Windows 10 TCP fast open sample

win-tfo.cpp

#include <stdio.h>
#include <WinSock2.h>
#include <MSWSock.h>
#include <WS2tcpip.h>

#pragma comment(lib, "Ws2_32.lib")


static LPFN_CONNECTEX ConnectEx = NULL;

static BOOL load_mswsock(void) {
    /* Dummy socket needed for WSAIoctl */
    SOCKET sock = socket(AF_INET, SOCK_STREAM, 0);
    if (sock == INVALID_SOCKET)
        return FALSE;

	GUID guid = WSAID_CONNECTEX;
    DWORD dwBytes;
	if (WSAIoctl(sock, SIO_GET_EXTENSION_FUNCTION_POINTER,
		&guid, sizeof(guid),
		&ConnectEx, sizeof(ConnectEx),
		&dwBytes, NULL, NULL) != 0)
		return FALSE;

    closesocket(sock);
    return TRUE;
}

int main(int argc, char *argv[]) {
    WSADATA wsaData;
    if (WSAStartup(MAKEWORD(2,2), &wsaData) != 0) {
        printf("WSAStartup failed");
        return 1;
    }

    if (!load_mswsock()) {
        printf("Error loading mswsock functions: %d\n", WSAGetLastError());
        return 1;
    }

    SOCKET sock = socket(AF_INET, SOCK_STREAM, 0);
    if (sock == INVALID_SOCKET) {
        printf("socket: %d\n", WSAGetLastError());
        return 1;
    }

	char optVal = TRUE;
	if (setsockopt(sock, IPPROTO_TCP, TCP_FASTOPEN, &optVal, sizeof(optVal)) != 0) {
		printf("setsockopt failed: %d\n", WSAGetLastError());
		return 1;
	}

    /* ConnectEx requires the socket to be initially bound. */
	sockaddr_in addr;
	ZeroMemory(&addr, sizeof(addr));
	addr.sin_family = AF_INET;
	addr.sin_addr.s_addr = INADDR_ANY;
	addr.sin_port = 0;
	if (bind(sock, (SOCKADDR*) &addr, sizeof(addr)) != 0) {
		printf("bind failed: %d\n", WSAGetLastError());
		return 1;
	}

    /* Issue ConnectEx and wait for the operation to complete. */
	OVERLAPPED ol;
	ZeroMemory(&ol, sizeof(ol));

	// 198.35.26.96  en.wikipedia
	inet_pton(AF_INET, "172.93.41.174", &addr.sin_addr.s_addr);
	addr.sin_port = htons(80);

	BYTE dat[] = "GET / HTTP/1.0\n\n";
	DWORD bytesSent;
	BOOL ok = ConnectEx(sock, (SOCKADDR*) &addr, sizeof(addr), dat, sizeof(dat)-1, &bytesSent, &ol);
	if (ok) {
		printf("ConnectEx succeeded immediately\n");
	} else if (WSAGetLastError() == ERROR_IO_PENDING) {
		ok = GetOverlappedResult((HANDLE) sock, &ol, &bytesSent, TRUE);
		printf("ConnectEx pending\n");

		if (!ok)
			printf("ConnectEx failed: %d\n", WSAGetLastError());
	} else {
		printf("ConnectEx failed: %d\n", WSAGetLastError());
		return 1;
	}
  	char buf[4096];
  	recv(sock, buf, 4096, 0);

    closesocket(sock);
  	WSACleanup();

    printf("Done\n");
    return 0;
}

连维基百科的443端口成功几率挺大的
然而连我自己服务器的80端口经常出现莫名其妙的延时3秒才回http响应，还有相当大的几率SYN+PSH包丢掉，fallback到传统三次握手。
更让人心寒的是SoftEther VPN内嵌的NAT造成tfo的第一个包100%被丢，然后windows会自动禁用tfo。断开vpn也不会马上恢复

这破玩意儿根本不能用嘛