1 #include "stralloc.h"
2 #include "byte.h"
3 #include "uint16.h"
4 #include "dns.h"
5
6 static char *q = 0;
7
dns_mx_packet(stralloc * out,const char * buf,unsigned int len)8 int dns_mx_packet(stralloc *out,const char *buf,unsigned int len)
9 {
10 unsigned int pos;
11 char header[12];
12 char pref[2];
13 uint16 numanswers;
14 uint16 datalen;
15
16 if (!stralloc_copys(out,"")) return -1;
17
18 pos = dns_packet_copy(buf,len,0,header,12); if (!pos) return -1;
19 uint16_unpack_big(header + 6,&numanswers);
20 pos = dns_packet_skipname(buf,len,pos); if (!pos) return -1;
21 pos += 4;
22
23 while (numanswers--) {
24 pos = dns_packet_skipname(buf,len,pos); if (!pos) return -1;
25 pos = dns_packet_copy(buf,len,pos,header,10); if (!pos) return -1;
26 uint16_unpack_big(header + 8,&datalen);
27 if (byte_equal(header,2,DNS_T_MX))
28 if (byte_equal(header + 2,2,DNS_C_IN)) {
29 if (!dns_packet_copy(buf,len,pos,pref,2)) return -1;
30 if (!dns_packet_getname(buf,len,pos + 2,&q)) return -1;
31 if (!stralloc_catb(out,pref,2)) return -1;
32 if (!dns_domain_todot_cat(out,q)) return -1;
33 if (!stralloc_0(out)) return -1;
34 }
35 pos += datalen;
36 }
37
38 return 0;
39 }
40
dns_mx(stralloc * out,const stralloc * fqdn)41 int dns_mx(stralloc *out,const stralloc *fqdn)
42 {
43 if (!dns_domain_fromdot(&q,fqdn->s,fqdn->len)) return -1;
44 if (dns_resolve(q,DNS_T_MX) == -1) return -1;
45 if (dns_mx_packet(out,dns_resolve_tx.packet,dns_resolve_tx.packetlen) == -1) return -1;
46 dns_transmit_free(&dns_resolve_tx);
47 dns_domain_free(&q);
48 return 0;
49 }
50