netdev - Re: [PATCH bpf-next v4 5/7] selftests/bpf: verify token of struct mptcp

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Date:   Tue, 17 May 2022 13:19:38 +0800
From:   Geliang Tang <geliangtang@...il.com>
To:     Martin KaFai Lau <kafai@...com>
Cc:     Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Geliang Tang <geliang.tang@...e.com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        MPTCP Upstream <mptcp@...ts.linux.dev>,
        Matthieu Baerts <matthieu.baerts@...sares.net>
Subject: Re: [PATCH bpf-next v4 5/7] selftests/bpf: verify token of struct mptcp_sock

Martin KaFai Lau <kafai@...com> 于2022年5月17日周二 09:32写道：
>
> On Fri, May 13, 2022 at 03:48:25PM -0700, Mat Martineau wrote:
> [ ... ]
>
> > +/*
> > + * Parse the token from the output of 'ip mptcp monitor':
> > + *
> > + * [       CREATED] token=3ca933d3 remid=0 locid=0 saddr4=127.0.0.1 ...
> > + * [       CREATED] token=2ab57040 remid=0 locid=0 saddr4=127.0.0.1 ...
> How stable is the string format ?
>
> If it happens to have some unrelated mptcp connection going on, will the test
> break ?

Hi Martin,

Yes, it will break in that case. How can I fix this? Should I run the
test in a special net namespace?

'ip mptcp monitor' can easily run in a special net namespace:

ip -net ns1 mptcp monitor

But I don't know how to run start_server() and connect_to_fd() in a
special namespace. Could you please give me some suggestions about
this?

Thanks,
-Geliang

>
> > + */
> > +static __u32 get_msk_token(void)
> > +{
> > +     char *prefix = "[       CREATED] token=";
> > +     char buf[BUFSIZ] = {};
> > +     __u32 token = 0;
> > +     ssize_t len;
> > +     int fd;
> > +
> > +     sync();
> > +
> > +     fd = open(monitor_log_path, O_RDONLY);
> > +     if (!ASSERT_GE(fd, 0, "Failed to open monitor_log_path"))
> > +             return token;
> > +
> > +     len = read(fd, buf, sizeof(buf));
> > +     if (!ASSERT_GT(len, 0, "Failed to read monitor_log_path"))
> > +             goto err;
> > +
> > +     if (strncmp(buf, prefix, strlen(prefix))) {
> > +             log_err("Invalid prefix %s", buf);
> > +             goto err;
> > +     }
> > +
> > +     token = strtol(buf + strlen(prefix), NULL, 16);
> > +
> > +err:
> > +     close(fd);
> > +     return token;
> > +}
> > +
>