linux-kernel - Re: [PATCH bpf-next v2 5/9] selftests/bpf: Add selftest for sockmap/hashmap redirection

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Message-ID: <66bf942f-dfdb-4ce9-bd95-8b734e7afa53@rbox.co>
Date: Wed, 16 Apr 2025 14:33:20 +0200
From: Michal Luczaj <mhal@...x.co>
To: Jiayuan Chen <mrpre@....com>
Cc: Andrii Nakryiko <andrii@...nel.org>, Eduard Zingerman
 <eddyz87@...il.com>, Mykola Lysenko <mykolal@...com>,
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>,
 Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, Shuah Khan <shuah@...nel.org>,
 Jonathan Corbet <corbet@....net>, bpf@...r.kernel.org,
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org, Jakub Sitnicki <jakub@...udflare.com>
Subject: Re: [PATCH bpf-next v2 5/9] selftests/bpf: Add selftest for
 sockmap/hashmap redirection

On 4/11/25 16:31, Jiayuan Chen wrote:
> On Fri, Apr 11, 2025 at 01:32:41PM +0200, Michal Luczaj wrote:
>> +static void test_send_redir_recv(int sd_send, int send_flags, int sd_peer,
>> +				 int sd_in, int sd_out, int sd_recv,
>> +				 struct maps *maps, int status)
>> +{
>> +	unsigned int drop, pass;
>> +	char *send_buf = "ab";
>> +	char recv_buf = '\0';
>> +	ssize_t n, len = 1;
>> +	/* Zero out the verdict map */
>> +	if (xbpf_map_update_elem(maps->verd, &u32(SK_DROP), &u32(0), BPF_ANY) ||
>> +	    xbpf_map_update_elem(maps->verd, &u32(SK_PASS), &u32(0), BPF_ANY))
>> +		return;
>> +
>> +	if (xbpf_map_update_elem(maps->in, &u32(0), &u64(sd_in), BPF_NOEXIST))
>> +		return;
>> +
>> +	if (xbpf_map_update_elem(maps->out, &u32(0), &u64(sd_out), BPF_NOEXIST))
>> +		goto del_in;
>> +
>> +	/* Last byte is OOB data when send_flags has MSG_OOB bit set */
>> +	if (send_flags & MSG_OOB)
>> +		len++;
>> +	n = send(sd_send, send_buf, len, send_flags);
>> +	if (n >= 0 && n < len)
>> +		FAIL("incomplete send");
>> +	if (n < 0) {
>> +		/* sk_msg redirect combo not supported? */
>> +		if (status & SUPPORTED || errno != EACCES)
>> +			FAIL_ERRNO("send");
>> +		goto out;
>> +	}
>> +
>> +	if (!(status & SUPPORTED)) {
>> +		handle_unsupported(sd_send, sd_peer, sd_in, sd_out, sd_recv,
>> +				   maps->verd, status);
>> +		goto out;
>> +	}
>> +
>> +	errno = 0;
>> +	n = recv_timeout(sd_recv, &recv_buf, 1, 0, IO_TIMEOUT_SEC);
>> +	if (n != 1) {
>> +		FAIL_ERRNO("recv_timeout()");
>> +		goto out;
>> +	}
> I prefer multiple send and receive operations, or implementing a loop at
> the outer level.

If you referring to MSG_OOB that "emulates" multiple send(), that's quite
deliberate: to exercise what is actually happening on
unix_stream_sendmsg(, MSG_OOB). And, well, to follow the selftests logic
in sockmap_listen.c:pairs_redir_to_connected().

Would you rather have it split anyway?

Thanks,
Michal