From patchwork Tue Apr 18 14:33:07 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Samuel Thibault X-Patchwork-Id: 13215775 X-Patchwork-Delegate: kuba@kernel.org 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 9F5AEC77B78 for ; Tue, 18 Apr 2023 14:33:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230307AbjDROdP (ORCPT ); Tue, 18 Apr 2023 10:33:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39712 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231384AbjDROdO (ORCPT ); Tue, 18 Apr 2023 10:33:14 -0400 Received: from sonata.ens-lyon.org (sonata.ens-lyon.org [140.77.166.138]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3ADED83FC; Tue, 18 Apr 2023 07:33:13 -0700 (PDT) Received: from localhost (localhost [127.0.0.1]) by sonata.ens-lyon.org (Postfix) with ESMTP id C82DA2018B; Tue, 18 Apr 2023 16:33:11 +0200 (CEST) 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 ggrempUKGqz6; Tue, 18 Apr 2023 16:33:11 +0200 (CEST) Received: from begin (unknown [109.190.253.11]) (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 95A4520181; Tue, 18 Apr 2023 16:33:11 +0200 (CEST) Received: from samy by begin with local (Exim 4.96) (envelope-from ) id 1pomOJ-00C9qp-0h; Tue, 18 Apr 2023 16:33:07 +0200 Date: Tue, 18 Apr 2023 16:33:07 +0200 From: Samuel Thibault To: James Chapman , tparkin@katalix.com, edumazet@google.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: [PATCHv2] PPPoL2TP: Add more code snippets Message-ID: <20230418143307.hth4yjkopy5se4md@begin> Mail-Followup-To: Samuel Thibault , James Chapman , tparkin@katalix.com, edumazet@google.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 MIME-Version: 1.0 Content-Disposition: inline User-Agent: NeoMutt/20170609 (1.8.3) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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 Documentation/networking/l2tp.rst | 97 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 93 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 +411,95 @@ 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 0; + + return ppp_chan_fd; + +Non-data 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; + +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; + } + + 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 -------------------