[RFC PATCH 2/2] l2tp: Introduce L2TPv3 IP encapsulation support for IPv6

[RFC PATCH 2/2] l2tp: Introduce L2TPv3 IP encapsulation support for IPv6

[James Chapman]

L2TPv3 defines an IP encapsulation packet format where data is carried
directly over IP (no UDP). The kernel already has support for L2TP IP
encapsulation over IPv4 (l2tp_ip). This patch introduces support for L2TP
IP encapsulation over IPv6.

---
 include/linux/l2tp.h |   17 +
 net/l2tp/Makefile    |    1 +
 net/l2tp/l2tp_ip6.c  |  808 ++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 826 insertions(+), 0 deletions(-)
 create mode 100644 net/l2tp/l2tp_ip6.c

diff --git a/include/linux/l2tp.h b/include/linux/l2tp.h
index 16b8347..7eab668 100644
--- a/include/linux/l2tp.h
+++ b/include/linux/l2tp.h
@@ -11,6 +11,7 @@
 #include <linux/socket.h>
 #ifdef __KERNEL__
 #include <linux/in.h>
+#include <linux/in6.h>
 #else
 #include <netinet/in.h>
 #endif
@@ -39,6 +40,22 @@ struct sockaddr_l2tpip {
 			      sizeof(__u32)];
 };
 
+/**
+ * struct sockaddr_l2tpip6 - the sockaddr structure for L2TP-over-IPv6 sockets
+ * @l2tp_family:  address family number AF_L2TPIP.
+ * @l2tp_addr:    protocol specific address information
+ * @l2tp_conn_id: connection id of tunnel
+ */
+struct sockaddr_l2tpip6 {
+	/* The first fields must match struct sockaddr_in6 */
+	__kernel_sa_family_t l2tp_family; /* AF_INET6 */
+	__be16		l2tp_unused;	/* INET port number (unused) */
+	__be32		l2tp_flowinfo;	/* IPv6 flow information */
+	struct in6_addr	l2tp_addr;	/* IPv6 address */
+	__u32		l2tp_scope_id;	/* scope id (new in RFC2553) */
+	__u32		l2tp_conn_id;	/* Connection ID of tunnel */
+};
+
 /*****************************************************************************
  *  NETLINK_GENERIC netlink family.
  *****************************************************************************/
diff --git a/net/l2tp/Makefile b/net/l2tp/Makefile
index 110e7bc..a6378eb 100644
--- a/net/l2tp/Makefile
+++ b/net/l2tp/Makefile
@@ -10,3 +10,4 @@ obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_L2TP_IP)) += l2tp_ip.o
 obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_L2TP_V3)) += l2tp_netlink.o
 obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_L2TP_ETH)) += l2tp_eth.o
 obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_L2TP_DEBUGFS)) += l2tp_debugfs.o
+obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_L2TP_IP)) += l2tp_ip6.o
diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
new file mode 100644
index 0000000..4711014
--- /dev/null
+++ b/net/l2tp/l2tp_ip6.c
@@ -0,0 +1,808 @@
+/*
+ * L2TPv3 IP encapsulation support for IPv6
+ *
+ * Copyright (c) 2012 Katalix Systems Ltd
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/icmp.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/random.h>
+#include <linux/socket.h>
+#include <linux/l2tp.h>
+#include <linux/in.h>
+#include <linux/in6.h>
+#include <net/sock.h>
+#include <net/ip.h>
+#include <net/icmp.h>
+#include <net/udp.h>
+#include <net/inet_common.h>
+#include <net/inet_hashtables.h>
+#include <net/tcp_states.h>
+#include <net/protocol.h>
+#include <net/xfrm.h>
+
+#include <net/transp_v6.h>
+#include <net/addrconf.h>
+#include <net/ip6_route.h>
+
+#include "l2tp_core.h"
+
+struct l2tp_ip6_sock {
+	/* inet_sock has to be the first member of l2tp_ip6_sock */
+	struct inet_sock	inet;
+
+	__u32			conn_id;
+	__u32			peer_conn_id;
+
+	__u64			tx_packets;
+	__u64			tx_bytes;
+	__u64			tx_errors;
+	__u64			rx_packets;
+	__u64			rx_bytes;
+	__u64			rx_errors;
+
+	/* ipv6_pinfo has to be the last member of l2tp_ip6_sock, see
+	   inet6_sk_generic */
+	struct ipv6_pinfo	inet6;
+};
+
+static DEFINE_RWLOCK(l2tp_ip6_lock);
+static struct hlist_head l2tp_ip6_table;
+static struct hlist_head l2tp_ip6_bind_table;
+
+static inline struct l2tp_ip6_sock *l2tp_ip6_sk(const struct sock *sk)
+{
+	return (struct l2tp_ip6_sock *)sk;
+}
+
+static struct sock *__l2tp_ip6_bind_lookup(struct net *net, struct in6_addr *laddr,
+					   int dif, u32 tunnel_id)
+{
+	struct hlist_node *node;
+	struct sock *sk;
+
+	sk_for_each_bound(sk, node, &l2tp_ip6_bind_table) {
+		struct in6_addr *addr = inet6_rcv_saddr(sk);
+		struct l2tp_ip6_sock *l2tp = l2tp_ip6_sk(sk);
+
+		if (l2tp == NULL)
+			continue;
+
+		if ((l2tp->conn_id == tunnel_id) &&
+		    net_eq(sock_net(sk), net) &&
+		    !(addr && ipv6_addr_equal(addr, laddr)) &&
+		    !(sk->sk_bound_dev_if && sk->sk_bound_dev_if != dif))
+			goto found;
+	}
+
+	sk = NULL;
+found:
+	return sk;
+}
+
+static inline struct sock *l2tp_ip6_bind_lookup(struct net *net, struct in6_addr *laddr,
+						int dif, u32 tunnel_id)
+{
+	struct sock *sk = __l2tp_ip6_bind_lookup(net, laddr, dif, tunnel_id);
+	if (sk)
+		sock_hold(sk);
+
+	return sk;
+}
+
+/* When processing receive frames, there are two cases to
+ * consider. Data frames consist of a non-zero session-id and an
+ * optional cookie. Control frames consist of a regular L2TP header
+ * preceded by 32-bits of zeros.
+ *
+ * L2TPv3 Session Header Over IP
+ *
+ *  0                   1                   2                   3
+ *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                           Session ID                          |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |               Cookie (optional, maximum 64 bits)...
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *                                                                 |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * L2TPv3 Control Message Header Over IP
+ *
+ *  0                   1                   2                   3
+ *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                      (32 bits of zeros)                       |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |T|L|x|x|S|x|x|x|x|x|x|x|  Ver  |             Length            |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                     Control Connection ID                     |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |               Ns              |               Nr              |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * All control frames are passed to userspace.
+ */
+static int l2tp_ip6_recv(struct sk_buff *skb)
+{
+	struct sock *sk;
+	u32 session_id;
+	u32 tunnel_id;
+	unsigned char *ptr, *optr;
+	struct l2tp_session *session;
+	struct l2tp_tunnel *tunnel = NULL;
+	int length;
+	int offset;
+
+	/* Point to L2TP header */
+	optr = ptr = skb->data;
+
+	if (!pskb_may_pull(skb, 4))
+		goto discard;
+
+	session_id = ntohl(*((__be32 *) ptr));
+	ptr += 4;
+
+	/* RFC3931: L2TP/IP packets have the first 4 bytes containing
+	 * the session_id. If it is 0, the packet is a L2TP control
+	 * frame and the session_id value can be discarded.
+	 */
+	if (session_id == 0) {
+		__skb_pull(skb, 4);
+		goto pass_up;
+	}
+
+	/* Ok, this is a data packet. Lookup the session. */
+	session = l2tp_session_find(&init_net, NULL, session_id);
+	if (session == NULL)
+		goto discard;
+
+	tunnel = session->tunnel;
+	if (tunnel == NULL)
+		goto discard;
+
+	/* Trace packet contents, if enabled */
+	if (tunnel->debug & L2TP_MSG_DATA) {
+		length = min(32u, skb->len);
+		if (!pskb_may_pull(skb, length))
+			goto discard;
+
+		printk(KERN_DEBUG "%s: ip recv: ", tunnel->name);
+
+		offset = 0;
+		do {
+			printk(" %02X", ptr[offset]);
+		} while (++offset < length);
+
+		printk("\n");
+	}
+
+	l2tp_recv_common(session, skb, ptr, optr, 0, skb->len,
+			 tunnel->recv_payload_hook);
+	return 0;
+
+pass_up:
+	/* Get the tunnel_id from the L2TP header */
+	if (!pskb_may_pull(skb, 12))
+		goto discard;
+
+	if ((skb->data[0] & 0xc0) != 0xc0)
+		goto discard;
+
+	tunnel_id = ntohl(*(__be32 *) &skb->data[4]);
+	tunnel = l2tp_tunnel_find(&init_net, tunnel_id);
+	if (tunnel != NULL)
+		sk = tunnel->sock;
+	else {
+		struct ipv6hdr *iph = ipv6_hdr(skb);
+
+		read_lock_bh(&l2tp_ip6_lock);
+		sk = __l2tp_ip6_bind_lookup(&init_net, &iph->daddr,
+					    0, tunnel_id);
+		read_unlock_bh(&l2tp_ip6_lock);
+	}
+
+	if (sk == NULL)
+		goto discard;
+
+	sock_hold(sk);
+
+	if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
+		goto discard_put;
+
+	nf_reset(skb);
+
+	return sk_receive_skb(sk, skb, 1);
+
+discard_put:
+	sock_put(sk);
+
+discard:
+	kfree_skb(skb);
+	return 0;
+}
+
+static int l2tp_ip6_open(struct sock *sk)
+{
+	/* Prevent autobind. We don't have ports. */
+	inet_sk(sk)->inet_num = IPPROTO_L2TP;
+
+	write_lock_bh(&l2tp_ip6_lock);
+	sk_add_node(sk, &l2tp_ip6_table);
+	write_unlock_bh(&l2tp_ip6_lock);
+
+	return 0;
+}
+
+static void l2tp_ip6_close(struct sock *sk, long timeout)
+{
+	write_lock_bh(&l2tp_ip6_lock);
+	hlist_del_init(&sk->sk_bind_node);
+	sk_del_node_init(sk);
+	write_unlock_bh(&l2tp_ip6_lock);
+
+	sk_common_release(sk);
+}
+
+static void l2tp_ip6_destroy_sock(struct sock *sk)
+{
+	lock_sock(sk);
+	ip6_flush_pending_frames(sk);
+	release_sock(sk);
+
+	inet6_destroy_sock(sk);
+}
+
+static int l2tp_ip6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	struct ipv6_pinfo *np = inet6_sk(sk);
+	struct sockaddr_l2tpip6 *addr = (struct sockaddr_l2tpip6 *) uaddr;
+	__be32 v4addr = 0;
+	int addr_type;
+	int err;
+
+	if (addr_len < sizeof(*addr))
+		return -EINVAL;
+
+	addr_type = ipv6_addr_type(&addr->l2tp_addr);
+
+	/* l2tp_ip6 sockets are IPv6 only */
+	if (addr_type == IPV6_ADDR_MAPPED)
+		return -EADDRNOTAVAIL;
+
+	/* L2TP is point-point, not multicast */
+	if (addr_type & IPV6_ADDR_MULTICAST)
+		return -EADDRNOTAVAIL;
+
+	err = -EADDRINUSE;
+	read_lock_bh(&l2tp_ip6_lock);
+	if (__l2tp_ip6_bind_lookup(&init_net, &addr->l2tp_addr,
+				   sk->sk_bound_dev_if, addr->l2tp_conn_id))
+		goto out_in_use;
+	read_unlock_bh(&l2tp_ip6_lock);
+
+	lock_sock(sk);
+
+	err = -EINVAL;
+	if (sk->sk_state != TCP_CLOSE)
+		goto out_unlock;
+
+	/* Check if the address belongs to the host. */
+	if (addr_type != IPV6_ADDR_ANY) {
+		struct net_device *dev = NULL;
+
+		if (addr_type & IPV6_ADDR_LINKLOCAL) {
+			if (addr_len >= sizeof(struct sockaddr_in6) &&
+			    addr->l2tp_scope_id) {
+				/* Override any existing binding, if another
+				 * one is supplied by user.
+				 */
+				sk->sk_bound_dev_if = addr->l2tp_scope_id;
+			}
+
+			/* Binding to link-local address requires an
+			   interface */
+			if (!sk->sk_bound_dev_if)
+				goto out_unlock;
+
+			err = -ENODEV;
+			rcu_read_lock();
+			dev = dev_get_by_index_rcu(sock_net(sk),
+						   sk->sk_bound_dev_if);
+			rcu_read_unlock();
+			if (!dev)
+				goto out_unlock;
+		}
+
+		/* ipv4 addr of the socket is invalid.  Only the
+		 * unspecified and mapped address have a v4 equivalent.
+		 */
+		v4addr = LOOPBACK4_IPV6;
+		err = -EADDRNOTAVAIL;
+		if (!ipv6_chk_addr(sock_net(sk), &addr->l2tp_addr, dev, 0))
+			goto out_unlock;
+	}
+
+	inet->inet_rcv_saddr = inet->inet_saddr = v4addr;
+	np->rcv_saddr = addr->l2tp_addr;
+	np->saddr = addr->l2tp_addr;
+
+	l2tp_ip6_sk(sk)->conn_id = addr->l2tp_conn_id;
+
+	write_lock_bh(&l2tp_ip6_lock);
+	sk_add_bind_node(sk, &l2tp_ip6_bind_table);
+	sk_del_node_init(sk);
+	write_unlock_bh(&l2tp_ip6_lock);
+
+	err = 0;
+out_unlock:
+	release_sock(sk);
+	return err;
+
+out_in_use:
+	read_unlock_bh(&l2tp_ip6_lock);
+	return err;
+}
+
+static int l2tp_ip6_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
+{
+	struct sockaddr_l2tpip6 *lsa = (struct sockaddr_l2tpip6 *) uaddr;
+	struct sockaddr_in6	*usin = (struct sockaddr_in6 *) uaddr;
+	struct in6_addr	*daddr;
+	int	addr_type;
+	int rc;
+
+	if (addr_len < sizeof(*lsa))
+		return -EINVAL;
+
+	addr_type = ipv6_addr_type(&usin->sin6_addr);
+	if (addr_type & IPV6_ADDR_MULTICAST)
+		return -EINVAL;
+
+	if (addr_type & IPV6_ADDR_MAPPED) {
+		daddr = &usin->sin6_addr;
+		if (ipv4_is_multicast(daddr->s6_addr32[3]))
+			return -EINVAL;
+	}
+
+	rc = ip6_datagram_connect(sk, uaddr, addr_len);
+
+	lock_sock(sk);
+
+	l2tp_ip6_sk(sk)->peer_conn_id = lsa->l2tp_conn_id;
+
+	write_lock_bh(&l2tp_ip6_lock);
+	hlist_del_init(&sk->sk_bind_node);
+	sk_add_bind_node(sk, &l2tp_ip6_bind_table);
+	write_unlock_bh(&l2tp_ip6_lock);
+
+	release_sock(sk);
+
+	return rc;
+}
+
+static int l2tp_ip6_getname(struct socket *sock, struct sockaddr *uaddr,
+			    int *uaddr_len, int peer)
+{
+	struct sockaddr_l2tpip6 *lsa = (struct sockaddr_l2tpip6 *)uaddr;
+	struct sock *sk = sock->sk;
+	struct ipv6_pinfo *np = inet6_sk(sk);
+	struct l2tp_ip6_sock *lsk = l2tp_ip6_sk(sk);
+
+	lsa->l2tp_family = AF_INET6;
+	lsa->l2tp_flowinfo = 0;
+	lsa->l2tp_scope_id = 0;
+	if (peer) {
+		if (!lsk->peer_conn_id)
+			return -ENOTCONN;
+		lsa->l2tp_conn_id = lsk->peer_conn_id;
+		lsa->l2tp_addr = np->daddr;
+		if (np->sndflow)
+			lsa->l2tp_flowinfo = np->flow_label;
+	} else {
+		if (ipv6_addr_any(&np->rcv_saddr))
+			lsa->l2tp_addr = np->saddr;
+		else
+			lsa->l2tp_addr = np->rcv_saddr;
+
+		lsa->l2tp_conn_id = lsk->conn_id;
+	}
+	if (ipv6_addr_type(&lsa->l2tp_addr) & IPV6_ADDR_LINKLOCAL)
+		lsa->l2tp_scope_id = sk->sk_bound_dev_if;
+	*uaddr_len = sizeof(*lsa);
+	return 0;
+}
+
+static int l2tp_ip6_backlog_recv(struct sock *sk, struct sk_buff *skb)
+{
+	int rc;
+
+	/* Charge it to the socket, dropping if the queue is full. */
+	rc = sock_queue_rcv_skb(sk, skb);
+	if (rc < 0)
+		goto drop;
+
+	return 0;
+
+drop:
+	IP_INC_STATS(&init_net, IPSTATS_MIB_INDISCARDS);
+	kfree_skb(skb);
+	return -1;
+}
+
+static int l2tp_ip6_push_pending_frames(struct sock *sk)
+{
+	struct sk_buff *skb;
+	__be32 *transhdr = NULL;
+	int err = 0;
+
+	skb = skb_peek(&sk->sk_write_queue);
+	if (skb == NULL)
+		goto out;
+
+	transhdr = (__be32 *)skb_transport_header(skb);
+	*transhdr = 0;
+
+	err = ip6_push_pending_frames(sk);
+
+out:
+	return err;
+}
+
+/* Userspace will call sendmsg() on the tunnel socket to send L2TP
+ * control frames.
+ */
+static int l2tp_ip6_sendmsg(struct kiocb *iocb, struct sock *sk,
+			    struct msghdr *msg, size_t len)
+{
+	struct ipv6_txoptions opt_space;
+	struct sockaddr_l2tpip6 *lsa = (struct sockaddr_l2tpip6 *) msg->msg_name;
+	struct in6_addr *daddr, *final_p, final;
+	struct ipv6_pinfo *np = inet6_sk(sk);
+	struct l2tp_ip6_sock *lsk = l2tp_ip6_sk(sk);
+	struct ipv6_txoptions *opt = NULL;
+	struct ip6_flowlabel *flowlabel = NULL;
+	struct dst_entry *dst = NULL;
+	struct flowi6 fl6;
+	int addr_len = msg->msg_namelen;
+	int hlimit = -1;
+	int tclass = -1;
+	int dontfrag = -1;
+	int transhdrlen = 4; /* zero session-id */
+	int ulen = len + transhdrlen;
+	int err;
+
+	/* Rough check on arithmetic overflow,
+	   better check is made in ip6_append_data().
+	 */
+	if (len > INT_MAX)
+		return -EMSGSIZE;
+
+	/* Mirror BSD error message compatibility */
+	if (msg->msg_flags & MSG_OOB)
+		return -EOPNOTSUPP;
+
+	/*
+	 *	Get and verify the address.
+	 */
+	memset(&fl6, 0, sizeof(fl6));
+
+	fl6.flowi6_mark = sk->sk_mark;
+
+	if (lsa) {
+		if (addr_len < SIN6_LEN_RFC2133)
+			return -EINVAL;
+
+		if (lsa->l2tp_family && lsa->l2tp_family != AF_INET6)
+			return -EAFNOSUPPORT;
+
+		daddr = &lsa->l2tp_addr;
+		if (np->sndflow) {
+			fl6.flowlabel = lsa->l2tp_flowinfo & IPV6_FLOWINFO_MASK;
+			if (fl6.flowlabel&IPV6_FLOWLABEL_MASK) {
+				flowlabel = fl6_sock_lookup(sk, fl6.flowlabel);
+				if (flowlabel == NULL)
+					return -EINVAL;
+				daddr = &flowlabel->dst;
+			}
+		}
+
+		/*
+		 * Otherwise it will be difficult to maintain
+		 * sk->sk_dst_cache.
+		 */
+		if (sk->sk_state == TCP_ESTABLISHED &&
+		    ipv6_addr_equal(daddr, &np->daddr))
+			daddr = &np->daddr;
+
+		if (addr_len >= sizeof(struct sockaddr_in6) &&
+		    lsa->l2tp_scope_id &&
+		    ipv6_addr_type(daddr) & IPV6_ADDR_LINKLOCAL)
+			fl6.flowi6_oif = lsa->l2tp_scope_id;
+	} else {
+		if (sk->sk_state != TCP_ESTABLISHED)
+			return -EDESTADDRREQ;
+
+		daddr = &np->daddr;
+		fl6.flowlabel = np->flow_label;
+	}
+
+	if (fl6.flowi6_oif == 0)
+		fl6.flowi6_oif = sk->sk_bound_dev_if;
+
+	if (msg->msg_controllen) {
+		opt = &opt_space;
+		memset(opt, 0, sizeof(struct ipv6_txoptions));
+		opt->tot_len = sizeof(struct ipv6_txoptions);
+
+		err = datagram_send_ctl(sock_net(sk), sk, msg, &fl6, opt,
+					&hlimit, &tclass, &dontfrag);
+		if (err < 0) {
+			fl6_sock_release(flowlabel);
+			return err;
+		}
+		if ((fl6.flowlabel & IPV6_FLOWLABEL_MASK) && !flowlabel) {
+			flowlabel = fl6_sock_lookup(sk, fl6.flowlabel);
+			if (flowlabel == NULL)
+				return -EINVAL;
+		}
+		if (!(opt->opt_nflen|opt->opt_flen))
+			opt = NULL;
+	}
+
+	if (opt == NULL)
+		opt = np->opt;
+	if (flowlabel)
+		opt = fl6_merge_options(&opt_space, flowlabel, opt);
+	opt = ipv6_fixup_options(&opt_space, opt);
+
+	fl6.flowi6_proto = sk->sk_protocol;
+	if (!ipv6_addr_any(daddr))
+		fl6.daddr = *daddr;
+	else
+		fl6.daddr.s6_addr[15] = 0x1; /* :: means loopback (BSD'ism) */
+	if (ipv6_addr_any(&fl6.saddr) && !ipv6_addr_any(&np->saddr))
+		fl6.saddr = np->saddr;
+
+	final_p = fl6_update_dst(&fl6, opt, &final);
+
+	if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr))
+		fl6.flowi6_oif = np->mcast_oif;
+	else if (!fl6.flowi6_oif)
+		fl6.flowi6_oif = np->ucast_oif;
+
+	security_sk_classify_flow(sk, flowi6_to_flowi(&fl6));
+
+	dst = ip6_dst_lookup_flow(sk, &fl6, final_p, true);
+	if (IS_ERR(dst)) {
+		err = PTR_ERR(dst);
+		goto out;
+	}
+
+	if (hlimit < 0) {
+		if (ipv6_addr_is_multicast(&fl6.daddr))
+			hlimit = np->mcast_hops;
+		else
+			hlimit = np->hop_limit;
+		if (hlimit < 0)
+			hlimit = ip6_dst_hoplimit(dst);
+	}
+
+	if (tclass < 0)
+		tclass = np->tclass;
+
+	if (dontfrag < 0)
+		dontfrag = np->dontfrag;
+
+	if (msg->msg_flags & MSG_CONFIRM)
+		goto do_confirm;
+
+back_from_confirm:
+	lock_sock(sk);
+	err = ip6_append_data(sk, ip_generic_getfrag, msg->msg_iov,
+			      ulen, transhdrlen, hlimit, tclass, opt,
+			      &fl6, (struct rt6_info *)dst,
+			      msg->msg_flags, dontfrag);
+	if (err)
+		ip6_flush_pending_frames(sk);
+	else if (!(msg->msg_flags & MSG_MORE))
+		err = l2tp_ip6_push_pending_frames(sk);
+	release_sock(sk);
+done:
+	dst_release(dst);
+out:
+	fl6_sock_release(flowlabel);
+
+	/* Update stats */
+	if (err < 0) {
+		lsk->tx_errors++;
+	} else {
+		lsk->tx_packets++;
+		lsk->tx_bytes += len;
+	}
+
+	return err < 0 ? err : len;
+
+do_confirm:
+	dst_confirm(dst);
+	if (!(msg->msg_flags & MSG_PROBE) || len)
+		goto back_from_confirm;
+	err = 0;
+	goto done;
+}
+
+static int l2tp_ip6_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
+			    size_t len, int noblock, int flags, int *addr_len)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	struct l2tp_ip6_sock *lsk = l2tp_ip6_sk(sk);
+	struct sockaddr_l2tpip6 *lsa = (struct sockaddr_l2tpip6 *)msg->msg_name;
+	size_t copied = 0;
+	int err = -EOPNOTSUPP;
+	struct sk_buff *skb;
+
+	if (flags & MSG_OOB)
+		goto out;
+
+	if (addr_len)
+		*addr_len = sizeof(*lsa);
+
+	if (flags & MSG_ERRQUEUE)
+		return ipv6_recv_error(sk, msg, len);
+
+	skb = skb_recv_datagram(sk, flags, noblock, &err);
+	if (!skb)
+		goto out;
+
+	copied = skb->len;
+	if (len < copied) {
+		msg->msg_flags |= MSG_TRUNC;
+		copied = len;
+	}
+
+	err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);
+	if (err)
+		goto done;
+
+	sock_recv_timestamp(msg, sk, skb);
+
+	/* Copy the address. */
+	if (lsa) {
+		lsa->l2tp_family = AF_INET6;
+		lsa->l2tp_unused = 0;
+		lsa->l2tp_addr = ipv6_hdr(skb)->saddr;
+		lsa->l2tp_flowinfo = 0;
+		lsa->l2tp_scope_id = 0;
+		if (ipv6_addr_type(&lsa->l2tp_addr) & IPV6_ADDR_LINKLOCAL)
+			lsa->l2tp_scope_id = IP6CB(skb)->iif;
+	}
+
+	if (inet->cmsg_flags)
+		ip_cmsg_recv(msg, skb);
+
+	if (flags & MSG_TRUNC)
+		copied = skb->len;
+done:
+	skb_free_datagram(sk, skb);
+out:
+	if (err) {
+		lsk->rx_errors++;
+		return err;
+	}
+
+	lsk->rx_packets++;
+	lsk->rx_bytes += copied;
+
+	return copied;
+}
+
+static struct proto l2tp_ip6_prot = {
+	.name		   = "L2TP/IPv6",
+	.owner		   = THIS_MODULE,
+	.init		   = l2tp_ip6_open,
+	.close		   = l2tp_ip6_close,
+	.bind		   = l2tp_ip6_bind,
+	.connect	   = l2tp_ip6_connect,
+	.disconnect	   = udp_disconnect,
+	.ioctl		   = udp_ioctl,
+	.destroy	   = l2tp_ip6_destroy_sock,
+	.setsockopt	   = ipv6_setsockopt,
+	.getsockopt	   = ipv6_getsockopt,
+	.sendmsg	   = l2tp_ip6_sendmsg,
+	.recvmsg	   = l2tp_ip6_recvmsg,
+	.backlog_rcv	   = l2tp_ip6_backlog_recv,
+	.hash		   = inet_hash,
+	.unhash		   = inet_unhash,
+	.obj_size	   = sizeof(struct l2tp_ip6_sock),
+#ifdef CONFIG_COMPAT
+	.compat_setsockopt = compat_ipv6_setsockopt,
+	.compat_getsockopt = compat_ipv6_getsockopt,
+#endif
+};
+
+static const struct proto_ops l2tp_ip6_ops = {
+	.family		   = PF_INET6,
+	.owner		   = THIS_MODULE,
+	.release	   = inet6_release,
+	.bind		   = inet6_bind,
+	.connect	   = inet_dgram_connect,
+	.socketpair	   = sock_no_socketpair,
+	.accept		   = sock_no_accept,
+	.getname	   = l2tp_ip6_getname,
+	.poll		   = datagram_poll,
+	.ioctl		   = inet6_ioctl,
+	.listen		   = sock_no_listen,
+	.shutdown	   = inet_shutdown,
+	.setsockopt	   = sock_common_setsockopt,
+	.getsockopt	   = sock_common_getsockopt,
+	.sendmsg	   = inet_sendmsg,
+	.recvmsg	   = sock_common_recvmsg,
+	.mmap		   = sock_no_mmap,
+	.sendpage	   = sock_no_sendpage,
+#ifdef CONFIG_COMPAT
+	.compat_setsockopt = compat_sock_common_setsockopt,
+	.compat_getsockopt = compat_sock_common_getsockopt,
+#endif
+};
+
+static struct inet_protosw l2tp_ip6_protosw = {
+	.type		= SOCK_DGRAM,
+	.protocol	= IPPROTO_L2TP,
+	.prot		= &l2tp_ip6_prot,
+	.ops		= &l2tp_ip6_ops,
+	.no_check	= 0,
+};
+
+static struct inet6_protocol l2tp_ip6_protocol __read_mostly = {
+	.handler	= l2tp_ip6_recv,
+};
+
+static int __init l2tp_ip6_init(void)
+{
+	int err;
+
+	printk(KERN_INFO "L2TP IP encapsulation support for IPv6 (L2TPv3)\n");
+
+	err = proto_register(&l2tp_ip6_prot, 1);
+	if (err != 0)
+		goto out;
+
+	err = inet6_add_protocol(&l2tp_ip6_protocol, IPPROTO_L2TP);
+	if (err)
+		goto out1;
+
+	inet6_register_protosw(&l2tp_ip6_protosw);
+	return 0;
+
+out1:
+	proto_unregister(&l2tp_ip6_prot);
+out:
+	return err;
+}
+
+static void __exit l2tp_ip6_exit(void)
+{
+	inet6_unregister_protosw(&l2tp_ip6_protosw);
+	inet6_del_protocol(&l2tp_ip6_protocol, IPPROTO_L2TP);
+	proto_unregister(&l2tp_ip6_prot);
+}
+
+module_init(l2tp_ip6_init);
+module_exit(l2tp_ip6_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Chris Elston <celston@katalix.com>");
+MODULE_DESCRIPTION("L2TP IP encapsulation for IPv6");
+MODULE_VERSION("1.0");
+
+/* Use the value of SOCK_DGRAM (2) directory, because __stringify doesn't like
+ * enums
+ */
+MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET6, 2, IPPROTO_L2TP);
-- 
1.7.0.4

Re: [RFC PATCH 2/2] l2tp: Introduce L2TPv3 IP encapsulation support for IPv6

[Eric Dumazet]

On Tue, 2012-04-17 at 13:29 +0100, James Chapman wrote:
> L2TPv3 defines an IP encapsulation packet format where data is carried
> directly over IP (no UDP). The kernel already has support for L2TP IP
> encapsulation over IPv4 (l2tp_ip). This patch introduces support for L2TP
> IP encapsulation over IPv6.

...

> +	/* Check if the address belongs to the host. */
> +	if (addr_type != IPV6_ADDR_ANY) {
> +		struct net_device *dev = NULL;
> +
> +		if (addr_type & IPV6_ADDR_LINKLOCAL) {
> +			if (addr_len >= sizeof(struct sockaddr_in6) &&
> +			    addr->l2tp_scope_id) {
> +				/* Override any existing binding, if another
> +				 * one is supplied by user.
> +				 */
> +				sk->sk_bound_dev_if = addr->l2tp_scope_id;
> +			}
> +
> +			/* Binding to link-local address requires an
> +			   interface */
> +			if (!sk->sk_bound_dev_if)
> +				goto out_unlock;
> +
> +			err = -ENODEV;
> +			rcu_read_lock();
> +			dev = dev_get_by_index_rcu(sock_net(sk),
> +						   sk->sk_bound_dev_if);
> +			rcu_read_unlock();

			Here you can not dereference dev, since it can disappear after
rcu_read_unlock()

> +			if (!dev)
> +				goto out_unlock;
> +		}
> +
> +		/* ipv4 addr of the socket is invalid.  Only the
> +		 * unspecified and mapped address have a v4 equivalent.
> +		 */
> +		v4addr = LOOPBACK4_IPV6;
> +		err = -EADDRNOTAVAIL;

	So I suspect a potential problem here :

> +		if (!ipv6_chk_addr(sock_net(sk), &addr->l2tp_addr, dev, 0))
> +			goto out_unlock;
> +	}
> +

...

> +back_from_confirm:
> +	lock_sock(sk);
> +	err = ip6_append_data(sk, ip_generic_getfrag, msg->msg_iov,
> +			      ulen, transhdrlen, hlimit, tclass, opt,
> +			      &fl6, (struct rt6_info *)dst,
> +			      msg->msg_flags, dontfrag);
> +	if (err)
> +		ip6_flush_pending_frames(sk);
> +	else if (!(msg->msg_flags & MSG_MORE))
> +		err = l2tp_ip6_push_pending_frames(sk);
> +	release_sock(sk);
> +done:
> +	dst_release(dst);
> +out:
> +	fl6_sock_release(flowlabel);
> +
> +	/* Update stats */
> +	if (err < 0) {
> +		lsk->tx_errors++;
> +	} else {
> +		lsk->tx_packets++;

This is not SMP (especially on 32bit) safe, you dont own any lock

> +		lsk->tx_bytes += len;
> +	}
> +
> +	return err < 0 ? err : len;
> +
> +do_confirm:
> +	dst_confirm(dst);
> +	if (!(msg->msg_flags & MSG_PROBE) || len)
> +		goto back_from_confirm;
> +	err = 0;
> +	goto done;
> +}
> +

Re: [RFC PATCH 2/2] l2tp: Introduce L2TPv3 IP encapsulation support for IPv6

[James Chapman]

On 17/04/12 13:48, Eric Dumazet wrote:
> On Tue, 2012-04-17 at 13:29 +0100, James Chapman wrote:
>> L2TPv3 defines an IP encapsulation packet format where data is carried
>> directly over IP (no UDP). The kernel already has support for L2TP IP
>> encapsulation over IPv4 (l2tp_ip). This patch introduces support for L2TP
>> IP encapsulation over IPv6.
> 
> ...
>
>> +	/* Update stats */
>> +	if (err < 0) {
>> +		lsk->tx_errors++;
>> +	} else {
>> +		lsk->tx_packets++;
> 
> This is not SMP (especially on 32bit) safe, you dont own any lock

Thanks for catching this. This should be updating the stats in the l2tp
tunnel, not private data of the socket. We have the same SMP issues in
the l2tp tunnel/session stats code though. I'll submit a separate patch
to fix it.

Thanks for reviewing.


-- 
James Chapman
Katalix Systems Ltd
http://www.katalix.com
Catalysts for your Embedded Linux software development

Re: [RFC PATCH 2/2] l2tp: Introduce L2TPv3 IP encapsulation support for IPv6

[David Miller]

From: James Chapman <jchapman@katalix.com>
Date: Tue, 17 Apr 2012 13:29:26 +0100

> L2TPv3 defines an IP encapsulation packet format where data is carried
> directly over IP (no UDP). The kernel already has support for L2TP IP
> encapsulation over IPv4 (l2tp_ip). This patch introduces support for L2TP
> IP encapsulation over IPv6.

Either the ipv4 side should be changed to use ip4_datagram_connect()
or the ipv6 side should duplicate just the parts of
ip6_datagram_connect() it needs.

Which is it? :-)

Re: [RFC PATCH 2/2] l2tp: Introduce L2TPv3 IP encapsulation support for IPv6

[James Chapman]

On 18/04/12 05:28, David Miller wrote:
> From: James Chapman <jchapman@katalix.com>
> Date: Tue, 17 Apr 2012 13:29:26 +0100
> 
>> L2TPv3 defines an IP encapsulation packet format where data is carried
>> directly over IP (no UDP). The kernel already has support for L2TP IP
>> encapsulation over IPv4 (l2tp_ip). This patch introduces support for L2TP
>> IP encapsulation over IPv6.
> 
> Either the ipv4 side should be changed to use ip4_datagram_connect()
> or the ipv6 side should duplicate just the parts of
> ip6_datagram_connect() it needs.
> 
> Which is it? :-)

Ok, I'll add a patch to l2tp_ip to have it use ip4_datagram_connect(). :-)