diff options
Diffstat (limited to 'apt-pkg')
| -rw-r--r-- | apt-pkg/contrib/srvrec.cc | 141 | ||||
| -rw-r--r-- | apt-pkg/contrib/srvrec.h | 42 | ||||
| -rw-r--r-- | apt-pkg/makefile | 2 |
3 files changed, 184 insertions, 1 deletions
diff --git a/apt-pkg/contrib/srvrec.cc b/apt-pkg/contrib/srvrec.cc new file mode 100644 index 000000000..70247c2ae --- /dev/null +++ b/apt-pkg/contrib/srvrec.cc @@ -0,0 +1,141 @@ +// -*- mode: cpp; mode: fold -*- +// Description /*{{{*/ +/* ###################################################################### + + SRV record support + + ##################################################################### */ + /*}}}*/ +#include <config.h> + +#include <netdb.h> + +#include <netinet/in.h> +#include <arpa/nameser.h> +#include <resolv.h> + +#include <algorithm> + +#include <apt-pkg/strutl.h> +#include <apt-pkg/error.h> +#include "srvrec.h" + +bool GetSrvRecords(std::string host, int port, std::vector<SrvRec> &Result) +{ + std::string target; + struct servent *s_ent = getservbyport(htons(port), "tcp"); + if (s_ent == NULL) + 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]; + int answer_len, compressed_name_len; + int answer_count; + + if (res_init() != 0) + 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 < (int)sizeof(HEADER)) + return _error->Warning("Not enough data from res_query (%i)", answer_len); + + // check the header + HEADER *header = (HEADER*)answer; + if (header->rcode != NOERROR) + return _error->Warning("res_query returned rcode %i", header->rcode); + answer_count = ntohs(header->ancount); + if (answer_count <= 0) + return _error->Warning("res_query returned no answers (%i) ", answer_count); + + // skip the header + compressed_name_len = dn_skipname(answer+sizeof(HEADER), answer+answer_len); + if(compressed_name_len < 0) + return _error->Warning("dn_skipname failed %i", compressed_name_len); + + // pt points to the first answer record, go over all of them now + 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", + compressed_name_len); + pt += compressed_name_len; + if (((answer+answer_len) - pt) < 16) + return _error->Warning("packet too short"); + + // extract the data out of the result buffer + #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", + T_SRV, type); + extract_u16(klass, pt); + if(klass != C_IN) + return _error->Warning("Unexpected class excepted %x != %x", + C_IN, klass); + pt += 4; // ttl + extract_u16(dlen, pt); + extract_u16(priority, pt); + extract_u16(weight, pt); + extract_u16(port, pt); + + #undef extract_u16 + + compressed_name_len = dn_expand(answer, answer+answer_len, pt, buf, sizeof(buf)); + if(compressed_name_len < 0) + return _error->Warning("dn_expand failed %i", compressed_name_len); + 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); + } + + // implement load balancing as specified in RFC-2782 + + // sort them by priority + std::stable_sort(Result.begin(), Result.end()); + + // 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; + } + + // 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; + } + + // now shuffle + + return true; +} diff --git a/apt-pkg/contrib/srvrec.h b/apt-pkg/contrib/srvrec.h new file mode 100644 index 000000000..79b318b48 --- /dev/null +++ b/apt-pkg/contrib/srvrec.h @@ -0,0 +1,42 @@ +// -*- mode: cpp; mode: fold -*- +// Description /*{{{*/ +/* ###################################################################### + + SRV record support + + ##################################################################### */ + /*}}}*/ +#ifndef SRVREC_H +#define SRVREC_H + +#include <arpa/nameser.h> +#include <vector> +#include <string> + +class SrvRec +{ + public: + std::string target; + u_int16_t priority; + u_int16_t weight; + u_int16_t port; + + // each server is assigned a interval [start, end] in the space of [0, max] + int random_number_range_start; + int random_number_range_end; + int random_number_range_max; + + bool operator<(SrvRec const &other) const { + return this->priority < other.priority; + } +}; + +/** \brief Get SRV records from host/port (builds the query string internally) + */ +bool GetSrvRecords(std::string name, std::vector<SrvRec> &Result); + +/** \brief Get SRV records for query string like: _http._tcp.example.com + */ +bool GetSrvRecords(std::string host, int port, std::vector<SrvRec> &Result); + +#endif diff --git a/apt-pkg/makefile b/apt-pkg/makefile index 5603b51ed..45dcddfe3 100644 --- a/apt-pkg/makefile +++ b/apt-pkg/makefile @@ -15,7 +15,7 @@ include ../buildlib/libversion.mak LIBRARY=apt-pkg MAJOR=$(LIBAPTPKG_MAJOR) MINOR=$(LIBAPTPKG_RELEASE) -SLIBS=$(PTHREADLIB) $(INTLLIBS) -lutil -ldl +SLIBS=$(PTHREADLIB) $(INTLLIBS) -lutil -ldl -lresolv ifeq ($(HAVE_ZLIB),yes) SLIBS+= -lz endif |