socket.c

/* SCTP kernel implementation
 * (C) Copyright IBM Corp. 2001, 2004
 * Copyright (c) 1999-2000 Cisco, Inc.
 * Copyright (c) 1999-2001 Motorola, Inc.
 * Copyright (c) 2001-2003 Intel Corp.
 * Copyright (c) 2001-2002 Nokia, Inc.
 * Copyright (c) 2001 La Monte H.P. Yarroll
 *
 * This file is part of the SCTP kernel implementation
 *
 * These functions interface with the sockets layer to implement the
 * SCTP Extensions for the Sockets API.
 *
 * Note that the descriptions from the specification are USER level
 * functions--this file is the functions which populate the struct proto
 * for SCTP which is the BOTTOM of the sockets interface.
 *
 * This SCTP implementation 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, or (at your option)
 * any later version.
 *
 * This SCTP implementation 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with GNU CC; see the file COPYING.  If not, see
 * <http://www.gnu.org/licenses/>.
 *
 * Please send any bug reports or fixes you make to the
 * email address(es):
 *    lksctp developers <linux-sctp@vger.kernel.org>
 *
 * Written or modified by:
 *    La Monte H.P. Yarroll <piggy@acm.org>
 *    Narasimha Budihal     <narsi@refcode.org>
 *    Karl Knutson          <karl@athena.chicago.il.us>
 *    Jon Grimm             <jgrimm@us.ibm.com>
 *    Xingang Guo           <xingang.guo@intel.com>
 *    Daisy Chang           <daisyc@us.ibm.com>
 *    Sridhar Samudrala     <samudrala@us.ibm.com>
 *    Inaky Perez-Gonzalez  <inaky.gonzalez@intel.com>
 *    Ardelle Fan	    <ardelle.fan@intel.com>
 *    Ryan Layer	    <rmlayer@us.ibm.com>
 *    Anup Pemmaiah         <pemmaiah@cc.usu.edu>
 *    Kevin Gao             <kevin.gao@intel.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <crypto/hash.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/wait.h>
#include <linux/time.h>
#include <linux/ip.h>
#include <linux/capability.h>
#include <linux/fcntl.h>
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/compat.h>

#include <net/ip.h>
#include <net/icmp.h>
#include <net/route.h>
#include <net/ipv6.h>
#include <net/inet_common.h>
#include <net/busy_poll.h>

#include <linux/socket.h> /* for sa_family_t */
#include <linux/export.h>
#include <net/sock.h>
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>

/* Forward declarations for internal helper functions. */
static int sctp_writeable(struct sock *sk);
static void sctp_wfree(struct sk_buff *skb);
static int sctp_wait_for_sndbuf(struct sctp_association *, long *timeo_p,
				size_t msg_len);
static int sctp_wait_for_packet(struct sock *sk, int *err, long *timeo_p);
static int sctp_wait_for_connect(struct sctp_association *, long *timeo_p);
static int sctp_wait_for_accept(struct sock *sk, long timeo);
static void sctp_wait_for_close(struct sock *sk, long timeo);
static void sctp_destruct_sock(struct sock *sk);
static struct sctp_af *sctp_sockaddr_af(struct sctp_sock *opt,
					union sctp_addr *addr, int len);
static int sctp_bindx_add(struct sock *, struct sockaddr *, int);
static int sctp_bindx_rem(struct sock *, struct sockaddr *, int);
static int sctp_send_asconf_add_ip(struct sock *, struct sockaddr *, int);
static int sctp_send_asconf_del_ip(struct sock *, struct sockaddr *, int);
static int sctp_send_asconf(struct sctp_association *asoc,
			    struct sctp_chunk *chunk);
static int sctp_do_bind(struct sock *, union sctp_addr *, int);
static int sctp_autobind(struct sock *sk);
static void sctp_sock_migrate(struct sock *, struct sock *,
			      struct sctp_association *, sctp_socket_type_t);

static int sctp_memory_pressure;
static atomic_long_t sctp_memory_allocated;
struct percpu_counter sctp_sockets_allocated;

static void sctp_enter_memory_pressure(struct sock *sk)
{
	sctp_memory_pressure = 1;
}


/* Get the sndbuf space available at the time on the association.  */
static inline int sctp_wspace(struct sctp_association *asoc)
{
	int amt;

	if (asoc->ep->sndbuf_policy)
		amt = asoc->sndbuf_used;
	else
		amt = sk_wmem_alloc_get(asoc->base.sk);

	if (amt >= asoc->base.sk->sk_sndbuf) {
		if (asoc->base.sk->sk_userlocks & SOCK_SNDBUF_LOCK)
			amt = 0;
		else {
			amt = sk_stream_wspace(asoc->base.sk);
			if (amt < 0)
				amt = 0;
		}
	} else {
		amt = asoc->base.sk->sk_sndbuf - amt;
	}
	return amt;
}

/* Increment the used sndbuf space count of the corresponding association by
 * the size of the outgoing data chunk.
 * Also, set the skb destructor for sndbuf accounting later.
 *
 * Since it is always 1-1 between chunk and skb, and also a new skb is always
 * allocated for chunk bundling in sctp_packet_transmit(), we can use the
 * destructor in the data chunk skb for the purpose of the sndbuf space
 * tracking.
 */
static inline void sctp_set_owner_w(struct sctp_chunk *chunk)
{
	struct sctp_association *asoc = chunk->asoc;
	struct sock *sk = asoc->base.sk;

	/* The sndbuf space is tracked per association.  */
	sctp_association_hold(asoc);

	skb_set_owner_w(chunk->skb, sk);

	chunk->skb->destructor = sctp_wfree;
	/* Save the chunk pointer in skb for sctp_wfree to use later.  */
	skb_shinfo(chunk->skb)->destructor_arg = chunk;

	asoc->sndbuf_used += SCTP_DATA_SNDSIZE(chunk) +
				sizeof(struct sk_buff) +
				sizeof(struct sctp_chunk);

	atomic_add(sizeof(struct sctp_chunk), &sk->sk_wmem_alloc);
	sk->sk_wmem_queued += chunk->skb->truesize;
	sk_mem_charge(sk, chunk->skb->truesize);
}

/* Verify that this is a valid address. */
static inline int sctp_verify_addr(struct sock *sk, union sctp_addr *addr,
				   int len)
{
	struct sctp_af *af;

	/* Verify basic sockaddr. */
	af = sctp_sockaddr_af(sctp_sk(sk), addr, len);
	if (!af)
		return -EINVAL;

	/* Is this a valid SCTP address?  */
	if (!af->addr_valid(addr, sctp_sk(sk), NULL))
		return -EINVAL;

	if (!sctp_sk(sk)->pf->send_verify(sctp_sk(sk), (addr)))
		return -EINVAL;

	return 0;
}

/* Look up the association by its id.  If this is not a UDP-style
 * socket, the ID field is always ignored.
 */
struct sctp_association *sctp_id2assoc(struct sock *sk, sctp_assoc_t id)
{
	struct sctp_association *asoc = NULL;

	/* If this is not a UDP-style socket, assoc id should be ignored. */
	if (!sctp_style(sk, UDP)) {
		/* Return NULL if the socket state is not ESTABLISHED. It
		 * could be a TCP-style listening socket or a socket which
		 * hasn't yet called connect() to establish an association.
		 */
		if (!sctp_sstate(sk, ESTABLISHED) && !sctp_sstate(sk, CLOSING))
			return NULL;

		/* Get the first and the only association from the list. */
		if (!list_empty(&sctp_sk(sk)->ep->asocs))
			asoc = list_entry(sctp_sk(sk)->ep->asocs.next,
					  struct sctp_association, asocs);
		return asoc;
	}

	/* Otherwise this is a UDP-style socket. */
	if (!id || (id == (sctp_assoc_t)-1))
		return NULL;

	spin_lock_bh(&sctp_assocs_id_lock);
	asoc = (struct sctp_association *)idr_find(&sctp_assocs_id, (int)id);
	spin_unlock_bh(&sctp_assocs_id_lock);

	if (!asoc || (asoc->base.sk != sk) || asoc->base.dead)
		return NULL;

	return asoc;
}

/* Look up the transport from an address and an assoc id. If both address and
 * id are specified, the associations matching the address and the id should be
 * the same.
 */
static struct sctp_transport *sctp_addr_id2transport(struct sock *sk,
					      struct sockaddr_storage *addr,
					      sctp_assoc_t id)
{
	struct sctp_association *addr_asoc = NULL, *id_asoc = NULL;
	struct sctp_transport *transport;
	union sctp_addr *laddr = (union sctp_addr *)addr;

	addr_asoc = sctp_endpoint_lookup_assoc(sctp_sk(sk)->ep,
					       laddr,
					       &transport);

	if (!addr_asoc)
		return NULL;

	id_asoc = sctp_id2assoc(sk, id);
	if (id_asoc && (id_asoc != addr_asoc))
		return NULL;

	sctp_get_pf_specific(sk->sk_family)->addr_to_user(sctp_sk(sk),
						(union sctp_addr *)addr);

	return transport;
}

/* API 3.1.2 bind() - UDP Style Syntax
 * The syntax of bind() is,
 *
 *   ret = bind(int sd, struct sockaddr *addr, int addrlen);
 *
 *   sd      - the socket descriptor returned by socket().
 *   addr    - the address structure (struct sockaddr_in or struct
 *             sockaddr_in6 [RFC 2553]),
 *   addr_len - the size of the address structure.
 */
static int sctp_bind(struct sock *sk, struct sockaddr *addr, int addr_len)
{
	int retval = 0;

	lock_sock(sk);

	pr_debug("%s: sk:%p, addr:%p, addr_len:%d\n", __func__, sk,
		 addr, addr_len);

	/* Disallow binding twice. */
	if (!sctp_sk(sk)->ep->base.bind_addr.port)
		retval = sctp_do_bind(sk, (union sctp_addr *)addr,
				      addr_len);
	else
		retval = -EINVAL;

	release_sock(sk);

	return retval;
}

static long sctp_get_port_local(struct sock *, union sctp_addr *);

/* Verify this is a valid sockaddr. */
static struct sctp_af *sctp_sockaddr_af(struct sctp_sock *opt,
					union sctp_addr *addr, int len)
{
	struct sctp_af *af;

	/* Check minimum size.  */
	if (len < sizeof (struct sockaddr))
		return NULL;

	/* V4 mapped address are really of AF_INET family */
	if (addr->sa.sa_family == AF_INET6 &&
	    ipv6_addr_v4mapped(&addr->v6.sin6_addr)) {
		if (!opt->pf->af_supported(AF_INET, opt))
			return NULL;
	} else {
		/* Does this PF support this AF? */
		if (!opt->pf->af_supported(addr->sa.sa_family, opt))
			return NULL;
	}

	/* If we get this far, af is valid. */
	af = sctp_get_af_specific(addr->sa.sa_family);

	if (len < af->sockaddr_len)
		return NULL;

	return af;
}

/* Bind a local address either to an endpoint or to an association.  */
static int sctp_do_bind(struct sock *sk, union sctp_addr *addr, int len)
{
	struct net *net = sock_net(sk);
	struct sctp_sock *sp = sctp_sk(sk);
	struct sctp_endpoint *ep = sp->ep;
	struct sctp_bind_addr *bp = &ep->base.bind_addr;
	struct sctp_af *af;
	unsigned short snum;
	int ret = 0;

	/* Common sockaddr verification. */
	af = sctp_sockaddr_af(sp, addr, len);
	if (!af) {
		pr_debug("%s: sk:%p, newaddr:%p, len:%d EINVAL\n",
			 __func__, sk, addr, len);
		return -EINVAL;
	}

	snum = ntohs(addr->v4.sin_port);

	pr_debug("%s: sk:%p, new addr:%pISc, port:%d, new port:%d, len:%d\n",
		 __func__, sk, &addr->sa, bp->port, snum, len);

	/* PF specific bind() address verification. */
	if (!sp->pf->bind_verify(sp, addr))
		return -EADDRNOTAVAIL;

	/* We must either be unbound, or bind to the same port.
	 * It's OK to allow 0 ports if we are already bound.
	 * We'll just inhert an already bound port in this case
	 */
	if (bp->port) {
		if (!snum)
			snum = bp->port;
		else if (snum != bp->port) {
			pr_debug("%s: new port %d doesn't match existing port "
				 "%d\n", __func__, snum, bp->port);
			return -EINVAL;
		}
	}

	if (snum && snum < PROT_SOCK &&
	    !ns_capable(net->user_ns, CAP_NET_BIND_SERVICE))
		return -EACCES;

	/* See if the address matches any of the addresses we may have
	 * already bound before checking against other endpoints.
	 */
	if (sctp_bind_addr_match(bp, addr, sp))
		return -EINVAL;

	/* Make sure we are allowed to bind here.
	 * The function sctp_get_port_local() does duplicate address
	 * detection.
	 */
	addr->v4.sin_port = htons(snum);
	if ((ret = sctp_get_port_local(sk, addr))) {
		return -EADDRINUSE;
	}

	/* Refresh ephemeral port.  */
	if (!bp->port)
		bp->port = inet_sk(sk)->inet_num;

	/* Add the address to the bind address list.
	 * Use GFP_ATOMIC since BHs will be disabled.
	 */
	ret = sctp_add_bind_addr(bp, addr, af->sockaddr_len,
				 SCTP_ADDR_SRC, GFP_ATOMIC);

	/* Copy back into socket for getsockname() use. */
	if (!ret) {
		inet_sk(sk)->inet_sport = htons(inet_sk(sk)->inet_num);
		sp->pf->to_sk_saddr(addr, sk);
	}

	return ret;
}

 /* ADDIP Section 4.1.1 Congestion Control of ASCONF Chunks
 *
 * R1) One and only one ASCONF Chunk MAY be in transit and unacknowledged
 * at any one time.  If a sender, after sending an ASCONF chunk, decides
 * it needs to transfer another ASCONF Chunk, it MUST wait until the
 * ASCONF-ACK Chunk returns from the previous ASCONF Chunk before sending a
 * subsequent ASCONF. Note this restriction binds each side, so at any
 * time two ASCONF may be in-transit on any given association (one sent
 * from each endpoint).
 */
static int sctp_send_asconf(struct sctp_association *asoc,
			    struct sctp_chunk *chunk)
{
	struct net 	*net = sock_net(asoc->base.sk);
	int		retval = 0;

	/* If there is an outstanding ASCONF chunk, queue it for later
	 * transmission.
	 */
	if (asoc->addip_last_asconf) {
		list_add_tail(&chunk->list, &asoc->addip_chunk_list);
		goto out;
	}

	/* Hold the chunk until an ASCONF_ACK is received. */
	sctp_chunk_hold(chunk);
	retval = sctp_primitive_ASCONF(net, asoc, chunk);
	if (retval)
		sctp_chunk_free(chunk);
	else
		asoc->addip_last_asconf = chunk;

out:
	return retval;
}

/* Add a list of addresses as bind addresses to local endpoint or
 * association.
 *
 * Basically run through each address specified in the addrs/addrcnt
 * array/length pair, determine if it is IPv6 or IPv4 and call
 * sctp_do_bind() on it.
 *
 * If any of them fails, then the operation will be reversed and the
 * ones that were added will be removed.
 *
 * Only sctp_setsockopt_bindx() is supposed to call this function.
 */
static int sctp_bindx_add(struct sock *sk, struct sockaddr *addrs, int addrcnt)
{
	int cnt;
	int retval = 0;
	void *addr_buf;
	struct sockaddr *sa_addr;
	struct sctp_af *af;

	pr_debug("%s: sk:%p, addrs:%p, addrcnt:%d\n", __func__, sk,
		 addrs, addrcnt);

	addr_buf = addrs;
	for (cnt = 0; cnt < addrcnt; cnt++) {
		/* The list may contain either IPv4 or IPv6 address;
		 * determine the address length for walking thru the list.
		 */
		sa_addr = addr_buf;
		af = sctp_get_af_specific(sa_addr->sa_family);
		if (!af) {
			retval = -EINVAL;
			goto err_bindx_add;
		}

		retval = sctp_do_bind(sk, (union sctp_addr *)sa_addr,
				      af->sockaddr_len);

		addr_buf += af->sockaddr_len;

err_bindx_add:
		if (retval < 0) {
			/* Failed. Cleanup the ones that have been added */
			if (cnt > 0)
				sctp_bindx_rem(sk, addrs, cnt);
			return retval;
		}
	}

	return retval;
}

/* Send an ASCONF chunk with Add IP address parameters to all the peers of the
 * associations that are part of the endpoint indicating that a list of local
 * addresses are added to the endpoint.
 *
 * If any of the addresses is already in the bind address list of the
 * association, we do not send the chunk for that association.  But it will not
 * affect other associations.
 *
 * Only sctp_setsockopt_bindx() is supposed to call this function.
 */
static int sctp_send_asconf_add_ip(struct sock		*sk,
				   struct sockaddr	*addrs,
				   int 			addrcnt)
{
	struct net *net = sock_net(sk);
	struct sctp_sock		*sp;
	struct sctp_endpoint		*ep;
	struct sctp_association		*asoc;
	struct sctp_bind_addr		*bp;
	struct sctp_chunk		*chunk;
	struct sctp_sockaddr_entry	*laddr;
	union sctp_addr			*addr;
	union sctp_addr			saveaddr;
	void				*addr_buf;
	struct sctp_af			*af;
	struct list_head		*p;
	int 				i;
	int 				retval = 0;

	if (!net->sctp.addip_enable)
		return retval;

	sp = sctp_sk(sk);
	ep = sp->ep;

	pr_debug("%s: sk:%p, addrs:%p, addrcnt:%d\n",
		 __func__, sk, addrs, addrcnt);

	list_for_each_entry(asoc, &ep->asocs, asocs) {
		if (!asoc->peer.asconf_capable)
			continue;

		if (asoc->peer.addip_disabled_mask & SCTP_PARAM_ADD_IP)
			continue;

		if (!sctp_state(asoc, ESTABLISHED))
			continue;

		/* Check if any address in the packed array of addresses is
		 * in the bind address list of the association. If so,
		 * do not send the asconf chunk to its peer, but continue with
		 * other associations.
		 */
		addr_buf = addrs;
		for (i = 0; i < addrcnt; i++) {
			addr = addr_buf;
			af = sctp_get_af_specific(addr->v4.sin_family);
			if (!af) {
				retval = -EINVAL;
				goto out;
			}

			if (sctp_assoc_lookup_laddr(asoc, addr))
				break;

			addr_buf += af->sockaddr_len;
		}
		if (i < addrcnt)
			continue;

		/* Use the first valid address in bind addr list of
		 * association as Address Parameter of ASCONF CHUNK.
		 */
		bp = &asoc->base.bind_addr;
		p = bp->address_list.next;
		laddr = list_entry(p, struct sctp_sockaddr_entry, list);
		chunk = sctp_make_asconf_update_ip(asoc, &laddr->a, addrs,
						   addrcnt, SCTP_PARAM_ADD_IP);
		if (!chunk) {
			retval = -ENOMEM;
			goto out;
		}

		/* Add the new addresses to the bind address list with
		 * use_as_src set to 0.
		 */
		addr_buf = addrs;
		for (i = 0; i < addrcnt; i++) {
			addr = addr_buf;
			af = sctp_get_af_specific(addr->v4.sin_family);
			memcpy(&saveaddr, addr, af->sockaddr_len);
			retval = sctp_add_bind_addr(bp, &saveaddr,
						    sizeof(saveaddr),
						    SCTP_ADDR_NEW, GFP_ATOMIC);
			addr_buf += af->sockaddr_len;
		}
		if (asoc->src_out_of_asoc_ok) {
			struct sctp_transport *trans;

			list_for_each_entry(trans,
			    &asoc->peer.transport_addr_list, transports) {
				/* Clear the source and route cache */
				dst_release(trans->dst);
				trans->cwnd = min(4*asoc->pathmtu, max_t(__u32,
				    2*asoc->pathmtu, 4380));
				trans->ssthresh = asoc->peer.i.a_rwnd;
				trans->rto = asoc->rto_initial;
				sctp_max_rto(asoc, trans);
				trans->rtt = trans->srtt = trans->rttvar = 0;
				sctp_transport_route(trans, NULL,
				    sctp_sk(asoc->base.sk));
			}
		}
		retval = sctp_send_asconf(asoc, chunk);
	}

out:
	return retval;
}

/* Remove a list of addresses from bind addresses list.  Do not remove the
 * last address.
 *
 * Basically run through each address specified in the addrs/addrcnt
 * array/length pair, determine if it is IPv6 or IPv4 and call
 * sctp_del_bind() on it.
 *
 * If any of them fails, then the operation will be reversed and the
 * ones that were removed will be added back.
 *
 * At least one address has to be left; if only one address is
 * available, the operation will return -EBUSY.
 *
 * Only sctp_setsockopt_bindx() is supposed to call this function.
 */
static int sctp_bindx_rem(struct sock *sk, struct sockaddr *addrs, int addrcnt)
{
	struct sctp_sock *sp = sctp_sk(sk);
	struct sctp_endpoint *ep = sp->ep;
	int cnt;
	struct sctp_bind_addr *bp = &ep->base.bind_addr;
	int retval = 0;
	void *addr_buf;
	union sctp_addr *sa_addr;
	struct sctp_af *af;

	pr_debug("%s: sk:%p, addrs:%p, addrcnt:%d\n",
		 __func__, sk, addrs, addrcnt);

	addr_buf = addrs;
	for (cnt = 0; cnt < addrcnt; cnt++) {
		/* If the bind address list is empty or if there is only one
		 * bind address, there is nothing more to be removed (we need
		 * at least one address here).
		 */
		if (list_empty(&bp->address_list) ||
		    (sctp_list_single_entry(&bp->address_list))) {
			retval = -EBUSY;
			goto err_bindx_rem;
		}

		sa_addr = addr_buf;
		af = sctp_get_af_specific(sa_addr->sa.sa_family);
		if (!af) {
			retval = -EINVAL;
			goto err_bindx_rem;
		}

		if (!af->addr_valid(sa_addr, sp, NULL)) {
			retval = -EADDRNOTAVAIL;
			goto err_bindx_rem;
		}

		if (sa_addr->v4.sin_port &&
		    sa_addr->v4.sin_port != htons(bp->port)) {
			retval = -EINVAL;
			goto err_bindx_rem;
		}

		if (!sa_addr->v4.sin_port)
			sa_addr->v4.sin_port = htons(bp->port);

		/* FIXME - There is probably a need to check if sk->sk_saddr and
		 * sk->sk_rcv_addr are currently set to one of the addresses to
		 * be removed. This is something which needs to be looked into
		 * when we are fixing the outstanding issues with multi-homing
		 * socket routing and failover schemes. Refer to comments in
		 * sctp_do_bind(). -daisy
		 */
		retval = sctp_del_bind_addr(bp, sa_addr);

		addr_buf += af->sockaddr_len;
err_bindx_rem:
		if (retval < 0) {
			/* Failed. Add the ones that has been removed back */
			if (cnt > 0)
				sctp_bindx_add(sk, addrs, cnt);
			return retval;
		}
	}

	return retval;
}

/* Send an ASCONF chunk with Delete IP address parameters to all the peers of
 * the associations that are part of the endpoint indicating that a list of
 * local addresses are removed from the endpoint.
 *
 * If any of the addresses is already in the bind address list of the
 * association, we do not send the chunk for that association.  But it will not
 * affect other associations.
 *
 * Only sctp_setsockopt_bindx() is supposed to call this function.
 */
static int sctp_send_asconf_del_ip(struct sock		*sk,
				   struct sockaddr	*addrs,
				   int			addrcnt)
{
	struct net *net = sock_net(sk);
	struct sctp_sock	*sp;
	struct sctp_endpoint	*ep;
	struct sctp_association	*asoc;
	struct sctp_transport	*transport;
	struct sctp_bind_addr	*bp;
	struct sctp_chunk	*chunk;
	union sctp_addr		*laddr;
	void			*addr_buf;
	struct sctp_af		*af;
	struct sctp_sockaddr_entry *saddr;
	int 			i;
	int 			retval = 0;
	int			stored = 0;

	chunk = NULL;
	if (!net->sctp.addip_enable)
		return retval;

	sp = sctp_sk(sk);
	ep = sp->ep;

	pr_debug("%s: sk:%p, addrs:%p, addrcnt:%d\n",
		 __func__, sk, addrs, addrcnt);

	list_for_each_entry(asoc, &ep->asocs, asocs) {

		if (!asoc->peer.asconf_capable)
			continue;

		if (asoc->peer.addip_disabled_mask & SCTP_PARAM_DEL_IP)
			continue;

		if (!sctp_state(asoc, ESTABLISHED))
			continue;

		/* Check if any address in the packed array of addresses is
		 * not present in the bind address list of the association.
		 * If so, do not send the asconf chunk to its peer, but
		 * continue with other associations.
		 */
		addr_buf = addrs;
		for (i = 0; i < addrcnt; i++) {
			laddr = addr_buf;
			af = sctp_get_af_specific(laddr->v4.sin_family);
			if (!af) {
				retval = -EINVAL;
				goto out;
			}

			if (!sctp_assoc_lookup_laddr(asoc, laddr))
				break;

			addr_buf += af->sockaddr_len;
		}
		if (i < addrcnt)
			continue;

		/* Find one address in the association's bind address list
		 * that is not in the packed array of addresses. This is to
		 * make sure that we do not delete all the addresses in the
		 * association.
		 */
		bp = &asoc->base.bind_addr;
		laddr = sctp_find_unmatch_addr(bp, (union sctp_addr *)addrs,
					       addrcnt, sp);
		if ((laddr == NULL) && (addrcnt == 1)) {
			if (asoc->asconf_addr_del_pending)
				continue;
			asoc->asconf_addr_del_pending =
			    kzalloc(sizeof(union sctp_addr), GFP_ATOMIC);
			if (asoc->asconf_addr_del_pending == NULL) {
				retval = -ENOMEM;
				goto out;
			}
			asoc->asconf_addr_del_pending->sa.sa_family =
				    addrs->sa_family;
			asoc->asconf_addr_del_pending->v4.sin_port =
				    htons(bp->port);
			if (addrs->sa_family == AF_INET) {
				struct sockaddr_in *sin;

				sin = (struct sockaddr_in *)addrs;
				asoc->asconf_addr_del_pending->v4.sin_addr.s_addr = sin->sin_addr.s_addr;
			} else if (addrs->sa_family == AF_INET6) {
				struct sockaddr_in6 *sin6;

				sin6 = (struct sockaddr_in6 *)addrs;
				asoc->asconf_addr_del_pending->v6.sin6_addr = sin6->sin6_addr;
			}

			pr_debug("%s: keep the last address asoc:%p %pISc at %p\n",
				 __func__, asoc, &asoc->asconf_addr_del_pending->sa,
				 asoc->asconf_addr_del_pending);

			asoc->src_out_of_asoc_ok = 1;
			stored = 1;
			goto skip_mkasconf;
		}

		if (laddr == NULL)
			return -EINVAL;

		/* We do not need RCU protection throughout this loop
		 * because this is done under a socket lock from the
		 * setsockopt call.
		 */
		chunk = sctp_make_asconf_update_ip(asoc, laddr, addrs, addrcnt,
						   SCTP_PARAM_DEL_IP);
		if (!chunk) {
			retval = -ENOMEM;
			goto out;
		}

skip_mkasconf:
		/* Reset use_as_src flag for the addresses in the bind address
		 * list that are to be deleted.
		 */
		addr_buf = addrs;
		for (i = 0; i < addrcnt; i++) {
			laddr = addr_buf;
			af = sctp_get_af_specific(laddr->v4.sin_family);
			list_for_each_entry(saddr, &bp->address_list, list) {
				if (sctp_cmp_addr_exact(&saddr->a, laddr))
					saddr->state = SCTP_ADDR_DEL;
			}
			addr_buf += af->sockaddr_len;
		}

		/* Update the route and saddr entries for all the transports
		 * as some of the addresses in the bind address list are
		 * about to be deleted and cannot be used as source addresses.
		 */
		list_for_each_entry(transport, &asoc->peer.transport_addr_list,
					transports) {
			dst_release(transport->dst);
			sctp_transport_route(transport, NULL,
					     sctp_sk(asoc->base.sk));
		}

		if (stored)
			/* We don't need to transmit ASCONF */
			continue;
		retval = sctp_send_asconf(asoc, chunk);
	}
out:
	return retval;
}

/* set addr events to assocs in the endpoint.  ep and addr_wq must be locked */
int sctp_asconf_mgmt(struct sctp_sock *sp, struct sctp_sockaddr_entry *addrw)
{
	struct sock *sk = sctp_opt2sk(sp);
	union sctp_addr *addr;
	struct sctp_af *af;

	/* It is safe to write port space in caller. */
	addr = &addrw->a;
	addr->v4.sin_port = htons(sp->ep->base.bind_addr.port);
	af = sctp_get_af_specific(addr->sa.sa_family);
	if (!af)
		return -EINVAL;
	if (sctp_verify_addr(sk, addr, af->sockaddr_len))
		return -EINVAL;

	if (addrw->state == SCTP_ADDR_NEW)
		return sctp_send_asconf_add_ip(sk, (struct sockaddr *)addr, 1);
	else
		return sctp_send_asconf_del_ip(sk, (struct sockaddr *)addr, 1);
}

/* Helper for tunneling sctp_bindx() requests through sctp_setsockopt()
 *
 * API 8.1
 * int sctp_bindx(int sd, struct sockaddr *addrs, int addrcnt,
 *                int flags);
 *
 * If sd is an IPv4 socket, the addresses passed must be IPv4 addresses.
 * If the sd is an IPv6 socket, the addresses passed can either be IPv4
 * or IPv6 addresses.
 *
 * A single address may be specified as INADDR_ANY or IN6ADDR_ANY, see
 * Section 3.1.2 for this usage.
 *
 * addrs is a pointer to an array of one or more socket addresses. Each
 * address is contained in its appropriate structure (i.e. struct
 * sockaddr_in or struct sockaddr_in6) the family of the address type
 * must be used to distinguish the address length (note that this
 * representation is termed a "packed array" of addresses). The caller
 * specifies the number of addresses in the array with addrcnt.
 *
 * On success, sctp_bindx() returns 0. On failure, sctp_bindx() returns
 * -1, and sets errno to the appropriate error code.
 *
 * For SCTP, the port given in each socket address must be the same, or
 * sctp_bindx() will fail, setting errno to EINVAL.
 *
 * The flags parameter is formed from the bitwise OR of zero or more of
 * the following currently defined flags:
 *
 * SCTP_BINDX_ADD_ADDR
 *
 * SCTP_BINDX_REM_ADDR
 *
 * SCTP_BINDX_ADD_ADDR directs SCTP to add the given addresses to the
 * association, and SCTP_BINDX_REM_ADDR directs SCTP to remove the given
 * addresses from the association. The two flags are mutually exclusive;
 * if both are given, sctp_bindx() will fail with EINVAL. A caller may
 * not remove all addresses from an association; sctp_bindx() will
 * reject such an attempt with EINVAL.
 *
 * An application can use sctp_bindx(SCTP_BINDX_ADD_ADDR) to associate
 * additional addresses with an endpoint after calling bind().  Or use
 * sctp_bindx(SCTP_BINDX_REM_ADDR) to remove some addresses a listening
 * socket is associated with so that no new association accepted will be
 * associated with those addresses. If the endpoint supports dynamic
 * address a SCTP_BINDX_REM_ADDR or SCTP_BINDX_ADD_ADDR may cause a
 * endpoint to send the appropriate message to the peer to change the
 * peers address lists.
 *
 * Adding and removing addresses from a connected association is
 * optional functionality. Implementations that do not support this
 * functionality should return EOPNOTSUPP.
 *
 * Basically do nothing but copying the addresses from user to kernel
 * land and invoking either sctp_bindx_add() or sctp_bindx_rem() on the sk.
 * This is used for tunneling the sctp_bindx() request through sctp_setsockopt()
 * from userspace.
 *
 * We don't use copy_from_user() for optimization: we first do the
 * sanity checks (buffer size -fast- and access check-healthy
 * pointer); if all of those succeed, then we can alloc the memory
 * (expensive operation) needed to copy the data to kernel. Then we do
 * the copying without checking the user space area
 * (__copy_from_user()).
 *
 * On exit there is no need to do sockfd_put(), sys_setsockopt() does
 * it.
 *
 * sk        The sk of the socket
 * addrs     The pointer to the addresses in user land
 * addrssize Size of the addrs buffer
 * op        Operation to perform (add or remove, see the flags of
 *           sctp_bindx)
 *
 * Returns 0 if ok, <0 errno code on error.
 */
static int sctp_setsockopt_bindx(struct sock *sk,
				 struct sockaddr __user *addrs,
				 int addrs_size, int op)
{
	struct sockaddr *kaddrs;
	int err;
	int addrcnt = 0;
	int walk_size = 0;
	struct sockaddr *sa_addr;
	void *addr_buf;
	struct sctp_af *af;

	pr_debug("%s: sk:%p addrs:%p addrs_size:%d opt:%d\n",
		 __func__, sk, addrs, addrs_size, op);

	if (unlikely(addrs_size <= 0))
		return -EINVAL;

	/* Check the user passed a healthy pointer.  */
	if (unlikely(!access_ok(VERIFY_READ, addrs, addrs_size)))
		return -EFAULT;

	/* Alloc space for the address array in kernel memory.  */
	kaddrs = kmalloc(addrs_size, GFP_USER | __GFP_NOWARN);
	if (unlikely(!kaddrs))
		return -ENOMEM;

	if (__copy_from_user(kaddrs, addrs, addrs_size)) {
		kfree(kaddrs);
		return -EFAULT;
	}

	/* Walk through the addrs buffer and count the number of addresses. */
	addr_buf = kaddrs;
	while (walk_size < addrs_size) {
		if (walk_size + sizeof(sa_family_t) > addrs_size) {
			kfree(kaddrs);
			return -EINVAL;
		}

		sa_addr = addr_buf;
		af = sctp_get_af_specific(sa_addr->sa_family);

		/* If the address family is not supported or if this address
		 * causes the address buffer to overflow return EINVAL.
		 */
		if (!af || (walk_size + af->sockaddr_len) > addrs_size) {
			kfree(kaddrs);
			return -EINVAL;
		}
		addrcnt++;
		addr_buf += af->sockaddr_len;
		walk_size += af->sockaddr_len;
	}

	/* Do the work. */
	switch (op) {
	case SCTP_BINDX_ADD_ADDR:
		err = sctp_bindx_add(sk, kaddrs, addrcnt);
		if (err)
			goto out;
		err = sctp_send_asconf_add_ip(sk, kaddrs, addrcnt);
		break;

	case SCTP_BINDX_REM_ADDR:
		err = sctp_bindx_rem(sk, kaddrs, addrcnt);
		if (err)
			goto out;
		err = sctp_send_asconf_del_ip(sk, kaddrs, addrcnt);
		break;

	default:
		err = -EINVAL;
		break;
	}

out:
	kfree(kaddrs);

	return err;
}

/* __sctp_connect(struct sock* sk, struct sockaddr *kaddrs, int addrs_size)
 *
 * Common routine for handling connect() and sctp_connectx().
 * Connect will come in with just a single address.
 */
static int __sctp_connect(struct sock *sk,
			  struct sockaddr *kaddrs,
			  int addrs_size,
			  sctp_assoc_t *assoc_id)
{
	struct net *net = sock_net(sk);
	struct sctp_sock *sp;
	struct sctp_endpoint *ep;
	struct sctp_association *asoc = NULL;
	struct sctp_association *asoc2;
	struct sctp_transport *transport;
	union sctp_addr to;
	sctp_scope_t scope;
	long timeo;
	int err = 0;
	int addrcnt = 0;
	int walk_size = 0;
	union sctp_addr *sa_addr = NULL;
	void *addr_buf;
	unsigned short port;
	unsigned int f_flags = 0;

	sp = sctp_sk(sk);
	ep = sp->ep;

	/* connect() cannot be done on a socket that is already in ESTABLISHED
	 * state - UDP-style peeled off socket or a TCP-style socket that
	 * is already connected.
	 * It cannot be done even on a TCP-style listening socket.
	 */
	if (sctp_sstate(sk, ESTABLISHED) || sctp_sstate(sk, CLOSING) ||
	    (sctp_style(sk, TCP) && sctp_sstate(sk, LISTENING))) {
		err = -EISCONN;
		goto out_free;
	}

	/* Walk through the addrs buffer and count the number of addresses. */
	addr_buf = kaddrs;
	while (walk_size < addrs_size) {
		struct sctp_af *af;

		if (walk_size + sizeof(sa_family_t) > addrs_size) {
			err = -EINVAL;
			goto out_free;
		}

		sa_addr = addr_buf;
		af = sctp_get_af_specific(sa_addr->sa.sa_family);

		/* If the address family is not supported or if this address
		 * causes the address buffer to overflow return EINVAL.
		 */
		if (!af || (walk_size + af->sockaddr_len) > addrs_size) {
			err = -EINVAL;
			goto out_free;
		}

		port = ntohs(sa_addr->v4.sin_port);

		/* Save current address so we can work with it */
		memcpy(&to, sa_addr, af->sockaddr_len);

		err = sctp_verify_addr(sk, &to, af->sockaddr_len);
		if (err)
			goto out_free;

		/* Make sure the destination port is correctly set
		 * in all addresses.
		 */
		if (asoc && asoc->peer.port && asoc->peer.port != port) {
			err = -EINVAL;
			goto out_free;
		}

		/* Check if there already is a matching association on the
		 * endpoint (other than the one created here).
		 */
		asoc2 = sctp_endpoint_lookup_assoc(ep, &to, &transport);
		if (asoc2 && asoc2 != asoc) {
			if (asoc2->state >= SCTP_STATE_ESTABLISHED)
				err = -EISCONN;
			else
				err = -EALREADY;
			goto out_free;
		}

		/* If we could not find a matching association on the endpoint,
		 * make sure that there is no peeled-off association matching
		 * the peer address even on another socket.
		 */
		if (sctp_endpoint_is_peeled_off(ep, &to)) {
			err = -EADDRNOTAVAIL;
			goto out_free;
		}

		if (!asoc) {
			/* If a bind() or sctp_bindx() is not called prior to
			 * an sctp_connectx() call, the system picks an
			 * ephemeral port and will choose an address set
			 * equivalent to binding with a wildcard address.
			 */
			if (!ep->base.bind_addr.port) {
				if (sctp_autobind(sk)) {
					err = -EAGAIN;
					goto out_free;
				}
			} else {
				/*
				 * If an unprivileged user inherits a 1-many
				 * style socket with open associations on a
				 * privileged port, it MAY be permitted to
				 * accept new associations, but it SHOULD NOT
				 * be permitted to open new associations.
				 */
				if (ep->base.bind_addr.port < PROT_SOCK &&
				    !ns_capable(net->user_ns, CAP_NET_BIND_SERVICE)) {
					err = -EACCES;
					goto out_free;
				}
			}

			scope = sctp_scope(&to);
			asoc = sctp_association_new(ep, sk, scope, GFP_KERNEL);
			if (!asoc) {
				err = -ENOMEM;
				goto out_free;
			}

			err = sctp_assoc_set_bind_addr_from_ep(asoc, scope,
							      GFP_KERNEL);
			if (err < 0) {
				goto out_free;
			}

		}

		/* Prime the peer's transport structures.  */
		transport = sctp_assoc_add_peer(asoc, &to, GFP_KERNEL,
						SCTP_UNKNOWN);
		if (!transport) {
			err = -ENOMEM;
			goto out_free;
		}

		addrcnt++;
		addr_buf += af->sockaddr_len;
		walk_size += af->sockaddr_len;
	}

	/* In case the user of sctp_connectx() wants an association
	 * id back, assign one now.
	 */
	if (assoc_id) {
		err = sctp_assoc_set_id(asoc, GFP_KERNEL);
		if (err < 0)
			goto out_free;
	}

	err = sctp_primitive_ASSOCIATE(net, asoc, NULL);
	if (err < 0) {
		goto out_free;
	}

	/* Initialize sk's dport and daddr for getpeername() */
	inet_sk(sk)->inet_dport = htons(asoc->peer.port);
	sp->pf->to_sk_daddr(sa_addr, sk);
	sk->sk_err = 0;

	/* in-kernel sockets don't generally have a file allocated to them
	 * if all they do is call sock_create_kern().
	 */
	if (sk->sk_socket->file)
		f_flags = sk->sk_socket->file->f_flags;

	timeo = sock_sndtimeo(sk, f_flags & O_NONBLOCK);

	err = sctp_wait_for_connect(asoc, &timeo);
	if ((err == 0 || err == -EINPROGRESS) && assoc_id)
		*assoc_id = asoc->assoc_id;

	/* Don't free association on exit. */
	asoc = NULL;

out_free:
	pr_debug("%s: took out_free path with asoc:%p kaddrs:%p err:%d\n",
		 __func__, asoc, kaddrs, err);

	if (asoc) {
		/* sctp_primitive_ASSOCIATE may have added this association
		 * To the hash table, try to unhash it, just in case, its a noop
		 * if it wasn't hashed so we're safe
		 */
		sctp_association_free(asoc);
	}
	return err;
}

/* Helper for tunneling sctp_connectx() requests through sctp_setsockopt()
 *
 * API 8.9
 * int sctp_connectx(int sd, struct sockaddr *addrs, int addrcnt,
 * 			sctp_assoc_t *asoc);
 *
 * If sd is an IPv4 socket, the addresses passed must be IPv4 addresses.
 * If the sd is an IPv6 socket, the addresses passed can either be IPv4
 * or IPv6 addresses.
 *
 * A single address may be specified as INADDR_ANY or IN6ADDR_ANY, see
 * Section 3.1.2 for this usage.
 *
 * addrs is a pointer to an array of one or more socket addresses. Each
 * address is contained in its appropriate structure (i.e. struct
 * sockaddr_in or struct sockaddr_in6) the family of the address type
 * must be used to distengish the address length (note that this
 * representation is termed a "packed array" of addresses). The caller
 * specifies the number of addresses in the array with addrcnt.
 *
 * On success, sctp_connectx() returns 0. It also sets the assoc_id to
 * the association id of the new association.  On failure, sctp_connectx()
 * returns -1, and sets errno to the appropriate error code.  The assoc_id
 * is not touched by the kernel.
 *
 * For SCTP, the port given in each socket address must be the same, or
 * sctp_connectx() will fail, setting errno to EINVAL.
 *
 * An application can use sctp_connectx to initiate an association with
 * an endpoint that is multi-homed.  Much like sctp_bindx() this call
 * allows a caller to specify multiple addresses at which a peer can be
 * reached.  The way the SCTP stack uses the list of addresses to set up
 * the association is implementation dependent.  This function only
 * specifies that the stack will try to make use of all the addresses in
 * the list when needed.
 *
 * Note that the list of addresses passed in is only used for setting up
 * the association.  It does not necessarily equal the set of addresses
 * the peer uses for the resulting association.  If the caller wants to
 * find out the set of peer addresses, it must use sctp_getpaddrs() to
 * retrieve them after the association has been set up.
 *
 * Basically do nothing but copying the addresses from user to kernel
 * land and invoking either sctp_connectx(). This is used for tunneling
 * the sctp_connectx() request through sctp_setsockopt() from userspace.
 *
 * We don't use copy_from_user() for optimization: we first do the
 * sanity checks (buffer size -fast- and access check-healthy
 * pointer); if all of those succeed, then we can alloc the memory
 * (expensive operation) needed to copy the data to kernel. Then we do
 * the copying without checking the user space area
 * (__copy_from_user()).
 *
 * On exit there is no need to do sockfd_put(), sys_setsockopt() does
 * it.
 *
 * sk        The sk of the socket
 * addrs     The pointer to the addresses in user land
 * addrssize Size of the addrs buffer
 *
 * Returns >=0 if ok, <0 errno code on error.
 */
static int __sctp_setsockopt_connectx(struct sock *sk,
				      struct sockaddr __user *addrs,
				      int addrs_size,
				      sctp_assoc_t *assoc_id)
{
	struct sockaddr *kaddrs;
	gfp_t gfp = GFP_KERNEL;
	int err = 0;

	pr_debug("%s: sk:%p addrs:%p addrs_size:%d\n",
		 __func__, sk, addrs, addrs_size);

	if (unlikely(addrs_size <= 0))
		return -EINVAL;

	/* Check the user passed a healthy pointer.  */
	if (unlikely(!access_ok(VERIFY_READ, addrs, addrs_size)))
		return -EFAULT;

	/* Alloc space for the address array in kernel memory.  */
	if (sk->sk_socket->file)
		gfp = GFP_USER | __GFP_NOWARN;
	kaddrs = kmalloc(addrs_size, gfp);
	if (unlikely(!kaddrs))
		return -ENOMEM;

	if (__copy_from_user(kaddrs, addrs, addrs_size)) {
		err = -EFAULT;
	} else {
		err = __sctp_connect(sk, kaddrs, addrs_size, assoc_id);
	}

	kfree(kaddrs);

	return err;
}

/*
 * This is an older interface.  It's kept for backward compatibility
 * to the option that doesn't provide association id.
 */
static int sctp_setsockopt_connectx_old(struct sock *sk,
					struct sockaddr __user *addrs,
					int addrs_size)
{
	return __sctp_setsockopt_connectx(sk, addrs, addrs_size, NULL);
}

/*
 * New interface for the API.  The since the API is done with a socket
 * option, to make it simple we feed back the association id is as a return
 * indication to the call.  Error is always negative and association id is
 * always positive.
 */
static int sctp_setsockopt_connectx(struct sock *sk,
				    struct sockaddr __user *addrs,
				    int addrs_size)
{
	sctp_assoc_t assoc_id = 0;
	int err = 0;

	err = __sctp_setsockopt_connectx(sk, addrs, addrs_size, &assoc_id);

	if (err)
		return err;
	else
		return assoc_id;
}

/*
 * New (hopefully final) interface for the API.
 * We use the sctp_getaddrs_old structure so that use-space library
 * can avoid any unnecessary allocations. The only different part
 * is that we store the actual length of the address buffer into the
 * addrs_num structure member. That way we can re-use the existing
 * code.
 */
#ifdef CONFIG_COMPAT
struct compat_sctp_getaddrs_old {
	sctp_assoc_t	assoc_id;
	s32		addr_num;
	compat_uptr_t	addrs;		/* struct sockaddr * */
};
#endif

static int sctp_getsockopt_connectx3(struct sock *sk, int len,
				     char __user *optval,
				     int __user *optlen)
{
	struct sctp_getaddrs_old param;
	sctp_assoc_t assoc_id = 0;
	int err = 0;

#ifdef CONFIG_COMPAT
	if (in_compat_syscall()) {
		struct compat_sctp_getaddrs_old param32;

		if (len < sizeof(param32))
			return -EINVAL;
		if (copy_from_user(&param32, optval, sizeof(param32)))
			return -EFAULT;

		param.assoc_id = param32.assoc_id;
		param.addr_num = param32.addr_num;
		param.addrs = compat_ptr(param32.addrs);
	} else
#endif
	{
		if (len < sizeof(param))
			return -EINVAL;
		if (copy_from_user(&param, optval, sizeof(param)))
			return -EFAULT;
	}

	err = __sctp_setsockopt_connectx(sk, (struct sockaddr __user *)
					 param.addrs, param.addr_num,
					 &assoc_id);
	if (err == 0 || err == -EINPROGRESS) {
		if (copy_to_user(optval, &assoc_id, sizeof(assoc_id)))
			return -EFAULT;
		if (put_user(sizeof(assoc_id), optlen))
			return -EFAULT;
	}

	return err;
}

/* API 3.1.4 close() - UDP Style Syntax
 * Applications use close() to perform graceful shutdown (as described in
 * Section 10.1 of [SCTP]) on ALL the associations currently represented
 * by a UDP-style socket.
 *
 * The syntax is
 *
 *   ret = close(int sd);
 *
 *   sd      - the socket descriptor of the associations to be closed.
 *
 * To gracefully shutdown a specific association represented by the
 * UDP-style socket, an application should use the sendmsg() call,
 * passing no user data, but including the appropriate flag in the
 * ancillary data (see Section xxxx).
 *
 * If sd in the close() call is a branched-off socket representing only
 * one association, the shutdown is performed on that association only.
 *
 * 4.1.6 close() - TCP Style Syntax
 *
 * Applications use close() to gracefully close down an association.
 *
 * The syntax is:
 *
 *    int close(int sd);
 *
 *      sd      - the socket descriptor of the association to be closed.
 *
 * After an application calls close() on a socket descriptor, no further
 * socket operations will succeed on that descriptor.
 *
 * API 7.1.4 SO_LINGER
 *
 * An application using the TCP-style socket can use this option to
 * perform the SCTP ABORT primitive.  The linger option structure is:
 *
 *  struct  linger {
 *     int     l_onoff;                // option on/off
 *     int     l_linger;               // linger time
 * };
 *
 * To enable the option, set l_onoff to 1.  If the l_linger value is set
 * to 0, calling close() is the same as the ABORT primitive.  If the
 * value is set to a negative value, the setsockopt() call will return
 * an error.  If the value is set to a positive value linger_time, the
 * close() can be blocked for at most linger_time ms.  If the graceful
 * shutdown phase does not finish during this period, close() will
 * return but the graceful shutdown phase continues in the system.
 */
static void sctp_close(struct sock *sk, long timeout)
{
	struct net *net = sock_net(sk);
	struct sctp_endpoint *ep;
	struct sctp_association *as