netdev - Re: [PATCH v2 bpf-next/net 6/6] selftest: bpf: Add test for sk->sk_bypass_prot

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Message-ID: <fa80d5a7-790d-4f10-bef3-f5c708218f83@linux.dev>
Date: Wed, 15 Oct 2025 12:07:38 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Kuniyuki Iwashima <kuniyu@...gle.com>
Cc: Alexei Starovoitov <ast@...nel.org>, Andrii Nakryiko <andrii@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 John Fastabend <john.fastabend@...il.com>,
 Stanislav Fomichev <sdf@...ichev.me>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Neal Cardwell <ncardwell@...gle.com>, Willem de Bruijn <willemb@...gle.com>,
 Mina Almasry <almasrymina@...gle.com>,
 Roman Gushchin <roman.gushchin@...ux.dev>,
 Shakeel Butt <shakeel.butt@...ux.dev>, Kuniyuki Iwashima
 <kuni1840@...il.com>, bpf@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2 bpf-next/net 6/6] selftest: bpf: Add test for
 sk->sk_bypass_prot_mem.

On 10/14/25 4:54 PM, Kuniyuki Iwashima wrote:
> +static int tcp_create_sockets(struct test_case *test_case, int sk[], int len)
> +{
> +	int server, i, err = 0;
> +
> +	server = start_server(test_case->family, test_case->type, NULL, 0, 0);
> +	if (!ASSERT_GE(server, 0, "start_server_str"))
> +		return server;
> +
> +	/* Keep for-loop so we can change NR_SOCKETS easily. */
> +	for (i = 0; i < len; i += 2) {
> +		sk[i] = connect_to_fd(server, 0);
> +		if (sk[i] < 0) {
> +			ASSERT_GE(sk[i], 0, "connect_to_fd");
> +			err = sk[i];
> +			break;
> +		}
> +
> +		sk[i + 1] = accept(server, NULL, NULL);
> +		if (sk[i + 1] < 0) {
> +			ASSERT_GE(sk[i + 1], 0, "accept");
> +			err = sk[i + 1];
> +			break;
> +		}
> +	}
> +
> +	close(server);
> +
> +	return err;
> +}
> +

> +static int check_bypass(struct test_case *test_case,
> +			struct sk_bypass_prot_mem *skel, bool bypass)
> +{
> +	char buf[BUF_SINGLE] = {};
> +	long memory_allocated[2];
> +	int sk[NR_SOCKETS] = {};
> +	int err, i, j;
> +
> +	err = test_case->create_sockets(test_case, sk, ARRAY_SIZE(sk));
> +	if (err)
> +		goto close;
> +
> +	memory_allocated[0] = test_case->get_memory_allocated(test_case, skel);
> +
> +	/* allocate pages >= NR_PAGES */
> +	for (i = 0; i < ARRAY_SIZE(sk); i++) {
> +		for (j = 0; j < NR_SEND; j++) {
> +			int bytes = send(sk[i], buf, sizeof(buf), 0);
> +
> +			/* Avoid too noisy logs when something failed. */
> +			if (bytes != sizeof(buf)) {
> +				ASSERT_EQ(bytes, sizeof(buf), "send");
> +				if (bytes < 0) {
> +					err = bytes;
> +					goto drain;
> +				}
> +			}
> +		}
> +	}
> +
> +	memory_allocated[1] = test_case->get_memory_allocated(test_case, skel);
> +
> +	if (bypass)
> +		ASSERT_LE(memory_allocated[1], memory_allocated[0] + 10, "bypass");
> +	else
> +		ASSERT_GT(memory_allocated[1], memory_allocated[0] + NR_PAGES, "no bypass");
> +
> +drain:
> +	if (test_case->type == SOCK_DGRAM) {
> +		/* UDP starts purging sk->sk_receive_queue after one RCU
> +		 * grace period, then udp_memory_allocated goes down,
> +		 * so drain the queue before close().
> +		 */
> +		for (i = 0; i < ARRAY_SIZE(sk); i++) {
> +			for (j = 0; j < NR_SEND; j++) {
> +				int bytes = recv(sk[i], buf, 1, MSG_DONTWAIT | MSG_TRUNC);
> +
> +				if (bytes == sizeof(buf))
> +					continue;
> +				if (bytes != -1 || errno != EAGAIN)
> +					PRINT_FAIL("bytes: %d, errno: %s\n", bytes, strerror(errno));
> +				break;
> +			}
> +		}
> +	}
> +
> +close:
> +	for (i = 0; i < ARRAY_SIZE(sk); i++) {
> +		if (sk[i] <= 0)

Theoretically, 0 is a legit fd. The tcp_create_sockets above is also testing 
ASSERT_GE(sk[i], 0, ...). I changed to test "< 0" here and initialize all sk[] 
to -1 at the beginning of this function.

> +			break;
> +
> +		close(sk[i]);
> +	}
> +
> +	return err;
> +}
> +

> +struct test_case test_cases[] = {

Added static.

Applied. Thanks.