isisd: Fix Attach-bit processing

The purpose of the Attach-bit is to accomplish inter-area routing.  In other
venders, the Attached-bit is automatically set when a router is configured
as a L1|L2 router and has two adjacencies.  When a L1 router receives a LSP
with the Attached-bit set it is supposed to create a default route pointing
toward the neighbor to provide a default path out of the L1 area.

ISIS implementation has been fixed to support the above definition:
Setting the Attach-bit is now the default behavior and we allow the user to
turn it off.

We will only set the Default Attach-bit when creating a L1 LSP, if we are
a L1|L2 router and have a L2 adjacency up.

When a L1 router receives a LSP with the Attach-bit set, we will create a
default route pointing to the L1|L2 router as the nexthop.

The default route will be removed if the LSP is received with the Attach-bit
cleared.

Signed-off-by: Lynne Morrison <lynne@voltanet.io>

1 files changed, 15 insertions, 0 deletions

diff --git a/yang/frr-isisd.yang b/yang/frr-isisd.yang
index 812dd4159..8757ab6b8 100644
--- a/yang/frr-isisd.yang
+++ b/yang/frr-isisd.yang
@@ -1043,9 +1043,24 @@ module frr-isisd {
           "Dynamic hostname support for IS-IS.";
       }
 
+      leaf attach-send {
+        type boolean;
+        default "true";
+        description
+          "If true, attached bits are sent in LSP if L1/L2 router for inter-area traffic.";
+      }
+
+      leaf attach-receive-ignore {
+        type boolean;
+        default "false";
+        description
+          "If false, attached bits received in LSP, cause default route add, if L1 router for inter-area traffic.";
+      }
+
       leaf attached {
         type boolean;
         default "false";
+	status deprecated;
         description
           "If true, identify as L1/L2 router for inter-area traffic.";
       }