arp: fix arp -s/-S

When setting a permanent ARP entry, the route(4) would use
rtm->rtm_rmx.rmx_expire == 0 as a flag for installing a static entry, but
netlink(4) is looking for explicit NTF_STICKY flag in the request.  The
arp(8) utility was adopted to use netlink(4) by default, but it has lots
of route-era guts internally. Specifically there is global variable 'opts'
that shares configuration for both protocols, and it is still initialized
with route(4) specific RTF_xxx flags.  In set_nl() these flags are
translated to netlink(4) parameters. However, RTF_STATIC is a flag that is
never set by default, so attempt to use it as a proxy flag manifesting
-s/-S results in losing it.  Use zero opts.expire_time as a manifest of
-s/-S operation.  This is a minimal fix.  A better one would be to fully
get rid of route(4) legacy.

The change also corrects the logic to set NUD_PERMANENT flag for
consistency.  This flag is ignored by our kernel (now).

Reviewed by:		melifaro, tuexen, emaste
PR:			277063
Fixes:			6ad73dbf65048b0950a1ba6ff25607f6708c8954
Differential Revision:	https://reviews.freebsd.org/D43983

1 files changed, 3 insertions, 5 deletions

diff --git a/usr.sbin/arp/arp_netlink.c b/usr.sbin/arp/arp_netlink.c
index d78f380af04b..8644f3722aed 100644
--- a/usr.sbin/arp/arp_netlink.c
+++ b/usr.sbin/arp/arp_netlink.c
@@ -390,9 +390,6 @@ set_nl(uint32_t ifindex, struct sockaddr_in *dst, struct sockaddr_dl *sdl, char
 		return (0);
 	}
 
-	if (opts.expire_time != 0)
-		opts.flags &= ~RTF_STATIC;
-
 	snl_init_writer(&ss, &nw);
 	struct nlmsghdr *hdr = snl_create_msg_request(&nw, RTM_NEWNEIGH);
 	hdr->nlmsg_flags |= NLM_F_CREATE | NLM_F_REPLACE;
@@ -402,11 +399,12 @@ set_nl(uint32_t ifindex, struct sockaddr_in *dst, struct sockaddr_dl *sdl, char
 
 		ndmsg->ndm_family = AF_INET;
 		ndmsg->ndm_ifindex = ifindex;
-		ndmsg->ndm_state = (opts.flags & RTF_STATIC) ? NUD_PERMANENT : NUD_NONE;
+		ndmsg->ndm_state = (opts.expire_time == 0) ? \
+		    NUD_PERMANENT : NUD_NONE;
 
 		if (opts.flags & RTF_ANNOUNCE)
 			nl_flags |= NTF_PROXY;
-		if (opts.flags & RTF_STATIC)
+		if (opts.expire_time == 0)
 			nl_flags |= NTF_STICKY;
 		ndmsg->ndm_flags = nl_flags;
 	}