include/net/sctp/command.h - third_party/kernel - Git at Google

 /* SPDX-License-Identifier: GPL-2.0-or-later */
 /* SCTP kernel Implementation
  * (C) Copyright IBM Corp. 2001, 2004
  * Copyright (C) 1999-2001 Cisco, Motorola
  *
  * This file is part of the SCTP kernel implementation
  *
  * These are the definitions needed for the command object.
  *
  * 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>
  *   Karl Knutson <karl@athena.chicago.il.us>
  *   Ardelle Fan <ardelle.fan@intel.com>
  *   Sridhar Samudrala <sri@us.ibm.com>
  */

 #ifndef __net_sctp_command_h__
 #define __net_sctp_command_h__

 #include <net/sctp/constants.h>
 #include <net/sctp/structs.h>


 enum sctp_verb {
 	SCTP_CMD_NOP = 0,	/* Do nothing. */
 	SCTP_CMD_NEW_ASOC,	/* Register a new association.  */
 	SCTP_CMD_DELETE_TCB,	/* Delete the current association. */
 	SCTP_CMD_NEW_STATE,	/* Enter a new state.  */
 	SCTP_CMD_REPORT_TSN,	/* Record the arrival of a TSN.  */
 	SCTP_CMD_GEN_SACK,	/* Send a Selective ACK (maybe).  */
 	SCTP_CMD_PROCESS_SACK,	/* Process an inbound SACK.  */
 	SCTP_CMD_GEN_INIT_ACK,	/* Generate an INIT ACK chunk.  */
 	SCTP_CMD_PEER_INIT,	/* Process a INIT from the peer.  */
 	SCTP_CMD_GEN_COOKIE_ECHO, /* Generate a COOKIE ECHO chunk. */
 	SCTP_CMD_CHUNK_ULP,	/* Send a chunk to the sockets layer.  */
 	SCTP_CMD_EVENT_ULP,	/* Send a notification to the sockets layer. */
 	SCTP_CMD_REPLY,		/* Send a chunk to our peer.  */
 	SCTP_CMD_SEND_PKT,	/* Send a full packet to our peer.  */
 	SCTP_CMD_RETRAN,	/* Mark a transport for retransmission.  */
 	SCTP_CMD_ECN_CE,        /* Do delayed CE processing.   */
 	SCTP_CMD_ECN_ECNE,	/* Do delayed ECNE processing. */
 	SCTP_CMD_ECN_CWR,	/* Do delayed CWR processing.  */
 	SCTP_CMD_TIMER_START,	/* Start a timer.  */
 	SCTP_CMD_TIMER_START_ONCE, /* Start a timer once */
 	SCTP_CMD_TIMER_RESTART,	/* Restart a timer. */
 	SCTP_CMD_TIMER_STOP,	/* Stop a timer. */
 	SCTP_CMD_INIT_CHOOSE_TRANSPORT, /* Choose transport for an INIT. */
 	SCTP_CMD_INIT_COUNTER_RESET, /* Reset init counter. */
 	SCTP_CMD_INIT_COUNTER_INC,   /* Increment init counter. */
 	SCTP_CMD_INIT_RESTART,  /* High level, do init timer work. */
 	SCTP_CMD_COOKIEECHO_RESTART,  /* High level, do cookie-echo timer work. */
 	SCTP_CMD_INIT_FAILED,   /* High level, do init failure work. */
 	SCTP_CMD_REPORT_DUP,	/* Report a duplicate TSN.  */
 	SCTP_CMD_STRIKE,	/* Mark a strike against a transport.  */
 	SCTP_CMD_HB_TIMERS_START,    /* Start the heartbeat timers. */
 	SCTP_CMD_HB_TIMER_UPDATE,    /* Update a heartbeat timers.  */
 	SCTP_CMD_HB_TIMERS_STOP,     /* Stop the heartbeat timers.  */
 	SCTP_CMD_PROBE_TIMER_UPDATE, /* Update a probe timer.  */
 	SCTP_CMD_TRANSPORT_HB_SENT,  /* Reset the status of a transport. */
 	SCTP_CMD_TRANSPORT_IDLE,     /* Do manipulations on idle transport */
 	SCTP_CMD_TRANSPORT_ON,       /* Mark the transport as active. */
 	SCTP_CMD_REPORT_ERROR,   /* Pass this error back out of the sm. */
 	SCTP_CMD_REPORT_BAD_TAG, /* Verification tags didn't match. */
 	SCTP_CMD_PROCESS_CTSN,   /* Sideeffect from shutdown. */
 	SCTP_CMD_ASSOC_FAILED,	 /* Handle association failure. */
 	SCTP_CMD_DISCARD_PACKET, /* Discard the whole packet. */
 	SCTP_CMD_GEN_SHUTDOWN,   /* Generate a SHUTDOWN chunk. */
 	SCTP_CMD_PURGE_OUTQUEUE, /* Purge all data waiting to be sent. */
 	SCTP_CMD_SETUP_T2,       /* Hi-level, setup T2-shutdown parms.  */
 	SCTP_CMD_RTO_PENDING,	 /* Set transport's rto_pending. */
 	SCTP_CMD_PART_DELIVER,	 /* Partial data delivery considerations. */
 	SCTP_CMD_RENEGE,         /* Renege data on an association. */
 	SCTP_CMD_SETUP_T4,	 /* ADDIP, setup T4 RTO timer parms. */
 	SCTP_CMD_PROCESS_OPERR,  /* Process an ERROR chunk. */
 	SCTP_CMD_REPORT_FWDTSN,	 /* Report new cumulative TSN Ack. */
 	SCTP_CMD_PROCESS_FWDTSN, /* Skips were reported, so process further. */
 	SCTP_CMD_CLEAR_INIT_TAG, /* Clears association peer's inittag. */
 	SCTP_CMD_DEL_NON_PRIMARY, /* Removes non-primary peer transports. */
 	SCTP_CMD_T3_RTX_TIMERS_STOP, /* Stops T3-rtx pending timers */
 	SCTP_CMD_FORCE_PRIM_RETRAN,  /* Forces retrans. over primary path. */
 	SCTP_CMD_SET_SK_ERR,	 /* Set sk_err */
 	SCTP_CMD_ASSOC_CHANGE,	 /* generate and send assoc_change event */
 	SCTP_CMD_ADAPTATION_IND, /* generate and send adaptation event */
 	SCTP_CMD_PEER_NO_AUTH,   /* generate and send authentication event */
 	SCTP_CMD_ASSOC_SHKEY,    /* generate the association shared keys */
 	SCTP_CMD_T1_RETRAN,	 /* Mark for retransmission after T1 timeout  */
 	SCTP_CMD_UPDATE_INITTAG, /* Update peer inittag */
 	SCTP_CMD_SEND_MSG,	 /* Send the whole use message */
 	SCTP_CMD_PURGE_ASCONF_QUEUE, /* Purge all asconf queues.*/
 	SCTP_CMD_SET_ASOC,	 /* Restore association context */
 	SCTP_CMD_LAST
 };

 /* How many commands can you put in an struct sctp_cmd_seq?
  * This is a rather arbitrary number, ideally derived from a careful
  * analysis of the state functions, but in reality just taken from
  * thin air in the hopes othat we don't trigger a kernel panic.
  */
 #define SCTP_MAX_NUM_COMMANDS 20

 union sctp_arg {
 	void *zero_all;	/* Set to NULL to clear the entire union */
 	__s32 i32;
 	__u32 u32;
 	__be32 be32;
 	__u16 u16;
 	__u8 u8;
 	int error;
 	__be16 err;
 	enum sctp_state state;
 	enum sctp_event_timeout to;
 	struct sctp_chunk *chunk;
 	struct sctp_association *asoc;
 	struct sctp_transport *transport;
 	struct sctp_bind_addr *bp;
 	struct sctp_init_chunk *init;
 	struct sctp_ulpevent *ulpevent;
 	struct sctp_packet *packet;
 	struct sctp_sackhdr *sackh;
 	struct sctp_datamsg *msg;
 };

 /* We are simulating ML type constructors here.
  *
  * SCTP_ARG_CONSTRUCTOR(NAME, TYPE, ELT) builds a function called
  * SCTP_NAME() which takes an argument of type TYPE and returns an
  * union sctp_arg.  It does this by inserting the sole argument into
  * the ELT union element of a local union sctp_arg.
  *
  * E.g., SCTP_ARG_CONSTRUCTOR(I32, __s32, i32) builds SCTP_I32(arg),
  * which takes an __s32 and returns a union sctp_arg containing the
  * __s32.  So, after foo = SCTP_I32(arg), foo.i32 == arg.
  */

 #define SCTP_ARG_CONSTRUCTOR(name, type, elt) \
 static inline union sctp_arg	\
 SCTP_## name (type arg)		\
 { union sctp_arg retval;\
   retval.zero_all = NULL;\
   retval.elt = arg;\
   return retval;\
 }

 SCTP_ARG_CONSTRUCTOR(I32,	__s32, i32)
 SCTP_ARG_CONSTRUCTOR(U32,	__u32, u32)
 SCTP_ARG_CONSTRUCTOR(BE32,	__be32, be32)
 SCTP_ARG_CONSTRUCTOR(U16,	__u16, u16)
 SCTP_ARG_CONSTRUCTOR(U8,	__u8, u8)
 SCTP_ARG_CONSTRUCTOR(ERROR,     int, error)
 SCTP_ARG_CONSTRUCTOR(PERR,      __be16, err)	/* protocol error */
 SCTP_ARG_CONSTRUCTOR(STATE,	enum sctp_state, state)
 SCTP_ARG_CONSTRUCTOR(TO,	enum sctp_event_timeout, to)
 SCTP_ARG_CONSTRUCTOR(CHUNK,	struct sctp_chunk *, chunk)
 SCTP_ARG_CONSTRUCTOR(ASOC,	struct sctp_association *, asoc)
 SCTP_ARG_CONSTRUCTOR(TRANSPORT,	struct sctp_transport *, transport)
 SCTP_ARG_CONSTRUCTOR(BA,	struct sctp_bind_addr *, bp)
 SCTP_ARG_CONSTRUCTOR(PEER_INIT,	struct sctp_init_chunk *, init)
 SCTP_ARG_CONSTRUCTOR(ULPEVENT,  struct sctp_ulpevent *, ulpevent)
 SCTP_ARG_CONSTRUCTOR(PACKET,	struct sctp_packet *, packet)
 SCTP_ARG_CONSTRUCTOR(SACKH,	struct sctp_sackhdr *, sackh)
 SCTP_ARG_CONSTRUCTOR(DATAMSG,	struct sctp_datamsg *, msg)

 static inline union sctp_arg SCTP_FORCE(void)
 {
 	return SCTP_I32(1);
 }

 static inline union sctp_arg SCTP_NOFORCE(void)
 {
 	return SCTP_I32(0);
 }

 static inline union sctp_arg SCTP_NULL(void)
 {
 	union sctp_arg retval;
 	retval.zero_all = NULL;
 	return retval;
 }

 struct sctp_cmd {
 	union sctp_arg obj;
 	enum sctp_verb verb;
 };

 struct sctp_cmd_seq {
 	struct sctp_cmd cmds[SCTP_MAX_NUM_COMMANDS];
 	struct sctp_cmd *last_used_slot;
 	struct sctp_cmd *next_cmd;
 };


 /* Initialize a block of memory as a command sequence.
  * Return 0 if the initialization fails.
  */
 static inline int sctp_init_cmd_seq(struct sctp_cmd_seq *seq)
 {
 	/* cmds[] is filled backwards to simplify the overflow BUG() check */
 	seq->last_used_slot = seq->cmds + SCTP_MAX_NUM_COMMANDS;
 	seq->next_cmd = seq->last_used_slot;
 	return 1;		/* We always succeed.  */
 }


 /* Add a command to an struct sctp_cmd_seq.
  *
  * Use the SCTP_* constructors defined by SCTP_ARG_CONSTRUCTOR() above
  * to wrap data which goes in the obj argument.
  */
 static inline void sctp_add_cmd_sf(struct sctp_cmd_seq *seq,
 				   enum sctp_verb verb, union sctp_arg obj)
 {
 	struct sctp_cmd *cmd = seq->last_used_slot - 1;

 	BUG_ON(cmd < seq->cmds);

 	cmd->verb = verb;
 	cmd->obj = obj;
 	seq->last_used_slot = cmd;
 }

 /* Return the next command structure in an sctp_cmd_seq.
  * Return NULL at the end of the sequence.
  */
 static inline struct sctp_cmd *sctp_next_cmd(struct sctp_cmd_seq *seq)
 {
 	if (seq->next_cmd <= seq->last_used_slot)
 		return NULL;

 	return --seq->next_cmd;
 }

 #endif /* __net_sctp_command_h__ */
	/* SPDX-License-Identifier: GPL-2.0-or-later */
	/* SCTP kernel Implementation
	* (C) Copyright IBM Corp. 2001, 2004
	* Copyright (C) 1999-2001 Cisco, Motorola
	*
	* This file is part of the SCTP kernel implementation
	*
	* These are the definitions needed for the command object.
	*
	* 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>
	* Karl Knutson <karl@athena.chicago.il.us>
	* Ardelle Fan <ardelle.fan@intel.com>
	* Sridhar Samudrala <sri@us.ibm.com>
	*/

	#ifndef __net_sctp_command_h__
	#define __net_sctp_command_h__

	#include <net/sctp/constants.h>
	#include <net/sctp/structs.h>


	enum sctp_verb {
	SCTP_CMD_NOP = 0, /* Do nothing. */
	SCTP_CMD_NEW_ASOC, /* Register a new association. */
	SCTP_CMD_DELETE_TCB, /* Delete the current association. */
	SCTP_CMD_NEW_STATE, /* Enter a new state. */
	SCTP_CMD_REPORT_TSN, /* Record the arrival of a TSN. */
	SCTP_CMD_GEN_SACK, /* Send a Selective ACK (maybe). */
	SCTP_CMD_PROCESS_SACK, /* Process an inbound SACK. */
	SCTP_CMD_GEN_INIT_ACK, /* Generate an INIT ACK chunk. */
	SCTP_CMD_PEER_INIT, /* Process a INIT from the peer. */
	SCTP_CMD_GEN_COOKIE_ECHO, /* Generate a COOKIE ECHO chunk. */
	SCTP_CMD_CHUNK_ULP, /* Send a chunk to the sockets layer. */
	SCTP_CMD_EVENT_ULP, /* Send a notification to the sockets layer. */
	SCTP_CMD_REPLY, /* Send a chunk to our peer. */
	SCTP_CMD_SEND_PKT, /* Send a full packet to our peer. */
	SCTP_CMD_RETRAN, /* Mark a transport for retransmission. */
	SCTP_CMD_ECN_CE, /* Do delayed CE processing. */
	SCTP_CMD_ECN_ECNE, /* Do delayed ECNE processing. */
	SCTP_CMD_ECN_CWR, /* Do delayed CWR processing. */
	SCTP_CMD_TIMER_START, /* Start a timer. */
	SCTP_CMD_TIMER_START_ONCE, /* Start a timer once */
	SCTP_CMD_TIMER_RESTART, /* Restart a timer. */
	SCTP_CMD_TIMER_STOP, /* Stop a timer. */
	SCTP_CMD_INIT_CHOOSE_TRANSPORT, /* Choose transport for an INIT. */
	SCTP_CMD_INIT_COUNTER_RESET, /* Reset init counter. */
	SCTP_CMD_INIT_COUNTER_INC, /* Increment init counter. */
	SCTP_CMD_INIT_RESTART, /* High level, do init timer work. */
	SCTP_CMD_COOKIEECHO_RESTART, /* High level, do cookie-echo timer work. */
	SCTP_CMD_INIT_FAILED, /* High level, do init failure work. */
	SCTP_CMD_REPORT_DUP, /* Report a duplicate TSN. */
	SCTP_CMD_STRIKE, /* Mark a strike against a transport. */
	SCTP_CMD_HB_TIMERS_START, /* Start the heartbeat timers. */
	SCTP_CMD_HB_TIMER_UPDATE, /* Update a heartbeat timers. */
	SCTP_CMD_HB_TIMERS_STOP, /* Stop the heartbeat timers. */
	SCTP_CMD_PROBE_TIMER_UPDATE, /* Update a probe timer. */
	SCTP_CMD_TRANSPORT_HB_SENT, /* Reset the status of a transport. */
	SCTP_CMD_TRANSPORT_IDLE, /* Do manipulations on idle transport */
	SCTP_CMD_TRANSPORT_ON, /* Mark the transport as active. */
	SCTP_CMD_REPORT_ERROR, /* Pass this error back out of the sm. */
	SCTP_CMD_REPORT_BAD_TAG, /* Verification tags didn't match. */
	SCTP_CMD_PROCESS_CTSN, /* Sideeffect from shutdown. */
	SCTP_CMD_ASSOC_FAILED, /* Handle association failure. */
	SCTP_CMD_DISCARD_PACKET, /* Discard the whole packet. */
	SCTP_CMD_GEN_SHUTDOWN, /* Generate a SHUTDOWN chunk. */
	SCTP_CMD_PURGE_OUTQUEUE, /* Purge all data waiting to be sent. */
	SCTP_CMD_SETUP_T2, /* Hi-level, setup T2-shutdown parms. */
	SCTP_CMD_RTO_PENDING, /* Set transport's rto_pending. */
	SCTP_CMD_PART_DELIVER, /* Partial data delivery considerations. */
	SCTP_CMD_RENEGE, /* Renege data on an association. */
	SCTP_CMD_SETUP_T4, /* ADDIP, setup T4 RTO timer parms. */
	SCTP_CMD_PROCESS_OPERR, /* Process an ERROR chunk. */
	SCTP_CMD_REPORT_FWDTSN, /* Report new cumulative TSN Ack. */
	SCTP_CMD_PROCESS_FWDTSN, /* Skips were reported, so process further. */
	SCTP_CMD_CLEAR_INIT_TAG, /* Clears association peer's inittag. */
	SCTP_CMD_DEL_NON_PRIMARY, /* Removes non-primary peer transports. */
	SCTP_CMD_T3_RTX_TIMERS_STOP, /* Stops T3-rtx pending timers */
	SCTP_CMD_FORCE_PRIM_RETRAN, /* Forces retrans. over primary path. */
	SCTP_CMD_SET_SK_ERR, /* Set sk_err */
	SCTP_CMD_ASSOC_CHANGE, /* generate and send assoc_change event */
	SCTP_CMD_ADAPTATION_IND, /* generate and send adaptation event */
	SCTP_CMD_PEER_NO_AUTH, /* generate and send authentication event */
	SCTP_CMD_ASSOC_SHKEY, /* generate the association shared keys */
	SCTP_CMD_T1_RETRAN, /* Mark for retransmission after T1 timeout */
	SCTP_CMD_UPDATE_INITTAG, /* Update peer inittag */
	SCTP_CMD_SEND_MSG, /* Send the whole use message */
	SCTP_CMD_PURGE_ASCONF_QUEUE, /* Purge all asconf queues.*/
	SCTP_CMD_SET_ASOC, /* Restore association context */
	SCTP_CMD_LAST
	};

	/* How many commands can you put in an struct sctp_cmd_seq?
	* This is a rather arbitrary number, ideally derived from a careful
	* analysis of the state functions, but in reality just taken from
	* thin air in the hopes othat we don't trigger a kernel panic.
	*/
	#define SCTP_MAX_NUM_COMMANDS 20

	union sctp_arg {
	void zero_all; / Set to NULL to clear the entire union */
	__s32 i32;
	__u32 u32;
	__be32 be32;
	__u16 u16;
	__u8 u8;
	int error;
	__be16 err;
	enum sctp_state state;
	enum sctp_event_timeout to;
	struct sctp_chunk *chunk;
	struct sctp_association *asoc;
	struct sctp_transport *transport;
	struct sctp_bind_addr *bp;
	struct sctp_init_chunk *init;
	struct sctp_ulpevent *ulpevent;
	struct sctp_packet *packet;
	struct sctp_sackhdr *sackh;
	struct sctp_datamsg *msg;
	};

	/* We are simulating ML type constructors here.
	*
	* SCTP_ARG_CONSTRUCTOR(NAME, TYPE, ELT) builds a function called
	* SCTP_NAME() which takes an argument of type TYPE and returns an
	* union sctp_arg. It does this by inserting the sole argument into
	* the ELT union element of a local union sctp_arg.
	*
	* E.g., SCTP_ARG_CONSTRUCTOR(I32, __s32, i32) builds SCTP_I32(arg),
	* which takes an __s32 and returns a union sctp_arg containing the
	* __s32. So, after foo = SCTP_I32(arg), foo.i32 == arg.
	*/

	#define SCTP_ARG_CONSTRUCTOR(name, type, elt) \
	static inline union sctp_arg \
	SCTP_## name (type arg) \
	{ union sctp_arg retval;\
	retval.zero_all = NULL;\
	retval.elt = arg;\
	return retval;\
	}

	SCTP_ARG_CONSTRUCTOR(I32, __s32, i32)
	SCTP_ARG_CONSTRUCTOR(U32, __u32, u32)
	SCTP_ARG_CONSTRUCTOR(BE32, __be32, be32)
	SCTP_ARG_CONSTRUCTOR(U16, __u16, u16)
	SCTP_ARG_CONSTRUCTOR(U8, __u8, u8)
	SCTP_ARG_CONSTRUCTOR(ERROR, int, error)
	SCTP_ARG_CONSTRUCTOR(PERR, __be16, err) /* protocol error */
	SCTP_ARG_CONSTRUCTOR(STATE, enum sctp_state, state)
	SCTP_ARG_CONSTRUCTOR(TO, enum sctp_event_timeout, to)
	SCTP_ARG_CONSTRUCTOR(CHUNK, struct sctp_chunk *, chunk)
	SCTP_ARG_CONSTRUCTOR(ASOC, struct sctp_association *, asoc)
	SCTP_ARG_CONSTRUCTOR(TRANSPORT, struct sctp_transport *, transport)
	SCTP_ARG_CONSTRUCTOR(BA, struct sctp_bind_addr *, bp)
	SCTP_ARG_CONSTRUCTOR(PEER_INIT, struct sctp_init_chunk *, init)
	SCTP_ARG_CONSTRUCTOR(ULPEVENT, struct sctp_ulpevent *, ulpevent)
	SCTP_ARG_CONSTRUCTOR(PACKET, struct sctp_packet *, packet)
	SCTP_ARG_CONSTRUCTOR(SACKH, struct sctp_sackhdr *, sackh)
	SCTP_ARG_CONSTRUCTOR(DATAMSG, struct sctp_datamsg *, msg)

	static inline union sctp_arg SCTP_FORCE(void)
	{
	return SCTP_I32(1);
	}

	static inline union sctp_arg SCTP_NOFORCE(void)
	{
	return SCTP_I32(0);
	}

	static inline union sctp_arg SCTP_NULL(void)
	{
	union sctp_arg retval;
	retval.zero_all = NULL;
	return retval;
	}

	struct sctp_cmd {
	union sctp_arg obj;
	enum sctp_verb verb;
	};

	struct sctp_cmd_seq {
	struct sctp_cmd cmds[SCTP_MAX_NUM_COMMANDS];
	struct sctp_cmd *last_used_slot;
	struct sctp_cmd *next_cmd;
	};


	/* Initialize a block of memory as a command sequence.
	* Return 0 if the initialization fails.
	*/
	static inline int sctp_init_cmd_seq(struct sctp_cmd_seq *seq)
	{
	/* cmds[] is filled backwards to simplify the overflow BUG() check */
	seq->last_used_slot = seq->cmds + SCTP_MAX_NUM_COMMANDS;
	seq->next_cmd = seq->last_used_slot;
	return 1; /* We always succeed. */
	}


	/* Add a command to an struct sctp_cmd_seq.
	*
	* Use the SCTP_* constructors defined by SCTP_ARG_CONSTRUCTOR() above
	* to wrap data which goes in the obj argument.
	*/
	static inline void sctp_add_cmd_sf(struct sctp_cmd_seq *seq,
	enum sctp_verb verb, union sctp_arg obj)
	{
	struct sctp_cmd *cmd = seq->last_used_slot - 1;

	BUG_ON(cmd < seq->cmds);

	cmd->verb = verb;
	cmd->obj = obj;
	seq->last_used_slot = cmd;
	}

	/* Return the next command structure in an sctp_cmd_seq.
	* Return NULL at the end of the sequence.
	*/
	static inline struct sctp_cmd sctp_next_cmd(struct sctp_cmd_seq seq)
	{
	if (seq->next_cmd <= seq->last_used_slot)
	return NULL;

	return --seq->next_cmd;
	}

	#endif /* __net_sctp_command_h__ */