apt-pkg/contrib/srvrec.cc

   1 // -*- mode: cpp; mode: fold -*-
   2 // Description                                                          /*{{{*/
   3 /* ######################################################################
   4
   5    SRV record support
   6
   7    ##################################################################### */
   8                                                                         /*}}}*/
   9 #include <config.h>
  10
  11 #include <netinet/in.h>
  12 #include <arpa/nameser.h>
  13 #include <resolv.h>
  14
  15 #include <algorithm>
  16
  17 #include <apt-pkg/error.h>
  18 #include "srvrec.h"
  19
  20 bool GetSrvRecords(std::string name, std::vector<SrvRec> &Result)
  21 {
  22    unsigned char answer[PACKETSZ];
  23    int answer_len, compressed_name_len;
  24    int answer_count;
  25
  26    if (res_init() != 0)
  27       return _error->Errno("res_init", "Failed to init resolver");
  28
  29    answer_len = res_query(name.c_str(), C_IN, T_SRV, answer, sizeof(answer));
  30    if (answer_len < (int)sizeof(HEADER))
  31       return _error->Warning("Not enough data from res_query (%i)", answer_len);
  32
  33    // check the header
  34    HEADER *header = (HEADER*)answer;
  35    if (header->rcode != NOERROR)
  36       return _error->Warning("res_query returned rcode %i", header->rcode);
  37    answer_count = ntohs(header->ancount);
  38    if (answer_count <= 0)
  39       return _error->Warning("res_query returned no answers (%i) ", answer_count);
  40
  41    // skip the header
  42    compressed_name_len = dn_skipname(answer+sizeof(HEADER), answer+answer_len);
  43    if(compressed_name_len < 0)
  44       return _error->Warning("dn_skipname failed %i", compressed_name_len);
  45
  46    // pt points to the first answer record, go over all of them now
  47    unsigned char *pt = answer+sizeof(HEADER)+compressed_name_len+QFIXEDSZ;
  48    while ((int)Result.size() < answer_count && pt < answer+answer_len)
  49    {
  50       SrvRec rec;
  51       u_int16_t type, klass, priority, weight, port, dlen;
  52       char buf[MAXDNAME];
  53
  54       compressed_name_len = dn_skipname(pt, answer+answer_len);
  55       if (compressed_name_len < 0)
  56          return _error->Warning("dn_skipname failed (2): %i",
  57                                 compressed_name_len);
  58       pt += compressed_name_len;
  59       if (((answer+answer_len) - pt) < 16)
  60          return _error->Warning("packet too short");
  61
  62       // extract the data out of the result buffer
  63       #define extract_u16(target, p) target = *p++ << 8; target |= *p++;
  64
  65       extract_u16(type, pt);
  66       if(type != T_SRV)
  67          return _error->Warning("Unexpected type excepted %x != %x",
  68                                 T_SRV, type);
  69       extract_u16(klass, pt);
  70       if(klass != C_IN)
  71          return _error->Warning("Unexpected class excepted %x != %x",
  72                                 C_IN, klass);
  73       pt += 4;  // ttl
  74       extract_u16(dlen, pt);
  75       extract_u16(priority, pt);
  76       extract_u16(weight, pt);
  77       extract_u16(port, pt);
  78
  79       #undef extract_u16
  80
  81       compressed_name_len = dn_expand(answer, answer+answer_len, pt, buf, sizeof(buf));
  82       if(compressed_name_len < 0)
  83          return _error->Warning("dn_expand failed %i", compressed_name_len);
  84       pt += compressed_name_len;
  85
  86       // add it to our class
  87       rec.priority = priority;
  88       rec.weight = weight;
  89       rec.port = port;
  90       rec.target = buf;
  91       Result.push_back(rec);
  92    }
  93
  94    // sort them
  95    std::stable_sort(Result.begin(), Result.end());
  96
  97    // FIXME: implement weight selection as specified in RFC-2782
  98
  99    return true;
 100 }