[PATCH] mac80211: enable to inject a-msdu frames using monitor interface

[PATCH] mac80211: enable to inject a-msdu frames using monitor interface

[Michael Braun]

Problem: When injecting an A-MSDU using a PF_PACKET socket, the qos flag
IEEE80211_QOS_CTL_A_MSDU_PRESENT is cleared.

How to reproduce: Inject a frame on a mac80211 hwsim monitor interface and
have tshark sniffing on this monitor interface.
You'll see the packet twice: Once with correct flag and once with flag
cleared. On hwsim0, you'll only see the packet with a cleared flag.

I guess the same is needed for packets with IEEE80211_TX_CTRL_AMSDU set.

Signed-off-by: Michael Braun <michael-dev@fami-braun.de>
---
 net/mac80211/wme.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/mac80211/wme.c b/net/mac80211/wme.c
index 9eb0aee..3faa972 100644
--- a/net/mac80211/wme.c
+++ b/net/mac80211/wme.c
@@ -248,6 +248,13 @@ void ieee80211_set_qos_hdr(struct ieee80211_sub_if_data *sdata,
 	/* preserve EOSP bit */
 	ack_policy = *p & IEEE80211_QOS_CTL_EOSP;
 
+	/* preserve A-MSDU bit for MONITOR interfaces to allow injecting
+	 * A-MSDU frames
+	 */
+	if (info->flags & IEEE80211_TX_CTL_INJECTED ||
+	    info->control.flags & IEEE80211_TX_CTRL_AMSDU)
+		ack_policy |= *p & IEEE80211_QOS_CTL_A_MSDU_PRESENT;
+
 	if (is_multicast_ether_addr(hdr->addr1) ||
 	    sdata->noack_map & BIT(tid)) {
 		ack_policy |= IEEE80211_QOS_CTL_ACK_POLICY_NOACK;
-- 
2.1.4

Re: [PATCH] mac80211: enable to inject a-msdu frames using monitor interface

[Johannes Berg]

On Fri, 2016-10-07 at 22:29 +0200, Michael Braun wrote:
> 
> I guess the same is needed for packets with IEEE80211_TX_CTRL_AMSDU
> set.

I don't think that's true, since we don't get here after A-MSDU
building in mac80211.

>  	/* preserve EOSP bit */
>  	ack_policy = *p & IEEE80211_QOS_CTL_EOSP;
>  
> +	/* preserve A-MSDU bit for MONITOR interfaces to allow
> injecting
> +	 * A-MSDU frames
> +	 */
> +	if (info->flags & IEEE80211_TX_CTL_INJECTED ||
> +	    info->control.flags & IEEE80211_TX_CTRL_AMSDU)
> +		ack_policy |= *p & IEEE80211_QOS_CTL_A_MSDU_PRESENT;

However, why not just unconditionally preserve it?

johannes