X-Git-Url: https://git.saurik.com/apt.git/blobdiff_plain/f106fecc1d7d0250d1d76c2ba837dc0c870c5fff..671a55ba455dcf4e5ce6d86b202761666f54d5c6:/apt-pkg/contrib/srvrec.cc

diff --git a/apt-pkg/contrib/srvrec.cc b/apt-pkg/contrib/srvrec.cc
index d5d89fc67..be159bad9 100644
--- a/apt-pkg/contrib/srvrec.cc
+++ b/apt-pkg/contrib/srvrec.cc
@@ -8,13 +8,46 @@
 									/*}}}*/
 #include <config.h>
 
+#include <netdb.h>
+
 #include <netinet/in.h>
 #include <arpa/nameser.h>
 #include <resolv.h>
+#include <time.h>
+
+#include <algorithm>
+#include <tuple>
 
+#include <apt-pkg/configuration.h>
 #include <apt-pkg/error.h>
+#include <apt-pkg/strutl.h>
+
+
 #include "srvrec.h"
 
+
+bool SrvRec::operator==(SrvRec const &other) const
+{
+   return (std::tie(target, priority, weight, port) ==
+           std::tie(other.target, other.priority, other.weight, other.port));
+}
+
+bool GetSrvRecords(std::string host, int port, std::vector<SrvRec> &Result)
+{
+   std::string target;
+   int res;
+   struct servent s_ent_buf;
+   struct servent *s_ent = nullptr;
+   std::vector<char> buf(1024);
+
+   res = getservbyport_r(htons(port), "tcp", &s_ent_buf, buf.data(), buf.size(), &s_ent);
+   if (res != 0 || s_ent == nullptr)
+      return false;
+
+   strprintf(target, "_%s._tcp.%s", s_ent->s_name, host.c_str());
+   return GetSrvRecords(target, Result);
+}
+
 bool GetSrvRecords(std::string name, std::vector<SrvRec> &Result)
 {
    unsigned char answer[PACKETSZ];
@@ -25,6 +58,8 @@ bool GetSrvRecords(std::string name, std::vector<SrvRec> &Result)
       return _error->Errno("res_init", "Failed to init resolver");
 
    answer_len = res_query(name.c_str(), C_IN, T_SRV, answer, sizeof(answer));
+   if (answer_len == -1)
+      return false;
    if (answer_len < (int)sizeof(HEADER))
       return _error->Warning("Not enough data from res_query (%i)", answer_len);
 
@@ -45,10 +80,9 @@ bool GetSrvRecords(std::string name, std::vector<SrvRec> &Result)
    unsigned char *pt = answer+sizeof(HEADER)+compressed_name_len+QFIXEDSZ;
    while ((int)Result.size() < answer_count && pt < answer+answer_len)
    {
-      SrvRec rec;
       u_int16_t type, klass, priority, weight, port, dlen;
       char buf[MAXDNAME];
-      
+
       compressed_name_len = dn_skipname(pt, answer+answer_len);
       if (compressed_name_len < 0)
          return _error->Warning("dn_skipname failed (2): %i",
@@ -58,15 +92,15 @@ bool GetSrvRecords(std::string name, std::vector<SrvRec> &Result)
          return _error->Warning("packet too short");
 
       // extract the data out of the result buffer
-      #define extract_u16(target, p) target = *p++ << 8; target |= *p++; 
+      #define extract_u16(target, p) target = *p++ << 8; target |= *p++;
 
       extract_u16(type, pt);
       if(type != T_SRV)
-         return _error->Warning("Unexpected type excepted %x != %x", 
+         return _error->Warning("Unexpected type excepted %x != %x",
                                 T_SRV, type);
       extract_u16(klass, pt);
       if(klass != C_IN)
-         return _error->Warning("Unexpected class excepted %x != %x", 
+         return _error->Warning("Unexpected class excepted %x != %x",
                                 C_IN, klass);
       pt += 4;  // ttl
       extract_u16(dlen, pt);
@@ -82,12 +116,81 @@ bool GetSrvRecords(std::string name, std::vector<SrvRec> &Result)
       pt += compressed_name_len;
 
       // add it to our class
-      rec.priority = priority;
-      rec.weight = weight;
-      rec.port = port;
-      rec.target = buf;
-      Result.push_back(rec);
+      Result.emplace_back(buf, priority, weight, port);
+   }
+
+   // implement load balancing as specified in RFC-2782
+
+   // sort them by priority
+   std::stable_sort(Result.begin(), Result.end());
+
+   for(std::vector<SrvRec>::iterator I = Result.begin();
+      I != Result.end(); ++I)
+   {
+      if (_config->FindB("Debug::Acquire::SrvRecs", false) == true)
+      {
+         std::cerr << "SrvRecs: got " << I->target
+                   << " prio: " << I->priority
+                   << " weight: " << I->weight
+                   << std::endl;
+      }
    }
 
    return true;
 }
+
+SrvRec PopFromSrvRecs(std::vector<SrvRec> &Recs)
+{
+   // FIXME: instead of the simplistic shuffle below use the algorithm
+   //        described in rfc2782 (with weights)
+   //        and figure out how the weights need to be adjusted if
+   //        a host refuses connections
+
+#if 0  // all code below is only needed for the weight adjusted selection 
+   // assign random number ranges
+   int prev_weight = 0;
+   int prev_priority = 0;
+   for(std::vector<SrvRec>::iterator I = Result.begin();
+      I != Result.end(); ++I)
+   {
+      if(prev_priority != I->priority)
+         prev_weight = 0;
+      I->random_number_range_start = prev_weight;
+      I->random_number_range_end = prev_weight + I->weight;
+      prev_weight = I->random_number_range_end;
+      prev_priority = I->priority;
+
+      if (_config->FindB("Debug::Acquire::SrvRecs", false) == true)
+         std::cerr << "SrvRecs: got " << I->target
+                   << " prio: " << I->priority
+                   << " weight: " << I->weight
+                   << std::endl;
+   }
+
+   // go over the code in reverse order and note the max random range
+   int max = 0;
+   prev_priority = 0;
+   for(std::vector<SrvRec>::iterator I = Result.end();
+      I != Result.begin(); --I)
+   {
+      if(prev_priority != I->priority)
+         max = I->random_number_range_end;
+      I->random_number_range_max = max;
+   }
+#endif
+
+   // shuffle in a very simplistic way for now (equal weights)
+   std::vector<SrvRec>::iterator I = Recs.begin();
+   std::vector<SrvRec>::iterator const J = std::find_if(Recs.begin(), Recs.end(),
+	 [&I](SrvRec const &J) { return I->priority != J.priority; });
+
+   // clock seems random enough.
+   I += clock() % std::distance(I, J);
+   SrvRec const selected = std::move(*I);
+   Recs.erase(I);
+
+   if (_config->FindB("Debug::Acquire::SrvRecs", false) == true)
+      std::cerr << "PopFromSrvRecs: selecting " << selected.target << std::endl;
+
+   return selected;
+}