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Subject: kern/7230: problem with SIOCGIFCONF
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>Number:         7230
>Category:       kern
>Synopsis:       problem with SIOCGIFCONF
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:
>Keywords:
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Jul  9 16:10:01 PDT 1998
>Last-Modified:
>Originator:     Robert Cousus
>Organization:
>Release:        FreeBSD 2.2.6-RELEASE i386
>Environment:

	K6 cpu, 128 megs RAM, 15 gigs Disk, 2 LAN ifces.

>Description:

	SIOCGIFCONF does not return an array of struct ifreq with one
	entry per network interface.

>How-To-Repeat:

	Compile and run the attached program to demonstrate the problem.
        (Note: program runs correctly under Solaris 2.5.1.)
-----------------
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <net/if.h>
#include <sys/ioctl.h>

char buffer[1<<12];

int main(int argc, char *argv[])
{
  int res;			/* result from call */
  int sock;			/* socket file descriptor */
  int i;			/* loop variable */
  struct ifconf ifconf;		/* used in test below */
  struct ifreq *ptr;		/* pointer to walk buffer */

  sock = socket(PF_INET, SOCK_DGRAM, 0);
  if (sock < 0) {
    perror("socket(PF_INET, SOCK_DGRAM, 0)");
    exit(1);
  }

  ifconf.ifc_len = sizeof(buffer); /* establish size of buffer */
  ifconf.ifc_buf = buffer;	/* point to buffer */

  res = ioctl(sock, SIOCGIFCONF, &ifconf);
  if (res < 0) {
    perror("ioctl(sock, SIOCGIFCONF, &ifconf)");
    exit(1);
  }

  /* 
   * At this point, the ifconf.ifc_len should tell how many bytes consumed
   * in the buffer and ifconf.ifc_req should point to an array of ifreq
   * structures.
   *

   /*
    * Test 1: The return value should be a multiple of sizeof(ifreq).
    */

  if (ifconf.ifc_len % sizeof(struct ifreq)) {
    printf("Failed test1: %d %% %d = %d\n",
	   ifconf.ifc_len, sizeof(struct ifreq),
	   ifconf.ifc_len % sizeof(struct ifreq));
  }

  /*
   * Test 2: We should be able to print out the names of all
   * interfaces by looping through the array.
   */

   ptr = ifconf.ifc_req;	/* point to beginning of array */
   for (i = 0; i < (ifconf.ifc_len/sizeof(struct ifreq)); i++, ptr++)
     printf("Interface %d: %s\n", i, ptr->ifr_name);

   exit(0);
}
-----------------
>Fix:
	
	Unknown.

>Audit-Trail:
>Unformatted:
Robert Cousins

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