docs: networking: convert l2tp.txt to ReST
- add SPDX header; - add a document title; - mark tables as such; - adjust identation, whitespaces and blank lines; - add to networking/index.rst. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
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Mauro Carvalho Chehab
David S. Miller
parent
9f04960660
commit
10ebb22137
@ -74,6 +74,7 @@ Contents:
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ipvlan
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ipvs-sysctl
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kcm
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l2tp
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.. only:: subproject and html
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@ -1,3 +1,9 @@
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.. SPDX-License-Identifier: GPL-2.0
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====
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L2TP
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====
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This document describes how to use the kernel's L2TP drivers to
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provide L2TP functionality. L2TP is a protocol that tunnels one or
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more sessions over an IP tunnel. It is commonly used for VPNs
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@ -121,14 +127,16 @@ Userspace may control behavior of the tunnel or session using
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setsockopt and ioctl on the PPPoX socket. The following socket
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options are supported:-
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DEBUG - bitmask of debug message categories. See below.
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SENDSEQ - 0 => don't send packets with sequence numbers
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1 => send packets with sequence numbers
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RECVSEQ - 0 => receive packet sequence numbers are optional
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1 => drop receive packets without sequence numbers
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LNSMODE - 0 => act as LAC.
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1 => act as LNS.
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REORDERTO - reorder timeout (in millisecs). If 0, don't try to reorder.
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========= ===========================================================
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DEBUG bitmask of debug message categories. See below.
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SENDSEQ - 0 => don't send packets with sequence numbers
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- 1 => send packets with sequence numbers
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RECVSEQ - 0 => receive packet sequence numbers are optional
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- 1 => drop receive packets without sequence numbers
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LNSMODE - 0 => act as LAC.
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- 1 => act as LNS.
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REORDERTO reorder timeout (in millisecs). If 0, don't try to reorder.
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========= ===========================================================
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Only the DEBUG option is supported by the special tunnel management
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PPPoX socket.
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@ -177,20 +185,22 @@ setsockopt on the PPPoX socket to set a debug mask.
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The following debug mask bits are available:
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================ ==============================
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L2TP_MSG_DEBUG verbose debug (if compiled in)
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L2TP_MSG_CONTROL userspace - kernel interface
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L2TP_MSG_SEQ sequence numbers handling
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L2TP_MSG_DATA data packets
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================ ==============================
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If enabled, files under a l2tp debugfs directory can be used to dump
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kernel state about L2TP tunnels and sessions. To access it, the
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debugfs filesystem must first be mounted.
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debugfs filesystem must first be mounted::
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# mount -t debugfs debugfs /debug
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# mount -t debugfs debugfs /debug
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Files under the l2tp directory can then be accessed.
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Files under the l2tp directory can then be accessed::
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# cat /debug/l2tp/tunnels
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# cat /debug/l2tp/tunnels
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The debugfs files should not be used by applications to obtain L2TP
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state information because the file format is subject to change. It is
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@ -211,14 +221,14 @@ iproute2's ip utility to support this.
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To create an L2TPv3 ethernet pseudowire between local host 192.168.1.1
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and peer 192.168.1.2, using IP addresses 10.5.1.1 and 10.5.1.2 for the
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tunnel endpoints:-
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tunnel endpoints::
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# ip l2tp add tunnel tunnel_id 1 peer_tunnel_id 1 udp_sport 5000 \
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udp_dport 5000 encap udp local 192.168.1.1 remote 192.168.1.2
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# ip l2tp add session tunnel_id 1 session_id 1 peer_session_id 1
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# ip -s -d show dev l2tpeth0
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# ip addr add 10.5.1.2/32 peer 10.5.1.1/32 dev l2tpeth0
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# ip li set dev l2tpeth0 up
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# ip l2tp add tunnel tunnel_id 1 peer_tunnel_id 1 udp_sport 5000 \
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udp_dport 5000 encap udp local 192.168.1.1 remote 192.168.1.2
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# ip l2tp add session tunnel_id 1 session_id 1 peer_session_id 1
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# ip -s -d show dev l2tpeth0
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# ip addr add 10.5.1.2/32 peer 10.5.1.1/32 dev l2tpeth0
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# ip li set dev l2tpeth0 up
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Choose IP addresses to be the address of a local IP interface and that
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of the remote system. The IP addresses of the l2tpeth0 interface can be
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@ -228,75 +238,78 @@ Repeat the above at the peer, with ports, tunnel/session ids and IP
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addresses reversed. The tunnel and session IDs can be any non-zero
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32-bit number, but the values must be reversed at the peer.
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======================== ===================
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Host 1 Host2
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======================== ===================
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udp_sport=5000 udp_sport=5001
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udp_dport=5001 udp_dport=5000
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tunnel_id=42 tunnel_id=45
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peer_tunnel_id=45 peer_tunnel_id=42
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session_id=128 session_id=5196755
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peer_session_id=5196755 peer_session_id=128
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======================== ===================
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When done at both ends of the tunnel, it should be possible to send
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data over the network. e.g.
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data over the network. e.g.::
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# ping 10.5.1.1
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# ping 10.5.1.1
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Sample Userspace Code
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=====================
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1. Create tunnel management PPPoX socket
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1. Create tunnel management PPPoX socket::
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kernel_fd = socket(AF_PPPOX, SOCK_DGRAM, PX_PROTO_OL2TP);
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if (kernel_fd >= 0) {
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struct sockaddr_pppol2tp sax;
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struct sockaddr_in const *peer_addr;
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kernel_fd = socket(AF_PPPOX, SOCK_DGRAM, PX_PROTO_OL2TP);
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if (kernel_fd >= 0) {
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struct sockaddr_pppol2tp sax;
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struct sockaddr_in const *peer_addr;
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peer_addr = l2tp_tunnel_get_peer_addr(tunnel);
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memset(&sax, 0, sizeof(sax));
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sax.sa_family = AF_PPPOX;
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sax.sa_protocol = PX_PROTO_OL2TP;
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sax.pppol2tp.fd = udp_fd; /* fd of tunnel UDP socket */
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sax.pppol2tp.addr.sin_addr.s_addr = peer_addr->sin_addr.s_addr;
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sax.pppol2tp.addr.sin_port = peer_addr->sin_port;
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sax.pppol2tp.addr.sin_family = AF_INET;
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sax.pppol2tp.s_tunnel = tunnel_id;
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sax.pppol2tp.s_session = 0; /* special case: mgmt socket */
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sax.pppol2tp.d_tunnel = 0;
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sax.pppol2tp.d_session = 0; /* special case: mgmt socket */
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peer_addr = l2tp_tunnel_get_peer_addr(tunnel);
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memset(&sax, 0, sizeof(sax));
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sax.sa_family = AF_PPPOX;
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sax.sa_protocol = PX_PROTO_OL2TP;
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sax.pppol2tp.fd = udp_fd; /* fd of tunnel UDP socket */
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sax.pppol2tp.addr.sin_addr.s_addr = peer_addr->sin_addr.s_addr;
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sax.pppol2tp.addr.sin_port = peer_addr->sin_port;
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sax.pppol2tp.addr.sin_family = AF_INET;
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sax.pppol2tp.s_tunnel = tunnel_id;
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sax.pppol2tp.s_session = 0; /* special case: mgmt socket */
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sax.pppol2tp.d_tunnel = 0;
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sax.pppol2tp.d_session = 0; /* special case: mgmt socket */
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if(connect(kernel_fd, (struct sockaddr *)&sax, sizeof(sax) ) < 0 ) {
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perror("connect failed");
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result = -errno;
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goto err;
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}
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}
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if(connect(kernel_fd, (struct sockaddr *)&sax, sizeof(sax) ) < 0 ) {
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perror("connect failed");
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result = -errno;
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goto err;
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}
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}
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2. Create session PPPoX data socket
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2. Create session PPPoX data socket::
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struct sockaddr_pppol2tp sax;
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int fd;
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struct sockaddr_pppol2tp sax;
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int fd;
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/* Note, the target socket must be bound already, else it will not be ready */
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sax.sa_family = AF_PPPOX;
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sax.sa_protocol = PX_PROTO_OL2TP;
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sax.pppol2tp.fd = tunnel_fd;
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sax.pppol2tp.addr.sin_addr.s_addr = addr->sin_addr.s_addr;
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sax.pppol2tp.addr.sin_port = addr->sin_port;
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sax.pppol2tp.addr.sin_family = AF_INET;
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sax.pppol2tp.s_tunnel = tunnel_id;
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sax.pppol2tp.s_session = session_id;
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sax.pppol2tp.d_tunnel = peer_tunnel_id;
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sax.pppol2tp.d_session = peer_session_id;
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/* Note, the target socket must be bound already, else it will not be ready */
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sax.sa_family = AF_PPPOX;
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sax.sa_protocol = PX_PROTO_OL2TP;
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sax.pppol2tp.fd = tunnel_fd;
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sax.pppol2tp.addr.sin_addr.s_addr = addr->sin_addr.s_addr;
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sax.pppol2tp.addr.sin_port = addr->sin_port;
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sax.pppol2tp.addr.sin_family = AF_INET;
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sax.pppol2tp.s_tunnel = tunnel_id;
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sax.pppol2tp.s_session = session_id;
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sax.pppol2tp.d_tunnel = peer_tunnel_id;
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sax.pppol2tp.d_session = peer_session_id;
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/* session_fd is the fd of the session's PPPoL2TP socket.
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* tunnel_fd is the fd of the tunnel UDP socket.
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*/
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fd = connect(session_fd, (struct sockaddr *)&sax, sizeof(sax));
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if (fd < 0 ) {
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return -errno;
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}
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return 0;
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/* session_fd is the fd of the session's PPPoL2TP socket.
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* tunnel_fd is the fd of the tunnel UDP socket.
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*/
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fd = connect(session_fd, (struct sockaddr *)&sax, sizeof(sax));
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if (fd < 0 ) {
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return -errno;
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}
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return 0;
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Internal Implementation
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=======================
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