Conditionally compile in the af_inet and af_inet6, af_nd6 modules.

If compiled in for dual-stack use, test with feature_present(3)
to see if we should register the IPv4/IPv6 address family related
options.

In case there is no "inet" support we would love to go with the
usage() and make the address family mandatory (as it is for anything
but inet in theory).  Unfortunately people are used to
  ifconfig IF up/down
etc. as well, so use a fallback of "link".  Adjust the man page
to reflect these minor details.

Improve error handling printing a warning in addition to the usage
telling that we do not know the given address family in two places.

Reviewed by:	hrs, rwatson
Sponsored by:	The FreeBSD Foundation
Sponsored by:	iXsystems
MFC after:	2 weeks

1 files changed, 2 insertions, 0 deletions

diff --git a/sbin/ifconfig/af_inet.c b/sbin/ifconfig/af_inet.c
index 2e27114..6b4d735 100644
--- a/sbin/ifconfig/af_inet.c
+++ b/sbin/ifconfig/af_inet.c
@@ -200,5 +200,7 @@ static struct afswtch af_inet = {
 static __constructor void
 inet_ctor(void)
 {
+	if (!feature_present("inet"))
+		return;
 	af_register(&af_inet);
 }