2016-10-10 16:52:45

by michael-dev

Subject: [PATCH] mac80211: fix A-MSDU outer SA/DA

According to IEEE 802.11-2012 section 8.3.2 table 8-19, the outer SA/DA
of A-MSDU frames need to be changed depending on FromDS/ToDS values.

Signed-off-by: Michael Braun <[email protected]>
---
net/mac80211/tx.c | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 5023966..acd334c 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3050,7 +3050,7 @@ static bool ieee80211_amsdu_prepare_head(struct ieee80211_sub_if_data *sdata,
int hdr_len = fast_tx->hdr_len - sizeof(rfc1042_header);
int subframe_len = skb->len - hdr_len;
void *data;
- u8 *qc;
+ u8 *qc, *bssid;

if (info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE)
return false;
@@ -3062,10 +3062,32 @@ static bool ieee80211_amsdu_prepare_head(struct ieee80211_sub_if_data *sdata,
&subframe_len))
return false;

+ switch (sdata->vif.type) {
+ case NL80211_IFTYPE_STATION:
+ bssid = sdata->u.mgd.bssid;
+ break;
+ case NL80211_IFTYPE_AP:
+ case NL80211_IFTYPE_AP_VLAN:
+ bssid = sdata->vif.addr;
+ break;
+ default:
+ bssid = NULL;
+ }
+
amsdu_hdr.h_proto = cpu_to_be16(subframe_len);
memcpy(amsdu_hdr.h_source, skb->data + fast_tx->sa_offs, ETH_ALEN);
memcpy(amsdu_hdr.h_dest, skb->data + fast_tx->da_offs, ETH_ALEN);

+ /* according to IEEE 802.11-2012 8.3.2 table 8-19, the outer SA/DA
+ * fields needs to be changed to BSSID for A-MSDU frames depending
+ * on FromDS/ToDS values.
+ */
+ hdr = data;
+ if (bssid && ieee80211_has_fromds(hdr->frame_control))
+ memcpy(amsdu_hdr.h_source, bssid, ETH_ALEN);
+ if (bssid && ieee80211_has_tods(hdr->frame_control))
+ memcpy(amsdu_hdr.h_dest, bssid, ETH_ALEN);
+
data = skb_push(skb, sizeof(amsdu_hdr));
memmove(data, data + sizeof(amsdu_hdr), hdr_len);
memcpy(data + hdr_len, &amsdu_hdr, sizeof(amsdu_hdr));
--
2.1.4

2016-10-12 07:57:32

by Johannes Berg

Subject: Re: [PATCH] mac80211: fix A-MSDU outer SA/DA

On Wed, 2016-10-12 at 09:53 +0200, Johannes Berg wrote:
> On Mon, 2016-10-10 at 18:52 +0200, Michael Braun wrote:
> >
> > According to IEEE 802.11-2012 section 8.3.2 table 8-19, the outer
> > SA/DA of A-MSDU frames need to be changed depending on FromDS/ToDS
> > values.
>
> "Need to" is perhaps a bit strongly worded, but whatever :)
>
> I was going to write a long reply and whatever - but I think that's
> all moot. As far as I can tell, you got this completely wrong, as
> you're changing the *inner* headers, not the *outer* header as you
> should?

Oh, no, my mistake - this happens before 802.3->.11 conversion.

So this does look correct, but I don't like that you write to
amsdu_hdr.h_{source,dest} twice after the patch.

I think you should have da and sa variables and set those, and then
memcpy only once.

johannes

2016-10-12 08:14:09

by Johannes Berg

Subject: Re: [PATCH] mac80211: fix A-MSDU outer SA/DA

On Mon, 2016-10-10 at 18:52 +0200, Michael Braun wrote:
> According to IEEE 802.11-2012 section 8.3.2 table 8-19, the outer
> SA/DA of A-MSDU frames need to be changed depending on FromDS/ToDS
> values.

"Need to" is perhaps a bit strongly worded, but whatever :)

I was going to write a long reply and whatever - but I think that's all
moot. As far as I can tell, you got this completely wrong, as you're
changing the *inner* headers, not the *outer* header as you should?

johannes