Message-ID: <CAK-6q+gCKU0htSwjAZ2vjekq-wD0+8tUc6zXHv_Y+MGb2VkM+Q@mail.gmail.com>
Date:   Sun, 23 Oct 2022 19:26:15 -0400
From:   Alexander Aring <aahringo@...hat.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Alexander Aring <alex.aring@...il.com>,
        Stefan Schmidt <stefan@...enfreihafen.org>,
        linux-wpan@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org,
        David Girault <david.girault@...vo.com>,
        Romuald Despres <romuald.despres@...vo.com>,
        Frederic Blain <frederic.blain@...vo.com>,
        Nicolas Schodet <nico@...fr.eu.org>,
        Guilhem Imberton <guilhem.imberton@...vo.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH wpan-next] mac802154: Allow the creation of coordinator interfaces

Hi,

On Sun, Oct 23, 2022 at 7:13 PM Alexander Aring <aahringo@...hat.com> wrote:
>
> Hi,
>
> On Wed, Oct 19, 2022 at 5:52 AM Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> >
> > Hi Alexander,
> >
> > aahringo@...hat.com wrote on Tue, 18 Oct 2022 19:57:19 -0400:
> >
> > > Hi,
> > >
> > > On Tue, Oct 18, 2022 at 2:36 PM Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> > > >
> > > > As a first strep in introducing proper PAN management and association,
> > > > we need to be able to create coordinator interfaces which might act as
> > > > coordinator or PAN coordinator.
> > > >
> > > > Hence, let's add the minimum support to allow the creation of these
> > > > interfaces. This support will be improved later, in particular regarding
> > > > the filtering.
> > > >
> > > > Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
> > > > ---
> > > >  net/mac802154/iface.c | 14 ++++++++------
> > > >  net/mac802154/main.c  |  2 ++
> > > >  net/mac802154/rx.c    | 11 +++++++----
> > > >  3 files changed, 17 insertions(+), 10 deletions(-)
> > > >
> > > > diff --git a/net/mac802154/iface.c b/net/mac802154/iface.c
> > > > index d9b50884d34e..682249f3369b 100644
> > > > --- a/net/mac802154/iface.c
> > > > +++ b/net/mac802154/iface.c
> > > > @@ -262,13 +262,13 @@ ieee802154_check_concurrent_iface(struct ieee802154_sub_if_data *sdata,
> > > >                 if (nsdata != sdata && ieee802154_sdata_running(nsdata)) {
> > > >                         int ret;
> > > >
> > > > -                       /* TODO currently we don't support multiple node types
> > > > -                        * we need to run skb_clone at rx path. Check if there
> > > > -                        * exist really an use case if we need to support
> > > > -                        * multiple node types at the same time.
> > > > +                       /* TODO currently we don't support multiple node/coord
> > > > +                        * types we need to run skb_clone at rx path. Check if
> > > > +                        * there exist really an use case if we need to support
> > > > +                        * multiple node/coord types at the same time.
> > > >                          */
> > > > -                       if (wpan_dev->iftype == NL802154_IFTYPE_NODE &&
> > > > -                           nsdata->wpan_dev.iftype == NL802154_IFTYPE_NODE)
> > > > +                       if (wpan_dev->iftype != NL802154_IFTYPE_MONITOR &&
> > > > +                           nsdata->wpan_dev.iftype != NL802154_IFTYPE_MONITOR)
> > > >                                 return -EBUSY;
> > > >
> > > >                         /* check all phy mac sublayer settings are the same.
> > > > @@ -565,6 +565,7 @@ ieee802154_setup_sdata(struct ieee802154_sub_if_data *sdata,
> > > >         wpan_dev->short_addr = cpu_to_le16(IEEE802154_ADDR_BROADCAST);
> > > >
> > > >         switch (type) {
> > > > +       case NL802154_IFTYPE_COORD:
> > > >         case NL802154_IFTYPE_NODE:
> > > >                 ieee802154_be64_to_le64(&wpan_dev->extended_addr,
> > > >                                         sdata->dev->dev_addr);
> > > > @@ -624,6 +625,7 @@ ieee802154_if_add(struct ieee802154_local *local, const char *name,
> > > >         ieee802154_le64_to_be64(ndev->perm_addr,
> > > >                                 &local->hw.phy->perm_extended_addr);
> > > >         switch (type) {
> > > > +       case NL802154_IFTYPE_COORD:
> > > >         case NL802154_IFTYPE_NODE:
> > > >                 ndev->type = ARPHRD_IEEE802154;
> > > >                 if (ieee802154_is_valid_extended_unicast_addr(extended_addr)) {
> > > > diff --git a/net/mac802154/main.c b/net/mac802154/main.c
> > > > index 40fab08df24b..d03ecb747afc 100644
> > > > --- a/net/mac802154/main.c
> > > > +++ b/net/mac802154/main.c
> > > > @@ -219,6 +219,8 @@ int ieee802154_register_hw(struct ieee802154_hw *hw)
> > > >
> > > >         if (hw->flags & IEEE802154_HW_PROMISCUOUS)
> > > >                 local->phy->supported.iftypes |= BIT(NL802154_IFTYPE_MONITOR);
> > > > +       else
> > > > +               local->phy->supported.iftypes &= ~BIT(NL802154_IFTYPE_COORD);
> > > >
> > >
> > > So this means if somebody in the driver sets iftype COORD is supported
> > > but then IEEE802154_HW_PROMISCUOUS is not supported it will not
> > > support COORD?
> > >
> > > Why is IEEE802154_HW_PROMISCUOUS required for COORD iftype? I thought
> > > IEEE802154_HW_PROMISCUOUS is required to do a scan?
> >
> > You are totally right this is inconsistent, I'll drop the else block
> > entirely. The fact that HW_PROMISCUOUS is supported when starting a
> > scan is handled by the -EOPNOTSUPP return code from
> > drv_set_promiscuous_mode() called by drv_start() in
> > mac802154_trigger_scan().
> >
> > However I need your input on the following topic: in my branch I
> > have somewhere a patch adding IFTYPE_COORD to the list of
> > phy->supported.iftypes in each individual driver. But right now, if we
> > drop the promiscuous constraint as you suggest, I don't see anymore the
> > need for setting this as a per-driver value.
> >
> > Should we make the possibility to create IFTYPE_COORD interfaces the
> > default instead, something like this?
> >
> > --- a/net/mac802154/main.c
> > +++ b/net/mac802154/main.c
> > @@ -118,7 +118,7 @@ ieee802154_alloc_hw(size_t priv_data_len, const struct ieee802154_ops *ops)
> >         phy->supported.lbt = NL802154_SUPPORTED_BOOL_FALSE;
> >
> >         /* always supported */
> > -       phy->supported.iftypes = BIT(NL802154_IFTYPE_NODE);
> > +       phy->supported.iftypes = BIT(NL802154_IFTYPE_NODE) | BIT(NL802154_IFTYPE_COORD);
> >
>
> okay.
>
> > > >         rc = wpan_phy_register(local->phy);
> > > >         if (rc < 0)
> > > > diff --git a/net/mac802154/rx.c b/net/mac802154/rx.c
> > > > index 2ae23a2f4a09..aca348d7834b 100644
> > > > --- a/net/mac802154/rx.c
> > > > +++ b/net/mac802154/rx.c
> > > > @@ -208,6 +208,7 @@ __ieee802154_rx_handle_packet(struct
> > > > ieee802154_local *local, int ret;
> > > >         struct ieee802154_sub_if_data *sdata;
> > > >         struct ieee802154_hdr hdr;
> > > > +       struct sk_buff *skb2;
> > > >
> > > >         ret = ieee802154_parse_frame_start(skb, &hdr);
> > > >         if (ret) {
> > > > @@ -217,7 +218,7 @@ __ieee802154_rx_handle_packet(struct
> > > > ieee802154_local *local, }
> > > >
> > > >         list_for_each_entry_rcu(sdata, &local->interfaces, list) {
> > > > -               if (sdata->wpan_dev.iftype != NL802154_IFTYPE_NODE)
> > > > +               if (sdata->wpan_dev.iftype ==
> > > > NL802154_IFTYPE_MONITOR) continue;
> > >
> > > I guess this will work but I would like to see no logic about if it's
> > > not MONITOR it's NODE or COORD, because introducing others requires
> > > updating those again... however I think it's fine.
> >
> > Actually I don't get why we would not want this logic, it seem very
> > relevant to me. Do you want a helper instead and hide the condition
> > inside? Or something else? Or is it just fine for now?
> >
> > > I would like to see
> > > a different receive path for coord_rx() and node_rx(), but yea
> > > currently I guess they are mostly the same... in future I think they
> > > are required as PACKTE_HOST, etc. will be changed regarding pan
> > > coordinator or just coordinator (so far I understood).
> >
>
> yes, I think so too.
>
> > I agree it is tempting, but yeah, there is really very little changes
> > between the two, for me splitting the rx path would just darken the
> > code without bringing much...
> >
>
> ok.
>
> > About the way we handle the PAN coordinator role I have a couple of
> > questions:
> > - shall we consider only the PAN coordinator to be able to accept
> >   associations or is any coordinator in the PAN able to do it? (this is
> >   not clear to me)
>
> Me either, it sounds for me that coordinators are "leaves" and pan
> coordinators are not. It is like in IPv6 level it is a host or router.
>

In this case pan coordinators are able to accept associations only but
others can send associations.

We should talk about how the difference is here between a node
interface and a coordinator interface. For me a node interface is a
"mesh" 802.15.4 interface. Coordinators/Pan Coordinators build up star
topologies, or not? What I think about is maybe coord interfaces are
just pan coordinators. Node interfaces act at the beginning as a fully
mesh interface, but soon as you associate it with a pan coordinator it
will become what 802.15.4 says a coordinator. I think we don't need
any kind of iftype indicator for that.

I am not sure if there is really a difference between node and
coordinator, but pan coordinator should be a different interface. And
a coordinator is a node type but only when it's associated with a pan
coordinator. Somehow it needs to fit into the current infrastructure.

- Alex

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