARNING batadv_mcast_forw_mode might add more headers
+			 * in front of the skb. and might even reallocate the skb
+			 */
 			forw_mode = batadv_mcast_forw_mode(bat_priv, skb, vid,
 							   &mcast_is_routable);
 			switch (forw_mode) {
@@ -350,8 +355,6 @@ static netdev_tx_t batadv_interface_tx(struct sk_buff *skb,
 		}
 	}
 
-	batadv_skb_set_priority(skb, 0);
-
 	/* ethernet packet should be broadcasted */
 	if (do_bcast) {
 		primary_if = batadv_primary_if_get_selected(bat_priv);

-- 
2.47.3