From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 40921CCA47E for ; Tue, 7 Jun 2022 16:16:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344816AbiFGQQi (ORCPT ); Tue, 7 Jun 2022 12:16:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40210 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344804AbiFGQQh (ORCPT ); Tue, 7 Jun 2022 12:16:37 -0400 Received: from relay5-d.mail.gandi.net (relay5-d.mail.gandi.net [IPv6:2001:4b98:dc4:8::225]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 701A4101739; Tue, 7 Jun 2022 09:16:14 -0700 (PDT) Received: (Authenticated sender: miquel.raynal@bootlin.com) by mail.gandi.net (Postfix) with ESMTPSA id 45C9D1C000D; Tue, 7 Jun 2022 16:16:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1654618572; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ZkAbXoXs2t8ugzNXMaQPGeM/Hio1skCbepGCuzCcvq8=; b=bT6KFVzefthNneJOZl8xkCHji1l5Zdj785++E0Brf8YKQwn0d6bDo1pkl/PZZTbwDDubHj l3TDI4TaVPxxjSYrBrr3sg46UvL7WtKG09Gi1cAfr4UFxTv8LosEeHyhxMl0K8nMTso4jB n4GX0PVEeB9YRe2XK7sAy4Lx7U4RHo/RKrtDOQ0ZikzT1zZu5m9y5t9ZFYEFxkEfUCMzYH Hu5JWhFumTWtj/wI806sUrMay3awejAwhYEIPaY56zU95b8N2wHQtXbg3RzLPRLTiXa9NG +2zy012ZyN66XybvqfOkVsoVDOajM/NNk0F3GSuYaVDHnvfkg3Mxmxuy0Ym7Xw== Date: Tue, 7 Jun 2022 18:16:08 +0200 From: Miquel Raynal To: Alexander Aring Cc: Alexander Aring , Stefan Schmidt , linux-wpan - ML , "David S. Miller" , Jakub Kicinski , Paolo Abeni , Network Development , David Girault , Romuald Despres , Frederic Blain , Nicolas Schodet , Thomas Petazzoni Subject: Re: [PATCH wpan-next 1/6] net: ieee802154: Drop coordinator interface type Message-ID: <20220607181608.609429cb@xps-13> In-Reply-To: References: <20220603182143.692576-1-miquel.raynal@bootlin.com> <20220603182143.692576-2-miquel.raynal@bootlin.com> <20220606174319.0924f80d@xps-13> Organization: Bootlin X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Hi Alex, aahringo@redhat.com wrote on Mon, 6 Jun 2022 23:04:06 -0400: > Hi, >=20 > On Mon, Jun 6, 2022 at 11:43 AM Miquel Raynal = wrote: > > > > Hi Alexander, > > > > aahringo@redhat.com wrote on Fri, 3 Jun 2022 22:01:38 -0400: > > =20 > > > Hi, > > > > > > On Fri, Jun 3, 2022 at 2:34 PM Miquel Raynal wrote: =20 > > > > > > > > The current enum is wrong. A device can either be an RFD, an RFD-RX= , an > > > > RFD-TX or an FFD. If it is an FFD, it can also be a coordinator. Wh= ile > > > > defining a node type might make sense from a strict software point = of > > > > view, opposing node and coordinator seems meaningless in the ieee > > > > 802.15.4 world. As this enumeration is not used anywhere, let's just > > > > drop it. We will in a second time add a new "node type" enumeration > > > > which apply only to nodes, and does differentiates the type of devi= ces > > > > mentioned above. > > > > =20 > > > > > > First you cannot say if this is not used anywhere else. =20 > > > > Mmmh, that's tricky, I really don't see how that might be a > > problem because there is literally nowhere in the kernel that uses this > > type, besides ieee802154_setup_sdata() which would just BUG() if this > > type was to be used. So I assumed it was safe to be removed. > > =20 >=20 > this header is somehow half uapi where we copy it into some other > software e.g. wpan-tools as you noticed. >=20 > > > Second I have > > > a different opinion here that you cannot just "switch" the role from > > > RFD, FFD, whatever. =20 > > > > I agree with this, and that's why I don't understand this enum. > > > > A device can either be a NODE (an active device) or a MONITOR (a > > passive device) at a time. We can certainly switch from one to > > another at run time. > > > > A NODE can be either an RFD or an FFD. That is a static property which > > cannot change. > > > > However being a coordinator is just an additional property of a NODE > > which is of type FFD, and this can change over time. > > > > So I don't get what having a coordinator interface would bring. What > > was the idea behind its introduction then? > > =20 >=20 > There exists arguments which I have in my mind right now: >=20 > 1. frame parsing/address filter (which is somehow missing in your patches) >=20 > The parsing of frames is different from other types (just as monitor > interfaces). You will notice that setting up the address filter will > require a parameter if coordinator or not. I think this is something that I completely missed until now, can you point me to where/how this is expected to be done? I don't see anything wpan specific filtering implementation. What is expected on this area and is there code that I missed already? > Changing the address > filterung during runtime of an interface is somehow _not_ supported. > The reason is that the datasheets tell you to first set up an address > filter and then switch into receiving mode. Changing the address > filter during receive mode (start()/stop()) is not a specified > behaviour. Due to bus communication it also cannot be done atomically. > This might be avoidable but is a pain to synchronize if you really > depend on hw address filtering which we might do in future. It should > end in a different receiving path e.g. node_rx/monitor_rx. Got it. >=20 > 2. HardMAC transceivers >=20 > The add_interface() callback will be directly forwarded to the driver > and the driver will during the lifetime of this interface act as a > coordinator and not a mixed mode which can be disabled and enabled > anytime. I am not even sure if this can ever be handled in such a way > from hardmac transceivers, it might depend on the transceiver > interface but we should assume some strict "static" handling. Static > handling means here that the transceiver is unable to switch from > coordinator and vice versa after some initialization state. Okay. I just completely missed the "interface add" command. So your advice is to treat the "PAN coordinator" property as a static property for a given interface, which seems reasonable. For now I will assume the same treatment when adding the interface is required compared to a NODE, but if something comes to your mind, please let me know. By the way, is there a mechanism limiting the number of interfaces on a device? Should we prevent the introduction of a coordinator iface if there is a node iface active? > 3. coordinator (any $TYPE specific) userspace software >=20 > May the main argument. Some coordinator specific user space daemon > does specific type handling (e.g. hostapd) maybe because some library > is required. It is a pain to deal with changing roles during the > lifetime of an interface and synchronize user space software with it. > We should keep in mind that some of those handlings will maybe be > moved to user space instead of doing it in the kernel. I am fine with > the solution now, but keep in mind to offer such a possibility. >=20 > I think the above arguments are probably the same why wireless is > doing something similar and I would avoid running into issues or it's > really difficult to handle because you need to solve other Linux net > architecture handling at first. Yep. > > > You are mixing things here with "role in the network" and what the > > > transceiver capability (RFD, FFD) is, which are two different things.= =20 > > > > I don't think I am, however maybe our vision differ on what an > > interface should be. > > =20 > > > You should use those defines and the user needs to create a new > > > interface type and probably have a different extended address to act > > > as a coordinator. =20 > > > > Can't we just simply switch from coordinator to !coordinator (that's > > what I currently implemented)? Why would we need the user to create a > > new interface type *and* to provide a new address? > > > > Note that these are real questions that I am asking myself. I'm fine > > adapting my implementation, as long as I get the main idea. > > =20 >=20 > See above. That's okay for me. I will adapt my implementation to use the interface thing. In the mean time additional details about what a coordinator interface should do differently (above question) is welcome because this is not something I am really comfortable with. Thanks, Miqu=C3=A8l