From patchwork Sat Feb 3 22:35:13 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Samuel Thibault X-Patchwork-Id: 13544380 X-Patchwork-Delegate: kuba@kernel.org Received: from sonata.ens-lyon.org (sonata.ens-lyon.org [140.77.166.138]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7597212E68; Sat, 3 Feb 2024 22:43:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=140.77.166.138 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707000187; cv=none; b=ka+ZHxx2iG3zLs0+AlF6NR0qUeLwrhuPLgf00scoUeGJ6jbgk8sYuNomUvZbmITtTWy+BEWKpS0tazXc2OxTadQqn54lbhX+oBU+yheb3XlxPsZXshr9WruF0c6iec7HYTPOPboEJWEmYuSbNtGavuy2mkEy71NpHwyQCAaA1UM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707000187; c=relaxed/simple; bh=hVfYZuMJypX8SO8Q0Mz5apUsGqZEhj917+dlLvHNxhM=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition; b=utKkSMz5L1WI/+6G0WPu76tNmyYdbS2qgRE0blbCvurNoAQCxOWowQEG2EA/zmiPQ+qiKHY8TVAbHL0zqs1j/zccv2CL5PrTcsFmG5e8iL0ATNrwlCs4aasS1vUHefcBvUXsldWf2/8bNsxAu7IOjgrPJFiSgZi7YMjxXfmCQu4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ens-lyon.org; spf=pass smtp.mailfrom=bounce.ens-lyon.org; arc=none smtp.client-ip=140.77.166.138 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ens-lyon.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bounce.ens-lyon.org Received: from localhost (localhost [127.0.0.1]) by sonata.ens-lyon.org (Postfix) with ESMTP id D02BAA02B7; Sat, 3 Feb 2024 23:35:14 +0100 (CET) Received: from sonata.ens-lyon.org ([127.0.0.1]) by localhost (sonata.ens-lyon.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ibr8YHfAeCVX; Sat, 3 Feb 2024 23:35:14 +0100 (CET) Received: from begin (aamiens-653-1-111-57.w83-192.abo.wanadoo.fr [83.192.234.57]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by sonata.ens-lyon.org (Postfix) with ESMTPSA id 399BEA022A; Sat, 3 Feb 2024 23:35:14 +0100 (CET) Received: from samy by begin with local (Exim 4.97) (envelope-from ) id 1rWObR-00000002MC2-3T4p; Sat, 03 Feb 2024 23:35:13 +0100 Date: Sat, 3 Feb 2024 23:35:13 +0100 From: Samuel Thibault To: James Chapman , tparkin@katalix.com, edumazet@google.com, gnault@redhat.com Cc: davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, corbet@lwn.net, netdev@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCHv3] PPPoL2TP: Add more code snippets Message-ID: <20240203223513.f2nfgaamgffz6dno@begin> Mail-Followup-To: Samuel Thibault , James Chapman , tparkin@katalix.com, edumazet@google.com, gnault@redhat.com, davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, corbet@lwn.net, netdev@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline User-Agent: NeoMutt/20170609 (1.8.3) X-Patchwork-Delegate: kuba@kernel.org The existing documentation was not telling that one has to create a PPP channel and a PPP interface to get PPPoL2TP data offloading working. Also, tunnel switching was not mentioned, so that people were thinking it was not supported, while it actually is. Signed-off-by: Samuel Thibault --- Difference from v1: - follow kernel coding style - check for failures - also mention netlink and ip for configuring the link - fix bridging channels Difference from v2: - fix text alignment Documentation/networking/l2tp.rst | 99 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 95 insertions(+), 4 deletions(-) --- a/Documentation/networking/l2tp.rst +++ b/Documentation/networking/l2tp.rst @@ -387,11 +387,16 @@ Sample userspace code: - Create session PPPoX data socket:: struct sockaddr_pppol2tp sax; - int fd; + int session_fd; + int ret; /* Note, the tunnel socket must be bound already, else it * will not be ready */ + session_fd = socket(AF_PPPOX, SOCK_DGRAM, PX_PROTO_OL2TP); + if (session_fd < 0) + return -errno; + sax.sa_family = AF_PPPOX; sax.sa_protocol = PX_PROTO_OL2TP; sax.pppol2tp.fd = tunnel_fd; @@ -406,11 +411,97 @@ Sample userspace code: /* session_fd is the fd of the session's PPPoL2TP socket. * tunnel_fd is the fd of the tunnel UDP / L2TPIP socket. */ - fd = connect(session_fd, (struct sockaddr *)&sax, sizeof(sax)); - if (fd < 0 ) { + ret = connect(session_fd, (struct sockaddr *)&sax, sizeof(sax)); + if (ret < 0 ) { + close(session_fd); + return -errno; + } + + return session_fd; + +L2TP control packets will still be available for read on `tunnel_fd`. + + - Create PPP channel:: + + int chindx; + int ppp_chan_fd; + + ret = ioctl(session_fd, PPPIOCGCHAN, &chindx); + if (ret < 0) + return -errno; + + ppp_chan_fd = open("/dev/ppp", O_RDWR); + if (ppp_chan_fd < 0) + return -errno; + + ret = ioctl(ppp_chan_fd, PPPIOCATTCHAN, &chindx); + if (ret < 0) { + close(ppp_chan_fd); + return -errno; + } + + return ppp_chan_fd; + +LCP PPP frames will be available for read on `ppp_chan_fd`. + + - Create PPP interface:: + + int ppp_if_fd; + int ifunit = -1; + + ppp_if_fd = open("/dev/ppp", O_RDWR); + if (ppp_chan_fd < 0) + return -errno; + + ret = ioctl(ppp_if_fd, PPPIOCNEWUNIT, &ifunit); + if (ret < 0) { + close(ppp_if_fd); + return -errno; + } + + ret = ioctl(ppp_chan_fd, PPPIOCCONNECT, ifunit); + if (ret < 0) { + close(ppp_if_fd); + return -errno; + } + + return ppp_chan_fd; + +IPCP/IPv6CP PPP frames will be available for read on `ppp_if_fd`. + +The ppp interface can then be configured as usual with netlink's +RTM_NEWLINK, RTM_NEWADDR, RTM_NEWROUTE, or ioctl's SIOCSIFMTU, SIOCSIFADDR, +SIOCSIFDSTADDR, SIOCSIFNETMASK, SIOCSIFFLAGS, or with the `ip` command. + + - L2TP session bridging (also called L2TP tunnel switching or L2TP multihop) + is supported by bridging the ppp channels of the two L2TP sessions to be + bridged:: + + int chindx1; + int chindx2; + int ppp_chan_fd; + + ret = ioctl(session_fd1, PPPIOCGCHAN, &chindx1); + if (ret < 0) + return -errno; + + ret = ioctl(session_fd2, PPPIOCGCHAN, &chind2x); + if (ret < 0) + return -errno; + + ppp_chan_fd = open("/dev/ppp", O_RDWR); + ret = ioctl(ppp_chan_fd, PPPIOCATTCHAN, &chindx1); + if (ret < 0) { + close(ppp_chan_fd); return -errno; } - return 0; + + ret = ioctl(ppp_chan_fd, PPPIOCBRIDGECHAN, &chindx2); + close(ppp_chan_fd); + if (ret < 0) + return -errno; + +See more details for the PPP side in ppp_generic.rst. Old L2TPv2-only API -------------------