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✏️ Editing: dhcp.py

# Copyright (C) 2017 Canonical Ltd.
#
# Author: Chad Smith <chad.smith@canonical.com>
#
# This file is part of cloud-init. See LICENSE file for license information.

import abc
import contextlib
import glob
import logging
import os
import re
import signal
import time
from io import StringIO
from typing import Any, Dict, List

import configobj

from cloudinit import subp, temp_utils, util
from cloudinit.net import (
    find_fallback_nic,
    get_devicelist,
    get_ib_interface_hwaddr,
    get_interface_mac,
    is_ib_interface,
)

LOG = logging.getLogger(__name__)

NETWORKD_LEASES_DIR = "/run/systemd/netif/leases"
UDHCPC_SCRIPT = """#!/bin/sh
log() {
    echo "udhcpc[$PPID]" "$interface: $2"
}
[ -z "$1" ] && echo "Error: should be called from udhcpc" && exit 1
case $1 in
    bound|renew)
    cat <<JSON > "$LEASE_FILE"
{
    "interface": "$interface",
    "fixed-address": "$ip",
    "subnet-mask": "$subnet",
    "routers": "${router%% *}",
    "static_routes" : "${staticroutes}"
}
JSON
    ;;
    deconfig)
    log err "Not supported"
    exit 1
    ;;
    leasefail | nak)
    log err "configuration failed: $1: $message"
    exit 1
    ;;
    *)
    echo "$0: Unknown udhcpc command: $1" >&2
    exit 1
    ;;
esac
"""

class NoDHCPLeaseError(Exception):
    """Raised when unable to get a DHCP lease."""

class InvalidDHCPLeaseFileError(NoDHCPLeaseError):
    """Raised when parsing an empty or invalid dhclient.lease file.

Current uses are DataSourceAzure and DataSourceEc2 during ephemeral
    boot to scrape metadata.
    """

class NoDHCPLeaseInterfaceError(NoDHCPLeaseError):
    """Raised when unable to find a viable interface for DHCP."""

class NoDHCPLeaseMissingDhclientError(NoDHCPLeaseError):
    """Raised when unable to find dhclient."""

class NoDHCPLeaseMissingUdhcpcError(NoDHCPLeaseError):
    """Raised when unable to find udhcpc client."""

def select_dhcp_client(distro):
    """distros set priority list, select based on this order which to use

If the priority dhcp client isn't found, fall back to lower in list.
    """
    for client in distro.dhcp_client_priority:
        try:
            dhcp_client = client()
            LOG.debug("DHCP client selected: %s", client.client_name)
            return dhcp_client
        except (
            NoDHCPLeaseMissingDhclientError,
            NoDHCPLeaseMissingUdhcpcError,
        ):
            LOG.warning("DHCP client not found: %s", client.client_name)
    raise NoDHCPLeaseMissingDhclientError()

def maybe_perform_dhcp_discovery(distro, nic=None, dhcp_log_func=None):
    """Perform dhcp discovery if nic valid and dhclient command exists.

If the nic is invalid or undiscoverable or dhclient command is not found,
    skip dhcp_discovery and return an empty dict.

@param nic: Name of the network interface we want to run dhclient on.
    @param dhcp_log_func: A callable accepting the dhclient output and error
        streams.
    @return: A list of dicts representing dhcp options for each lease obtained
        from the dhclient discovery if run, otherwise an empty list is
        returned.
    """
    if nic is None:
        nic = find_fallback_nic()
        if nic is None:
            LOG.debug("Skip dhcp_discovery: Unable to find fallback nic.")
            raise NoDHCPLeaseInterfaceError()
    elif nic not in get_devicelist():
        LOG.debug(
            "Skip dhcp_discovery: nic %s not found in get_devicelist.", nic
        )
        raise NoDHCPLeaseInterfaceError()
    client = select_dhcp_client(distro)
    return client.dhcp_discovery(nic, dhcp_log_func, distro)

def networkd_parse_lease(content):
    """Parse a systemd lease file content as in /run/systemd/netif/leases/

Parse this (almost) ini style file even though it says:
      # This is private data. Do not parse.

Simply return a dictionary of key/values."""

return dict(configobj.ConfigObj(StringIO(content), list_values=False))

def networkd_load_leases(leases_d=None):
    """Return a dictionary of dictionaries representing each lease
    found in lease_d.i

The top level key will be the filename, which is typically the ifindex."""

if leases_d is None:
        leases_d = NETWORKD_LEASES_DIR

ret = {}
    if not os.path.isdir(leases_d):
        return ret
    for lfile in os.listdir(leases_d):
        ret[lfile] = networkd_parse_lease(
            util.load_file(os.path.join(leases_d, lfile))
        )
    return ret

def networkd_get_option_from_leases(keyname, leases_d=None):
    if leases_d is None:
        leases_d = NETWORKD_LEASES_DIR
    leases = networkd_load_leases(leases_d=leases_d)
    for _ifindex, data in sorted(leases.items()):
        if data.get(keyname):
            return data[keyname]
    return None

class DhcpClient(abc.ABC):
    client_name = ""

@classmethod
    def kill_dhcp_client(cls):
        subp.subp(["pkill", cls.client_name], rcs=[0, 1])

@classmethod
    def clear_leases(cls):
        cls.kill_dhcp_client()
        files = glob.glob("/var/lib/dhcp/*")
        for file in files:
            os.remove(file)

@classmethod
    def start_service(cls, dhcp_interface: str, distro):
        distro.manage_service(
            "start", cls.client_name, dhcp_interface, rcs=[0, 1]
        )

@classmethod
    def stop_service(cls, dhcp_interface: str, distro):
        distro.manage_service("stop", cls.client_name, rcs=[0, 1])

class IscDhclient(DhcpClient):
    client_name = "dhclient"

def __init__(self):
        self.dhclient_path = subp.which("dhclient")
        if not self.dhclient_path:
            LOG.debug(
                "Skip dhclient configuration: No dhclient command found."
            )
            raise NoDHCPLeaseMissingDhclientError()

@staticmethod
    def parse_dhcp_lease_file(lease_file: str) -> List[Dict[str, Any]]:
        """Parse the given dhcp lease file returning all leases as dicts.

Return a list of dicts of dhcp options. Each dict contains key value
        pairs a specific lease in order from oldest to newest.

@raises: InvalidDHCPLeaseFileError on empty of unparseable leasefile
            content.
        """
        lease_regex = re.compile(r"lease {(?P<lease>.*?)}\n", re.DOTALL)
        dhcp_leases = []
        lease_content = util.load_file(lease_file)
        if len(lease_content) == 0:
            raise InvalidDHCPLeaseFileError(
                "Cannot parse empty dhcp lease file {0}".format(lease_file)
            )
        for lease in lease_regex.findall(lease_content):
            lease_options = []
            for line in lease.split(";"):
                # Strip newlines, double-quotes and option prefix
                line = line.strip().replace('"', "").replace("option ", "")
                if not line:
                    continue
                lease_options.append(line.split(" ", 1))
            dhcp_leases.append(dict(lease_options))
        if not dhcp_leases:
            raise InvalidDHCPLeaseFileError(
                "Cannot parse dhcp lease file {0}. No leases found".format(
                    lease_file
                )
            )
        return dhcp_leases

def dhcp_discovery(
        self,
        interface,
        dhcp_log_func=None,
        distro=None,
    ):
        """Run dhclient on the interface without scripts/filesystem artifacts.

@param dhclient_cmd_path: Full path to the dhclient used.
        @param interface: Name of the network interface on which to dhclient.
        @param dhcp_log_func: A callable accepting the dhclient output and
            error streams.

@return: A list of dicts of representing the dhcp leases parsed from
            the dhclient.lease file or empty list.
        """
        LOG.debug("Performing a dhcp discovery on %s", interface)

# We want to avoid running /sbin/dhclient-script because of
        # side-effects in # /etc/resolv.conf any any other vendor specific
        # scripts in /etc/dhcp/dhclient*hooks.d.
        pid_file = "/run/dhclient.pid"
        lease_file = "/run/dhclient.lease"
        config_file = None

# this function waits for these files to exist, clean previous runs
        # to avoid false positive in wait_for_files
        with contextlib.suppress(FileNotFoundError):
            os.remove(pid_file)
            os.remove(lease_file)

# ISC dhclient needs the interface up to send initial discovery packets
        # Generally dhclient relies on dhclient-script PREINIT action to bring
        # the link up before attempting discovery. Since we are using
        # -sf /bin/true, we need to do that "link up" ourselves first.
        distro.net_ops.link_up(interface)
        # For INFINIBAND port the dhlient must be sent with
        # dhcp-client-identifier. So here we are checking if the interface is
        # INFINIBAND or not. If yes, we are generating the the client-id to be
        # used with the dhclient
        if is_ib_interface(interface):
            dhcp_client_identifier = (
                "20:%s" % get_interface_mac(interface)[36:]
            )
            interface_dhclient_content = (
                'interface "%s" '
                "{send dhcp-client-identifier %s;}"
                % (interface, dhcp_client_identifier)
            )
            tmp_dir = temp_utils.get_tmp_ancestor(needs_exe=True)
            config_file = os.path.join(tmp_dir, interface + "-dhclient.conf")
            util.write_file(config_file, interface_dhclient_content)

try:
            out, err = subp.subp(
                distro.build_dhclient_cmd(
                    self.dhclient_path,
                    lease_file,
                    pid_file,
                    interface,
                    config_file,
                )
            )
        except subp.ProcessExecutionError as error:
            LOG.debug(
                "dhclient exited with code: %s stderr: %r stdout: %r",
                error.exit_code,
                error.stderr,
                error.stdout,
            )
            raise NoDHCPLeaseError from error

# Wait for pid file and lease file to appear, and for the process
        # named by the pid file to daemonize (have pid 1 as its parent). If we
        # try to read the lease file before daemonization happens, we might try
        # to read it before the dhclient has actually written it. We also have
        # to wait until the dhclient has become a daemon so we can be sure to
        # kill the correct process, thus freeing cleandir to be deleted back
        # up the callstack.
        missing = util.wait_for_files(
            [pid_file, lease_file], maxwait=5, naplen=0.01
        )
        if missing:
            LOG.warning(
                "dhclient did not produce expected files: %s",
                ", ".join(os.path.basename(f) for f in missing),
            )
            return []

ppid = "unknown"
        daemonized = False
        for _ in range(0, 1000):
            pid_content = util.load_file(pid_file).strip()
            try:
                pid = int(pid_content)
            except ValueError:
                pass
            else:
                ppid = util.get_proc_ppid(pid)
                if ppid == 1:
                    LOG.debug("killing dhclient with pid=%s", pid)
                    os.kill(pid, signal.SIGKILL)
                    daemonized = True
                    break
            time.sleep(0.01)

if not daemonized:
            LOG.error(
                "dhclient(pid=%s, parentpid=%s) failed to daemonize after %s "
                "seconds",
                pid_content,
                ppid,
                0.01 * 1000,
            )
        if dhcp_log_func is not None:
            dhcp_log_func(out, err)
        return self.parse_dhcp_lease_file(lease_file)

@staticmethod
    def parse_static_routes(rfc3442):
        """
        parse rfc3442 format and return a list containing tuple of strings.

The tuple is composed of the network_address (including net length) and
        gateway for a parsed static route.  It can parse two formats of
        rfc3442, one from dhcpcd and one from dhclient (isc).

@param rfc3442: string in rfc3442 format (isc or dhcpd)
        @returns: list of tuple(str, str) for all valid parsed routes until the
                  first parsing error.

e.g.:

sr=parse_static_routes(\
        "32,169,254,169,254,130,56,248,255,0,130,56,240,1")
        sr=[
            ("169.254.169.254/32", "130.56.248.255"), \
        ("0.0.0.0/0", "130.56.240.1")
        ]

sr2 = parse_static_routes(\
        "24.191.168.128 192.168.128.1,0 192.168.128.1")
        sr2 = [
            ("191.168.128.0/24", "192.168.128.1"),\
        ("0.0.0.0/0", "192.168.128.1")
        ]

Python version of isc-dhclient's hooks:
           /etc/dhcp/dhclient-exit-hooks.d/rfc3442-classless-routes
        """
        # raw strings from dhcp lease may end in semi-colon
        rfc3442 = rfc3442.rstrip(";")
        tokens = [tok for tok in re.split(r"[, .]", rfc3442) if tok]
        static_routes = []

def _trunc_error(cidr, required, remain):
            msg = (
                "RFC3442 string malformed.  Current route has CIDR of %s "
                "and requires %s significant octets, but only %s remain. "
                "Verify DHCP rfc3442-classless-static-routes value: %s"
                % (cidr, required, remain, rfc3442)
            )
            LOG.error(msg)

current_idx = 0
        for idx, tok in enumerate(tokens):
            if idx < current_idx:
                continue
            net_length = int(tok)
            if net_length in range(25, 33):
                req_toks = 9
                if len(tokens[idx:]) < req_toks:
                    _trunc_error(net_length, req_toks, len(tokens[idx:]))
                    return static_routes
                net_address = ".".join(tokens[idx + 1 : idx + 5])
                gateway = ".".join(tokens[idx + 5 : idx + req_toks])
                current_idx = idx + req_toks
            elif net_length in range(17, 25):
                req_toks = 8
                if len(tokens[idx:]) < req_toks:
                    _trunc_error(net_length, req_toks, len(tokens[idx:]))
                    return static_routes
                net_address = ".".join(tokens[idx + 1 : idx + 4] + ["0"])
                gateway = ".".join(tokens[idx + 4 : idx + req_toks])
                current_idx = idx + req_toks
            elif net_length in range(9, 17):
                req_toks = 7
                if len(tokens[idx:]) < req_toks:
                    _trunc_error(net_length, req_toks, len(tokens[idx:]))
                    return static_routes
                net_address = ".".join(tokens[idx + 1 : idx + 3] + ["0", "0"])
                gateway = ".".join(tokens[idx + 3 : idx + req_toks])
                current_idx = idx + req_toks
            elif net_length in range(1, 9):
                req_toks = 6
                if len(tokens[idx:]) < req_toks:
                    _trunc_error(net_length, req_toks, len(tokens[idx:]))
                    return static_routes
                net_address = ".".join(
                    tokens[idx + 1 : idx + 2] + ["0", "0", "0"]
                )
                gateway = ".".join(tokens[idx + 2 : idx + req_toks])
                current_idx = idx + req_toks
            elif net_length == 0:
                req_toks = 5
                if len(tokens[idx:]) < req_toks:
                    _trunc_error(net_length, req_toks, len(tokens[idx:]))
                    return static_routes
                net_address = "0.0.0.0"
                gateway = ".".join(tokens[idx + 1 : idx + req_toks])
                current_idx = idx + req_toks
            else:
                LOG.error(
                    'Parsed invalid net length "%s".  Verify DHCP '
                    "rfc3442-classless-static-routes value.",
                    net_length,
                )
                return static_routes

static_routes.append(
                ("%s/%s" % (net_address, net_length), gateway)
            )

return static_routes

@staticmethod
    def get_dhclient_d():
        # find lease files directory
        supported_dirs = [
            "/var/lib/dhclient",
            "/var/lib/dhcp",
            "/var/lib/NetworkManager",
        ]
        for d in supported_dirs:
            if os.path.exists(d) and len(os.listdir(d)) > 0:
                LOG.debug("Using %s lease directory", d)
                return d
        return None

@staticmethod
    def get_latest_lease(lease_d=None):
        # find latest lease file
        if lease_d is None:
            lease_d = IscDhclient.get_dhclient_d()
        if not lease_d:
            return None
        lease_files = os.listdir(lease_d)
        latest_mtime = -1
        latest_file = None

# lease files are named inconsistently across distros.
        # We assume that 'dhclient6' indicates ipv6 and ignore it.
        # ubuntu:
        #   dhclient.<iface>.leases, dhclient.leases, dhclient6.leases
        # centos6:
        #   dhclient-<iface>.leases, dhclient6.leases
        # centos7: ('--' is not a typo)
        #   dhclient--<iface>.lease, dhclient6.leases
        for fname in lease_files:
            if fname.startswith("dhclient6"):
                # avoid files that start with dhclient6 assuming dhcpv6.
                continue
            if not (fname.endswith((".lease", ".leases"))):
                continue

abs_path = os.path.join(lease_d, fname)
            mtime = os.path.getmtime(abs_path)
            if mtime > latest_mtime:
                latest_mtime = mtime
                latest_file = abs_path
        return latest_file

@staticmethod
    def parse_dhcp_server_from_lease_file(lease_file):
        with open(lease_file, "r") as fd:
            for line in fd:
                if "dhcp-server-identifier" in line:
                    words = line.strip(" ;\r\n").split(" ")
                    if len(words) > 2:
                        dhcptok = words[2]
                        LOG.debug("Found DHCP identifier %s", dhcptok)
                        latest_address = dhcptok
        return latest_address

class Dhcpcd:
    client_name = "dhcpcd"

def __init__(self):
        raise NoDHCPLeaseMissingDhclientError("Dhcpcd not yet implemented")

class Udhcpc(DhcpClient):
    client_name = "udhcpc"

def __init__(self):
        self.udhcpc_path = subp.which("udhcpc")
        if not self.udhcpc_path:
            LOG.debug("Skip udhcpc configuration: No udhcpc command found.")
            raise NoDHCPLeaseMissingUdhcpcError()

def dhcp_discovery(
        self,
        interface,
        dhcp_log_func=None,
        distro=None,
    ):
        """Run udhcpc on the interface without scripts or filesystem artifacts.

@param interface: Name of the network interface on which to run udhcpc.
        @param dhcp_log_func: A callable accepting the udhcpc output and
            error streams.

@return: A list of dicts of representing the dhcp leases parsed from
            the udhcpc lease file.
        """
        LOG.debug("Performing a dhcp discovery on %s", interface)

tmp_dir = temp_utils.get_tmp_ancestor(needs_exe=True)
        lease_file = os.path.join(tmp_dir, interface + ".lease.json")
        with contextlib.suppress(FileNotFoundError):
            os.remove(lease_file)

# udhcpc needs the interface up to send initial discovery packets
        distro.net_ops.link_up(interface)

udhcpc_script = os.path.join(tmp_dir, "udhcpc_script")
        util.write_file(udhcpc_script, UDHCPC_SCRIPT, 0o755)

cmd = [
            self.udhcpc_path,
            "-O",
            "staticroutes",
            "-i",
            interface,
            "-s",
            udhcpc_script,
            "-n",  # Exit if lease is not obtained
            "-q",  # Exit after obtaining lease
            "-f",  # Run in foreground
            "-v",
        ]

# For INFINIBAND port the dhcpc must be running with
        # client id option. So here we are checking if the interface is
        # INFINIBAND or not. If yes, we are generating the the client-id to be
        # used with the udhcpc
        if is_ib_interface(interface):
            dhcp_client_identifier = get_ib_interface_hwaddr(
                interface, ethernet_format=True
            )
            cmd.extend(
                ["-x", "0x3d:%s" % dhcp_client_identifier.replace(":", "")]
            )
        try:
            out, err = subp.subp(
                cmd, update_env={"LEASE_FILE": lease_file}, capture=True
            )
        except subp.ProcessExecutionError as error:
            LOG.debug(
                "udhcpc exited with code: %s stderr: %r stdout: %r",
                error.exit_code,
                error.stderr,
                error.stdout,
            )
            raise NoDHCPLeaseError from error

if dhcp_log_func is not None:
            dhcp_log_func(out, err)

lease_json = util.load_json(util.load_file(lease_file))
        static_routes = lease_json["static_routes"].split()
        if static_routes:
            # format: dest1/mask gw1 ... destn/mask gwn
            lease_json["static_routes"] = [
                i for i in zip(static_routes[::2], static_routes[1::2])
            ]
        return [lease_json]

MR SKB