From 322e3f614f06c5f9627b0ae71e1507a32def3b47 Mon Sep 17 00:00:00 2001
From: Ivan Pepelnjak <ip@ipspace.net>
Date: Sun, 4 Dec 2022 17:57:53 +0100
Subject: [PATCH] Use new- or old-style formatting strings when creating
 interface names

---
 netsim/__init__.py           |  2 +-
 netsim/augment/links.py      | 15 +++++++++++++--
 netsim/topology-defaults.yml |  4 ++--
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/netsim/__init__.py b/netsim/__init__.py
index 6a79234ca..16f62de1a 100755
--- a/netsim/__init__.py
+++ b/netsim/__init__.py
@@ -1,3 +1,3 @@
 #!/usr/bin/env python3
 
-__version__ = "1.4.1-post2"
+__version__ = "1.4.2-dev1"
diff --git a/netsim/augment/links.py b/netsim/augment/links.py
index d93203bb9..529220f13 100644
--- a/netsim/augment/links.py
+++ b/netsim/augment/links.py
@@ -146,6 +146,17 @@ def get_link_propagate_attributes(defaults: Box) -> set:
   return set(defaults.attributes.link).union(set(defaults.attributes.link_internal)) - \
          set(defaults.attributes.link_no_propagate)
 
+"""
+Get interface name: create interface name given interface name format, ifindex and optional
+interface data structures. Use str.format if the name format includes '{}'
+"""
+def get_interface_name(fmt: str, ifdata: Box) -> str:
+  if '{' in fmt:
+    result = str(eval(f"f'{fmt}'",dict(ifdata)))                        # An awful hack to use f-string specified in a string variable
+    return result
+  else:
+    return fmt % ifdata.ifindex                                         # Old-style formatting
+
 """
 Add interface data structure to a node:
 
@@ -167,12 +178,12 @@ def add_node_interface(node: Box, ifdata: Box, defaults: Box) -> Box:
 
   ifdata.ifindex = ifindex
   if ifname_format and not 'ifname' in ifdata:
-    ifdata.ifname = ifname_format % ifindex
+    ifdata.ifname = get_interface_name(ifname_format,ifdata)
 
   pdata = devices.get_provider_data(node,defaults).get('interface',{})
   pdata = Box(pdata,box_dots=True,default_box=True)                     # Create a copy of the provider interface data
   if 'name' in pdata:
-    pdata.name = pdata.name % ifindex
+    pdata.name = get_interface_name(pdata.name,ifdata)
 
   if pdata:
     provider = devices.get_provider(node,defaults)
diff --git a/netsim/topology-defaults.yml b/netsim/topology-defaults.yml
index 05778991f..b367273f2 100644
--- a/netsim/topology-defaults.yml
+++ b/netsim/topology-defaults.yml
@@ -534,7 +534,7 @@ devices:
       create_iso: asav
   
   eos:
-    interface_name: Ethernet%d
+    interface_name: Ethernet{ifindex}
     description: Arista vEOS
     mgmt_if: Management1
     virtualbox:
@@ -583,7 +583,7 @@ devices:
         protocol: [ anycast, vrrp ]
     clab:
       interface:
-        name: et%d
+        name: et{ifindex}
       node:
         kind: ceos
         env: