confd: add support for static ARP and neighbor cache

Add support for static ARP (IPv4) and neighbor cache (IPv6) entries per
interface.  Static entries are installed as permanent kernel neighbor
table entries that are never evicted by normal ARP/NDP aging.

Fixes #819

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

src/statd/python/yanger/ietf_interfaces/common.py

@@ -28,3 +28,17 @@ def ipaddrs(ifname=None, netns=None):
         return HOST.run_json(pre + ["ip", "-j", "addr", "show"] + filt)
 
     return { addr["ifname"]: addr for addr in _ipaddrs(ifname, netns) }
+
+
+@cache
+def ipneighs(ifname=None, netns=None):
+    def _ipneighs(ifname, netns):
+        pre = ["ip", "netns", "exec", netns] if netns else []
+        filt = ["dev", ifname] if ifname else []
+        return HOST.run_json(pre + ["ip", "-j", "neigh", "show"] + filt, [])
+
+    result = {}
+    for e in _ipneighs(ifname, netns):
+        if dev := e.get("dev"):
+            result.setdefault(dev, []).append(e)
+    return result

src/statd/python/yanger/ietf_interfaces/ip.py

@@ -1,4 +1,55 @@
+import ipaddress
+
 from ..host import HOST
+from . import common
+
+
+def neigh_state(states):
+    xlate = {
+        "REACHABLE":  "reachable",
+        "STALE":      "stale",
+        "DELAY":      "delay",
+        "PROBE":      "probe",
+        "INCOMPLETE": "incomplete",
+    }
+    return next((xlate[s] for s in states if s in xlate), None)
+
+
+def neighbors(ifname, family):
+    result = []
+    for entry in common.ipneighs().get(ifname, []):
+        dst = entry.get("dst", "")
+        try:
+            version = ipaddress.ip_address(dst).version
+        except ValueError:
+            continue
+
+        if version != (4 if family == "inet" else 6):
+            continue
+
+        lladdr = entry.get("lladdr")
+        states = entry.get("state", [])
+
+        if not lladdr:
+            continue
+
+        origin = "static" if "PERMANENT" in states else "dynamic"
+        neigh = {
+            "ip":                 dst,
+            "link-layer-address": lladdr,
+            "origin":             origin,
+        }
+
+        if family == "inet6":
+            if state := neigh_state(states):
+                neigh["state"] = state
+            if entry.get("router"):
+                neigh["is-router"] = [None]
+
+        result.append(neigh)
+
+    return result
+
 
 def inet2yang_origin(inet):
     """Translate kernel IP address origin to YANG"""
@@ -34,23 +85,31 @@ def addresses(ipaddr, proto):
 
 def ipv4(ipaddr):
     ipv4 = {}
+    ifname = ipaddr.get("ifname")
 
     mtu = ipaddr.get("mtu")
-    if mtu and ipaddr.get("ifname") != "lo":
+    if mtu and ifname != "lo":
         ipv4["mtu"] = mtu
 
     if addrs := addresses(ipaddr, "inet"):
         ipv4["address"] = addrs
 
+    if neighs := neighbors(ifname, "inet"):
+        ipv4["neighbor"] = neighs
+
     return ipv4
 
 def ipv6(ipaddr):
     ipv6 = {}
+    ifname = ipaddr.get("ifname")
 
-    if mtu := HOST.read(f"/proc/sys/net/ipv6/conf/{ipaddr['ifname']}/mtu"):
+    if mtu := HOST.read(f"/proc/sys/net/ipv6/conf/{ifname}/mtu"):
         ipv6["mtu"] = int(mtu.strip())
 
     if addrs := addresses(ipaddr, "inet6"):
         ipv6["address"] = addrs
 
+    if neighs := neighbors(ifname, "inet6"):
+        ipv6["neighbor"] = neighs
+
     return ipv6