zebra: set connected route metric based on the devaddr metric

MACVLAN devices are typically used for applications such as VRR/VRRP that
require a second MAC address (virtual). These devices have a corresponding
SVI/VLAN device -
root@TORC11:~# ip addr show vlan1002
39: vlan1002@bridge: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9152 qdisc noqueue master vrf1 state UP group default
    link/ether 00:02:00:00:00:2e brd ff:ff:ff:ff:ff:ff
    inet6 2001:aa:1::2/64 scope global
       valid_lft forever preferred_lft forever
root@TORC11:~# ip addr show vlan1002-v0
40: vlan1002-v0@vlan1002: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9152 qdisc noqueue master vrf1 state UP group default
    link/ether 00:00:5e:00:01:01 brd ff:ff:ff:ff:ff:ff
    inet6 2001:aa:1::a/64 metric 1024 scope global
       valid_lft forever preferred_lft forever
root@TORC11:~#

The macvlan device is used primarily for RX (VR-IP/VR-MAC). And TX is via
the SVI. To acheive that functionality the macvlan network's metric
is set to a higher value.

Zebra currently ignores the devaddr metric sent by the kernel and hardcodes
it to 0. This commit eliminates that hardcoding. If the devaddr metric
is available (METRIC_MAX) it is used for setting up the connected route
otherwise we fallback to the dev/interface metric.

Setting the macvlan metric to a higher value ensures that zebra will always
select the connected route on the SVI (and subsequently use it for next hop
resolution etc.) -
root@TORC11:~# vtysh -c "show ip route vrf vrf1 2001:aa:1::/64"
Routing entry for 2001:aa:1::/64
  Known via "connected", distance 0, metric 1024, vrf vrf1
  Last update 11:30:56 ago
  * directly connected, vlan1002-v0

Routing entry for 2001:aa:1::/64
  Known via "connected", distance 0, metric 0, vrf vrf1, best
  Last update 11:30:56 ago
  * directly connected, vlan1002

root@TORC11:~#

Ticket: CM-23511
Signed-off-by: Anuradha Karuppiah <anuradhak@cumulusnetworks.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/lib/if.h b/lib/if.h
index 166bfa92b5..5b46ed8204 100644
--- a/lib/if.h
+++ b/lib/if.h
@@ -341,6 +341,8 @@ DECLARE_QOBJ_TYPE(interface)
 DECLARE_HOOK(if_add, (struct interface * ifp), (ifp))
 DECLARE_KOOH(if_del, (struct interface * ifp), (ifp))
 
+#define METRIC_MAX (~0)
+
 /* Connected address structure. */
 struct connected {
 	/* Attached interface. */
@@ -388,6 +390,13 @@ struct connected {
 
 	/* Label for Linux 2.2.X and upper. */
 	char *label;
+
+	/*
+	 * Used for setting the connected route's cost. If the metric
+	 * here is set to METRIC_MAX the connected route falls back to
+	 * "struct interface"
+	 */
+	uint32_t metric;
 };
 
 /* Nbr Connected address structure. */