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/**
* @file llsrv.cpp
* @brief Wrapper for DNS SRV record lookups
*
* Copyright (c) 2007-$CurrentYear$, Linden Research, Inc.
* $License$
*/
#include "llviewerprecompiledheaders.h"
#include "llsrv.h"
using namespace std;
#if LL_WINDOWS
#undef UNICODE
#include <winsock2.h>
#include <windns.h>
vector<LLSRVRecord> LLSRV::query(const string& name)
{
vector<LLSRVRecord> recs;
DNS_RECORD *rec;
DNS_STATUS status;
status = DnsQuery(name.c_str(), DNS_TYPE_SRV, DNS_QUERY_STANDARD, NULL, &rec, NULL);
if (!status)
{
for (DNS_RECORD *cur = rec; cur != NULL; cur = cur->pNext)
{
if (cur->wType != DNS_TYPE_SRV)
{
continue;
}
recs.push_back(LLSRVRecord(cur->Data.Srv.wPriority,
cur->Data.Srv.wWeight,
cur->Data.Srv.pNameTarget,
cur->Data.Srv.wPort));
}
DnsRecordListFree(rec, DnsFreeRecordListDeep);
}
return recs;
}
#else // !LL_WINDOWS
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <arpa/nameser_compat.h>
#include <resolv.h>
#include <netdb.h>
vector<LLSRVRecord> LLSRV::query(const string& queryName)
{
unsigned char response[16384];
vector<LLSRVRecord> recs;
char name[1024];
int len;
len = res_query(queryName.c_str(), ns_c_in, ns_t_srv, response,
sizeof(response));
if (len == -1)
{
llinfos << "Query failed for " << queryName << llendl;
return recs;
}
else if (len > (int) sizeof(response))
{
llinfos << "Response too big for " << queryName
<< " (capacity " << sizeof(response)
<< ", response " << len << ")" << llendl;
return recs;
}
// We "should" be using libresolv's ns_initparse and ns_parserr to
// parse the result of our query. However, libresolv isn't
// packaged correctly on Linux (as of BIND 9), so neither of these
// functions is available without statically linking against
// libresolv. Ugh! So we parse the response ourselves.
const unsigned char *pos = response + sizeof(HEADER);
const unsigned char *end = response + len;
const HEADER *hdr = (const HEADER *) response;
// Skip over the query embedded in the response.
for (int q = ntohs(hdr->qdcount); q > 0; --q)
{
len = dn_expand(response, end, pos, name, sizeof(name));
if (len == -1)
{
llinfos << "Could not expand queried name in RR response" << llendl;
return recs;
}
pos += len + NS_QFIXEDSZ;
}
for (int a = ntohs(hdr->ancount); a > 0; --a)
{
static const ns_rr *rr;
len = dn_expand(response, end, pos, name, sizeof(name) - 1);
if (len == -1)
{
llinfos << "Could not expand response name in RR response" << llendl;
return recs;
}
// Skip over the resource name and headers we don't care about.
pos += len + sizeof(rr->type) + sizeof(rr->rr_class) +
sizeof(rr->ttl) + sizeof(rr->rdlength);
U16 prio;
U16 weight;
U16 port;
NS_GET16(prio, pos);
NS_GET16(weight, pos);
NS_GET16(port, pos);
len = dn_expand(response, end, pos, name, sizeof(name) - 1);
if (len == -1)
{
llinfos << "Could not expand name in RR response" << llendl;
return recs;
}
recs.push_back(LLSRVRecord(prio, weight, name, port));
}
// There are likely to be more records in the response, but we
// don't care about those, at least for now.
return recs;
}
#endif // LL_WINDOWS
vector<string> LLSRV::rewriteURI(const string& uriStr)
{
LLURI uri(uriStr);
const string& scheme = uri.scheme();
llinfos << "Rewriting " << uriStr << llendl;
string serviceName("_" + scheme + "._tcp." + uri.hostName());
llinfos << "Querying for " << serviceName << llendl;
vector<LLSRVRecord> srvs(LLSRV::query(serviceName));
vector<string> rewritten;
if (srvs.empty())
{
llinfos << "No query results; using " << uriStr << llendl;
rewritten.push_back(uriStr);
}
else
{
vector<LLSRVRecord>::const_iterator iter;
size_t maxSrvs = 3;
size_t i;
llinfos << "Got " << srvs.size() << " results" << llendl;
if (srvs.size() > maxSrvs)
{
llinfos << "Clamping to " << maxSrvs << llendl;
}
for (iter = srvs.begin(), i = 0;
iter != srvs.end() && i < maxSrvs; ++iter, ++i)
{
LLURI newUri(scheme,
uri.userName(),
uri.password(),
iter->target(),
uri.defaultPort() ? iter->port() : uri.hostPort(),
uri.escapedPath(),
uri.escapedQuery());
string newUriStr(newUri.asString());
llinfos << "Rewrite[" << i << "] " << newUriStr << llendl;
rewritten.push_back(newUriStr);
}
}
return rewritten;
}
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