This patch makes mac80211 warn (once) when the driver passes up a
frame in which the payload data is not aligned on a four-byte
boundary, with a long comment for people who run into the condition
and need to know what to do.

Signed-off-by: Johannes Berg <[EMAIL PROTECTED]>
---
 net/mac80211/rx.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

--- everything.orig/net/mac80211/rx.c   2007-12-18 14:47:18.433014323 +0100
+++ everything/net/mac80211/rx.c        2007-12-18 14:48:47.113014051 +0100
@@ -1619,6 +1619,7 @@ void __ieee80211_rx(struct ieee80211_hw 
        struct ieee80211_sub_if_data *prev = NULL;
        struct sk_buff *skb_new;
        u8 *bssid;
+       int hdrlen;
 
        /*
         * key references and virtual interfaces are protected using RCU
@@ -1648,6 +1649,18 @@ void __ieee80211_rx(struct ieee80211_hw 
        rx.fc = le16_to_cpu(hdr->frame_control);
        type = rx.fc & IEEE80211_FCTL_FTYPE;
 
+       /*
+        * Drivers are required to align the payload data to a four-byte
+        * boundary, so the last two bits of the address where it starts
+        * may not be set. The header is required to be directly before
+        * the payload data, padding like atheros hardware adds which is
+        * inbetween the 802.11 header and the payload is not supported,
+        * the driver is required to move the 802.11 header further back
+        * in that case.
+        */
+       hdrlen = ieee80211_get_hdrlen(rx.fc);
+       WARN_ON_ONCE(((unsigned long)(skb->data + hdrlen)) & 3);
+
        if (type == IEEE80211_FTYPE_DATA || type == IEEE80211_FTYPE_MGMT)
                local->dot11ReceivedFragmentCount++;
 


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