Add a queue to hold packets while we await an ARP reply.

When a fast machine first brings up some non TCP networking program
it is quite possible that we will drop packets due to the fact that
only one packet can be held per ARP entry.  This leads to packets
being missed when a program starts or restarts if the ARP data is
not currently in the ARP cache.

This code adds a new sysctl, net.link.ether.inet.maxhold, which defines
a system wide maximum number of packets to be held in each ARP entry.
Up to maxhold packets are queued until an ARP reply is received or
the ARP times out.  The default setting is the old value of 1
which has been part of the BSD networking code since time
immemorial.

Expose the time we hold an incomplete ARP entry by adding
the sysctl net.link.ether.inet.wait, which defaults to 20
seconds, the value used when the new ARP code was added..

Reviewed by:	bz, rpaulo
MFC after: 3 weeks

3 files changed, 178 insertions, 0 deletions

diff --git a/tools/regression/netinet/arphold/Makefile b/tools/regression/netinet/arphold/Makefile
new file mode 100644
index 0000000..37abefb
--- /dev/null
+++ b/tools/regression/netinet/arphold/Makefile
@@ -0,0 +1,7 @@
+# $FreeBSD$
+
+PROG=	arphold
+NO_MAN=
+CFLAGS+=	-Wall
+
+.include <bsd.prog.mk>
diff --git a/tools/regression/netinet/arphold/arphold.c b/tools/regression/netinet/arphold/arphold.c
new file mode 100644
index 0000000..092461d
--- /dev/null
+++ b/tools/regression/netinet/arphold/arphold.c
@@ -0,0 +1,164 @@
+/*
+ * Copyright (c) 2010 Advanced Computing Technologies LLC
+ * Written by George Neville-Neil gnn@freebsd.org
+ * 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 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.
+ *
+ * Description: The following is a test of the arp entry packet queues
+ * which replaced the single packet hold entry that existed in the BSDs
+ * since time immemorial.  The test process is:
+ *
+ * 1) Find out the current system limit (maxhold)
+ * 2) Using an IP address for which we do not yet have an entry
+ *    load up an ARP entry packet queue with exactly that many packets.
+ * 3) Check the arp dropped stat to make sure that we have not dropped
+ *    any packets as yet.
+ * 4) Add one more packet to the queue.
+ * 5) Make sure that only one packet was dropped.
+ *
+ * CAVEAT: The ARP timer will flush the queue after 1 second so it is
+ * important not to run this code in a fast loop or the test will
+ * fail.
+ *
+ * $FreeBSD$
+ */
+
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/sysctl.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <net/if_arp.h>
+
+#define MSG_SIZE 1024
+#define PORT 6969
+
+int
+main(int argc, char **argv)
+{
+
+	int sock;
+	int maxhold;
+	int wait;
+	size_t size = sizeof(maxhold);
+	struct sockaddr_in dest;
+	char message[MSG_SIZE];
+	struct arpstat arpstat;
+	size_t len = sizeof(arpstat);
+	unsigned long dropped = 0;
+
+	memset(&message, 1, sizeof(message));
+
+	if (sysctlbyname("net.link.ether.inet.maxhold", &maxhold, &size,
+			 NULL, 0) < 0) {
+		perror("not ok 1 - sysctlbyname failed");
+		exit(1);
+	}
+	    
+#ifdef DEBUG
+	printf("maxhold is %d\n", maxhold);
+#endif /* DEBUG */
+
+	if ((sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
+		perror("not ok 1 - could not open socket");
+		exit(1);
+	}
+
+	bzero(&dest, sizeof(dest));
+	if (inet_pton(AF_INET, argv[1], &dest.sin_addr.s_addr) != 1) {
+		perror("not ok 1 - could not parse address");
+		exit(1);
+	}
+	dest.sin_len = sizeof(dest);
+	dest.sin_family = AF_INET;
+	dest.sin_port = htons(PORT);
+
+	if (sysctlbyname("net.link.ether.arp.stats", &arpstat, &len,
+			 NULL, 0) < 0) {
+		perror("not ok 1 - could not get initial arp stats");
+		exit(1);
+	}
+
+	dropped = arpstat.dropped;
+#ifdef DEBUG
+	printf("dropped before %ld\n", dropped);
+#endif /* DEBUG */
+
+	/* 
+	 * Load up the queue in the ARP entry to the maximum.
+	 * We should not drop any packets at this point. 
+	 */
+
+	while (maxhold > 0) {
+		if (sendto(sock, message, sizeof(message), 0,
+			   (struct sockaddr *)&dest, sizeof(dest)) < 0) {
+			perror("not ok 1 - could not send packet");
+			exit(1);
+		}
+		maxhold--;
+	}
+
+	if (sysctlbyname("net.link.ether.arp.stats", &arpstat, &len,
+			 NULL, 0) < 0) {
+		perror("not ok 1 - could not get new arp stats");
+		exit(1);
+	}
+
+#ifdef DEBUG
+	printf("dropped after %ld\n", arpstat.dropped);
+#endif /* DEBUG */
+
+	if (arpstat.dropped != dropped) {
+		printf("not ok 1 - Failed, drops changed:"
+		       "before %ld after %ld\n", dropped, arpstat.dropped);
+		exit(1);
+	}
+	
+	dropped = arpstat.dropped;
+
+	/* Now add one extra and make sure it is dropped. */
+	if (sendto(sock, message, sizeof(message), 0,
+		   (struct sockaddr *)&dest, sizeof(dest)) < 0) {
+		perror("not ok 1 - could not send packet");
+		exit(1);
+	}
+
+	if (sysctlbyname("net.link.ether.arp.stats", &arpstat, &len,
+			 NULL, 0) < 0) {
+		perror("not ok 1 - could not get new arp stats");
+		exit(1);
+	}
+
+	if (arpstat.dropped != (dropped + 1)) {
+		printf("not ok 1 - Failed to drop one packet: before"
+		       " %ld after %ld\n", dropped, arpstat.dropped);
+		exit(1);
+	}
+
+	printf("ok\n");
+	return (0);
+}
diff --git a/tools/regression/netinet/arphold/arphold.t b/tools/regression/netinet/arphold/arphold.t
new file mode 100644
index 0000000..eb1b2a8
--- /dev/null
+++ b/tools/regression/netinet/arphold/arphold.t
@@ -0,0 +1,7 @@
+#!/bin/sh
+#
+# $FreeBSD$
+
+make arphold 2>&1 > /dev/null
+
+./arphold 192.168.1.222