tracepath,doc: Added -4, -6 Parameter in doc and void usage(void)

Author: Seishinryohosha

doc/tracepath.sgml

@@ -15,6 +15,8 @@ traces path to a network host discovering MTU along this path</refpurpose>
 <refsynopsisdiv>
 <cmdsynopsis>
 <command>tracepath</command>
+<arg choice="opt">-4</arg>
+<arg choice="opt">-6</arg>
 <arg choice="opt">-n</arg>
 <arg choice="opt">-b</arg>
 <arg choice="opt">-l <replaceable/pktlen/</arg>
@@ -46,6 +48,20 @@ of UDP ports to maintain trace history.
 <refsect1><title>OPTIONS</title>
 <variablelist>
 
+ <varlistentry>
+  <term><option>-4</option></term>
+  <listitem><para>
+Use IPv4 only.
+  </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+  <term><option>-6</option></term>
+  <listitem><para>
+Use IPv6 only.
+  </para></listitem>
+ </varlistentry>
+
  <varlistentry>
   <term><option>-n</option></term>
   <listitem><para>

tracepath.c

@@ -366,7 +366,7 @@ static void usage(void) __attribute((noreturn));
 
 static void usage(void)
 {
-	fprintf(stderr, "Usage: tracepath [-n] [-b] [-l <len>] [-p port] <destination>\n");
+	fprintf(stderr, "Usage: tracepath [-4] [-6] [-n] [-b] [-l <len>] [-p port] <destination>\n");
 	exit(-1);
 }