The Tcpdump Group git mirrors - tcpdump/blob - win32/src/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 "ether.h"
  33 #include "interface.h"
  34 #include "addrtoname.h"
  35
  36 typedef struct ether_addr {
  37         unsigned char octet[ETHER_ADDR_LEN];
  38       } ether_address;
  39
  40 typedef struct ether_entry {
  41         ether_address      eth_addr;  /* MAC address */
  42         char               *name;     /* name of MAC-address */
  43         struct ether_entry *next;
  44       } ether_entry;
  45
  46 static struct ether_entry *eth0 = NULL;
  47
  48 /*
  49  * The reason to avoid using 'pcap_next_etherent()' in addrtoname.c
  50  * are several:
  51  *   1) wpcap.dll and 'pcap_next_etherent()' could have been built in
  52  *      debug-mode (-MDd) or release-mode (-MD) and tcpdump in
  53  *      the opposite model.
  54  *   2) If this is built by MSVC, wpcap.dll could have been built by
  55  *      MingW. It has no debug-model.
  56  *   3) It may not have been exported from wpcap.dll (present in wpcap.def).
  57  *
  58  * So we shoe-horn the building of tcpdump with '-DUSE_ETHER_NTOHOST' to
  59  * make 'init_etherarray()' call the below 'ether_ntohost()' instead.
  60  */
  61 #if !defined(USE_ETHER_NTOHOST)
  62 #error "'-DUSE_ETHER_NTOHOST' must be set"
  63 #endif
  64
  65 /*
  66  * Return TRUE if running under Win-95/98/ME.
  67  */
  68 static BOOL is_win9x (void)
  69 {
  70   OSVERSIONINFO ovi;
  71   DWORD os_ver = GetVersion();
  72   DWORD major_ver = LOBYTE (LOWORD(os_ver));
  73
  74   return (os_ver >= 0x80000000 && major_ver >= 4);
  75 }
  76
  77 /*
  78  * Return path to "%SystemRoot%/drivers/etc/<file>"  (Win-NT+)
  79  *          or to "%Windir%/etc/<file>"              (Win-9x/ME)
  80  */
  81 const char *etc_path (const char *file)
  82 {
  83   BOOL win9x = is_win9x();
  84   const char *env = win9x ? getenv("WinDir") : getenv("SystemRoot");
  85   static char path[MAX_PATH];
  86
  87   if (!env)
  88     return (file);
  89
  90   if (win9x)
  91     snprintf (path, sizeof(path), "%s\\etc\\%s", env, file);
  92   else
  93     snprintf (path, sizeof(path), "%s\\system32\\drivers\\etc\\%s", env, file);
  94
  95   return (path);
  96 }
  97
  98 /*
  99  * Parse a string-buf containing an MAC address and name.
 100  * Accepts MAC addresses on both "xx:xx:xx.." and "xx-xx-xx.." forms.
 101  *
 102  * We could have used pcap_ether_aton(), but problem 3) above could apply.
 103  * or we could have cut & pasted 'pcap_next_etherent(FILE *fp)' below.
 104  */
 105 #define MIN_LEN  sizeof("0:0:0:0:0:0 X")
 106
 107 static
 108 int parse_ether_buf (const char *buf, char **result, struct ether_addr *e)
 109 {
 110   const char *fmt;
 111   char       *name;
 112   char       *str = (char*)buf;
 113   unsigned    eth [sizeof(*e)];
 114   int         i;
 115
 116   /* Find first non-blank in 'buf' */
 117   while (str[0] && str[1] && isspace((int)str[0]))
 118        str++;
 119
 120   if (*str == '#' || *str == ';' || *str == '\n' || strlen(str) < MIN_LEN)
 121      return (0);
 122
 123   if (str[2] == ':')
 124     fmt = "%02x:%02x:%02x:%02x:%02x:%02x";
 125   else
 126     fmt = "%02x-%02x-%02x-%02x-%02x-%02x";
 127
 128   if (sscanf(str, fmt, &eth[0], &eth[1], &eth[2], &eth[3], &eth[4], &eth[5]) != ETHER_ADDR_LEN)
 129      return (0);
 130
 131   str  = strtok (str, " \t");
 132   name = strtok (NULL, " #\t\n");
 133
 134   if (!str || !name || strlen(name) < 1)
 135      return (0);
 136
 137   *result = name;
 138
 139   for (i = 0; i < ETHER_ADDR_LEN; i++)
 140       e->octet[i] = eth[i];
 141
 142   return (1);
 143 }
 144
 145 static void free_ethers (void)
 146 {
 147   struct ether_entry *e, *next;
 148
 149   for (e = eth0; e; e = next) {
 150     next = e->next;
 151     free(e->name);
 152     free(e);
 153   }
 154   eth0 = NULL;
 155 }
 156
 157 static int init_ethers (void)
 158 {
 159   char  buf[BUFSIZE];
 160   FILE *fp = fopen (etc_path("ethers"), "r");
 161
 162   if (!fp)
 163      return (0);
 164
 165   while (fgets(buf,sizeof(buf),fp))
 166   {
 167     struct ether_entry *e;
 168     char  *name;
 169     ether_address eth;
 170
 171     if (!parse_ether_buf(buf,&name,&eth))
 172        continue;
 173
 174     e = calloc (sizeof(*e), 1);
 175     if (!e)
 176        break;
 177
 178     memcpy(&e->eth_addr, &eth, ETHER_ADDR_LEN);
 179     e->name = strdup(name);
 180     if (!e->name) {
 181       free(e);
 182       break;
 183     }
 184
 185     e->next = eth0;
 186     eth0 = e;
 187   }
 188   fclose(fp);
 189   atexit(free_ethers);
 190   return (1);
 191 }
 192
 193 /*
 194  * Map an ethernet address 'e' to a 'name'.
 195  * Returns 0 on success.
 196  *
 197  * This function is called at startup by init_etherarray() and then
 198  * by etheraddr_string() as needed. To avoid doing an expensive fopen()
 199  * on each call, the contents of 'etc_path("ethers")' is cached here in
 200  * a linked-list 'eth0'.
 201  */
 202 int ether_ntohost (char *name, struct ether_addr *e)
 203 {
 204   const struct ether_entry *cache;
 205   static int init = 0;
 206
 207   if (!init) {
 208     init_ethers();
 209     init = 1;
 210   }
 211
 212   for (cache = eth0; cache; cache = cache->next)
 213      if (!memcmp(&e->octet, &cache->eth_addr, ETHER_ADDR_LEN)) {
 214        strcpy (name,cache->name);
 215        return (0);
 216      }
 217   return (1);
 218 }
 219