1 files changed, 113 insertions, 0 deletions
diff --git a/frr-evpn-route-watcher/task.py b/frr-evpn-route-watcher/task.py
new file mode 100755
index 0000000..dfd981e
--- /dev/null
+++ b/frr-evpn-route-watcher/task.py
@@ -0,0 +1,113 @@
+import json
+import ipaddress
+import subprocess
+import re
+import time
+
+def get_frr_vrfs():
+    """Gets the list of vrf VNIs configured in FRR"""
+    process = subprocess.run(["vtysh", "-c", "show vrf vni json"], capture_output=True)
+    return json.loads(process.stdout)["vrfs"]
+
+def get_frr_evpn_info():
+    """Lists all the routes learned via evpn"""
+    process = subprocess.run(
+        ["vtysh", "-c", "show ip bgp l2vpn evpn json"], capture_output=True
+    )
+    return json.loads(process.stdout)
+
+def add_route_vrf(ip, vrf):
+    """Add a route using the ip route command"""
+    subprocess.run(
+        ["ip", "route", "add", str(ip), "dev", vrf, "metric", "0"],
+    )
+
+def remove_route_vrf(ip):
+    subprocess.run(["ip", "route", "del", str(ip)])
+
+def currently_routed(vrfs_names):
+    process = subprocess.run(["ip", "route"], capture_output=True, text=True)
+    routed_ips = []
+    for route in process.stdout.splitlines():
+        parts = route.split(" ")
+        if len(parts) == 6:
+            addr, dev, vrf, scope, link = (
+                parts[0],
+                parts[1],
+                parts[2],
+                parts[3],
+                parts[4],
+            )
+            addr = parse_ip(addr)
+            if (
+                addr != None
+                and dev == "dev"
+                and vrf in vrfs_names
+                and scope == "scope"
+                and link == "link"
+            ):
+                routed_ips.append(addr)
+    return routed_ips
+
+def parse_ip(str):
+    try:
+        return ipaddress.ip_network(str)
+    except ValueError:
+        return False
+
+def get_vrfs():
+    return {str(vrf["vni"]): vrf["vrf"] for vrf in get_frr_vrfs()}
+
+def resolve_routes():
+    json = get_frr_evpn_info()
+    vrfs = get_vrfs()
+
+    # The local router-id to search for IPs in the evpn routes information
+    localRouterId = json["bgpLocalRouterId"]
+    localAS = json["localAS"]
+
+    currentlyRouted = currently_routed([vrfs[vrf] for vrf in vrfs])
+
+    for jsonKey in json:
+        rd = jsonKey.split(":")
+        if len(rd) == 2:
+            peer, _ = rd
+
+            if parse_ip(peer) and peer == localRouterId:
+                rdObject = json[jsonKey]
+                for route in rdObject:
+                    matches = re.findall(r"(?:\[([^\]]*)\]:?)", route)
+                    if len(matches) == 6:
+                        route_type = matches[0]
+                        if route_type == "2":
+                            ip = parse_ip(matches[5])
+
+                            if ip != None and not ip.is_link_local:
+                                extendedCommunities = rdObject[route]["paths"][0][
+                                    "extendedCommunity"
+                                ]["string"]
+                                rts = re.finditer(
+                                    f"RT:{localAS}:(\d+)", extendedCommunities
+                                )
+
+                                # For all the matches we have in the extentendCommunity value
+                                for rt in rts:
+                                    vni = rt.group(1)
+                                    if vni in vrfs:
+                                        vrf = vrfs[vni]
+                                        if ip in currentlyRouted:
+                                            currentlyRouted.remove(ip)
+                                            break
+                                        
+                                        print(
+                                            f"wanting to add route {ip} to {vrf} ({vni}) vrf"
+                                        )
+                                        add_route_vrf(ip, vrf)
+                                        
+
+                                        break
+    for remove in currentlyRouted:
+        print(f"removing route for {remove}")
+        remove_route_vrf(remove)
+
+resolve_routes()
+\ No newline at end of file