Message-ID: <ZBDEoDeEUb6BQsf6@localhost.localdomain>
Date:   Tue, 14 Mar 2023 20:01:52 +0100
From:   Michal Kubiak <michal.kubiak@...el.com>
To:     Jaewan Kim <jaewan@...gle.com>
CC:     <gregkh@...uxfoundation.org>, <johannes@...solutions.net>,
        <linux-wireless@...r.kernel.org>, <netdev@...r.kernel.org>,
        <kernel-team@...roid.com>, <adelva@...gle.com>
Subject: Re: [PATCH v9 1/5] mac80211_hwsim: add PMSR capability support

On Wed, Mar 15, 2023 at 01:36:02AM +0900, Jaewan Kim wrote:
> On Tue, Mar 14, 2023 at 1:52 AM Michal Kubiak <michal.kubiak@...el.com> wrote:
> >
> > On Mon, Mar 13, 2023 at 07:53:22AM +0000, Jaewan Kim wrote:
> > > PMSR (a.k.a. peer measurement) is generalized measurement between two
> > > Wi-Fi devices. And currently FTM (a.k.a. fine time measurement or flight
> > > time measurement) is the one and only measurement. FTM is measured by
> > > RTT (a.k.a. round trip time) of packets between two Wi-Fi devices.
> > >
> > > Add necessary functionality to allow mac80211_hwsim to be configured with
> > > PMSR capability. The capability is mandatory to accept incoming PMSR
> > > request because nl80211_pmsr_start() ignores incoming the request without
> > > the PMSR capability.
> > >
> > > In detail, add new mac80211_hwsim attribute HWSIM_ATTR_PMSR_SUPPORT.
> > > HWSIM_ATTR_PMSR_SUPPORT is used to set PMSR capability when creating a new
> > > radio. To send extra capability details, HWSIM_ATTR_PMSR_SUPPORT can have
> > > nested PMSR capability attributes defined in the nl80211.h. Data format is
> > > the same as cfg80211_pmsr_capabilities.
> > >
> > > If HWSIM_ATTR_PMSR_SUPPORT is specified, mac80211_hwsim builds
> > > cfg80211_pmsr_capabilities and sets wiphy.pmsr_capa.
> > >
> > > Signed-off-by: Jaewan Kim <jaewan@...gle.com>
> >
> > Hi,
> >
> > Just a few style comments and suggestions.
> >
> > Thanks,
> > Michal
> >
> > > ---
> > > V8 -> V9: Changed to consider unknown PMSR type as error.
> > > V7 -> V8: Changed not to send pmsr_capa when adding new radio to limit
> > >           exporting cfg80211 function to driver.
> > > V6 -> V7: Added terms definitions. Removed pr_*() uses.
> > > V5 -> V6: Added per change patch history.
> > > V4 -> V5: Fixed style for commit messages.
> > > V3 -> V4: Added change details for new attribute, and fixed memory leak.
> > > V1 -> V3: Initial commit (includes resends).
> > > ---
> > >  drivers/net/wireless/mac80211_hwsim.c | 129 +++++++++++++++++++++++++-
> > >  drivers/net/wireless/mac80211_hwsim.h |   3 +
> > >  2 files changed, 131 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/net/wireless/mac80211_hwsim.c b/drivers/net/wireless/mac80211_hwsim.c
> > > index 4cc4eaf80b14..65868f28a00f 100644
> > > --- a/drivers/net/wireless/mac80211_hwsim.c
> > > +++ b/drivers/net/wireless/mac80211_hwsim.c
> > > @@ -719,6 +719,9 @@ struct mac80211_hwsim_data {
> > >       /* RSSI in rx status of the receiver */
> > >       int rx_rssi;
> > >
> > > +     /* only used when pmsr capability is supplied */
> > > +     struct cfg80211_pmsr_capabilities pmsr_capa;
> > > +
> > >       struct mac80211_hwsim_link_data link_data[IEEE80211_MLD_MAX_NUM_LINKS];
> > >  };
> > >
> > > @@ -760,6 +763,34 @@ static const struct genl_multicast_group hwsim_mcgrps[] = {
> > >
> > >  /* MAC80211_HWSIM netlink policy */
> > >
> > > +static const struct nla_policy
> > > +hwsim_ftm_capa_policy[NL80211_PMSR_FTM_CAPA_ATTR_MAX + 1] = {
> > > +     [NL80211_PMSR_FTM_CAPA_ATTR_ASAP] = { .type = NLA_FLAG },
> > > +     [NL80211_PMSR_FTM_CAPA_ATTR_NON_ASAP] = { .type = NLA_FLAG },
> > > +     [NL80211_PMSR_FTM_CAPA_ATTR_REQ_LCI] = { .type = NLA_FLAG },
> > > +     [NL80211_PMSR_FTM_CAPA_ATTR_REQ_CIVICLOC] = { .type = NLA_FLAG },
> > > +     [NL80211_PMSR_FTM_CAPA_ATTR_PREAMBLES] = { .type = NLA_U32 },
> > > +     [NL80211_PMSR_FTM_CAPA_ATTR_BANDWIDTHS] = { .type = NLA_U32 },
> > > +     [NL80211_PMSR_FTM_CAPA_ATTR_MAX_BURSTS_EXPONENT] = NLA_POLICY_MAX(NLA_U8, 15),
> > > +     [NL80211_PMSR_FTM_CAPA_ATTR_MAX_FTMS_PER_BURST] = NLA_POLICY_MAX(NLA_U8, 31),
> > > +     [NL80211_PMSR_FTM_CAPA_ATTR_TRIGGER_BASED] = { .type = NLA_FLAG },
> > > +     [NL80211_PMSR_FTM_CAPA_ATTR_NON_TRIGGER_BASED] = { .type = NLA_FLAG },
> > > +};
> > > +
> > > +static const struct nla_policy
> > > +hwsim_pmsr_capa_type_policy[NL80211_PMSR_TYPE_MAX + 1] = {
> > > +     [NL80211_PMSR_TYPE_FTM] = NLA_POLICY_NESTED(hwsim_ftm_capa_policy),
> > > +};
> > > +
> > > +static const struct nla_policy
> > > +hwsim_pmsr_capa_policy[NL80211_PMSR_ATTR_MAX + 1] = {
> > > +     [NL80211_PMSR_ATTR_MAX_PEERS] = { .type = NLA_U32 },
> > > +     [NL80211_PMSR_ATTR_REPORT_AP_TSF] = { .type = NLA_FLAG },
> > > +     [NL80211_PMSR_ATTR_RANDOMIZE_MAC_ADDR] = { .type = NLA_FLAG },
> > > +     [NL80211_PMSR_ATTR_TYPE_CAPA] = NLA_POLICY_NESTED(hwsim_pmsr_capa_type_policy),
> > > +     [NL80211_PMSR_ATTR_PEERS] = { .type = NLA_REJECT }, // only for request.
> > > +};
> > > +
> > >  static const struct nla_policy hwsim_genl_policy[HWSIM_ATTR_MAX + 1] = {
> > >       [HWSIM_ATTR_ADDR_RECEIVER] = NLA_POLICY_ETH_ADDR_COMPAT,
> > >       [HWSIM_ATTR_ADDR_TRANSMITTER] = NLA_POLICY_ETH_ADDR_COMPAT,
> > > @@ -788,6 +819,7 @@ static const struct nla_policy hwsim_genl_policy[HWSIM_ATTR_MAX + 1] = {
> > >       [HWSIM_ATTR_IFTYPE_SUPPORT] = { .type = NLA_U32 },
> > >       [HWSIM_ATTR_CIPHER_SUPPORT] = { .type = NLA_BINARY },
> > >       [HWSIM_ATTR_MLO_SUPPORT] = { .type = NLA_FLAG },
> > > +     [HWSIM_ATTR_PMSR_SUPPORT] = NLA_POLICY_NESTED(hwsim_pmsr_capa_policy),
> > >  };
> > >
> > >  #if IS_REACHABLE(CONFIG_VIRTIO)
> > > @@ -3186,6 +3218,7 @@ struct hwsim_new_radio_params {
> > >       u32 *ciphers;
> > >       u8 n_ciphers;
> > >       bool mlo;
> > > +     const struct cfg80211_pmsr_capabilities *pmsr_capa;
> > >  };
> > >
> > >  static void hwsim_mcast_config_msg(struct sk_buff *mcast_skb,
> > > @@ -3260,7 +3293,7 @@ static int append_radio_msg(struct sk_buff *skb, int id,
> > >                       return ret;
> > >       }
> > >
> > > -     return 0;
> > > +     return ret;
> > >  }
> > >
> > >  static void hwsim_mcast_new_radio(int id, struct genl_info *info,
> > > @@ -4445,6 +4478,7 @@ static int mac80211_hwsim_new_radio(struct genl_info *info,
> > >                             NL80211_EXT_FEATURE_MULTICAST_REGISTRATIONS);
> > >       wiphy_ext_feature_set(hw->wiphy,
> > >                             NL80211_EXT_FEATURE_BEACON_RATE_LEGACY);
> > > +     wiphy_ext_feature_set(hw->wiphy, NL80211_EXT_FEATURE_ENABLE_FTM_RESPONDER);
> > >
> > >       hw->wiphy->interface_modes = param->iftypes;
> > >
> > > @@ -4606,6 +4640,11 @@ static int mac80211_hwsim_new_radio(struct genl_info *info,
> > >                                   data->debugfs,
> > >                                   data, &hwsim_simulate_radar);
> > >
> > > +     if (param->pmsr_capa) {
> > > +             data->pmsr_capa = *param->pmsr_capa;
> > > +             hw->wiphy->pmsr_capa = &data->pmsr_capa;
> > > +     }
> > > +
> > >       spin_lock_bh(&hwsim_radio_lock);
> > >       err = rhashtable_insert_fast(&hwsim_radios_rht, &data->rht,
> > >                                    hwsim_rht_params);
> > > @@ -4715,6 +4754,7 @@ static int mac80211_hwsim_get_radio(struct sk_buff *skb,
> > >       param.regd = data->regd;
> > >       param.channels = data->channels;
> > >       param.hwname = wiphy_name(data->hw->wiphy);
> > > +     param.pmsr_capa = &data->pmsr_capa;
> > >
> > >       res = append_radio_msg(skb, data->idx, &param);
> > >       if (res < 0)
> > > @@ -5053,6 +5093,77 @@ static bool hwsim_known_ciphers(const u32 *ciphers, int n_ciphers)
> > >       return true;
> > >  }
> > >
> > > +static int parse_ftm_capa(const struct nlattr *ftm_capa, struct cfg80211_pmsr_capabilities *out,
> > > +                       struct genl_info *info)
> > > +{
> > > +     struct nlattr *tb[NL80211_PMSR_FTM_CAPA_ATTR_MAX + 1];
> > > +     int ret = nla_parse_nested(tb, NL80211_PMSR_FTM_CAPA_ATTR_MAX,
> > > +                                ftm_capa, hwsim_ftm_capa_policy, NULL);
> >
> > I would suggest to split declaration and assignment here. It breaks the
> > RCT principle and it is more likely to overlook "nla_parse_nested" call.
> > I think it would improve the readability when we know that the parsing
> > function can return an error.
> 
> Thank you for the review, but what's the RCT principle?
> I've searched Kernel documentation and also googled it but I couldn't
> find a good match.
> Could you elaborate on the details?
> Most of your comments are related to the RCT, so I'd like to
> understand what it is.
>

RCT stands for "reverse christmas tree" order of declaration.
That means the longest declaration should go first and the shortest last.
For example:

struct very_long_structure_name *ptr;
int abc, defgh, othername;
long ret_code = 0;
u32 a, b, c;
u8 i;

As far as I know, it is a good practice of coding style in networking.

Thanks,
Michal

> >
> > > +
> > > +     if (ret) {
> > > +             NL_SET_ERR_MSG_ATTR(info->extack, ftm_capa, "malformed FTM capability");
> > > +             return -EINVAL;
> > > +     }
> > > +
> > > +     out->ftm.supported = 1;
> > > +     if (tb[NL80211_PMSR_FTM_CAPA_ATTR_PREAMBLES])
> > > +             out->ftm.preambles = nla_get_u32(tb[NL80211_PMSR_FTM_CAPA_ATTR_PREAMBLES]);
> > > +     if (tb[NL80211_PMSR_FTM_CAPA_ATTR_BANDWIDTHS])
> > > +             out->ftm.bandwidths = nla_get_u32(tb[NL80211_PMSR_FTM_CAPA_ATTR_BANDWIDTHS]);
> > > +     if (tb[NL80211_PMSR_FTM_CAPA_ATTR_MAX_BURSTS_EXPONENT])
> > > +             out->ftm.max_bursts_exponent =
> > > +                     nla_get_u8(tb[NL80211_PMSR_FTM_CAPA_ATTR_MAX_BURSTS_EXPONENT]);
> > > +     if (tb[NL80211_PMSR_FTM_CAPA_ATTR_MAX_FTMS_PER_BURST])
> > > +             out->ftm.max_ftms_per_burst =
> > > +                     nla_get_u8(tb[NL80211_PMSR_FTM_CAPA_ATTR_MAX_FTMS_PER_BURST]);
> > > +     out->ftm.asap = !!tb[NL80211_PMSR_FTM_CAPA_ATTR_ASAP];
> > > +     out->ftm.non_asap = !!tb[NL80211_PMSR_FTM_CAPA_ATTR_NON_ASAP];
> > > +     out->ftm.request_lci = !!tb[NL80211_PMSR_FTM_CAPA_ATTR_REQ_LCI];
> > > +     out->ftm.request_civicloc = !!tb[NL80211_PMSR_FTM_CAPA_ATTR_REQ_CIVICLOC];
> > > +     out->ftm.trigger_based = !!tb[NL80211_PMSR_FTM_CAPA_ATTR_TRIGGER_BASED];
> > > +     out->ftm.non_trigger_based = !!tb[NL80211_PMSR_FTM_CAPA_ATTR_NON_TRIGGER_BASED];
> > > +
> > > +     return 0;
> > > +}
> > > +
> > > +static int parse_pmsr_capa(const struct nlattr *pmsr_capa, struct cfg80211_pmsr_capabilities *out,
> > > +                        struct genl_info *info)
> > > +{
> > > +     struct nlattr *tb[NL80211_PMSR_ATTR_MAX + 1];
> > > +     struct nlattr *nla;
> > > +     int size;
> > > +     int ret = nla_parse_nested(tb, NL80211_PMSR_ATTR_MAX, pmsr_capa,
> > > +                                hwsim_pmsr_capa_policy, NULL);
> >
> > Ditto.
> >
> > > +
> > > +     if (ret) {
> > > +             NL_SET_ERR_MSG_ATTR(info->extack, pmsr_capa, "malformed PMSR capability");
> > > +             return -EINVAL;
> > > +     }
> > > +
> > > +     if (tb[NL80211_PMSR_ATTR_MAX_PEERS])
> > > +             out->max_peers = nla_get_u32(tb[NL80211_PMSR_ATTR_MAX_PEERS]);
> > > +     out->report_ap_tsf = !!tb[NL80211_PMSR_ATTR_REPORT_AP_TSF];
> > > +     out->randomize_mac_addr = !!tb[NL80211_PMSR_ATTR_RANDOMIZE_MAC_ADDR];
> > > +
> > > +     if (!tb[NL80211_PMSR_ATTR_TYPE_CAPA]) {
> > > +             NL_SET_ERR_MSG_ATTR(info->extack, tb[NL80211_PMSR_ATTR_TYPE_CAPA],
> > > +                                 "malformed PMSR type");
> > > +             return -EINVAL;
> > > +     }
> > > +
> > > +     nla_for_each_nested(nla, tb[NL80211_PMSR_ATTR_TYPE_CAPA], size) {
> > > +             switch (nla_type(nla)) {
> > > +             case NL80211_PMSR_TYPE_FTM:
> > > +                     parse_ftm_capa(nla, out, info);
> > > +                     break;
> > > +             default:
> > > +                     NL_SET_ERR_MSG_ATTR(info->extack, nla, "unsupported measurement type");
> > > +                     return -EINVAL;
> > > +             }
> > > +     }
> > > +     return 0;
> > > +}
> > > +
> > >  static int hwsim_new_radio_nl(struct sk_buff *msg, struct genl_info *info)
> > >  {
> > >       struct hwsim_new_radio_params param = { 0 };
> > > @@ -5173,8 +5284,24 @@ static int hwsim_new_radio_nl(struct sk_buff *msg, struct genl_info *info)
> > >               param.hwname = hwname;
> > >       }
> > >
> > > +     if (info->attrs[HWSIM_ATTR_PMSR_SUPPORT]) {
> > > +             struct cfg80211_pmsr_capabilities *pmsr_capa =
> > > +                     kmalloc(sizeof(*pmsr_capa), GFP_KERNEL);
> >
> > Missing empty line after variable definition.
> > BTW, would it not be better to split "pmsr_capa" declaration and
> > "kmalloc"? For example:
> >
> >                 struct cfg80211_pmsr_capabilities *pmsr_capa;
> >
> >                 pmsr_capa = kmalloc(sizeof(*pmsr_capa), GFP_KERNEL);
> >                 if (!pmsr_capa) {
> >
> > I think it would be more readable and you would not have to break the
> > line. Also, in the current version it seems more likely that the memory
> > allocation will be overlooked.
> >
> > > +             if (!pmsr_capa) {
> > > +                     ret = -ENOMEM;
> > > +                     goto out_free;
> > > +             }
> > > +             ret = parse_pmsr_capa(info->attrs[HWSIM_ATTR_PMSR_SUPPORT], pmsr_capa, info);
> > > +             if (ret)
> > > +                     goto out_free;
> > > +             param.pmsr_capa = pmsr_capa;
> > > +     }
> > > +
> > >       ret = mac80211_hwsim_new_radio(info, &param);
> > > +
> > > +out_free:
> > >       kfree(hwname);
> > > +     kfree(param.pmsr_capa);
> > >       return ret;
> > >  }
> > >
> > > diff --git a/drivers/net/wireless/mac80211_hwsim.h b/drivers/net/wireless/mac80211_hwsim.h
> > > index 527799b2de0f..d10fa7f4853b 100644
> > > --- a/drivers/net/wireless/mac80211_hwsim.h
> > > +++ b/drivers/net/wireless/mac80211_hwsim.h
> > > @@ -142,6 +142,8 @@ enum {
> > >   * @HWSIM_ATTR_CIPHER_SUPPORT: u32 array of supported cipher types
> > >   * @HWSIM_ATTR_MLO_SUPPORT: claim MLO support (exact parameters TBD) for
> > >   *   the new radio
> > > + * @HWSIM_ATTR_PMSR_SUPPORT: nested attribute used with %HWSIM_CMD_CREATE_RADIO
> > > + *   to provide peer measurement capabilities. (nl80211_peer_measurement_attrs)
> > >   * @__HWSIM_ATTR_MAX: enum limit
> > >   */
> > >
> > > @@ -173,6 +175,7 @@ enum {
> > >       HWSIM_ATTR_IFTYPE_SUPPORT,
> > >       HWSIM_ATTR_CIPHER_SUPPORT,
> > >       HWSIM_ATTR_MLO_SUPPORT,
> > > +     HWSIM_ATTR_PMSR_SUPPORT,
> > >       __HWSIM_ATTR_MAX,
> > >  };
> > >  #define HWSIM_ATTR_MAX (__HWSIM_ATTR_MAX - 1)
> > > --
> > > 2.40.0.rc1.284.g88254d51c5-goog
> > >
> 
> 
> 
> -- 
> Jaewan Kim (김재완) | Software Engineer in Google Korea |
> jaewan@...gle.com | +82-10-2781-5078

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