#!/usr/bin/env python3
"""
lab_peer.py - the "other end of the cable" for the namespace lab.

Runs on one end of a veth pair inside a private network namespace and
plays a switch and/or a DHCP server with raw AF_PACKET sockets:

  --dhcp IP          answer every DHCPDISCOVER with a DHCPOFFER from IP
  --server-id IP     option 54 to put in the offer (default = --dhcp IP)
  --domain NAME      option 15 in the offer
  --lldp SYSNAME     send an LLDP frame every second
  --eapol            send an EAPOL Request/Identity every second
  --mac MAC          source MAC for the frames (default: the iface's MAC)

Never run this outside the lab netns: it is a rogue DHCP server.
"""

import argparse
import os
import select
import socket
import sys
import time

sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
import frames as F  # noqa: E402


def main():
    ap = argparse.ArgumentParser()
    ap.add_argument("--iface", required=True)
    ap.add_argument("--dhcp")
    ap.add_argument("--server-id")
    ap.add_argument("--domain")
    ap.add_argument("--lldp")
    ap.add_argument("--eapol", action="store_true")
    ap.add_argument("--mac")
    ap.add_argument("--duration", type=float, default=120)
    args = ap.parse_args()

    if os.environ.get("PXE_NIC_LAB") != "1":
        sys.exit("lab_peer.py: refusing to run outside the lab (PXE_NIC_LAB)")

    with open("/sys/class/net/%s/address" % args.iface) as f:
        mac = args.mac or f.read().strip()
    s = socket.socket(socket.AF_PACKET, socket.SOCK_RAW, socket.htons(3))
    s.bind((args.iface, 0))
    end = time.monotonic() + args.duration
    next_beacon = 0.0
    answered = set()
    sys.stdout.write("ready\n")
    sys.stdout.flush()
    while time.monotonic() < end:
        now = time.monotonic()
        if now >= next_beacon:
            if args.lldp:
                s.send(F.lldp(mac, system=args.lldp, port="Gi1/0/14",
                              vlan=309))
            if args.eapol:
                s.send(F.eapol(mac))
            next_beacon = now + 1.0
        r, _, _ = select.select([s], [], [], 0.2)
        if not r:
            continue
        frame, addr = s.recvfrom(65535)
        if addr[2] == 4 or not args.dhcp:     # our own outgoing frames
            continue
        d = F.parse_discover(frame)
        if not d or d[0] in answered:
            continue
        answered.add(d[0])
        xid, chaddr = d
        s.send(F.dhcp_reply(mac, args.dhcp, xid, chaddr,
                            yiaddr="10.99.0.50", domain=args.domain,
                            server_id=args.server_id))
        sys.stdout.write("offered xid %08x to %s\n" % (xid, chaddr))
        sys.stdout.flush()


if __name__ == "__main__":
    main()