zebra: Modify metric read to be admin distance and metric

For ZEBRA_ROUTE_KERNEL types:

The metric/priority of the route received from the kernel
is a 32 bit number.  We are going to interpret the high
order byte as the Admin Distance and the low order 3 bytes
as the metric.

This will allow us to do two things:
1) Allow the creation of kernel routes that can be
   overridden by zebra.
2) Allow the old behavior for 'most' kernel route types
   if a user enters 'ip route ...' v4 routes get a metric
   of 0 and v6 routes get a metric of 1024.  Both of these
   values will end up with a admin distance of 0, which
   will cause them to win for the purposes of zebra.

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>

diff --git a/zebra/rt_netlink.c b/zebra/rt_netlink.c
index 039fac4e67d5a9aace331eb5f47060e49502f007..a0ca93dfd370da534e4f5762baab0bf4f8eaf95a 100644 (file)
--- a/zebra/rt_netlink.c
+++ b/zebra/rt_netlink.c
@@ -277,6 +277,7 @@ static int netlink_route_change_read_unicast(struct sockaddr_nl *snl,
        int table;
        int metric = 0;
        u_int32_t mtu = 0;
+       uint8_t distance = 0;
 
        void *dest = NULL;
        void *gate = NULL;
@@ -405,16 +406,38 @@ static int netlink_route_change_read_unicast(struct sockaddr_nl *snl,
                return 0;
        }
 
+       /*
+        * For ZEBRA_ROUTE_KERNEL types:
+        *
+        * The metric/priority of the route received from the kernel
+        * is a 32 bit number.  We are going to interpret the high
+        * order byte as the Admin Distance and the low order 3 bytes
+        * as the metric.
+        *
+        * This will allow us to do two things:
+        * 1) Allow the creation of kernel routes that can be
+        *    overridden by zebra.
+        * 2) Allow the old behavior for 'most' kernel route types
+        *    if a user enters 'ip route ...' v4 routes get a metric
+        *    of 0 and v6 routes get a metric of 1024.  Both of these
+        *    values will end up with a admin distance of 0, which
+        *    will cause them to win for the purposes of zebra.
+        */
+       if (proto == ZEBRA_ROUTE_KERNEL) {
+               distance = (metric >> 24) & 0xFF;
+               metric   = (metric & 0x00FFFFFF);
+       }
+
        if (IS_ZEBRA_DEBUG_KERNEL) {
                char buf[PREFIX_STRLEN];
                char buf2[PREFIX_STRLEN];
                zlog_debug(
-                       "%s %s%s%s vrf %u", nl_msg_type_to_str(h->nlmsg_type),
+                       "%s %s%s%s vrf %u metric: %d Admin Distance: %d", nl_msg_type_to_str(h->nlmsg_type),
                        prefix2str(&p, buf, sizeof(buf)),
                        src_p.prefixlen ? " from " : "",
                        src_p.prefixlen ? prefix2str(&src_p, buf2, sizeof(buf2))
                                        : "",
-                       vrf_id);
+                       vrf_id, metric, distance);
        }
 
        afi_t afi = AFI_IP;
@@ -454,7 +477,7 @@ static int netlink_route_change_read_unicast(struct sockaddr_nl *snl,
                                memcpy(&nh.gate, gate, sz);
 
                        rib_add(afi, SAFI_UNICAST, vrf_id, proto,
-                               0, flags, &p, NULL, &nh, table, metric, mtu, 0);
+                               0, flags, &p, NULL, &nh, table, metric, mtu, distance);
                } else {
                        /* This is a multipath route */
 
@@ -466,7 +489,7 @@ static int netlink_route_change_read_unicast(struct sockaddr_nl *snl,
 
                        re = XCALLOC(MTYPE_RE, sizeof(struct route_entry));
                        re->type = proto;
-                       re->distance = 0;
+                       re->distance = distance;
                        re->flags = flags;
                        re->metric = metric;
                        re->mtu = mtu;