dump tailscale derp rule-set

derp-dump.py

import json
import urllib.error
import urllib.request

url = "https://login.tailscale.com/derpmap/default"
try:
    with urllib.request.urlopen(url) as response:
        charset = response.headers.get_content_charset()
        if charset is None:
            charset = "utf-8"
        payload = response.read().decode(charset)
except urllib.error.URLError as e:
    print(f"URLError: {e}")
    raise e

data = json.loads(payload)

domains = []
seen_domains = set()
ipv4s = []
seen_ipv4s = set()
ipv6s = []
seen_ipv6s = set()

for region in data["Regions"].values():
    for node in region["Nodes"]:
        domain = node["HostName"]
        if domain not in seen_domains:
            domains.append(domain)
            seen_domains.add(domain)
        ipv4 = node["IPv4"]
        if ipv4 not in seen_ipv4s:
            ipv4s.append(ipv4)
            seen_ipv4s.add(ipv4)
        ipv6 = node["IPv6"]
        if ipv6 not in seen_ipv6s:
            ipv6s.append(ipv6)
            seen_ipv6s.add(ipv6)

with open("./derp.json", "w", buffering=1, encoding="utf-8") as derp_json:
    json.dump(data, derp_json, indent=2)

with open("./derp.list", "w", buffering=1, encoding="utf-8") as derp_file:
    derp_file.write("# Rule list of tailscale derpers\n")
    for domain in domains:
        derp_file.write(f"DOMAIN,{domain}\n")

    derp_file.write("# IPV4\n")
    for ipv4 in ipv4s:
        derp_file.write(f"IP-CIDR,{ipv4}/32,no-resolve\n")
        
    derp_file.write("# IPV6\n")
    for ipv6 in ipv6s:
        derp_file.write(f"IP-CIDR6,{ipv6}/128,no-resolve\n")