batman-adv: Fix broadcast packet CRC calculation

So far the crc16 checksum for a batman-adv broadcast data packet, received
on a batman-adv hard interface, was calculated over zero bytes of its
content leading to many incoming broadcast data packets wrongly being
dropped (60-80% packet loss).

This patch fixes this issue by calculating the crc16 over the actual,
complete broadcast payload.

The issue is a regression introduced by
("batman-adv: add broadcast duplicate check").

Signed-off-by: Linus Lüssing <linus.luessing@web.de>
Acked-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>

2 files changed, 11 insertions, 5 deletions

diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c
index 0a9084ad19a6..eebab20c7478 100644
--- a/net/batman-adv/bridge_loop_avoidance.c
+++ b/net/batman-adv/bridge_loop_avoidance.c
@@ -1210,8 +1210,8 @@ int batadv_bla_init(struct batadv_priv *bat_priv)
 /**
  * batadv_bla_check_bcast_duplist
  * @bat_priv: the bat priv with all the soft interface information
- * @bcast_packet: originator mac address
- * @hdr_size: maximum length of the frame
+ * @bcast_packet: encapsulated broadcast frame plus batman header
+ * @bcast_packet_len: length of encapsulated broadcast frame plus batman header
  *
  * check if it is on our broadcast list. Another gateway might
  * have sent the same packet because it is connected to the same backbone,
@@ -1224,14 +1224,14 @@ int batadv_bla_init(struct batadv_priv *bat_priv)
  */
 int batadv_bla_check_bcast_duplist(struct batadv_priv *bat_priv,
                                    struct batadv_bcast_packet *bcast_packet,
-                                   int hdr_size)
+                                   int bcast_packet_len)
 {
         int i, length, curr;
         uint8_t *content;
         uint16_t crc;
         struct batadv_bcast_duplist_entry *entry;
 
-        length = hdr_size - sizeof(*bcast_packet);
+        length = bcast_packet_len - sizeof(*bcast_packet);
         content = (uint8_t *)bcast_packet;
         content += sizeof(*bcast_packet);
 
diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c
index 939fc01371df..376b4cc6ca82 100644
--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -1124,8 +1124,14 @@ int batadv_recv_bcast_packet(struct sk_buff *skb,
 
         spin_unlock_bh(&orig_node->bcast_seqno_lock);
 
+        /* keep skb linear for crc calculation */
+        if (skb_linearize(skb) < 0)
+                goto out;
+
+        bcast_packet = (struct batadv_bcast_packet *)skb->data;
+
         /* check whether this has been sent by another originator before */
-        if (batadv_bla_check_bcast_duplist(bat_priv, bcast_packet, hdr_size))
+        if (batadv_bla_check_bcast_duplist(bat_priv, bcast_packet, skb->len))
                 goto out;
 
         /* rebroadcast packet */