The Tcpdump Group git mirrors - tcpdump/blob - missing/win_ether_ntohost.c

   1 /*
   2  * Redistribution and use in source and binary forms, with or without
   3  * modification, are permitted provided that: (1) source code distributions
   4  * retain the above copyright notice and this paragraph in its entirety, (2)
   5  * distributions including binary code include the above copyright notice and
   6  * this paragraph in its entirety in the documentation or other materials
   7  * provided with the distribution, and (3) all advertising materials mentioning
   8  * features or use of this software display the following acknowledgement:
   9  * ``This product includes software developed by the University of California,
  10  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
  11  * the University nor the names of its contributors may be used to endorse
  12  * or promote products derived from this software without specific prior
  13  * written permission.
  14  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
  15  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
  16  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  17  *
  18  * tcpdump/Win32 functions for reading and parsing system's Ethernet
  19  * address file:
  20  *    '%SystemRoot%/drivers/etc/ethers'  (Win-NT+)
  21  * or '%Windir%/etc/ethers'              (Win-9x/ME)
  22  *
  23  * G. Vanem <gvanem@yahoo.no> 2012.
  24  */
  25
  26 #ifdef HAVE_CONFIG_H
  27 #include <config.h>
  28 #endif
  29
  30 #include <netdissect-stdinc.h>
  31
  32 #include "missing/win_ether_ntohost.h"
  33
  34 #include "netdissect.h"
  35 #include "addrtoname.h"
  36
  37 typedef struct ether_entry {
  38         ether_address      eth_addr;  /* MAC address */
  39         char               *name;     /* name of MAC-address */
  40         struct ether_entry *next;
  41       } ether_entry;
  42
  43 static struct ether_entry *eth0 = NULL;
  44
  45 /*
  46  * The reason to avoid using 'pcap_next_etherent()' in addrtoname.c
  47  * are several:
  48  *   1) wpcap.dll and 'pcap_next_etherent()' could have been built in
  49  *      debug-mode (-MDd) or release-mode (-MD) and tcpdump in
  50  *      the opposite model.
  51  *   2) If this is built by MSVC, wpcap.dll could have been built by
  52  *      MingW. It has no debug-model.
  53  *   3) It may not have been exported from wpcap.dll (present in wpcap.def).
  54  *
  55  * So we shoe-horn the building of tcpdump with '-DUSE_ETHER_NTOHOST' to
  56  * make 'init_etherarray()' call the below 'ether_ntohost()' instead.
  57  */
  58 #if !defined(USE_ETHER_NTOHOST)
  59 #error "'-DUSE_ETHER_NTOHOST' must be set"
  60 #endif
  61
  62 /*
  63  * Return TRUE if running under Win-95/98/ME.
  64  */
  65 static BOOL is_win9x (void)
  66 {
  67   OSVERSIONINFO ovi;
  68   DWORD os_ver = GetVersion();
  69   DWORD major_ver = LOBYTE (LOWORD(os_ver));
  70
  71   return (os_ver >= 0x80000000 && major_ver >= 4);
  72 }
  73
  74 /*
  75  * Return path to "%SystemRoot%/drivers/etc/<file>"  (Win-NT+)
  76  *          or to "%Windir%/etc/<file>"              (Win-9x/ME)
  77  */
  78 const char *etc_path (const char *file)
  79 {
  80   BOOL win9x = is_win9x();
  81   const char *env = win9x ? getenv("WinDir") : getenv("SystemRoot");
  82   static char path[MAX_PATH];
  83
  84   if (!env)
  85     return (file);
  86
  87   if (win9x)
  88     snprintf (path, sizeof(path), "%s\\etc\\%s", env, file);
  89   else
  90     snprintf (path, sizeof(path), "%s\\system32\\drivers\\etc\\%s", env, file);
  91
  92   return (path);
  93 }
  94
  95 /*
  96  * Parse a string-buf containing an MAC address and name.
  97  * Accepts MAC addresses on both "xx:xx:xx.." and "xx-xx-xx.." forms.
  98  *
  99  * We could have used pcap_ether_aton(), but problem 3) above could apply.
 100  * or we could have cut & pasted 'pcap_next_etherent(FILE *fp)' below.
 101  */
 102 #define MIN_LEN  sizeof("0:0:0:0:0:0 X")
 103
 104 static
 105 int parse_ether_buf (const char *buf, char **result, struct ether_addr *e)
 106 {
 107   const char *fmt;
 108   char       *name;
 109   char       *str = (char*)buf;
 110   unsigned    eth [sizeof(*e)];
 111   int         i;
 112
 113   /* Find first non-blank in 'buf' */
 114   while (str[0] && str[1] && isspace((int)str[0]))
 115        str++;
 116
 117   if (*str == '#' || *str == ';' || *str == '\n' || strlen(str) < MIN_LEN)
 118      return (0);
 119
 120   if (str[2] == ':')
 121     fmt = "%02x:%02x:%02x:%02x:%02x:%02x";
 122   else
 123     fmt = "%02x-%02x-%02x-%02x-%02x-%02x";
 124
 125   if (sscanf(str, fmt, &eth[0], &eth[1], &eth[2], &eth[3], &eth[4], &eth[5]) != MAC_ADDR_LEN)
 126      return (0);
 127
 128   str  = strtok (str, " \t");
 129   name = strtok (NULL, " #\t\n");
 130
 131   if (!str || !name || strlen(name) < 1)
 132      return (0);
 133
 134   *result = name;
 135
 136   for (i = 0; i < MAC_ADDR_LEN; i++)
 137       e->octet[i] = eth[i];
 138
 139   return (1);
 140 }
 141
 142 static void free_ethers (void)
 143 {
 144   struct ether_entry *e, *next;
 145
 146   for (e = eth0; e; e = next) {
 147     next = e->next;
 148     free(e->name);
 149     free(e);
 150   }
 151   eth0 = NULL;
 152 }
 153
 154 static int init_ethers (void)
 155 {
 156   char  buf[BUFSIZE];
 157   FILE *fp = fopen (etc_path("ethers"), "r");
 158
 159   if (!fp)
 160      return (0);
 161
 162   while (fgets(buf,sizeof(buf),fp))
 163   {
 164     struct ether_entry *e;
 165     char  *name;
 166     ether_address eth;
 167
 168     if (!parse_ether_buf(buf,&name,&eth))
 169        continue;
 170
 171     e = calloc (sizeof(*e), 1);
 172     if (!e)
 173        break;
 174
 175     memcpy(&e->eth_addr, &eth, MAC_ADDR_LEN);
 176     e->name = strdup(name);
 177     if (!e->name) {
 178       free(e);
 179       break;
 180     }
 181
 182     e->next = eth0;
 183     eth0 = e;
 184   }
 185   fclose(fp);
 186   atexit(free_ethers);
 187   return (1);
 188 }
 189
 190 /*
 191  * Map an ethernet address 'e' to a 'name'.
 192  * Returns 0 on success.
 193  *
 194  * This function is called at startup by init_etherarray() and then
 195  * by etheraddr_string() as needed. To avoid doing an expensive fopen()
 196  * on each call, the contents of 'etc_path("ethers")' is cached here in
 197  * a linked-list 'eth0'.
 198  */
 199 int ether_ntohost (char *name, struct ether_addr *e)
 200 {
 201   const struct ether_entry *cache;
 202   static int init = 0;
 203
 204   if (!init) {
 205     init_ethers();
 206     init = 1;
 207   }
 208
 209   for (cache = eth0; cache; cache = cache->next)
 210      if (!memcmp(&e->octet, &cache->eth_addr, MAC_ADDR_LEN)) {
 211        strcpy (name,cache->name);
 212        return (0);
 213      }
 214   return (1);
 215 }
 216