2V1-a: port the EterLib network layer and the Crypto++ packet cipher

NetStream/NetAddress/NetDevice/NetPacketHeaderMap and EterBase/cipher.cpp
are mechanical copies. The winsock shim maps Winsock onto BSD sockets and
keeps the Winsock semantics CNetworkStream relies on: select ignores nfds,
a socket whose connect failed is not writable (40250 times out instead),
EINPROGRESS reads as WSAEWOULDBLOCK, and SIGPIPE is ignored.

port.net covers loopback connect, send/recv, peer close, the refused
connect timeout and the client/server key agreement.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

extension/src/port/CMakeLists.txt

@@ -174,6 +174,10 @@ if(BUILD_TESTING AND CMAKE_SYSTEM_NAME STREQUAL CMAKE_HOST_SYSTEM_NAME)
     add_test(NAME port.text COMMAND $<TARGET_FILE:port_text_test>)
     set_tests_properties(port.text PROPERTIES SKIP_RETURN_CODE 77)
 
+    add_executable(port_net_test ${CMAKE_CURRENT_SOURCE_DIR}/../../tests/port_net_test.cpp)
+    target_link_libraries(port_net_test PRIVATE port_platform)
+    add_test(NAME port.net COMMAND $<TARGET_FILE:port_net_test>)
+
     if(TARGET mtpython)
         add_executable(port_python_launcher_test ${CMAKE_CURRENT_SOURCE_DIR}/../../tests/port_python_launcher_test.cpp)
         target_link_libraries(port_python_launcher_test PRIVATE port_platform)

extension/src/port/EterBase/cipher.cpp

@@ -0,0 +1,448 @@
+#include "StdAfx.h"
+
+#include "cipher.h"
+
+#ifdef _IMPROVED_PACKET_ENCRYPTION_
+
+//#pragma warning(push)
+//#pragma warning(disable: 4100 4127 4189 4231 4512 4706)
+
+#include <cryptopp/modes.h>
+#include <cryptopp/nbtheory.h>
+#include <cryptopp/osrng.h>
+
+// Diffie-Hellman key agreement
+#include <cryptopp/dh.h>
+#include <cryptopp/dh2.h>
+
+// AES winner and candidates
+#include <cryptopp/aes.h>
+#include <cryptopp/cast.h>
+#include <cryptopp/rc6.h>
+#include <cryptopp/mars.h>
+#include <cryptopp/serpent.h>
+#include <cryptopp/twofish.h>
+// Other block ciphers
+#include <cryptopp/blowfish.h>
+#include <cryptopp/camellia.h>
+#include <cryptopp/des.h>
+#include <cryptopp/idea.h>
+#include <cryptopp/rc5.h>
+#include <cryptopp/seed.h>
+#include <cryptopp/shacal2.h>
+#include <cryptopp/skipjack.h>
+#include <cryptopp/tea.h>
+
+#ifdef __THEMIDA__
+#include <ThemidaSDK.h>
+#endif
+
+#include "Debug.h"
+
+
+using namespace CryptoPP;
+
+// Block cipher algorithm selector abstract base class.
+struct BlockCipherAlgorithm {
+	enum {
+		kDefault, // to give more chances to default algorithm
+		// AES winner and candidates
+//		kAES, // Rijndael
+		kRC6,
+		kMARS,
+		kTwofish,
+		kSerpent,
+		kCAST256,
+		// Other block ciphers
+		kIDEA,
+		k3DES, // DES-EDE2
+		kCamellia,
+		kSEED,
+		kRC5,
+		kBlowfish,
+		kTEA,
+		//kSKIPJACK,
+		kSHACAL2,
+		// End sentinel
+		kMaxAlgorithms
+	};
+
+	BlockCipherAlgorithm() {}
+	virtual ~BlockCipherAlgorithm() {}
+
+	static BlockCipherAlgorithm* Pick(int hint);
+
+	virtual int GetBlockSize() const = 0;
+	virtual int GetDefaultKeyLength() const = 0;
+	virtual int GetIVLength() const = 0;
+
+	virtual SymmetricCipher* CreateEncoder(const CryptoPP::byte* key, size_t keylen,
+		const CryptoPP::byte* iv) const = 0;
+	virtual SymmetricCipher* CreateDecoder(const CryptoPP::byte* key, size_t keylen,
+		const CryptoPP::byte* iv) const = 0;
+};
+
+// Block cipher (with CTR mode) algorithm selector template class.
+template<class T>
+struct BlockCipherDetail : public BlockCipherAlgorithm {
+	BlockCipherDetail() {}
+	virtual ~BlockCipherDetail() {}
+
+	virtual int GetBlockSize() const { return T::BLOCKSIZE; }
+	virtual int GetDefaultKeyLength() const { return T::DEFAULT_KEYLENGTH; }
+	virtual int GetIVLength() const { return T::IV_LENGTH; }
+
+	virtual SymmetricCipher* CreateEncoder(const CryptoPP::byte* key, size_t keylen,
+		const CryptoPP::byte* iv) const 
+	{
+		return new typename CTR_Mode<T>::Encryption(key, keylen, iv);
+	}
+	virtual SymmetricCipher* CreateDecoder(const CryptoPP::byte* key, size_t keylen,
+		const CryptoPP::byte* iv) const 
+	{
+		return new typename CTR_Mode<T>::Decryption(key, keylen, iv);
+	}
+};
+
+// Key agreement scheme abstract class.
+class KeyAgreement {
+public:
+	KeyAgreement() {}
+	virtual ~KeyAgreement() {}
+
+	virtual size_t Prepare(void* buffer, size_t* length) = 0;
+	virtual bool Agree(size_t agreed_length, const void* buffer, size_t length) = 0;
+
+	const SecByteBlock& shared() const { return shared_; }
+
+protected:
+	SecByteBlock shared_;
+};
+
+// Crypto++ Unified Diffie-Hellman key agreement scheme implementation.
+class DH2KeyAgreement : public KeyAgreement {
+public:
+	DH2KeyAgreement();
+	virtual ~DH2KeyAgreement();
+
+	virtual size_t Prepare(void* buffer, size_t* length);
+	virtual bool Agree(size_t agreed_length, const void* buffer, size_t length);
+
+private:
+	DH dh_;
+	DH2 dh2_;
+	SecByteBlock spriv_key_;
+	SecByteBlock epriv_key_;
+};
+
+Cipher::Cipher()
+: activated_(false), encoder_(NULL), decoder_(NULL), key_agreement_(NULL) {
+}
+
+Cipher::~Cipher() {
+	if (activated_) {
+		CleanUp();
+	}
+}
+
+void Cipher::CleanUp() {
+	if (encoder_ != NULL) {
+		delete encoder_;
+		encoder_ = NULL;
+	}
+	if (decoder_ != NULL) {
+		delete decoder_;
+		decoder_ = NULL;
+	}
+	if (key_agreement_ != NULL) {
+		delete key_agreement_;
+		key_agreement_ = NULL;
+	}
+	activated_ = false;
+}
+
+size_t Cipher::Prepare(void* buffer, size_t* length) {
+#ifdef __THEMIDA__
+	VM_START
+#endif
+
+	assert(key_agreement_ == NULL);
+	key_agreement_ = new DH2KeyAgreement();
+	assert(key_agreement_ != NULL);
+	size_t agreed_length = key_agreement_->Prepare(buffer, length);
+	if (agreed_length == 0) {
+		delete key_agreement_;
+		key_agreement_ = NULL;
+	}
+#ifdef __THEMIDA__
+	VM_END
+#endif
+
+	return agreed_length;
+}
+
+bool Cipher::Activate(bool polarity, size_t agreed_length,
+					  const void* buffer, size_t length) {
+#ifdef __THEMIDA__
+	VM_START
+#endif
+
+	assert(activated_ == false);
+	assert(key_agreement_ != NULL);
+	bool result = false;
+	if (key_agreement_->Agree(agreed_length, buffer, length)) {
+		result = SetUp(polarity);
+	}
+	delete key_agreement_;
+	key_agreement_ = NULL;
+#ifdef __THEMIDA__
+	VM_END
+#endif
+
+	return result;
+}
+
+bool Cipher::SetUp(bool polarity) {
+#ifdef __THEMIDA__
+	VM_START
+#endif
+
+	assert(key_agreement_ != NULL);
+	const SecByteBlock& shared = key_agreement_->shared();
+
+	// Pick a block cipher algorithm
+
+	if (shared.size() < 2) {
+		return false;
+	}
+
+	int hint_0 = shared.BytePtr()[*(shared.BytePtr()) % shared.size()];
+	int hint_1 = shared.BytePtr()[*(shared.BytePtr() + 1) % shared.size()];
+	BlockCipherAlgorithm* detail_0 = BlockCipherAlgorithm::Pick(hint_0);
+	BlockCipherAlgorithm* detail_1 = BlockCipherAlgorithm::Pick(hint_1);
+	assert(detail_0 != NULL);
+	assert(detail_1 != NULL);
+	std::unique_ptr<BlockCipherAlgorithm> algorithm_0(detail_0);
+	std::unique_ptr<BlockCipherAlgorithm> algorithm_1(detail_1);
+
+	const size_t key_length_0 = algorithm_0->GetDefaultKeyLength();
+	const size_t iv_length_0 = algorithm_0->GetBlockSize();
+
+	if (shared.size() < key_length_0 || shared.size() < iv_length_0) {
+		return false;
+	}
+
+	const size_t key_length_1 = algorithm_1->GetDefaultKeyLength();
+	const size_t iv_length_1 = algorithm_1->GetBlockSize();
+
+	if (shared.size() < key_length_1 || shared.size() < iv_length_1) {
+		return false;
+	}
+
+	// Pick encryption keys and initial vectors
+
+	SecByteBlock key_0(key_length_0), iv_0(iv_length_0);
+	SecByteBlock key_1(key_length_1), iv_1(iv_length_1);
+
+	size_t offset;
+
+	key_0.Assign(shared, key_length_0);
+	offset = key_length_0;
+	offset = min(key_length_0, shared.size() - key_length_1);
+	key_1.Assign(shared.BytePtr() + offset, key_length_1);
+
+	offset = shared.size() - iv_length_0;
+	iv_0.Assign(shared.BytePtr() + offset, iv_length_0);
+	offset = (offset < iv_length_1 ? 0 : offset - iv_length_1);
+	iv_1.Assign(shared.BytePtr() + offset, iv_length_1);
+
+	// Create encryption/decryption objects
+
+	if (polarity) {
+		encoder_ = algorithm_1->CreateEncoder(key_1, key_1.size(), iv_1);
+		decoder_ = algorithm_0->CreateDecoder(key_0, key_0.size(), iv_0);
+	} else {
+		encoder_ = algorithm_0->CreateEncoder(key_0, key_0.size(), iv_0);
+		decoder_ = algorithm_1->CreateDecoder(key_1, key_1.size(), iv_1);
+	}
+
+	assert(encoder_ != NULL);
+	assert(decoder_ != NULL);
+#ifdef __THEMIDA__
+	VM_END
+#endif
+
+	return true;
+}
+
+BlockCipherAlgorithm* BlockCipherAlgorithm::Pick(int hint) {
+	BlockCipherAlgorithm* detail;
+	int selector = hint % kMaxAlgorithms;
+	switch (selector) {
+	//case kAES:
+	//	detail = new BlockCipherDetail<AES>();
+		break;
+	case kRC6:
+		detail = new BlockCipherDetail<RC6>();
+		break;
+	case kMARS:
+		detail = new BlockCipherDetail<MARS>();
+		break;
+	case kTwofish:
+		detail = new BlockCipherDetail<Twofish>();
+		break;
+	case kSerpent:
+		detail = new BlockCipherDetail<Serpent>();
+		break;
+	case kCAST256:
+		detail = new BlockCipherDetail<CAST256>();
+		break;
+	case kIDEA:
+		detail = new BlockCipherDetail<IDEA>();
+		break;
+	case k3DES:
+		detail = new BlockCipherDetail<DES_EDE2>();
+		break;
+	case kCamellia:
+		detail = new BlockCipherDetail<Camellia>();
+		break;
+	case kSEED:
+		detail = new BlockCipherDetail<SEED>();
+		break;
+	case kRC5:
+		detail = new BlockCipherDetail<RC5>();
+		break;
+	case kBlowfish:
+		detail = new BlockCipherDetail<Blowfish>();
+		break;
+	case kTEA:
+		detail = new BlockCipherDetail<TEA>();
+		break;
+//	case kSKIPJACK:
+//		detail = new BlockCipherDetail<SKIPJACK>();
+//		break;
+	case kSHACAL2:
+		detail = new BlockCipherDetail<SHACAL2>();
+		break;
+	case kDefault:
+	default:
+		detail = new BlockCipherDetail<Twofish>(); // default algorithm
+		break;
+	}
+
+	return detail;
+}
+
+DH2KeyAgreement::DH2KeyAgreement() : dh_(), dh2_(dh_) {
+}
+
+DH2KeyAgreement::~DH2KeyAgreement() {
+}
+
+size_t DH2KeyAgreement::Prepare(void* buffer, size_t* length) {
+#ifdef __THEMIDA__
+	VM_START
+#endif
+
+	// RFC 5114, 1024-bit MODP Group with 160-bit Prime Order Subgroup
+	// http://tools.ietf.org/html/rfc5114#section-2.1
+	Integer p("0xB10B8F96A080E01DDE92DE5EAE5D54EC52C99FBCFB06A3C6"
+		"9A6A9DCA52D23B616073E28675A23D189838EF1E2EE652C0"
+		"13ECB4AEA906112324975C3CD49B83BFACCBDD7D90C4BD70"
+		"98488E9C219A73724EFFD6FAE5644738FAA31A4FF55BCCC0"
+		"A151AF5F0DC8B4BD45BF37DF365C1A65E68CFDA76D4DA708"
+		"DF1FB2BC2E4A4371");
+
+	Integer g("0xA4D1CBD5C3FD34126765A442EFB99905F8104DD258AC507F"
+		"D6406CFF14266D31266FEA1E5C41564B777E690F5504F213"
+		"160217B4B01B886A5E91547F9E2749F4D7FBD7D3B9A92EE1"
+		"909D0D2263F80A76A6A24C087A091F531DBF0A0169B6A28A"
+		"D662A4D18E73AFA32D779D5918D08BC8858F4DCEF97C2A24"
+		"855E6EEB22B3B2E5");
+
+	Integer q("0xF518AA8781A8DF278ABA4E7D64B7CB9D49462353");
+
+	// Schnorr Group primes are of the form p = rq + 1, p and q prime. They
+	// provide a subgroup order. In the case of 1024-bit MODP Group, the
+	// security level is 80 bits (based on the 160-bit prime order subgroup).		
+
+	// For a compare/contrast of using the maximum security level, see
+	// dh-unified.zip. Also see http://www.cryptopp.com/wiki/Diffie-Hellman
+	// and http://www.cryptopp.com/wiki/Security_level .
+
+	AutoSeededRandomPool rnd;
+
+	dh_.AccessGroupParameters().Initialize(p, q, g);
+
+	if(!dh_.GetGroupParameters().ValidateGroup(rnd, 3)) {
+		// Failed to validate prime and generator
+		return 0;
+	}
+
+	size_t count = 0;
+
+	p = dh_.GetGroupParameters().GetModulus();
+	q = dh_.GetGroupParameters().GetSubgroupOrder();
+	g = dh_.GetGroupParameters().GetGenerator();
+
+	// http://groups.google.com/group/sci.crypt/browse_thread/thread/7dc7eeb04a09f0ce
+	Integer v = ModularExponentiation(g, q, p);
+
+	if(v != Integer::One()) {
+		// Failed to verify order of the subgroup
+		return 0;
+	}
+
+	//////////////////////////////////////////////////////////////
+
+	spriv_key_.New(dh2_.StaticPrivateKeyLength());
+	epriv_key_.New(dh2_.EphemeralPrivateKeyLength());
+	SecByteBlock spub_key(dh2_.StaticPublicKeyLength());
+	SecByteBlock epub_key(dh2_.EphemeralPublicKeyLength());
+
+	dh2_.GenerateStaticKeyPair(rnd, spriv_key_, spub_key);
+	dh2_.GenerateEphemeralKeyPair(rnd, epriv_key_, epub_key);
+
+	// Prepare key agreement data
+	const size_t spub_key_length = spub_key.size();
+	const size_t epub_key_length = epub_key.size();
+	const size_t data_length = spub_key_length + epub_key_length;
+
+	if (*length < data_length) {
+		// Not enough data buffer length b-l-a-c-k
+		return 0;
+	}
+
+	*length = data_length;
+	CryptoPP::byte* buf = (CryptoPP::byte*)buffer;
+	memcpy(buf, spub_key.BytePtr(), spub_key_length);
+	memcpy(buf + spub_key_length, epub_key.BytePtr(), epub_key_length);
+
+#ifdef __THEMIDA__
+	VM_END
+#endif
+
+	return dh2_.AgreedValueLength();
+}
+
+bool DH2KeyAgreement::Agree(size_t agreed_length, const void* buffer, size_t length) {
+	if (agreed_length != dh2_.AgreedValueLength()) {
+		// Shared secret size mismatch
+		return false;
+	}
+	const size_t spub_key_length = dh2_.StaticPublicKeyLength();
+	const size_t epub_key_length = dh2_.EphemeralPublicKeyLength();
+	if (length != (spub_key_length + epub_key_length)) {
+		// Wrong data length
+		return false;
+	}
+	shared_.New(dh2_.AgreedValueLength());
+	const CryptoPP::byte* buf = (const CryptoPP::byte*)buffer;
+	if (!dh2_.Agree(shared_, spriv_key_, epriv_key_, buf, buf + spub_key_length)) {
+		// Failed to reach shared secret
+		return false;
+	}
+	return true;
+}
+
+#endif

extension/src/port/EterLib/NetAddress.cpp

@@ -0,0 +1,107 @@
+#include "StdAfx.h"
+#include "NetAddress.h"
+
+#ifndef VC_EXTRALEAN
+
+bool CNetworkAddress::GetHostName(char* szName, int size)
+{
+	if (gethostname(szName, size)==SOCKET_ERROR)
+		return false;
+	return true;
+}
+
+CNetworkAddress::CNetworkAddress()
+{
+	Clear();
+}
+
+CNetworkAddress::~CNetworkAddress()
+{
+}
+
+CNetworkAddress::operator const SOCKADDR_IN&() const
+{
+	return m_sockAddrIn;
+}
+
+void CNetworkAddress::Clear()
+{
+	memset(&m_sockAddrIn, 0, sizeof(m_sockAddrIn));
+	m_sockAddrIn.sin_family=AF_INET;
+}
+
+bool CNetworkAddress::IsIP(const char* c_szAddr)
+{
+	if (c_szAddr[0]<'0' || c_szAddr[0]>'9')
+		return false;
+	return true;
+}
+
+bool CNetworkAddress::Set(const char* c_szAddr, int port)
+{
+	if (IsIP(c_szAddr))
+	{
+		SetIP(c_szAddr);
+	}
+	else
+	{
+		if (!SetDNS(c_szAddr))
+			return false;
+	}
+
+	SetPort(port);
+	return true;
+}
+
+void CNetworkAddress::SetLocalIP()
+{
+	SetIP(INADDR_ANY);	
+}
+
+void CNetworkAddress::SetIP(DWORD ip)
+{
+	m_sockAddrIn.sin_addr.s_addr=htonl(ip);
+}
+
+void CNetworkAddress::SetIP(const char* c_szIP)
+{
+	m_sockAddrIn.sin_addr.s_addr=inet_addr(c_szIP);
+}
+
+bool CNetworkAddress::SetDNS(const char* c_szDNS)
+{
+	HOSTENT* pHostent=gethostbyname(c_szDNS);
+	if (!pHostent) return false;
+	memcpy(&m_sockAddrIn.sin_addr, pHostent->h_addr, sizeof(m_sockAddrIn.sin_addr));
+	return true;
+}
+
+void CNetworkAddress::SetPort(int port)
+{
+	m_sockAddrIn.sin_port = htons(port);
+}
+
+int CNetworkAddress::GetSize()
+{
+	return sizeof(m_sockAddrIn);
+}
+
+DWORD CNetworkAddress::GetIP()
+{
+	return ntohl(m_sockAddrIn.sin_addr.s_addr);
+}
+
+void CNetworkAddress::GetIP(char* szIP, int len)
+{
+	BYTE IPs[4];
+	*((DWORD*)IPs)=m_sockAddrIn.sin_addr.s_addr;
+
+	_snprintf(szIP, len, "%d.%d.%d.%d", IPs[0], IPs[1], IPs[2], IPs[3]);
+}
+			
+int CNetworkAddress::GetPort()
+{
+	return ntohs(m_sockAddrIn.sin_port);
+}
+
+#endif

extension/src/port/EterLib/NetDevice.cpp

@@ -0,0 +1,41 @@
+#include "StdAfx.h"
+#include "NetDevice.h"
+
+CNetworkDevice::CNetworkDevice()
+{
+	Initialize();
+}
+
+CNetworkDevice::~CNetworkDevice()
+{
+	Destroy();	
+}
+
+void CNetworkDevice::Initialize()
+{
+	m_isWSA=false;
+}
+
+void CNetworkDevice::Destroy()
+{
+	if (m_isWSA)
+	{
+		WSACleanup();
+		m_isWSA=false;
+	}
+}
+
+bool CNetworkDevice::Create()
+{
+	Destroy();
+
+	Initialize();
+
+	WSADATA wsaData;
+	if (WSAStartup(MAKEWORD(1, 1), &wsaData)!=0)
+		return false;
+
+	m_isWSA=true;
+	
+	return true;
+}

extension/src/port/EterLib/NetPacketHeaderMap.cpp

@@ -0,0 +1,26 @@
+#include "StdAfx.h"
+#include "NetPacketHeaderMap.h"
+
+void CNetworkPacketHeaderMap::Set(int header, TPacketType rPacketType)
+{
+	m_headerMap[header] = rPacketType;
+}
+bool CNetworkPacketHeaderMap::Get(int header, TPacketType * pPacketType)
+{
+	std::map<int, TPacketType>::iterator f=m_headerMap.find(header);
+	
+	if (m_headerMap.end()==f)
+		return false;
+	
+	*pPacketType = f->second;
+
+	return true;
+}
+
+CNetworkPacketHeaderMap::CNetworkPacketHeaderMap()
+{
+}
+
+CNetworkPacketHeaderMap::~CNetworkPacketHeaderMap()
+{
+}

extension/src/port/common/shim/win32/winsock.h

@@ -1,14 +1,75 @@
 #pragma once
-// Shim for <winsock.h> on non-Windows targets: the BSD socket types under their Winsock names.
+// Shim for <winsock.h> on non-Windows targets: the BSD socket API under its Winsock names, with the
+// Winsock semantics 40250 relies on where the two differ (see the notes on each function).
 #include "windows.h"
 
 #include <arpa/inet.h>
+#include <errno.h>
+#include <netdb.h>
 #include <netinet/in.h>
+#include <signal.h>
+#include <sys/ioctl.h>
+#include <sys/select.h>
 #include <sys/socket.h>
+#include <sys/time.h>
+#include <unistd.h>
 
 typedef int SOCKET;
 typedef struct sockaddr SOCKADDR;
+typedef struct sockaddr* PSOCKADDR;
 typedef struct sockaddr_in SOCKADDR_IN;
 typedef struct in_addr IN_ADDR;
+typedef struct timeval TIMEVAL;
+typedef struct hostent HOSTENT;
 #define INVALID_SOCKET (-1)
 #define SOCKET_ERROR (-1)
+#define WSAEWOULDBLOCK EWOULDBLOCK
+
+typedef struct WSAData
+{
+	WORD wVersion;
+	WORD wHighVersion;
+} WSADATA;
+
+// There is no Winsock DLL to start. A send on a socket the peer has closed raises SIGPIPE on POSIX
+// where Winsock returns an error, so the process ignores it from here on.
+inline int WSAStartup(WORD version, WSADATA* data)
+{
+	signal(SIGPIPE, SIG_IGN);
+	if (data)
+		data->wVersion = data->wHighVersion = version;
+	return 0;
+}
+inline int WSACleanup() { return 0; }
+
+// A non-blocking connect() answers WSAEWOULDBLOCK on Winsock and EINPROGRESS on POSIX.
+inline int WSAGetLastError() { return errno == EINPROGRESS ? WSAEWOULDBLOCK : errno; }
+
+inline int closesocket(SOCKET s) { return close(s); }
+
+inline int ioctlsocket(SOCKET s, long cmd, DWORD* argp)
+{
+	int value = static_cast<int>(*argp);
+	return ioctl(s, static_cast<unsigned long>(cmd), &value);
+}
+
+// Winsock ignores nfds, and a socket whose connect failed is reported only in exceptfds; POSIX needs
+// nfds and marks such a socket writable. Callers pass 0 and treat "writable" as "connected"
+// (CNetworkStream::Process), so writable sockets without a peer are dropped from the write set.
+inline int mt_winsock_select(fd_set* readfds, fd_set* writefds, fd_set* exceptfds, TIMEVAL* timeout)
+{
+	int ret = ::select(FD_SETSIZE, readfds, writefds, exceptfds, timeout);
+	if (ret <= 0 || !writefds)
+		return ret;
+	for (int fd = 0; fd < FD_SETSIZE; ++fd)
+	{
+		if (!FD_ISSET(fd, writefds))
+			continue;
+		sockaddr_in peer;
+		socklen_t len = sizeof(peer);
+		if (getpeername(fd, reinterpret_cast<sockaddr*>(&peer), &len) != 0)
+			FD_CLR(fd, writefds);
+	}
+	return ret;
+}
+#define select(nfds, readfds, writefds, exceptfds, timeout) mt_winsock_select(readfds, writefds, exceptfds, timeout)