resolvconf.c raw

   1  #include "lookup.h"
   2  #include "stdio_impl.h"
   3  #include <ctype.h>
   4  #include <errno.h>
   5  #include <string.h>
   6  #include <stdlib.h>
   7  #include <netinet/in.h>
   8  
   9  int __get_resolv_conf(struct resolvconf *conf, char *search, size_t search_sz)
  10  {
  11  	char line[256];
  12  	unsigned char _buf[256];
  13  	FILE *f, _f;
  14  	int nns = 0;
  15  
  16  	conf->ndots = 1;
  17  	conf->timeout = 5;
  18  	conf->attempts = 2;
  19  	if (search) *search = 0;
  20  
  21  	f = __fopen_rb_ca("/etc/resolv.conf", &_f, _buf, sizeof _buf);
  22  	if (!f) switch (errno) {
  23  	case ENOENT:
  24  	case ENOTDIR:
  25  	case EACCES:
  26  		goto no_resolv_conf;
  27  	default:
  28  		return -1;
  29  	}
  30  
  31  	while (fgets(line, sizeof line, f)) {
  32  		char *p, *z;
  33  		if (!strchr(line, '\n') && !feof(f)) {
  34  			/* Ignore lines that get truncated rather than
  35  			 * potentially misinterpreting them. */
  36  			int c;
  37  			do c = getc(f);
  38  			while (c != '\n' && c != EOF);
  39  			continue;
  40  		}
  41  		if (!strncmp(line, "options", 7) && isspace(line[7])) {
  42  			p = strstr(line, "ndots:");
  43  			if (p && isdigit(p[6])) {
  44  				p += 6;
  45  				unsigned long x = strtoul(p, &z, 10);
  46  				if (z != p) conf->ndots = x > 15 ? 15 : x;
  47  			}
  48  			p = strstr(line, "attempts:");
  49  			if (p && isdigit(p[9])) {
  50  				p += 9;
  51  				unsigned long x = strtoul(p, &z, 10);
  52  				if (z != p) conf->attempts = x > 10 ? 10 : x;
  53  			}
  54  			p = strstr(line, "timeout:");
  55  			if (p && (isdigit(p[8]) || p[8]=='.')) {
  56  				p += 8;
  57  				unsigned long x = strtoul(p, &z, 10);
  58  				if (z != p) conf->timeout = x > 60 ? 60 : x;
  59  			}
  60  			continue;
  61  		}
  62  		if (!strncmp(line, "nameserver", 10) && isspace(line[10])) {
  63  			if (nns >= MAXNS) continue;
  64  			for (p=line+11; isspace(*p); p++);
  65  			for (z=p; *z && !isspace(*z); z++);
  66  			*z=0;
  67  			if (__lookup_ipliteral(conf->ns+nns, p, AF_UNSPEC) > 0)
  68  				nns++;
  69  			continue;
  70  		}
  71  
  72  		if (!search) continue;
  73  		if ((strncmp(line, "domain", 6) && strncmp(line, "search", 6))
  74  		    || !isspace(line[6]))
  75  			continue;
  76  		for (p=line+7; isspace(*p); p++);
  77  		size_t l = strlen(p);
  78  		/* This can never happen anyway with chosen buffer sizes. */
  79  		if (l >= search_sz) continue;
  80  		memcpy(search, p, l+1);
  81  	}
  82  
  83  	__fclose_ca(f);
  84  
  85  no_resolv_conf:
  86  	if (!nns) {
  87  		__lookup_ipliteral(conf->ns, "127.0.0.1", AF_UNSPEC);
  88  		nns = 1;
  89  	}
  90  
  91  	conf->nns = nns;
  92  
  93  	return 0;
  94  }
  95