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af_netrom.c

/*
 * 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.
 *
 * Copyright Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
 * Copyright Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
 * Copyright Darryl Miles G7LED (dlm@g7led.demon.co.uk)
 */
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/stat.h>
#include <net/ax25.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <net/net_namespace.h>
#include <net/sock.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <linux/fcntl.h>
#include <linux/termios.h>    /* For TIOCINQ/OUTQ */
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/notifier.h>
#include <net/netrom.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <net/ip.h>
#include <net/tcp_states.h>
#include <net/arp.h>
#include <linux/init.h>

static int nr_ndevs = 4;

int sysctl_netrom_default_path_quality            = NR_DEFAULT_QUAL;
int sysctl_netrom_obsolescence_count_initialiser  = NR_DEFAULT_OBS;
int sysctl_netrom_network_ttl_initialiser         = NR_DEFAULT_TTL;
int sysctl_netrom_transport_timeout               = NR_DEFAULT_T1;
int sysctl_netrom_transport_maximum_tries         = NR_DEFAULT_N2;
int sysctl_netrom_transport_acknowledge_delay     = NR_DEFAULT_T2;
int sysctl_netrom_transport_busy_delay            = NR_DEFAULT_T4;
int sysctl_netrom_transport_requested_window_size = NR_DEFAULT_WINDOW;
int sysctl_netrom_transport_no_activity_timeout   = NR_DEFAULT_IDLE;
int sysctl_netrom_routing_control                 = NR_DEFAULT_ROUTING;
int sysctl_netrom_link_fails_count                = NR_DEFAULT_FAILS;
int sysctl_netrom_reset_circuit                   = NR_DEFAULT_RESET;

static unsigned short circuit = 0x101;

static HLIST_HEAD(nr_list);
static DEFINE_SPINLOCK(nr_list_lock);

static const struct proto_ops nr_proto_ops;

/*
 * NETROM network devices are virtual network devices encapsulating NETROM
 * frames into AX.25 which will be sent through an AX.25 device, so form a
 * special "super class" of normal net devices; split their locks off into a
 * separate class since they always nest.
 */
static struct lock_class_key nr_netdev_xmit_lock_key;

/*
 *    Socket removal during an interrupt is now safe.
 */
static void nr_remove_socket(struct sock *sk)
{
      spin_lock_bh(&nr_list_lock);
      sk_del_node_init(sk);
      spin_unlock_bh(&nr_list_lock);
}

/*
 *    Kill all bound sockets on a dropped device.
 */
static void nr_kill_by_device(struct net_device *dev)
{
      struct sock *s;
      struct hlist_node *node;

      spin_lock_bh(&nr_list_lock);
      sk_for_each(s, node, &nr_list)
            if (nr_sk(s)->device == dev)
                  nr_disconnect(s, ENETUNREACH);
      spin_unlock_bh(&nr_list_lock);
}

/*
 *    Handle device status changes.
 */
static int nr_device_event(struct notifier_block *this, unsigned long event, void *ptr)
{
      struct net_device *dev = (struct net_device *)ptr;

      if (dev->nd_net != &init_net)
            return NOTIFY_DONE;

      if (event != NETDEV_DOWN)
            return NOTIFY_DONE;

      nr_kill_by_device(dev);
      nr_rt_device_down(dev);

      return NOTIFY_DONE;
}

/*
 *    Add a socket to the bound sockets list.
 */
static void nr_insert_socket(struct sock *sk)
{
      spin_lock_bh(&nr_list_lock);
      sk_add_node(sk, &nr_list);
      spin_unlock_bh(&nr_list_lock);
}

/*
 *    Find a socket that wants to accept the Connect Request we just
 *    received.
 */
static struct sock *nr_find_listener(ax25_address *addr)
{
      struct sock *s;
      struct hlist_node *node;

      spin_lock_bh(&nr_list_lock);
      sk_for_each(s, node, &nr_list)
            if (!ax25cmp(&nr_sk(s)->source_addr, addr) &&
                s->sk_state == TCP_LISTEN) {
                  bh_lock_sock(s);
                  goto found;
            }
      s = NULL;
found:
      spin_unlock_bh(&nr_list_lock);
      return s;
}

/*
 *    Find a connected NET/ROM socket given my circuit IDs.
 */
static struct sock *nr_find_socket(unsigned char index, unsigned char id)
{
      struct sock *s;
      struct hlist_node *node;

      spin_lock_bh(&nr_list_lock);
      sk_for_each(s, node, &nr_list) {
            struct nr_sock *nr = nr_sk(s);

            if (nr->my_index == index && nr->my_id == id) {
                  bh_lock_sock(s);
                  goto found;
            }
      }
      s = NULL;
found:
      spin_unlock_bh(&nr_list_lock);
      return s;
}

/*
 *    Find a connected NET/ROM socket given their circuit IDs.
 */
static struct sock *nr_find_peer(unsigned char index, unsigned char id,
      ax25_address *dest)
{
      struct sock *s;
      struct hlist_node *node;

      spin_lock_bh(&nr_list_lock);
      sk_for_each(s, node, &nr_list) {
            struct nr_sock *nr = nr_sk(s);

            if (nr->your_index == index && nr->your_id == id &&
                !ax25cmp(&nr->dest_addr, dest)) {
                  bh_lock_sock(s);
                  goto found;
            }
      }
      s = NULL;
found:
      spin_unlock_bh(&nr_list_lock);
      return s;
}

/*
 *    Find next free circuit ID.
 */
static unsigned short nr_find_next_circuit(void)
{
      unsigned short id = circuit;
      unsigned char i, j;
      struct sock *sk;

      for (;;) {
            i = id / 256;
            j = id % 256;

            if (i != 0 && j != 0) {
                  if ((sk=nr_find_socket(i, j)) == NULL)
                        break;
                  bh_unlock_sock(sk);
            }

            id++;
      }

      return id;
}

/*
 *    Deferred destroy.
 */
void nr_destroy_socket(struct sock *);

/*
 *    Handler for deferred kills.
 */
static void nr_destroy_timer(unsigned long data)
{
      struct sock *sk=(struct sock *)data;
      bh_lock_sock(sk);
      sock_hold(sk);
      nr_destroy_socket(sk);
      bh_unlock_sock(sk);
      sock_put(sk);
}

/*
 *    This is called from user mode and the timers. Thus it protects itself
 *    against interrupt users but doesn't worry about being called during
 *    work. Once it is removed from the queue no interrupt or bottom half
 *    will touch it and we are (fairly 8-) ) safe.
 */
void nr_destroy_socket(struct sock *sk)
{
      struct sk_buff *skb;

      nr_remove_socket(sk);

      nr_stop_heartbeat(sk);
      nr_stop_t1timer(sk);
      nr_stop_t2timer(sk);
      nr_stop_t4timer(sk);
      nr_stop_idletimer(sk);

      nr_clear_queues(sk);          /* Flush the queues */

      while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
            if (skb->sk != sk) { /* A pending connection */
                  /* Queue the unaccepted socket for death */
                  sock_set_flag(skb->sk, SOCK_DEAD);
                  nr_start_heartbeat(skb->sk);
                  nr_sk(skb->sk)->state = NR_STATE_0;
            }

            kfree_skb(skb);
      }

      if (atomic_read(&sk->sk_wmem_alloc) ||
          atomic_read(&sk->sk_rmem_alloc)) {
            /* Defer: outstanding buffers */
            sk->sk_timer.function = nr_destroy_timer;
            sk->sk_timer.expires  = jiffies + 2 * HZ;
            add_timer(&sk->sk_timer);
      } else
            sock_put(sk);
}

/*
 *    Handling for system calls applied via the various interfaces to a
 *    NET/ROM socket object.
 */

static int nr_setsockopt(struct socket *sock, int level, int optname,
      char __user *optval, int optlen)
{
      struct sock *sk = sock->sk;
      struct nr_sock *nr = nr_sk(sk);
      int opt;

      if (level != SOL_NETROM)
            return -ENOPROTOOPT;

      if (optlen < sizeof(int))
            return -EINVAL;

      if (get_user(opt, (int __user *)optval))
            return -EFAULT;

      switch (optname) {
      case NETROM_T1:
            if (opt < 1)
                  return -EINVAL;
            nr->t1 = opt * HZ;
            return 0;

      case NETROM_T2:
            if (opt < 1)
                  return -EINVAL;
            nr->t2 = opt * HZ;
            return 0;

      case NETROM_N2:
            if (opt < 1 || opt > 31)
                  return -EINVAL;
            nr->n2 = opt;
            return 0;

      case NETROM_T4:
            if (opt < 1)
                  return -EINVAL;
            nr->t4 = opt * HZ;
            return 0;

      case NETROM_IDLE:
            if (opt < 0)
                  return -EINVAL;
            nr->idle = opt * 60 * HZ;
            return 0;

      default:
            return -ENOPROTOOPT;
      }
}

static int nr_getsockopt(struct socket *sock, int level, int optname,
      char __user *optval, int __user *optlen)
{
      struct sock *sk = sock->sk;
      struct nr_sock *nr = nr_sk(sk);
      int val = 0;
      int len;

      if (level != SOL_NETROM)
            return -ENOPROTOOPT;

      if (get_user(len, optlen))
            return -EFAULT;

      if (len < 0)
            return -EINVAL;

      switch (optname) {
      case NETROM_T1:
            val = nr->t1 / HZ;
            break;

      case NETROM_T2:
            val = nr->t2 / HZ;
            break;

      case NETROM_N2:
            val = nr->n2;
            break;

      case NETROM_T4:
            val = nr->t4 / HZ;
            break;

      case NETROM_IDLE:
            val = nr->idle / (60 * HZ);
            break;

      default:
            return -ENOPROTOOPT;
      }

      len = min_t(unsigned int, len, sizeof(int));

      if (put_user(len, optlen))
            return -EFAULT;

      return copy_to_user(optval, &val, len) ? -EFAULT : 0;
}

static int nr_listen(struct socket *sock, int backlog)
{
      struct sock *sk = sock->sk;

      lock_sock(sk);
      if (sk->sk_state != TCP_LISTEN) {
            memset(&nr_sk(sk)->user_addr, 0, AX25_ADDR_LEN);
            sk->sk_max_ack_backlog = backlog;
            sk->sk_state           = TCP_LISTEN;
            release_sock(sk);
            return 0;
      }
      release_sock(sk);

      return -EOPNOTSUPP;
}

static struct proto nr_proto = {
      .name   = "NETROM",
      .owner        = THIS_MODULE,
      .obj_size = sizeof(struct nr_sock),
};

static int nr_create(struct net *net, struct socket *sock, int protocol)
{
      struct sock *sk;
      struct nr_sock *nr;

      if (net != &init_net)
            return -EAFNOSUPPORT;

      if (sock->type != SOCK_SEQPACKET || protocol != 0)
            return -ESOCKTNOSUPPORT;

      sk = sk_alloc(net, PF_NETROM, GFP_ATOMIC, &nr_proto);
      if (sk  == NULL)
            return -ENOMEM;

      nr = nr_sk(sk);

      sock_init_data(sock, sk);

      sock->ops    = &nr_proto_ops;
      sk->sk_protocol = protocol;

      skb_queue_head_init(&nr->ack_queue);
      skb_queue_head_init(&nr->reseq_queue);
      skb_queue_head_init(&nr->frag_queue);

      nr_init_timers(sk);

      nr->t1     =
            msecs_to_jiffies(sysctl_netrom_transport_timeout);
      nr->t2     =
            msecs_to_jiffies(sysctl_netrom_transport_acknowledge_delay);
      nr->n2     =
            msecs_to_jiffies(sysctl_netrom_transport_maximum_tries);
      nr->t4     =
            msecs_to_jiffies(sysctl_netrom_transport_busy_delay);
      nr->idle   =
            msecs_to_jiffies(sysctl_netrom_transport_no_activity_timeout);
      nr->window = sysctl_netrom_transport_requested_window_size;

      nr->bpqext = 1;
      nr->state  = NR_STATE_0;

      return 0;
}

static struct sock *nr_make_new(struct sock *osk)
{
      struct sock *sk;
      struct nr_sock *nr, *onr;

      if (osk->sk_type != SOCK_SEQPACKET)
            return NULL;

      sk = sk_alloc(osk->sk_net, PF_NETROM, GFP_ATOMIC, osk->sk_prot);
      if (sk == NULL)
            return NULL;

      nr = nr_sk(sk);

      sock_init_data(NULL, sk);

      sk->sk_type     = osk->sk_type;
      sk->sk_socket   = osk->sk_socket;
      sk->sk_priority = osk->sk_priority;
      sk->sk_protocol = osk->sk_protocol;
      sk->sk_rcvbuf   = osk->sk_rcvbuf;
      sk->sk_sndbuf   = osk->sk_sndbuf;
      sk->sk_state    = TCP_ESTABLISHED;
      sk->sk_sleep    = osk->sk_sleep;
      sock_copy_flags(sk, osk);

      skb_queue_head_init(&nr->ack_queue);
      skb_queue_head_init(&nr->reseq_queue);
      skb_queue_head_init(&nr->frag_queue);

      nr_init_timers(sk);

      onr = nr_sk(osk);

      nr->t1      = onr->t1;
      nr->t2      = onr->t2;
      nr->n2      = onr->n2;
      nr->t4      = onr->t4;
      nr->idle    = onr->idle;
      nr->window  = onr->window;

      nr->device  = onr->device;
      nr->bpqext  = onr->bpqext;

      return sk;
}

static int nr_release(struct socket *sock)
{
      struct sock *sk = sock->sk;
      struct nr_sock *nr;

      if (sk == NULL) return 0;

      sock_hold(sk);
      lock_sock(sk);
      nr = nr_sk(sk);

      switch (nr->state) {
      case NR_STATE_0:
      case NR_STATE_1:
      case NR_STATE_2:
            nr_disconnect(sk, 0);
            nr_destroy_socket(sk);
            break;

      case NR_STATE_3:
            nr_clear_queues(sk);
            nr->n2count = 0;
            nr_write_internal(sk, NR_DISCREQ);
            nr_start_t1timer(sk);
            nr_stop_t2timer(sk);
            nr_stop_t4timer(sk);
            nr_stop_idletimer(sk);
            nr->state    = NR_STATE_2;
            sk->sk_state    = TCP_CLOSE;
            sk->sk_shutdown |= SEND_SHUTDOWN;
            sk->sk_state_change(sk);
            sock_orphan(sk);
            sock_set_flag(sk, SOCK_DESTROY);
            sk->sk_socket   = NULL;
            break;

      default:
            sk->sk_socket = NULL;
            break;
      }

      sock->sk   = NULL;
      release_sock(sk);
      sock_put(sk);

      return 0;
}

static int nr_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
{
      struct sock *sk = sock->sk;
      struct nr_sock *nr = nr_sk(sk);
      struct full_sockaddr_ax25 *addr = (struct full_sockaddr_ax25 *)uaddr;
      struct net_device *dev;
      ax25_uid_assoc *user;
      ax25_address *source;

      lock_sock(sk);
      if (!sock_flag(sk, SOCK_ZAPPED)) {
            release_sock(sk);
            return -EINVAL;
      }
      if (addr_len < sizeof(struct sockaddr_ax25) || addr_len > sizeof(struct full_sockaddr_ax25)) {
            release_sock(sk);
            return -EINVAL;
      }
      if (addr_len < (addr->fsa_ax25.sax25_ndigis * sizeof(ax25_address) + sizeof(struct sockaddr_ax25))) {
            release_sock(sk);
            return -EINVAL;
      }
      if (addr->fsa_ax25.sax25_family != AF_NETROM) {
            release_sock(sk);
            return -EINVAL;
      }
      if ((dev = nr_dev_get(&addr->fsa_ax25.sax25_call)) == NULL) {
            SOCK_DEBUG(sk, "NET/ROM: bind failed: invalid node callsign\n");
            release_sock(sk);
            return -EADDRNOTAVAIL;
      }

      /*
       * Only the super user can set an arbitrary user callsign.
       */
      if (addr->fsa_ax25.sax25_ndigis == 1) {
            if (!capable(CAP_NET_BIND_SERVICE)) {
                  dev_put(dev);
                  release_sock(sk);
                  return -EACCES;
            }
            nr->user_addr   = addr->fsa_digipeater[0];
            nr->source_addr = addr->fsa_ax25.sax25_call;
      } else {
            source = &addr->fsa_ax25.sax25_call;

            user = ax25_findbyuid(current->euid);
            if (user) {
                  nr->user_addr   = user->call;
                  ax25_uid_put(user);
            } else {
                  if (ax25_uid_policy && !capable(CAP_NET_BIND_SERVICE)) {
                        release_sock(sk);
                        dev_put(dev);
                        return -EPERM;
                  }
                  nr->user_addr   = *source;
            }

            nr->source_addr = *source;
      }

      nr->device = dev;
      nr_insert_socket(sk);

      sock_reset_flag(sk, SOCK_ZAPPED);
      dev_put(dev);
      release_sock(sk);
      SOCK_DEBUG(sk, "NET/ROM: socket is bound\n");
      return 0;
}

static int nr_connect(struct socket *sock, struct sockaddr *uaddr,
      int addr_len, int flags)
{
      struct sock *sk = sock->sk;
      struct nr_sock *nr = nr_sk(sk);
      struct sockaddr_ax25 *addr = (struct sockaddr_ax25 *)uaddr;
      ax25_address *source = NULL;
      ax25_uid_assoc *user;
      struct net_device *dev;
      int err = 0;

      lock_sock(sk);
      if (sk->sk_state == TCP_ESTABLISHED && sock->state == SS_CONNECTING) {
            sock->state = SS_CONNECTED;
            goto out_release; /* Connect completed during a ERESTARTSYS event */
      }

      if (sk->sk_state == TCP_CLOSE && sock->state == SS_CONNECTING) {
            sock->state = SS_UNCONNECTED;
            err = -ECONNREFUSED;
            goto out_release;
      }

      if (sk->sk_state == TCP_ESTABLISHED) {
            err = -EISCONN;   /* No reconnect on a seqpacket socket */
            goto out_release;
      }

      sk->sk_state   = TCP_CLOSE;
      sock->state = SS_UNCONNECTED;

      if (addr_len != sizeof(struct sockaddr_ax25) && addr_len != sizeof(struct full_sockaddr_ax25)) {
            err = -EINVAL;
            goto out_release;
      }
      if (addr->sax25_family != AF_NETROM) {
            err = -EINVAL;
            goto out_release;
      }
      if (sock_flag(sk, SOCK_ZAPPED)) {   /* Must bind first - autobinding in this may or may not work */
            sock_reset_flag(sk, SOCK_ZAPPED);

            if ((dev = nr_dev_first()) == NULL) {
                  err = -ENETUNREACH;
                  goto out_release;
            }
            source = (ax25_address *)dev->dev_addr;

            user = ax25_findbyuid(current->euid);
            if (user) {
                  nr->user_addr   = user->call;
                  ax25_uid_put(user);
            } else {
                  if (ax25_uid_policy && !capable(CAP_NET_ADMIN)) {
                        dev_put(dev);
                        err = -EPERM;
                        goto out_release;
                  }
                  nr->user_addr   = *source;
            }

            nr->source_addr = *source;
            nr->device      = dev;

            dev_put(dev);
            nr_insert_socket(sk);         /* Finish the bind */
      }

      nr->dest_addr = addr->sax25_call;

      release_sock(sk);
      circuit = nr_find_next_circuit();
      lock_sock(sk);

      nr->my_index = circuit / 256;
      nr->my_id    = circuit % 256;

      circuit++;

      /* Move to connecting socket, start sending Connect Requests */
      sock->state  = SS_CONNECTING;
      sk->sk_state = TCP_SYN_SENT;

      nr_establish_data_link(sk);

      nr->state = NR_STATE_1;

      nr_start_heartbeat(sk);

      /* Now the loop */
      if (sk->sk_state != TCP_ESTABLISHED && (flags & O_NONBLOCK)) {
            err = -EINPROGRESS;
            goto out_release;
      }

      /*
       * A Connect Ack with Choke or timeout or failed routing will go to
       * closed.
       */
      if (sk->sk_state == TCP_SYN_SENT) {
            DEFINE_WAIT(wait);

            for (;;) {
                  prepare_to_wait(sk->sk_sleep, &wait,
                              TASK_INTERRUPTIBLE);
                  if (sk->sk_state != TCP_SYN_SENT)
                        break;
                  if (!signal_pending(current)) {
                        release_sock(sk);
                        schedule();
                        lock_sock(sk);
                        continue;
                  }
                  err = -ERESTARTSYS;
                  break;
            }
            finish_wait(sk->sk_sleep, &wait);
            if (err)
                  goto out_release;
      }

      if (sk->sk_state != TCP_ESTABLISHED) {
            sock->state = SS_UNCONNECTED;
            err = sock_error(sk);   /* Always set at this point */
            goto out_release;
      }

      sock->state = SS_CONNECTED;

out_release:
      release_sock(sk);

      return err;
}

static int nr_accept(struct socket *sock, struct socket *newsock, int flags)
{
      struct sk_buff *skb;
      struct sock *newsk;
      DEFINE_WAIT(wait);
      struct sock *sk;
      int err = 0;

      if ((sk = sock->sk) == NULL)
            return -EINVAL;

      lock_sock(sk);
      if (sk->sk_type != SOCK_SEQPACKET) {
            err = -EOPNOTSUPP;
            goto out_release;
      }

      if (sk->sk_state != TCP_LISTEN) {
            err = -EINVAL;
            goto out_release;
      }

      /*
       *    The write queue this time is holding sockets ready to use
       *    hooked into the SABM we saved
       */
      for (;;) {
            prepare_to_wait(sk->sk_sleep, &wait, TASK_INTERRUPTIBLE);
            skb = skb_dequeue(&sk->sk_receive_queue);
            if (skb)
                  break;

            if (flags & O_NONBLOCK) {
                  err = -EWOULDBLOCK;
                  break;
            }
            if (!signal_pending(current)) {
                  release_sock(sk);
                  schedule();
                  lock_sock(sk);
                  continue;
            }
            err = -ERESTARTSYS;
            break;
      }
      finish_wait(sk->sk_sleep, &wait);
      if (err)
            goto out_release;

      newsk = skb->sk;
      newsk->sk_socket = newsock;
      newsk->sk_sleep = &newsock->wait;

      /* Now attach up the new socket */
      kfree_skb(skb);
      sk_acceptq_removed(sk);
      newsock->sk = newsk;

out_release:
      release_sock(sk);

      return err;
}

static int nr_getname(struct socket *sock, struct sockaddr *uaddr,
      int *uaddr_len, int peer)
{
      struct full_sockaddr_ax25 *sax = (struct full_sockaddr_ax25 *)uaddr;
      struct sock *sk = sock->sk;
      struct nr_sock *nr = nr_sk(sk);

      lock_sock(sk);
      if (peer != 0) {
            if (sk->sk_state != TCP_ESTABLISHED) {
                  release_sock(sk);
                  return -ENOTCONN;
            }
            sax->fsa_ax25.sax25_family = AF_NETROM;
            sax->fsa_ax25.sax25_ndigis = 1;
            sax->fsa_ax25.sax25_call   = nr->user_addr;
            sax->fsa_digipeater[0]     = nr->dest_addr;
            *uaddr_len = sizeof(struct full_sockaddr_ax25);
      } else {
            sax->fsa_ax25.sax25_family = AF_NETROM;
            sax->fsa_ax25.sax25_ndigis = 0;
            sax->fsa_ax25.sax25_call   = nr->source_addr;
            *uaddr_len = sizeof(struct sockaddr_ax25);
      }
      release_sock(sk);

      return 0;
}

int nr_rx_frame(struct sk_buff *skb, struct net_device *dev)
{
      struct sock *sk;
      struct sock *make;
      struct nr_sock *nr_make;
      ax25_address *src, *dest, *user;
      unsigned short circuit_index, circuit_id;
      unsigned short peer_circuit_index, peer_circuit_id;
      unsigned short frametype, flags, window, timeout;
      int ret;

      skb->sk = NULL;         /* Initially we don't know who it's for */

      /*
       *    skb->data points to the netrom frame start
       */

      src  = (ax25_address *)(skb->data + 0);
      dest = (ax25_address *)(skb->data + 7);

      circuit_index      = skb->data[15];
      circuit_id         = skb->data[16];
      peer_circuit_index = skb->data[17];
      peer_circuit_id    = skb->data[18];
      frametype          = skb->data[19] & 0x0F;
      flags              = skb->data[19] & 0xF0;

      /*
       * Check for an incoming IP over NET/ROM frame.
       */
      if (frametype == NR_PROTOEXT &&
          circuit_index == NR_PROTO_IP && circuit_id == NR_PROTO_IP) {
            skb_pull(skb, NR_NETWORK_LEN + NR_TRANSPORT_LEN);
            skb_reset_transport_header(skb);

            return nr_rx_ip(skb, dev);
      }

      /*
       * Find an existing socket connection, based on circuit ID, if it's
       * a Connect Request base it on their circuit ID.
       *
       * Circuit ID 0/0 is not valid but it could still be a "reset" for a
       * circuit that no longer exists at the other end ...
       */

      sk = NULL;

      if (circuit_index == 0 && circuit_id == 0) {
            if (frametype == NR_CONNACK && flags == NR_CHOKE_FLAG)
                  sk = nr_find_peer(peer_circuit_index, peer_circuit_id, src);
      } else {
            if (frametype == NR_CONNREQ)
                  sk = nr_find_peer(circuit_index, circuit_id, src);
            else
                  sk = nr_find_socket(circuit_index, circuit_id);
      }

      if (sk != NULL) {
            skb_reset_transport_header(skb);

            if (frametype == NR_CONNACK && skb->len == 22)
                  nr_sk(sk)->bpqext = 1;
            else
                  nr_sk(sk)->bpqext = 0;

            ret = nr_process_rx_frame(sk, skb);
            bh_unlock_sock(sk);
            return ret;
      }

      /*
       * Now it should be a CONNREQ.
       */
      if (frametype != NR_CONNREQ) {
            /*
             * Here it would be nice to be able to send a reset but
             * NET/ROM doesn't have one.  We've tried to extend the protocol
             * by sending NR_CONNACK | NR_CHOKE_FLAGS replies but that
             * apparently kills BPQ boxes... :-(
             * So now we try to follow the established behaviour of
             * G8PZT's Xrouter which is sending packets with command type 7
             * as an extension of the protocol.
             */
            if (sysctl_netrom_reset_circuit &&
                (frametype != NR_RESET || flags != 0))
                  nr_transmit_reset(skb, 1);

            return 0;
      }

      sk = nr_find_listener(dest);

      user = (ax25_address *)(skb->data + 21);

      if (sk == NULL || sk_acceptq_is_full(sk) ||
          (make = nr_make_new(sk)) == NULL) {
            nr_transmit_refusal(skb, 0);
            if (sk)
                  bh_unlock_sock(sk);
            return 0;
      }

      window = skb->data[20];

      skb->sk             = make;
      make->sk_state        = TCP_ESTABLISHED;

      /* Fill in his circuit details */
      nr_make = nr_sk(make);
      nr_make->source_addr = *dest;
      nr_make->dest_addr   = *src;
      nr_make->user_addr   = *user;

      nr_make->your_index  = circuit_index;
      nr_make->your_id     = circuit_id;

      bh_unlock_sock(sk);
      circuit = nr_find_next_circuit();
      bh_lock_sock(sk);

      nr_make->my_index    = circuit / 256;
      nr_make->my_id       = circuit % 256;

      circuit++;

      /* Window negotiation */
      if (window < nr_make->window)
            nr_make->window = window;

      /* L4 timeout negotiation */
      if (skb->len == 37) {
            timeout = skb->data[36] * 256 + skb->data[35];
            if (timeout * HZ < nr_make->t1)
                  nr_make->t1 = timeout * HZ;
            nr_make->bpqext = 1;
      } else {
            nr_make->bpqext = 0;
      }

      nr_write_internal(make, NR_CONNACK);

      nr_make->condition = 0x00;
      nr_make->vs        = 0;
      nr_make->va        = 0;
      nr_make->vr        = 0;
      nr_make->vl        = 0;
      nr_make->state     = NR_STATE_3;
      sk_acceptq_added(sk);
      skb_queue_head(&sk->sk_receive_queue, skb);

      if (!sock_flag(sk, SOCK_DEAD))
            sk->sk_data_ready(sk, skb->len);

      bh_unlock_sock(sk);

      nr_insert_socket(make);

      nr_start_heartbeat(make);
      nr_start_idletimer(make);

      return 1;
}

static int nr_sendmsg(struct kiocb *iocb, struct socket *sock,
                  struct msghdr *msg, size_t len)
{
      struct sock *sk = sock->sk;
      struct nr_sock *nr = nr_sk(sk);
      struct sockaddr_ax25 *usax = (struct sockaddr_ax25 *)msg->msg_name;
      int err;
      struct sockaddr_ax25 sax;
      struct sk_buff *skb;
      unsigned char *asmptr;
      int size;

      if (msg->msg_flags & ~(MSG_DONTWAIT|MSG_EOR|MSG_CMSG_COMPAT))
            return -EINVAL;

      lock_sock(sk);
      if (sock_flag(sk, SOCK_ZAPPED)) {
            err = -EADDRNOTAVAIL;
            goto out;
      }

      if (sk->sk_shutdown & SEND_SHUTDOWN) {
            send_sig(SIGPIPE, current, 0);
            err = -EPIPE;
            goto out;
      }

      if (nr->device == NULL) {
            err = -ENETUNREACH;
            goto out;
      }

      if (usax) {
            if (msg->msg_namelen < sizeof(sax)) {
                  err = -EINVAL;
                  goto out;
            }
            sax = *usax;
            if (ax25cmp(&nr->dest_addr, &sax.sax25_call) != 0) {
                  err = -EISCONN;
                  goto out;
            }
            if (sax.sax25_family != AF_NETROM) {
                  err = -EINVAL;
                  goto out;
            }
      } else {
            if (sk->sk_state != TCP_ESTABLISHED) {
                  err = -ENOTCONN;
                  goto out;
            }
            sax.sax25_family = AF_NETROM;
            sax.sax25_call   = nr->dest_addr;
      }

      SOCK_DEBUG(sk, "NET/ROM: sendto: Addresses built.\n");

      /* Build a packet */
      SOCK_DEBUG(sk, "NET/ROM: sendto: building packet.\n");
      size = len + NR_NETWORK_LEN + NR_TRANSPORT_LEN;

      if ((skb = sock_alloc_send_skb(sk, size, msg->msg_flags & MSG_DONTWAIT, &err)) == NULL)
            goto out;

      skb_reserve(skb, size - len);
      skb_reset_transport_header(skb);

      /*
       *    Push down the NET/ROM header
       */

      asmptr = skb_push(skb, NR_TRANSPORT_LEN);
      SOCK_DEBUG(sk, "Building NET/ROM Header.\n");

      /* Build a NET/ROM Transport header */

      *asmptr++ = nr->your_index;
      *asmptr++ = nr->your_id;
      *asmptr++ = 0;          /* To be filled in later */
      *asmptr++ = 0;          /*      Ditto            */
      *asmptr++ = NR_INFO;
      SOCK_DEBUG(sk, "Built header.\n");

      /*
       *    Put the data on the end
       */
      skb_put(skb, len);

      SOCK_DEBUG(sk, "NET/ROM: Appending user data\n");

      /* User data follows immediately after the NET/ROM transport header */
      if (memcpy_fromiovec(skb_transport_header(skb), msg->msg_iov, len)) {
            kfree_skb(skb);
            err = -EFAULT;
            goto out;
      }

      SOCK_DEBUG(sk, "NET/ROM: Transmitting buffer\n");

      if (sk->sk_state != TCP_ESTABLISHED) {
            kfree_skb(skb);
            err = -ENOTCONN;
            goto out;
      }

      nr_output(sk, skb);     /* Shove it onto the queue */

      err = len;
out:
      release_sock(sk);
      return err;
}

static int nr_recvmsg(struct kiocb *iocb, struct socket *sock,
                  struct msghdr *msg, size_t size, int flags)
{
      struct sock *sk = sock->sk;
      struct sockaddr_ax25 *sax = (struct sockaddr_ax25 *)msg->msg_name;
      size_t copied;
      struct sk_buff *skb;
      int er;

      /*
       * This works for seqpacket too. The receiver has ordered the queue for
       * us! We do one quick check first though
       */

      lock_sock(sk);
      if (sk->sk_state != TCP_ESTABLISHED) {
            release_sock(sk);
            return -ENOTCONN;
      }

      /* Now we can treat all alike */
      if ((skb = skb_recv_datagram(sk, flags & ~MSG_DONTWAIT, flags & MSG_DONTWAIT, &er)) == NULL) {
            release_sock(sk);
            return er;
      }

      skb_reset_transport_header(skb);
      copied     = skb->len;

      if (copied > size) {
            copied = size;
            msg->msg_flags |= MSG_TRUNC;
      }

      skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);

      if (sax != NULL) {
            sax->sax25_family = AF_NETROM;
            skb_copy_from_linear_data_offset(skb, 7, sax->sax25_call.ax25_call,
                        AX25_ADDR_LEN);
      }

      msg->msg_namelen = sizeof(*sax);

      skb_free_datagram(sk, skb);

      release_sock(sk);
      return copied;
}


static int nr_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
{
      struct sock *sk = sock->sk;
      void __user *argp = (void __user *)arg;
      int ret;

      switch (cmd) {
      case TIOCOUTQ: {
            long amount;

            lock_sock(sk);
            amount = sk->sk_sndbuf - atomic_read(&sk->sk_wmem_alloc);
            if (amount < 0)
                  amount = 0;
            release_sock(sk);
            return put_user(amount, (int __user *)argp);
      }

      case TIOCINQ: {
            struct sk_buff *skb;
            long amount = 0L;

            lock_sock(sk);
            /* These two are safe on a single CPU system as only user tasks fiddle here */
            if ((skb = skb_peek(&sk->sk_receive_queue)) != NULL)
                  amount = skb->len;
            release_sock(sk);
            return put_user(amount, (int __user *)argp);
      }

      case SIOCGSTAMP:
            lock_sock(sk);
            ret = sock_get_timestamp(sk, argp);
            release_sock(sk);
            return ret;

      case SIOCGSTAMPNS:
            lock_sock(sk);
            ret = sock_get_timestampns(sk, argp);
            release_sock(sk);
            return ret;

      case SIOCGIFADDR:
      case SIOCSIFADDR:
      case SIOCGIFDSTADDR:
      case SIOCSIFDSTADDR:
      case SIOCGIFBRDADDR:
      case SIOCSIFBRDADDR:
      case SIOCGIFNETMASK:
      case SIOCSIFNETMASK:
      case SIOCGIFMETRIC:
      case SIOCSIFMETRIC:
            return -EINVAL;

      case SIOCADDRT:
      case SIOCDELRT:
      case SIOCNRDECOBS:
            if (!capable(CAP_NET_ADMIN)) return -EPERM;
            return nr_rt_ioctl(cmd, argp);

      default:
            return -ENOIOCTLCMD;
      }

      return 0;
}

#ifdef CONFIG_PROC_FS

static void *nr_info_start(struct seq_file *seq, loff_t *pos)
{
      struct sock *s;
      struct hlist_node *node;
      int i = 1;

      spin_lock_bh(&nr_list_lock);
      if (*pos == 0)
            return SEQ_START_TOKEN;

      sk_for_each(s, node, &nr_list) {
            if (i == *pos)
                  return s;
            ++i;
      }
      return NULL;
}

static void *nr_info_next(struct seq_file *seq, void *v, loff_t *pos)
{
      ++*pos;

      return (v == SEQ_START_TOKEN) ? sk_head(&nr_list)
            : sk_next((struct sock *)v);
}

static void nr_info_stop(struct seq_file *seq, void *v)
{
      spin_unlock_bh(&nr_list_lock);
}

static int nr_info_show(struct seq_file *seq, void *v)
{
      struct sock *s = v;
      struct net_device *dev;
      struct nr_sock *nr;
      const char *devname;
      char buf[11];

      if (v == SEQ_START_TOKEN)
            seq_puts(seq,
"user_addr dest_node src_node  dev    my  your  st  vs  vr  va    t1     t2     t4      idle   n2  wnd Snd-Q Rcv-Q inode\n");

      else {

            bh_lock_sock(s);
            nr = nr_sk(s);

            if ((dev = nr->device) == NULL)
                  devname = "???";
            else
                  devname = dev->name;

            seq_printf(seq, "%-9s ", ax2asc(buf, &nr->user_addr));
            seq_printf(seq, "%-9s ", ax2asc(buf, &nr->dest_addr));
            seq_printf(seq,
"%-9s %-3s  %02X/%02X %02X/%02X %2d %3d %3d %3d %3lu/%03lu %2lu/%02lu %3lu/%03lu %3lu/%03lu %2d/%02d %3d %5d %5d %ld\n",
                  ax2asc(buf, &nr->source_addr),
                  devname,
                  nr->my_index,
                  nr->my_id,
                  nr->your_index,
                  nr->your_id,
                  nr->state,
                  nr->vs,
                  nr->vr,
                  nr->va,
                  ax25_display_timer(&nr->t1timer) / HZ,
                  nr->t1 / HZ,
                  ax25_display_timer(&nr->t2timer) / HZ,
                  nr->t2 / HZ,
                  ax25_display_timer(&nr->t4timer) / HZ,
                  nr->t4 / HZ,
                  ax25_display_timer(&nr->idletimer) / (60 * HZ),
                  nr->idle / (60 * HZ),
                  nr->n2count,
                  nr->n2,
                  nr->window,
                  atomic_read(&s->sk_wmem_alloc),
                  atomic_read(&s->sk_rmem_alloc),
                  s->sk_socket ? SOCK_INODE(s->sk_socket)->i_ino : 0L);

            bh_unlock_sock(s);
      }
      return 0;
}

static const struct seq_operations nr_info_seqops = {
      .start = nr_info_start,
      .next = nr_info_next,
      .stop = nr_info_stop,
      .show = nr_info_show,
};

static int nr_info_open(struct inode *inode, struct file *file)
{
      return seq_open(file, &nr_info_seqops);
}

static const struct file_operations nr_info_fops = {
      .owner = THIS_MODULE,
      .open = nr_info_open,
      .read = seq_read,
      .llseek = seq_lseek,
      .release = seq_release,
};
#endif      /* CONFIG_PROC_FS */

static struct net_proto_family nr_family_ops = {
      .family           =     PF_NETROM,
      .create           =     nr_create,
      .owner            =     THIS_MODULE,
};

static const struct proto_ops nr_proto_ops = {
      .family           =     PF_NETROM,
      .owner            =     THIS_MODULE,
      .release    =     nr_release,
      .bind       =     nr_bind,
      .connect    =     nr_connect,
      .socketpair =     sock_no_socketpair,
      .accept           =     nr_accept,
      .getname    =     nr_getname,
      .poll       =     datagram_poll,
      .ioctl            =     nr_ioctl,
      .listen           =     nr_listen,
      .shutdown   =     sock_no_shutdown,
      .setsockopt =     nr_setsockopt,
      .getsockopt =     nr_getsockopt,
      .sendmsg    =     nr_sendmsg,
      .recvmsg    =     nr_recvmsg,
      .mmap       =     sock_no_mmap,
      .sendpage   =     sock_no_sendpage,
};

static struct notifier_block nr_dev_notifier = {
      .notifier_call    =     nr_device_event,
};

static struct net_device **dev_nr;

static struct ax25_protocol nr_pid = {
      .pid  = AX25_P_NETROM,
      .func = nr_route_frame
};

static struct ax25_linkfail nr_linkfail_notifier = {
      .func = nr_link_failed,
};

static int __init nr_proto_init(void)
{
      int i;
      int rc = proto_register(&nr_proto, 0);

      if (rc != 0)
            goto out;

      if (nr_ndevs > 0x7fffffff/sizeof(struct net_device *)) {
            printk(KERN_ERR "NET/ROM: nr_proto_init - nr_ndevs parameter to large\n");
            return -1;
      }

      dev_nr = kzalloc(nr_ndevs * sizeof(struct net_device *), GFP_KERNEL);
      if (dev_nr == NULL) {
            printk(KERN_ERR "NET/ROM: nr_proto_init - unable to allocate device array\n");
            return -1;
      }

      for (i = 0; i < nr_ndevs; i++) {
            char name[IFNAMSIZ];
            struct net_device *dev;

            sprintf(name, "nr%d", i);
            dev = alloc_netdev(sizeof(struct nr_private), name, nr_setup);
            if (!dev) {
                  printk(KERN_ERR "NET/ROM: nr_proto_init - unable to allocate device structure\n");
                  goto fail;
            }

            dev->base_addr = i;
            if (register_netdev(dev)) {
                  printk(KERN_ERR "NET/ROM: nr_proto_init - unable to register network device\n");
                  free_netdev(dev);
                  goto fail;
            }
            lockdep_set_class(&dev->_xmit_lock, &nr_netdev_xmit_lock_key);
            dev_nr[i] = dev;
      }

      if (sock_register(&nr_family_ops)) {
            printk(KERN_ERR "NET/ROM: nr_proto_init - unable to register socket family\n");
            goto fail;
      }

      register_netdevice_notifier(&nr_dev_notifier);

      ax25_register_pid(&nr_pid);
      ax25_linkfail_register(&nr_linkfail_notifier);

#ifdef CONFIG_SYSCTL
      nr_register_sysctl();
#endif

      nr_loopback_init();

      proc_net_fops_create(&init_net, "nr", S_IRUGO, &nr_info_fops);
      proc_net_fops_create(&init_net, "nr_neigh", S_IRUGO, &nr_neigh_fops);
      proc_net_fops_create(&init_net, "nr_nodes", S_IRUGO, &nr_nodes_fops);
out:
      return rc;
fail:
      while (--i >= 0) {
            unregister_netdev(dev_nr[i]);
            free_netdev(dev_nr[i]);
      }
      kfree(dev_nr);
      proto_unregister(&nr_proto);
      rc = -1;
      goto out;
}

module_init(nr_proto_init);

module_param(nr_ndevs, int, 0);
MODULE_PARM_DESC(nr_ndevs, "number of NET/ROM devices");

MODULE_AUTHOR("Jonathan Naylor G4KLX <g4klx@g4klx.demon.co.uk>");
MODULE_DESCRIPTION("The amateur radio NET/ROM network and transport layer protocol");
MODULE_LICENSE("GPL");
MODULE_ALIAS_NETPROTO(PF_NETROM);

static void __exit nr_exit(void)
{
      int i;

      proc_net_remove(&init_net, "nr");
      proc_net_remove(&init_net, "nr_neigh");
      proc_net_remove(&init_net, "nr_nodes");
      nr_loopback_clear();

      nr_rt_free();

#ifdef CONFIG_SYSCTL
      nr_unregister_sysctl();
#endif

      ax25_linkfail_release(&nr_linkfail_notifier);
      ax25_protocol_release(AX25_P_NETROM);

      unregister_netdevice_notifier(&nr_dev_notifier);

      sock_unregister(PF_NETROM);

      for (i = 0; i < nr_ndevs; i++) {
            struct net_device *dev = dev_nr[i];
            if (dev) {
                  unregister_netdev(dev);
                  free_netdev(dev);
            }
      }

      kfree(dev_nr);
      proto_unregister(&nr_proto);
}
module_exit(nr_exit);

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