diff options
| -rwxr-xr-x | frr-evpn-route-watcher/task.py | 113 |
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 |