From: Geliang Tang <tanggeliang@xxxxxxxxxx>
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 'cond_break' 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@xxxxxxxxxx>
Signed-off-by: Geliang Tang <tanggeliang@xxxxxxxxxx>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx>
---
Notes:
- v5: new patch, instead of using 'ss' in the following patch
---
MAINTAINERS | 2 +-
tools/testing/selftests/bpf/progs/mptcp_bpf.h | 42 ++++++++++++++
tools/testing/selftests/bpf/progs/mptcp_subflow.c | 69 +++++++++++++++++++++++
3 files changed, 112 insertions(+), 1 deletion(-)
diff --git a/MAINTAINERS b/MAINTAINERS
index 30a9b9450e11..2674b86209d1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -16058,7 +16058,7 @@ F: include/net/mptcp.h
F: include/trace/events/mptcp.h
F: include/uapi/linux/mptcp*.h
F: net/mptcp/
-F: tools/testing/selftests/bpf/*/*mptcp*.c
+F: tools/testing/selftests/bpf/*/*mptcp*.[ch]
F: tools/testing/selftests/net/mptcp/
NETWORKING [TCP]
diff --git a/tools/testing/selftests/bpf/progs/mptcp_bpf.h b/tools/testing/selftests/bpf/progs/mptcp_bpf.h
new file mode 100644
index 000000000000..179b74c1205f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/mptcp_bpf.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
+#ifndef __MPTCP_BPF_H__
+#define __MPTCP_BPF_H__
+
+#include "bpf_experimental.h"
+
+/* list helpers from include/linux/list.h */
+static inline int list_is_head(const struct list_head *list,
+ const struct list_head *head)
+{
+ return list == head;
+}
+
+#define list_entry(ptr, type, member) \
+ container_of(ptr, type, member)
+
+#define list_first_entry(ptr, type, member) \
+ list_entry((ptr)->next, type, member)
+
+#define list_next_entry(pos, member) \
+ list_entry((pos)->member.next, typeof(*(pos)), member)
+
+#define list_entry_is_head(pos, head, member) \
+ list_is_head(&pos->member, (head))
+
+/* small difference: 'cond_break' has been added in the conditions */
+#define list_for_each_entry(pos, head, member) \
+ for (pos = list_first_entry(head, typeof(*pos), member); \
+ cond_break, !list_entry_is_head(pos, head, member); \
+ pos = list_next_entry(pos, member))
+
+/* mptcp helpers from protocol.h */
+#define mptcp_for_each_subflow(__msk, __subflow) \
+ list_for_each_entry(__subflow, &((__msk)->conn_list), node)
+
+static __always_inline struct sock *
+mptcp_subflow_tcp_sock(const struct mptcp_subflow_context *subflow)
+{
+ return subflow->tcp_sock;
+}
+
+#endif
diff --git a/tools/testing/selftests/bpf/progs/mptcp_subflow.c b/tools/testing/selftests/bpf/progs/mptcp_subflow.c
index 2e28f4a215b5..70302477e326 100644
--- a/tools/testing/selftests/bpf/progs/mptcp_subflow.c
+++ b/tools/testing/selftests/bpf/progs/mptcp_subflow.c
@@ -4,10 +4,12 @@
/* vmlinux.h, bpf_helpers.h and other 'define' */
#include "bpf_tracing_net.h"
+#include "mptcp_bpf.h"
char _license[] SEC("license") = "GPL";
char cc[TCP_CA_NAME_MAX] = "reno";
+int pid;
/* Associate a subflow counter to each token */
struct {
@@ -57,3 +59,70 @@ int mptcp_subflow(struct bpf_sock_ops *skops)
return 1;
}
+
+static int _check_getsockopt_subflow_mark(struct mptcp_sock *msk, struct bpf_sockopt *ctx)
+{
+ struct mptcp_subflow_context *subflow;
+ int i = 0;
+
+ mptcp_for_each_subflow(msk, subflow) {
+ struct sock *ssk;
+
+ ssk = mptcp_subflow_tcp_sock(bpf_core_cast(subflow,
+ struct mptcp_subflow_context));
+
+ if (ssk->sk_mark != ++i) {
+ ctx->retval = -2;
+ break;
+ }
+ }
+
+ return 1;
+}
+
+static int _check_getsockopt_subflow_cc(struct mptcp_sock *msk, struct bpf_sockopt *ctx)
+{
+ struct mptcp_subflow_context *subflow;
+
+ mptcp_for_each_subflow(msk, subflow) {
+ struct inet_connection_sock *icsk;
+ struct sock *ssk;
+
+ ssk = mptcp_subflow_tcp_sock(bpf_core_cast(subflow,
+ struct mptcp_subflow_context));
+ icsk = bpf_core_cast(ssk, struct inet_connection_sock);
+
+ if (ssk->sk_mark == 2 &&
+ __builtin_memcmp(icsk->icsk_ca_ops->name, cc, TCP_CA_NAME_MAX)) {
+ ctx->retval = -2;
+ break;
+ }
+ }
+
+ return 1;
+}
+
+SEC("cgroup/getsockopt")
+int _getsockopt_subflow(struct bpf_sockopt *ctx)
+{
+ struct bpf_sock *sk = ctx->sk;
+ struct mptcp_sock *msk;
+
+ if (bpf_get_current_pid_tgid() >> 32 != pid)
+ return 1;
+
+ if (!sk || sk->protocol != IPPROTO_MPTCP ||
+ (!(ctx->level == SOL_SOCKET && ctx->optname == SO_MARK) &&
+ !(ctx->level == SOL_TCP && ctx->optname == TCP_CONGESTION)))
+ return 1;
+
+ msk = bpf_core_cast(sk, struct mptcp_sock);
+ if (msk->pm.subflows != 1) {
+ ctx->retval = -1;
+ return 1;
+ }
+
+ if (ctx->optname == SO_MARK)
+ return _check_getsockopt_subflow_mark(msk, ctx);
+ return _check_getsockopt_subflow_cc(msk, ctx);
+}
--
2.45.2
