diff mbox series

[mptcp-next,v3,2/4] selftests/bpf: Add mptcp subflow example

Message ID 4c1e2173c4890caeb2353dfb19fc1f281c0f303f.1711296000.git.tanggeliang@kylinos.cn (mailing list archive)
State Superseded, archived
Headers show
Series setsockopt per subflow: BPF | expand

Checks

Context Check Description
matttbe/build success Build and static analysis OK
matttbe/checkpatch warning total: 0 errors, 1 warnings, 0 checks, 73 lines checked
matttbe/shellcheck success MPTCP selftests files have not been modified
matttbe/KVM_Validation__normal success Success! ✅
matttbe/KVM_Validation__debug success Success! ✅
matttbe/KVM_Validation__btf__only_bpftest_all_ success Success! ✅

Commit Message

Geliang Tang March 24, 2024, 4:01 p.m. UTC 
From: Geliang Tang <tanggeliang@kylinos.cn>

Move Nicolas's patch into bpf selftests directory. This example added a
test that was adding a different mark (SO_MARK) on each subflow, and
changing the TCP CC only on the first subflow.

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, we implemented two different behaviours:

    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".

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/76
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
 .../selftests/bpf/progs/mptcp_subflow.c       | 73 +++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/mptcp_subflow.c
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/progs/mptcp_subflow.c b/tools/testing/selftests/bpf/progs/mptcp_subflow.c
new file mode 100644
index 000000000000..9553099ffd5f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/mptcp_subflow.c
@@ -0,0 +1,73 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020, Tessares SA. */
+/* Copyright (c) 2024, Kylin Software */
+/* Author: Nicolas Rybowski */
+
+#include <sys/socket.h> // SOL_SOCKET, SO_MARK, ...
+#include <linux/tcp.h>  // TCP_CONGESTION
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_tcp_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+#ifndef SOL_TCP
+#define SOL_TCP 6
+#endif
+
+#ifndef TCP_CA_NAME_MAX
+#define TCP_CA_NAME_MAX 16
+#endif
+
+char cc[TCP_CA_NAME_MAX] = "reno";
+
+/* Associate a subflow counter to each token */
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(key_size, sizeof(__u32));
+	__uint(value_size, sizeof(__u32));
+	__uint(max_entries, 100);
+} mptcp_sf SEC(".maps");
+
+SEC("sockops")
+int mptcp_subflow(struct bpf_sock_ops *skops)
+{
+	__u32 init = 1, key, mark, *cnt;
+	struct mptcp_sock *msk;
+	struct bpf_sock *sk;
+	int err;
+
+	if (skops->op != BPF_SOCK_OPS_TCP_CONNECT_CB)
+		return 1;
+
+	sk = skops->sk;
+	if (!sk)
+		return 1;
+
+	msk = bpf_skc_to_mptcp_sock(sk);
+	if (!msk)
+		return 1;
+
+	key = msk->token;
+	cnt = bpf_map_lookup_elem(&mptcp_sf, &key);
+	if (cnt) {
+		/* A new subflow is added to an existing MPTCP connection */
+		__sync_fetch_and_add(cnt, 1);
+		mark = *cnt;
+	} else {
+		/* A new MPTCP connection is just initiated and this is its primary
+		 *  subflow
+		 */
+		bpf_map_update_elem(&mptcp_sf, &key, &init, BPF_ANY);
+		mark = init;
+	}
+
+	/* Set the mark of the subflow's socket to its apparition order */
+	err = bpf_setsockopt(skops, SOL_SOCKET, SO_MARK, &mark, sizeof(mark));
+	if (err < 0)
+		return 1;
+	if (mark == 1)
+		err = bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION, cc, TCP_CA_NAME_MAX);
+
+	return 1;
+}