feat(mptcp): Basic implementation of Multipath-TCP

[zonyitoo]

• Currently support macOS (Client Only) and Linux (> 5.19)
• ref MPTCP support #1156

[dev4u]

请教一下，这玩意有什么用途吗？

[database64128]

The MPTCP folks seem to be pushing a lot lately. MPTCP support detection logic just got merged into the Go runtime: golang/go@59d7c69

[zonyitoo]

Some observation:

• Linux 5.19 (Ubuntu 22.10) doesn't support TCP_KEEPIDLE and TCP_KEEPINTV sockopts.

Accepted socket (13):

accept4(9, {sa_family=AF_INET6, sin6_port=htons(64832), sin6_flowinfo=htonl(0), inet_pton(AF_INET6, "::ffff:192.168.11.186", &sin6_addr), sin6_scope_id=0}, [128 => 28], SOCK_CLOEXEC|SOCK_NONBLOCK) = 13
setsockopt(13, SOL_SOCKET, SO_KEEPALIVE, [1], 4) = 0
setsockopt(13, SOL_TCP, TCP_KEEPIDLE, [15], 4) = -1 EOPNOTSUPP
setsockopt(13, SOL_TCP, TCP_KEEPINTVL, [15], 4) = -1 EOPNOTSUPP

Connected socket (14), target doesn't support MPTCP:

socket(AF_INET, SOCK_STREAM, IPPROTO_MPTCP) = 14
connect(14, {sa_family=AF_INET, sin_port=htons(443), sin_addr=inet_addr("14.119.104.189")}, 16) = -1 EINPROGRESS
setsockopt(14, SOL_SOCKET, SO_KEEPALIVE, [1], 4) = 0
setsockopt(14, SOL_TCP, TCP_KEEPIDLE, [15], 4) = 0
setsockopt(14, SOL_TCP, TCP_KEEPINTVL, [15], 4) = 0

Connected socket (14), target supports MPTCP:

socket(AF_INET6, SOCK_STREAM, IPPROTO_MPTCP) = 14
connect(14, {sa_family=AF_INET6, sin6_port=htons(8388), sin6_flowinfo=htonl(0), inet_pton(AF_INET6, "::1", &sin6_addr), sin6_scope_id=0}, 28) = -1 EINPROGRESS
setsockopt(14, SOL_SOCKET, SO_KEEPALIVE, [1], 4) = 0
setsockopt(14, SOL_TCP, TCP_KEEPIDLE, [15], 4) = -1 EOPNOTSUPP

• macOS supports AF_MULTIPATH only for client sockets. bind() will return EOPNOTSUPP and setsockopt with SO_REUSEADDR will return ENOPROTOOPT.

socket(0x27, 0x1, 0x6)		 = 9 0
bind(0x9, 0x700005C74560, 0x10)		 = -1 102

[zonyitoo]

ref multipath-tcp/mptcp_net-next#383

[wangyoucao577]

@zonyitoo Hi, why does it require Linux > 5.19? It's MPTCPv1, which is available since Linux v5.6, right? https://github.com/multipath-tcp/mptcp_net-next/wiki#changelog

[zonyitoo]

Did you tried to run it under older version of Linux Kernel?

[wangyoucao577]

I haven't tried this app yet. But I have tried mptcpize run -d iperf3 on Linux v5.15 (both client and server side), which worked well.

[zonyitoo]

You could try to run it under v5.15 and see if any error occured.