ping: Add option -H to force reverse DNS resolution

Forcing DNS name resolution is useful for numeric destination,
or -f option, which by default do not perform it.

-H overrides previously defined -n, -n overrides previously defined -H
(useful, when one of them is in alias it can still be overridden).

Fixes: https://github.com/iputils/iputils/issues/421
Fixes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=650479
Closes: https://github.com/iputils/iputils/pull/494
Reported-by: Vincent Lefevre <vincent@vinc17.net>
Reported-by: Michele Guerini Rocco <rnhmjoj@inventati.org>
Reviewed-by: Vincent Lefevre <vincent@vinc17.net>
Reviewed-by: Cyril Hrubis <chrubis@suse.cz>
Reviewed-by: Guillaume Nault <guillaume.nault@wanadoo.fr>
Signed-off-by: Petr Vorel <pvorel@suse.cz>

4 files changed, 24 insertions, 5 deletions

diff --git a/doc/ping.xml b/doc/ping.xml
index 3bc0767..9e3a0f9 100644
--- a/doc/ping.xml
+++ b/doc/ping.xml
@@ -24,7 +24,7 @@ xml:id="man.ping">
     <cmdsynopsis sepchar=" ">
       <command>ping</command>
       <arg choice="opt" rep="norepeat">
-        <option>-aAbBdCDfhLnOqrRUvV46</option>
+        <option>-aAbBdCDfhHLnOqrRUvV46</option>
       </arg>
       <arg choice="opt" rep="norepeat">
         <option>-c
@@ -274,6 +274,17 @@ xml:id="man.ping">
       </varlistentry>
       <varlistentry>
         <term>
+          <option>-H</option>
+        </term>
+        <listitem>
+          <para>Force DNS name resolution for the output. Useful for numeric
+          destination, or <option>-f</option> option, which by default do not
+          perform it. Override previously defined <option>-n</option> option.
+          </para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term>
           <option>-i</option>
           <emphasis remap="I">interval</emphasis>
         </term>
@@ -526,7 +537,8 @@ xml:id="man.ping">
           <para>Numeric output only. No attempt will be made to lookup
           symbolic names for host addresses (no reverse DNS resolution).
           This is the default for numeric destination or <option>-f</option>
-          option.</para>
+          option.  Override previously defined <option>-H</option> option.
+          </para>
         </listitem>
       </varlistentry>
       <varlistentry>
diff --git a/ping/ping.c b/ping/ping.c
index 0ff5a48..32b50cf 100644
--- a/ping/ping.c
+++ b/ping/ping.c
@@ -363,7 +363,7 @@ main(int argc, char **argv)
 		hints.ai_family = AF_INET6;
 
 	/* Parse command line options */
-	while ((ch = getopt(argc, argv, "h?" "4bRT:" "6F:N:" "aABc:CdDe:fi:I:l:Lm:M:nOp:qQ:rs:S:t:UvVw:W:")) != EOF) {
+	while ((ch = getopt(argc, argv, "h?" "4bRT:" "6F:N:" "aABc:CdDe:fHi:I:l:Lm:M:nOp:qQ:rs:S:t:UvVw:W:")) != EOF) {
 		switch(ch) {
 		/* IPv4 specific options */
 		case '4':
@@ -433,6 +433,9 @@ main(int argc, char **argv)
 		case 'D':
 			rts.opt_ptimeofday = 1;
 			break;
+		case 'H':
+			rts.opt_force_lookup = 1;
+			break;
 		case 'i':
 		{
 			double optval;
@@ -496,6 +499,7 @@ main(int argc, char **argv)
 			break;
 		case 'n':
 			rts.opt_numeric = 1;
+			rts.opt_force_lookup = 0;
 			break;
 		case 'O':
 			rts.opt_outstanding = 1;
@@ -1780,7 +1784,7 @@ char *_pr_addr(struct ping_rts *rts, void *sa, socklen_t salen, int resolve_name
 	rts->in_pr_addr = !setjmp(rts->pr_addr_jmp);
 
 	getnameinfo(sa, salen, address, sizeof address, NULL, 0, getnameinfo_flags | NI_NUMERICHOST);
-	if (!rts->exiting && resolve_name && !rts->opt_numeric)
+	if (!rts->exiting && resolve_name && (rts->opt_force_lookup || !rts->opt_numeric))
 		getnameinfo(sa, salen, name, sizeof name, NULL, 0, getnameinfo_flags);
 
 	if (*name && strncmp(name, address, NI_MAXHOST))
diff --git a/ping/ping.h b/ping/ping.h
index 7799395..a40c8f8 100644
--- a/ping/ping.h
+++ b/ping/ping.h
@@ -236,6 +236,7 @@ struct ping_rts {
 		opt_flood:1,
 		opt_flood_poll:1,
 		opt_flowinfo:1,
+		opt_force_lookup:1,
 		opt_interval:1,
 		opt_latency:1,
 		opt_mark:1,
diff --git a/ping/ping_common.c b/ping/ping_common.c
index ac656ba..c8b868b 100644
--- a/ping/ping_common.c
+++ b/ping/ping_common.c
@@ -62,13 +62,15 @@ void usage(void)
 		"                     Imply using SOCK_RAW (for IPv4 only for identifier 0)\n"
 		"  -f                 flood ping\n"
 		"  -h                 print help and exit\n"
+		"  -H                 force reverse DNS name resolution (useful for numeric\n"
+		"                     destinations or for -f), override -n\n"
 		"  -I <interface>     either interface name or address\n"
 		"  -i <interval>      seconds between sending each packet\n"
 		"  -L                 suppress loopback of multicast packets\n"
 		"  -l <preload>       send <preload> number of packages while waiting replies\n"
 		"  -m <mark>          tag the packets going out\n"
 		"  -M <pmtud opt>     define mtu discovery, can be one of <do|dont|want|probe>\n"
-		"  -n                 no reverse DNS name resolution\n"
+		"  -n                 no reverse DNS name resolution, override -H\n"
 		"  -O                 report outstanding replies\n"
 		"  -p <pattern>       contents of padding byte\n"
 		"  -q                 quiet output\n"