This patch adds the selftests support for mptfo in mptcp_connect.c
We introduce mptfo option, that sets "TCP_FASTOPEN" + "MSG_FASTOPEN"
We call sendto() instead of connect().

Signed-off-by: Dmytro Shytyi <dmytro@shytyi.net>
---
 .../selftests/net/mptcp/mptcp_connect.c       | 121 +++++++++++++-----
 .../selftests/net/mptcp/mptcp_connect.sh      |  21 +++
 2 files changed, 113 insertions(+), 29 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.c b/tools/testing/selftests/net/mptcp/mptcp_connect.c
index e54653ea2ed4..4bc855159c52 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_connect.c
+++ b/tools/testing/selftests/net/mptcp/mptcp_connect.c
@@ -26,11 +26,13 @@
 
 #include <netdb.h>
 #include <netinet/in.h>
+#include <netinet/tcp.h>
 
-#include <linux/tcp.h>
 #include <linux/time_types.h>
 #include <linux/sockios.h>
 
+
+
 extern int optind;
 
 #ifndef IPPROTO_MPTCP
@@ -83,6 +85,7 @@ struct cfg_cmsg_types {
 
 struct cfg_sockopt_types {
 	unsigned int transparent:1;
+	unsigned int mptfo:1;
 };
 
 struct tcp_inq_state {
@@ -232,6 +235,14 @@ static void set_transparent(int fd, int pf)
 	}
 }
 
+static void set_mptfo(int fd, int pf)
+{
+	int qlen = 25;
+
+	if (setsockopt(fd, SOL_TCP, TCP_FASTOPEN, &qlen, sizeof(qlen)) == -1)
+		perror("TCP_FASTOPEN");
+}
+
 static int do_ulp_so(int sock, const char *name)
 {
 	return setsockopt(sock, IPPROTO_TCP, TCP_ULP, name, strlen(name));
@@ -300,6 +311,9 @@ static int sock_listen_mptcp(const char * const listenaddr,
 		if (cfg_sockopt_types.transparent)
 			set_transparent(sock, pf);
 
+		if (cfg_sockopt_types.mptfo)
+			set_mptfo(sock, pf);
+
 		if (bind(sock, a->ai_addr, a->ai_addrlen) == 0)
 			break; /* success */
 
@@ -330,13 +344,18 @@ static int sock_listen_mptcp(const char * const listenaddr,
 
 static int sock_connect_mptcp(const char * const remoteaddr,
 			      const char * const port, int proto,
-			      struct addrinfo **peer)
+			      struct addrinfo **peer,
+			      int infd,
+			      unsigned int *woff)
 {
 	struct addrinfo hints = {
 		.ai_protocol = IPPROTO_TCP,
 		.ai_socktype = SOCK_STREAM,
 	};
 	struct addrinfo *a, *addr;
+	unsigned int wlen = 0;
+	int syn_copied = 0;
+	char wbuf[8192];
 	int sock = -1;
 
 	hints.ai_family = pf;
@@ -354,14 +373,33 @@ static int sock_connect_mptcp(const char * const remoteaddr,
 		if (cfg_mark)
 			set_mark(sock, cfg_mark);
 
-		if (connect(sock, a->ai_addr, a->ai_addrlen) == 0) {
-			*peer = a;
-			break; /* success */
-		}
+		if (cfg_sockopt_types.mptfo) {
+			if (wlen == 0)
+				wlen = read(infd, wbuf, sizeof(wbuf));
 
-		perror("connect()");
-		close(sock);
-		sock = -1;
+			syn_copied = sendto(sock, wbuf, wlen, MSG_FASTOPEN,
+					    a->ai_addr, a->ai_addrlen);
+			if (syn_copied) {
+				*woff = wlen;
+				*peer = a;
+				break; /* success */
+			}
+		} else {
+			if (connect(sock, a->ai_addr, a->ai_addrlen) == 0) {
+				*peer = a;
+				break; /* success */
+			}
+		}
+		if (cfg_sockopt_types.mptfo) {
+			perror("sendto()");
+			close(sock);
+			sock = -1;
+		} else {
+
+			perror("connect()");
+			close(sock);
+			sock = -1;
+		}
 	}
 
 	freeaddrinfo(addr);
@@ -571,13 +609,14 @@ static void shut_wr(int fd)
 	shutdown(fd, SHUT_WR);
 }
 
-static int copyfd_io_poll(int infd, int peerfd, int outfd, bool *in_closed_after_out)
+static int copyfd_io_poll(int infd, int peerfd, int outfd,
+			  bool *in_closed_after_out, unsigned int woff)
 {
 	struct pollfd fds = {
 		.fd = peerfd,
 		.events = POLLIN | POLLOUT,
 	};
-	unsigned int woff = 0, wlen = 0, total_wlen = 0, total_rlen = 0;
+	unsigned int wlen = 0, total_wlen = 0, total_rlen = 0;
 	char wbuf[8192];
 
 	set_nonblock(peerfd, true);
@@ -839,7 +878,7 @@ static int copyfd_io_sendfile(int infd, int peerfd, int outfd,
 	return err;
 }
 
-static int copyfd_io(int infd, int peerfd, int outfd, bool close_peerfd)
+static int copyfd_io(int infd, int peerfd, int outfd, bool close_peerfd, unsigned int woff)
 {
 	bool in_closed_after_out = false;
 	struct timespec start, end;
@@ -851,7 +890,7 @@ static int copyfd_io(int infd, int peerfd, int outfd, bool close_peerfd)
 
 	switch (cfg_mode) {
 	case CFG_MODE_POLL:
-		ret = copyfd_io_poll(infd, peerfd, outfd, &in_closed_after_out);
+		ret = copyfd_io_poll(infd, peerfd, outfd, &in_closed_after_out, woff);
 		break;
 
 	case CFG_MODE_MMAP:
@@ -1033,7 +1072,7 @@ int main_loop_s(int listensock)
 
 		SOCK_TEST_TCPULP(remotesock, 0);
 
-		copyfd_io(fd, remotesock, 1, true);
+		copyfd_io(fd, remotesock, 1, true, 0);
 	} else {
 		perror("accept");
 		return 1;
@@ -1130,6 +1169,11 @@ static void parse_setsock_options(const char *name)
 		return;
 	}
 
+	if (strncmp(name, "MPTFO", len) == 0) {
+		cfg_sockopt_types.mptfo = 1;
+		return;
+	}
+
 	fprintf(stderr, "Unrecognized setsockopt option %s\n", name);
 	exit(1);
 }
@@ -1168,23 +1212,25 @@ int main_loop(void)
 {
 	int fd, ret, fd_in = 0;
 	struct addrinfo *peer;
+	unsigned int woff = 0;
 
-	/* listener is ready. */
-	fd = sock_connect_mptcp(cfg_host, cfg_port, cfg_sock_proto, &peer);
-	if (fd < 0)
-		return 2;
-
+	if (!cfg_sockopt_types.mptfo) {
+		/* listener is ready. */
+		fd = sock_connect_mptcp(cfg_host, cfg_port, cfg_sock_proto, &peer, 0, 0);
+		if (fd < 0)
+			return 2;
 again:
-	check_getpeername_connect(fd);
+		check_getpeername_connect(fd);
 
-	SOCK_TEST_TCPULP(fd, cfg_sock_proto);
+		SOCK_TEST_TCPULP(fd, cfg_sock_proto);
 
-	if (cfg_rcvbuf)
-		set_rcvbuf(fd, cfg_rcvbuf);
-	if (cfg_sndbuf)
-		set_sndbuf(fd, cfg_sndbuf);
-	if (cfg_cmsg_types.cmsg_enabled)
-		apply_cmsg_types(fd, &cfg_cmsg_types);
+		if (cfg_rcvbuf)
+			set_rcvbuf(fd, cfg_rcvbuf);
+		if (cfg_sndbuf)
+			set_sndbuf(fd, cfg_sndbuf);
+		if (cfg_cmsg_types.cmsg_enabled)
+			apply_cmsg_types(fd, &cfg_cmsg_types);
+	}
 
 	if (cfg_input) {
 		fd_in = open(cfg_input, O_RDONLY);
@@ -1192,8 +1238,25 @@ int main_loop(void)
 			xerror("can't open %s:%d", cfg_input, errno);
 	}
 
-	/* close the client socket open only if we are not going to reconnect */
-	ret = copyfd_io(fd_in, fd, 1, 0);
+	if (cfg_sockopt_types.mptfo) {
+		/* sendto() instead of connect */
+		fd = sock_connect_mptcp(cfg_host, cfg_port, cfg_sock_proto, &peer, fd_in, &woff);
+		if (fd < 0)
+			return 2;
+
+		check_getpeername_connect(fd);
+
+		SOCK_TEST_TCPULP(fd, cfg_sock_proto);
+
+		if (cfg_rcvbuf)
+			set_rcvbuf(fd, cfg_rcvbuf);
+		if (cfg_sndbuf)
+			set_sndbuf(fd, cfg_sndbuf);
+		if (cfg_cmsg_types.cmsg_enabled)
+			apply_cmsg_types(fd, &cfg_cmsg_types);
+	}
+
+	ret = copyfd_io(fd_in, fd, 1, 0, 0);
 	if (ret)
 		return ret;
 
diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.sh b/tools/testing/selftests/net/mptcp/mptcp_connect.sh
index 621af6895f4d..60198b91a530 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_connect.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_connect.sh
@@ -762,6 +762,23 @@ run_tests_peekmode()
 	run_tests_lo "$ns1" "$ns1" dead:beef:1::1 1 "-P ${peekmode}"
 }
 
+run_tests_mptfo()
+{
+	echo "INFO: with MPTFO start"
+	ip netns exec "$ns1" sysctl -q net.ipv4.tcp_fastopen=2
+	ip netns exec "$ns2" sysctl -q net.ipv4.tcp_fastopen=1
+
+	run_tests_lo "$ns1" "$ns2" 10.0.1.1 0 "-o MPTFO"
+	run_tests_lo "$ns1" "$ns2" 10.0.1.1 0 "-o MPTFO"
+
+	run_tests_lo "$ns1" "$ns2" dead:beef:1::1 0 "-o MPTFO"
+	run_tests_lo "$ns1" "$ns2" dead:beef:1::1 0 "-o MPTFO"
+
+	ip netns exec "$ns1" sysctl -q net.ipv4.tcp_fastopen=0
+	ip netns exec "$ns2" sysctl -q net.ipv4.tcp_fastopen=0
+	echo "INFO: with MPTFO end"
+}
+
 run_tests_disconnect()
 {
 	local peekmode="$1"
@@ -901,6 +918,10 @@ run_tests_peekmode "saveWithPeek"
 run_tests_peekmode "saveAfterPeek"
 stop_if_error "Tests with peek mode have failed"
 
+# MPTFO (MultiPath TCP Fatopen tests)
+run_tests_mptfo
+stop_if_error "Tests with MPTFO have failed"
+
 # connect to ns4 ip address, ns2 should intercept/proxy
 run_test_transparent 10.0.3.1 "tproxy ipv4"
 run_test_transparent dead:beef:3::1 "tproxy ipv6"
-- 
2.34.1

On Sun, 2022-11-06 at 15:24 +0000, Dmytro Shytyi wrote:
> This patch adds the selftests support for mptfo in mptcp_connect.c
> We introduce mptfo option, that sets "TCP_FASTOPEN" + "MSG_FASTOPEN"
> We call sendto() instead of connect().
> 
> Signed-off-by: Dmytro Shytyi <dmytro@shytyi.net>
> ---
>  .../selftests/net/mptcp/mptcp_connect.c       | 121 +++++++++++++-----
>  .../selftests/net/mptcp/mptcp_connect.sh      |  21 +++
>  2 files changed, 113 insertions(+), 29 deletions(-)
> 
> diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.c b/tools/testing/selftests/net/mptcp/mptcp_connect.c
> index e54653ea2ed4..4bc855159c52 100644
> --- a/tools/testing/selftests/net/mptcp/mptcp_connect.c
> +++ b/tools/testing/selftests/net/mptcp/mptcp_connect.c
> @@ -26,11 +26,13 @@
>  
>  #include <netdb.h>
>  #include <netinet/in.h>
> +#include <netinet/tcp.h>
>  
> -#include <linux/tcp.h>

Funnily enough, the above change breaks the build on my host. I see the
CI does not complain about it, but I still would avoid it

>  #include <linux/time_types.h>
>  #include <linux/sockios.h>
>  
> +
> +

Unneeded empty lines, do not add them

>  extern int optind;
>  
>  #ifndef IPPROTO_MPTCP
> @@ -83,6 +85,7 @@ struct cfg_cmsg_types {
>  
>  struct cfg_sockopt_types {
>  	unsigned int transparent:1;
> +	unsigned int mptfo:1;
>  };
>  
>  struct tcp_inq_state {
> @@ -232,6 +235,14 @@ static void set_transparent(int fd, int pf)
>  	}
>  }
>  
> +static void set_mptfo(int fd, int pf)
> +{
> +	int qlen = 25;
> +
> +	if (setsockopt(fd, SOL_TCP, TCP_FASTOPEN, &qlen, sizeof(qlen)) == -1)

If you use IPPROTO_TCP here instead of SOL_TCP - yep, it's not what the
man page says - you can avoid the initial problematic chunck

> +		perror("TCP_FASTOPEN");
> +}
> +
>  static int do_ulp_so(int sock, const char *name)
>  {
>  	return setsockopt(sock, IPPROTO_TCP, TCP_ULP, name, strlen(name));
> @@ -300,6 +311,9 @@ static int sock_listen_mptcp(const char * const listenaddr,
>  		if (cfg_sockopt_types.transparent)
>  			set_transparent(sock, pf);
>  
> +		if (cfg_sockopt_types.mptfo)
> +			set_mptfo(sock, pf);
> +
>  		if (bind(sock, a->ai_addr, a->ai_addrlen) == 0)
>  			break; /* success */
>  
> @@ -330,13 +344,18 @@ static int sock_listen_mptcp(const char * const listenaddr,
>  
>  static int sock_connect_mptcp(const char * const remoteaddr,
>  			      const char * const port, int proto,
> -			      struct addrinfo **peer)
> +			      struct addrinfo **peer,
> +			      int infd,
> +			      unsigned int *woff)
>  {
>  	struct addrinfo hints = {
>  		.ai_protocol = IPPROTO_TCP,
>  		.ai_socktype = SOCK_STREAM,
>  	};
>  	struct addrinfo *a, *addr;
> +	unsigned int wlen = 0;
> +	int syn_copied = 0;
> +	char wbuf[8192];
>  	int sock = -1;
>  
>  	hints.ai_family = pf;
> @@ -354,14 +373,33 @@ static int sock_connect_mptcp(const char * const remoteaddr,
>  		if (cfg_mark)
>  			set_mark(sock, cfg_mark);
>  
> -		if (connect(sock, a->ai_addr, a->ai_addrlen) == 0) {
> -			*peer = a;
> -			break; /* success */
> -		}
> +		if (cfg_sockopt_types.mptfo) {
> +			if (wlen == 0)
> +				wlen = read(infd, wbuf, sizeof(wbuf));
>  
> -		perror("connect()");
> -		close(sock);
> -		sock = -1;
> +			syn_copied = sendto(sock, wbuf, wlen, MSG_FASTOPEN,
> +					    a->ai_addr, a->ai_addrlen);
> +			if (syn_copied) {
> +				*woff = wlen;

This is likely causing the self-test failures. syn_copied can be lower
than wlen - or even negative. You must check for errors, and save the
exact amount of bytes copied. Additionally you need to preserve wbuf
contents, or read but unsent bytes will be lost.

I'll try to send an incremental patch asap.

> +				*peer = a;
> +				break; /* success */
> +			}
> +		} else {
> +			if (connect(sock, a->ai_addr, a->ai_addrlen) == 0) {
> +				*peer = a;
> +				break; /* success */
> +			}
> +		}
> +		if (cfg_sockopt_types.mptfo) {
> +			perror("sendto()");
> +			close(sock);
> +			sock = -1;
> +		} else {
> +
> +			perror("connect()");
> +			close(sock);
> +			sock = -1;
> +		}
>  	}
>  
>  	freeaddrinfo(addr);
> @@ -571,13 +609,14 @@ static void shut_wr(int fd)
>  	shutdown(fd, SHUT_WR);
>  }
>  
> -static int copyfd_io_poll(int infd, int peerfd, int outfd, bool *in_closed_after_out)
> +static int copyfd_io_poll(int infd, int peerfd, int outfd,
> +			  bool *in_closed_after_out, unsigned int woff)
>  {
>  	struct pollfd fds = {
>  		.fd = peerfd,
>  		.events = POLLIN | POLLOUT,
>  	};
> -	unsigned int woff = 0, wlen = 0, total_wlen = 0, total_rlen = 0;
> +	unsigned int wlen = 0, total_wlen = 0, total_rlen = 0;
>  	char wbuf[8192];
>  
>  	set_nonblock(peerfd, true);
> @@ -839,7 +878,7 @@ static int copyfd_io_sendfile(int infd, int peerfd, int outfd,
>  	return err;
>  }
>  
> -static int copyfd_io(int infd, int peerfd, int outfd, bool close_peerfd)
> +static int copyfd_io(int infd, int peerfd, int outfd, bool close_peerfd, unsigned int woff)
>  {
>  	bool in_closed_after_out = false;
>  	struct timespec start, end;
> @@ -851,7 +890,7 @@ static int copyfd_io(int infd, int peerfd, int outfd, bool close_peerfd)
>  
>  	switch (cfg_mode) {
>  	case CFG_MODE_POLL:
> -		ret = copyfd_io_poll(infd, peerfd, outfd, &in_closed_after_out);
> +		ret = copyfd_io_poll(infd, peerfd, outfd, &in_closed_after_out, woff);
>  		break;
>  
>  	case CFG_MODE_MMAP:
> @@ -1033,7 +1072,7 @@ int main_loop_s(int listensock)
>  
>  		SOCK_TEST_TCPULP(remotesock, 0);
>  
> -		copyfd_io(fd, remotesock, 1, true);
> +		copyfd_io(fd, remotesock, 1, true, 0);
>  	} else {
>  		perror("accept");
>  		return 1;
> @@ -1130,6 +1169,11 @@ static void parse_setsock_options(const char *name)
>  		return;
>  	}
>  
> +	if (strncmp(name, "MPTFO", len) == 0) {
> +		cfg_sockopt_types.mptfo = 1;
> +		return;
> +	}
> +
>  	fprintf(stderr, "Unrecognized setsockopt option %s\n", name);
>  	exit(1);
>  }
> @@ -1168,23 +1212,25 @@ int main_loop(void)
>  {
>  	int fd, ret, fd_in = 0;
>  	struct addrinfo *peer;
> +	unsigned int woff = 0;
>  
> -	/* listener is ready. */
> -	fd = sock_connect_mptcp(cfg_host, cfg_port, cfg_sock_proto, &peer);
> -	if (fd < 0)
> -		return 2;
> -
> +	if (!cfg_sockopt_types.mptfo) {
> +		/* listener is ready. */
> +		fd = sock_connect_mptcp(cfg_host, cfg_port, cfg_sock_proto, &peer, 0, 0);
> +		if (fd < 0)
> +			return 2;
>  again:
> -	check_getpeername_connect(fd);
> +		check_getpeername_connect(fd);
>  
> -	SOCK_TEST_TCPULP(fd, cfg_sock_proto);
> +		SOCK_TEST_TCPULP(fd, cfg_sock_proto);
>  
> -	if (cfg_rcvbuf)
> -		set_rcvbuf(fd, cfg_rcvbuf);
> -	if (cfg_sndbuf)
> -		set_sndbuf(fd, cfg_sndbuf);
> -	if (cfg_cmsg_types.cmsg_enabled)
> -		apply_cmsg_types(fd, &cfg_cmsg_types);
> +		if (cfg_rcvbuf)
> +			set_rcvbuf(fd, cfg_rcvbuf);
> +		if (cfg_sndbuf)
> +			set_sndbuf(fd, cfg_sndbuf);
> +		if (cfg_cmsg_types.cmsg_enabled)
> +			apply_cmsg_types(fd, &cfg_cmsg_types);
> +	}
>  
>  	if (cfg_input) {
>  		fd_in = open(cfg_input, O_RDONLY);
> @@ -1192,8 +1238,25 @@ int main_loop(void)
>  			xerror("can't open %s:%d", cfg_input, errno);
>  	}
>  
> -	/* close the client socket open only if we are not going to reconnect */
> -	ret = copyfd_io(fd_in, fd, 1, 0);
> +	if (cfg_sockopt_types.mptfo) {
> +		/* sendto() instead of connect */
> +		fd = sock_connect_mptcp(cfg_host, cfg_port, cfg_sock_proto, &peer, fd_in, &woff);
> +		if (fd < 0)
> +			return 2;
> +
> +		check_getpeername_connect(fd);
> +
> +		SOCK_TEST_TCPULP(fd, cfg_sock_proto);
> +
> +		if (cfg_rcvbuf)
> +			set_rcvbuf(fd, cfg_rcvbuf);
> +		if (cfg_sndbuf)
> +			set_sndbuf(fd, cfg_sndbuf);
> +		if (cfg_cmsg_types.cmsg_enabled)
> +			apply_cmsg_types(fd, &cfg_cmsg_types);
> +	}
> +
> +	ret = copyfd_io(fd_in, fd, 1, 0, 0);

Here GCC is reporting an uninitialized warning for fd. I think it's
better to avoid special case for TFO above, and let
sock_connect_mptcp() deal with that.


Cheers,

Paolo

Hello all,

@Matthieu Baerts,

Please find the first packetdrill test in this github repo: 
https://github.com/dmytroshytyi/MPTFO

Precisely,

*.pkt:

https://github.com/dmytroshytyi/MPTFO/blob/main/client-MSG_FASTOPEN.pkt

and result of test execution:

https://github.com/dmytroshytyi/MPTFO/blob/main/packetdrill-sender-test-result.png


Also I created a pull request in multipath-tcp/packetdrill:

https://github.com/multipath-tcp/packetdrill/pull/99


Best regards,

Dmytro SHYTYI.



On 11/6/2022 4:24 PM, Dmytro Shytyi wrote:
> This patch adds the selftests support for mptfo in mptcp_connect.c
> We introduce mptfo option, that sets "TCP_FASTOPEN" + "MSG_FASTOPEN"
> We call sendto() instead of connect().
>
> Signed-off-by: Dmytro Shytyi <dmytro@shytyi.net>
> ---
>   .../selftests/net/mptcp/mptcp_connect.c       | 121 +++++++++++++-----
>   .../selftests/net/mptcp/mptcp_connect.sh      |  21 +++
>   2 files changed, 113 insertions(+), 29 deletions(-)
>
> diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.c b/tools/testing/selftests/net/mptcp/mptcp_connect.c
> index e54653ea2ed4..4bc855159c52 100644
> --- a/tools/testing/selftests/net/mptcp/mptcp_connect.c
> +++ b/tools/testing/selftests/net/mptcp/mptcp_connect.c
> @@ -26,11 +26,13 @@
>   
>   #include <netdb.h>
>   #include <netinet/in.h>
> +#include <netinet/tcp.h>
>   
> -#include <linux/tcp.h>
>   #include <linux/time_types.h>
>   #include <linux/sockios.h>
>   
> +
> +
>   extern int optind;
>   
>   #ifndef IPPROTO_MPTCP
> @@ -83,6 +85,7 @@ struct cfg_cmsg_types {
>   
>   struct cfg_sockopt_types {
>   	unsigned int transparent:1;
> +	unsigned int mptfo:1;
>   };
>   
>   struct tcp_inq_state {
> @@ -232,6 +235,14 @@ static void set_transparent(int fd, int pf)
>   	}
>   }
>   
> +static void set_mptfo(int fd, int pf)
> +{
> +	int qlen = 25;
> +
> +	if (setsockopt(fd, SOL_TCP, TCP_FASTOPEN, &qlen, sizeof(qlen)) == -1)
> +		perror("TCP_FASTOPEN");
> +}
> +
>   static int do_ulp_so(int sock, const char *name)
>   {
>   	return setsockopt(sock, IPPROTO_TCP, TCP_ULP, name, strlen(name));
> @@ -300,6 +311,9 @@ static int sock_listen_mptcp(const char * const listenaddr,
>   		if (cfg_sockopt_types.transparent)
>   			set_transparent(sock, pf);
>   
> +		if (cfg_sockopt_types.mptfo)
> +			set_mptfo(sock, pf);
> +
>   		if (bind(sock, a->ai_addr, a->ai_addrlen) == 0)
>   			break; /* success */
>   
> @@ -330,13 +344,18 @@ static int sock_listen_mptcp(const char * const listenaddr,
>   
>   static int sock_connect_mptcp(const char * const remoteaddr,
>   			      const char * const port, int proto,
> -			      struct addrinfo **peer)
> +			      struct addrinfo **peer,
> +			      int infd,
> +			      unsigned int *woff)
>   {
>   	struct addrinfo hints = {
>   		.ai_protocol = IPPROTO_TCP,
>   		.ai_socktype = SOCK_STREAM,
>   	};
>   	struct addrinfo *a, *addr;
> +	unsigned int wlen = 0;
> +	int syn_copied = 0;
> +	char wbuf[8192];
>   	int sock = -1;
>   
>   	hints.ai_family = pf;
> @@ -354,14 +373,33 @@ static int sock_connect_mptcp(const char * const remoteaddr,
>   		if (cfg_mark)
>   			set_mark(sock, cfg_mark);
>   
> -		if (connect(sock, a->ai_addr, a->ai_addrlen) == 0) {
> -			*peer = a;
> -			break; /* success */
> -		}
> +		if (cfg_sockopt_types.mptfo) {
> +			if (wlen == 0)
> +				wlen = read(infd, wbuf, sizeof(wbuf));
>   
> -		perror("connect()");
> -		close(sock);
> -		sock = -1;
> +			syn_copied = sendto(sock, wbuf, wlen, MSG_FASTOPEN,
> +					    a->ai_addr, a->ai_addrlen);
> +			if (syn_copied) {
> +				*woff = wlen;
> +				*peer = a;
> +				break; /* success */
> +			}
> +		} else {
> +			if (connect(sock, a->ai_addr, a->ai_addrlen) == 0) {
> +				*peer = a;
> +				break; /* success */
> +			}
> +		}
> +		if (cfg_sockopt_types.mptfo) {
> +			perror("sendto()");
> +			close(sock);
> +			sock = -1;
> +		} else {
> +
> +			perror("connect()");
> +			close(sock);
> +			sock = -1;
> +		}
>   	}
>   
>   	freeaddrinfo(addr);
> @@ -571,13 +609,14 @@ static void shut_wr(int fd)
>   	shutdown(fd, SHUT_WR);
>   }
>   
> -static int copyfd_io_poll(int infd, int peerfd, int outfd, bool *in_closed_after_out)
> +static int copyfd_io_poll(int infd, int peerfd, int outfd,
> +			  bool *in_closed_after_out, unsigned int woff)
>   {
>   	struct pollfd fds = {
>   		.fd = peerfd,
>   		.events = POLLIN | POLLOUT,
>   	};
> -	unsigned int woff = 0, wlen = 0, total_wlen = 0, total_rlen = 0;
> +	unsigned int wlen = 0, total_wlen = 0, total_rlen = 0;
>   	char wbuf[8192];
>   
>   	set_nonblock(peerfd, true);
> @@ -839,7 +878,7 @@ static int copyfd_io_sendfile(int infd, int peerfd, int outfd,
>   	return err;
>   }
>   
> -static int copyfd_io(int infd, int peerfd, int outfd, bool close_peerfd)
> +static int copyfd_io(int infd, int peerfd, int outfd, bool close_peerfd, unsigned int woff)
>   {
>   	bool in_closed_after_out = false;
>   	struct timespec start, end;
> @@ -851,7 +890,7 @@ static int copyfd_io(int infd, int peerfd, int outfd, bool close_peerfd)
>   
>   	switch (cfg_mode) {
>   	case CFG_MODE_POLL:
> -		ret = copyfd_io_poll(infd, peerfd, outfd, &in_closed_after_out);
> +		ret = copyfd_io_poll(infd, peerfd, outfd, &in_closed_after_out, woff);
>   		break;
>   
>   	case CFG_MODE_MMAP:
> @@ -1033,7 +1072,7 @@ int main_loop_s(int listensock)
>   
>   		SOCK_TEST_TCPULP(remotesock, 0);
>   
> -		copyfd_io(fd, remotesock, 1, true);
> +		copyfd_io(fd, remotesock, 1, true, 0);
>   	} else {
>   		perror("accept");
>   		return 1;
> @@ -1130,6 +1169,11 @@ static void parse_setsock_options(const char *name)
>   		return;
>   	}
>   
> +	if (strncmp(name, "MPTFO", len) == 0) {
> +		cfg_sockopt_types.mptfo = 1;
> +		return;
> +	}
> +
>   	fprintf(stderr, "Unrecognized setsockopt option %s\n", name);
>   	exit(1);
>   }
> @@ -1168,23 +1212,25 @@ int main_loop(void)
>   {
>   	int fd, ret, fd_in = 0;
>   	struct addrinfo *peer;
> +	unsigned int woff = 0;
>   
> -	/* listener is ready. */
> -	fd = sock_connect_mptcp(cfg_host, cfg_port, cfg_sock_proto, &peer);
> -	if (fd < 0)
> -		return 2;
> -
> +	if (!cfg_sockopt_types.mptfo) {
> +		/* listener is ready. */
> +		fd = sock_connect_mptcp(cfg_host, cfg_port, cfg_sock_proto, &peer, 0, 0);
> +		if (fd < 0)
> +			return 2;
>   again:
> -	check_getpeername_connect(fd);
> +		check_getpeername_connect(fd);
>   
> -	SOCK_TEST_TCPULP(fd, cfg_sock_proto);
> +		SOCK_TEST_TCPULP(fd, cfg_sock_proto);
>   
> -	if (cfg_rcvbuf)
> -		set_rcvbuf(fd, cfg_rcvbuf);
> -	if (cfg_sndbuf)
> -		set_sndbuf(fd, cfg_sndbuf);
> -	if (cfg_cmsg_types.cmsg_enabled)
> -		apply_cmsg_types(fd, &cfg_cmsg_types);
> +		if (cfg_rcvbuf)
> +			set_rcvbuf(fd, cfg_rcvbuf);
> +		if (cfg_sndbuf)
> +			set_sndbuf(fd, cfg_sndbuf);
> +		if (cfg_cmsg_types.cmsg_enabled)
> +			apply_cmsg_types(fd, &cfg_cmsg_types);
> +	}
>   
>   	if (cfg_input) {
>   		fd_in = open(cfg_input, O_RDONLY);
> @@ -1192,8 +1238,25 @@ int main_loop(void)
>   			xerror("can't open %s:%d", cfg_input, errno);
>   	}
>   
> -	/* close the client socket open only if we are not going to reconnect */
> -	ret = copyfd_io(fd_in, fd, 1, 0);
> +	if (cfg_sockopt_types.mptfo) {
> +		/* sendto() instead of connect */
> +		fd = sock_connect_mptcp(cfg_host, cfg_port, cfg_sock_proto, &peer, fd_in, &woff);
> +		if (fd < 0)
> +			return 2;
> +
> +		check_getpeername_connect(fd);
> +
> +		SOCK_TEST_TCPULP(fd, cfg_sock_proto);
> +
> +		if (cfg_rcvbuf)
> +			set_rcvbuf(fd, cfg_rcvbuf);
> +		if (cfg_sndbuf)
> +			set_sndbuf(fd, cfg_sndbuf);
> +		if (cfg_cmsg_types.cmsg_enabled)
> +			apply_cmsg_types(fd, &cfg_cmsg_types);
> +	}
> +
> +	ret = copyfd_io(fd_in, fd, 1, 0, 0);
>   	if (ret)
>   		return ret;
>   
> diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.sh b/tools/testing/selftests/net/mptcp/mptcp_connect.sh
> index 621af6895f4d..60198b91a530 100755
> --- a/tools/testing/selftests/net/mptcp/mptcp_connect.sh
> +++ b/tools/testing/selftests/net/mptcp/mptcp_connect.sh
> @@ -762,6 +762,23 @@ run_tests_peekmode()
>   	run_tests_lo "$ns1" "$ns1" dead:beef:1::1 1 "-P ${peekmode}"
>   }
>   
> +run_tests_mptfo()
> +{
> +	echo "INFO: with MPTFO start"
> +	ip netns exec "$ns1" sysctl -q net.ipv4.tcp_fastopen=2
> +	ip netns exec "$ns2" sysctl -q net.ipv4.tcp_fastopen=1
> +
> +	run_tests_lo "$ns1" "$ns2" 10.0.1.1 0 "-o MPTFO"
> +	run_tests_lo "$ns1" "$ns2" 10.0.1.1 0 "-o MPTFO"
> +
> +	run_tests_lo "$ns1" "$ns2" dead:beef:1::1 0 "-o MPTFO"
> +	run_tests_lo "$ns1" "$ns2" dead:beef:1::1 0 "-o MPTFO"
> +
> +	ip netns exec "$ns1" sysctl -q net.ipv4.tcp_fastopen=0
> +	ip netns exec "$ns2" sysctl -q net.ipv4.tcp_fastopen=0
> +	echo "INFO: with MPTFO end"
> +}
> +
>   run_tests_disconnect()
>   {
>   	local peekmode="$1"
> @@ -901,6 +918,10 @@ run_tests_peekmode "saveWithPeek"
>   run_tests_peekmode "saveAfterPeek"
>   stop_if_error "Tests with peek mode have failed"
>   
> +# MPTFO (MultiPath TCP Fatopen tests)
> +run_tests_mptfo
> +stop_if_error "Tests with MPTFO have failed"
> +
>   # connect to ns4 ip address, ns2 should intercept/proxy
>   run_test_transparent 10.0.3.1 "tproxy ipv4"
>   run_test_transparent dead:beef:3::1 "tproxy ipv6"

Hi Dmytro,

Thank you for your modifications, that's great!

Our CI did some validations and here is its report:

- KVM Validation: normal:
  - Unstable: 2 failed test(s): mptcp_connect_mmap selftest_mptcp_connect 🔴:
  - Task: https://cirrus-ci.com/task/5790712473059328
  - Summary: https://api.cirrus-ci.com/v1/artifact/task/5790712473059328/summary/summary.txt

- KVM Validation: debug:
  - Unstable: 3 failed test(s): mptcp_connect_mmap packetdrill_sockopts selftest_mptcp_connect 🔴:
  - Task: https://cirrus-ci.com/task/5227762519638016
  - Summary: https://api.cirrus-ci.com/v1/artifact/task/5227762519638016/summary/summary.txt

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/4bc59678c676


If there are some issues, you can reproduce them using the same environment as
the one used by the CI thanks to a docker image, e.g.:

    $ cd [kernel source code]
    $ docker run -v "${PWD}:${PWD}:rw" -w "${PWD}" --privileged --rm -it \
        --pull always mptcp/mptcp-upstream-virtme-docker:latest \
        auto-debug

For more details:

    https://github.com/multipath-tcp/mptcp-upstream-virtme-docker


Please note that despite all the efforts that have been already done to have a
stable tests suite when executed on a public CI like here, it is possible some
reported issues are not due to your modifications. Still, do not hesitate to
help us improve that ;-)

Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (Tessares)