src/hostsreader.c

   1 #include <stdio.h>
   2 #include <ctype.h>
   3 #include <string.h>
   4 #include "common.h"
   5
   6 /*
   7    simple reader for /etc/hosts
   8    it only supports comments, blank lines and lines consisting of an ipv4 hostname pair.
   9    this is required so we can return entries from the host db without messing up the
  10    non-thread-safe state of libc's gethostent().
  11
  12 */
  13
  14 struct hostsreader {
  15         FILE *f;
  16         char* ip, *name;
  17 };
  18
  19 int hostsreader_open(struct hostsreader *ctx) {
  20         if(!(ctx->f = fopen("/etc/hosts", "r"))) return 0;
  21         return 1;
  22 }
  23
  24 void hostsreader_close(struct hostsreader *ctx) {
  25         fclose(ctx->f);
  26 }
  27
  28 int hostsreader_get(struct hostsreader *ctx, char* buf, size_t bufsize) {
  29         while(1) {
  30                 if(!fgets(buf, bufsize, ctx->f)) return 0;
  31                 if(*buf == '#') continue;
  32                 char *p = buf;
  33                 size_t l = bufsize;
  34                 ctx->ip = p;
  35                 while(*p && !isspace(*p) && l) {
  36                         p++;
  37                         l--;
  38                 }
  39                 if(!l || !*p || p == ctx->ip) continue;
  40                 *p = 0;
  41                 p++;
  42                 while(*p && isspace(*p) && l) {
  43                         p++;
  44                         l--;
  45                 }
  46                 if(!l || !*p) continue;
  47                 ctx->name = p;
  48                 while(*p && !isspace(*p) && l) {
  49                         p++;
  50                         l--;
  51                 }
  52                 if(!l || !*p) continue;
  53                 *p = 0;
  54                 if(pc_isnumericipv4(ctx->ip)) return 1;
  55         }
  56 }
  57
  58 char* hostsreader_get_ip_for_name(const char* name, char* buf, size_t bufsize) {
  59         struct hostsreader ctx;
  60         char *res = 0;
  61         if(!hostsreader_open(&ctx)) return 0;
  62         while(hostsreader_get(&ctx, buf, bufsize)) {
  63                 if(!strcmp(ctx.name, name)) {
  64                         res = ctx.ip;
  65                         break;
  66                 }
  67         }
  68         hostsreader_close(&ctx);
  69         return res;
  70 }
  71
  72 #include "ip_type.h"
  73 #include <netinet/in.h>
  74 #include <sys/socket.h>
  75 #include <arpa/inet.h>
  76 ip_type4 hostsreader_get_numeric_ip_for_name(const char* name) {
  77         char *hres;
  78         char buf[320];
  79         if((hres = hostsreader_get_ip_for_name(name, buf, sizeof buf))) {
  80                 struct in_addr c;
  81                 inet_aton(hres, &c);
  82                 ip_type4 res;
  83                 memcpy(res.octet, &c.s_addr, 4);
  84                 return res;
  85         } else return IPT4_INVALID;
  86 }
  87
  88 #ifdef HOSTSREADER_TEST
  89 #include "ip_type.c"
  90 int main(int a, char**b) {
  91         char buf[256];
  92         if(a != 2) return 1;
  93         char * ret = hostsreader_get_ip_for_name(b[1], buf, sizeof buf);
  94         printf("%s\n", ret ? ret : "null");
  95 }
  96 #endif