Fragment and 11s inconsistency

[Rui Paulo]

On 2012/02/14, at 14:14, Monthadar Al Jaberi wrote:

> Hi,
> 
> I cant verify this yet, but isn't there something wrong in current FreeBSD?
> 
> lets say an 11s data frame need to be fragmented in ieee80211_encap:
> if (addqos)
> 		hdrsize = sizeof(struct ieee80211_qosframe);
> else
> 		hdrsize = sizeof(struct ieee80211_frame);
> ...
> if (vap->iv_opmode == IEEE80211_M_MBSS) {
> ...
> 		if (!IEEE80211_IS_MULTICAST(eh.ether_dhost))
> 			hdrsize += IEEE80211_ADDR_LEN;	/* unicast are 4-addr */
> 		meshhdrsize = sizeof(struct ieee80211_meshcntl);
> }
> ...
> if (__predict_true((m->m_flags & M_FF) == 0)) {
> 		/*
> 		 * Normal frame.
> 		 */
> 		m = ieee80211_mbuf_adjust(vap, hdrspace + meshhdrsize, key, m);
> }
> M_PREPEND(m, hdrspace + meshhdrsize, M_DONTWAIT);
> if (txfrag && !ieee80211_fragment(vap, m, hdrsize,
> 	    key != NULL ? key->wk_cipher->ic_header : 0, vap->iv_fragthreshold))
> 		goto bad;
> 
> This means we send meshcontrol only in first segment, because we never
> add meshhdrsize to hdrsize...

Yes, this is a bug. Thanks for finding it.

> but in mesh_input
> switch (type) {
> 	case IEEE80211_FC0_TYPE_DATA:
> ...
> meshdrlen = sizeof(struct ieee80211_meshcntl) +
> 		    (mc->mc_flags & 3) * IEEE80211_ADDR_LEN;
> 		hdrspace += meshdrlen;
> ...
> 		/*
> 		 * Potentially forward packet.  See table s36 (p140)
> 		 * for the rules.  XXX tap fwd'd packets not for us?
> 		 */
> 		if (dir == IEEE80211_FC1_DIR_FROMDS ||
> 		    !mesh_isucastforme(vap, wh, mc)) {
> 			mesh_forward(vap, m, mc);
> ...
> if (!IEEE80211_IS_MULTICAST(wh->i_addr1)) {
> 			m = ieee80211_defrag(ni, m, hdrspace);
> 			if (m == NULL) {
> 
> This seems wrong to me, how can we potentially forward before defragin
> the frame? this will fail cause sub-frag have no mesh control as code
> shows above.
> 
> shouldnt the defrag code be moved above?

Yes, another bug.

> I am attaching a patch that both moves the defrag, validates that mesh
> control is present and makes 11s data frames QoS and set Mesh control
> bit present to 1 as the amendment specifies.

There are some typos in your patch ("This is in constrast to Draf 4.0.").

Can you please rewrite this code:
+		*(uint16_t *)qos = *(uint16_t *)
+		    (((IEEE80211_IS_MULTICAST(wh->i_addr1) &&
+		    dir == IEEE80211_FC1_DIR_FROMDS)) ?
+		    ((struct ieee80211_qosframe *)wh)->i_qos :
+		    ((struct ieee80211_qosframe_addr4 *)wh)->i_qos);

In ieee80211_encap(), why didn't you add meshhdrsize to ieee80211_fragment()?

Would be nice to test this  before committing.

Thanks,
--
Rui Paulo