Message-ID: <20220824093547.16f05d15@xps-13>
Date:   Wed, 24 Aug 2022 09:35:47 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Alexander Aring <aahringo@...hat.com>
Cc:     Alexander Aring <alex.aring@...il.com>,
        Stefan Schmidt <stefan@...enfreihafen.org>,
        linux-wpan - ML <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>,
        Network Development <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>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH wpan-next 01/20] net: mac802154: Allow the creation of
 coordinator interfaces

Hi Alexander,

aahringo@...hat.com wrote on Tue, 23 Aug 2022 17:44:52 -0400:

> Hi,
> 
> On Tue, Aug 23, 2022 at 12:29 PM Miquel Raynal
> <miquel.raynal@...tlin.com> wrote:
> >
> > Hi Alexander,
> >
> > aahringo@...hat.com wrote on Tue, 23 Aug 2022 08:33:30 -0400:
> >  
> > > Hi,
> > >
> > > On Fri, Aug 19, 2022 at 1:11 PM Miquel Raynal <miquel.raynal@...tlin.com> wrote:  
> > > >
> > > > Hi Alexander,
> > > >
> > > > aahringo@...hat.com wrote on Tue, 5 Jul 2022 21:51:02 -0400:
> > > >  
> > > > > Hi,
> > > > >
> > > > > On Fri, Jul 1, 2022 at 10:36 AM 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 might be restrained and improved later.
> > > > > >
> > > > > > Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
> > > > > > ---
> > > > > >  net/mac802154/iface.c | 14 ++++++++------
> > > > > >  net/mac802154/rx.c    |  2 +-
> > > > > >  2 files changed, 9 insertions(+), 7 deletions(-)
> > > > > >
> > > > > > diff --git a/net/mac802154/iface.c b/net/mac802154/iface.c
> > > > > > index 500ed1b81250..7ac0c5685d3f 100644
> > > > > > --- a/net/mac802154/iface.c
> > > > > > +++ b/net/mac802154/iface.c
> > > > > > @@ -273,13 +273,13 @@ 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.
> > > > > > @@ -577,6 +577,7 @@ 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);
> > > > > > @@ -636,6 +637,7 @@ 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/rx.c b/net/mac802154/rx.c
> > > > > > index b8ce84618a55..39459d8d787a 100644
> > > > > > --- a/net/mac802154/rx.c
> > > > > > +++ b/net/mac802154/rx.c
> > > > > > @@ -203,7 +203,7 @@ __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 probably get why you are doing that, but first the overall design is
> > > > > working differently - means you should add an additional receive path
> > > > > for the special interface type.
> > > > >
> > > > > Also we "discovered" before that the receive path of node vs
> > > > > coordinator is different... Where is the different handling here? I
> > > > > don't see it, I see that NODE and COORD are the same now (because that
> > > > > is _currently_ everything else than monitor). This change is not
> > > > > enough and does "something" to handle in some way coordinator receive
> > > > > path but there are things missing.
> > > > >
> > > > > 1. Changing the address filters that it signals the transceiver it's
> > > > > acting as coordinator
> > > > > 2. We _should_ also have additional handling for whatever the
> > > > > additional handling what address filters are doing in mac802154
> > > > > _because_ there is hardware which doesn't have address filtering e.g.
> > > > > hwsim which depend that this is working in software like other
> > > > > transceiver hardware address filters.
> > > > >
> > > > > For the 2. one, I don't know if we do that even for NODE right or we
> > > > > just have the bare minimal support there... I don't assume that
> > > > > everything is working correctly here but what I want to see is a
> > > > > separate receive path for coordinators that people can send patches to
> > > > > fix it.  
> > > >
> > > > Yes, we do very little differently between the two modes, that's why I
> > > > took the easy way: just changing the condition. I really don't see what
> > > > I can currently add here, but I am fine changing the style to easily
> > > > show people where to add filters for such or such interface, but right
> > > > now both path will look very "identical", do we agree on that?  
> > >
> > > mostly yes, but there exists a difference and we should at least check
> > > if the node receive path violates the coordinator receive path and
> > > vice versa.
> > > Put it in a receive_path() function and then coord_receive_path(),
> > > node_receive_path() that calls the receive_path() and do the
> > > additional filtering for coordinators, etc.
> > >
> > > There should be a part in the standard about "third level filter rule
> > > if it's a coordinator".
> > > btw: this is because the address filter on the transceiver needs to
> > > have the "i am a coordinator" boolean set which is missing in this
> > > series. However it depends on the transceiver filtering level and the
> > > mac802154 receive path if we actually need to run such filtering or
> > > not.  
> >
> > I must be missing some information because I can't find any places
> > where what you suggest is described in the spec.
> >
> > I agree there are multiple filtering level so let's go through them one
> > by one (6.7.2 Reception and rejection):
> > - first level: is the checksum (FCS) valid?
> >         yes -> goto second level
> >         no -> drop
> > - second level: are we in promiscuous mode?
> >         yes -> forward to upper layers
> >         no -> goto second level (bis)
> > - second level (bis): are we scanning?
> >         yes -> goto scan filtering
> >         no -> goto third level
> > - scan filtering: is it a beacon?
> >         yes -> process the beacon
> >         no -> drop
> > - third level: is the frame valid? (type, source, destination, pan id,
> >   etc)
> >         yes -> forward to upper layers
> >         no -> drop
> >
> > But none of them, as you said, is dependent on the interface type.
> > There is no mention of a specific filtering operation to do in all
> > those cases when running in COORD mode. So I still don't get what
> > should be included in either node_receive_path() which should be
> > different than in coord_receive_path() for now.
> >
> > There are, however, two situations where the interface type has its
> > importance:
> > - Enhanced beacon requests with Enhanced beacon filter IE, which asks
> >   the receiving device to process/drop the request upon certain
> >   conditions (minimum LQI and/or randomness), as detailed in
> >   7.4.4.6 Enhanced Beacon Filter IE. But, as mentioned in
> >   7.5.9 Enhanced Beacon Request command: "The Enhanced Beacon Request
> >   command is optional for an FFD and an RFD", so this series was only
> >   targeting basic beaconing for now.
> > - In relaying mode, the destination address must not be validated
> >   because the message needs to be re-emitted. Indeed, a receiver in
> >   relaying mode may not be the recipient. This is also optional and out
> >   of the scope of this series.
> >
> > Right now I have the below diff, which clarifies the two path, without
> > too much changes in the current code because I don't really see why it
> > would be necessary. Unless you convince me otherwise or read the spec
> > differently than I do :) What do you think?
> >  
> 
> "Reception and rejection"
> 
> third-level filtering regarding "destination address" and if the
> device is "PAN coordinator".
> This is, in my opinion, what the coordinator boolean tells the
> transceiver to do on hardware when doing address filter there. You can
> also read that up in datasheets of transceivers as atf86rf233, search
> for I_AM_COORD.

Oh right, I now see what you mean!

> Whereas they use the word "PAN coordinator" not "coordinator", if they
> really make a difference there at this point..., if so then the kernel
> must know if the coordinator is a pan coordinator or coordinator
> because we need to set the address filter in kernel.

Yes we need to make a difference, you can have several coordinators but
a single PAN coordinator in a PAN. I think we can assume that the PAN
coordinator is the coordinator with no parent (association-wise). With
the addition of the association series, I can handle that, so I will
create the two path as you advise, add a comment about this additional
filter rule that we don't yet support, and finally after the
association series add another commit to make this filtering rule real.

> 
> > Thanks,
> > Miquèl
> >
> > ---
> >
> > --- a/net/mac802154/rx.c
> > +++ b/net/mac802154/rx.c
> > @@ -194,6 +194,7 @@ __ieee802154_rx_handle_packet(struct ieee802154_local *local,
> >         int ret;
> >         struct ieee802154_sub_if_data *sdata;
> >         struct ieee802154_hdr hdr;
> > +       bool iface_found = false;
> >
> >         ret = ieee802154_parse_frame_start(skb, &hdr);
> >         if (ret) {
> > @@ -203,18 +204,31 @@ __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;
> >
> >                 if (!ieee802154_sdata_running(sdata))
> >                         continue;
> >
> > +               iface_found = true;
> > +               break;
> > +       }
> > +
> > +       if (!iface_found) {
> > +               kfree_skb(skb);
> > +               return;
> > +       }
> > +
> > +       /* TBD: Additional filtering is possible on NODEs and/or COORDINATORs */
> > +       switch (sdata->wpan_dev.iftype) {
> > +       case NL802154_IFTYPE_COORD:
> > +       case NL802154_IFTYPE_NODE:
> >                 ieee802154_subif_frame(sdata, skb, &hdr);
> > -               skb = NULL;
> > +               break;
> > +       default:
> > +               kfree_skb(skb);
> >                 break;
> >         }  
> 
> Why do you remove the whole interface looping above and make it only
> run for one ?first found? ?

To reduce the indentation level.

> That code changes this behaviour and I do
> not know why.

The precedent code did:
for_each_iface() {
	if (not a node)
		continue;
	if (not running)
		continue;

	subif_frame();
	break;
}

That final break also elected only the first running node iface.
Otherwise it would mean that we allow the same skb to be consumed
twice, which is wrong IMHO?

> Move the switch case into the loop and do a different
> receive path if coord and node and do whatever differs from filtering
> and then call ieee802154_subif_frame().
> 
> - Alex
> 

Thanks,
Miquèl

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