diff mbox

batman-adv: dirty hack to recompute mac_len in the rx path

Message ID 1350218817-18871-1-git-send-email-siwu@hrz.tu-chemnitz.de (mailing list archive)
State Accepted, archived
Headers

Commit Message

Simon Wunderlich Oct. 14, 2012, 12:46 p.m. UTC 
  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 <ordex@autistici.org>
Signed-off-by: Simon Wunderlich <siwu@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(+)

Comments

Marek Lindner Oct. 14, 2012, 6:53 p.m. UTC | #1 
On Sunday, October 14, 2012 20:46:57 Simon Wunderlich wrote:
> 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 <ordex@autistici.org>
> Signed-off-by: Simon Wunderlich <siwu@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(+)

Applied in revision a6ad857.

Thanks,
Marek
diff mbox

Patch

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_ */