[PATCH v3] mac80211: do not TX injected frames when not allowed

[PATCH v3] mac80211: do not TX injected frames when not allowed

[Luis R. Rodriguez]

Monitor mode is able to TX by using injected frames. We should
not allow injected frames to be sent unless allowed by regulatory
rules. Since AP mode uses a monitor interfaces to transmit
management frames we have to take care to not break AP mode as
well while resolving this. We deal with this by allowing compliant
APs solutions to inform mac80211 if their monitor interface is
intended to be used for an AP by setting a cfg80211 flag for the
monitor interface. hostapd, for example, currently does its own
checks to ensure AP mode is not used on channels which require radar
detection. Once such solutions are available it can can enable this
flag.

Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
---

Note that we also add the passive scan flag now as well. Passive scan
is used for STAs on DFS channels *and* when on world regulatory domains where
you are your location is unknown yet. Once a location is known by finding
a local AP though you should be good to TX, but the found regulatory domain
would indicate this to us.

 include/linux/nl80211.h |    3 +++
 include/net/cfg80211.h  |    4 ++++
 net/mac80211/tx.c       |   22 ++++++++++++++++++++++
 net/wireless/nl80211.c  |    1 +
 4 files changed, 30 insertions(+), 0 deletions(-)

diff --git a/include/linux/nl80211.h b/include/linux/nl80211.h
index 76aae3d..3357907 100644
--- a/include/linux/nl80211.h
+++ b/include/linux/nl80211.h
@@ -705,6 +705,8 @@ enum nl80211_reg_rule_flags {
  * @NL80211_MNTR_FLAG_OTHER_BSS: disable BSSID filtering
  * @NL80211_MNTR_FLAG_COOK_FRAMES: report frames after processing.
  *	overrides all other flags.
+ * @NL80211_MNTR_FLAG_AP_MGT: this monitor interface is used for AP mode
+ * 	to be able to inject management frames.
  *
  * @__NL80211_MNTR_FLAG_AFTER_LAST: internal use
  * @NL80211_MNTR_FLAG_MAX: highest possible monitor flag
@@ -716,6 +718,7 @@ enum nl80211_mntr_flags {
 	NL80211_MNTR_FLAG_CONTROL,
 	NL80211_MNTR_FLAG_OTHER_BSS,
 	NL80211_MNTR_FLAG_COOK_FRAMES,
+	NL80211_MNTR_FLAG_AP_MGT,
 
 	/* keep last */
 	__NL80211_MNTR_FLAG_AFTER_LAST,
diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index dd1fd51..fe65c64 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -255,6 +255,9 @@ struct station_info {
  * @MONITOR_FLAG_CONTROL: pass control frames
  * @MONITOR_FLAG_OTHER_BSS: disable BSSID filtering
  * @MONITOR_FLAG_COOK_FRAMES: report frames after processing
+ * @MONITOR_FLAG_AP_MGT: informs us this monitor interface is
+ *	used by a driver for AP mode to be able to inject management
+ * 	frames.
  */
 enum monitor_flags {
 	MONITOR_FLAG_FCSFAIL		= 1<<NL80211_MNTR_FLAG_FCSFAIL,
@@ -262,6 +265,7 @@ enum monitor_flags {
 	MONITOR_FLAG_CONTROL		= 1<<NL80211_MNTR_FLAG_CONTROL,
 	MONITOR_FLAG_OTHER_BSS		= 1<<NL80211_MNTR_FLAG_OTHER_BSS,
 	MONITOR_FLAG_COOK_FRAMES	= 1<<NL80211_MNTR_FLAG_COOK_FRAMES,
+	MONITOR_FLAG_AP_MGT		= 1<<NL80211_MNTR_FLAG_AP_MGT,
 };
 
 /**
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 7b013fb..f242cf4 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1432,11 +1432,33 @@ int ieee80211_master_start_xmit(struct sk_buff *skb, struct net_device *dev)
 int ieee80211_monitor_start_xmit(struct sk_buff *skb,
 				 struct net_device *dev)
 {
+	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
 	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
+	struct ieee80211_channel *chan = local->hw.conf.channel;
 	struct ieee80211_radiotap_header *prthdr =
 		(struct ieee80211_radiotap_header *)skb->data;
 	u16 len_rthdr;
 
+	/*
+	 * Frame injection is not allowed if beaconing is not allowed
+	 * or if we need radar detection. Beaconing is usually not allowed when
+	 * the mode or operation (Adhoc, AP, Mesh) does not support DFS.
+	 * Passive scan is also used in world regulatory domains where
+	 * your country is not known and as such it should be treated as
+	 * NO TX unless the channel is explicitly allowed in which case
+	 * your current regulatory domain would not have the passive scan
+	 * flag.
+	 *
+	 * Since AP mode uses monitor interfaces to inject/TX management
+	 * frames we make AP mode the exception to this rule as its
+	 * implementation can deal with radar detection by itself.
+	 */
+	if (!(sdata->u.mntr_flags & MONITOR_FLAG_AP_MGT) &&
+	   (chan->flags & (IEEE80211_CHAN_NO_IBSS |
+	   IEEE80211_CHAN_RADAR |
+	   IEEE80211_CHAN_PASSIVE_SCAN)))
+		goto fail;
+
 	/* check for not even having the fixed radiotap header part */
 	if (unlikely(skb->len < sizeof(struct ieee80211_radiotap_header)))
 		goto fail; /* too short to be possibly valid */
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index e69da8d..3c6327d 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -537,6 +537,7 @@ static const struct nla_policy mntr_flags_policy[NL80211_MNTR_FLAG_MAX + 1] = {
 	[NL80211_MNTR_FLAG_CONTROL] = { .type = NLA_FLAG },
 	[NL80211_MNTR_FLAG_OTHER_BSS] = { .type = NLA_FLAG },
 	[NL80211_MNTR_FLAG_COOK_FRAMES] = { .type = NLA_FLAG },
+	[NL80211_MNTR_FLAG_AP_MGT] = { .type = NLA_FLAG },
 };
 
 static int parse_monitor_flags(struct nlattr *nla, u32 *mntrflags)
-- 
1.6.1.rc3.51.g5832d

Re: [PATCH v3] mac80211: do not TX injected frames when not allowed

[Johannes Berg]

[-- Attachment #1: Type: text/plain, Size: 1430 bytes --]

On Tue, 2009-01-27 at 18:50 -0800, Luis R. Rodriguez wrote:
> Monitor mode is able to TX by using injected frames. We should
> not allow injected frames to be sent unless allowed by regulatory
> rules. Since AP mode uses a monitor interfaces to transmit
> management frames we have to take care to not break AP mode as
> well while resolving this. We deal with this by allowing compliant
> APs solutions to inform mac80211 if their monitor interface is
> intended to be used for an AP by setting a cfg80211 flag for the
> monitor interface. hostapd, for example, currently does its own
> checks to ensure AP mode is not used on channels which require radar
> detection. Once such solutions are available it can can enable this
> flag.

> Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>

Acked-by: Johannes Berg <johannes@sipsolutions.net>

if you fix the indentation here:

> +	 * Since AP mode uses monitor interfaces to inject/TX management
> +	 * frames we make AP mode the exception to this rule as its
> +	 * implementation can deal with radar detection by itself.
> +	 */
> +	if (!(sdata->u.mntr_flags & MONITOR_FLAG_AP_MGT) &&
> +	   (chan->flags & (IEEE80211_CHAN_NO_IBSS |
> +	   IEEE80211_CHAN_RADAR |
> +	   IEEE80211_CHAN_PASSIVE_SCAN)))
> +		goto fail;

to indent like this:

if (...
    (chan->flags & (.. |
                    .. |
                    ..)))

johannes

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 836 bytes --]

Re: [PATCH v3] mac80211: do not TX injected frames when not allowed

[Johannes Berg]

[-- Attachment #1: Type: text/plain, Size: 1127 bytes --]

On Tue, 2009-01-27 at 18:50 -0800, Luis R. Rodriguez wrote:
> Monitor mode is able to TX by using injected frames. We should
> not allow injected frames to be sent unless allowed by regulatory
> rules. Since AP mode uses a monitor interfaces to transmit
> management frames we have to take care to not break AP mode as
> well while resolving this. We deal with this by allowing compliant
> APs solutions to inform mac80211 if their monitor interface is
> intended to be used for an AP by setting a cfg80211 flag for the
> monitor interface. hostapd, for example, currently does its own
> checks to ensure AP mode is not used on channels which require radar
> detection. Once such solutions are available it can can enable this
> flag.

> + * @NL80211_MNTR_FLAG_AP_MGT: this monitor interface is used for AP mode
> + * 	to be able to inject management frames.

Come to think of it, is that really a good name? The intention is "will
check for radar" but then we don't even have a way to check for radar
yet!

So maybe we should leave that out, and introduce it with proper radar
support later?

johannes

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 836 bytes --]

Re: [PATCH v3] mac80211: do not TX injected frames when not allowed

[Luis R. Rodriguez]

On Fri, Jan 30, 2009 at 03:03:02AM -0800, Johannes Berg wrote:
> On Tue, 2009-01-27 at 18:50 -0800, Luis R. Rodriguez wrote:
> > Monitor mode is able to TX by using injected frames. We should
> > not allow injected frames to be sent unless allowed by regulatory
> > rules. Since AP mode uses a monitor interfaces to transmit
> > management frames we have to take care to not break AP mode as
> > well while resolving this. We deal with this by allowing compliant
> > APs solutions to inform mac80211 if their monitor interface is
> > intended to be used for an AP by setting a cfg80211 flag for the
> > monitor interface. hostapd, for example, currently does its own
> > checks to ensure AP mode is not used on channels which require radar
> > detection. Once such solutions are available it can can enable this
> > flag.
> 
> > + * @NL80211_MNTR_FLAG_AP_MGT: this monitor interface is used for AP mode
> > + * 	to be able to inject management frames.
> 
> Come to think of it, is that really a good name? The intention is "will
> check for radar" but then we don't even have a way to check for radar
> yet!
> 
> So maybe we should leave that out, and introduce it with proper radar
> support later?

Dude, that's the approach I had in my first patch for this, you had suggested
to add this so I did. Anyway yeah I agree, heh. I'll send v5.

  Luis