It is possible that the mac_len is not properly exported because of
strange device configuration (this behaviour has been observed when
using batman-adv on top of a vlan interface). Therefore it is needed to
explicitly recompute it at the very beginning of the rx path.
This is done by appending the recompute function to the skb_share_mac()
function, hence the "dirty hack" in the subject. We expect this problem to
be fixed in linux 3.8 and above.
Reported-by: Antonio Quartulli <or...@autistici.org>
Signed-off-by: Simon Wunderlich <s...@hrz.tu-chemnitz.de>
---
this is a rewrite of Antonios patch
"batman-adv: recompute mac_len at the beginning of the rx path". It is
intended to fix the issue for out-of-kernel releases, without hurting
the in-kernel code too much. Obviously, this patch won't go upstream
into the kernel.
This version includes Svens "more sane" version, and also has implements
skb_reset_mac_len() for kernels prior to 3.0.
---
compat.h | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/compat.h b/compat.h
index 14969e0..47223f5 100644
--- a/compat.h
+++ b/compat.h
@@ -137,6 +137,11 @@ void batadv_free_rcu_neigh_node(struct rcu_head *rcu);
void batadv_free_rcu_tt_local_entry(struct rcu_head *rcu);
void batadv_free_rcu_backbone_gw(struct rcu_head *rcu);
+static inline void skb_reset_mac_len(struct sk_buff *skb)
+{
+ skb->mac_len = skb->network_header - skb->mac_header;
+}
+
#endif /* < KERNEL_VERSION(3, 0, 0) */
@@ -159,4 +164,23 @@ static inline void eth_hw_addr_random(struct net_device
*dev)
#endif /* < KERNEL_VERSION(3, 5, 0) */
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 8, 0)
+
+/* hack for not correctly set mac_len. This may happen for some special
+ * configurations like batman-adv on VLANs.
+ *
+ * This is pretty dirty, but we only use skb_share_check() in main.c right
+ * before mac_len is checked, and the recomputation shouldn't hurt too much.
+ */
+#define skb_share_check(skb, b) \
+ ({ \
+ struct sk_buff *_t_skb; \
+ _t_skb = skb_share_check(skb, b); \
+ if (_t_skb) \
+ skb_reset_mac_len(_t_skb); \
+ _t_skb; \
+ })
+
+#endif /* < KERNEL_VERSION(3, 8, 0) */
+
#endif /* _NET_BATMAN_ADV_COMPAT_H_ */
--
1.7.10
