lib/ip/gethostent.c

   1 /*      gethostent() - Interface to /etc/hosts          Author: Kees J. Bot
   2  *                                                              31 May 1999
   3  */
   4
   5 /* Prefix the functions defined here with underscores to distinguish them
   6  * from the newer replacements in the resolver library.
   7  */
   8 #define sethostent      _sethostent
   9 #define endhostent      _endhostent
  10 #define gethostent      _gethostent
  11 #define gethostbyname   _gethostbyname
  12 #define gethostbyaddr   _gethostbyaddr
  13
  14 #define nil 0
  15 #include <sys/types.h>
  16 #include <stdio.h>
  17 #include <string.h>
  18 #include <net/gen/netdb.h>
  19 #include <net/gen/in.h>
  20 #include <net/gen/inet.h>
  21 #include <net/gen/socket.h>
  22
  23 #define arraysize(a)    (sizeof(a) / sizeof((a)[0]))
  24 #define arraylimit(a)   ((a) + arraysize(a))
  25 #define isspace(c)      ((unsigned) (c) <= ' ')
  26
  27 static char HOSTS[]= _PATH_HOSTS;
  28 static char *hosts= HOSTS;      /* Current hosts file. */
  29 static FILE *hfp;               /* Open hosts file. */
  30
  31 void sethostent(int stayopen)
  32 /* Start search.  (Same as ending it.) */
  33 {
  34     endhostent();
  35 }
  36
  37 void endhostent(void)
  38 /* End search and reinitialize. */
  39 {
  40     if (hfp != nil) {
  41         fclose(hfp);
  42         hfp= nil;
  43     }
  44     hosts= _PATH_HOSTS;
  45 }
  46
  47 struct hostent *gethostent(void)
  48 /* Return the next entry from the hosts files. */
  49 {
  50     static char line[256];      /* One line in a hosts file. */
  51     static ipaddr_t addr;       /* IP address found first on the line. */
  52     static char *names[16];     /* Pointers to the words on the line. */
  53     static char *addrs[2]= {    /* List of IP addresses (just one.) */
  54         (char *) &addr,
  55         nil,
  56     };
  57     static struct hostent host = {
  58         nil,                    /* h_name, will set to names[1]. */
  59         names + 2,              /* h_aliases, the rest of the names. */
  60         AF_INET,                /* h_addrtype */
  61         sizeof(ipaddr_t),       /* Size of an address in the address list. */
  62         addrs,                  /* List of IP addresses. */
  63     };
  64     static char nexthosts[128]; /* Next hosts file to include. */
  65     char *lp, **np;
  66     int c;
  67
  68     for (;;) {
  69         if (hfp == nil) {
  70             /* No hosts file open, try to open the next one. */
  71             if (hosts == 0) return nil;
  72             if ((hfp= fopen(hosts, "r")) == nil) { hosts= nil; continue; }
  73         }
  74
  75         /* Read a line. */
  76         lp= line;
  77         while ((c= getc(hfp)) != EOF && c != '\n') {
  78             if (lp < arraylimit(line)) *lp++= c;
  79         }
  80
  81         /* EOF?  Then close and prepare for reading the next file. */
  82         if (c == EOF) {
  83             fclose(hfp);
  84             hfp= nil;
  85             hosts= nil;
  86             continue;
  87         }
  88
  89         if (lp == arraylimit(line)) continue;
  90         *lp= 0;
  91
  92         /* Break the line up in words. */
  93         np= names;
  94         lp= line;
  95         for (;;) {
  96             while (isspace(*lp) && *lp != 0) lp++;
  97             if (*lp == 0 || *lp == '#') break;
  98             if (np == arraylimit(names)) break;
  99             *np++= lp;
 100             while (!isspace(*lp) && *lp != 0) lp++;
 101             if (*lp == 0) break;
 102             *lp++= 0;
 103         }
 104
 105         if (np == arraylimit(names)) continue;
 106         *np= nil;
 107
 108         /* Special "include file" directive. */
 109         if (np == names + 2 && strcmp(names[0], "include") == 0) {
 110             fclose(hfp);
 111             hfp= nil;
 112             hosts= nil;
 113             if (strlen(names[1]) < sizeof(nexthosts)) {
 114                 strcpy(nexthosts, names[1]);
 115                 hosts= nexthosts;
 116             }
 117             continue;
 118         }
 119
 120         /* At least two words, the first of which is an IP address. */
 121         if (np < names + 2) continue;
 122         if (!inet_aton((char *) names[0], &addr)) continue;
 123         host.h_name= (char *) names[1];
 124
 125         return &host;
 126     }
 127 }
 128
 129 /* Rest kept in reserve, we probably never need 'em. */
 130 #if XXX
 131 struct hostent *gethostbyname(const char *name)
 132 {
 133     struct hostent *he;
 134     char **pa;
 135     char alias[256];
 136     char *domain;
 137
 138     sethostent(0);
 139     while ((he= gethostent()) != nil) {
 140         if (strcasecmp(he->h_name, name) == 0) goto found;
 141
 142         domain= strchr(he->h_name, '.');
 143         for (pa= he->h_aliases; *pa != nil; pa++) {
 144             strcpy(alias, *pa);
 145             if (domain != nil && strchr(alias, '.') == nil) {
 146                 strcat(alias, domain);
 147             }
 148             if (strcasecmp(alias, name) == 0) goto found;
 149         }
 150     }
 151   found:
 152     endhostent();
 153     return he;
 154 }
 155
 156 struct hostent *gethostbyaddr(const char *addr, int len, int type)
 157 {
 158     struct hostent *he;
 159
 160     sethostent(0);
 161     while ((he= gethostent()) != nil) {
 162         if (he->h_name[0] == '%') continue;
 163         if (type == AF_INET && memcmp(he->h_addr, addr, len) == 0) break;
 164     }
 165     endhostent();
 166     return he;
 167 }
 168 #endif