diff mbox series

[bpf-next,v9,4/4] selftests/bpf: Add mptcpify test

Message ID 92ee6be5a465601ff3a2df29b6a517086e87ca3c.1691069778.git.geliang.tang@suse.com (mailing list archive)
State Handled Elsewhere
Headers show
Series bpf: Force to MPTCP | expand

Commit Message

Geliang Tang Aug. 3, 2023, 1:41 p.m. UTC 
Implement a new test program mptcpify: if the family is AF_INET or
AF_INET6, the type is SOCK_STREAM, and the protocol ID is 0 or
IPPROTO_TCP, set it to IPPROTO_MPTCP. It will be hooked in
update_socket_protocol().

Extend the MPTCP test base, add a selftest test_mptcpify() for the
mptcpify case. Open and load the mptcpify test prog to mptcpify the
TCP sockets dynamically, then use start_server() and connect_to_fd()
to create a TCP socket, but actually what's created is an MPTCP
socket, which can be verified through the outputs of 'ss' and 'nstat'
commands.

Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 .../testing/selftests/bpf/prog_tests/mptcp.c  | 94 +++++++++++++++++++
 tools/testing/selftests/bpf/progs/mptcpify.c  | 25 +++++
 2 files changed, 119 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/mptcpify.c

Comments

Yonghong Song Aug. 3, 2023, 11:40 p.m. UTC | #1 
On 8/3/23 6:41 AM, Geliang Tang wrote:
> Implement a new test program mptcpify: if the family is AF_INET or
> AF_INET6, the type is SOCK_STREAM, and the protocol ID is 0 or
> IPPROTO_TCP, set it to IPPROTO_MPTCP. It will be hooked in
> update_socket_protocol().
> 
> Extend the MPTCP test base, add a selftest test_mptcpify() for the
> mptcpify case. Open and load the mptcpify test prog to mptcpify the
> TCP sockets dynamically, then use start_server() and connect_to_fd()
> to create a TCP socket, but actually what's created is an MPTCP
> socket, which can be verified through the outputs of 'ss' and 'nstat'
> commands.
> 
> Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
> Signed-off-by: Geliang Tang <geliang.tang@suse.com>
> ---
>   .../testing/selftests/bpf/prog_tests/mptcp.c  | 94 +++++++++++++++++++
>   tools/testing/selftests/bpf/progs/mptcpify.c  | 25 +++++
>   2 files changed, 119 insertions(+)
>   create mode 100644 tools/testing/selftests/bpf/progs/mptcpify.c
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/mptcp.c b/tools/testing/selftests/bpf/prog_tests/mptcp.c
> index 4407bd5c9e9a..caab3aa6a162 100644
> --- a/tools/testing/selftests/bpf/prog_tests/mptcp.c
> +++ b/tools/testing/selftests/bpf/prog_tests/mptcp.c
> @@ -6,6 +6,7 @@
>   #include "cgroup_helpers.h"
>   #include "network_helpers.h"
>   #include "mptcp_sock.skel.h"
> +#include "mptcpify.skel.h"
>   
>   char NS_TEST[32];
>   
> @@ -195,8 +196,101 @@ static void test_base(void)
>   	close(cgroup_fd);
>   }
>   
> +static void send_byte(int fd)
> +{
> +	char b = 0x55;
> +
> +	ASSERT_EQ(write(fd, &b, sizeof(b)), 1, "send single byte");
> +}
> +
> +static int verify_mptcpify(void)
> +{
> +	char cmd[256];
> +	int err = 0;
> +
> +	snprintf(cmd, sizeof(cmd),
> +		 "ip netns exec %s ss -tOni | grep -q '%s'",
> +		 NS_TEST, "tcp-ulp-mptcp");
> +	if (!ASSERT_OK(system(cmd), "No tcp-ulp-mptcp found!"))
> +		err++;
> +
> +	snprintf(cmd, sizeof(cmd),
> +		 "ip netns exec %s nstat -asz %s | awk '%s' | grep -q '%s'",
> +		 NS_TEST, "MPTcpExtMPCapableSYNACKRX",
> +		 "NR==1 {next} {print $2}", "1");
> +	if (!ASSERT_OK(system(cmd), "No MPTcpExtMPCapableSYNACKRX found!"))
> +		err++;
> +
> +	return err;
> +}
> +
> +static int run_mptcpify(int cgroup_fd)
> +{
> +	int server_fd, client_fd, prog_fd, err = 0;
> +	struct mptcpify *mptcpify_skel;
> +
> +	mptcpify_skel = mptcpify__open_and_load();
> +	if (!ASSERT_OK_PTR(mptcpify_skel, "skel_open_load"))
> +		return -EIO;
> +
> +	err = mptcpify__attach(mptcpify_skel);
> +	if (!ASSERT_OK(err, "skel_attach"))
> +		goto out;
> +
> +	prog_fd = bpf_program__fd(mptcpify_skel->progs.mptcpify);
> +	if (!ASSERT_GE(prog_fd, 0, "bpf_program__fd")) {
> +		err = -EIO;
> +		goto out;
> +	}

load success means prog_fd is always valid. So above
ASSERT_GE not needed.

> +
> +	/* without MPTCP */
> +	server_fd = start_server(AF_INET, SOCK_STREAM, NULL, 0, 0);
> +	if (!ASSERT_GE(server_fd, 0, "start_server")) {
> +		err = -EIO;
> +		goto out;
> +	}
> +
> +	client_fd = connect_to_fd(server_fd, 0);
> +	if (!ASSERT_GE(client_fd, 0, "connect to fd")) {
> +		err = -EIO;
> +		goto close_server;
> +	}
> +
> +	send_byte(client_fd);
> +	err += verify_mptcpify();
> +
> +	close(client_fd);
> +close_server:
> +	close(server_fd);
> +out:
> +	mptcpify__destroy(mptcpify_skel);
> +	return err;
> +}
> +
> +static void test_mptcpify(void)
> +{
> +	struct nstoken *nstoken = NULL;
> +	int cgroup_fd;
> +
> +	cgroup_fd = test__join_cgroup("/mptcpify");
> +	if (!ASSERT_GE(cgroup_fd, 0, "test__join_cgroup"))
> +		return;
> +
> +	nstoken = create_netns();
> +	if (!ASSERT_OK_PTR(nstoken, "create_netns"))
> +		goto fail;
> +
> +	ASSERT_OK(run_mptcpify(cgroup_fd), "run_mptcpify");
> +
> +fail:
> +	cleanup_netns(nstoken);
> +	close(cgroup_fd);
> +}
> +
>   void test_mptcp(void)
>   {
>   	if (test__start_subtest("base"))
>   		test_base();
> +	if (test__start_subtest("mptcpify"))
> +		test_mptcpify();
>   }
> diff --git a/tools/testing/selftests/bpf/progs/mptcpify.c b/tools/testing/selftests/bpf/progs/mptcpify.c
> new file mode 100644
> index 000000000000..9cf1febe982d
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/mptcpify.c
> @@ -0,0 +1,25 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2023, SUSE. */
> +
> +#include <linux/bpf.h>
> +#include <bpf/bpf_tracing.h>
> +
> +char _license[] SEC("license") = "GPL";
> +
> +#define	AF_INET		2
> +#define	AF_INET6	10
> +#define	SOCK_STREAM	1
> +#define	IPPROTO_TCP	6
> +#define	IPPROTO_MPTCP	262

To avoid the above macros, you can use
vmlinux.h and bpf_tracing_net.h.

> +
> +SEC("fmod_ret/update_socket_protocol")
> +int BPF_PROG(mptcpify, int family, int type, int protocol)
> +{
> +	if ((family == AF_INET || family == AF_INET6) &&
> +	    type == SOCK_STREAM &&
> +	    (!protocol || protocol == IPPROTO_TCP)) {
> +		return IPPROTO_MPTCP;
> +	}
> +
> +	return protocol;
> +}
Yonghong Song Aug. 4, 2023, 1:23 a.m. UTC | #2 
On 8/3/23 6:41 AM, Geliang Tang wrote:
> Implement a new test program mptcpify: if the family is AF_INET or
> AF_INET6, the type is SOCK_STREAM, and the protocol ID is 0 or
> IPPROTO_TCP, set it to IPPROTO_MPTCP. It will be hooked in
> update_socket_protocol().
> 
> Extend the MPTCP test base, add a selftest test_mptcpify() for the
> mptcpify case. Open and load the mptcpify test prog to mptcpify the
> TCP sockets dynamically, then use start_server() and connect_to_fd()
> to create a TCP socket, but actually what's created is an MPTCP
> socket, which can be verified through the outputs of 'ss' and 'nstat'
> commands.
> 
> Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
> Signed-off-by: Geliang Tang <geliang.tang@suse.com>
> ---
>   .../testing/selftests/bpf/prog_tests/mptcp.c  | 94 +++++++++++++++++++
>   tools/testing/selftests/bpf/progs/mptcpify.c  | 25 +++++
>   2 files changed, 119 insertions(+)
>   create mode 100644 tools/testing/selftests/bpf/progs/mptcpify.c
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/mptcp.c b/tools/testing/selftests/bpf/prog_tests/mptcp.c
> index 4407bd5c9e9a..caab3aa6a162 100644
> --- a/tools/testing/selftests/bpf/prog_tests/mptcp.c
> +++ b/tools/testing/selftests/bpf/prog_tests/mptcp.c
> @@ -6,6 +6,7 @@
>   #include "cgroup_helpers.h"
>   #include "network_helpers.h"
>   #include "mptcp_sock.skel.h"
> +#include "mptcpify.skel.h"
>   
>   char NS_TEST[32];
>   
> @@ -195,8 +196,101 @@ static void test_base(void)
>   	close(cgroup_fd);
>   }
>   
> +static void send_byte(int fd)
> +{
> +	char b = 0x55;
> +
> +	ASSERT_EQ(write(fd, &b, sizeof(b)), 1, "send single byte");
> +}
> +
> +static int verify_mptcpify(void)
> +{
> +	char cmd[256];
> +	int err = 0;
> +
> +	snprintf(cmd, sizeof(cmd),
> +		 "ip netns exec %s ss -tOni | grep -q '%s'",
> +		 NS_TEST, "tcp-ulp-mptcp");

Could you show what is the expected output from the above command line
   ip netns exec %s ss -tOni
?
This way, users can easily reason about the ss states based on tests.

> +	if (!ASSERT_OK(system(cmd), "No tcp-ulp-mptcp found!"))
> +		err++;
> +
> +	snprintf(cmd, sizeof(cmd),
> +		 "ip netns exec %s nstat -asz %s | awk '%s' | grep -q '%s'",
> +		 NS_TEST, "MPTcpExtMPCapableSYNACKRX",
> +		 "NR==1 {next} {print $2}", "1");

The same thing here. Could you show the expected output with
    ip netns exec %s nstat -asz %s
?

> +	if (!ASSERT_OK(system(cmd), "No MPTcpExtMPCapableSYNACKRX found!"))
> +		err++;
> +
> +	return err;
> +}
> +
[...]
Geliang Tang Aug. 4, 2023, 2:24 a.m. UTC | #3 
Hi Yonghong,

On Thu, Aug 03, 2023 at 06:23:57PM -0700, Yonghong Song wrote:
> 
> 
> On 8/3/23 6:41 AM, Geliang Tang wrote:
> > Implement a new test program mptcpify: if the family is AF_INET or
> > AF_INET6, the type is SOCK_STREAM, and the protocol ID is 0 or
> > IPPROTO_TCP, set it to IPPROTO_MPTCP. It will be hooked in
> > update_socket_protocol().
> > 
> > Extend the MPTCP test base, add a selftest test_mptcpify() for the
> > mptcpify case. Open and load the mptcpify test prog to mptcpify the
> > TCP sockets dynamically, then use start_server() and connect_to_fd()
> > to create a TCP socket, but actually what's created is an MPTCP
> > socket, which can be verified through the outputs of 'ss' and 'nstat'
> > commands.
> > 
> > Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
> > Signed-off-by: Geliang Tang <geliang.tang@suse.com>
> > ---
> >   .../testing/selftests/bpf/prog_tests/mptcp.c  | 94 +++++++++++++++++++
> >   tools/testing/selftests/bpf/progs/mptcpify.c  | 25 +++++
> >   2 files changed, 119 insertions(+)
> >   create mode 100644 tools/testing/selftests/bpf/progs/mptcpify.c
> > 
> > diff --git a/tools/testing/selftests/bpf/prog_tests/mptcp.c b/tools/testing/selftests/bpf/prog_tests/mptcp.c
> > index 4407bd5c9e9a..caab3aa6a162 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/mptcp.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/mptcp.c
> > @@ -6,6 +6,7 @@
> >   #include "cgroup_helpers.h"
> >   #include "network_helpers.h"
> >   #include "mptcp_sock.skel.h"
> > +#include "mptcpify.skel.h"
> >   char NS_TEST[32];
> > @@ -195,8 +196,101 @@ static void test_base(void)
> >   	close(cgroup_fd);
> >   }
> > +static void send_byte(int fd)
> > +{
> > +	char b = 0x55;
> > +
> > +	ASSERT_EQ(write(fd, &b, sizeof(b)), 1, "send single byte");
> > +}
> > +
> > +static int verify_mptcpify(void)
> > +{
> > +	char cmd[256];
> > +	int err = 0;
> > +
> > +	snprintf(cmd, sizeof(cmd),
> > +		 "ip netns exec %s ss -tOni | grep -q '%s'",
> > +		 NS_TEST, "tcp-ulp-mptcp");
> 
> Could you show what is the expected output from the above command line
>   ip netns exec %s ss -tOni
> ?
> This way, users can easily reason about the ss states based on tests.

There're too many items in the output of command 'ip netns exec %s ss -tOni':

'''
State Recv-Q Send-Q Local Address:Port  Peer Address:Port Process                                                                                                                                                                                                                                                                                                                                                                                                                                    
ESTAB 0      0          127.0.0.1:42225    127.0.0.1:44180 cubic wscale:7,7 rto:201 rtt:0.034/0.017 ato:40 mss:16640 pmtu:65535 rcvmss:536 advmss:65483 cwnd:10 bytes_received:1 segs_out:1 segs_in:3 data_segs_in:1 send 39152941176bps lastsnd:7 lastrcv:7 lastack:7 pacing_rate 78305882352bps delivered:1 app_limited rcv_space:33280 rcv_ssthresh:33280 minrtt:0.034 snd_wnd:33280 tcp-ulp-mptcp flags:Mec token:0000(id:0)/3a1e0d3c(id:0) seq:c2802f11c5228db6 sfseq:1 ssnoff:49d3c135 maplen:1
ESTAB 0      0          127.0.0.1:44180    127.0.0.1:42225 cubic wscale:7,7 rto:201 rtt:0.036/0.02 mss:16640 pmtu:65535 rcvmss:536 advmss:65483 cwnd:10 bytes_sent:1 bytes_acked:2 segs_out:3 segs_in:2 data_segs_out:1 send 36977777778bps lastsnd:7 lastrcv:7 lastack:7 pacing_rate 72200677960bps delivery_rate 8874666664bps delivered:2 rcv_space:33280 rcv_ssthresh:33280 minrtt:0.015 snd_wnd:33280 tcp-ulp-mptcp flags:Mmec token:0000(id:0)/39429ce(id:0) seq:e3ed00de37c805c sfseq:1 ssnoff:d4e4d561 maplen:0
'''

We only care about this 'tcp-ulp-mptcp' item.

Show all output will confuse users. So we just pick and test the only
item we care.

> 
> > +	if (!ASSERT_OK(system(cmd), "No tcp-ulp-mptcp found!"))
> > +		err++;
> > +
> > +	snprintf(cmd, sizeof(cmd),
> > +		 "ip netns exec %s nstat -asz %s | awk '%s' | grep -q '%s'",
> > +		 NS_TEST, "MPTcpExtMPCapableSYNACKRX",
> > +		 "NR==1 {next} {print $2}", "1");
> 
> The same thing here. Could you show the expected output with
>    ip netns exec %s nstat -asz %s
> ?

The output of 'ip netns exec %s nstat -asz %s' is:

'''
#kernel
MPTcpExtMPCapableSYNACKRX       1                  0.0
'''

The same, we only check if it contains an MPTcpExtMPCapableSYNACKRX, not
show the output.

-Geliang

> 
> > +	if (!ASSERT_OK(system(cmd), "No MPTcpExtMPCapableSYNACKRX found!"))
> > +		err++;
> > +
> > +	return err;
> > +}
> > +
> [...]
Yonghong Song Aug. 4, 2023, 4:26 a.m. UTC | #4 
On 8/3/23 7:24 PM, Geliang Tang wrote:
> Hi Yonghong,
> 
> On Thu, Aug 03, 2023 at 06:23:57PM -0700, Yonghong Song wrote:
>>
>>
>> On 8/3/23 6:41 AM, Geliang Tang wrote:
>>> Implement a new test program mptcpify: if the family is AF_INET or
>>> AF_INET6, the type is SOCK_STREAM, and the protocol ID is 0 or
>>> IPPROTO_TCP, set it to IPPROTO_MPTCP. It will be hooked in
>>> update_socket_protocol().
>>>
>>> Extend the MPTCP test base, add a selftest test_mptcpify() for the
>>> mptcpify case. Open and load the mptcpify test prog to mptcpify the
>>> TCP sockets dynamically, then use start_server() and connect_to_fd()
>>> to create a TCP socket, but actually what's created is an MPTCP
>>> socket, which can be verified through the outputs of 'ss' and 'nstat'
>>> commands.
>>>
>>> Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
>>> Signed-off-by: Geliang Tang <geliang.tang@suse.com>
>>> ---
>>>    .../testing/selftests/bpf/prog_tests/mptcp.c  | 94 +++++++++++++++++++
>>>    tools/testing/selftests/bpf/progs/mptcpify.c  | 25 +++++
>>>    2 files changed, 119 insertions(+)
>>>    create mode 100644 tools/testing/selftests/bpf/progs/mptcpify.c
>>>
>>> diff --git a/tools/testing/selftests/bpf/prog_tests/mptcp.c b/tools/testing/selftests/bpf/prog_tests/mptcp.c
>>> index 4407bd5c9e9a..caab3aa6a162 100644
>>> --- a/tools/testing/selftests/bpf/prog_tests/mptcp.c
>>> +++ b/tools/testing/selftests/bpf/prog_tests/mptcp.c
>>> @@ -6,6 +6,7 @@
>>>    #include "cgroup_helpers.h"
>>>    #include "network_helpers.h"
>>>    #include "mptcp_sock.skel.h"
>>> +#include "mptcpify.skel.h"
>>>    char NS_TEST[32];
>>> @@ -195,8 +196,101 @@ static void test_base(void)
>>>    	close(cgroup_fd);
>>>    }
>>> +static void send_byte(int fd)
>>> +{
>>> +	char b = 0x55;
>>> +
>>> +	ASSERT_EQ(write(fd, &b, sizeof(b)), 1, "send single byte");
>>> +}
>>> +
>>> +static int verify_mptcpify(void)
>>> +{
>>> +	char cmd[256];
>>> +	int err = 0;
>>> +
>>> +	snprintf(cmd, sizeof(cmd),
>>> +		 "ip netns exec %s ss -tOni | grep -q '%s'",
>>> +		 NS_TEST, "tcp-ulp-mptcp");
>>
>> Could you show what is the expected output from the above command line
>>    ip netns exec %s ss -tOni
>> ?
>> This way, users can easily reason about the ss states based on tests.
> 
> There're too many items in the output of command 'ip netns exec %s ss -tOni':
> 
> '''
> State Recv-Q Send-Q Local Address:Port  Peer Address:Port Process
> ESTAB 0      0          127.0.0.1:42225    127.0.0.1:44180 cubic wscale:7,7 rto:201 rtt:0.034/0.017 ato:40 mss:16640 pmtu:65535 rcvmss:536 advmss:65483 cwnd:10 bytes_received:1 segs_out:1 segs_in:3 data_segs_in:1 send 39152941176bps lastsnd:7 lastrcv:7 lastack:7 pacing_rate 78305882352bps delivered:1 app_limited rcv_space:33280 rcv_ssthresh:33280 minrtt:0.034 snd_wnd:33280 tcp-ulp-mptcp flags:Mec token:0000(id:0)/3a1e0d3c(id:0) seq:c2802f11c5228db6 sfseq:1 ssnoff:49d3c135 maplen:1
> ESTAB 0      0          127.0.0.1:44180    127.0.0.1:42225 cubic wscale:7,7 rto:201 rtt:0.036/0.02 mss:16640 pmtu:65535 rcvmss:536 advmss:65483 cwnd:10 bytes_sent:1 bytes_acked:2 segs_out:3 segs_in:2 data_segs_out:1 send 36977777778bps lastsnd:7 lastrcv:7 lastack:7 pacing_rate 72200677960bps delivery_rate 8874666664bps delivered:2 rcv_space:33280 rcv_ssthresh:33280 minrtt:0.015 snd_wnd:33280 tcp-ulp-mptcp flags:Mmec token:0000(id:0)/39429ce(id:0) seq:e3ed00de37c805c sfseq:1 ssnoff:d4e4d561 maplen:0
> '''
> 
> We only care about this 'tcp-ulp-mptcp' item.
> 
> Show all output will confuse users. So we just pick and test the only
> item we care.

Thanks. Originally I thought at least we should put one line in
the comment which has 'tcp-ulp-mptcp' like

ESTAB 0      0          127.0.0.1:44180    127.0.0.1:42225 cubic 
wscale:7,7 rto:201 rtt:0.036/0.02 mss:16640 pmtu:65535 rcvmss:536 
advmss:65483 cwnd:10 bytes_sent:1 bytes_acked:2 segs_out:3 segs_in:2 
data_segs_out:1 send 36977777778bps lastsnd:7 lastrcv:7 lastack:7 
pacing_rate 72200677960bps delivery_rate 8874666664bps delivered:2 
rcv_space:33280 rcv_ssthresh:33280 minrtt:0.015 snd_wnd:33280 
tcp-ulp-mptcp flags:Mmec token:0000(id:0)/39429ce(id:0) 
seq:e3ed00de37c805c sfseq:1 ssnoff:d4e4d561 maplen:0

or simplified version

ESTAB 0      0          127.0.0.1:44180    127.0.0.1:42225 cubic
... tcp-ulp-mptcp flags:Mmec ...

But people familiar with 'ss' should be able to dump it and get
the above (maybe without tcp-ulp-mptcp) easily. So I am okay
with no additional comments.

> 
>>
>>> +	if (!ASSERT_OK(system(cmd), "No tcp-ulp-mptcp found!"))
>>> +		err++;
>>> +
>>> +	snprintf(cmd, sizeof(cmd),
>>> +		 "ip netns exec %s nstat -asz %s | awk '%s' | grep -q '%s'",
>>> +		 NS_TEST, "MPTcpExtMPCapableSYNACKRX",
>>> +		 "NR==1 {next} {print $2}", "1");
>>
>> The same thing here. Could you show the expected output with
>>     ip netns exec %s nstat -asz %s
>> ?
> 
> The output of 'ip netns exec %s nstat -asz %s' is:
> 
> '''
> #kernel
> MPTcpExtMPCapableSYNACKRX       1                  0.0
> '''
> 
> The same, we only check if it contains an MPTcpExtMPCapableSYNACKRX, not
> show the output.
> 
> -Geliang
> 
>>
>>> +	if (!ASSERT_OK(system(cmd), "No MPTcpExtMPCapableSYNACKRX found!"))
>>> +		err++;
>>> +
>>> +	return err;
>>> +}
>>> +
>> [...]
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/prog_tests/mptcp.c b/tools/testing/selftests/bpf/prog_tests/mptcp.c
index 4407bd5c9e9a..caab3aa6a162 100644
--- a/tools/testing/selftests/bpf/prog_tests/mptcp.c
+++ b/tools/testing/selftests/bpf/prog_tests/mptcp.c
@@ -6,6 +6,7 @@ 
 #include "cgroup_helpers.h"
 #include "network_helpers.h"
 #include "mptcp_sock.skel.h"
+#include "mptcpify.skel.h"
 
 char NS_TEST[32];
 
@@ -195,8 +196,101 @@  static void test_base(void)
 	close(cgroup_fd);
 }
 
+static void send_byte(int fd)
+{
+	char b = 0x55;
+
+	ASSERT_EQ(write(fd, &b, sizeof(b)), 1, "send single byte");
+}
+
+static int verify_mptcpify(void)
+{
+	char cmd[256];
+	int err = 0;
+
+	snprintf(cmd, sizeof(cmd),
+		 "ip netns exec %s ss -tOni | grep -q '%s'",
+		 NS_TEST, "tcp-ulp-mptcp");
+	if (!ASSERT_OK(system(cmd), "No tcp-ulp-mptcp found!"))
+		err++;
+
+	snprintf(cmd, sizeof(cmd),
+		 "ip netns exec %s nstat -asz %s | awk '%s' | grep -q '%s'",
+		 NS_TEST, "MPTcpExtMPCapableSYNACKRX",
+		 "NR==1 {next} {print $2}", "1");
+	if (!ASSERT_OK(system(cmd), "No MPTcpExtMPCapableSYNACKRX found!"))
+		err++;
+
+	return err;
+}
+
+static int run_mptcpify(int cgroup_fd)
+{
+	int server_fd, client_fd, prog_fd, err = 0;
+	struct mptcpify *mptcpify_skel;
+
+	mptcpify_skel = mptcpify__open_and_load();
+	if (!ASSERT_OK_PTR(mptcpify_skel, "skel_open_load"))
+		return -EIO;
+
+	err = mptcpify__attach(mptcpify_skel);
+	if (!ASSERT_OK(err, "skel_attach"))
+		goto out;
+
+	prog_fd = bpf_program__fd(mptcpify_skel->progs.mptcpify);
+	if (!ASSERT_GE(prog_fd, 0, "bpf_program__fd")) {
+		err = -EIO;
+		goto out;
+	}
+
+	/* without MPTCP */
+	server_fd = start_server(AF_INET, SOCK_STREAM, NULL, 0, 0);
+	if (!ASSERT_GE(server_fd, 0, "start_server")) {
+		err = -EIO;
+		goto out;
+	}
+
+	client_fd = connect_to_fd(server_fd, 0);
+	if (!ASSERT_GE(client_fd, 0, "connect to fd")) {
+		err = -EIO;
+		goto close_server;
+	}
+
+	send_byte(client_fd);
+	err += verify_mptcpify();
+
+	close(client_fd);
+close_server:
+	close(server_fd);
+out:
+	mptcpify__destroy(mptcpify_skel);
+	return err;
+}
+
+static void test_mptcpify(void)
+{
+	struct nstoken *nstoken = NULL;
+	int cgroup_fd;
+
+	cgroup_fd = test__join_cgroup("/mptcpify");
+	if (!ASSERT_GE(cgroup_fd, 0, "test__join_cgroup"))
+		return;
+
+	nstoken = create_netns();
+	if (!ASSERT_OK_PTR(nstoken, "create_netns"))
+		goto fail;
+
+	ASSERT_OK(run_mptcpify(cgroup_fd), "run_mptcpify");
+
+fail:
+	cleanup_netns(nstoken);
+	close(cgroup_fd);
+}
+
 void test_mptcp(void)
 {
 	if (test__start_subtest("base"))
 		test_base();
+	if (test__start_subtest("mptcpify"))
+		test_mptcpify();
 }
diff --git a/tools/testing/selftests/bpf/progs/mptcpify.c b/tools/testing/selftests/bpf/progs/mptcpify.c
new file mode 100644
index 000000000000..9cf1febe982d
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/mptcpify.c
@@ -0,0 +1,25 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023, SUSE. */
+
+#include <linux/bpf.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+#define	AF_INET		2
+#define	AF_INET6	10
+#define	SOCK_STREAM	1
+#define	IPPROTO_TCP	6
+#define	IPPROTO_MPTCP	262
+
+SEC("fmod_ret/update_socket_protocol")
+int BPF_PROG(mptcpify, int family, int type, int protocol)
+{
+	if ((family == AF_INET || family == AF_INET6) &&
+	    type == SOCK_STREAM &&
+	    (!protocol || protocol == IPPROTO_TCP)) {
+		return IPPROTO_MPTCP;
+	}
+
+	return protocol;
+}