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inet_connection_sock.c

/*
 * INET           An implementation of the TCP/IP protocol suite for the LINUX
 *          operating system.  INET is implemented using the  BSD Socket
 *          interface as the means of communication with the user level.
 *
 *          Support for INET connection oriented protocols.
 *
 * Authors: See the TCP sources
 *
 *          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/module.h>
#include <linux/jhash.h>

#include <net/inet_connection_sock.h>
#include <net/inet_hashtables.h>
#include <net/inet_timewait_sock.h>
#include <net/ip.h>
#include <net/route.h>
#include <net/tcp_states.h>
#include <net/xfrm.h>

#ifdef INET_CSK_DEBUG
const char inet_csk_timer_bug_msg[] = "inet_csk BUG: unknown timer value\n";
EXPORT_SYMBOL(inet_csk_timer_bug_msg);
#endif

/*
 * This array holds the first and last local port number.
 */
int sysctl_local_port_range[2] = { 32768, 61000 };
DEFINE_SEQLOCK(sysctl_port_range_lock);

void inet_get_local_port_range(int *low, int *high)
{
      unsigned seq;
      do {
            seq = read_seqbegin(&sysctl_port_range_lock);

            *low = sysctl_local_port_range[0];
            *high = sysctl_local_port_range[1];
      } while (read_seqretry(&sysctl_port_range_lock, seq));
}
EXPORT_SYMBOL(inet_get_local_port_range);

int inet_csk_bind_conflict(const struct sock *sk,
                     const struct inet_bind_bucket *tb)
{
      const __be32 sk_rcv_saddr = inet_rcv_saddr(sk);
      struct sock *sk2;
      struct hlist_node *node;
      int reuse = sk->sk_reuse;

      sk_for_each_bound(sk2, node, &tb->owners) {
            if (sk != sk2 &&
                !inet_v6_ipv6only(sk2) &&
                (!sk->sk_bound_dev_if ||
                 !sk2->sk_bound_dev_if ||
                 sk->sk_bound_dev_if == sk2->sk_bound_dev_if)) {
                  if (!reuse || !sk2->sk_reuse ||
                      sk2->sk_state == TCP_LISTEN) {
                        const __be32 sk2_rcv_saddr = inet_rcv_saddr(sk2);
                        if (!sk2_rcv_saddr || !sk_rcv_saddr ||
                            sk2_rcv_saddr == sk_rcv_saddr)
                              break;
                  }
            }
      }
      return node != NULL;
}

EXPORT_SYMBOL_GPL(inet_csk_bind_conflict);

/* Obtain a reference to a local port for the given sock,
 * if snum is zero it means select any available local port.
 */
int inet_csk_get_port(struct inet_hashinfo *hashinfo,
                  struct sock *sk, unsigned short snum,
                  int (*bind_conflict)(const struct sock *sk,
                                 const struct inet_bind_bucket *tb))
{
      struct inet_bind_hashbucket *head;
      struct hlist_node *node;
      struct inet_bind_bucket *tb;
      int ret;

      local_bh_disable();
      if (!snum) {
            int remaining, rover, low, high;

            inet_get_local_port_range(&low, &high);
            remaining = (high - low) + 1;
            rover = net_random() % remaining + low;

            do {
                  head = &hashinfo->bhash[inet_bhashfn(rover, hashinfo->bhash_size)];
                  spin_lock(&head->lock);
                  inet_bind_bucket_for_each(tb, node, &head->chain)
                        if (tb->port == rover)
                              goto next;
                  break;
            next:
                  spin_unlock(&head->lock);
                  if (++rover > high)
                        rover = low;
            } while (--remaining > 0);

            /* Exhausted local port range during search?  It is not
             * possible for us to be holding one of the bind hash
             * locks if this test triggers, because if 'remaining'
             * drops to zero, we broke out of the do/while loop at
             * the top level, not from the 'break;' statement.
             */
            ret = 1;
            if (remaining <= 0)
                  goto fail;

            /* OK, here is the one we will use.  HEAD is
             * non-NULL and we hold it's mutex.
             */
            snum = rover;
      } else {
            head = &hashinfo->bhash[inet_bhashfn(snum, hashinfo->bhash_size)];
            spin_lock(&head->lock);
            inet_bind_bucket_for_each(tb, node, &head->chain)
                  if (tb->port == snum)
                        goto tb_found;
      }
      tb = NULL;
      goto tb_not_found;
tb_found:
      if (!hlist_empty(&tb->owners)) {
            if (sk->sk_reuse > 1)
                  goto success;
            if (tb->fastreuse > 0 &&
                sk->sk_reuse && sk->sk_state != TCP_LISTEN) {
                  goto success;
            } else {
                  ret = 1;
                  if (bind_conflict(sk, tb))
                        goto fail_unlock;
            }
      }
tb_not_found:
      ret = 1;
      if (!tb && (tb = inet_bind_bucket_create(hashinfo->bind_bucket_cachep, head, snum)) == NULL)
            goto fail_unlock;
      if (hlist_empty(&tb->owners)) {
            if (sk->sk_reuse && sk->sk_state != TCP_LISTEN)
                  tb->fastreuse = 1;
            else
                  tb->fastreuse = 0;
      } else if (tb->fastreuse &&
               (!sk->sk_reuse || sk->sk_state == TCP_LISTEN))
            tb->fastreuse = 0;
success:
      if (!inet_csk(sk)->icsk_bind_hash)
            inet_bind_hash(sk, tb, snum);
      BUG_TRAP(inet_csk(sk)->icsk_bind_hash == tb);
      ret = 0;

fail_unlock:
      spin_unlock(&head->lock);
fail:
      local_bh_enable();
      return ret;
}

EXPORT_SYMBOL_GPL(inet_csk_get_port);

/*
 * Wait for an incoming connection, avoid race conditions. This must be called
 * with the socket locked.
 */
static int inet_csk_wait_for_connect(struct sock *sk, long timeo)
{
      struct inet_connection_sock *icsk = inet_csk(sk);
      DEFINE_WAIT(wait);
      int err;

      /*
       * True wake-one mechanism for incoming connections: only
       * one process gets woken up, not the 'whole herd'.
       * Since we do not 'race & poll' for established sockets
       * anymore, the common case will execute the loop only once.
       *
       * Subtle issue: "add_wait_queue_exclusive()" will be added
       * after any current non-exclusive waiters, and we know that
       * it will always _stay_ after any new non-exclusive waiters
       * because all non-exclusive waiters are added at the
       * beginning of the wait-queue. As such, it's ok to "drop"
       * our exclusiveness temporarily when we get woken up without
       * having to remove and re-insert us on the wait queue.
       */
      for (;;) {
            prepare_to_wait_exclusive(sk->sk_sleep, &wait,
                                TASK_INTERRUPTIBLE);
            release_sock(sk);
            if (reqsk_queue_empty(&icsk->icsk_accept_queue))
                  timeo = schedule_timeout(timeo);
            lock_sock(sk);
            err = 0;
            if (!reqsk_queue_empty(&icsk->icsk_accept_queue))
                  break;
            err = -EINVAL;
            if (sk->sk_state != TCP_LISTEN)
                  break;
            err = sock_intr_errno(timeo);
            if (signal_pending(current))
                  break;
            err = -EAGAIN;
            if (!timeo)
                  break;
      }
      finish_wait(sk->sk_sleep, &wait);
      return err;
}

/*
 * This will accept the next outstanding connection.
 */
struct sock *inet_csk_accept(struct sock *sk, int flags, int *err)
{
      struct inet_connection_sock *icsk = inet_csk(sk);
      struct sock *newsk;
      int error;

      lock_sock(sk);

      /* We need to make sure that this socket is listening,
       * and that it has something pending.
       */
      error = -EINVAL;
      if (sk->sk_state != TCP_LISTEN)
            goto out_err;

      /* Find already established connection */
      if (reqsk_queue_empty(&icsk->icsk_accept_queue)) {
            long timeo = sock_rcvtimeo(sk, flags & O_NONBLOCK);

            /* If this is a non blocking socket don't sleep */
            error = -EAGAIN;
            if (!timeo)
                  goto out_err;

            error = inet_csk_wait_for_connect(sk, timeo);
            if (error)
                  goto out_err;
      }

      newsk = reqsk_queue_get_child(&icsk->icsk_accept_queue, sk);
      BUG_TRAP(newsk->sk_state != TCP_SYN_RECV);
out:
      release_sock(sk);
      return newsk;
out_err:
      newsk = NULL;
      *err = error;
      goto out;
}

EXPORT_SYMBOL(inet_csk_accept);

/*
 * Using different timers for retransmit, delayed acks and probes
 * We may wish use just one timer maintaining a list of expire jiffies
 * to optimize.
 */
void inet_csk_init_xmit_timers(struct sock *sk,
                         void (*retransmit_handler)(unsigned long),
                         void (*delack_handler)(unsigned long),
                         void (*keepalive_handler)(unsigned long))
{
      struct inet_connection_sock *icsk = inet_csk(sk);

      init_timer(&icsk->icsk_retransmit_timer);
      init_timer(&icsk->icsk_delack_timer);
      init_timer(&sk->sk_timer);

      icsk->icsk_retransmit_timer.function = retransmit_handler;
      icsk->icsk_delack_timer.function     = delack_handler;
      sk->sk_timer.function              = keepalive_handler;

      icsk->icsk_retransmit_timer.data =
            icsk->icsk_delack_timer.data =
                  sk->sk_timer.data  = (unsigned long)sk;

      icsk->icsk_pending = icsk->icsk_ack.pending = 0;
}

EXPORT_SYMBOL(inet_csk_init_xmit_timers);

void inet_csk_clear_xmit_timers(struct sock *sk)
{
      struct inet_connection_sock *icsk = inet_csk(sk);

      icsk->icsk_pending = icsk->icsk_ack.pending = icsk->icsk_ack.blocked = 0;

      sk_stop_timer(sk, &icsk->icsk_retransmit_timer);
      sk_stop_timer(sk, &icsk->icsk_delack_timer);
      sk_stop_timer(sk, &sk->sk_timer);
}

EXPORT_SYMBOL(inet_csk_clear_xmit_timers);

void inet_csk_delete_keepalive_timer(struct sock *sk)
{
      sk_stop_timer(sk, &sk->sk_timer);
}

EXPORT_SYMBOL(inet_csk_delete_keepalive_timer);

void inet_csk_reset_keepalive_timer(struct sock *sk, unsigned long len)
{
      sk_reset_timer(sk, &sk->sk_timer, jiffies + len);
}

EXPORT_SYMBOL(inet_csk_reset_keepalive_timer);

struct dst_entry* inet_csk_route_req(struct sock *sk,
                             const struct request_sock *req)
{
      struct rtable *rt;
      const struct inet_request_sock *ireq = inet_rsk(req);
      struct ip_options *opt = inet_rsk(req)->opt;
      struct flowi fl = { .oif = sk->sk_bound_dev_if,
                      .nl_u = { .ip4_u =
                              { .daddr = ((opt && opt->srr) ?
                                      opt->faddr :
                                      ireq->rmt_addr),
                              .saddr = ireq->loc_addr,
                              .tos = RT_CONN_FLAGS(sk) } },
                      .proto = sk->sk_protocol,
                      .uli_u = { .ports =
                               { .sport = inet_sk(sk)->sport,
                               .dport = ireq->rmt_port } } };

      security_req_classify_flow(req, &fl);
      if (ip_route_output_flow(&rt, &fl, sk, 0)) {
            IP_INC_STATS_BH(IPSTATS_MIB_OUTNOROUTES);
            return NULL;
      }
      if (opt && opt->is_strictroute && rt->rt_dst != rt->rt_gateway) {
            ip_rt_put(rt);
            IP_INC_STATS_BH(IPSTATS_MIB_OUTNOROUTES);
            return NULL;
      }
      return &rt->u.dst;
}

EXPORT_SYMBOL_GPL(inet_csk_route_req);

static inline u32 inet_synq_hash(const __be32 raddr, const __be16 rport,
                         const u32 rnd, const u32 synq_hsize)
{
      return jhash_2words((__force u32)raddr, (__force u32)rport, rnd) & (synq_hsize - 1);
}

#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
#define AF_INET_FAMILY(fam) ((fam) == AF_INET)
#else
#define AF_INET_FAMILY(fam) 1
#endif

struct request_sock *inet_csk_search_req(const struct sock *sk,
                               struct request_sock ***prevp,
                               const __be16 rport, const __be32 raddr,
                               const __be32 laddr)
{
      const struct inet_connection_sock *icsk = inet_csk(sk);
      struct listen_sock *lopt = icsk->icsk_accept_queue.listen_opt;
      struct request_sock *req, **prev;

      for (prev = &lopt->syn_table[inet_synq_hash(raddr, rport, lopt->hash_rnd,
                                        lopt->nr_table_entries)];
           (req = *prev) != NULL;
           prev = &req->dl_next) {
            const struct inet_request_sock *ireq = inet_rsk(req);

            if (ireq->rmt_port == rport &&
                ireq->rmt_addr == raddr &&
                ireq->loc_addr == laddr &&
                AF_INET_FAMILY(req->rsk_ops->family)) {
                  BUG_TRAP(!req->sk);
                  *prevp = prev;
                  break;
            }
      }

      return req;
}

EXPORT_SYMBOL_GPL(inet_csk_search_req);

void inet_csk_reqsk_queue_hash_add(struct sock *sk, struct request_sock *req,
                           unsigned long timeout)
{
      struct inet_connection_sock *icsk = inet_csk(sk);
      struct listen_sock *lopt = icsk->icsk_accept_queue.listen_opt;
      const u32 h = inet_synq_hash(inet_rsk(req)->rmt_addr, inet_rsk(req)->rmt_port,
                             lopt->hash_rnd, lopt->nr_table_entries);

      reqsk_queue_hash_req(&icsk->icsk_accept_queue, h, req, timeout);
      inet_csk_reqsk_queue_added(sk, timeout);
}

/* Only thing we need from tcp.h */
extern int sysctl_tcp_synack_retries;

EXPORT_SYMBOL_GPL(inet_csk_reqsk_queue_hash_add);

void inet_csk_reqsk_queue_prune(struct sock *parent,
                        const unsigned long interval,
                        const unsigned long timeout,
                        const unsigned long max_rto)
{
      struct inet_connection_sock *icsk = inet_csk(parent);
      struct request_sock_queue *queue = &icsk->icsk_accept_queue;
      struct listen_sock *lopt = queue->listen_opt;
      int max_retries = icsk->icsk_syn_retries ? : sysctl_tcp_synack_retries;
      int thresh = max_retries;
      unsigned long now = jiffies;
      struct request_sock **reqp, *req;
      int i, budget;

      if (lopt == NULL || lopt->qlen == 0)
            return;

      /* Normally all the openreqs are young and become mature
       * (i.e. converted to established socket) for first timeout.
       * If synack was not acknowledged for 3 seconds, it means
       * one of the following things: synack was lost, ack was lost,
       * rtt is high or nobody planned to ack (i.e. synflood).
       * When server is a bit loaded, queue is populated with old
       * open requests, reducing effective size of queue.
       * When server is well loaded, queue size reduces to zero
       * after several minutes of work. It is not synflood,
       * it is normal operation. The solution is pruning
       * too old entries overriding normal timeout, when
       * situation becomes dangerous.
       *
       * Essentially, we reserve half of room for young
       * embrions; and abort old ones without pity, if old
       * ones are about to clog our table.
       */
      if (lopt->qlen>>(lopt->max_qlen_log-1)) {
            int young = (lopt->qlen_young<<1);

            while (thresh > 2) {
                  if (lopt->qlen < young)
                        break;
                  thresh--;
                  young <<= 1;
            }
      }

      if (queue->rskq_defer_accept)
            max_retries = queue->rskq_defer_accept;

      budget = 2 * (lopt->nr_table_entries / (timeout / interval));
      i = lopt->clock_hand;

      do {
            reqp=&lopt->syn_table[i];
            while ((req = *reqp) != NULL) {
                  if (time_after_eq(now, req->expires)) {
                        if ((req->retrans < thresh ||
                             (inet_rsk(req)->acked && req->retrans < max_retries))
                            && !req->rsk_ops->rtx_syn_ack(parent, req, NULL)) {
                              unsigned long timeo;

                              if (req->retrans++ == 0)
                                    lopt->qlen_young--;
                              timeo = min((timeout << req->retrans), max_rto);
                              req->expires = now + timeo;
                              reqp = &req->dl_next;
                              continue;
                        }

                        /* Drop this request */
                        inet_csk_reqsk_queue_unlink(parent, req, reqp);
                        reqsk_queue_removed(queue, req);
                        reqsk_free(req);
                        continue;
                  }
                  reqp = &req->dl_next;
            }

            i = (i + 1) & (lopt->nr_table_entries - 1);

      } while (--budget > 0);

      lopt->clock_hand = i;

      if (lopt->qlen)
            inet_csk_reset_keepalive_timer(parent, interval);
}

EXPORT_SYMBOL_GPL(inet_csk_reqsk_queue_prune);

struct sock *inet_csk_clone(struct sock *sk, const struct request_sock *req,
                      const gfp_t priority)
{
      struct sock *newsk = sk_clone(sk, priority);

      if (newsk != NULL) {
            struct inet_connection_sock *newicsk = inet_csk(newsk);

            newsk->sk_state = TCP_SYN_RECV;
            newicsk->icsk_bind_hash = NULL;

            inet_sk(newsk)->dport = inet_rsk(req)->rmt_port;
            newsk->sk_write_space = sk_stream_write_space;

            newicsk->icsk_retransmits = 0;
            newicsk->icsk_backoff     = 0;
            newicsk->icsk_probes_out  = 0;

            /* Deinitialize accept_queue to trap illegal accesses. */
            memset(&newicsk->icsk_accept_queue, 0, sizeof(newicsk->icsk_accept_queue));

            security_inet_csk_clone(newsk, req);
      }
      return newsk;
}

EXPORT_SYMBOL_GPL(inet_csk_clone);

/*
 * At this point, there should be no process reference to this
 * socket, and thus no user references at all.  Therefore we
 * can assume the socket waitqueue is inactive and nobody will
 * try to jump onto it.
 */
void inet_csk_destroy_sock(struct sock *sk)
{
      BUG_TRAP(sk->sk_state == TCP_CLOSE);
      BUG_TRAP(sock_flag(sk, SOCK_DEAD));

      /* It cannot be in hash table! */
      BUG_TRAP(sk_unhashed(sk));

      /* If it has not 0 inet_sk(sk)->num, it must be bound */
      BUG_TRAP(!inet_sk(sk)->num || inet_csk(sk)->icsk_bind_hash);

      sk->sk_prot->destroy(sk);

      sk_stream_kill_queues(sk);

      xfrm_sk_free_policy(sk);

      sk_refcnt_debug_release(sk);

      atomic_dec(sk->sk_prot->orphan_count);
      sock_put(sk);
}

EXPORT_SYMBOL(inet_csk_destroy_sock);

int inet_csk_listen_start(struct sock *sk, const int nr_table_entries)
{
      struct inet_sock *inet = inet_sk(sk);
      struct inet_connection_sock *icsk = inet_csk(sk);
      int rc = reqsk_queue_alloc(&icsk->icsk_accept_queue, nr_table_entries);

      if (rc != 0)
            return rc;

      sk->sk_max_ack_backlog = 0;
      sk->sk_ack_backlog = 0;
      inet_csk_delack_init(sk);

      /* There is race window here: we announce ourselves listening,
       * but this transition is still not validated by get_port().
       * It is OK, because this socket enters to hash table only
       * after validation is complete.
       */
      sk->sk_state = TCP_LISTEN;
      if (!sk->sk_prot->get_port(sk, inet->num)) {
            inet->sport = htons(inet->num);

            sk_dst_reset(sk);
            sk->sk_prot->hash(sk);

            return 0;
      }

      sk->sk_state = TCP_CLOSE;
      __reqsk_queue_destroy(&icsk->icsk_accept_queue);
      return -EADDRINUSE;
}

EXPORT_SYMBOL_GPL(inet_csk_listen_start);

/*
 *    This routine closes sockets which have been at least partially
 *    opened, but not yet accepted.
 */
void inet_csk_listen_stop(struct sock *sk)
{
      struct inet_connection_sock *icsk = inet_csk(sk);
      struct request_sock *acc_req;
      struct request_sock *req;

      inet_csk_delete_keepalive_timer(sk);

      /* make all the listen_opt local to us */
      acc_req = reqsk_queue_yank_acceptq(&icsk->icsk_accept_queue);

      /* Following specs, it would be better either to send FIN
       * (and enter FIN-WAIT-1, it is normal close)
       * or to send active reset (abort).
       * Certainly, it is pretty dangerous while synflood, but it is
       * bad justification for our negligence 8)
       * To be honest, we are not able to make either
       * of the variants now.             --ANK
       */
      reqsk_queue_destroy(&icsk->icsk_accept_queue);

      while ((req = acc_req) != NULL) {
            struct sock *child = req->sk;

            acc_req = req->dl_next;

            local_bh_disable();
            bh_lock_sock(child);
            BUG_TRAP(!sock_owned_by_user(child));
            sock_hold(child);

            sk->sk_prot->disconnect(child, O_NONBLOCK);

            sock_orphan(child);

            atomic_inc(sk->sk_prot->orphan_count);

            inet_csk_destroy_sock(child);

            bh_unlock_sock(child);
            local_bh_enable();
            sock_put(child);

            sk_acceptq_removed(sk);
            __reqsk_free(req);
      }
      BUG_TRAP(!sk->sk_ack_backlog);
}

EXPORT_SYMBOL_GPL(inet_csk_listen_stop);

void inet_csk_addr2sockaddr(struct sock *sk, struct sockaddr *uaddr)
{
      struct sockaddr_in *sin = (struct sockaddr_in *)uaddr;
      const struct inet_sock *inet = inet_sk(sk);

      sin->sin_family         = AF_INET;
      sin->sin_addr.s_addr    = inet->daddr;
      sin->sin_port           = inet->dport;
}

EXPORT_SYMBOL_GPL(inet_csk_addr2sockaddr);

int inet_csk_ctl_sock_create(struct socket **sock, unsigned short family,
                       unsigned short type, unsigned char protocol)
{
      int rc = sock_create_kern(family, type, protocol, sock);

      if (rc == 0) {
            (*sock)->sk->sk_allocation = GFP_ATOMIC;
            inet_sk((*sock)->sk)->uc_ttl = -1;
            /*
             * Unhash it so that IP input processing does not even see it,
             * we do not wish this socket to see incoming packets.
             */
            (*sock)->sk->sk_prot->unhash((*sock)->sk);
      }
      return rc;
}

EXPORT_SYMBOL_GPL(inet_csk_ctl_sock_create);

#ifdef CONFIG_COMPAT
int inet_csk_compat_getsockopt(struct sock *sk, int level, int optname,
                         char __user *optval, int __user *optlen)
{
      const struct inet_connection_sock *icsk = inet_csk(sk);

      if (icsk->icsk_af_ops->compat_getsockopt != NULL)
            return icsk->icsk_af_ops->compat_getsockopt(sk, level, optname,
                                              optval, optlen);
      return icsk->icsk_af_ops->getsockopt(sk, level, optname,
                                   optval, optlen);
}

EXPORT_SYMBOL_GPL(inet_csk_compat_getsockopt);

int inet_csk_compat_setsockopt(struct sock *sk, int level, int optname,
                         char __user *optval, int optlen)
{
      const struct inet_connection_sock *icsk = inet_csk(sk);

      if (icsk->icsk_af_ops->compat_setsockopt != NULL)
            return icsk->icsk_af_ops->compat_setsockopt(sk, level, optname,
                                              optval, optlen);
      return icsk->icsk_af_ops->setsockopt(sk, level, optname,
                                   optval, optlen);
}

EXPORT_SYMBOL_GPL(inet_csk_compat_setsockopt);
#endif

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