Resolves: #1444281

commit f3c189e26b3ba803b703d724e831e59390d0af13
Author: Jan Synacek <jsynacek@redhat.com>
Date:   Mon May 15 12:07:59 2017 +0200

    ping: fix pmtu discovery for ipv6
    
    Fixes: #40

diff --git a/ping.c b/ping.c
index 45cca8d..fade2c9 100644
--- a/ping.c
+++ b/ping.c
@@ -107,7 +107,7 @@ int cmsg_len;
 
 static struct sockaddr_in source = { .sin_family = AF_INET };
 char *device;
-static int pmtudisc = -1;
+int pmtudisc = -1;
 
 static void create_socket(socket_st *sock, int family, int socktype, int protocol, int requisite)
 {
@@ -498,8 +498,14 @@ main(int argc, char **argv)
 	enable_capability_raw();
 	if (hints.ai_family != AF_INET6)
 		create_socket(&sock4, AF_INET, hints.ai_socktype, IPPROTO_ICMP, hints.ai_family == AF_INET);
-	if (hints.ai_family != AF_INET)
+	if (hints.ai_family != AF_INET) {
 		create_socket(&sock6, AF_INET6, hints.ai_socktype, IPPROTO_ICMPV6, sock4.fd == -1);
+		/* This may not be needed if both protocol versions always had the same value, but
+		 * since I don't know that, it's better to be safe than sorry. */
+		pmtudisc = pmtudisc == IP_PMTUDISC_DO   ? IPV6_PMTUDISC_DO :
+			   pmtudisc == IP_PMTUDISC_DONT ? IPV6_PMTUDISC_DONT :
+			   pmtudisc == IP_PMTUDISC_WANT ? IPV6_PMTUDISC_WANT : pmtudisc;
+	}
 	disable_capability_raw();
 
 	/* Limit address family on single-protocol systems */
diff --git a/ping.h b/ping.h
index 1253fa0..78e3853 100644
--- a/ping.h
+++ b/ping.h
@@ -168,6 +168,7 @@ extern volatile int status_snapshot;
 extern int confirm;
 extern int confirm_flag;
 extern char *device;
+extern int pmtudisc;
 
 extern volatile int in_pr_addr;		/* pr_addr() is executing */
 extern jmp_buf pr_addr_jmp;
diff --git a/ping6_common.c b/ping6_common.c
index a5627ae..f5c81fd 100644
--- a/ping6_common.c
+++ b/ping6_common.c
@@ -101,7 +101,6 @@ void ping6_usage(unsigned) __attribute((noreturn));
 
 struct sockaddr_in6 source6 = { .sin6_family = AF_INET6 };
 char *device;
-int pmtudisc=-1;
 
 #if defined(USE_GCRYPT) || defined(USE_OPENSSL) || defined(USE_NETTLE)
 #include "iputils_md5dig.h"