As is described in the "How to use MPTCP?" section in MPTCP wiki [1]:
"Your app should create sockets with IPPROTO_MPTCP as the proto: ( socket(AF_INET, SOCK_STREAM, IPPROTO_MPTCP); ). Legacy apps can be forced to create and use MPTCP sockets instead of TCP ones via the mptcpize command bundled with the mptcpd daemon."
But the mptcpize (LD_PRELOAD technique) command has some limitations [2]:
- it doesn't work if the application is not using libc (e.g. GoLang apps) - in some envs, it might not be easy to set env vars / change the way apps are launched, e.g. on Android - mptcpize needs to be launched with all apps that want MPTCP: we could have more control from BPF to enable MPTCP only for some apps or all the ones of a netns or a cgroup, etc. - it is not in BPF, we cannot talk about it at netdev conf.
So this patchset attempts to use BPF to implement functions similer to mptcpize.
The main idea is to add a hook in sys_socket() to change the protocol id from IPPROTO_TCP (or 0) to IPPROTO_MPTCP.
[1] https://github.com/multipath-tcp/mptcp_net-next/wiki [2] https://github.com/multipath-tcp/mptcp_net-next/issues/79
v9: - update comment for 'update_socket_protocol'.
v8: - drop the additional checks on the 'protocol' value after the 'update_socket_protocol()' call.
v7: - add __weak and __diag_* for update_socket_protocol.
v6: - add update_socket_protocol.
v5: - add bpf_mptcpify helper.
v4: - use lsm_cgroup/socket_create
v3: - patch 8: char cmd[128]; -> char cmd[256];
v2: - Fix build selftests errors reported by CI
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/79
Geliang Tang (4): bpf: Add update_socket_protocol hook selftests/bpf: Use random netns name for mptcp selftests/bpf: Add two mptcp netns helpers selftests/bpf: Add mptcpify test
net/mptcp/bpf.c | 17 +++ net/socket.c | 24 ++++ .../testing/selftests/bpf/prog_tests/mptcp.c | 125 ++++++++++++++++-- tools/testing/selftests/bpf/progs/mptcpify.c | 25 ++++ 4 files changed, 182 insertions(+), 9 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/mptcpify.c