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#pragma once
#include <contrib/libs/c-ares/include/ares.h>
#include <util/generic/map.h>
#include <util/generic/vector.h>
#include <util/network/address.h>
#include <util/system/mutex.h>
#include <util/datetime/base.h>
/** Asynchronous DNS resolver.
*
* This is NOT general purpose resolver! It is designed with very specific assumptions:
* 1) there is relatively small and rarely changed set of resolved names (like, server pool in cluster)
* 2) this names supposed to have addresses, absense of A record is equal to DNS error
* 3) most of the time IP addresses do not change
* 4) it's OK to return old IP address when DNS server not responding in time
*/
class TDnsCache {
public:
TDnsCache(bool allowIpv4 = true, bool allowIpv6 = true, time_t entry_lifetime = 1800, time_t neg_lifetime = 1, ui32 request_timeout = 500000);
~TDnsCache();
TString GetHostByAddr(const NAddr::IRemoteAddr&);
// ip in network byte order
TIpHost Get(const TString& host);
/* use with AF_INET, AF_INET6 or AF_UNSPEC */
NAddr::IRemoteAddrPtr GetAddr(const TString& host,
int family,
TIpPort port = 0,
bool cacheOnly = false);
void GetAllAddresses(const TString& host, TVector<NAddr::IRemoteAddrPtr>&);
void GetStats(ui64& a_cache_hits, ui64& a_cache_misses,
ui64& ptr_cache_hits, ui64& ptr_cache_misses);
protected:
bool ValidateHName(const TString& host) const noexcept;
private:
struct TGHBNContext {
TDnsCache* Owner;
TString Hostname;
int Family;
};
struct TGHBAContext {
TDnsCache* Owner;
in6_addr Addr;
};
struct THost {
THost() noexcept {
}
TVector<TIpHost> AddrsV4;
time_t ResolvedV4 = 0;
time_t NotFoundV4 = 0;
TAtomic InProgressV4 = 0;
TVector<in6_addr> AddrsV6;
time_t ResolvedV6 = 0;
time_t NotFoundV6 = 0;
TAtomic InProgressV6 = 0;
TString AddrsV4ToString() const;
TString AddrsV6ToString() const;
bool IsStale(int family, const TDnsCache* ctx) const noexcept;
};
typedef TMap<TString, THost> THostCache;
struct TAddr {
TString Hostname;
time_t Resolved = 0;
time_t NotFound = 0;
TAtomic InProgress = 0;
};
/* IRemoteAddr is annoingly hard to use, so I'll use in6_addr as key
* and put v4 addrs in it.
*/
struct TAddrCmp {
bool operator()(const in6_addr& left, const in6_addr& right) const {
for (size_t i = 0; i < sizeof(left); i++) {
if (left.s6_addr[i] < right.s6_addr[i]) {
return true;
} else if (left.s6_addr[i] > right.s6_addr[i]) {
return false;
}
}
// equal
return false;
}
};
typedef TMap<in6_addr, TAddr, TAddrCmp> TAddrCache;
const THost& Resolve(const TString&, int family, bool cacheOnly = false);
const TAddr& ResolveAddr(const in6_addr&, int family);
void WaitTask(TAtomic&);
static void GHBNCallback(void* arg, int status, int timeouts,
struct hostent* info);
static void GHBACallback(void* arg, int status, int timeouts,
struct hostent* info);
const time_t EntryLifetime;
const time_t NegativeLifetime;
const TDuration Timeout;
const bool AllowIpV4;
const bool AllowIpV6;
TMutex CacheMtx;
THostCache HostCache;
TAddrCache AddrCache;
ui64 ACacheHits;
ui64 ACacheMisses;
ui64 PtrCacheHits;
ui64 PtrCacheMisses;
const static THost NullHost;
TMutex AresMtx;
void* Channel;
struct TAresLibInit {
TAresLibInit() {
#ifdef _win_
const auto res = ares_library_init(ARES_LIB_INIT_ALL);
Y_VERIFY(res == 0);
#endif
}
~TAresLibInit() {
#ifdef _win_
ares_library_cleanup();
#endif
}
};
static TAresLibInit InitAresLib;
};
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