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multiple client connection attempts if hostname resolves to multiple addresses

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This commit is contained in:
Yakov Olkhovskiy 2022-05-16 17:47:07 -04:00
parent 5c725fe77c
commit fc26505111
3 changed files with 92 additions and 42 deletions
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70
src/Client/Connection.cpp
View File

@ -93,37 +93,59 @@ void Connection::connect(const ConnectionTimeouts & timeouts)
{
try
{
if (connected)
disconnect();
LOG_TRACE(log_wrapper.get(), "Connecting. Database: {}. User: {}{}{}",
default_database.empty() ? "(not specified)" : default_database,
user,
static_cast<bool>(secure) ? ". Secure" : "",
static_cast<bool>(compression) ? "" : ". Uncompressed");
if (static_cast<bool>(secure))
{
#if USE_SSL
socket = std::make_unique<Poco::Net::SecureStreamSocket>();
/// we resolve the ip when we open SecureStreamSocket, so to make Server Name Indication (SNI)
/// work we need to pass host name separately. It will be send into TLS Hello packet to let
/// the server know which host we want to talk with (single IP can process requests for multiple hosts using SNI).
static_cast<Poco::Net::SecureStreamSocket*>(socket.get())->setPeerHostName(host);
#else
throw Exception{"tcp_secure protocol is disabled because poco library was built without NetSSL support.", ErrorCodes::SUPPORT_IS_DISABLED};
#endif
}
else
{
socket = std::make_unique<Poco::Net::StreamSocket>();
}
current_resolved_address = DNSResolver::instance().resolveAddress(host, port);
auto addresses = DNSResolver::instance().resolveAddressList(host, port);
const auto & connection_timeout = static_cast<bool>(secure) ? timeouts.secure_connection_timeout : timeouts.connection_timeout;
socket->connect(*current_resolved_address, connection_timeout);
for (auto it = addresses.begin(); it != addresses.end();)
{
if (connected)
disconnect();
current_resolved_address = *it;
if (static_cast<bool>(secure))
{
#if USE_SSL
socket = std::make_unique<Poco::Net::SecureStreamSocket>();
/// we resolve the ip when we open SecureStreamSocket, so to make Server Name Indication (SNI)
/// work we need to pass host name separately. It will be send into TLS Hello packet to let
/// the server know which host we want to talk with (single IP can process requests for multiple hosts using SNI).
static_cast<Poco::Net::SecureStreamSocket*>(socket.get())->setPeerHostName(host);
#else
throw Exception{"tcp_secure protocol is disabled because poco library was built without NetSSL support.", ErrorCodes::SUPPORT_IS_DISABLED};
#endif
}
else
{
socket = std::make_unique<Poco::Net::StreamSocket>();
}
try
{
socket->connect(*current_resolved_address, connection_timeout);
}
catch (Poco::Net::NetException &)
{
if (++it == addresses.end())
throw;
continue;
}
catch (Poco::TimeoutException &)
{
if (++it == addresses.end())
throw;
continue;
}
break;
}
socket->setReceiveTimeout(timeouts.receive_timeout);
socket->setSendTimeout(timeouts.send_timeout);
socket->setNoDelay(true);

62
src/Common/DNSResolver.cpp
View File

@ -83,25 +83,8 @@ static void splitHostAndPort(const std::string & host_and_port, std::string & ou
throw Exception("Port must be numeric", ErrorCodes::BAD_ARGUMENTS);
}
static DNSResolver::IPAddresses resolveIPAddressImpl(const std::string & host)
static DNSResolver::IPAddresses hostByName(const std::string & host)
{
Poco::Net::IPAddress ip;
/// NOTE:
/// - Poco::Net::DNS::resolveOne(host) doesn't work for IP addresses like 127.0.0.2
/// - Poco::Net::IPAddress::tryParse() expect hex string for IPv6 (without brackets)
if (host.starts_with('['))
{
assert(host.ends_with(']'));
if (Poco::Net::IPAddress::tryParse(host.substr(1, host.size() - 2), ip))
return DNSResolver::IPAddresses(1, ip);
}
else
{
if (Poco::Net::IPAddress::tryParse(host, ip))
return DNSResolver::IPAddresses(1, ip);
}
/// Family: AF_UNSPEC
/// AI_ALL is required for checking if client is allowed to connect from an address
auto flags = Poco::Net::DNS::DNS_HINT_AI_V4MAPPED | Poco::Net::DNS::DNS_HINT_AI_ALL;
@ -131,6 +114,30 @@ static DNSResolver::IPAddresses resolveIPAddressImpl(const std::string & host)
return addresses;
}
static DNSResolver::IPAddresses resolveIPAddressImpl(const std::string & host)
{
Poco::Net::IPAddress ip;
/// NOTE:
/// - Poco::Net::DNS::resolveOne(host) doesn't work for IP addresses like 127.0.0.2
/// - Poco::Net::IPAddress::tryParse() expect hex string for IPv6 (without brackets)
if (host.starts_with('['))
{
assert(host.ends_with(']'));
if (Poco::Net::IPAddress::tryParse(host.substr(1, host.size() - 2), ip))
return DNSResolver::IPAddresses(1, ip);
}
else
{
if (Poco::Net::IPAddress::tryParse(host, ip))
return DNSResolver::IPAddresses(1, ip);
}
DNSResolver::IPAddresses addresses = hostByName(host);
return addresses;
}
static String reverseResolveImpl(const Poco::Net::IPAddress & address)
{
Poco::Net::SocketAddress sock_addr(address, 0);
@ -208,6 +215,25 @@ Poco::Net::SocketAddress DNSResolver::resolveAddress(const std::string & host, U
return Poco::Net::SocketAddress(impl->cache_host(host).front(), port);
}
std::vector<Poco::Net::SocketAddress> DNSResolver::resolveAddressList(const std::string & host, UInt16 port)
{
if (Poco::Net::IPAddress ip; Poco::Net::IPAddress::tryParse(host, ip))
return std::vector<Poco::Net::SocketAddress>{{ip, port}};
std::vector<Poco::Net::SocketAddress> addresses;
if (!impl->disable_cache)
addToNewHosts(host);
std::vector<Poco::Net::IPAddress> ips = impl->disable_cache ? hostByName(host) : impl->cache_host(host);
auto ips_end = std::unique(ips.begin(), ips.end());
for (auto ip = ips.begin(); ip != ips_end; ++ip)
addresses.emplace_back(*ip, port);
return addresses;
}
String DNSResolver::reverseResolve(const Poco::Net::IPAddress & address)
{
if (impl->disable_cache)

2
src/Common/DNSResolver.h
View File

@ -34,6 +34,8 @@ public:
Poco::Net::SocketAddress resolveAddress(const std::string & host, UInt16 port);
std::vector<Poco::Net::SocketAddress> resolveAddressList(const std::string & host, UInt16 port);
/// Accepts host IP and resolves its host name
String reverseResolve(const Poco::Net::IPAddress & address);