[PATCH] mac80211: enable IBSS merging

[Bruno Randolf <bruno@thinktube.com>]

addressing johannes latest comments and adding a channel check...

enable IBSS cell merging. if an IBSS beacon with the same channel, same ESSID
and a TSF higher than the local TSF (mactime) is received, we have to join its
BSSID.  while this might not be immediately apparent from reading the 802.11
standard it is compliant and necessary to make IBSS mode functional in many
cases. most drivers have a similar behaviour.

* move the relevant code section (previously only containing debug code) down
to the end of the function, so we can reuse the bss structure.

* we have to compare the mactime (TSF at the time of packet receive) rather
than the current TSF. since some drivers are not able to give a reliable
mactime we fall back to use the current TSF, which will be enough to catch most
(but not all) cases where an IBSS merge is necessary.

* in IBSS mode we want to allow beacons to override probe response info so we
can correctly do merges.

* we don't only configure beacons based on scan results, so change that
message.

* to enable this we have to let all beacons thru in IBSS mode, even if they
have a different BSSID.

Signed-off-by: Bruno Randolf <bruno@thinktube.com>
---

 include/net/mac80211.h       |    3 +-
 net/mac80211/ieee80211_sta.c |   70 ++++++++++++++++++++++++++----------------
 net/mac80211/rx.c            |    5 ++-
 3 files changed, 49 insertions(+), 29 deletions(-)


diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 460da54..4ae3a12 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -276,7 +276,8 @@ struct ieee80211_tx_control {
  * @RX_FLAG_FAILED_PLCP_CRC: Set this flag if the PCLP check failed on
  *	the frame.
  * @RX_FLAG_TSFT: The timestamp passed in the RX status (@mactime field)
- *	is valid.
+ *	is valid. This is useful in monitor mode and necessary for beacon frames
+ *	to enable IBSS merging.
  */
 enum mac80211_rx_flags {
 	RX_FLAG_MMIC_ERROR	= 1<<0,
diff --git a/net/mac80211/ieee80211_sta.c b/net/mac80211/ieee80211_sta.c
index 08f89fa..4df18ae 100644
--- a/net/mac80211/ieee80211_sta.c
+++ b/net/mac80211/ieee80211_sta.c
@@ -2202,7 +2202,7 @@ static void ieee80211_rx_bss_info(struct net_device *dev,
 	struct ieee80211_sta_bss *bss;
 	struct sta_info *sta;
 	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
-	u64 timestamp;
+	u64 timestamp, mactime;
 	DECLARE_MAC_BUF(mac);
 	DECLARE_MAC_BUF(mac2);
 
@@ -2220,30 +2220,6 @@ static void ieee80211_rx_bss_info(struct net_device *dev,
 		return;
 
 	timestamp = le64_to_cpu(mgmt->u.beacon.timestamp);
-
-	if (sdata->vif.type == IEEE80211_IF_TYPE_IBSS && beacon &&
-	    memcmp(mgmt->bssid, sdata->u.sta.bssid, ETH_ALEN) == 0) {
-#ifdef CONFIG_MAC80211_IBSS_DEBUG
-		static unsigned long last_tsf_debug = 0;
-		u64 tsf;
-		if (local->ops->get_tsf)
-			tsf = local->ops->get_tsf(local_to_hw(local));
-		else
-			tsf = -1LLU;
-		if (time_after(jiffies, last_tsf_debug + 5 * HZ)) {
-			printk(KERN_DEBUG "RX beacon SA=%s BSSID="
-			       "%s TSF=0x%llx BCN=0x%llx diff=%lld "
-			       "@%lu\n",
-			       print_mac(mac, mgmt->sa), print_mac(mac2, mgmt->bssid),
-			       (unsigned long long)tsf,
-			       (unsigned long long)timestamp,
-			       (unsigned long long)(tsf - timestamp),
-			       jiffies);
-			last_tsf_debug = jiffies;
-		}
-#endif /* CONFIG_MAC80211_IBSS_DEBUG */
-	}
-
 	ieee802_11_parse_elems(mgmt->u.beacon.variable, len - baselen, &elems);
 
 	if (sdata->vif.type == IEEE80211_IF_TYPE_IBSS && elems.supp_rates &&
@@ -2329,8 +2305,10 @@ static void ieee80211_rx_bss_info(struct net_device *dev,
 
 	bss->band = rx_status->band;
 
-	if (bss->probe_resp && beacon) {
-		/* Do not allow beacon to override data from Probe Response. */
+	if (sdata->vif.type != IEEE80211_IF_TYPE_IBSS &&
+	    bss->probe_resp && beacon) {
+		/* STA mode:
+		 * Do not allow beacon to override data from Probe Response. */
 		ieee80211_rx_bss_put(dev, bss);
 		return;
 	}
@@ -2434,6 +2412,44 @@ static void ieee80211_rx_bss_info(struct net_device *dev,
 	bss->noise = rx_status->noise;
 	if (!beacon)
 		bss->probe_resp++;
+
+	/* check if we need to merge IBSS */
+	if (sdata->vif.type == IEEE80211_IF_TYPE_IBSS && beacon &&
+	    !local->sta_sw_scanning && !local->sta_hw_scanning &&
+	    mgmt->u.beacon.capab_info & WLAN_CAPABILITY_IBSS &&
+	    bss->freq == local->oper_channel->center_freq &&
+	    elems.ssid_len == sdata->u.sta.ssid_len &&
+	    memcmp(elems.ssid, sdata->u.sta.ssid, sdata->u.sta.ssid_len) == 0) {
+		if (rx_status->flag & RX_FLAG_TSFT)
+			/* in order for correct IBSS merging we need mactime */
+			mactime = rx_status->mactime;
+		else if (local && local->ops && local->ops->get_tsf)
+			/* second best option: get current TSF */
+			mactime = local->ops->get_tsf(local_to_hw(local));
+		else
+			/* can't merge without knowing the TSF */
+			mactime = -1LLU;
+#ifdef CONFIG_MAC80211_IBSS_DEBUG
+		printk(KERN_DEBUG "RX beacon SA=%s BSSID="
+		       "%s TSF=0x%llx BCN=0x%llx diff=%lld @%lu\n",
+		       print_mac(mac, mgmt->sa),
+		       print_mac(mac2, mgmt->bssid),
+		       (unsigned long long)mactime,
+		       (unsigned long long)timestamp,
+		       (unsigned long long)(mactime - timestamp),
+		       jiffies);
+#endif /* CONFIG_MAC80211_IBSS_DEBUG */
+		if (mactime <= timestamp) {
+			if (CONFIG_MAC80211_IBSS_DEBUG || net_ratelimit())
+				printk(KERN_DEBUG "%s: beacon TSF higher than "
+				       "local TSF - IBSS merge with BSSID %s\n",
+				       dev->name, print_mac(mac, mgmt->bssid));
+			ieee80211_sta_join_ibss(dev, &sdata->u.sta, bss);
+			ieee80211_ibss_add_sta(dev, NULL,
+					       mgmt->bssid, mgmt->sa);
+		}
+	}
+
 	ieee80211_rx_bss_put(dev, bss);
 }
 
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index beda1bf..ed7cf37 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -1612,7 +1612,10 @@ static int prepare_for_handlers(struct ieee80211_sub_if_data *sdata,
 	case IEEE80211_IF_TYPE_IBSS:
 		if (!bssid)
 			return 0;
-		if (!ieee80211_bssid_match(bssid, sdata->u.sta.bssid)) {
+		if ((rx->fc & IEEE80211_FCTL_FTYPE) == IEEE80211_FTYPE_MGMT &&
+		    (rx->fc & IEEE80211_FCTL_STYPE) == IEEE80211_STYPE_BEACON)
+			return 1;
+		else if (!ieee80211_bssid_match(bssid, sdata->u.sta.bssid)) {
 			if (!(rx->flags & IEEE80211_TXRXD_RXIN_SCAN))
 				return 0;
 			rx->flags &= ~IEEE80211_TXRXD_RXRA_MATCH;