Re: [PATCH 3/3] nl80211: New command for setting TX rate mask for rate control

[Philip Prindeville <philipp_subx@redfish-solutions.com>]

  On 12/29/09 2:59 AM, Jouni Malinen wrote:

> Add a new NL80211_CMD_SET_TX_BITRATE_MASK command and related
> attributes to provide support for setting TX rate mask for rate
> control. This uses the existing cfg80211 set_bitrate_mask operation
> that was previously used only with WEXT compat code (SIOCSIWRATE). The
> nl80211 command allows more generic configuration of allowed rates as
> a mask instead of fixed/max rate.
>
> Signed-off-by: Jouni Malinen<jouni.malinen@atheros.com>
>
> ---
>   include/linux/nl80211.h |   44 +++++++++++++++++++
>   include/net/cfg80211.h  |    4 -
>   net/wireless/nl80211.c  |  111 ++++++++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 157 insertions(+), 2 deletions(-)
>
> --- wireless-testing.orig/include/linux/nl80211.h	2009-12-29 10:50:56.000000000 +0200
> +++ wireless-testing/include/linux/nl80211.h	2009-12-29 10:56:42.000000000 +0200
> @@ -295,6 +295,10 @@
>    *	This command is also used as an event to notify when a requested
>    *	remain-on-channel duration has expired.
>    *
> + * @NL80211_CMD_SET_TX_BITRATE_MASK: Set the mask of rates to be used in TX
> + *	rate selection. %NL80211_ATTR_IFINDEX is used to specify the interface
> + *	and @NL80211_ATTR_TX_RATES the set of allowed rates.
> + *
>    * @NL80211_CMD_MAX: highest used command number
>    * @__NL80211_CMD_AFTER_LAST: internal use
>    */
> @@ -381,6 +385,8 @@ enum nl80211_commands {
>   	NL80211_CMD_REMAIN_ON_CHANNEL,
>   	NL80211_CMD_CANCEL_REMAIN_ON_CHANNEL,
>
> +	NL80211_CMD_SET_TX_BITRATE_MASK,
> +
>   	/* add new commands above here */
>
>   	/* used to define NL80211_CMD_MAX below */
> @@ -638,6 +644,13 @@ enum nl80211_commands {
>    *
>    * @NL80211_ATTR_COOKIE: Generic 64-bit cookie to identify objects.
>    *
> + * @NL80211_ATTR_TX_RATES: Nested set of attributes
> + *	(enum nl80211_tx_rate_attributes) describing TX rates per band. The
> + *	enum nl80211_band value is used as the index (nla_type() of the nested
> + *	data. If a band is not included, it will be configured to allow all
> + *	rates based on negotiated supported rates information. This attribute
> + *	is used with %NL80211_CMD_SET_TX_BITRATE_MASK.
> + *
>    * @NL80211_ATTR_MAX: highest attribute number currently defined
>    * @__NL80211_ATTR_AFTER_LAST: internal use
>    */
> @@ -779,6 +792,8 @@ enum nl80211_attrs {
>
>   	NL80211_ATTR_COOKIE,
>
> +	NL80211_ATTR_TX_RATES,
> +
>   	/* add attributes here, update the policy in nl80211.c */
>
>   	__NL80211_ATTR_AFTER_LAST,
> @@ -1478,4 +1493,33 @@ enum nl80211_key_attributes {
>   	NL80211_KEY_MAX = __NL80211_KEY_AFTER_LAST - 1
>   };
>
> +/**
> + * enum nl80211_tx_rate_attributes - TX rate set attributes
> + * @__NL80211_TXRATE_INVALID: invalid
> + * @NL80211_TXRATE_LEGACY: Legacy (non-MCS) rates allowed for TX rate selection
> + *	in an array of rates as defined in IEEE 802.11 7.3.2.2 (u8 values with
> + *	1 = 500 kbps) but without the IE length restriction (at most
> + *	%NL80211_MAX_SUPP_RATES in a single array).
> + * @__NL80211_TXRATE_AFTER_LAST: internal
> + * @NL80211_TXRATE_MAX: highest TX rate attribute
> + */
> +enum nl80211_tx_rate_attributes {
> +	__NL80211_TXRATE_INVALID,
> +	NL80211_TXRATE_LEGACY,
> +
> +	/* keep last */
> +	__NL80211_TXRATE_AFTER_LAST,
> +	NL80211_TXRATE_MAX = __NL80211_TXRATE_AFTER_LAST - 1
> +};
> +
> +/**
> + * enum nl80211_band - Frequency band
> + * @NL80211_BAND_2GHZ - 2.4 GHz ISM band
> + * @NL80211_BAND_5GHZ - around 5 GHz band (4.9 - 5.7 GHz)
> + */
> +enum nl80211_band {
> +	NL80211_BAND_2GHZ,
> +	NL80211_BAND_5GHZ,
> +};
> +
>   #endif /* __LINUX_NL80211_H */
> --- wireless-testing.orig/net/wireless/nl80211.c	2009-12-29 10:50:57.000000000 +0200
> +++ wireless-testing/net/wireless/nl80211.c	2009-12-29 10:57:37.000000000 +0200
> @@ -143,6 +143,7 @@ static struct nla_policy nl80211_policy[
>   				 .len = WLAN_PMKID_LEN },
>   	[NL80211_ATTR_DURATION] = { .type = NLA_U32 },
>   	[NL80211_ATTR_COOKIE] = { .type = NLA_U64 },
> +	[NL80211_ATTR_TX_RATES] = { .type = NLA_NESTED },
>   };
>
>   /* policy for the attributes */
> @@ -572,6 +573,7 @@ static int nl80211_send_wiphy(struct sk_
>   	CMD(del_pmksa, DEL_PMKSA);
>   	CMD(flush_pmksa, FLUSH_PMKSA);
>   	CMD(remain_on_channel, REMAIN_ON_CHANNEL);
> +	CMD(set_bitrate_mask, SET_TX_BITRATE_MASK);
>   	if (dev->wiphy.flags&  WIPHY_FLAG_NETNS_OK) {
>   		i++;
>   		NLA_PUT_U32(msg, i, NL80211_CMD_SET_WIPHY_NETNS);
> @@ -4423,6 +4425,109 @@ static int nl80211_cancel_remain_on_chan
>   	return err;
>   }
>
> +static u32 rateset_to_mask(struct ieee80211_supported_band *sband,
> +			   u8 *rates, u8 rates_len)
> +{
> +	u8 i;
> +	u32 mask = 0;
> +
> +	for (i = 0; i<  rates_len; i++) {
> +		int rate = (rates[i]&  0x7f) * 5;
> +		int ridx;
> +		for (ridx = 0; ridx<  sband->n_bitrates; ridx++) {
> +			struct ieee80211_rate *srate =
> +				&sband->bitrates[ridx];
> +			if (rate == srate->bitrate) {
> +				mask |= 1<<  ridx;
> +				break;
> +			}
> +		}
> +		if (ridx == sband->n_bitrates)
> +			return 0; /* rate not found */
> +	}
> +
> +	return mask;
> +}
> +
> +static struct nla_policy
> +nl80211_txattr_policy[NL80211_TXRATE_MAX + 1] __read_mostly = {
> +	[NL80211_TXRATE_LEGACY] = { .type = NLA_BINARY,
> +				    .len = NL80211_MAX_SUPP_RATES },
> +};
> +
> +static int nl80211_set_tx_bitrate_mask(struct sk_buff *skb,
> +				       struct genl_info *info)
> +{
> +	struct nlattr *tb[NL80211_TXRATE_MAX + 1];
> +	struct cfg80211_registered_device *rdev;
> +	struct cfg80211_bitrate_mask mask;
> +	int err, rem, i;
> +	struct net_device *dev;
> +	struct nlattr *tx_rates;
> +	struct ieee80211_supported_band *sband;
> +
> +	if (info->attrs[NL80211_ATTR_TX_RATES] == NULL)
> +		return -EINVAL;
> +
> +	rtnl_lock();
> +
> +	err = get_rdev_dev_by_info_ifindex(info,&rdev,&dev);
> +	if (err)
> +		goto unlock_rtnl;
> +
> +	if (!rdev->ops->set_bitrate_mask) {
> +		err = -EOPNOTSUPP;
> +		goto unlock;
> +	}
> +
> +	memset(&mask, 0, sizeof(mask));
> +	/* Default to all rates enabled */
> +	for (i = 0; i<  IEEE80211_NUM_BANDS; i++) {
> +		sband = rdev->wiphy.bands[i];
> +		mask.control[i].legacy =
> +			sband ? (1<<  sband->n_bitrates) - 1 : 0;
> +	}
> +
> +	/*
> +	 * The nested attribute uses enum nl80211_band as the index. This maps
> +	 * directly to the enum ieee80211_band values used in cfg80211.
> +	 */
> +	nla_for_each_nested(tx_rates, info->attrs[NL80211_ATTR_TX_RATES], rem)
> +	{
> +		enum ieee80211_band band = nla_type(tx_rates);

Can this even work?  The first entry in nl80211_band is NL80211_BAND_2GHZ, i.e. zero.

Yet looking at libnl-1.1/lib/attr.c there's:

int nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len,
               struct nla_policy *policy)
{
...
         nla_for_each_attr(nla, head, len, rem) {
                 int type = nla_type(nla);

                 if (type == 0) {
                         fprintf(stderr, "Illegal nla->nla_type == 0\n");
                         continue;
                 }

so any time nla->nla_type is set to NL80211_BAND_2GHZ, isn't this going to be problematic?

Or am I misreading this code?

-Philip


> +		if (band<  0 || band>= IEEE80211_NUM_BANDS) {
> +			err = -EINVAL;
> +			goto unlock;
> +		}
> +		sband = rdev->wiphy.bands[band];
> +		if (sband == NULL) {
> +			err = -EINVAL;
> +			goto unlock;
> +		}
> +		nla_parse(tb, NL80211_TXRATE_MAX, nla_data(tx_rates),
> +			  nla_len(tx_rates), nl80211_txattr_policy);
> +		if (tb[NL80211_TXRATE_LEGACY]) {
> +			mask.control[band].legacy = rateset_to_mask(
> +				sband,
> +				nla_data(tb[NL80211_TXRATE_LEGACY]),
> +				nla_len(tb[NL80211_TXRATE_LEGACY]));
> +			if (mask.control[band].legacy == 0) {
> +				err = -EINVAL;
> +				goto unlock;
> +			}
> +		}
> +	}
> +
> +	err = rdev->ops->set_bitrate_mask(&rdev->wiphy, dev, NULL,&mask);
> +
> + unlock:
> +	dev_put(dev);
> +	cfg80211_unlock_rdev(rdev);
> + unlock_rtnl:
> +	rtnl_unlock();
> +	return err;
> +}
> +
>   static struct genl_ops nl80211_ops[] = {
>   	{
>   		.cmd = NL80211_CMD_GET_WIPHY,
> @@ -4697,6 +4802,12 @@ static struct genl_ops nl80211_ops[] = {
>   		.policy = nl80211_policy,
>   		.flags = GENL_ADMIN_PERM,
>   	},
> +	{
> +		.cmd = NL80211_CMD_SET_TX_BITRATE_MASK,
> +		.doit = nl80211_set_tx_bitrate_mask,
> +		.policy = nl80211_policy,
> +		.flags = GENL_ADMIN_PERM,
> +	},
>   };
>
>   static struct genl_multicast_group nl80211_mlme_mcgrp = {
> --- wireless-testing.orig/include/net/cfg80211.h	2009-12-29 10:54:29.000000000 +0200
> +++ wireless-testing/include/net/cfg80211.h	2009-12-29 10:55:52.000000000 +0200
> @@ -39,8 +39,8 @@
>    * @IEEE80211_BAND_5GHZ: around 5GHz band (4.9-5.7)
>    */
>   enum ieee80211_band {
> -	IEEE80211_BAND_2GHZ,
> -	IEEE80211_BAND_5GHZ,
> +	IEEE80211_BAND_2GHZ = NL80211_BAND_2GHZ,
> +	IEEE80211_BAND_5GHZ = NL80211_BAND_5GHZ,
>
>   	/* keep last */
>   	IEEE80211_NUM_BANDS
>