Add very basic afinet socket tests which I started to write in order

to then try to reproduce a kernel panic, which turned out to be a
race condition and hard to test from here.

Commit the changes anywhere as the "bind zero" case was a surprise
to me and we should try to maintain this status.

Also it is easy examples someone can build upon.

With help from:	markj
Event:		Waterloo Hackathon 2019

tests/sys/netinet/Makefile

@@ -4,7 +4,8 @@ TESTSDIR=	${TESTSBASE}/sys/netinet
 BINDIR=		${TESTSDIR}
 
 ATF_TESTS_C=	ip_reass_test \
-		so_reuseport_lb_test
+		so_reuseport_lb_test \
+		socket_afinet
 
 ATF_TESTS_SH=	fibs_test
 

tests/sys/netinet/socket_afinet.c

@@ -0,0 +1,97 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2019 Bjoern A. Zeeb
+ *
+ * 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/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/errno.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+
+#include <atf-c.h>
+
+ATF_TC_WITHOUT_HEAD(socket_afinet);
+ATF_TC_BODY(socket_afinet, tc)
+{
+	int sd;
+
+	sd = socket(PF_INET, SOCK_DGRAM, 0);
+	ATF_CHECK(sd >= 0);
+
+	close(sd);
+}
+
+ATF_TC_WITHOUT_HEAD(socket_afinet_bind_zero);
+ATF_TC_BODY(socket_afinet_bind_zero, tc)
+{
+	int sd, rc;
+	struct sockaddr_in sin;
+
+	sd = socket(PF_INET, SOCK_DGRAM, 0);
+	ATF_CHECK(sd >= 0);
+
+	bzero(&sin, sizeof(sin));
+	/*
+	 * For AF_INET we do not check the family in in_pcbbind_setup(9),
+	 * sa_len gets set from the syscall argument in getsockaddr(9),
+	 * so we bind to 0:0.
+	 */
+	rc = bind(sd, (struct sockaddr *)&sin, sizeof(sin));
+	ATF_CHECK_EQ(0, rc);
+
+	close(sd);
+}
+
+ATF_TC_WITHOUT_HEAD(socket_afinet_bind_ok);
+ATF_TC_BODY(socket_afinet_bind_ok, tc)
+{
+	int sd, rc;
+	struct sockaddr_in sin;
+
+	sd = socket(PF_INET, SOCK_DGRAM, 0);
+	ATF_CHECK(sd >= 0);
+
+	bzero(&sin, sizeof(sin));
+	sin.sin_family = AF_INET;
+	sin.sin_len = sizeof(sin);
+	sin.sin_port = htons(6666);
+	sin.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+	rc = bind(sd, (struct sockaddr *)&sin, sizeof(sin));
+	ATF_CHECK_EQ(0, rc);
+
+	close(sd);
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+
+	ATF_TP_ADD_TC(tp, socket_afinet);
+	ATF_TP_ADD_TC(tp, socket_afinet_bind_zero);
+	ATF_TP_ADD_TC(tp, socket_afinet_bind_ok);
+
+	return atf_no_error();
+}