infix/test/case/dhcp/client_hostname_resend/test.py

#!/usr/bin/env python3
"""DHCP Hostname Resend

Verify that updating the system hostname restarts the DHCP client so
subsequent DHCP requests advertise the current hostname (option 12,
RFC 2132).

Regression test for a bug where the DHCP client callback only reacts
on diffs in infix-dhcp-client, so a standalone change of
ietf-system:system/hostname leaves the running udhcpc untouched with
the old '-x hostname:' argument from when it was first started.

"""

import infamy
from infamy.util import until


def udhcpc_cmdline(ssh, ifname):
    """Return the NUL-separated argv of the running udhcpc for ifname."""
    pidfile = f"/run/dhcp-client-{ifname}.pid"
    cmd = ssh.runsh(
        f"p=$(cat {pidfile} 2>/dev/null); "
        f"[ -n \"$p\" ] && tr '\\0' ' ' < /proc/$p/cmdline"
    )
    return cmd.stdout


def running_hostname(ssh, ifname):
    """Extract the hostname udhcpc is currently announcing (-x hostname:<name>)."""
    for tok in udhcpc_cmdline(ssh, ifname).split():
        if tok.startswith("hostname:"):
            return tok.split(":", 1)[1]
    return None


with infamy.Test() as test:
    HOSTNM_A = "infix-resend-a"
    HOSTNM_B = "infix-resend-b"

    with test.step("Set up topology and attach to target DUT"):
        env = infamy.Env()
        client = env.attach("client", "mgmt")
        clissh = env.attach("client", "mgmt", "ssh")
        _, port = env.ltop.xlate("client", "mgmt")

    with test.step(f"Configure initial hostname '{HOSTNM_A}'"):
        client.put_config_dicts({"ietf-system": {
            "system": {
                "hostname": HOSTNM_A
            }
        }})
        until(lambda: client.get_data("/ietf-system:system")
              .get("system", {}).get("hostname") == HOSTNM_A)

    with test.step("Enable DHCP client sending hostname option"):
        client.put_config_dicts({
            "ietf-system": {
                "system": {
                    "hostname": HOSTNM_A
                }
            },
            "ietf-interfaces": {
            "interfaces": {
                "interface": [{
                    "name": port,
                    "ipv4": {
                        "infix-dhcp-client:dhcp": {
                            "option": [
                                {"id": "vendor-class", "value": "infamy"},
                                {"id": "hostname", "value": "auto"},
                                {"id": "netmask"},
                                {"id": "router"}
                            ]
                        }
                    }
                }]
            }
        }})

    with test.step(f"Verify running udhcpc announces hostname '{HOSTNM_A}'"):
        until(lambda: running_hostname(clissh, port) == HOSTNM_A)

    with test.step(f"Update system hostname to '{HOSTNM_B}'"):
        client.put_config_dicts({"ietf-system": {
            "system": {
                "hostname": HOSTNM_B
            }
        }})
        until(lambda: client.get_data("/ietf-system:system")
              .get("system", {}).get("hostname") == HOSTNM_B)

    with test.step(f"Verify running udhcpc announces hostname '{HOSTNM_B}'"):
        try:
            until(lambda: running_hostname(clissh, port) == HOSTNM_B,
                  attempts=15)
        except Exception:
            cur = running_hostname(clissh, port)
            print(f"udhcpc still announcing hostname '{cur}', expected '{HOSTNM_B}'")
            test.fail()

    test.succeed()