ipv6: Don't send rs packets to the interface of ARPHRD_TUNNEL

ARPHRD_TUNNEL interface can't process rs packets
and will generate TX errors

ex:
ip tunnel add ethn mode ipip local 192.168.1.1 remote 192.168.1.2
ifconfig ethn x.x.x.x

ethn: flags=209<UP,POINTOPOINT,RUNNING,NOARP>  mtu 1480
	inet x.x.x.x  netmask 255.255.255.255  destination x.x.x.x
	inet6 fe80::5efe:ac1e:3cdb  prefixlen 64  scopeid 0x20<link>
	tunnel   txqueuelen 1000  (IPIP Tunnel)
	RX packets 0  bytes 0 (0.0 B)
	RX errors 0  dropped 0  overruns 0  frame 0
	TX packets 0  bytes 0 (0.0 B)
	TX errors 3  dropped 0 overruns 0  carrier 0  collisions 0

Signed-off-by: jianghaoran <jianghaoran@kylinos.cn>
Link: https://lore.kernel.org/r/20220429053802.246681-1-jianghaoran@kylinos.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv6/addrconf.c

@@ -4219,7 +4219,8 @@ static void addrconf_dad_completed(struct inet6_ifaddr *ifp, bool bump_id,
 	send_rs = send_mld &&
 		  ipv6_accept_ra(ifp->idev) &&
 		  ifp->idev->cnf.rtr_solicits != 0 &&
-		  (dev->flags&IFF_LOOPBACK) == 0;
+		  (dev->flags & IFF_LOOPBACK) == 0 &&
+		  (dev->type != ARPHRD_TUNNEL);
 	read_unlock_bh(&ifp->idev->lock);
 
 	/* While dad is in progress mld report's source address is in6_addrany.