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