tests/netinet: add UDP socket I/O tests

Start a file that would collect tests for I/O functionality of a UDP
socket, targeted on how a socket interacts with userland rather than with
wire side of the protocol.

First version tests that MSG_TRUNC and MSG_PEEK are working correctly.

tests/sys/netinet/Makefile

@@ -12,7 +12,8 @@ ATF_TESTS_C=	ip_reass_test \
 		socket_afinet \
 		tcp_connect_port_test \
 		tcp_implied_connect \
-		tcp_md5_getsockopt
+		tcp_md5_getsockopt \
+		udp_io
 
 ATF_TESTS_SH=	arp \
 		carp \

tests/sys/netinet/udp_io.c

@@ -0,0 +1,139 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2024 Gleb Smirnoff <glebius@FreeBSD.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <atf-c.h>
+
+/*
+ * Create a pair of UDP sockets.  The first one is bound to a local
+ * address and the second one is connected to it.
+ */
+static void
+udp_socketpair(int *s)
+{
+	struct sockaddr_in sin = {
+		.sin_family = AF_INET,
+		.sin_len = sizeof(sin),
+	};
+	socklen_t slen = sizeof(sin);
+	int b, c;
+
+	ATF_REQUIRE((b = socket(PF_INET, SOCK_DGRAM, 0)) > 0);
+	ATF_REQUIRE((c = socket(PF_INET, SOCK_DGRAM, 0)) > 0);
+	ATF_REQUIRE(bind(b, (struct sockaddr *)&sin, sizeof(sin)) == 0);
+	ATF_REQUIRE(getsockname(b, (struct sockaddr *)&sin, &slen) == 0);
+	ATF_REQUIRE(connect(c, (struct sockaddr *)&sin, sizeof(sin)) == 0);
+
+	s[0] = b;
+	s[1] = c;
+}
+
+/*
+ * Check MSG_TRUNC.
+ */
+ATF_TC_WITHOUT_HEAD(trunc);
+ATF_TC_BODY(trunc, tc)
+{
+	char sbuf[] = "Hello, peer!", rbuf[sizeof(sbuf)];
+	struct iovec iov = {
+		.iov_base = sbuf,
+		.iov_len = sizeof(sbuf),
+	};
+	struct msghdr msg = {
+		.msg_iov = &iov,
+		.msg_iovlen = 1,
+	};
+	int s[2];
+	u_int n;
+
+	udp_socketpair(s);
+
+	ATF_REQUIRE(sendmsg(s[1], &msg, 0) == sizeof(sbuf));
+	n = (arc4random() % (sizeof(sbuf) - 1)) + 1;
+	iov.iov_base = rbuf;
+	iov.iov_len = n;
+	ATF_REQUIRE(recvmsg(s[0], &msg, 0) == n);
+	ATF_REQUIRE(msg.msg_flags == MSG_TRUNC);
+	ATF_REQUIRE(strncmp(sbuf, rbuf, n) == 0);
+	iov.iov_len = sizeof(rbuf);
+	ATF_REQUIRE(recvmsg(s[0], &msg, MSG_DONTWAIT) == -1);
+	ATF_REQUIRE(errno == EAGAIN);
+
+	close(s[0]);
+	close(s[1]);
+}
+
+/*
+ * Check MSG_PEEK.
+ */
+ATF_TC_WITHOUT_HEAD(peek);
+ATF_TC_BODY(peek, tc)
+{
+	char sbuf[] = "Hello, peer!", rbuf[sizeof(sbuf)];
+	struct iovec iov = {
+		.iov_base = sbuf,
+		.iov_len = sizeof(sbuf),
+	};
+	struct msghdr msg = {
+		.msg_iov = &iov,
+		.msg_iovlen = 1,
+	};
+	int s[2];
+	u_int n;
+
+	udp_socketpair(s);
+
+	ATF_REQUIRE(sendmsg(s[1], &msg, 0) == sizeof(sbuf));
+	iov.iov_base = rbuf;
+	for (int i = 0; i < 10; i++) {
+		n = (arc4random() % sizeof(sbuf)) + 1;
+		iov.iov_len = n;
+		ATF_REQUIRE(recvmsg(s[0], &msg, MSG_PEEK) == n);
+		if (n < sizeof(sbuf))
+			ATF_REQUIRE(msg.msg_flags == (MSG_PEEK | MSG_TRUNC));
+		else
+			ATF_REQUIRE(msg.msg_flags == MSG_PEEK);
+		ATF_REQUIRE(strncmp(sbuf, rbuf, n) == 0);
+	}
+
+	close(s[0]);
+	close(s[1]);
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+	ATF_TP_ADD_TC(tp, trunc);
+	ATF_TP_ADD_TC(tp, peek);
+
+	return (atf_no_error());
+}