The following code sets up two connected TCP sockets that send data to each

other until the window is closed. Then one of the sockets is closed, which
will generate a RST once the TCP at the other socket does a window probe.

All versions of FreeBSD prior to 11/26/2004 will ignore this RST into a 0
window, causing the connection (and application) to hang indefinitely.
On patched versions of FreeBSD (and other operating systems), the RST
will be accepted and the program will exit in a few seconds.

Submitted by:	Michiel Boland
Reviewed by:	silby

tools/regression/netinet/tcpfullwindowrst/Makefile

@@ -0,0 +1,6 @@
+# $FreeBSD$
+
+PROG=	tcpfullwindowrsttest
+NOMAN=	noman
+
+.include <bsd.prog.mk>

tools/regression/netinet/tcpfullwindowrst/tcpfullwindowrst.t

@@ -0,0 +1,7 @@
+#!/bin/sh
+#
+# $FreeBSD$
+
+make tcpfullwindowrsttest 2>&1 > /dev/null
+
+./tcpfullwindowrsttest

tools/regression/netinet/tcpfullwindowrst/tcpfullwindowrsttest.c

@@ -0,0 +1,131 @@
+/*
+Copyright 2004 Michiel Boland.  All rights reserved.
+
+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 ``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.
+
+$FreeBSD$
+
+*/
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <unistd.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <string.h>
+
+/*
+ * The following code sets up two connected TCP sockets that send data to each
+ * other until the window is closed. Then one of the sockets is closed, which
+ * will generate a RST once the TCP at the other socket does a window probe.
+ *
+ * All versions of FreeBSD prior to 11/26/2004 will ignore this RST into a 0
+ * window, causing the connection (and application) to hang indefinitely.
+ * On patched versions of FreeBSD (and other operating systems), the RST
+ * will be accepted and the program will exit in a few seconds.
+ */
+
+/*
+ * If the alarm fired then we've hung and the test failed.
+ */
+void
+do_alrm(int s)
+{
+	printf("not ok 1 - tcpfullwindowrst\n");
+	exit(0);
+}
+
+int
+main(void)
+{
+	int o, s, t, u, do_t, do_u;
+	struct pollfd pfd[2];
+	struct sockaddr_in sa;
+	char buf[4096];
+
+	printf("1..1\n");
+	signal(SIGALRM, do_alrm);
+	alarm(20);
+
+	s = socket(AF_INET, SOCK_STREAM, 0);
+	if (s == -1)
+		return 1;
+	o = 1;
+	setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &o, sizeof o);
+	memset(&sa, 0, sizeof sa);
+	sa.sin_family = AF_INET;
+	sa.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+	sa.sin_port = htons(3737);
+	if (bind(s, (struct sockaddr *) &sa, sizeof sa) == -1)
+		return 1;
+	if (listen(s, 1) == -1)
+		return 1;
+	t = socket(AF_INET, SOCK_STREAM, 0);
+	if (t == -1)
+		return 1;
+	if (connect(t, (struct sockaddr *) &sa, sizeof sa) == -1)
+		return 1;
+	u = accept(s, 0, 0);
+	if (u == -1)
+		return 1;
+	close(s);
+	fcntl(t, F_SETFL, fcntl(t, F_GETFL) | O_NONBLOCK);
+	fcntl(u, F_SETFL, fcntl(t, F_GETFL) | O_NONBLOCK);
+	do_t = 1;
+	do_u = 1;
+	pfd[0].fd = t;
+	pfd[0].events = POLLOUT;
+	pfd[1].fd = u;
+	pfd[1].events = POLLOUT;
+	while (do_t || do_u) {
+		if (poll(pfd, 2, 1000) == 0) {
+			if (do_t) {
+				close(t);
+				pfd[0].fd = -1;
+				do_t = 0;
+			}
+			continue;
+		}
+		if (pfd[0].revents & POLLOUT) {
+			if (write(t, buf, sizeof buf) == -1) {
+				close(t);
+				pfd[0].fd = -1;
+				do_t = 0;
+			}
+		}
+		if (pfd[1].revents & POLLOUT) {
+			if (write(u, buf, sizeof buf) == -1) {
+				close(u);
+				pfd[1].fd = -1;
+				do_u = 0;
+			}
+		}
+	}
+
+	printf("ok 1 - tcpfullwindowrst\n");
+	return 0;
+}