From 97926373401e4e794fa90f87b42c6cac9c35daf7 Mon Sep 17 00:00:00 2001
From: Ihar Hrachyshka <ihrachys@redhat.com>
Date: Mon, 22 Oct 2018 21:25:46 +0100
Subject: arping: support -i interval option

This option will allow to set time interval to use between packets sent.

It may become handy to work around timing issues in the network.  For
example, Linux kernel as of the time of writing by default ignores all ARP
updates that arrive in 1-second interval since previous update for the same
table entry *irrespective of whether the previous update was ignored*.  It
means that calling apring with -c 3 may still not affect Linux network peers
because every consequent update is ignored because of the previous ARP
update (that was also ignored).

In this scenario, we would now be able to call arping -i 2 to work that
kernel behaviour around.

Linux fix can be found in: https://patchwork.ozlabs.org/patch/760372/
---
 arping.c       | 9 +++++++--
 doc/arping.xml | 6 ++++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/arping.c b/arping.c
index 3998d97..80acad0 100644
--- a/arping.c
+++ b/arping.c
@@ -79,6 +79,7 @@ int dad, unsolicited, advert;
 int quiet;
 int count = -1;
 int timeout;
+unsigned int interval = 1;
 int unicasting;
 int socketfd;
 int broadcast_only;
@@ -125,6 +126,7 @@ void usage(void)
 		"  -V            print version and exit\n"
 		"  -c <count>    how many packets to send\n"
 		"  -w <timeout>  how long to wait for a reply\n"
+		"  -i <interval> set interval between packets (default: 1 second)\n"
 		"  -I <device>   which ethernet device to use"
 #ifdef DEFAULT_DEVICE_STR
 				"(" DEFAULT_DEVICE_STR ")"
@@ -382,7 +384,7 @@ void catcher(void)
 			 * unsolicited mode */
 			finish();
 	}
-	alarm(1);
+	alarm(interval);
 }
 
 void print_hex(unsigned char *p, int len)
@@ -1004,7 +1006,7 @@ main(int argc, char **argv)
 
 	disable_capability_raw();
 
-	while ((ch = getopt(argc, argv, "h?bfDUAqc:w:s:I:V")) != EOF) {
+	while ((ch = getopt(argc, argv, "h?bfDUAqc:w:i:s:I:V")) != EOF) {
 		switch(ch) {
 		case 'b':
 			broadcast_only=1;
@@ -1029,6 +1031,9 @@ main(int argc, char **argv)
 		case 'w':
 			timeout = atoi(optarg);
 			break;
+		case 'i':
+			interval = (unsigned int)atoi(optarg);
+			break;
 		case 'I':
 			device.name = optarg;
 			break;
diff --git a/doc/arping.xml b/doc/arping.xml
index a20e3be..0c7db21 100644
--- a/doc/arping.xml
+++ b/doc/arping.xml
@@ -23,6 +23,7 @@
     <arg choice='opt'>-AbDfhqUV </arg>
     <arg choice='opt'>-c <replaceable>count</replaceable></arg>
     <arg choice='opt'>-w <replaceable>deadline</replaceable></arg>
+    <arg choice='opt'>-i <replaceable>interval</replaceable></arg>
     <arg choice='opt'>-s <replaceable>source</replaceable></arg>
     <arg choice='opt'>-I <replaceable>interface</replaceable></arg>
     <arg choice='plain'><replaceable>destination</replaceable></arg>
@@ -133,6 +134,11 @@ expire or until
 probes are answered.</para>
   </listitem>
   </varlistentry>
+  <varlistentry>
+  <term><option>-i </option><emphasis remap='I'>interval</emphasis></term>
+  <listitem><para>Specify an interval, in seconds, between packets.</para>
+  </listitem>
+  </varlistentry>
 </variablelist>
 </refsect1>
 
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