text: /* 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.
   *
   * This file is part of the SCTP kernel implementation
   *
   * The base lksctp header.
   *
   * 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>
   *    Xingang Guo           <xingang.guo@intel.com>
   *    Jon Grimm             <jgrimm@us.ibm.com>
   *    Daisy Chang           <daisyc@us.ibm.com>
   *    Sridhar Samudrala     <sri@us.ibm.com>
   *    Ardelle Fan           <ardelle.fan@intel.com>
   *    Ryan Layer            <rmlayer@us.ibm.com>
   *    Kevin Gao             <kevin.gao@intel.com> 
   */
  
  #ifndef __net_sctp_h__
  #define __net_sctp_h__
  
  /* Header Strategy.
   *    Start getting some control over the header file depencies:
   *       includes
   *       constants
   *       structs
   *       prototypes
   *       macros, externs, and inlines
   *
   *   Move test_frame specific items out of the kernel headers
   *   and into the test frame headers.   This is not perfect in any sense
   *   and will continue to evolve.
   */
  
  #include <linux/types.h>
  #include <linux/slab.h>
  #include <linux/in.h>
  #include <linux/tty.h>
  #include <linux/proc_fs.h>
  #include <linux/spinlock.h>
  #include <linux/jiffies.h>
  #include <linux/idr.h>
  
  #if IS_ENABLED(CONFIG_IPV6)
  #include <net/ipv6.h>
  #include <net/ip6_route.h>
  #endif
  
  #include <linux/uaccess.h>
  #include <asm/page.h>
  #include <net/sock.h>
  #include <net/snmp.h>
  #include <net/sctp/structs.h>
  #include <net/sctp/constants.h>
  
  #ifdef CONFIG_IP_SCTP_MODULE
  #define SCTP_PROTOSW_FLAG 0
  #else /* static! */
  #define SCTP_PROTOSW_FLAG INET_PROTOSW_PERMANENT
  #endif
  
  /* Round an int up to the next multiple of 4.  */
  #define SCTP_PAD4(s) (((s)+3)&~3)
  /* Truncate to the previous multiple of 4.  */
  #define SCTP_TRUNC4(s) ((s)&~3)
  
  /*
   * Function declarations.
   */
  
  /*
   * sctp/protocol.c
   */
  int sctp_copy_local_addr_list(struct net *net, struct sctp_bind_addr *addr,
  			      enum sctp_scope, gfp_t gfp, int flags);
  struct sctp_pf *sctp_get_pf_specific(sa_family_t family);
  int sctp_register_pf(struct sctp_pf *, sa_family_t);
  void sctp_addr_wq_mgmt(struct net *, struct sctp_sockaddr_entry *, int);
  
  /*
   * sctp/socket.c
   */
  int sctp_inet_connect(struct socket *sock, struct sockaddr *uaddr,
  		      int addr_len, int flags);
  int sctp_backlog_rcv(struct sock *sk, struct sk_buff *skb);
  int sctp_inet_listen(struct socket *sock, int backlog);
  void sctp_write_space(struct sock *sk);
  void sctp_data_ready(struct sock *sk);
  __poll_t sctp_poll(struct file *file, struct socket *sock,
  		poll_table *wait);
  void sctp_sock_rfree(struct sk_buff *skb);
  void sctp_copy_sock(struct sock *newsk, struct sock *sk,
  		    struct sctp_association *asoc);
  extern struct percpu_counter sctp_sockets_allocated;
  int sctp_asconf_mgmt(struct sctp_sock *, struct sctp_sockaddr_entry *);
  struct sk_buff *sctp_skb_recv_datagram(struct sock *, int, int, int *);
  
  void sctp_transport_walk_start(struct rhashtable_iter *iter);
  void sctp_transport_walk_stop(struct rhashtable_iter *iter);
  struct sctp_transport *sctp_transport_get_next(struct net *net,
  			struct rhashtable_iter *iter);
  struct sctp_transport *sctp_transport_get_idx(struct net *net,
  			struct rhashtable_iter *iter, int pos);
  int sctp_transport_lookup_process(int (*cb)(struct sctp_transport *, void *),
  				  struct net *net,
  				  const union sctp_addr *laddr,
  				  const union sctp_addr *paddr, void *p);
  int sctp_for_each_transport(int (*cb)(struct sctp_transport *, void *),
  			    int (*cb_done)(struct sctp_transport *, void *),
  			    struct net *net, int *pos, void *p);
  int sctp_for_each_endpoint(int (*cb)(struct sctp_endpoint *, void *), void *p);
  int sctp_get_sctp_info(struct sock *sk, struct sctp_association *asoc,
  		       struct sctp_info *info);
  
  /*
   * sctp/primitive.c
   */
  int sctp_primitive_ASSOCIATE(struct net *, struct sctp_association *, void *arg);
  int sctp_primitive_SHUTDOWN(struct net *, struct sctp_association *, void *arg);
  int sctp_primitive_ABORT(struct net *, struct sctp_association *, void *arg);
  int sctp_primitive_SEND(struct net *, struct sctp_association *, void *arg);
  int sctp_primitive_REQUESTHEARTBEAT(struct net *, struct sctp_association *, void *arg);
  int sctp_primitive_ASCONF(struct net *, struct sctp_association *, void *arg);
  int sctp_primitive_RECONF(struct net *net, struct sctp_association *asoc,
  			  void *arg);
  
  /*
   * sctp/input.c
   */
  int sctp_rcv(struct sk_buff *skb);
  void sctp_v4_err(struct sk_buff *skb, u32 info);
  void sctp_hash_endpoint(struct sctp_endpoint *);
  void sctp_unhash_endpoint(struct sctp_endpoint *);
  struct sock *sctp_err_lookup(struct net *net, int family, struct sk_buff *,
  			     struct sctphdr *, struct sctp_association **,
  			     struct sctp_transport **);
  void sctp_err_finish(struct sock *, struct sctp_transport *);
  void sctp_icmp_frag_needed(struct sock *, struct sctp_association *,
  			   struct sctp_transport *t, __u32 pmtu);
  void sctp_icmp_redirect(struct sock *, struct sctp_transport *,
  			struct sk_buff *);
  void sctp_icmp_proto_unreachable(struct sock *sk,
  				 struct sctp_association *asoc,
  				 struct sctp_transport *t);
  void sctp_backlog_migrate(struct sctp_association *assoc,
  			  struct sock *oldsk, struct sock *newsk);
  int sctp_transport_hashtable_init(void);
  void sctp_transport_hashtable_destroy(void);
  int sctp_hash_transport(struct sctp_transport *t);
  void sctp_unhash_transport(struct sctp_transport *t);
  struct sctp_transport *sctp_addrs_lookup_transport(
  				struct net *net,
  				const union sctp_addr *laddr,
  				const union sctp_addr *paddr);
  struct sctp_transport *sctp_epaddr_lookup_transport(
  				const struct sctp_endpoint *ep,
  				const union sctp_addr *paddr);
  
  /*
   * sctp/proc.c
   */
  int __net_init sctp_proc_init(struct net *net);
  
  /*
   * sctp/offload.c
   */
  int sctp_offload_init(void);
  
  /*
   * sctp/stream_sched.c
   */
  void sctp_sched_ops_init(void);
  
  /*
   * sctp/stream.c
   */
  int sctp_send_reset_streams(struct sctp_association *asoc,
  			    struct sctp_reset_streams *params);
  int sctp_send_reset_assoc(struct sctp_association *asoc);
  int sctp_send_add_streams(struct sctp_association *asoc,
  			  struct sctp_add_streams *params);
  
  /*
   * Module global variables
   */
  
   /*
    * sctp/protocol.c
    */
  extern struct kmem_cache *sctp_chunk_cachep __read_mostly;
  extern struct kmem_cache *sctp_bucket_cachep __read_mostly;
  extern long sysctl_sctp_mem[3];
  extern int sysctl_sctp_rmem[3];
  extern int sysctl_sctp_wmem[3];
  
  /*
   *  Section:  Macros, externs, and inlines
   */
  
  /* SCTP SNMP MIB stats handlers */
  #define SCTP_INC_STATS(net, field)	SNMP_INC_STATS((net)->sctp.sctp_statistics, field)
  #define __SCTP_INC_STATS(net, field)	__SNMP_INC_STATS((net)->sctp.sctp_statistics, field)
  #define SCTP_DEC_STATS(net, field)	SNMP_DEC_STATS((net)->sctp.sctp_statistics, field)
  
  /* sctp mib definitions */
  enum {
  	SCTP_MIB_NUM = 0,
  	SCTP_MIB_CURRESTAB,			/* CurrEstab */
  	SCTP_MIB_ACTIVEESTABS,			/* ActiveEstabs */
  	SCTP_MIB_PASSIVEESTABS,			/* PassiveEstabs */
  	SCTP_MIB_ABORTEDS,			/* Aborteds */
  	SCTP_MIB_SHUTDOWNS,			/* Shutdowns */
  	SCTP_MIB_OUTOFBLUES,			/* OutOfBlues */
  	SCTP_MIB_CHECKSUMERRORS,		/* ChecksumErrors */
  	SCTP_MIB_OUTCTRLCHUNKS,			/* OutCtrlChunks */
  	SCTP_MIB_OUTORDERCHUNKS,		/* OutOrderChunks */
  	SCTP_MIB_OUTUNORDERCHUNKS,		/* OutUnorderChunks */
  	SCTP_MIB_INCTRLCHUNKS,			/* InCtrlChunks */
  	SCTP_MIB_INORDERCHUNKS,			/* InOrderChunks */
  	SCTP_MIB_INUNORDERCHUNKS,		/* InUnorderChunks */
  	SCTP_MIB_FRAGUSRMSGS,			/* FragUsrMsgs */
  	SCTP_MIB_REASMUSRMSGS,			/* ReasmUsrMsgs */
  	SCTP_MIB_OUTSCTPPACKS,			/* OutSCTPPacks */
  	SCTP_MIB_INSCTPPACKS,			/* InSCTPPacks */
  	SCTP_MIB_T1_INIT_EXPIREDS,
  	SCTP_MIB_T1_COOKIE_EXPIREDS,
  	SCTP_MIB_T2_SHUTDOWN_EXPIREDS,
  	SCTP_MIB_T3_RTX_EXPIREDS,
  	SCTP_MIB_T4_RTO_EXPIREDS,
  	SCTP_MIB_T5_SHUTDOWN_GUARD_EXPIREDS,
  	SCTP_MIB_DELAY_SACK_EXPIREDS,
  	SCTP_MIB_AUTOCLOSE_EXPIREDS,
  	SCTP_MIB_T1_RETRANSMITS,
  	SCTP_MIB_T3_RETRANSMITS,
  	SCTP_MIB_PMTUD_RETRANSMITS,
  	SCTP_MIB_FAST_RETRANSMITS,
  	SCTP_MIB_IN_PKT_SOFTIRQ,
  	SCTP_MIB_IN_PKT_BACKLOG,
  	SCTP_MIB_IN_PKT_DISCARDS,
  	SCTP_MIB_IN_DATA_CHUNK_DISCARDS,
  	__SCTP_MIB_MAX
  };
  
  #define SCTP_MIB_MAX    __SCTP_MIB_MAX
  struct sctp_mib {
          unsigned long   mibs[SCTP_MIB_MAX];
  };
  
  /* helper function to track stats about max rto and related transport */
  static inline void sctp_max_rto(struct sctp_association *asoc,
  				struct sctp_transport *trans)
  {
  	if (asoc->stats.max_obs_rto < (__u64)trans->rto) {
  		asoc->stats.max_obs_rto = trans->rto;
  		memset(&asoc->stats.obs_rto_ipaddr, 0,
  			sizeof(struct sockaddr_storage));
  		memcpy(&asoc->stats.obs_rto_ipaddr, &trans->ipaddr,
  			trans->af_specific->sockaddr_len);
  	}
  }
  
  /*
   * Macros for keeping a global reference of object allocations.
   */
  #ifdef CONFIG_SCTP_DBG_OBJCNT
  
  extern atomic_t sctp_dbg_objcnt_sock;
  extern atomic_t sctp_dbg_objcnt_ep;
  extern atomic_t sctp_dbg_objcnt_assoc;
  extern atomic_t sctp_dbg_objcnt_transport;
  extern atomic_t sctp_dbg_objcnt_chunk;
  extern atomic_t sctp_dbg_objcnt_bind_addr;
  extern atomic_t sctp_dbg_objcnt_bind_bucket;
  extern atomic_t sctp_dbg_objcnt_addr;
  extern atomic_t sctp_dbg_objcnt_datamsg;
  extern atomic_t sctp_dbg_objcnt_keys;
  
  /* Macros to atomically increment/decrement objcnt counters.  */
  #define SCTP_DBG_OBJCNT_INC(name) \
  atomic_inc(&sctp_dbg_objcnt_## name)
  #define SCTP_DBG_OBJCNT_DEC(name) \
  atomic_dec(&sctp_dbg_objcnt_## name)
  #define SCTP_DBG_OBJCNT(name) \
  atomic_t sctp_dbg_objcnt_## name = ATOMIC_INIT(0)
  
  /* Macro to help create new entries in in the global array of
   * objcnt counters.
   */
  #define SCTP_DBG_OBJCNT_ENTRY(name) \
  {.label= #name, .counter= &sctp_dbg_objcnt_## name}
  
  void sctp_dbg_objcnt_init(struct net *);
  
  #else
  
  #define SCTP_DBG_OBJCNT_INC(name)
  #define SCTP_DBG_OBJCNT_DEC(name)
  
  static inline void sctp_dbg_objcnt_init(struct net *net) { return; }
  
  #endif /* CONFIG_SCTP_DBG_OBJCOUNT */
  
  #if defined CONFIG_SYSCTL
  void sctp_sysctl_register(void);
  void sctp_sysctl_unregister(void);
  int sctp_sysctl_net_register(struct net *net);
  void sctp_sysctl_net_unregister(struct net *net);
  #else
  static inline void sctp_sysctl_register(void) { return; }
  static inline void sctp_sysctl_unregister(void) { return; }
  static inline int sctp_sysctl_net_register(struct net *net) { return 0; }
  static inline void sctp_sysctl_net_unregister(struct net *net) { return; }
  #endif
  
  /* Size of Supported Address Parameter for 'x' address types. */
  #define SCTP_SAT_LEN(x) (sizeof(struct sctp_paramhdr) + (x) * sizeof(__u16))
  
  #if IS_ENABLED(CONFIG_IPV6)
  
  void sctp_v6_pf_init(void);
  void sctp_v6_pf_exit(void);
  int sctp_v6_protosw_init(void);
  void sctp_v6_protosw_exit(void);
  int sctp_v6_add_protocol(void);
  void sctp_v6_del_protocol(void);
  
  #else /* #ifdef defined(CONFIG_IPV6) */
  
  static inline void sctp_v6_pf_init(void) { return; }
  static inline void sctp_v6_pf_exit(void) { return; }
  static inline int sctp_v6_protosw_init(void) { return 0; }
  static inline void sctp_v6_protosw_exit(void) { return; }
  static inline int sctp_v6_add_protocol(void) { return 0; }
  static inline void sctp_v6_del_protocol(void) { return; }
  
  #endif /* #if defined(CONFIG_IPV6) */
  
  
  /* Map an association to an assoc_id. */
  static inline sctp_assoc_t sctp_assoc2id(const struct sctp_association *asoc)
  {
  	return asoc ? asoc->assoc_id : 0;
  }
  
  static inline enum sctp_sstat_state
  sctp_assoc_to_state(const struct sctp_association *asoc)
  {
  	/* SCTP's uapi always had SCTP_EMPTY(=0) as a dummy state, but we
  	 * got rid of it in kernel space. Therefore SCTP_CLOSED et al
  	 * start at =1 in user space, but actually as =0 in kernel space.
  	 * Now that we can not break user space and SCTP_EMPTY is exposed
  	 * there, we need to fix it up with an ugly offset not to break
  	 * applications. :(
  	 */
  	return asoc->state + 1;
  }
  
  /* Look up the association by its id.  */
  struct sctp_association *sctp_id2assoc(struct sock *sk, sctp_assoc_t id);
  
  int sctp_do_peeloff(struct sock *sk, sctp_assoc_t id, struct socket **sockp);
  
  /* A macro to walk a list of skbs.  */
  #define sctp_skb_for_each(pos, head, tmp) \
  	skb_queue_walk_safe(head, pos, tmp)
  
  /**
   *	sctp_list_dequeue - remove from the head of the queue
   *	@list: list to dequeue from
   *
   *	Remove the head of the list. The head item is
   *	returned or %NULL if the list is empty.
   */
  
  static inline struct list_head *sctp_list_dequeue(struct list_head *list)
  {
  	struct list_head *result = NULL;
  
  	if (!list_empty(list)) {
  		result = list->next;
  		list_del_init(result);
  	}
  	return result;
  }
  
  /* SCTP version of skb_set_owner_r.  We need this one because
   * of the way we have to do receive buffer accounting on bundled
   * chunks.
   */
  static inline void sctp_skb_set_owner_r(struct sk_buff *skb, struct sock *sk)
  {
  	struct sctp_ulpevent *event = sctp_skb2event(skb);
  
  	skb_orphan(skb);
  	skb->sk = sk;
  	skb->destructor = sctp_sock_rfree;
  	atomic_add(event->rmem_len, &sk->sk_rmem_alloc);
  	/*
  	 * This mimics the behavior of skb_set_owner_r
  	 */
  	sk->sk_forward_alloc -= event->rmem_len;
  }
  
  /* Tests if the list has one and only one entry. */
  static inline int sctp_list_single_entry(struct list_head *head)
  {
  	return (head->next != head) && (head->next == head->prev);
  }
  
  /* Break down data chunks at this point.  */
  static inline int sctp_frag_point(const struct sctp_association *asoc, int pmtu)
  {
  	struct sctp_sock *sp = sctp_sk(asoc->base.sk);
  	struct sctp_af *af = sp->pf->af;
  	int frag = pmtu;
  
  	frag -= af->ip_options_len(asoc->base.sk);
  	frag -= af->net_header_len;
  	frag -= sizeof(struct sctphdr) + sctp_datachk_len(&asoc->stream);
  
  	if (asoc->user_frag)
  		frag = min_t(int, frag, asoc->user_frag);
  
  	frag = SCTP_TRUNC4(min_t(int, frag, SCTP_MAX_CHUNK_LEN -
  					    sctp_datachk_len(&asoc->stream)));
  
  	return frag;
  }
  
  static inline void sctp_assoc_pending_pmtu(struct sctp_association *asoc)
  {
  	sctp_assoc_sync_pmtu(asoc);
  	asoc->pmtu_pending = 0;
  }
  
  static inline bool sctp_chunk_pending(const struct sctp_chunk *chunk)
  {
  	return !list_empty(&chunk->list);
  }
  
  /* Walk through a list of TLV parameters.  Don't trust the
   * individual parameter lengths and instead depend on
   * the chunk length to indicate when to stop.  Make sure
   * there is room for a param header too.
   */
  #define sctp_walk_params(pos, chunk, member)\
  _sctp_walk_params((pos), (chunk), ntohs((chunk)->chunk_hdr.length), member)
  
  #define _sctp_walk_params(pos, chunk, end, member)\
  for (pos.v = chunk->member;\
       (pos.v + offsetof(struct sctp_paramhdr, length) + sizeof(pos.p->length) <=\
        (void *)chunk + end) &&\
       pos.v <= (void *)chunk + end - ntohs(pos.p->length) &&\
       ntohs(pos.p->length) >= sizeof(struct sctp_paramhdr);\
       pos.v += SCTP_PAD4(ntohs(pos.p->length)))
  
  #define sctp_walk_errors(err, chunk_hdr)\
  _sctp_walk_errors((err), (chunk_hdr), ntohs((chunk_hdr)->length))
  
  #define _sctp_walk_errors(err, chunk_hdr, end)\
  for (err = (struct sctp_errhdr *)((void *)chunk_hdr + \
  	    sizeof(struct sctp_chunkhdr));\
       ((void *)err + offsetof(struct sctp_errhdr, length) + sizeof(err->length) <=\
        (void *)chunk_hdr + end) &&\
       (void *)err <= (void *)chunk_hdr + end - ntohs(err->length) &&\
       ntohs(err->length) >= sizeof(struct sctp_errhdr); \
       err = (struct sctp_errhdr *)((void *)err + SCTP_PAD4(ntohs(err->length))))
  
  #define sctp_walk_fwdtsn(pos, chunk)\
  _sctp_walk_fwdtsn((pos), (chunk), ntohs((chunk)->chunk_hdr->length) - sizeof(struct sctp_fwdtsn_chunk))
  
  #define _sctp_walk_fwdtsn(pos, chunk, end)\
  for (pos = chunk->subh.fwdtsn_hdr->skip;\
       (void *)pos <= (void *)chunk->subh.fwdtsn_hdr->skip + end - sizeof(struct sctp_fwdtsn_skip);\
       pos++)
  
  /* External references. */
  
  extern struct proto sctp_prot;
  extern struct proto sctpv6_prot;
  void sctp_put_port(struct sock *sk);
  
  extern struct idr sctp_assocs_id;
  extern spinlock_t sctp_assocs_id_lock;
  
  /* Static inline functions. */
  
  /* Convert from an IP version number to an Address Family symbol.  */
  static inline int ipver2af(__u8 ipver)
  {
  	switch (ipver) {
  	case 4:
  	        return  AF_INET;
  	case 6:
  		return AF_INET6;
  	default:
  		return 0;
  	}
  }
  
  /* Convert from an address parameter type to an address family.  */
  static inline int param_type2af(__be16 type)
  {
  	switch (type) {
  	case SCTP_PARAM_IPV4_ADDRESS:
  	        return  AF_INET;
  	case SCTP_PARAM_IPV6_ADDRESS:
  		return AF_INET6;
  	default:
  		return 0;
  	}
  }
  
  /* Warning: The following hash functions assume a power of two 'size'. */
  /* This is the hash function for the SCTP port hash table. */
  static inline int sctp_phashfn(struct net *net, __u16 lport)
  {
  	return (net_hash_mix(net) + lport) & (sctp_port_hashsize - 1);
  }
  
  /* This is the hash function for the endpoint hash table. */
  static inline int sctp_ep_hashfn(struct net *net, __u16 lport)
  {
  	return (net_hash_mix(net) + lport) & (sctp_ep_hashsize - 1);
  }
  
  #define sctp_for_each_hentry(epb, head) \
  	hlist_for_each_entry(epb, head, node)
  
  /* Is a socket of this style? */
  #define sctp_style(sk, style) __sctp_style((sk), (SCTP_SOCKET_##style))
  static inline int __sctp_style(const struct sock *sk,
  			       enum sctp_socket_type style)
  {
  	return sctp_sk(sk)->type == style;
  }
  
  /* Is the association in this state? */
  #define sctp_state(asoc, state) __sctp_state((asoc), (SCTP_STATE_##state))
  static inline int __sctp_state(const struct sctp_association *asoc,
  			       enum sctp_state state)
  {
  	return asoc->state == state;
  }
  
  /* Is the socket in this state? */
  #define sctp_sstate(sk, state) __sctp_sstate((sk), (SCTP_SS_##state))
  static inline int __sctp_sstate(const struct sock *sk,
  				enum sctp_sock_state state)
  {
  	return sk->sk_state == state;
  }
  
  /* Map v4-mapped v6 address back to v4 address */
  static inline void sctp_v6_map_v4(union sctp_addr *addr)
  {
  	addr->v4.sin_family = AF_INET;
  	addr->v4.sin_port = addr->v6.sin6_port;
  	addr->v4.sin_addr.s_addr = addr->v6.sin6_addr.s6_addr32[3];
  }
  
  /* Map v4 address to v4-mapped v6 address */
  static inline void sctp_v4_map_v6(union sctp_addr *addr)
  {
  	__be16 port;
  
  	port = addr->v4.sin_port;
  	addr->v6.sin6_addr.s6_addr32[3] = addr->v4.sin_addr.s_addr;
  	addr->v6.sin6_port = port;
  	addr->v6.sin6_family = AF_INET6;
  	addr->v6.sin6_flowinfo = 0;
  	addr->v6.sin6_scope_id = 0;
  	addr->v6.sin6_addr.s6_addr32[0] = 0;
  	addr->v6.sin6_addr.s6_addr32[1] = 0;
  	addr->v6.sin6_addr.s6_addr32[2] = htonl(0x0000ffff);
  }
  
  /* The cookie is always 0 since this is how it's used in the
   * pmtu code.
   */
  static inline struct dst_entry *sctp_transport_dst_check(struct sctp_transport *t)
  {
  	if (t->dst && !dst_check(t->dst, t->dst_cookie))
  		sctp_transport_dst_release(t);
  
  	return t->dst;
  }
  
  static inline bool sctp_transport_pmtu_check(struct sctp_transport *t)
  {
  	__u32 pmtu = max_t(size_t, SCTP_TRUNC4(dst_mtu(t->dst)),
  			   SCTP_DEFAULT_MINSEGMENT);
  
  	if (t->pathmtu == pmtu)
  		return true;
  
  	t->pathmtu = pmtu;
  
  	return false;
  }
  
  #endif /* __net_sctp_h__ */
  