mac80211: fix the mesh channel switch support

Mesh STA receiving the mesh CSA action frame is not able to trigger
the mesh channel switch due to the incorrect handling and comparison
of mesh channel switch parameters element (MCSP)'s TTL. Make sure
the MCSP's TTL is updated accordingly before calling the
ieee80211_mesh_process_chnswitch. Also, we update the beacon before
forwarding the CSA action frame, so MCSP's precedence value and
initiator flag need to be updated prior to this.

Signed-off-by: Chun-Yeow Yeoh <[e-mail]>
Signed-off-by: Johannes Berg <[e-mail]>

net/mac80211/cfg.c

···
 		    params->chandef.chan->band)
 			return -EINVAL;
 
+		ifmsh->chsw_init = true;
+		if (!ifmsh->pre_value)
+			ifmsh->pre_value = 1;
+		else
+			ifmsh->pre_value++;
+
 		err = ieee80211_mesh_csa_beacon(sdata, params, true);
-		if (err < 0)
+		if (err < 0) {
+			ifmsh->chsw_init = false;
 			return err;
+		}
 		break;
 #endif
 	default:

net/mac80211/ieee80211_i.h

···
 	u8 mode;
 	u8 count;
 	u8 ttl;
+	u16 pre_value;
 };
 
 /* Parsed Information Elements */

net/mac80211/mesh.c

···
 		 params.chandef.chan->center_freq);
 
 	params.block_tx = csa_ie.mode & WLAN_EID_CHAN_SWITCH_PARAM_TX_RESTRICT;
-	if (beacon)
+	if (beacon) {
 		ifmsh->chsw_ttl = csa_ie.ttl - 1;
-	else
-		ifmsh->chsw_ttl = 0;
+		if (ifmsh->pre_value >= csa_ie.pre_value)
+			return false;
+		ifmsh->pre_value = csa_ie.pre_value;
+	}
 
-	if (ifmsh->chsw_ttl > 0)
+	if (ifmsh->chsw_ttl < ifmsh->mshcfg.dot11MeshTTL) {
 		if (ieee80211_mesh_csa_beacon(sdata, &params, false) < 0)
 			return false;
+	} else {
+		return false;
+	}
 
 	sdata->csa_radar_required = params.radar_required;
 
···
 	offset_ttl = (len < 42) ? 7 : 10;
 	*(pos + offset_ttl) -= 1;
 	*(pos + offset_ttl + 1) &= ~WLAN_EID_CHAN_SWITCH_PARAM_INITIATOR;
-	sdata->u.mesh.chsw_ttl = *(pos + offset_ttl);
 
 	memcpy(mgmt_fwd, mgmt, len);
 	eth_broadcast_addr(mgmt_fwd->da);
···
 	u16 pre_value;
 	bool fwd_csa = true;
 	size_t baselen;
-	u8 *pos, ttl;
+	u8 *pos;
 
 	if (mgmt->u.action.u.measurement.action_code !=
 	    WLAN_ACTION_SPCT_CHL_SWITCH)
···
 			   u.action.u.chan_switch.variable);
 	ieee802_11_parse_elems(pos, len - baselen, false, &elems);
 
-	ttl = elems.mesh_chansw_params_ie->mesh_ttl;
-	if (!--ttl)
+	ifmsh->chsw_ttl = elems.mesh_chansw_params_ie->mesh_ttl;
+	if (!--ifmsh->chsw_ttl)
 		fwd_csa = false;
 
 	pre_value = le16_to_cpu(elems.mesh_chansw_params_ie->mesh_pre_value);

net/mac80211/spectmgmt.c

···
 	if (elems->mesh_chansw_params_ie) {
 		csa_ie->ttl = elems->mesh_chansw_params_ie->mesh_ttl;
 		csa_ie->mode = elems->mesh_chansw_params_ie->mesh_flags;
+		csa_ie->pre_value = le16_to_cpu(
+				elems->mesh_chansw_params_ie->mesh_pre_value);
 	}
 
 	new_freq = ieee80211_channel_to_frequency(new_chan_no, new_band);

net/mac80211/util.c

···
 			  WLAN_EID_CHAN_SWITCH_PARAM_TX_RESTRICT : 0x00;
 		put_unaligned_le16(WLAN_REASON_MESH_CHAN, pos); /* Reason Cd */
 		pos += 2;
-		if (!ifmsh->pre_value)
-			ifmsh->pre_value = 1;
-		else
-			ifmsh->pre_value++;
 		pre_value = cpu_to_le16(ifmsh->pre_value);
 		memcpy(pos, &pre_value, 2);		/* Precedence Value */
 		pos += 2;
-		ifmsh->chsw_init = true;
 	}
 
 	ieee80211_tx_skb(sdata, skb);