|
This patch adds a "cgroup/getsockopt" way to inspect the subflows of an
MPTCP socket, and verify the modifications done by the same BPF program
in the previous commit: a different mark per subflow, and a different
TCP CC set on the second one. This new hook will be used by the next
commit to verify the socket options set on each subflow.
This extra "cgroup/getsockopt" prog walks the msk->conn_list and use
bpf_core_cast to cast a pointer for readonly. It allows to inspect all
the fields of a structure.
Note that on the kernel side, the MPTCP socket stores a list of subflows
under 'msk->conn_list'. They can be iterated using the generic 'list'
helpers. They have been imported here, with a small difference:
list_for_each_entry() uses 'can_loop' to limit the number of iterations,
and ease its use. Because only data need to be read here, it is enough
to use this technique. It is planned to use bpf_iter, when BPF programs
will be used to modify data from the different subflows.
mptcp_subflow_tcp_sock() and mptcp_for_each_stubflow() helpers have also
be imported.
Suggested-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20240926-upstream-bpf-next-20240506-mptcp-subflow-test-v7-2-d26029e15cdd@kernel.org
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
|
|
Move Nicolas' patch into bpf selftests directory. This example adds a
different mark (SO_MARK) on each subflow, and changes the TCP CC only on
the first subflow.
From the userspace, an application can do a setsockopt() on an MPTCP
socket, and typically the same value will be propagated to all subflows
(paths). If someone wants to have different values per subflow, the
recommended way is to use BPF. So it is good to add such example here,
and make sure there is no regressions.
This example shows how it is possible to:
Identify the parent msk of an MPTCP subflow.
Put different sockopt for each subflow of a same MPTCP connection.
Here especially, two different behaviours are implemented:
A socket mark (SOL_SOCKET SO_MARK) is put on each subflow of a same
MPTCP connection. The order of creation of the current subflow defines
its mark. The TCP CC algorithm of the very first subflow of an MPTCP
connection is set to "reno".
This is just to show it is possible to identify an MPTCP connection, and
set socket options, from different SOL levels, per subflow. "reno" has
been picked because it is built-in and usually not set as default one.
It is easy to verify with 'ss' that these modifications have been
applied correctly. That's what the next patch is going to do.
Nicolas' code comes from:
commit 4d120186e4d6 ("bpf:examples: update mptcp_set_mark_kern.c")
from the MPTCP repo https://github.com/multipath-tcp/mptcp_net-next (the
"scripts" branch), and it has been adapted by Geliang.
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/76
Co-developed-by: Geliang Tang <tanggeliang@kylinos.cn>
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Signed-off-by: Nicolas Rybowski <nicolas.rybowski@tessares.net>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20240926-upstream-bpf-next-20240506-mptcp-subflow-test-v7-1-d26029e15cdd@kernel.org
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
|
