This patch implements a modification of TCP on SunOS 4.1.3 to support
cleaning up TIME_WAIT state at active close side. 

Copyright (c) 1997 University of Southern California.
All rights reserved.                                           
								 
Redistribution and use in source and binary forms are permitted
provided that the above copyright notice and this paragraph are
duplicated in all such forms and that any documentation, advertising
materials, and other materials related to such distribution and use
acknowledge that the software was developed by the University of
Southern California, Information Sciences Institute.  The name of the
University may not be used to endorse or promote products derived from
this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.


--------------------------------------------------------------------------------
*** tcp.h.orig	Wed Jun 16 12:13:51 1993
--- tcp.h	Wed Apr 30 14:21:42 1997
***************
*** 60,63 ****
--- 60,67 ----
  #define	TCP_NODELAY	0x01	/* don't delay send to coalesce packets */
  #define	TCP_MAXSEG	0x02	/* set maximum segment size */
  
+ #ifdef PCBSWAP
+ #define	TCP_PCBSWAP	0x04	/* swap pcbs on passive close */
+ #endif
+ 
  #endif /*!_netinet_tcp_h*/
*** tcp_subr.c.orig	Wed Jun 16 12:13:52 1993
--- tcp_subr.c	Wed Apr 30 14:37:44 1997
***************
*** 210,215 ****
--- 210,233 ----
  	return (tcp_close(tp));
  }
  
+ #ifdef PCBSWAP
+ /*
+  * Send an RST to the other side of the connection
+  * this is tcp_drop without the closing the socket, it's called from
+  * tcp_close() if PCBSWAP is in effect, the current connection is in
+  * LAST_ACK, has TF_PCBSWAP set and gets an ACK.  See tcp_close()
+  */
+ void tcp_swaprst(tp)
+ 	register struct tcpcb *tp;
+ {
+ 	struct socket *so = tp->t_inpcb->inp_socket;
+ 
+ 	tp->t_state = TCPS_CLOSED;
+ 	(void) tcp_output(tp);
+ 	tcpstat.tcps_drops++;
+ }
+ #endif 
+ 
  /* 
   * We need to clear the tcp_last_inp cache in tcp_input
   * when a connection finally goes away.
***************
*** 231,236 ****
--- 249,265 ----
  	struct socket *so = inp->inp_socket;
  	register struct mbuf *m;
  
+ #ifdef PCBSWAP
+ 	if ( tp->t_state == TCPS_LAST_ACK && tp->t_flags & TF_PCBSWAP ) {
+ 		/* Send a RST packet to the other side and move this
+ 		   connection to TIME_WAIT */
+ 		tcp_swaprst(tp);
+ 		tp->t_state = TCPS_TIME_WAIT;
+ 		tcp_canceltimers(tp);
+ 		tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
+ 		return ((struct tcpcb *)0);
+ 	}
+ #endif
  	t = tp->seg_next;
  	while (t != (struct tcpiphdr *)tp) {
  		t = (struct tcpiphdr *)t->ti_next;
*** tcp_usrreq.c.orig	Wed Jun 16 12:13:52 1993
--- tcp_usrreq.c	Thu May  1 21:17:20 1997
***************
*** 383,388 ****
--- 383,399 ----
  				tp->t_flags &= ~TF_NODELAY;
  			break;
  
+ #ifdef PCBSWAP
+ 		case TCP_PCBSWAP:
+ 			if (m == NULL || m->m_len < sizeof (int))
+ 				error = EINVAL;
+ 			else if (*mtod(m, int *))
+ 				tp->t_flags |= TF_PCBSWAP;
+ 			else
+ 				tp->t_flags &= ~TF_PCBSWAP;
+ 			break;
+ #endif
+ 
  		case TCP_MAXSEG:	/* not yet */
  		default:
  			error = EINVAL;
***************
*** 400,405 ****
--- 411,421 ----
  		case TCP_NODELAY:
  			*mtod(m, int *) = tp->t_flags & TF_NODELAY;
  			break;
+ #ifdef PCBSWAP
+ 		case TCP_PCBSWAP:
+ 			*mtod(m, int *) = tp->t_flags & TF_PCBSWAP;
+ 			break;
+ #endif
  		case TCP_MAXSEG:
  			*mtod(m, int *) = tp->t_maxseg;
  			break;
*** tcp_var.h.orig	Wed Jun 16 12:13:52 1993
--- tcp_var.h	Thu May  1 21:10:13 1997
***************
*** 32,37 ****
--- 32,42 ----
  #define	TF_NODELAY	0x04		/* don't delay packets to coalesce */
  #define	TF_NOOPT	0x08		/* don't use tcp options */
  #define	TF_SENTFIN	0x10		/* have sent FIN */
+ #ifdef PCBSWAP
+ 					/* High number so that fat pipe
+ 					   stuff fits -- tvf */
+ #define TF_PCBSWAP	0x20		/* Swap PCBs on passive close -- tvf */
+ #endif
  	struct	tcpiphdr *t_template;	/* skeletal packet for transmit */
  	struct	inpcb *t_inpcb;		/* back pointer to internet pcb */
  /*