[PATCH mptcp-next v13 0/4] bpf: Force to MPTCP

Geliang Tang
2023-08-12T02:53:55Z

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

v13:
- drop "Use random netns name for mptcp" patch.

v12:
- update diag_* log of update_socket_protocol.
- add 'ip netns show' after 'ip netns del' to check if there is
a test did not clean up its netns.
- return libbpf_get_error() instead of -EIO for the error from
open_and_load().
- Use getsockopt(SOL_PROTOCOL) to verify mptcp protocol intead of
using 'ss -tOni'.

v11:
- add comments about outputs of 'ss' and 'nstat'.
- use "err = verify_mptcpify()" instead of using =+.

v10:
- drop "#ifdef CONFIG_BPF_JIT".
- include vmlinux.h and bpf_tracing_net.h to avoid defining some
macros.
- drop unneeded checks for mptcp.

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: Add two mptcp netns helpers
selftests/bpf: Fix error checks of mptcp open_and_load
selftests/bpf: Add mptcpify test

net/mptcp/bpf.c | 15 ++
net/socket.c | 26 +++-
.../testing/selftests/bpf/prog_tests/mptcp.c | 141 +++++++++++++++---
tools/testing/selftests/bpf/progs/mptcpify.c | 20 +++
4 files changed, 182 insertions(+), 20 deletions(-)
create mode 100644 tools/testing/selftests/bpf/progs/mptcpify.c

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