diff options
Diffstat (limited to 'drivers/net/ppp/pppolac.c')
| -rw-r--r-- | drivers/net/ppp/pppolac.c | 449 |
1 files changed, 449 insertions, 0 deletions
diff --git a/drivers/net/ppp/pppolac.c b/drivers/net/ppp/pppolac.c new file mode 100644 index 00000000..a5d3d634 --- /dev/null +++ b/drivers/net/ppp/pppolac.c @@ -0,0 +1,449 @@ +/* drivers/net/pppolac.c + * + * Driver for PPP on L2TP Access Concentrator / PPPoLAC Socket (RFC 2661) + * + * Copyright (C) 2009 Google, Inc. + * + * This software is licensed under the terms of the GNU General Public + * License version 2, as published by the Free Software Foundation, and + * may be copied, distributed, and modified under those terms. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + */ + +/* This driver handles L2TP data packets between a UDP socket and a PPP channel. + * The socket must keep connected, and only one session per socket is permitted. + * Sequencing of outgoing packets is controlled by LNS. Incoming packets with + * sequences are reordered within a sliding window of one second. Currently + * reordering only happens when a packet is received. It is done for simplicity + * since no additional locks or threads are required. This driver only works on + * IPv4 due to the lack of UDP encapsulation support in IPv6. */ + +#include <linux/module.h> +#include <linux/jiffies.h> +#include <linux/workqueue.h> +#include <linux/skbuff.h> +#include <linux/file.h> +#include <linux/netdevice.h> +#include <linux/net.h> +#include <linux/udp.h> +#include <linux/ppp_defs.h> +#include <linux/if_ppp.h> +#include <linux/if_pppox.h> +#include <linux/ppp_channel.h> +#include <net/tcp_states.h> +#include <asm/uaccess.h> + +#define L2TP_CONTROL_BIT 0x80 +#define L2TP_LENGTH_BIT 0x40 +#define L2TP_SEQUENCE_BIT 0x08 +#define L2TP_OFFSET_BIT 0x02 +#define L2TP_VERSION 0x02 +#define L2TP_VERSION_MASK 0x0F + +#define PPP_ADDR 0xFF +#define PPP_CTRL 0x03 + +union unaligned { + __u32 u32; +} __attribute__((packed)); + +static inline union unaligned *unaligned(void *ptr) +{ + return (union unaligned *)ptr; +} + +struct meta { + __u32 sequence; + __u32 timestamp; +}; + +static inline struct meta *skb_meta(struct sk_buff *skb) +{ + return (struct meta *)skb->cb; +} + +/******************************************************************************/ + +static int pppolac_recv_core(struct sock *sk_udp, struct sk_buff *skb) +{ + struct sock *sk = (struct sock *)sk_udp->sk_user_data; + struct pppolac_opt *opt = &pppox_sk(sk)->proto.lac; + struct meta *meta = skb_meta(skb); + __u32 now = jiffies; + __u8 bits; + __u8 *ptr; + + /* Drop the packet if L2TP header is missing. */ + if (skb->len < sizeof(struct udphdr) + 6) + goto drop; + + /* Put it back if it is a control packet. */ + if (skb->data[sizeof(struct udphdr)] & L2TP_CONTROL_BIT) + return opt->backlog_rcv(sk_udp, skb); + + /* Skip UDP header. */ + skb_pull(skb, sizeof(struct udphdr)); + + /* Check the version. */ + if ((skb->data[1] & L2TP_VERSION_MASK) != L2TP_VERSION) + goto drop; + bits = skb->data[0]; + ptr = &skb->data[2]; + + /* Check the length if it is present. */ + if (bits & L2TP_LENGTH_BIT) { + if ((ptr[0] << 8 | ptr[1]) != skb->len) + goto drop; + ptr += 2; + } + + /* Skip all fields including optional ones. */ + if (!skb_pull(skb, 6 + (bits & L2TP_SEQUENCE_BIT ? 4 : 0) + + (bits & L2TP_LENGTH_BIT ? 2 : 0) + + (bits & L2TP_OFFSET_BIT ? 2 : 0))) + goto drop; + + /* Skip the offset padding if it is present. */ + if (bits & L2TP_OFFSET_BIT && + !skb_pull(skb, skb->data[-2] << 8 | skb->data[-1])) + goto drop; + + /* Check the tunnel and the session. */ + if (unaligned(ptr)->u32 != opt->local) + goto drop; + + /* Check the sequence if it is present. */ + if (bits & L2TP_SEQUENCE_BIT) { + meta->sequence = ptr[4] << 8 | ptr[5]; + if ((__s16)(meta->sequence - opt->recv_sequence) < 0) + goto drop; + } + + /* Skip PPP address and control if they are present. */ + if (skb->len >= 2 && skb->data[0] == PPP_ADDR && + skb->data[1] == PPP_CTRL) + skb_pull(skb, 2); + + /* Fix PPP protocol if it is compressed. */ + if (skb->len >= 1 && skb->data[0] & 1) + skb_push(skb, 1)[0] = 0; + + /* Drop the packet if PPP protocol is missing. */ + if (skb->len < 2) + goto drop; + + /* Perform reordering if sequencing is enabled. */ + atomic_set(&opt->sequencing, bits & L2TP_SEQUENCE_BIT); + if (bits & L2TP_SEQUENCE_BIT) { + struct sk_buff *skb1; + + /* Insert the packet into receive queue in order. */ + skb_set_owner_r(skb, sk); + skb_queue_walk(&sk->sk_receive_queue, skb1) { + struct meta *meta1 = skb_meta(skb1); + __s16 order = meta->sequence - meta1->sequence; + if (order == 0) + goto drop; + if (order < 0) { + meta->timestamp = meta1->timestamp; + skb_insert(skb1, skb, &sk->sk_receive_queue); + skb = NULL; + break; + } + } + if (skb) { + meta->timestamp = now; + skb_queue_tail(&sk->sk_receive_queue, skb); + } + + /* Remove packets from receive queue as long as + * 1. the receive buffer is full, + * 2. they are queued longer than one second, or + * 3. there are no missing packets before them. */ + skb_queue_walk_safe(&sk->sk_receive_queue, skb, skb1) { + meta = skb_meta(skb); + if (atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf && + now - meta->timestamp < HZ && + meta->sequence != opt->recv_sequence) + break; + skb_unlink(skb, &sk->sk_receive_queue); + opt->recv_sequence = (__u16)(meta->sequence + 1); + skb_orphan(skb); + ppp_input(&pppox_sk(sk)->chan, skb); + } + return NET_RX_SUCCESS; + } + + /* Flush receive queue if sequencing is disabled. */ + skb_queue_purge(&sk->sk_receive_queue); + skb_orphan(skb); + ppp_input(&pppox_sk(sk)->chan, skb); + return NET_RX_SUCCESS; +drop: + kfree_skb(skb); + return NET_RX_DROP; +} + +static int pppolac_recv(struct sock *sk_udp, struct sk_buff *skb) +{ + sock_hold(sk_udp); + sk_receive_skb(sk_udp, skb, 0); + return 0; +} + +static struct sk_buff_head delivery_queue; + +static void pppolac_xmit_core(struct work_struct *delivery_work) +{ + mm_segment_t old_fs = get_fs(); + struct sk_buff *skb; + + set_fs(KERNEL_DS); + while ((skb = skb_dequeue(&delivery_queue))) { + struct sock *sk_udp = skb->sk; + struct kvec iov = {.iov_base = skb->data, .iov_len = skb->len}; + struct msghdr msg = { + .msg_iov = (struct iovec *)&iov, + .msg_iovlen = 1, + .msg_flags = MSG_NOSIGNAL | MSG_DONTWAIT, + }; + sk_udp->sk_prot->sendmsg(NULL, sk_udp, &msg, skb->len); + kfree_skb(skb); + } + set_fs(old_fs); +} + +static DECLARE_WORK(delivery_work, pppolac_xmit_core); + +static int pppolac_xmit(struct ppp_channel *chan, struct sk_buff *skb) +{ + struct sock *sk_udp = (struct sock *)chan->private; + struct pppolac_opt *opt = &pppox_sk(sk_udp->sk_user_data)->proto.lac; + + /* Install PPP address and control. */ + skb_push(skb, 2); + skb->data[0] = PPP_ADDR; + skb->data[1] = PPP_CTRL; + + /* Install L2TP header. */ + if (atomic_read(&opt->sequencing)) { + skb_push(skb, 10); + skb->data[0] = L2TP_SEQUENCE_BIT; + skb->data[6] = opt->xmit_sequence >> 8; + skb->data[7] = opt->xmit_sequence; + skb->data[8] = 0; + skb->data[9] = 0; + opt->xmit_sequence++; + } else { + skb_push(skb, 6); + skb->data[0] = 0; + } + skb->data[1] = L2TP_VERSION; + unaligned(&skb->data[2])->u32 = opt->remote; + + /* Now send the packet via the delivery queue. */ + skb_set_owner_w(skb, sk_udp); + skb_queue_tail(&delivery_queue, skb); + schedule_work(&delivery_work); + return 1; +} + +/******************************************************************************/ + +static struct ppp_channel_ops pppolac_channel_ops = { + .start_xmit = pppolac_xmit, +}; + +static int pppolac_connect(struct socket *sock, struct sockaddr *useraddr, + int addrlen, int flags) +{ + struct sock *sk = sock->sk; + struct pppox_sock *po = pppox_sk(sk); + struct sockaddr_pppolac *addr = (struct sockaddr_pppolac *)useraddr; + struct socket *sock_udp = NULL; + struct sock *sk_udp; + int error; + + if (addrlen != sizeof(struct sockaddr_pppolac) || + !addr->local.tunnel || !addr->local.session || + !addr->remote.tunnel || !addr->remote.session) { + return -EINVAL; + } + + lock_sock(sk); + error = -EALREADY; + if (sk->sk_state != PPPOX_NONE) + goto out; + + sock_udp = sockfd_lookup(addr->udp_socket, &error); + if (!sock_udp) + goto out; + sk_udp = sock_udp->sk; + lock_sock(sk_udp); + + /* Remove this check when IPv6 supports UDP encapsulation. */ + error = -EAFNOSUPPORT; + if (sk_udp->sk_family != AF_INET) + goto out; + error = -EPROTONOSUPPORT; + if (sk_udp->sk_protocol != IPPROTO_UDP) + goto out; + error = -EDESTADDRREQ; + if (sk_udp->sk_state != TCP_ESTABLISHED) + goto out; + error = -EBUSY; + if (udp_sk(sk_udp)->encap_type || sk_udp->sk_user_data) + goto out; + if (!sk_udp->sk_bound_dev_if) { + struct dst_entry *dst = sk_dst_get(sk_udp); + error = -ENODEV; + if (!dst) + goto out; + sk_udp->sk_bound_dev_if = dst->dev->ifindex; + dst_release(dst); + } + + po->chan.hdrlen = 12; + po->chan.private = sk_udp; + po->chan.ops = &pppolac_channel_ops; + po->chan.mtu = PPP_MRU - 80; + po->proto.lac.local = unaligned(&addr->local)->u32; + po->proto.lac.remote = unaligned(&addr->remote)->u32; + atomic_set(&po->proto.lac.sequencing, 1); + po->proto.lac.backlog_rcv = sk_udp->sk_backlog_rcv; + + error = ppp_register_channel(&po->chan); + if (error) + goto out; + + sk->sk_state = PPPOX_CONNECTED; + udp_sk(sk_udp)->encap_type = UDP_ENCAP_L2TPINUDP; + udp_sk(sk_udp)->encap_rcv = pppolac_recv; + sk_udp->sk_backlog_rcv = pppolac_recv_core; + sk_udp->sk_user_data = sk; +out: + if (sock_udp) { + release_sock(sk_udp); + if (error) + sockfd_put(sock_udp); + } + release_sock(sk); + return error; +} + +static int pppolac_release(struct socket *sock) +{ + struct sock *sk = sock->sk; + + if (!sk) + return 0; + + lock_sock(sk); + if (sock_flag(sk, SOCK_DEAD)) { + release_sock(sk); + return -EBADF; + } + + if (sk->sk_state != PPPOX_NONE) { + struct sock *sk_udp = (struct sock *)pppox_sk(sk)->chan.private; + lock_sock(sk_udp); + skb_queue_purge(&sk->sk_receive_queue); + pppox_unbind_sock(sk); + udp_sk(sk_udp)->encap_type = 0; + udp_sk(sk_udp)->encap_rcv = NULL; + sk_udp->sk_backlog_rcv = pppox_sk(sk)->proto.lac.backlog_rcv; + sk_udp->sk_user_data = NULL; + release_sock(sk_udp); + sockfd_put(sk_udp->sk_socket); + } + + sock_orphan(sk); + sock->sk = NULL; + release_sock(sk); + sock_put(sk); + return 0; +} + +/******************************************************************************/ + +static struct proto pppolac_proto = { + .name = "PPPOLAC", + .owner = THIS_MODULE, + .obj_size = sizeof(struct pppox_sock), +}; + +static struct proto_ops pppolac_proto_ops = { + .family = PF_PPPOX, + .owner = THIS_MODULE, + .release = pppolac_release, + .bind = sock_no_bind, + .connect = pppolac_connect, + .socketpair = sock_no_socketpair, + .accept = sock_no_accept, + .getname = sock_no_getname, + .poll = sock_no_poll, + .ioctl = pppox_ioctl, + .listen = sock_no_listen, + .shutdown = sock_no_shutdown, + .setsockopt = sock_no_setsockopt, + .getsockopt = sock_no_getsockopt, + .sendmsg = sock_no_sendmsg, + .recvmsg = sock_no_recvmsg, + .mmap = sock_no_mmap, +}; + +static int pppolac_create(struct net *net, struct socket *sock) +{ + struct sock *sk; + + sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, &pppolac_proto); + if (!sk) + return -ENOMEM; + + sock_init_data(sock, sk); + sock->state = SS_UNCONNECTED; + sock->ops = &pppolac_proto_ops; + sk->sk_protocol = PX_PROTO_OLAC; + sk->sk_state = PPPOX_NONE; + return 0; +} + +/******************************************************************************/ + +static struct pppox_proto pppolac_pppox_proto = { + .create = pppolac_create, + .owner = THIS_MODULE, +}; + +static int __init pppolac_init(void) +{ + int error; + + error = proto_register(&pppolac_proto, 0); + if (error) + return error; + + error = register_pppox_proto(PX_PROTO_OLAC, &pppolac_pppox_proto); + if (error) + proto_unregister(&pppolac_proto); + else + skb_queue_head_init(&delivery_queue); + return error; +} + +static void __exit pppolac_exit(void) +{ + unregister_pppox_proto(PX_PROTO_OLAC); + proto_unregister(&pppolac_proto); +} + +module_init(pppolac_init); +module_exit(pppolac_exit); + +MODULE_DESCRIPTION("PPP on L2TP Access Concentrator (PPPoLAC)"); +MODULE_AUTHOR("Chia-chi Yeh <chiachi@android.com>"); +MODULE_LICENSE("GPL"); |