zebra/mtu_kvm.c

   1 /* MTU get using kvm_read.
   2  * Copyright (C) 1999 Kunihiro Ishiguro
   3  *
   4  * This file is part of GNU Zebra.
   5  *
   6  * GNU Zebra is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by the
   8  * Free Software Foundation; either version 2, or (at your option) any
   9  * later version.
  10  *
  11  * GNU Zebra is distributed in the hope that it will be useful, but
  12  * WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with GNU Zebra; see the file COPYING.  If not, write to the Free
  18  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  19  * 02111-1307, USA.
  20  */
  21
  22 #include <zebra.h>
  23
  24 #include <kvm.h>
  25 #include <limits.h>
  26 #include <fcntl.h>
  27
  28 #include "if.h"
  29
  30 /* get interface MTU to use kvm_read */
  31 void
  32 if_kvm_get_mtu (struct interface *ifp)
  33 {
  34   kvm_t *kvmd;
  35   struct ifnet ifnet;
  36   unsigned long ifnetaddr;
  37   int len;
  38
  39   char ifname[IFNAMSIZ];
  40   char tname[INTERFACE_NAMSIZ + 1];
  41   char buf[_POSIX2_LINE_MAX];
  42
  43   struct nlist nl[] =
  44   {
  45     {"_ifnet"},
  46     {""}
  47   };
  48
  49   ifp->mtu = -1;
  50
  51   kvmd = kvm_openfiles (NULL, NULL, NULL, O_RDONLY, buf);
  52
  53   if (kvmd == NULL)
  54     return ;
  55
  56   kvm_nlist(kvmd, nl);
  57
  58   ifnetaddr = nl[0].n_value;
  59
  60   if (kvm_read(kvmd, ifnetaddr, (char *)&ifnetaddr, sizeof ifnetaddr) < 0)
  61     {
  62       kvm_close (kvmd);
  63       return ;
  64     }
  65
  66   while(ifnetaddr != 0)
  67     {
  68       if (kvm_read (kvmd, ifnetaddr, (char *)&ifnet, sizeof ifnet) < 0)
  69         {
  70           kvm_close (kvmd);
  71           return ;
  72         }
  73
  74       if (kvm_read (kvmd, (u_long)ifnet.if_name, ifname, IFNAMSIZ) < 0)
  75         {
  76           kvm_close (kvmd);
  77           return ;
  78         }
  79
  80       len = snprintf (tname, INTERFACE_NAMSIZ + 1,
  81                       "%s%d", ifname, ifnet.if_unit);
  82
  83       if (strncmp (tname, ifp->name, len) == 0)
  84         break;
  85
  86       ifnetaddr = (u_long)ifnet.if_next;
  87     }
  88
  89   kvm_close (kvmd);
  90
  91   if (ifnetaddr == 0)
  92     {
  93       return ;
  94     }
  95
  96   ifp->mtu = ifnet.if_mtu;
  97 }