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#include "stralloc.h"
#include "byte.h"
#include "uint_t.h"
#include "dnsresolv.h"
/**
* @file dns_mx.c
* @author djb
* @ref qmail
* @brief dns MX query
* @param (on output) stralloc out
*/
static char *q = 0;
int dns_mx_packet(stralloc *out,const char *buf,unsigned int len)
{
unsigned int pos;
char header[12];
char pref[2];
uint16 numanswers;
uint16 datalen;
int ranswers = 0;
if (!stralloc_copys(out,"")) return DNS_MEM;
pos = dns_packet_copy(buf,len,0,header,12); if (!pos) return DNS_ERR;
uint16_unpack_big(header + 6,&numanswers);
pos = dns_packet_skipname(buf,len,pos); if (!pos) return DNS_ERR;
pos += 4;
while (numanswers--) {
pos = dns_packet_skipname(buf,len,pos); if (!pos) return DNS_ERR;
pos = dns_packet_copy(buf,len,pos,header,10); if (!pos) return DNS_ERR;
uint16_unpack_big(header + 8,&datalen);
if (byte_equal(header,2,DNS_T_MX))
if (byte_equal(header + 2,2,DNS_C_IN)) {
if (!dns_packet_copy(buf,len,pos,pref,2)) return DNS_ERR;
if (!dns_packet_getname(buf,len,pos + 2,&q)) return DNS_ERR;
if (!stralloc_catb(out,pref,2)) return DNS_MEM;
if (dns_domain_todot_cat(out,q) <= 0) return DNS_ERR;
if (!stralloc_0(out)) return DNS_MEM;
}
pos += datalen;
++ranswers;
}
return ranswers;
}
int dns_mx(stralloc *out,const stralloc *fqdn)
{
int rc = 0;
if (dns_domain_fromdot(&q,fqdn->s,fqdn->len) <= 0) return DNS_ERR;
if (dns_resolve(q,DNS_T_MX) >= 0) {
if ((rc = dns_mx_packet(out,dns_resolve_tx.packet,dns_resolve_tx.packetlen)) < 0) return DNS_ERR;
dns_transmit_free(&dns_resolve_tx);
dns_domain_free(&q);
}
return rc;
}
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