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selftests/bpf: Add getsockopt to inspect mptcp subflow
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This patch adds a "cgroup/getsockopt" way to inspect the subflows of a
mptcp socket.

mptcp_for_each_stubflow() and other helpers related to list_dentry are
added into progs/mptcp_bpf.h.

Add an extra "cgroup/getsockopt" prog to walk the msk->conn_list and use
bpf_rdonly_cast to cast a pointer to tcp_sock for readonly. It will allow
to inspect all the fields in a tcp_sock.

Suggested-by: Martin KaFai Lau <[email protected]>
Signed-off-by: Geliang Tang <[email protected]>
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Geliang Tang authored and intel-lab-lkp committed Aug 20, 2024
1 parent 538622b commit 62c4c77
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Showing 3 changed files with 69 additions and 0 deletions.
11 changes: 11 additions & 0 deletions tools/testing/selftests/bpf/prog_tests/mptcp.c
Original file line number Diff line number Diff line change
Expand Up @@ -383,6 +383,7 @@ static void run_subflow(char *new)
{
int server_fd, client_fd, err;
char cc[TCP_CA_NAME_MAX];
unsigned int mark;
socklen_t len;

server_fd = start_mptcp_server(AF_INET, ADDR_1, PORT_1, 0);
Expand All @@ -407,6 +408,10 @@ static void run_subflow(char *new)
ASSERT_OK(ss_search(ADDR_1, new), "ss_search new cc");
ASSERT_OK(ss_search(ADDR_2, cc), "ss_search default cc");

len = sizeof(mark);
err = getsockopt(client_fd, SOL_SOCKET, SO_MARK, &mark, &len);
ASSERT_OK(err, "getsockopt(client_fd, SO_MARK)");

close(client_fd);
fail:
close(server_fd);
Expand All @@ -417,6 +422,7 @@ static void test_subflow(void)
int cgroup_fd, prog_fd, err;
struct mptcp_subflow *skel;
struct nstoken *nstoken;
struct bpf_link *link;

cgroup_fd = test__join_cgroup("/mptcp_subflow");
if (!ASSERT_GE(cgroup_fd, 0, "join_cgroup: mptcp_subflow"))
Expand All @@ -442,6 +448,10 @@ static void test_subflow(void)
if (endpoint_init("subflow") < 0)
goto close_netns;

link = bpf_program__attach_cgroup(skel->progs._getsockopt, cgroup_fd);
if (!ASSERT_OK_PTR(link, "getsockopt prog"))
goto close_netns;

run_subflow(skel->data->cc);

close_netns:
Expand All @@ -450,6 +460,7 @@ static void test_subflow(void)
mptcp_subflow__destroy(skel);
close_cgroup:
close(cgroup_fd);
bpf_link__destroy(link);
}

static struct nstoken *sched_init(char *flags, char *sched)
Expand Down
26 changes: 26 additions & 0 deletions tools/testing/selftests/bpf/progs/mptcp_bpf.h
Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,32 @@

#define MPTCP_SUBFLOWS_MAX 8

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))

#define list_for_each_entry(pos, head, member) \
for (pos = list_first_entry(head, typeof(*pos), member); \
!list_entry_is_head(pos, head, member); \
pos = list_next_entry(pos, member))

#define mptcp_for_each_subflow(__msk, __subflow) \
list_for_each_entry(__subflow, &((__msk)->conn_list), node)

extern void mptcp_subflow_set_scheduled(struct mptcp_subflow_context *subflow,
bool scheduled) __ksym;

Expand Down
32 changes: 32 additions & 0 deletions tools/testing/selftests/bpf/progs/mptcp_subflow.c
Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@

/* vmlinux.h, bpf_helpers.h and other 'define' */
#include "bpf_tracing_net.h"
#include "mptcp_bpf.h"

char _license[] SEC("license") = "GPL";

Expand Down Expand Up @@ -57,3 +58,34 @@ int mptcp_subflow(struct bpf_sock_ops *skops)

return 1;
}

SEC("cgroup/getsockopt")
int _getsockopt(struct bpf_sockopt *ctx)
{
struct mptcp_sock *msk = bpf_core_cast(ctx->sk, struct mptcp_sock);
struct mptcp_subflow_context *subflow;
int i = 0;

if (!msk || ctx->level != SOL_SOCKET || ctx->optname != SO_MARK)
return 1;

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 != i + 1)
ctx->retval = -1;
if (ssk->sk_mark == 1 &&
__builtin_memcmp(icsk->icsk_ca_ops->name, cc, TCP_CA_NAME_MAX))
ctx->retval = -1;

if (i++ >= MPTCP_SUBFLOWS_MAX)
break;
}

return 1;
}

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