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From: ambar@bloom-beacon.UUCP
Newsgroups: comp.unix.wizards
Subject: Re: Sockets stuck in FIN_WAIT_2
Message-ID: <910@bloom-beacon.MIT.EDU>
Date: Sat, 13-Jun-87 18:12:16 EDT
Article-I.D.: bloom-be.910
Posted: Sat Jun 13 18:12:16 1987
Date-Received: Sun, 14-Jun-87 03:52:56 EDT
References: <1556@aw.sei.cmu.edu>
Sender: daemon@bloom-beacon.MIT.EDU
Reply-To: ambar@athena.mit.edu (Jean Marie Diaz)
Organization: Madhouse International Technologies
Lines: 128
Summary: here's a program

In article <1556@aw.sei.cmu.edu> pdb@sei.cmu.edu (Patrick Barron) writes:
>
>If I shutdown sendmail on my Ultrix VAX and there is still a socket out there
>bound to the local smtp service in FIN_WAIT_2 (waiting for a FIN from the
>remote host), then I'll never be able to restart mail unless I reboot the
>machine.  Does anyone have a program, or the proper "adb -k" incantations,
>to force a stuck FIN_WAIT_2 socket into CLOSED state?

fixfin2 was written by our local network wizard, Jeff Schiller.  He
makes it available via anonymous ftp from bitsy.mit.edu, so posting it
isn't a problem.  It works on 4.[23]BSD, and Ultrix.  However, it
assumes that your header files match your kernel.  Be careful.  (and
don't forget to nuke the .signature at the end..)

#include <stdio.h>
#include "/sys/h/types.h"
#include "/sys/h/file.h"
#include "/sys/h/param.h"
#include "/sys/h/socket.h"
#include "/sys/h/socketvar.h"
#include "/sys/h/mbuf.h"
#include "/sys/h/protosw.h"
#include "/sys/netinet/in.h"
#include "/sys/netinet/in_systm.h"
#include "/sys/net/route.h"
#include "/sys/netinet/in_pcb.h"
#include "/sys/netinet/ip.h"
#include "/sys/netinet/tcp.h"
#include "/sys/netinet/tcp_fsm.h"
#include "/sys/netinet/tcp_timer.h"
#include "/sys/netinet/tcp_var.h"
#include <nlist.h>
extern   int errno;
struct inpcb inpcb;
struct tcpcb tcpcb;
int kmem;
struct nlist nl[] = {
#define N_TCB 0
  { "_tcb" }, 
  "",
};
main ()
{
  register int err;
  register struct inpcb *next, *prev;
  register int stateoff;
  struct inpcb *tcbaddr;
  int testfirst;
  short fstate;
  stateoff = 0;
  nlist("/vmunix", nl);
  if (nl[0].n_type == 0) {
    fprintf(stderr, "/vmunix: no namelist\n");
    exit (1);
  }
  tcbaddr = (struct inpcb *) nl[N_TCB].n_value;
  kmem = open ("/dev/kmem", O_RDWR, 0644);
  check_error(kmem, "Opening /dev/kmem", errno);
  (void) lseek (kmem, (off_t)tcbaddr, 0);
  check_error((errno != 0) ? -1 : 0, "seeking for tcbaddr", errno);
  err = read (kmem, (caddr_t)&inpcb, sizeof (struct inpcb));
  check_error(err, "reading tcb", errno);
  if (inpcb.inp_next == (struct inpcb *)tcbaddr) exit (3);
  prev = tcbaddr;
  while (inpcb.inp_next != (struct inpcb *)tcbaddr) {
    next = inpcb.inp_next;
    (void) lseek (kmem, (off_t)next, 0);
    check_error((errno != 0) ? -1 : 0, "seeking for next inpcb", errno);
    err = read(kmem, (char *)&inpcb, sizeof(inpcb));
    check_error(err, "reading next inpcb", errno);
    if (inpcb.inp_prev != prev) {
      fprintf(stderr,"Bad sample after %x\n", prev);
      exit (4);
    }
    (void) lseek(kmem, (off_t)inpcb.inp_ppcb, 0);
    check_error((errno != 0) ? -1 : 0, "Seeking tcpcb", errno);
    err = read (kmem, (char *)&tcpcb, sizeof(tcpcb));
    check_error(err, "Reading tcpcb", errno);
    if (stateoff == 0) {
      stateoff = (int) &tcpcb.t_state - (int) &tcpcb;
    }
    if (tcpcb.t_state == TCPS_FIN_WAIT_2) {
      testfirst = 1;
    doitagain:
      (void) lseek (kmem, (off_t) ((int) inpcb.inp_ppcb + stateoff), 0);
      check_error ((errno != 0) ? -1 : 0, "seeking to tcp state variable", errno);
      if (testfirst) {
	err = read (kmem, (char *)&fstate, sizeof (short));
      } else {
/*	fprintf(stderr, "Would write %d, &tcpcb = %X, stateoff= %d\n",
		fstate, inpcb.inp_ppcb, stateoff); */
	err = write (kmem, (char *)&fstate, sizeof (short));
      }
      check_error (err, testfirst ? "reading tcp state variable" :
		   "Writing tcp state variable", errno);
      if (testfirst) {
	if (fstate != TCPS_FIN_WAIT_2) {
	  fprintf(stderr, "Connection changed state!\n");
	} else {
	  testfirst = 0;
	  fstate = 0;
	}
	goto doitagain;
      }
    }
    prev = next;
  }
  (void) close (kmem);
  exit (0);
}

check_error(err, msg, code)
int err;
char *msg;
int code;
{
  if (err < 0) {
    fprintf (stderr, "finfix2: Error: %s\n", msg);
    errno = code;
    perror("fixfin2");
    exit (1);
  }
  return;
}


				AMBAR
ARPA: ambar@eddie.mit.edu		UUCP: {backbones}!mit-eddie!ambar