Geliang Tang says:
====================
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
v14:
- Use getsockopt(MPTCP_INFO) to verify mptcp protocol intead of using
nstat command.
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
====================
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>