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#include "meta.h"
#include "caddrinfo.h"
#include "sockio.h"
#include "acfg.h"
#include "debug.h"
#include "lockable.h"
#include "cleaner.h"
#include <queue>
using namespace std;
namespace acng
{
static const unsigned DNS_CACHE_MAX=255;
base_with_condition dnsCacheCv;
map<tStrPair,CAddrInfoPtr> dnsCache;
// simple prio-queue to track the oldest entries
typedef decltype(dnsCache)::iterator dnsIter;
struct tDnsCmpEarliest
{
bool operator() (const dnsIter& x,const dnsIter& y)
{
return (x->second->m_nExpTime > y->second->m_nExpTime);
}
};
priority_queue<dnsIter, vector<dnsIter>, tDnsCmpEarliest> dnsCleanupQ;
bool CAddrInfo::Resolve(const string & sHostname, const string &sPort,
string & sErrorBuf)
{
LOGSTART2("CAddrInfo::Resolve", "Resolving " << sHostname);
m_bError = false;
m_bResInProgress = true;
LPCSTR port = sPort.empty() ? nullptr : sPort.c_str();
static struct addrinfo hints =
{
// we provide numbers, no resolution needed; only supported addresses
(port ? AI_NUMERICSERV:0) | AI_ADDRCONFIG,
PF_UNSPEC, SOCK_STREAM, IPPROTO_TCP,
0, nullptr, nullptr, nullptr };
// if only one family is specified, filter on this earlier
if(cfg::conprotos[0] != PF_UNSPEC && cfg::conprotos[1] == PF_UNSPEC)
hints.ai_family = cfg::conprotos[0];
if (m_resolvedInfo)
{
freeaddrinfo(m_resolvedInfo);
m_resolvedInfo=nullptr;
}
int r=getaddrinfo(sHostname.c_str(), port, &hints, &m_resolvedInfo);
if (0!=r)
{
sErrorBuf=(tSS()<<"503 DNS error for hostname "<<sHostname<<": "<<gai_strerror(r)
<<". If "<<sHostname<<" refers to a configured cache repository, "
"please check the corresponding configuration file.");
m_bError = true;
m_bResInProgress = false;
return false;
}
LOG("Host resolved");
// find any suitable-looking entry and keep a pointer to it
for (auto pCur=m_resolvedInfo; pCur && m_bResInProgress ; pCur = pCur->ai_next)
{
if (pCur->ai_socktype == SOCK_STREAM&& pCur->ai_protocol == IPPROTO_TCP)
{
m_addrInfo=pCur;
m_bResInProgress = false;
return true;
}
}
if(!m_bResInProgress)
return true;
LOG("couldn't find working DNS config");
m_bError = true;
m_bResInProgress = false;
sErrorBuf="500 DNS resolution error";
return false;
}
CAddrInfo::~CAddrInfo()
{
if (m_resolvedInfo)
freeaddrinfo(m_resolvedInfo);
}
CAddrInfoPtr CAddrInfo::CachedResolve(const string & sHostname, const string &sPort, string &sErrorMsgBuf)
{
// set if someone is responsible for cleaning it up later
bool added2cache = false;
auto dnsKey=make_pair(sHostname, sPort);
CAddrInfoPtr job;
if (!cfg::dnscachetime)
{
job.reset(new CAddrInfo);
goto plain_resolve;
}
if(!cfg::dnscachetime)
goto plain_resolve;
{
lockuniq lg(dnsCacheCv);
auto now = GetTime();
// every caller does little cleanup work first
while(!dnsCleanupQ.empty())
{
auto p = dnsCleanupQ.top()->second;
if(p->m_nExpTime >= now)
{
dnsCache.erase(dnsCleanupQ.top());
dnsCleanupQ.pop();
}
else if(dnsCleanupQ.size() < DNS_CACHE_MAX) // remaining ones are fresh enough unless we need to shrink the cache
break;
}
// observe a DNS process in progress if needed
auto it = dnsCache.find(dnsKey);
if(it != dnsCache.end())
{
auto p = it->second;
while(p->m_bResInProgress)
dnsCacheCv.wait(lg);
if(p->m_bError)
{
sErrorMsgBuf = string("Error resolving ") + sHostname;
return job; // still invalid pointer
}
// otherwise it's ok
return p;
}
job = make_shared<CAddrInfo>();
added2cache = dnsCache.size() < DNS_CACHE_MAX; // if looks like DOS, don't dirty the temp queue with it
if(added2cache)
dnsCache.insert(make_pair(dnsKey, job));
}
plain_resolve:
bool ok = job->Resolve(sHostname, sPort, sErrorMsgBuf);
// there is a slight risk that someone else expired our entry in the meantime, but it's unlikely and should be harmless
if(added2cache)
{
lockguard lg(dnsCacheCv);
dnsCacheCv.notifyAll();
if(ok)
{
auto it = dnsCache.find(dnsKey);
if(it != dnsCache.end())
dnsCleanupQ.push(it);
}
else
dnsCache.erase(dnsKey);
}
return ok ? job : CAddrInfoPtr();
}
void DropDnsCache()
{
lockguard g(dnsCacheCv);
dnsCache.clear();
dnsCleanupQ = decltype(dnsCleanupQ)();
}
}
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