zebra: Dissallow a /32 or /128 through itself

Do not allow an upper level protocol to send a route to
zebra that is a /32 or a /128 that recurses through itself.

Current behavior:
donna.cumulusnetworks.com# show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
       F - PBR, f - OpenFabric,
       > - selected route, * - FIB route, q - queued route, r - rejected route

K>* 0.0.0.0/0 [0/104] via 10.0.2.2, enp0s3, 01:05:28
C>* 10.0.2.0/24 is directly connected, enp0s3, 00:01:50
C>* 192.168.209.0/24 is directly connected, enp0s8, 01:05:28
C>* 192.168.210.0/24 is directly connected, enp0s9, 01:05:28
D>* 192.168.210.43/32 [150/0] via 192.168.210.44, enp0s9, 01:01:57
D   192.168.210.44/32 [150/0] via 192.168.210.44 inactive, 01:05:15
C>* 192.168.212.0/24 is directly connected, enp0s10, 01:05:28
donna.cumulusnetworks.com# sharp install routes 40.0.0.1 nexthop 192.168.210.44
% Command incomplete: sharp install routes 40.0.0.1 nexthop 192.168.210.44
donna.cumulusnetworks.com# sharp install routes 40.0.0.1 nexthop 192.168.210.44 1
donna.cumulusnetworks.com# end
donna.cumulusnetworks.com# show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
       F - PBR, f - OpenFabric,
       > - selected route, * - FIB route, q - queued route, r - rejected route

K>* 0.0.0.0/0 [0/104] via 10.0.2.2, enp0s3, 01:05:51
C>* 10.0.2.0/24 is directly connected, enp0s3, 00:00:12
D>* 40.0.0.1/32 [150/0] via 192.168.210.44, enp0s9, 00:00:03
C>* 192.168.209.0/24 is directly connected, enp0s8, 01:05:51
C>* 192.168.210.0/24 is directly connected, enp0s9, 01:05:51
D>* 192.168.210.43/32 [150/0] via 192.168.210.44, enp0s9, 01:02:20
D   192.168.210.44/32 [150/0] via 192.168.210.44 inactive, 01:05:38
C>* 192.168.212.0/24 is directly connected, enp0s10, 01:05:51
donna.cumulusnetworks.com#

Fixed behavior:

donna.cumulusnetworks.com# sharp install routes 192.168.210.44 nexthop 192.168.210.44 1
donna.cumulusnetworks.com# show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
       F - PBR, f - OpenFabric,
       > - selected route, * - FIB route, q - queued route, r - rejected route

K>* 0.0.0.0/0 [0/104] via 10.0.2.2, enp0s3, 00:00:15
C>* 10.0.2.0/24 is directly connected, enp0s3, 00:00:15
C>* 192.168.209.0/24 is directly connected, enp0s8, 00:00:15
C>* 192.168.210.0/24 is directly connected, enp0s9, 00:00:15
D   192.168.210.44/32 [150/0] via 192.168.210.44 inactive, 00:00:03
C>* 192.168.212.0/24 is directly connected, enp0s10, 00:00:15
donna.cumulusnetworks.com# sharp install routes 40.0.0.1 nexthop 192.168.210.44 1
donna.cumulusnetworks.com# show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
       F - PBR, f - OpenFabric,
       > - selected route, * - FIB route, q - queued route, r - rejected route

K>* 0.0.0.0/0 [0/104] via 10.0.2.2, enp0s3, 00:00:24
C>* 10.0.2.0/24 is directly connected, enp0s3, 00:00:24
D>* 40.0.0.1/32 [150/0] via 192.168.210.44, enp0s9, 00:00:02
C>* 192.168.209.0/24 is directly connected, enp0s8, 00:00:24
C>* 192.168.210.0/24 is directly connected, enp0s9, 00:00:24
D   192.168.210.44/32 [150/0] via 192.168.210.44 inactive, 00:00:12
C>* 192.168.212.0/24 is directly connected, enp0s10, 00:00:24
donna.cumulusnetworks.com#

This behavior came up from discussion around issue #5159.  Where
OSPF was receiving a route through itself as part of the router link
lsa.  I currently think that ospf should probably dissallow this in ospf
but we should also do the right thing in zebra.  If we do not allow this
change we can have situations where ordering of routes into zebra suddenly
matters.

Fixes: #5159
Signed-off-by: Donald Sharp <sharpd@cumulsunetworks.com>

diff --git a/zebra/zebra_nhg.c b/zebra/zebra_nhg.c
index 35df02a19ab469df002e6d66ad0d39625a03bbea..4484c831fe13ecfb3ba42e125eb70974e94a1b73 100644 (file)
--- a/zebra/zebra_nhg.c
+++ b/zebra/zebra_nhg.c
@@ -221,6 +221,17 @@ static int nexthop_active(afi_t afi, struct route_entry *re,
                }
        }
 
+       if ((top->p.family == AF_INET && top->p.prefixlen == 32
+            && nexthop->gate.ipv4.s_addr == top->p.u.prefix4.s_addr)
+           || (top->p.family == AF_INET6 && top->p.prefixlen == 128
+               && memcmp(&nexthop->gate.ipv6, &top->p.u.prefix6, 16) == 0)) {
+               if (IS_ZEBRA_DEBUG_RIB_DETAILED)
+                       zlog_debug(
+                               "\t:%s: Attempting to install a max prefixlength route through itself",
+                               __PRETTY_FUNCTION__);
+               return 0;
+       }
+
        /* Make lookup prefix. */
        memset(&p, 0, sizeof(struct prefix));
        switch (afi) {