Re: [ath5k-devel] [PATCH] addressing johannes latest comments and adding a channel check...

[bruno randolf <bruno@thinktube.com>]

uups, sorry stg mail (well, i...) confused the subject lines

bruno

On Wednesday 06 February 2008 11:46:40 Bruno Randolf wrote:
> mac80211: enable IBSS merging
>
> 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;
>
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