Subject: Re: [PATCH bpf-next v9 4/4] selftests/bpf: Add mptcpify test

From: Geliang Tang <[email-masked]>
Date: Fri, 4 Aug 2023 10:24:59 +0800

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 <[email-masked]>
> > Signed-off-by: Geliang Tang <[email-masked]>
> > ---
> >   .../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;
> > +}
> > +
> [...]