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#include <unistd.h>
#include "byte.h"
#include "dnsresolv.h"
#include "env.h"
#include "readclose.h"
#include "str.h"
#include "taia.h"
/**
@file dns_rcrw.c
@author djb
@ref ucspi-tcp
@brief DNS receive rewrite
*/
static stralloc data = {0};
static int init(stralloc *rules)
{
char host[256];
const char *x;
int i;
int j;
int k;
if (!stralloc_copys(rules, "")) return DNS_MEM;
x = env_get("DNSREWRITEFILE");
if (!x) x = "/etc/dnsrewrite";
i = openreadclose(x, &data, 64);
if (i == -1) return DNS_INT;
if (i) {
if (!stralloc_append(&data, "\n")) return DNS_MEM;
i = 0;
for (j = 0; j < data.len; ++j)
if (data.s[j] == '\n') {
if (!stralloc_catb(rules, data.s + i, j - i)) return DNS_MEM;
while (rules->len) {
if (rules->s[rules->len - 1] != ' ')
if (rules->s[rules->len - 1] != '\t')
if (rules->s[rules->len - 1] != '\r') break;
--rules->len;
}
if (!stralloc_0(rules)) return DNS_MEM;
i = j + 1;
}
return 0;
}
x = env_get("LOCALDOMAIN");
if (x) {
if (!stralloc_copys(&data, x)) return DNS_MEM;
if (!stralloc_append(&data, " ")) return DNS_MEM;
if (!stralloc_copys(rules, "?:")) return DNS_MEM;
i = 0;
for (j = 0; j < data.len; ++j) {
if (data.s[j] == ' ') {
if (!stralloc_cats(rules, "+.")) return DNS_MEM;
if (!stralloc_catb(rules, data.s + i, j - i)) return DNS_MEM;
i = j + 1;
}
}
if (!stralloc_0(rules)) return DNS_MEM;
if (!stralloc_cats(rules, "*.:")) return DNS_MEM;
if (!stralloc_0(rules)) return DNS_MEM;
return 0;
}
i = openreadclose("/etc/resolv.conf", &data, 64);
if (i == -1) return DNS_INT;
if (i) {
if (!stralloc_append(&data, "\n")) return DNS_MEM;
i = 0;
for (j = 0; j < data.len; ++j) {
if (data.s[j] == '\n') {
if (byte_equal("search ", 7, data.s + i) || byte_equal("search\t", 7, data.s + i)
|| byte_equal("domain ", 7, data.s + i) || byte_equal("domain\t", 7, data.s + i))
{
if (!stralloc_copys(rules, "?:")) return DNS_MEM;
i += 7;
while (i < j) {
k = byte_chr(data.s + i, j - i, ' ');
k = byte_chr(data.s + i, k, '\t');
if (!k) {
++i;
continue;
}
if (!stralloc_cats(rules, "+.")) return DNS_MEM;
if (!stralloc_catb(rules, data.s + i, k)) return DNS_MEM;
i += k;
}
if (!stralloc_0(rules)) return DNS_MEM;
if (!stralloc_cats(rules, "*.:")) return DNS_MEM;
if (!stralloc_0(rules)) return DNS_MEM;
return 0;
}
i = j + 1;
}
}
}
host[0] = 0;
if (gethostname(host, sizeof(host)) == -1) return DNS_ERR;
host[(sizeof(host)) - 1] = 0;
i = str_chr(host, '.');
if (host[i]) {
if (!stralloc_copys(rules, "?:")) return DNS_MEM;
if (!stralloc_cats(rules, host + i)) return DNS_MEM;
if (!stralloc_0(rules)) return DNS_MEM;
}
if (!stralloc_cats(rules, "*.:")) return DNS_MEM;
if (!stralloc_0(rules)) return DNS_MEM;
return 0;
}
static int ok = 0;
static unsigned int uses;
static struct taia deadline;
static stralloc rules = {0}; /* defined if ok */
int dns_resolvconfrewrite(stralloc *out)
{
struct taia now;
taia_now(&now);
if (taia_less(&deadline, &now)) ok = 0;
if (!uses) ok = 0;
if (!ok) {
if (init(&rules) < 0) return DNS_INT;
taia_uint(&deadline, 600);
taia_add(&deadline, &now, &deadline);
uses = 10000;
ok = 1;
}
--uses;
if (!stralloc_copy(out, &rules)) return DNS_MEM;
return 0;
}
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