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

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Message-ID: <20220517013217.oxbpwjilwr4fzvuv@kafai-mbp.dhcp.thefacebook.com>
Date:   Mon, 16 May 2022 18:32:17 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Geliang Tang <geliang.tang@...e.com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org, ast@...nel.org,
        daniel@...earbox.net, andrii@...nel.org, 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

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 ?

> + */
> +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;
> +}
> +