statd: add support for ip forwarding operational state

This patch unlocks "routing interfaces" support in the ietf-routing yang
model.  An array of interface with IP forwarding enabled.

Note, because of #515 we skip IPv6 forwarding for now.  This will in the
near future be handled by a per-interface force_forwarding sysctl flag.

The 'show interface [ifname]' admin-exec command has been extended with
a Flags field for a quick overview of which interfaces have forwarding
currently enabled.

Fixes #647

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/statd/python/cli_pretty/cli_pretty.py

@@ -98,6 +98,7 @@ def compress_interface_list(interfaces):
 
 
 class Pad:
+    flags = 2
     iface = 16
     proto = 11
     state = 12
@@ -803,6 +804,9 @@ class DhcpServer:
 
 
 class Iface:
+    # Class variable to hold routing-enabled interfaces for the current display session
+    _routing_ifaces = set()
+
     def __init__(self, data):
         self.data = data
         self.name = data.get('name', '')
@@ -915,13 +919,16 @@ class Iface:
         return self.oper_status
 
     def pr_name(self, pipe=""):
+        flag = "⇅" if self.name in Iface._routing_ifaces else " "
+        print(f"{flag:<{Pad.flags}}", end="")
         print(f"{pipe}{self.name:<{Pad.iface - len(pipe)}}", end="")
 
     def pr_proto_ipv4(self, pipe=''):
         for addr in self.ipv4_addr:
             origin = f"({addr['origin']})" if addr.get('origin') else ""
 
-            row =  f"{pipe:<{Pad.iface}}"
+            row =  f"{'':<{Pad.flags}}"
+            row += f"{pipe:<{Pad.iface}}"
             row += f"{'ipv4':<{Pad.proto}}"
             row += f"{'':<{Pad.state}}{addr['ip']}/{addr['prefix-length']} {origin}"
             print(row)
@@ -930,7 +937,8 @@ class Iface:
         for addr in self.ipv6_addr:
             origin = f"({addr['origin']})" if addr.get('origin') else ""
 
-            row =  f"{pipe:<{Pad.iface}}"
+            row =  f"{'':<{Pad.flags}}"
+            row += f"{pipe:<{Pad.iface}}"
             row += f"{'ipv6':<{Pad.proto}}"
             row += f"{'':<{Pad.state}}{addr['ip']}/{addr['prefix-length']} {origin}"
             print(row)
@@ -938,7 +946,8 @@ class Iface:
     def _pr_proto_common(self, name, phys_address, pipe=''):
         row = ""
         if len(pipe) > 0:
-            row =  f"{pipe:<{Pad.iface}}"
+            row =  f"{'':<{Pad.flags}}"
+            row += f"{pipe:<{Pad.iface}}"
 
         row += f"{name:<{Pad.proto}}"
         dec = Decore.green if self.oper() == "up" else Decore.red
@@ -1184,6 +1193,11 @@ class Iface:
         parent.pr_proto_eth()
 
     def pr_container(self):
+        # Add ⇅ flag for interfaces with IP forwarding enabled
+        flag = "⇅" if self.name in Iface._routing_ifaces else " "
+        # Flag column is outside the gray background
+        print(f"{flag:<{Pad.flags}}", end="")
+
         row = f"{self.name:<{Pad.iface}}"
         row += f"{'container':<{Pad.proto}}"
         row += f"{'':<{Pad.state}}"
@@ -1204,6 +1218,9 @@ class Iface:
         if self.oper():
             print(f"{'operational status':<{20}}: {self.oper(detail=True)}")
 
+        forwarding = "enabled" if self.name in Iface._routing_ifaces else "disabled"
+        print(f"{'ip forwarding':<{20}}: {forwarding}")
+
         if self.lower_if:
             print(f"{'lower-layer-if':<{20}}: {self.lower_if}")
 
@@ -1407,13 +1424,21 @@ def print_interface(iface):
 
 
 def pr_interface_list(json):
-    hdr = (f"{'INTERFACE':<{Pad.iface}}"
+    hdr = (f"{'⚑':<{Pad.flags}}"
+           f"{'INTERFACE':<{Pad.iface}}"
            f"{'PROTOCOL':<{Pad.proto}}"
            f"{'STATE':<{Pad.state}}"
            f"{'DATA':<{Pad.data}}")
 
     print(Decore.invert(hdr))
 
+    # Set class variable with routing-enabled interfaces (with IP forwarding)
+    if "ietf-routing:routing" in json:
+        routing_data = json["ietf-routing:routing"].get("interfaces", {})
+        Iface._routing_ifaces = set(routing_data.get("interface", []))
+    else:
+        Iface._routing_ifaces = set()
+
     ifaces = sorted(json["ietf-interfaces:interfaces"]["interface"],
                     key=ifname_sort)
     iface = find_iface(ifaces, "lo")
@@ -1472,6 +1497,13 @@ def pr_interface_list(json):
 
 
 def show_interfaces(json, name):
+    # Set class variable with routing-enabled interfaces (with IP forwarding)
+    if "ietf-routing:routing" in json:
+        routing_data = json["ietf-routing:routing"].get("interfaces", {})
+        Iface._routing_ifaces = set(routing_data.get("interface", []))
+    else:
+        Iface._routing_ifaces = set()
+
     if name:
         if not json.get("ietf-interfaces:interfaces"):
             print(f"No interface data found for \"{name}\"")

src/statd/python/yanger/ietf_routing.py

@@ -124,9 +124,37 @@ def add_protocol(routes, proto):
     insert(routes, 'routes', out)
 
 
+def get_routing_interfaces():
+    """Get list of interfaces with IPv4 forwarding enabled"""
+    import json
+
+    # Get all interfaces
+    links_json = HOST.run(tuple(['ip', '-j', 'link', 'show']), default="[]")
+    links = json.loads(links_json)
+
+    routing_ifaces = []
+    for link in links:
+        ifname = link.get('ifname')
+        if not ifname:
+            continue
+
+        # Check if IPv4 forwarding is enabled
+        # Note: We only check IPv4 forwarding. IPv6 forwarding behaves differently
+        # and will be handled separately when Linux 6.17+ force_forwarding is available.
+        ipv4_fwd = HOST.run(tuple(['sysctl', '-n', f'net.ipv4.conf.{ifname}.forwarding']), default="0").strip()
+
+        if ipv4_fwd == "1":
+            routing_ifaces.append(ifname)
+
+    return routing_ifaces
+
+
 def operational():
     out = {
         "ietf-routing:routing": {
+            "interfaces": {
+                "interface": get_routing_interfaces()
+            },
             "ribs":  {
                 "rib": [{
                     "name": "ipv4",