isisd: add support for Anycast-SIDs

Add the "n-flag-clear" option to the "segment-routing prefix"
command. The only thing that option does is to clear the node
flag of the Prefix-SID, even if it corresponds to a local loopback
address. No changes are necessary other than that in order to fully
support Anycast-SIDs.  isisd already supports multiple routers
advertising the same route with the same Prefix-SID after the recent
refactoring. Clearing the node flag for such anycast routes isn't
strictly required, but failure to do so can lead to problems like
TI-LFA picking the wrong Prefix-SID when calculating repair paths.

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/yang/frr-isisd.yang b/yang/frr-isisd.yang
index 06d1a793b..c3b39e375 100644
--- a/yang/frr-isisd.yang
+++ b/yang/frr-isisd.yang
@@ -1381,6 +1381,12 @@ module frr-isisd {
               description
                 "Configure last hop behavior.";
             }
+            leaf n-flag-clear {
+              type boolean;
+              default "false";
+              description
+                "Not a node SID";
+            }
           }
         }
       }