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 X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE790C433E6 for ; Tue, 16 Feb 2021 10:38:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 682AA64DF0 for ; Tue, 16 Feb 2021 10:38:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230059AbhBPKia (ORCPT ); Tue, 16 Feb 2021 05:38:30 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:42662 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229725AbhBPKi2 (ORCPT ); Tue, 16 Feb 2021 05:38:28 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613471821; 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=8rs5zW1or0x3SgRQjoDUd0UE+g7JCYAEd7GiRX8HiGs=; b=ULSZG/PzL7HqlRgeSeYeVLwgZQXFgryKJoCgYoAPE7Cf1PuINHIhMFZqyj7G3FPTGdJ8M5 Dvhf7fJWet7ACNHP0Tm+IkIwklbHpnzbTWwK3rQFwgHZBhEOXdGyXaplBlZXtrfbYd4HhC FBHtweyiZHIfoGNt/lzPNyp/RtBm/ic= Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-257-h5hsufJWNLyThSDeNp7SFw-1; Tue, 16 Feb 2021 05:36:59 -0500 X-MC-Unique: h5hsufJWNLyThSDeNp7SFw-1 Received: by mail-ed1-f70.google.com with SMTP id dk21so194245edb.10 for ; Tue, 16 Feb 2021 02:36:59 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version:content-transfer-encoding; bh=8rs5zW1or0x3SgRQjoDUd0UE+g7JCYAEd7GiRX8HiGs=; b=C/ojh9zZdrbnJMYHpuMZPnrFbLXnd/dANC/fw8eeOtq/lmQOthLP2orBIdFEGZrNZd IroAhASegWI76S8XqHx+cRmx7J5AGO5k6AuofCMdjOM9RxjuT0l32SkvyPnXeGAts9jQ mfRP4yHbWGkWV3cJ25SyqEAoUhoQ+taJvORh+oTAbgb3CijQPsPW+L/JIam92cnnpZVw +dTu79njKLbGRU2GTeRn5sDO4Le9rne6m5/ngqrJcQgxKcKQK2B6gX5ovgi/dEXtcUbZ ZHkj2Bxuz7h0Mle/InZg4fkO/DJMaJQUc8yIGf0YUFMxhTAWCjq8NMeNdxqxFPvNEx5A Vm4Q== X-Gm-Message-State: AOAM531luYJZrALEPb5LAKQeAbkPBXwNfLxs+pIlwBEksWuheV9FN8x9 wFaoBLxXtytuxKNF87LGHso7+NHTOGXv7vufmbKHPsdVeDhckPVTqz4KBBPGAwFAZnfuAjUcIQr AnN99gw2oqLMn X-Received: by 2002:a17:906:54b:: with SMTP id k11mr18804559eja.495.1613471818123; Tue, 16 Feb 2021 02:36:58 -0800 (PST) X-Google-Smtp-Source: ABdhPJz6vHFODLJBF9abhWybbR0ngnRu1I7OKFSuPKOlnBmdqRflzF2uUISKl8pP/YmnNJfq0pWcbw== X-Received: by 2002:a17:906:54b:: with SMTP id k11mr18804534eja.495.1613471817826; Tue, 16 Feb 2021 02:36:57 -0800 (PST) Received: from alrua-x1.borgediget.toke.dk ([2a0c:4d80:42:443::2]) by smtp.gmail.com with ESMTPSA id hr3sm12383053ejc.41.2021.02.16.02.36.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Feb 2021 02:36:57 -0800 (PST) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 199C71805FA; Tue, 16 Feb 2021 11:36:57 +0100 (CET) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: John Fastabend , John Fastabend , =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= , Maciej Fijalkowski , daniel@iogearbox.net, ast@kernel.org, bpf@vger.kernel.org, netdev@vger.kernel.org Cc: andrii@kernel.org, magnus.karlsson@intel.com, ciara.loftus@intel.com Subject: Re: [PATCH bpf-next 1/3] libbpf: xsk: use bpf_link In-Reply-To: <602b0f54c05a6_3ed41208dc@john-XPS-13-9370.notmuch> References: <20210215154638.4627-1-maciej.fijalkowski@intel.com> <20210215154638.4627-2-maciej.fijalkowski@intel.com> <87eehhcl9x.fsf@toke.dk> <602ad80c566ea_3ed4120871@john-XPS-13-9370.notmuch> <8735xxc8pf.fsf@toke.dk> <602b0f54c05a6_3ed41208dc@john-XPS-13-9370.notmuch> X-Clacks-Overhead: GNU Terry Pratchett Date: Tue, 16 Feb 2021 11:36:57 +0100 Message-ID: <87pn10b8om.fsf@toke.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org John Fastabend writes: > Toke H=C3=B8iland-J=C3=B8rgensen wrote: >> John Fastabend writes: >>=20 >> >> > However, in libxdp we can solve the original problem in a different= way, >> >> > and in fact I already suggested to Magnus that we should do this (s= ee >> >> > [1]); so one way forward could be to address it during the merge in >> >> > libxdp? It should be possible to address the original issue (two >> >> > instances of xdpsock breaking each other when they exit), but >> >> > applications will still need to do an explicit unload operation bef= ore >> >> > exiting (i.e., the automatic detach on bpf_link fd closure will take >> >> > more work, and likely require extending the bpf_link kernel support= )... >> >> > >> >>=20 >> >> I'd say it's depending on the libbpf 1.0/libxdp merge timeframe. If >> >> we're months ahead, then I'd really like to see this in libbpf until = the >> >> merge. However, I'll leave that for Magnus/you to decide! >> > >> > Did I miss some thread? What does this mean libbpf 1.0/libxdp merge? >>=20 >> The idea is to keep libbpf focused on bpf, and move the AF_XDP stuff to >> libxdp (so the socket stuff in xsk.h). We're adding the existing code >> wholesale, and keeping API compatibility during the move, so all that's >> needed is adding -lxdp when compiling. And obviously the existing libbpf >> code isn't going anywhere until such a time as there's a general >> backwards compatibility-breaking deprecation in libbpf (which I believe >> Andrii is planning to do in an upcoming and as-of-yet unannounced v1.0 >> release). > > OK, I would like to keep the basic XDP pieces in libbpf though. For examp= le > bpf_program__attach_xdp(). This way we don't have one lib to attach > everything, but XDP. The details are still TDB; for now, we're just merging in the XSK code to the libxdp repo. I expect Andrii to announce his plans for the rest soonish. I wouldn't expect basic things like that to go away, though :) >>=20 >> While integrating the XSK code into libxdp we're trying to make it >> compatible with the rest of the library (i.e., multi-prog). Hence my >> preference to avoid introducing something that makes this harder :) >>=20 >> -Toke >>=20 > > OK that makes sense to me thanks. But, I'm missing something (maybe its > obvious to everyone else?). > > When you load an XDP program you should get a reference to it. And then > XDP program should never be unloaded until that id is removed right? It > may or may not have an xsk map. Why does adding/removing programs from > an associated map have any impact on the XDP program? That seems like > the buggy part to me. No other map behaves this way as far as I can > tell. Now if the program with the XDP reference closes without pinning > the map or otherwise doing something with it, sure the map gets destroyed > and any xsk sockets are lost. The original bug comes from the XSK code abstracting away the fact that an AF_XDP socket needs an XDP program on the interface to work; so if none exists, the library will just load a program that redirects into the socket. Which breaks since the xdpsock example application is trying to be nice and clean up after itself, by removing the XDP program when it's done with the socket, thus breaking any other programs using that XDP program. So this patch introduces proper synchronisation on both add and remove of the XDP program... -Toke