[source] mac80211: fix skb size calculation in 4addr mode (FS#24)

[LEDE Commits]

jow pushed a commit to source.git, branch master:
https://git.lede-project.org/?p=source.git;a=commitdiff;h=1e03998e2b85e0250dd55da5146199a720e214af

commit 1e03998e2b85e0250dd55da5146199a720e214af
Author: Jo-Philipp Wich <jo at mein.io>
AuthorDate: Tue Jun 28 22:43:22 2016 +0200

    mac80211: fix skb size calculation in 4addr mode (FS#24)
    
    The PDU length of incoming LLC frames is set to the total skb payload size
    in __ieee80211_data_to_8023() of net/wireless/util.c which incorrectly
    includes the length of the IEEE 802.11 header.
    
    The resulting LLC frame header has a too large PDU length, causing the
    llc_fixup_skb() function of net/llc/llc_input.c to reject the incoming
    skb, effectively breaking STP.
    
    Solve the problem by properly substracting the IEEE 802.11 frame header size
    from the PDU length, allowing the LLC processor to pick up the incoming
    control messages.
    
    Special thanks to Gerry Rozema for tracking down the regression and proposing
    a suitable patch.
    
    Fixes FS#24.
    
    References:
    https://bugs.lede-project.org/index.php?do=details&task_id=24
    
    Reported-by: Gerry Rozema <gerryr at rozeware.com>
    Signed-off-by: Jo-Philipp Wich <jo at mein.io>
---
 .../mac80211/patches/533-mac80211_correct_4addr_skbsize.patch | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/package/kernel/mac80211/patches/533-mac80211_correct_4addr_skbsize.patch b/package/kernel/mac80211/patches/533-mac80211_correct_4addr_skbsize.patch
new file mode 100644
index 0000000..afd8cca
--- /dev/null
+++ b/package/kernel/mac80211/patches/533-mac80211_correct_4addr_skbsize.patch
@@ -0,0 +1,11 @@
+--- a/net/wireless/util.c
++++ b/net/wireless/util.c
+@@ -509,7 +509,7 @@ static int __ieee80211_data_to_8023(stru
+ 		 * replace EtherType */
+ 		hdrlen += ETH_ALEN + 2;
+ 	else
+-		tmp.h_proto = htons(skb->len);
++		tmp.h_proto = htons(skb->len - hdrlen);
+ 
+ 	pskb_pull(skb, hdrlen);
+