libc/inet/ethers.c

   1 /*
   2  * libc/inet/ethers.c
   3  *
   4  * Programmatic interface for the /etc/ethers file
   5  *
   6  * Copyright 2007 by Matthew Wilcox <matthew@wil.cx>
   7  *
   8  * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
   9  */
  10
  11 #include <ctype.h>
  12 #include <stdio.h>
  13 #include <string.h>
  14 #include <netinet/ether.h>
  15
  16 #define ETHER_LINE_LEN  256
  17
  18 /*
  19  * Internal function which returns a pointer to the part of the line
  20  * with the start of the hostname, or NULL if we couldn't parse the line.
  21  * Note that this line may have a comment symbol on it somewhere; if so
  22  * it will return NULL if the # is before or within the ether_addr, and
  23  * succeed if the # is before or within the host.  It's up to the callers
  24  * to be aware of this.
  25  *
  26  * I would have preferred to write a NUL to the location of the comment
  27  * character, but ether_line takes a const argument.  See __ether_line_w.
  28  */
  29 static const char *__ether_line(const char *line, struct ether_addr *addr)
  30 {
  31         struct ether_addr *res = ether_aton_r(line, addr);
  32         if (!res)
  33                 return NULL;
  34
  35         while (*line && (*line != ' ') && (*line != '\t'))
  36                 line++;
  37         while (*line && ((*line == ' ') || (*line == '\t')))
  38                 line++;
  39         return (*line) ? line : NULL;
  40 }
  41
  42 /*
  43  * Strips out the comment before calling __ether_line.  We can do this,
  44  * since we know the buffer is writable.
  45  */
  46 static const char *__ether_line_w(char *line, struct ether_addr *addr)
  47 {
  48         char *end = strchr(line, '#');
  49         if (!end)
  50                 end = strchr(line, '\n');
  51         if (end)
  52                 *end = '\0';
  53         return __ether_line(line, addr);
  54 }
  55
  56 int ether_line(const char *line, struct ether_addr *addr, char *hostname)
  57 {
  58         const char *name = __ether_line(line, addr);
  59         if (!name)
  60                 return -1;
  61
  62         while (*name) {
  63                 if ((*name == '#') || isspace(*name))
  64                         break;
  65                 *hostname++ = *name++;
  66         }
  67         *hostname = '\0';
  68
  69         return 0;
  70 }
  71
  72 int ether_ntohost(char *hostname, const struct ether_addr *addr)
  73 {
  74         int res = -1;
  75         FILE *fp;
  76         char buf[ETHER_LINE_LEN];
  77
  78         fp = fopen(ETHER_FILE_NAME, "r");
  79         if (!fp)
  80                 return -1;
  81
  82         while (fgets(buf, sizeof(buf), fp)) {
  83                 struct ether_addr tmp_addr;
  84                 const char *cp = __ether_line_w(buf, &tmp_addr);
  85                 if (!cp)
  86                         continue;
  87                 if (memcmp(addr, &tmp_addr, sizeof(tmp_addr)))
  88                         continue;
  89
  90                 strcpy(hostname, cp);
  91                 res = 0;
  92                 break;
  93         }
  94
  95         fclose(fp);
  96         return res;
  97 }
  98
  99 int ether_hostton(const char *hostname, struct ether_addr *addr)
 100 {
 101         int res = -1;
 102         FILE *fp;
 103         char buf[ETHER_LINE_LEN];
 104
 105         fp = fopen(ETHER_FILE_NAME, "r");
 106         if (!fp)
 107                 return -1;
 108
 109         while (fgets(buf, sizeof(buf), fp)) {
 110                 const char *cp = __ether_line_w(buf, addr);
 111                 if (!cp)
 112                         continue;
 113                 if (strcasecmp(hostname, cp))
 114                         continue;
 115
 116                 res = 0;
 117                 break;
 118         }
 119
 120         fclose(fp);
 121         return res;
 122 }