[PATCH iproute2 1/3] ip address: do not set nodad option for IPv4 addresses

[Andrea Claudi <aclaudi@redhat.com>]

Duplicate Address Detection (RFC 4862) is available only for IPv6
addresses. As a consequence, 'nodad' option, turning it off, should
be available only for IPv6, and is defined like that in the man page.

However it is possible to set nodad on IPv4 addresses, too:

$ ip link add dummy0 type dummy
$ ip -4 addr add 192.168.1.1 dev dummy0 nodad
$ ip a
1: dummy0: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN group default qlen 1000
   link/ether 1a:6d:c6:96:ca:f8 brd ff:ff:ff:ff:ff:ff
   inet 192.168.1.1/32 scope global nodad dummy0
      valid_lft forever preferred_lft forever

Fix this adding a check on the protocol family before setting
IFA_F_NODAD flag.

Fixes: bac735c53a36d ("enabled to manipulate the flags of IFA_F_HOMEADDRESS or IFA_F_NODAD from ip.")
Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
---
 ip/ipaddress.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/ip/ipaddress.c b/ip/ipaddress.c
index 47e5be7462fe7..38356cc929e7b 100644
--- a/ip/ipaddress.c
+++ b/ip/ipaddress.c
@@ -2250,7 +2250,10 @@ static int ipaddr_modify(int cmd, int flags, int argc, char **argv)
 		} else if (strcmp(*argv, "home") == 0) {
 			ifa_flags |= IFA_F_HOMEADDRESS;
 		} else if (strcmp(*argv, "nodad") == 0) {
-			ifa_flags |= IFA_F_NODAD;
+			if (req.ifa.ifa_family == AF_INET6)
+				ifa_flags |= IFA_F_NODAD;
+			else
+				invarg("nodad option can be set only for IPv6 addresses\n", *argv);
 		} else if (strcmp(*argv, "mngtmpaddr") == 0) {
 			ifa_flags |= IFA_F_MANAGETEMPADDR;
 		} else if (strcmp(*argv, "noprefixroute") == 0) {
-- 
2.20.1