path: root/tools/frr-reload.py

#!/usr/bin/env python3
# SPDX-License-Identifier: GPL-2.0-or-later
# Frr Reloader
# Copyright (C) 2014 Cumulus Networks, Inc.
#
"""
This program
- reads a frr configuration text file
- reads frr's current running configuration via "vtysh -c 'show running'"
- compares the two configs and determines what commands to execute to
  synchronize frr's running configuration with the configuation in the
  text file
"""

from __future__ import print_function, unicode_literals
import argparse
import logging
import os, os.path
import random
import re
import string
import subprocess
import sys
from collections import OrderedDict
from ipaddress import IPv6Address, ip_network
from pprint import pformat


# Python 3
def iteritems(d):
    return iter(d.items())


log = logging.getLogger(__name__)


class VtyshException(Exception):
    pass


class Vtysh(object):
    def __init__(self, bindir=None, confdir=None, sockdir=None, pathspace=None):
        self.bindir = bindir
        self.confdir = confdir
        self.pathspace = pathspace
        self.common_args = [os.path.join(bindir or "", "vtysh")]
        if confdir:
            self.common_args.extend(["--config_dir", confdir])
        if sockdir:
            self.common_args.extend(["--vty_socket", sockdir])
        if pathspace:
            self.common_args.extend(["-N", pathspace])

    def _call(self, args, stdin=None, stdout=None, stderr=None):
        kwargs = {}
        if stdin is not None:
            kwargs["stdin"] = stdin
        if stdout is not None:
            kwargs["stdout"] = stdout
        if stderr is not None:
            kwargs["stderr"] = stderr
        return subprocess.Popen(self.common_args + args, **kwargs)

    def _call_cmd(self, command, stdin=None, stdout=None, stderr=None):
        if isinstance(command, list):
            args = [item for sub in command for item in ["-c", sub]]
        else:
            args = ["-c", command]
        return self._call(args, stdin, stdout, stderr)

    def __call__(self, command, stdouts=None):
        """
        Call a CLI command (e.g. "show running-config")

        Output text is automatically redirected, decoded and returned.
        Multiple commands may be passed as list.
        """
        proc = self._call_cmd(command, stdout=subprocess.PIPE)
        stdout, stderr = proc.communicate()
        if proc.wait() != 0:
            if stdouts is not None:
                stdouts.append(stdout.decode("UTF-8"))
            raise VtyshException(
                'vtysh returned status %d for command "%s"' % (proc.returncode, command)
            )
        return stdout.decode("UTF-8")

    def is_config_available(self):
        """
        Return False if no frr daemon is running or some other vtysh session is
        in 'configuration terminal' mode which will prevent us from making any
        configuration changes.
        """

        output = self("configure")

        if "VTY configuration is locked by other VTY" in output:
            log.error("vtysh 'configure' returned\n%s\n" % (output))
            return False

        return True

    def exec_file(self, filename):
        child = self._call(["-f", filename])
        if child.wait() != 0:
            raise VtyshException(
                "vtysh (exec file) exited with status %d" % (child.returncode)
            )

    def mark_file(self, filename, stdin=None):
        child = self._call(
            ["-m", "-f", filename],
            stdout=subprocess.PIPE,
            stdin=subprocess.PIPE,
            stderr=subprocess.PIPE,
        )
        try:
            stdout, stderr = child.communicate()
        except subprocess.TimeoutExpired:
            child.kill()
            stdout, stderr = child.communicate()
            raise VtyshException("vtysh call timed out!")

        if child.wait() != 0:
            raise VtyshException(
                "vtysh (mark file) exited with status %d:\n%s"
                % (child.returncode, stderr)
            )

        return stdout.decode("UTF-8")

    def mark_show_run(self, daemon=None):
        cmd = "show running-config"
        if daemon:
            cmd += " %s" % daemon
        cmd += " no-header"
        show_run = self._call_cmd(cmd, stdout=subprocess.PIPE)
        mark = self._call(
            ["-m", "-f", "-"], stdin=show_run.stdout, stdout=subprocess.PIPE
        )

        show_run.wait()
        stdout, stderr = mark.communicate()
        mark.wait()

        if show_run.returncode != 0:
            raise VtyshException(
                "vtysh (show running-config) exited with status %d:"
                % (show_run.returncode)
            )
        if mark.returncode != 0:
            raise VtyshException(
                "vtysh (mark running-config) exited with status %d" % (mark.returncode)
            )

        return stdout.decode("UTF-8")


class Context(object):
    """
        A Context object represents a section of frr configuration such as:
    !
    interface swp3
     description swp3 -> r8's swp1
     ipv6 nd suppress-ra
     link-detect
    !

    or a single line context object such as this:

    ip forwarding

    """

    def __init__(self, keys, lines):
        self.keys = keys
        self.lines = lines

        # Keep a dictionary of the lines, this is to make it easy to tell if a
        # line exists in this Context
        self.dlines = OrderedDict()

        for ligne in lines:
            self.dlines[ligne] = True

    def __str__(self):
        return str(self.keys) + " : " + str(self.lines)

    def add_lines(self, lines):
        """
        Add lines to specified context
        """

        self.lines.extend(lines)

        for ligne in lines:
            self.dlines[ligne] = True


def get_normalized_es_id(line):
    """
    The es-id or es-sys-mac need to be converted to lower case
    """
    sub_strs = ["evpn mh es-id", "evpn mh es-sys-mac"]
    for sub_str in sub_strs:
        obj = re.match(sub_str + " (?P<esi>\S*)", line)
        if obj:
            line = "%s %s" % (sub_str, obj.group("esi").lower())
            break
    return line


def get_normalized_mac_ip_line(line):
    if line.startswith("evpn mh es"):
        return get_normalized_es_id(line)

    if not "ipv6 add" in line:
        return get_normalized_ipv6_line(line)

    return line


def get_normalized_interface_vrf(line):
    """
    If 'interface <int_name> vrf <vrf_name>' is present in file,
    we need to remove the explicit "vrf <vrf_name>"
    so that the context information is created
    correctly and configurations are matched appropriately.
    """

    intf_vrf = re.search("interface (\S+) vrf (\S+)", line)
    if intf_vrf:
        old_line = "vrf %s" % intf_vrf.group(2)
        new_line = line.replace(old_line, "").strip()
        return new_line

    return line


# This dictionary contains a tree of all commands that we know start a
# new multi-line context. All other commands are treated either as
# commands inside a multi-line context or as single-line contexts. This
# dictionary should be updated whenever a new node is added to FRR.
ctx_keywords = {
    "router bgp ": {
        "address-family ": {
            "vni ": {},
        },
        "vnc defaults": {},
        "vnc nve-group ": {},
        "vnc l2-group ": {},
        "vrf-policy ": {},
        "bmp targets ": {},
        "segment-routing srv6": {},
    },
    "router rip": {},
    "router ripng": {},
    "router isis ": {},
    "router openfabric ": {},
    "router ospf": {},
    "router ospf6": {},
    "router eigrp ": {},
    "router babel": {},
    "mpls ldp": {"address-family ": {"interface ": {}}},
    "l2vpn ": {"member pseudowire ": {}},
    "key chain ": {"key ": {}},
    "vrf ": {},
    "interface ": {"link-params": {}},
    "pseudowire ": {},
    "segment-routing": {
        "traffic-eng": {
            "segment-list ": {},
            "policy ": {"candidate-path ": {}},
            "pcep": {"pcc": {}, "pce ": {}, "pce-config ": {}},
        },
        "srv6": {"locators": {"locator ": {}}},
    },
    "nexthop-group ": {},
    "route-map ": {},
    "pbr-map ": {},
    "rpki": {},
    "bfd": {"peer ": {}, "profile ": {}},
    "line vty": {},
}


class Config(object):
    """
    A frr configuration is stored in a Config object. A Config object
    contains a dictionary of Context objects where the Context keys
    ('router ospf' for example) are our dictionary key.
    """

    def __init__(self, vtysh):
        self.lines = []
        self.contexts = OrderedDict()
        self.vtysh = vtysh

    def load_from_file(self, filename):
        """
        Read configuration from specified file and slurp it into internal memory
        The internal representation has been marked appropriately by passing it
        through vtysh with the -m parameter
        """
        log.info("Loading Config object from file %s", filename)

        file_output = self.vtysh.mark_file(filename)

        for line in file_output.split("\n"):
            line = line.strip()

            # Compress duplicate whitespaces
            line = " ".join(line.split())

            # Remove 'vrf <vrf_name>' from 'interface <x> vrf <vrf_name>'
            if line.startswith("interface ") and "vrf" in line:
                line = get_normalized_interface_vrf(line)

            if ":" in line:
                line = get_normalized_mac_ip_line(line)

            # vrf static routes can be added in two ways. The old way is:
            #
            # "ip route x.x.x.x/x y.y.y.y vrf <vrfname>"
            #
            # but it's rendered in the configuration as the new way::
            #
            # vrf <vrf-name>
            #  ip route x.x.x.x/x y.y.y.y
            #  exit-vrf
            #
            # this difference causes frr-reload to not consider them a
            # match and delete vrf static routes incorrectly.
            # fix the old way to match new "show running" output so a
            # proper match is found.
            if (
                line.startswith("ip route ") or line.startswith("ipv6 route ")
            ) and " vrf " in line:
                newline = line.split(" ")
                vrf_index = newline.index("vrf")
                vrf_ctx = newline[vrf_index] + " " + newline[vrf_index + 1]
                del newline[vrf_index : vrf_index + 2]
                newline = " ".join(newline)
                self.lines.append(vrf_ctx)
                self.lines.append(newline)
                self.lines.append("exit-vrf")
                line = "end"

            self.lines.append(line)

        self.load_contexts()

    def load_from_show_running(self, daemon):
        """
        Read running configuration and slurp it into internal memory
        The internal representation has been marked appropriately by passing it
        through vtysh with the -m parameter
        """
        log.info("Loading Config object from vtysh show running")

        config_text = self.vtysh.mark_show_run(daemon)

        for line in config_text.split("\n"):
            line = line.strip()

            if (
                line == "Building configuration..."
                or line == "Current configuration:"
                or not line
            ):
                continue

            self.lines.append(line)

        self.load_contexts()

    def get_lines(self):
        """
        Return the lines read in from the configuration
        """
        return "\n".join(self.lines)

    def get_contexts(self):
        """
        Return the parsed context as strings for display, log etc.
        """
        for _, ctx in sorted(iteritems(self.contexts)):
            print(str(ctx))

    def save_contexts(self, key, lines):
        """
        Save the provided key and lines as a context
        """
        if not key:
            return

        # IP addresses specified in "network" statements, "ip prefix-lists"
        # etc. can differ in the host part of the specification the user
        # provides and what the running config displays. For example, user can
        # specify 11.1.1.1/24, and the running config displays this as
        # 11.1.1.0/24. Ensure we don't do a needless operation for such lines.
        # IS-IS & OSPFv3 have no "network" support.
        re_key_rt = re.match(r"(ip|ipv6)\s+route\s+([A-Fa-f:.0-9/]+)(.*)$", key[0])
        if re_key_rt:
            addr = re_key_rt.group(2)
            if "/" in addr:
                try:
                    newaddr = ip_network(addr, strict=False)
                    key[0] = "%s route %s/%s%s" % (
                        re_key_rt.group(1),
                        str(newaddr.network_address),
                        newaddr.prefixlen,
                        re_key_rt.group(3),
                    )
                except ValueError:
                    pass

        re_key_rt = re.match(
            r"(ip|ipv6)\s+prefix-list(.*)(permit|deny)\s+([A-Fa-f:.0-9/]+)(.*)$", key[0]
        )
        if re_key_rt:
            addr = re_key_rt.group(4)
            if "/" in addr:
                try:
                    network_addr = ip_network(addr, strict=False)
                    newaddr = "%s/%s" % (
                        str(network_addr.network_address),
                        network_addr.prefixlen,
                    )
                except ValueError:
                    newaddr = addr
            else:
                newaddr = addr

            legestr = re_key_rt.group(5)
            re_lege = re.search(r"(.*)le\s+(\d+)\s+ge\s+(\d+)(.*)", legestr)
            if re_lege:
                legestr = "%sge %s le %s%s" % (
                    re_lege.group(1),
                    re_lege.group(3),
                    re_lege.group(2),
                    re_lege.group(4),
                )

            key[0] = "%s prefix-list%s%s %s%s" % (
                re_key_rt.group(1),
                re_key_rt.group(2),
                re_key_rt.group(3),
                newaddr,
                legestr,
            )

        if lines and key[0].startswith("router bgp"):
            newlines = []
            for line in lines:
                re_net = re.match(r"network\s+([A-Fa-f:.0-9/]+)(.*)$", line)
                if re_net:
                    addr = re_net.group(1)
                    if "/" not in addr and key[0].startswith("router bgp"):
                        # This is most likely an error because with no
                        # prefixlen, BGP treats the prefixlen as 8
                        addr = addr + "/8"

                    try:
                        network_addr = ip_network(addr, strict=False)
                        line = "network %s/%s %s" % (
                            str(network_addr.network_address),
                            network_addr.prefixlen,
                            re_net.group(2),
                        )
                        newlines.append(line)
                    except ValueError:
                        # Really this should be an error. Whats a network
                        # without an IP Address following it ?
                        newlines.append(line)
                else:
                    newlines.append(line)
            lines = newlines

        # More fixups in user specification and what running config shows.
        # "null0" in routes must be replaced by Null0.
        if (
            key[0].startswith("ip route")
            or key[0].startswith("ipv6 route")
            and "null0" in key[0]
        ):
            key[0] = re.sub(r"\s+null0(\s*$)", " Null0", key[0])

        if lines and key[0].startswith("vrf "):
            newlines = []
            for line in lines:
                if line.startswith("ip route ") or line.startswith("ipv6 route "):
                    if "null0" in line:
                        line = re.sub(r"\s+null0(\s*$)", " Null0", line)
                    newlines.append(line)
                else:
                    newlines.append(line)
            lines = newlines

        if lines:
            if tuple(key) not in self.contexts:
                ctx = Context(tuple(key), lines)
                self.contexts[tuple(key)] = ctx
            else:
                ctx = self.contexts[tuple(key)]
                ctx.add_lines(lines)

        else:
            if tuple(key) not in self.contexts:
                ctx = Context(tuple(key), [])
                self.contexts[tuple(key)] = ctx

    def load_contexts(self):
        """
        Parse the configuration and create contexts for each appropriate block

        The end of a context is flagged via the 'end' keyword:

        !
        interface swp52
         ipv6 nd suppress-ra
         link-detect
        !
        end
        router bgp 10
         bgp router-id 10.0.0.1
         bgp log-neighbor-changes
         no bgp default ipv4-unicast
         neighbor EBGP peer-group
         neighbor EBGP advertisement-interval 1
         neighbor EBGP timers connect 10
         neighbor 2001:40:1:4::6 remote-as 40
         neighbor 2001:40:1:8::a remote-as 40
        !
        end
         address-family ipv6
         neighbor IBGPv6 activate
         neighbor 2001:10::2 peer-group IBGPv6
         neighbor 2001:10::3 peer-group IBGPv6
         exit-address-family
        !
        end
        router ospf
         ospf router-id 10.0.0.1
         log-adjacency-changes detail
         timers throttle spf 0 50 5000
        !
        end

        The code assumes that its working on the output from the "vtysh -m"
        command. That provides the appropriate markers to signify end of
        a context. This routine uses that to build the contexts for the
        config.

        There are single line contexts such as "log file /media/node/zebra.log"
        and multi-line contexts such as "router ospf" and subcontexts
        within a context such as "address-family" within "router bgp"
        In each of these cases, the first line of the context becomes the
        key of the context. So "router bgp 10" is the key for the non-address
        family part of bgp, "router bgp 10, address-family ipv6 unicast" is
        the key for the subcontext and so on.
        """
        # stack of context keys
        ctx_keys = []
        # stack of context keywords
        cur_ctx_keywords = [ctx_keywords]
        # list of stored commands
        cur_ctx_lines = []

        for line in self.lines:
            if not line:
                continue

            if line.startswith("!") or line.startswith("#"):
                continue

            if line.startswith("exit"):
                # ignore on top level
                if len(ctx_keys) == 0:
                    continue

                # save current context
                self.save_contexts(ctx_keys, cur_ctx_lines)

                # exit current context
                log.debug("LINE %-50s: exit context %-50s", line, ctx_keys)

                ctx_keys.pop()
                cur_ctx_keywords.pop()
                cur_ctx_lines = []

                continue

            if line.startswith("end"):
                # exit all contexts
                while len(ctx_keys) > 0:
                    # save current context
                    self.save_contexts(ctx_keys, cur_ctx_lines)

                    # exit current context
                    log.debug("LINE %-50s: exit context %-50s", line, ctx_keys)

                    ctx_keys.pop()
                    cur_ctx_keywords.pop()
                    cur_ctx_lines = []

                continue

            new_ctx = False

            # check if the line is a context-entering keyword
            for k, v in cur_ctx_keywords[-1].items():
                if line.startswith(k):
                    # candidate-path is a special case. It may be a node and
                    # may be a single-line command. The distinguisher is the
                    # word "dynamic" or "explicit" at the middle of the line.
                    # It was perhaps not the best choice by the pathd authors
                    # but we have what we have.
                    if k == "candidate-path " and "explicit" in line:
                        # this is a single-line command
                        break

                    # save current context
                    self.save_contexts(ctx_keys, cur_ctx_lines)

                    # enter new context
                    new_ctx = True
                    ctx_keys.append(line)
                    cur_ctx_keywords.append(v)
                    cur_ctx_lines = []

                    log.debug("LINE %-50s: enter context %-50s", line, ctx_keys)
                    break

            if new_ctx:
                continue

            if len(ctx_keys) == 0:
                log.debug("LINE %-50s: single-line context", line)
                self.save_contexts([line], [])
            else:
                log.debug("LINE %-50s: add to current context %-50s", line, ctx_keys)
                cur_ctx_lines.append(line)

        # Save the context of the last one
        if len(ctx_keys) > 0:
            self.save_contexts(ctx_keys, cur_ctx_lines)


def lines_to_config(ctx_keys, line, delete):
    """
    Return the command as it would appear in frr.conf
    """
    cmd = []

    # If there's no `line` and `ctx_keys` length is 1, then it may be a single-line command.
    # In this case, we should treat it as a single command in an empty context.
    if len(ctx_keys) == 1 and not line:
        single = True

        for k, v in ctx_keywords.items():
            if ctx_keys[0].startswith(k):
                single = False
                break

        if single:
            line = ctx_keys[0]
            ctx_keys = []

    if line:
        for i, ctx_key in enumerate(ctx_keys):
            cmd.append(" " * i + ctx_key)

        line = line.lstrip()
        indent = len(ctx_keys) * " "

        # There are some commands that are on by default so their "no" form will be
        # displayed in the config.  "no bgp default ipv4-unicast" is one of these.
        # If we need to remove this line we do so by adding "bgp default ipv4-unicast",
        # not by doing a "no no bgp default ipv4-unicast"
        if delete:
            if line.startswith("no "):
                cmd.append("%s%s" % (indent, line[3:]))
            else:
                cmd.append("%sno %s" % (indent, line))

        else:
            cmd.append(indent + line)

        for i in reversed(range(len(ctx_keys))):
            cmd.append(" " * i + "exit")

    # If line is None then we are typically deleting an entire
    # context ('no router ospf' for example)
    else:
        for i, ctx_key in enumerate(ctx_keys[:-1]):
            cmd.append("%s%s" % (" " * i, ctx_key))

        # Only put the 'no' on the last sub-context
        if delete:
            if ctx_keys[-1].startswith("no "):
                cmd.append("%s%s" % (" " * (len(ctx_keys) - 1), ctx_keys[-1][3:]))
            else:
                cmd.append("%sno %s" % (" " * (len(ctx_keys) - 1), ctx_keys[-1]))
        else:
            cmd.append("%s%s" % (" " * (len(ctx_keys) - 1), ctx_keys[-1]))
            cmd.append("%sexit" % (" " * (len(ctx_keys) - 1)))

        for i in reversed(range(len(ctx_keys) - 1)):
            cmd.append(" " * i + "exit")

    return cmd


def get_normalized_ipv6_line(line):
    """
    Return a normalized IPv6 line as produced by frr,
    with all letters in lower case and trailing and leading
    zeros removed, and only the network portion present if
    the IPv6 word is a network
    """
    norm_line = ""
    words = line.split(" ")
    for word in words:
        if ":" in word:
            norm_word = None
            if "/" in word:
                try:
                    v6word = ip_network(word, strict=False)
                    norm_word = "%s/%s" % (
                        str(v6word.network_address),
                        v6word.prefixlen,
                    )
                except ValueError:
                    pass
            if not norm_word:
                try:
                    norm_word = "%s" % IPv6Address(word)
                except ValueError:
                    norm_word = word
        else:
            norm_word = word
        norm_line = norm_line + " " + norm_word

    return norm_line.strip()


def line_exist(lines, target_ctx_keys, target_line, exact_match=True):
    for ctx_keys, line in lines:
        if ctx_keys == target_ctx_keys:
            if exact_match:
                if line == target_line:
                    return True
            else:
                if line.startswith(target_line):
                    return True
    return False


def bgp_delete_inst_move_line(lines_to_del):
    # Deletion of bgp default inst followed by
    # bgp vrf inst leads to issue of default
    # instance can not be removed.
    # Move the bgp default instance line to end.
    bgp_defult_inst = False
    bgp_vrf_inst = False

    for ctx_keys, line in lines_to_del:
        # Find bgp default inst
        if (
            ctx_keys[0].startswith("router bgp")
            and not line
            and "vrf" not in ctx_keys[0]
        ):
            bgp_defult_inst = True
        # Find bgp vrf inst
        if ctx_keys[0].startswith("router bgp") and not line and "vrf" in ctx_keys[0]:
            bgp_vrf_inst = True

    if bgp_defult_inst and bgp_vrf_inst:
        for ctx_keys, line in lines_to_del:
            # move bgp default inst to end
            if (
                ctx_keys[0].startswith("router bgp")
                and not line
                and "vrf" not in ctx_keys[0]
            ):
                lines_to_del.remove((ctx_keys, line))
                lines_to_del.append((ctx_keys, line))


def bgp_delete_nbr_remote_as_line(lines_to_add):
    # Handle deletion of neighbor <nbr> remote-as line from
    # lines_to_add if the nbr is configured with peer-group and
    # peer-group has remote-as config present.
    # 'neighbor <nbr> remote-as change on peer is not allowed
    # if the peer is part of peer-group and peer-group has
    # remote-as config.

    pg_dict = dict()
    found_pg_cmd = False

    # Find all peer-group commands; create dict of each peer-group
    # to store assoicated neighbor as value
    for ctx_keys, line in lines_to_add:
        if (
            ctx_keys[0].startswith("router bgp")
            and line
            and line.startswith("neighbor ")
        ):
            # {'router bgp 65001': {'PG': [], 'PG1': []},
            # 'router bgp 65001 vrf vrf1': {'PG': [], 'PG1': []}}
            if ctx_keys[0] not in pg_dict:
                pg_dict[ctx_keys[0]] = dict()
            # find 'neighbor <pg_name> peer-group'
            re_pg = re.match("neighbor (\S+) peer-group$", line)
            if re_pg and re_pg.group(1) not in pg_dict[ctx_keys[0]]:
                pg_dict[ctx_keys[0]][re_pg.group(1)] = {
                    "nbr": list(),
                    "remoteas": False,
                }
                found_pg_cmd = True

    # Do nothing if there is no any "peer-group"
    if found_pg_cmd is False:
        return

    # Find peer-group with remote-as command, also search neighbor
    # associated to peer-group and store into peer-group dict
    for ctx_keys, line in lines_to_add:
        if (
            ctx_keys[0].startswith("router bgp")
            and line
            and line.startswith("neighbor ")
        ):
            if ctx_keys[0] in pg_dict:
                for pg_key in pg_dict[ctx_keys[0]]:
                    # Find 'neighbor <pg_name> remote-as'
                    pg_rmtas = "neighbor %s remote-as (\S+)" % pg_key
                    re_pg_rmtas = re.search(pg_rmtas, line)
                    if re_pg_rmtas:
                        pg_dict[ctx_keys[0]][pg_key]["remoteas"] = True

                    # Find 'neighbor <peer> [interface] peer-group <pg_name>'
                    nb_pg = "neighbor (\S+) peer-group %s$" % pg_key
                    re_nbr_pg = re.search(nb_pg, line)
                    if (
                        re_nbr_pg
                        and re_nbr_pg.group(1) not in pg_dict[ctx_keys[0]][pg_key]
                    ):
                        pg_dict[ctx_keys[0]][pg_key]["nbr"].append(re_nbr_pg.group(1))

    # Find any neighbor <nbr> remote-as config line check if the nbr
    # is in the peer group's list of nbrs. Remove 'neighbor <nbr> remote-as <>'
    # from lines_to_add.
    lines_to_del_from_add = []
    for ctx_keys, line in lines_to_add:
        if (
            ctx_keys[0].startswith("router bgp")
            and line
            and line.startswith("neighbor ")
        ):
            nbr_rmtas = "neighbor (\S+) remote-as.*"
            re_nbr_rmtas = re.search(nbr_rmtas, line)
            if re_nbr_rmtas and ctx_keys[0] in pg_dict:
                for pg in pg_dict[ctx_keys[0]]:
                    if pg_dict[ctx_keys[0]][pg]["remoteas"] == True:
                        for nbr in pg_dict[ctx_keys[0]][pg]["nbr"]:
                            if re_nbr_rmtas.group(1) == nbr:
                                lines_to_del_from_add.append((ctx_keys, line))

    for ctx_keys, line in lines_to_del_from_add:
        lines_to_add.remove((ctx_keys, line))


def bgp_remove_neighbor_cfg(lines_to_del, del_nbr_dict):
    # This method handles deletion of bgp neighbor configs,
    # if there is neighbor to peer-group cmd is in delete list.
    # As 'no neighbor .* peer-group' deletes the neighbor,
    # subsequent neighbor speciic config line deletion results
    # in error.
    lines_to_del_to_del = []

    for ctx_keys, line in lines_to_del:
        if (
            ctx_keys[0].startswith("router bgp")
            and line
            and line.startswith("neighbor ")
        ):
            if ctx_keys[0] in del_nbr_dict:
                for nbr in del_nbr_dict[ctx_keys[0]]:
                    re_nbr_pg = re.search("neighbor (\S+) .*peer-group (\S+)", line)
                    nb_exp = "neighbor %s .*" % nbr
                    if not re_nbr_pg:
                        re_nb = re.search(nb_exp, line)
                        if re_nb:
                            lines_to_del_to_del.append((ctx_keys, line))

    for ctx_keys, line in lines_to_del_to_del:
        lines_to_del.remove((ctx_keys, line))


def bgp_delete_move_lines(lines_to_add, lines_to_del):
    # This method handles deletion of bgp peer group config.
    # The objective is to delete config lines related to peers
    # associated with the peer-group and move the peer-group
    # config line to the end of the lines_to_del list.

    bgp_delete_nbr_remote_as_line(lines_to_add)

    del_dict = dict()
    del_nbr_dict = dict()
    # Stores the lines to move to the end of the pending list.
    lines_to_del_to_del = []
    # Stores the lines to move to end of the pending list.
    lines_to_del_to_app = []
    found_pg_del_cmd = False

    # When "neighbor <pg_name> peer-group" under a bgp instance is removed,
    # it also deletes the associated peer config. Any config line below no form of
    # peer-group related to a peer are errored out as the peer no longer exists.
    # To cleanup peer-group and associated peer(s) configs:
    # - Remove all the peers config lines from the pending list (lines_to_del list).
    # - Move peer-group deletion line to the end of the pending list, to allow
    # removal of any of the peer-group specific configs.
    #
    # Create a dictionary of config context (i.e. router bgp vrf x).
    # Under each context node, create a dictionary of a peer-group name.
    # Append a peer associated to the peer-group into a list under a peer-group node.
    # Remove all of the peer associated config lines from the pending list.
    # Append peer-group deletion line to end of the pending list.
    #
    # Example:
    #   neighbor underlay peer-group
    #   neighbor underlay remote-as external
    #   neighbor underlay advertisement-interval 0
    #   neighbor underlay timers 3 9
    #   neighbor underlay timers connect 10
    #   neighbor swp1 interface peer-group underlay
    #   neighbor swp1 advertisement-interval 0
    #   neighbor swp1 timers 3 9
    #   neighbor swp1 timers connect 10
    #   neighbor swp2 interface peer-group underlay
    #   neighbor swp2 advertisement-interval 0
    #   neighbor swp2 timers 3 9
    #   neighbor swp2 timers connect 10
    #   neighbor swp3 interface peer-group underlay
    #   neighbor uplink1 interface remote-as internal
    #   neighbor uplink1 advertisement-interval 0
    #   neighbor uplink1 timers 3 9
    #   neighbor uplink1 timers connect 10

    # New order:
    #   "router bgp 200  no bgp bestpath as-path multipath-relax"
    #   "router bgp 200  no neighbor underlay advertisement-interval 0"
    #   "router bgp 200  no neighbor underlay timers 3 9"
    #   "router bgp 200  no neighbor underlay timers connect 10"
    #   "router bgp 200  no neighbor uplink1 advertisement-interval 0"
    #   "router bgp 200  no neighbor uplink1 timers 3 9"
    #   "router bgp 200  no neighbor uplink1 timers connect 10"
    #   "router bgp 200  no neighbor underlay remote-as external"
    #   "router bgp 200  no neighbor uplink1 interface remote-as internal"
    #   "router bgp 200  no neighbor underlay peer-group"

    for ctx_keys, line in lines_to_del:
        if (
            ctx_keys[0].startswith("router bgp")
            and line
            and line.startswith("neighbor ")
        ):
            # When 'neighbor <peer> remote-as <>' is removed it deletes the peer,
            # there might be a peer associated config which also needs to be removed
            # prior to peer.
            # Append the 'neighbor <peer> remote-as <>' to the lines_to_del.
            # Example:
            #
            #  neighbor uplink1 interface remote-as internal
            #  neighbor uplink1 advertisement-interval 0
            #  neighbor uplink1 timers 3 9
            #  neighbor uplink1 timers connect 10

            #  Move to end:
            #  neighbor uplink1 advertisement-interval 0
            #  neighbor uplink1 timers 3 9
            #  neighbor uplink1 timers connect 10
            #  ...
            #
            #  neighbor uplink1 interface remote-as internal
            #
            # 'no neighbor peer [interface] remote-as <>'
            nb_remoteas = "neighbor (\S+) .*remote-as (\S+)"
            re_nb_remoteas = re.search(nb_remoteas, line)
            if re_nb_remoteas:
                lines_to_del_to_app.append((ctx_keys, line))

            # 'no neighbor peer [interface] peer-group <>' is in lines_to_del
            # copy the neighbor and look for all config removal lines associated
            # to neighbor and delete them from the lines_to_del
            re_nbr_pg = re.search("neighbor (\S+) .*peer-group (\S+)", line)
            if re_nbr_pg:
                if ctx_keys[0] not in del_nbr_dict:
                    del_nbr_dict[ctx_keys[0]] = list()
                if re_nbr_pg.group(1) not in del_nbr_dict[ctx_keys[0]]:
                    del_nbr_dict[ctx_keys[0]].append(re_nbr_pg.group(1))

            # {'router bgp 65001': {'PG': [], 'PG1': []},
            # 'router bgp 65001 vrf vrf1': {'PG': [], 'PG1': []}}
            if ctx_keys[0] not in del_dict:
                del_dict[ctx_keys[0]] = dict()
            # find 'no neighbor <pg_name> peer-group'
            re_pg = re.match("neighbor (\S+) peer-group$", line)
            if re_pg and re_pg.group(1) not in del_dict[ctx_keys[0]]:
                del_dict[ctx_keys[0]][re_pg.group(1)] = list()
                found_pg_del_cmd = True

    # move neighbor remote-as lines at the end
    for ctx_keys, line in lines_to_del_to_app:
        lines_to_del.remove((ctx_keys, line))
        lines_to_del.append((ctx_keys, line))

    if found_pg_del_cmd == False:
        bgp_delete_inst_move_line(lines_to_del)
        if del_nbr_dict:
            bgp_remove_neighbor_cfg(lines_to_del, del_nbr_dict)
        return (lines_to_add, lines_to_del)

    # {'router bgp 65001': {'PG': ['10.1.1.2'], 'PG1': ['10.1.1.21']},
    #  'router bgp 65001 vrf vrf1': {'PG': ['10.1.1.2'], 'PG1': ['10.1.1.21']}}
    for ctx_keys, line in lines_to_del:
        if (
            ctx_keys[0].startswith("router bgp")
            and line
            and line.startswith("neighbor ")
        ):
            if ctx_keys[0] in del_dict:
                for pg_key in del_dict[ctx_keys[0]]:
                    # 'neighbor <peer> [interface] peer-group <pg_name>'
                    nb_pg = "neighbor (\S+) .*peer-group %s$" % pg_key
                    re_nbr_pg = re.search(nb_pg, line)
                    if (
                        re_nbr_pg
                        and re_nbr_pg.group(1) not in del_dict[ctx_keys[0]][pg_key]
                    ):
                        del_dict[ctx_keys[0]][pg_key].append(re_nbr_pg.group(1))

    lines_to_del_to_app = []
    for ctx_keys, line in lines_to_del:
        if (
            ctx_keys[0].startswith("router bgp")
            and line
            and line.startswith("neighbor ")
        ):
            if ctx_keys[0] in del_dict:
                for pg in del_dict[ctx_keys[0]]:
                    for nbr in del_dict[ctx_keys[0]][pg]:
                        nb_exp = "neighbor %s .*" % nbr
                        re_nb = re.search(nb_exp, line)
                        # add peer configs to delete list.
                        if re_nb and line not in lines_to_del_to_del:
                            lines_to_del_to_del.append((ctx_keys, line))

                    pg_exp = "neighbor %s peer-group$" % pg
                    re_pg = re.match(pg_exp, line)
                    if re_pg:
                        lines_to_del_to_app.append((ctx_keys, line))

    for ctx_keys, line in lines_to_del_to_del:
        lines_to_del.remove((ctx_keys, line))

    for ctx_keys, line in lines_to_del_to_app:
        lines_to_del.remove((ctx_keys, line))
        lines_to_del.append((ctx_keys, line))

    bgp_delete_inst_move_line(lines_to_del)

    return (lines_to_add, lines_to_del)


def pim_delete_move_lines(lines_to_add, lines_to_del):
    # Under interface context, if 'no ip pim' is present
    # remove subsequent 'no ip pim <blah>' options as it
    # they are implicitly deleted by 'no ip pim'.
    # Remove all such depdendent options from delete
    # pending list.
    pim_disable = False
    lines_to_del_to_del = []

    index = -1
    for ctx_keys, line in lines_to_del:
        index = index + 1
        if ctx_keys[0].startswith("interface") and line and line == "ip pim":
            pim_disable = True

        # no ip msdp peer <> does not accept source so strip it off.
        if line and line.startswith("ip msdp peer "):
            pim_msdp_peer = re.search("ip msdp peer (\S+) source (\S+)", line)
            if pim_msdp_peer:
                source_sub_str = "source %s" % pim_msdp_peer.group(2)
                new_line = line.replace(source_sub_str, "").strip()
                lines_to_del.remove((ctx_keys, line))
                lines_to_del.insert(index, (ctx_keys, new_line))

    if pim_disable:
        for ctx_keys, line in lines_to_del:
            if (
                ctx_keys[0].startswith("interface")
                and line
                and (line.startswith("ip pim ") or line.startswith("ip multicast "))
            ):
                lines_to_del_to_del.append((ctx_keys, line))

    for ctx_keys, line in lines_to_del_to_del:
        lines_to_del.remove((ctx_keys, line))

    return (lines_to_add, lines_to_del)


def delete_move_lines(lines_to_add, lines_to_del):
    lines_to_add, lines_to_del = bgp_delete_move_lines(lines_to_add, lines_to_del)
    lines_to_add, lines_to_del = pim_delete_move_lines(lines_to_add, lines_to_del)

    return (lines_to_add, lines_to_del)


def ignore_delete_re_add_lines(lines_to_add, lines_to_del):
    # Quite possibly the most confusing (while accurate) variable names in history
    lines_to_add_to_del = []
    lines_to_del_to_del = []

    index = -1
    for ctx_keys, line in lines_to_del:
        deleted = False

        # no form of route-map description command only
        # accept 'no description', replace 'no description blah'
        # to just 'no description'.
        index = index + 1
        if (
            ctx_keys[0].startswith("route-map")
            and line
            and line.startswith("description ")
        ):
            lines_to_del.remove((ctx_keys, line))
            lines_to_del.insert(index, (ctx_keys, "description"))

        # interface x ; description blah
        # no form of description does not accept any argument,
        # strip arg before rendering
        if (
            ctx_keys[0].startswith("interface ")
            and line
            and line.startswith("description ")
        ):
            lines_to_del.remove((ctx_keys, line))
            lines_to_del.insert(index, (ctx_keys, "description"))

        # If there is a change in the segment routing block ranges, do it
        # in-place, to avoid requesting spurious label chunks which might fail
        if line and "segment-routing global-block" in line:
            for add_key, add_line in lines_to_add:
                if (
                    ctx_keys[0] == add_key[0]
                    and add_line
                    and "segment-routing global-block" in add_line
                ):
                    lines_to_del_to_del.append((ctx_keys, line))
                    break
            continue

        if ctx_keys[0].startswith("router bgp") and line:
            if line.startswith("neighbor "):
                # BGP changed how it displays swpX peers that are part of peer-group. Older
                # versions of frr would display these on separate lines:
                #     neighbor swp1 interface
                #     neighbor swp1 peer-group FOO
                #
                # but today we display via a single line
                #     neighbor swp1 interface peer-group FOO
                #
                # This change confuses frr-reload.py so check to see if we are deleting
                #     neighbor swp1 interface peer-group FOO
                #
                # and adding
                #     neighbor swp1 interface
                #     neighbor swp1 peer-group FOO
                #
                # If so then chop the del line and the corresponding add lines
                re_swpx_int_peergroup = re.search(
                    "neighbor (\S+) interface peer-group (\S+)", line
                )
                re_swpx_int_v6only_peergroup = re.search(
                    "neighbor (\S+) interface v6only peer-group (\S+)", line
                )

                if re_swpx_int_peergroup or re_swpx_int_v6only_peergroup:
                    swpx_interface = None
                    swpx_peergroup = None

                    if re_swpx_int_peergroup:
                        swpx = re_swpx_int_peergroup.group(1)
                        peergroup = re_swpx_int_peergroup.group(2)
                        swpx_interface = "neighbor %s interface" % swpx
                    elif re_swpx_int_v6only_peergroup:
                        swpx = re_swpx_int_v6only_peergroup.group(1)
                        peergroup = re_swpx_int_v6only_peergroup.group(2)
                        swpx_interface = "neighbor %s interface v6only" % swpx

                    swpx_peergroup = "neighbor %s peer-group %s" % (swpx, peergroup)
                    found_add_swpx_interface = line_exist(
                        lines_to_add, ctx_keys, swpx_interface
                    )
                    found_add_swpx_peergroup = line_exist(
                        lines_to_add, ctx_keys, swpx_peergroup
                    )
                    tmp_ctx_keys = tuple(list(ctx_keys))

                    if not found_add_swpx_peergroup:
                        tmp_ctx_keys = list(ctx_keys)
                        tmp_ctx_keys.append("address-family ipv4 unicast")
                        tmp_ctx_keys = tuple(tmp_ctx_keys)
                        found_add_swpx_peergroup = line_exist(
                            lines_to_add, tmp_ctx_keys, swpx_peergroup
                        )

                        if not found_add_swpx_peergroup:
                            tmp_ctx_keys = list(ctx_keys)
                            tmp_ctx_keys.append("address-family ipv6 unicast")
                            tmp_ctx_keys = tuple(tmp_ctx_keys)
                            found_add_swpx_peergroup = line_exist(
                                lines_to_add, tmp_ctx_keys, swpx_peergroup
                            )

                    if found_add_swpx_interface and found_add_swpx_peergroup:
                        deleted = True
                        lines_to_del_to_del.append((ctx_keys, line))
                        lines_to_add_to_del.append((ctx_keys, swpx_interface))
                        lines_to_add_to_del.append((tmp_ctx_keys, swpx_peergroup))

                # Changing the bfd timers on neighbors is allowed without doing
                # a delete/add process. Since doing a "no neighbor blah bfd
                # ..." will cause the peer to bounce unnecessarily, just skip
                # the delete and just do the add.
                re_nbr_bfd_timers = re.search(
                    r"neighbor (\S+) bfd (\S+) (\S+) (\S+)", line
                )

                if re_nbr_bfd_timers:
                    nbr = re_nbr_bfd_timers.group(1)
                    bfd_nbr = "neighbor %s" % nbr
                    bfd_search_string = bfd_nbr + r" bfd (\S+) (\S+) (\S+)"

                    for ctx_keys, add_line in lines_to_add:
                        if ctx_keys[0].startswith("router bgp"):
                            re_add_nbr_bfd_timers = re.search(
                                bfd_search_string, add_line
                            )

                            if re_add_nbr_bfd_timers:
                                found_add_bfd_nbr = line_exist(
                                    lines_to_add, ctx_keys, bfd_nbr, False
                                )

                                if found_add_bfd_nbr:
                                    lines_to_del_to_del.append((ctx_keys, line))

                # Neighbor changes of route-maps need to be accounted for in
                # that we do not want to do a `no route-map...` `route-map
                # ....` when changing a route-map.  This is bad mojo as that we
                # will send/receive data we don't want.  Additionally we need
                # to ensure that if we have different afi/safi variants that
                # they actually match and if we are going from a very old style
                # command such that the neighbor command is under the `router
                # bgp ..` node that we need to handle that appropriately
                re_nbr_rm = re.search("neighbor(.*)route-map(.*)(in|out)$", line)
                if re_nbr_rm:
                    adjust_for_bgp_node = 0
                    neighbor_name = re_nbr_rm.group(1)
                    rm_name_del = re_nbr_rm.group(2)
                    dir = re_nbr_rm.group(3)
                    search = "neighbor%sroute-map(.*)%s" % (neighbor_name, dir)
                    save_line = "EMPTY"
                    for ctx_keys_al, add_line in lines_to_add:
                        if ctx_keys_al[0].startswith("router bgp"):
                            if add_line:
                                rm_match = re.search(search, add_line)
                            if rm_match:
                                rm_name_add = rm_match.group(1)
                                if rm_name_add == rm_name_del:
                                    continue
                                if len(ctx_keys_al) == 1:
                                    save_line = line
                                    adjust_for_bgp_node = 1
                                else:
                                    if (
                                        len(ctx_keys) > 1
                                        and len(ctx_keys_al) > 1
                                        and ctx_keys[1] == ctx_keys_al[1]
                                    ):
                                        lines_to_del_to_del.append((ctx_keys_al, line))

                    if adjust_for_bgp_node == 1:
                        for ctx_keys_dl, dl_line in lines_to_del:
                            if (
                                ctx_keys_dl[0].startswith("router bgp")
                                and len(ctx_keys_dl) > 1
                                and ctx_keys_dl[1] == "address-family ipv4 unicast"
                            ):
                                if save_line == dl_line:
                                    lines_to_del_to_del.append((ctx_keys_dl, save_line))

                # We changed how we display the neighbor interface command. Older
                # versions of frr would display the following:
                #     neighbor swp1 interface
                #     neighbor swp1 remote-as external
                #     neighbor swp1 capability extended-nexthop
                #
                # but today we display via a single line
                #     neighbor swp1 interface remote-as external
                #
                # and capability extended-nexthop is no longer needed because we
                # automatically enable it when the neighbor is of type interface.
                #
                # This change confuses frr-reload.py so check to see if we are deleting
                #     neighbor swp1 interface remote-as (external|internal|ASNUM)
                #
                # and adding
                #     neighbor swp1 interface
                #     neighbor swp1 remote-as (external|internal|ASNUM)
                #     neighbor swp1 capability extended-nexthop
                #
                # If so then chop the del line and the corresponding add lines
                re_swpx_int_remoteas = re.search(
                    "neighbor (\S+) interface remote-as (\S+)", line
                )
                re_swpx_int_v6only_remoteas = re.search(
                    "neighbor (\S+) interface v6only remote-as (\S+)", line
                )

                if re_swpx_int_remoteas or re_swpx_int_v6only_remoteas:
                    swpx_interface = None
                    swpx_remoteas = None

                    if re_swpx_int_remoteas:
                        swpx = re_swpx_int_remoteas.group(1)
                        remoteas = re_swpx_int_remoteas.group(2)
                        swpx_interface = "neighbor %s interface" % swpx
                    elif re_swpx_int_v6only_remoteas:
                        swpx = re_swpx_int_v6only_remoteas.group(1)
                        remoteas = re_swpx_int_v6only_remoteas.group(2)
                        swpx_interface = "neighbor %s interface v6only" % swpx

                    swpx_remoteas = "neighbor %s remote-as %s" % (swpx, remoteas)
                    found_add_swpx_interface = line_exist(
                        lines_to_add, ctx_keys, swpx_interface
                    )
                    found_add_swpx_remoteas = line_exist(
                        lines_to_add, ctx_keys, swpx_remoteas
                    )
                    tmp_ctx_keys = tuple(list(ctx_keys))

                    if found_add_swpx_interface and found_add_swpx_remoteas:
                        deleted = True
                        lines_to_del_to_del.append((ctx_keys, line))
                        lines_to_add_to_del.append((ctx_keys, swpx_interface))
                        lines_to_add_to_del.append((tmp_ctx_keys, swpx_remoteas))

            # We made the 'bgp bestpath as-path multipath-relax' command
            # automatically assume 'no-as-set' since the lack of this option
            # caused weird routing problems. When the running config is shown
            # in releases with this change, the no-as-set keyword is not shown
            # as it is the default. This causes frr-reload to unnecessarily
            # unapply this option only to apply it back again, causing
            # unnecessary session resets.
            if "multipath-relax" in line:
                re_asrelax_new = re.search(
                    "^bgp\s+bestpath\s+as-path\s+multipath-relax$", line
                )
                old_asrelax_cmd = "bgp bestpath as-path multipath-relax no-as-set"
                found_asrelax_old = line_exist(lines_to_add, ctx_keys, old_asrelax_cmd)

                if re_asrelax_new and found_asrelax_old:
                    deleted = True
                    lines_to_del_to_del.append((ctx_keys, line))
                    lines_to_add_to_del.append((ctx_keys, old_asrelax_cmd))

            # If we are modifying the BGP table-map we need to avoid a del/add
            # and instead modify the table-map in place via an add.  This is
            # needed to avoid installing all routes in the RIB the second the
            # 'no table-map' is issued.
            if line.startswith("table-map"):
                found_table_map = line_exist(lines_to_add, ctx_keys, "table-map", False)

                if found_table_map:
                    lines_to_del_to_del.append((ctx_keys, line))

        # More old-to-new config handling. ip import-table no longer accepts
        # distance, but we honor the old syntax. But 'show running' shows only
        # the new syntax. This causes an unnecessary 'no import-table' followed
        # by the same old 'ip import-table' which causes perturbations in
        # announced routes leading to traffic blackholes. Fix this issue.
        re_importtbl = re.search("^ip\s+import-table\s+(\d+)$", ctx_keys[0])
        if re_importtbl:
            table_num = re_importtbl.group(1)
            for ctx in lines_to_add:
                if ctx[0][0].startswith("ip import-table %s distance" % table_num):
                    lines_to_del_to_del.append(
                        (("ip import-table %s" % table_num,), None)
                    )
                    lines_to_add_to_del.append((ctx[0], None))

        # ip/ipv6 prefix-lists and access-lists can be specified without a seq
        # number.  However, the running config always adds 'seq x', where x is
        # a number incremented by 5 for every element of the prefix/access
        # list.  So, ignore such lines as well. Sample prefix-list and
        # acces-list lines:
        #      ip prefix-list PR-TABLE-2 seq 5 permit 20.8.2.0/24 le 32
        #      ip prefix-list PR-TABLE-2 seq 10 permit 20.8.2.0/24 le 32
        #      ipv6 prefix-list vrfdev6-12 permit 2000:9:2::/64 gt 64
        #      access-list FOO seq 5 permit 2.2.2.2/32
        #      ipv6 access-list BAR seq 5 permit 2:2:2::2/128
        re_acl_pfxlst = re.search(
            "^(ip |ipv6 |)(prefix-list|access-list)(\s+\S+\s+)(seq \d+\s+)(permit|deny)(.*)$",
            ctx_keys[0],
        )
        if re_acl_pfxlst:
            found = False
            tmpline = (
                re_acl_pfxlst.group(1)
                + re_acl_pfxlst.group(2)
                + re_acl_pfxlst.group(3)
                + re_acl_pfxlst.group(5)
                + re_acl_pfxlst.group(6)
            )
            for ctx in lines_to_add:
                if ctx[0][0] == tmpline:
                    lines_to_del_to_del.append((ctx_keys, None))
                    lines_to_add_to_del.append(((tmpline,), None))
                    found = True
            # If prefix-lists or access-lists are being deleted and not added
            # (see comment above), add command with 'no' to lines_to_add and
            # remove from lines_to_del to improve scaling performance.
            if found is False:
                add_cmd = ("no " + ctx_keys[0],)
                lines_to_add.append((add_cmd, None))
                lines_to_del_to_del.append((ctx_keys, None))

        # bgp community-list, large-community-list, extcommunity-list can be
        # specified without a seq number. However, the running config always
        # adds `seq X` (sequence number). So, ignore such lines as well.
        # Examples:
        #      bgp community-list standard clist seq 5 permit 222:213
        #      bgp large-community-list standard llist seq 5 permit 65001:65001:1
        #      bgp extcommunity-list standard elist seq 5 permit soo 123:123
        re_bgp_lists = re.search(
            "^(bgp )(community-list|large-community-list|extcommunity-list)(\s+\S+\s+)(\S+\s+)(seq \d+\s+)(permit|deny)(.*)$",
            ctx_keys[0],
        )
        if re_bgp_lists:
            found = False
            tmpline = (
                re_bgp_lists.group(1)
                + re_bgp_lists.group(2)
                + re_bgp_lists.group(3)
                + re_bgp_lists.group(4)
                + re_bgp_lists.group(6)
                + re_bgp_lists.group(7)
            )
            for ctx in lines_to_add:
                if ctx[0][0] == tmpline:
                    lines_to_del_to_del.append((ctx_keys, None))
                    lines_to_add_to_del.append(((tmpline,), None))
                    found = True
            if found is False:
                add_cmd = ("no " + ctx_keys[0],)
                lines_to_add.append((add_cmd, None))
                lines_to_del_to_del.append((ctx_keys, None))

        # bgp as-path access-list can be specified without a seq number.
        # However, the running config always
        # adds `seq X` (sequence number). So, ignore such lines as well.
        # Examples:
        #      bgp as-path access-list important_internet_bgp_as_numbers seq 30 permit _40841_"
        re_bgp_as_path = re.search(
            "^(bgp )(as-path )(access-list )(\S+\s+)(seq \d+\s+)(permit|deny)(.*)$",
            ctx_keys[0],
        )
        if re_bgp_as_path:
            found = False
            tmpline = (
                re_bgp_as_path.group(1)
                + re_bgp_as_path.group(2)
                + re_bgp_as_path.group(3)
                + re_bgp_as_path.group(4)
                + re_bgp_as_path.group(6)
                + re_bgp_as_path.group(7)
            )
            for ctx in lines_to_add:
                if ctx[0][0] == tmpline:
                    lines_to_del_to_del.append((ctx_keys, None))
                    lines_to_add_to_del.append(((tmpline,), None))
                    found = True
            if found is False:
                add_cmd = ("no " + ctx_keys[0],)
                lines_to_add.append((add_cmd, None))
                lines_to_del_to_del.append((ctx_keys, None))

        if (
            len(ctx_keys) == 3
            and ctx_keys[0].startswith("router bgp")
            and ctx_keys[1] == "address-family l2vpn evpn"
            and ctx_keys[2].startswith("vni")
        ):
            re_route_target = (
                re.search("^route-target import (.*)$", line)
                if line is not None
                else False
            )

            if re_route_target:
                rt = re_route_target.group(1).strip()
                route_target_import_line = line
                route_target_export_line = "route-target export %s" % rt
                route_target_both_line = "route-target both %s" % rt

                found_route_target_export_line = line_exist(
                    lines_to_del, ctx_keys, route_target_export_line
                )
                found_route_target_both_line = line_exist(
                    lines_to_add, ctx_keys, route_target_both_line
                )

                # If the running configs has
                #     route-target import 1:1
                #     route-target export 1:1
                # and the config we are reloading against has
                #     route-target both 1:1
                # then we can ignore deleting the import/export and ignore adding the 'both'
                if found_route_target_export_line and found_route_target_both_line:
                    lines_to_del_to_del.append((ctx_keys, route_target_import_line))
                    lines_to_del_to_del.append((ctx_keys, route_target_export_line))
                    lines_to_add_to_del.append((ctx_keys, route_target_both_line))

        # Deleting static routes under a vrf can lead to time-outs if each is sent
        # as separate vtysh -c commands. Change them from being in lines_to_del and
        # put the "no" form in lines_to_add
        if ctx_keys[0].startswith("vrf ") and line:
            if line.startswith("ip route") or line.startswith("ipv6 route"):
                add_cmd = "no " + line
                lines_to_add.append((ctx_keys, add_cmd))
                lines_to_del_to_del.append((ctx_keys, line))

        if not deleted:
            found_add_line = line_exist(lines_to_add, ctx_keys, line)

            if found_add_line:
                lines_to_del_to_del.append((ctx_keys, line))
                lines_to_add_to_del.append((ctx_keys, line))
            else:
                # We have commands that used to be displayed in the global part
                # of 'router bgp' that are now displayed under 'address-family ipv4 unicast'
                #
                # # old way
                # router bgp 64900
                #   neighbor ISL advertisement-interval 0
                #
                # vs.
                #
                # # new way
                # router bgp 64900
                #   address-family ipv4 unicast
                #     neighbor ISL advertisement-interval 0
                #
                # Look to see if we are deleting it in one format just to add it back in the other
                if (
                    ctx_keys[0].startswith("router bgp")
                    and len(ctx_keys) > 1
                    and ctx_keys[1] == "address-family ipv4 unicast"
                ):
                    tmp_ctx_keys = list(ctx_keys)[:-1]
                    tmp_ctx_keys = tuple(tmp_ctx_keys)

                    found_add_line = line_exist(lines_to_add, tmp_ctx_keys, line)

                    if found_add_line:
                        lines_to_del_to_del.append((ctx_keys, line))
                        lines_to_add_to_del.append((tmp_ctx_keys, line))

    for ctx_keys, line in lines_to_del_to_del:
        try:
            lines_to_del.remove((ctx_keys, line))
        except ValueError:
            pass

    for ctx_keys, line in lines_to_add_to_del:
        try:
            lines_to_add.remove((ctx_keys, line))
        except ValueError:
            pass

    return (lines_to_add, lines_to_del)


def ignore_unconfigurable_lines(lines_to_add, lines_to_del):
    """
    There are certain commands that cannot be removed.  Remove
    those commands from lines_to_del.
    """
    lines_to_del_to_del = []

    for ctx_keys, line in lines_to_del:
        # The integrated-vtysh-config one is technically "no"able but if we did
        # so frr-reload would stop working so do not let the user shoot
        # themselves in the foot by removing this.
        if any(
            [
                ctx_keys[0].startswith(x)
                for x in [
                    "agentx",
                    "frr version",
                    "frr defaults",
                    "username",
                    "password",
                    "line vty",
                    "service integrated-vtysh-config",
                ]
            ]
        ):
            log.info('"%s" cannot be removed' % (ctx_keys[-1],))
            lines_to_del_to_del.append((ctx_keys, line))

    for ctx_keys, line in lines_to_del_to_del:
        lines_to_del.remove((ctx_keys, line))

    return (lines_to_add, lines_to_del)


def compare_context_objects(newconf, running):
    """
    Create a context diff for the two specified contexts
    """

    # Compare the two Config objects to find the lines that we need to add/del
    lines_to_add = []
    lines_to_del = []
    pollist_to_del = []
    seglist_to_del = []
    pceconf_to_del = []
    pcclist_to_del = []
    candidates_to_add = []
    delete_bgpd = False
    area_stub_no_sum = "area (\S+) stub no-summary"
    deleted_keychains = []

    # Find contexts that are in newconf but not in running
    # Find contexts that are in running but not in newconf
    for running_ctx_keys, running_ctx in iteritems(running.contexts):
        if running_ctx_keys in newconf.contexts:
            newconf_ctx = newconf.contexts[running_ctx_keys]

            for line in running_ctx.lines:
                # ospf area <> stub no-summary line removal requires
                # to remoe area <> stub as no form of original
                # retains the stub form.
                # lines_to_del will contain:
                #   no area <x> stub no-summary and
                #   no area <x> stub
                if (
                    running_ctx_keys[0].startswith("router ospf")
                    and line not in newconf_ctx.dlines
                ):
                    re_area_stub_no_sum = re.search(area_stub_no_sum, line)
                    if re_area_stub_no_sum:
                        new_del_line = "area %s stub" % re_area_stub_no_sum.group(1)
                        lines_to_del.append((running_ctx_keys, new_del_line))

        if running_ctx_keys not in newconf.contexts:
            # We check that the len is 1 here so that we only look at ('router bgp 10')
            # and not ('router bgp 10', 'address-family ipv4 unicast'). The
            # latter could cause a false delete_bgpd positive if ipv4 unicast is in
            # running but not in newconf.
            if "router bgp" in running_ctx_keys[0] and len(running_ctx_keys) == 1:
                delete_bgpd = True
                lines_to_del.append((running_ctx_keys, None))

            # We cannot do 'no interface' or 'no vrf' in FRR, and so deal with it
            elif running_ctx_keys[0].startswith("interface") or running_ctx_keys[
                0
            ].startswith("vrf"):
                for line in running_ctx.lines:
                    lines_to_del.append((running_ctx_keys, line))

            # If this is an address-family under 'router bgp' and we are already deleting the
            # entire 'router bgp' context then ignore this sub-context
            elif (
                "router bgp" in running_ctx_keys[0]
                and len(running_ctx_keys) > 1
                and delete_bgpd
            ):
                continue

            # Check if key chain is being deleted:
            # - If it is being deleted then avoid deleting its contexts
            # - Else delete its configuration without removing the root node
            elif (
                running_ctx_keys[0].startswith("key chain ")
                and len(running_ctx_keys) == 1
            ):
                deleted_keychains.append(running_ctx_keys[0])
                lines_to_del.append((running_ctx_keys, None))
            elif (
                running_ctx_keys[0].startswith("key chain ")
                and len(running_ctx_keys) > 1
                and running_ctx_keys[0] in deleted_keychains
            ):
                continue

            # Delete an entire vni sub-context under "address-family l2vpn evpn"
            elif (
                "router bgp" in running_ctx_keys[0]
                and len(running_ctx_keys) > 2
                and running_ctx_keys[1].startswith("address-family l2vpn evpn")
                and running_ctx_keys[2].startswith("vni ")
            ):
                lines_to_del.append((running_ctx_keys, None))

            elif (
                "router bgp" in running_ctx_keys[0]
                and len(running_ctx_keys) > 1
                and running_ctx_keys[1].startswith("address-family")
            ):
                # There's no 'no address-family' support and so we have to
                # delete each line individually again
                for line in running_ctx.lines:
                    lines_to_del.append((running_ctx_keys, line))

            # Some commands can happen at higher counts that make
            # doing vtysh -c inefficient (and can time out.)  For
            # these commands, instead of adding them to lines_to_del,
            # add the "no " version to lines_to_add.
            elif running_ctx_keys[0].startswith("ip route") or running_ctx_keys[
                0
            ].startswith("ipv6 route"):
                add_cmd = ("no " + running_ctx_keys[0],)
                lines_to_add.append((add_cmd, None))

            # if this an interface sub-subcontext in an address-family block in ldpd and
            # we are already deleting the whole context, then ignore this
            elif (
                len(running_ctx_keys) > 2
                and running_ctx_keys[0].startswith("mpls ldp")
                and running_ctx_keys[1].startswith("address-family")
                and (running_ctx_keys[:2], None) in lines_to_del
            ):
                continue

            # same thing for a pseudowire sub-context inside an l2vpn context
            elif (
                len(running_ctx_keys) > 1
                and running_ctx_keys[0].startswith("l2vpn")
                and running_ctx_keys[1].startswith("member pseudowire")
                and (running_ctx_keys[:1], None) in lines_to_del
            ):
                continue

            # Segment routing and traffic engineering never need to be deleted
            elif (
                running_ctx_keys[0].startswith("segment-routing")
                and len(running_ctx_keys) < 3
            ):
                continue

            # Neither the pcep command
            elif (
                len(running_ctx_keys) == 3
                and running_ctx_keys[0].startswith("segment-routing")
                and running_ctx_keys[2].startswith("pcep")
            ):
                continue

            # Segment lists can only be deleted after we removed all the candidate paths that
            # use them, so add them to a separate array that is going to be appended at the end
            elif (
                len(running_ctx_keys) == 3
                and running_ctx_keys[0].startswith("segment-routing")
                and running_ctx_keys[2].startswith("segment-list")
            ):
                seglist_to_del.append((running_ctx_keys, None))

            # Policies must be deleted after there candidate path, to be sure
            # we add them to a separate array that is going to be appended at the end
            elif (
                len(running_ctx_keys) == 3
                and running_ctx_keys[0].startswith("segment-routing")
                and running_ctx_keys[2].startswith("policy")
            ):
                pollist_to_del.append((running_ctx_keys, None))

            # pce-config must be deleted after the pce, to be sure we add them
            # to a separate array that is going to be appended at the end
            elif (
                len(running_ctx_keys) >= 4
                and running_ctx_keys[0].startswith("segment-routing")
                and running_ctx_keys[3].startswith("pce-config")
            ):
                pceconf_to_del.append((running_ctx_keys, None))

            # pcc must be deleted after the pce and pce-config too
            elif (
                len(running_ctx_keys) >= 4
                and running_ctx_keys[0].startswith("segment-routing")
                and running_ctx_keys[3].startswith("pcc")
            ):
                pcclist_to_del.append((running_ctx_keys, None))

            # Non-global context
            elif running_ctx_keys and not any(
                "address-family" in key for key in running_ctx_keys
            ):
                lines_to_del.append((running_ctx_keys, None))

            elif running_ctx_keys and not any("vni" in key for key in running_ctx_keys):
                lines_to_del.append((running_ctx_keys, None))

            # Global context
            else:
                for line in running_ctx.lines:
                    lines_to_del.append((running_ctx_keys, line))

    # if we have some policies commands to delete, append them to lines_to_del
    if len(pollist_to_del) > 0:
        lines_to_del.extend(pollist_to_del)

    # if we have some segment list commands to delete, append them to lines_to_del
    if len(seglist_to_del) > 0:
        lines_to_del.extend(seglist_to_del)

    # if we have some pce list commands to delete, append them to lines_to_del
    if len(pceconf_to_del) > 0:
        lines_to_del.extend(pceconf_to_del)

    # if we have some pcc list commands to delete, append them to lines_to_del
    if len(pcclist_to_del) > 0:
        lines_to_del.extend(pcclist_to_del)

    # Find the lines within each context to add
    # Find the lines within each context to del
    for newconf_ctx_keys, newconf_ctx in iteritems(newconf.contexts):
        if newconf_ctx_keys in running.contexts:
            running_ctx = running.contexts[newconf_ctx_keys]

            for line in newconf_ctx.lines:
                if line not in running_ctx.dlines:
                    # candidate paths can only be added after the policy and segment list,
                    # so add them to a separate array that is going to be appended at the end
                    if (
                        len(newconf_ctx_keys) == 3
                        and newconf_ctx_keys[0].startswith("segment-routing")
                        and newconf_ctx_keys[2].startswith("policy ")
                        and line.startswith("candidate-path ")
                    ):
                        candidates_to_add.append((newconf_ctx_keys, line))

                    else:
                        lines_to_add.append((newconf_ctx_keys, line))

            for line in running_ctx.lines:
                if line not in newconf_ctx.dlines:
                    lines_to_del.append((newconf_ctx_keys, line))

    for newconf_ctx_keys, newconf_ctx in iteritems(newconf.contexts):
        if newconf_ctx_keys not in running.contexts:
            # candidate paths can only be added after the policy and segment list,
            # so add them to a separate array that is going to be appended at the end
            if (
                len(newconf_ctx_keys) == 4
                and newconf_ctx_keys[0].startswith("segment-routing")
                and newconf_ctx_keys[3].startswith("candidate-path")
            ):
                candidates_to_add.append((newconf_ctx_keys, None))
                for line in newconf_ctx.lines:
                    candidates_to_add.append((newconf_ctx_keys, line))

            else:
                lines_to_add.append((newconf_ctx_keys, None))

                for line in newconf_ctx.lines:
                    lines_to_add.append((newconf_ctx_keys, line))

    # if we have some candidate paths commands to add, append them to lines_to_add
    if len(candidates_to_add) > 0:
        lines_to_add.extend(candidates_to_add)

    (lines_to_add, lines_to_del) = ignore_delete_re_add_lines(
        lines_to_add, lines_to_del
    )
    (lines_to_add, lines_to_del) = delete_move_lines(lines_to_add, lines_to_del)
    (lines_to_add, lines_to_del) = ignore_unconfigurable_lines(
        lines_to_add, lines_to_del
    )

    return (lines_to_add, lines_to_del)


if __name__ == "__main__":
    # Command line options
    parser = argparse.ArgumentParser(
        description="Dynamically apply diff in frr configs"
    )
    parser.add_argument(
        "--input", help='Read running config from file instead of "show running"'
    )
    group = parser.add_mutually_exclusive_group(required=True)
    group.add_argument(
        "--reload", action="store_true", help="Apply the deltas", default=False
    )
    group.add_argument(
        "--test", action="store_true", help="Show the deltas", default=False
    )
    level_group = parser.add_mutually_exclusive_group()
    level_group.add_argument(
        "--debug",
        action="store_true",
        help="Enable debugs (synonym for --log-level=debug)",
        default=False,
    )
    level_group.add_argument(
        "--log-level",
        help="Log level",
        default="info",
        choices=("critical", "error", "warning", "info", "debug"),
    )
    parser.add_argument(
        "--stdout", action="store_true", help="Log to STDOUT", default=False
    )
    parser.add_argument(
        "--pathspace",
        "-N",
        metavar="NAME",
        help="Reload specified path/namespace",
        default=None,
    )
    parser.add_argument("filename", help="Location of new frr config file")
    parser.add_argument(
        "--overwrite",
        action="store_true",
        help="Overwrite frr.conf with running config output",
        default=False,
    )
    parser.add_argument(
        "--bindir", help="path to the vtysh executable", default="/usr/bin"
    )
    parser.add_argument(
        "--confdir", help="path to the daemon config files", default="/etc/frr"
    )
    parser.add_argument(
        "--rundir", help="path for the temp config file", default="/var/run/frr"
    )
    parser.add_argument(
        "--vty_socket",
        help="socket to be used by vtysh to connect to the daemons",
        default=None,
    )
    parser.add_argument(
        "--daemon", help="daemon for which want to replace the config", default=""
    )
    parser.add_argument(
        "--test-reset",
        action="store_true",
        help="Used by topotest to not delete debug or log file commands",
    )

    args = parser.parse_args()

    # Logging
    # For --test log to stdout
    # For --reload log to /var/log/frr/frr-reload.log
    if args.test or args.stdout:
        logging.basicConfig(format="%(asctime)s %(levelname)5s: %(message)s")

        # Color the errors and warnings in red
        logging.addLevelName(
            logging.ERROR, "\033[91m  %s\033[0m" % logging.getLevelName(logging.ERROR)
        )
        logging.addLevelName(
            logging.WARNING, "\033[91m%s\033[0m" % logging.getLevelName(logging.WARNING)
        )

    elif args.reload:
        if not os.path.isdir("/var/log/frr/"):
            os.makedirs("/var/log/frr/", mode=0o0755)

        logging.basicConfig(
            filename="/var/log/frr/frr-reload.log",
            format="%(asctime)s %(levelname)5s: %(message)s",
        )

    # argparse should prevent this from happening but just to be safe...
    else:
        raise Exception("Must specify --reload or --test")
    log = logging.getLogger(__name__)

    if args.debug:
        log.setLevel(logging.DEBUG)
    else:
        log.setLevel(args.log_level.upper())

    if args.reload and not args.stdout:
        # Additionally send errors and above to STDOUT, with no metadata,
        # when we are logging to a file. This specifically does not follow
        # args.log_level, and is analagous to behaviour in earlier versions
        # which additionally logged most errors using print().

        stdout_hdlr = logging.StreamHandler(sys.stdout)
        stdout_hdlr.setLevel(logging.ERROR)
        stdout_hdlr.setFormatter(logging.Formatter())
        log.addHandler(stdout_hdlr)

    # Verify the new config file is valid
    if not os.path.isfile(args.filename):
        log.error("Filename %s does not exist" % args.filename)
        sys.exit(1)

    if not os.path.getsize(args.filename):
        log.error("Filename %s is an empty file" % args.filename)
        sys.exit(1)

    # Verify that confdir is correct
    if not os.path.isdir(args.confdir):
        log.error("Confdir %s is not a valid path" % args.confdir)
        sys.exit(1)

    # Verify that bindir is correct
    if not os.path.isdir(args.bindir) or not os.path.isfile(args.bindir + "/vtysh"):
        log.error("Bindir %s is not a valid path to vtysh" % args.bindir)
        sys.exit(1)

    # verify that the vty_socket, if specified, is valid
    if args.vty_socket and not os.path.isdir(args.vty_socket):
        log.error("vty_socket %s is not a valid path" % args.vty_socket)
        sys.exit(1)

    # verify that the daemon, if specified, is valid
    if args.daemon and args.daemon not in [
        "zebra",
        "bgpd",
        "fabricd",
        "isisd",
        "babeld",
        "ospf6d",
        "ospfd",
        "pbrd",
        "pimd",
        "pim6d",
        "ripd",
        "ripngd",
        "sharpd",
        "staticd",
        "vrrpd",
        "ldpd",
        "nhrpd",
        "pathd",
        "bfdd",
        "eigrpd",
    ]:
        msg = "Daemon %s is not a valid option for 'show running-config'" % args.daemon
        print(msg)
        log.error(msg)
        sys.exit(1)

    vtysh = Vtysh(args.bindir, args.confdir, args.vty_socket, args.pathspace)

    # Verify that 'service integrated-vtysh-config' is configured
    if args.pathspace:
        vtysh_filename = args.confdir + "/" + args.pathspace + "/vtysh.conf"
    else:
        vtysh_filename = args.confdir + "/vtysh.conf"
    service_integrated_vtysh_config = True

    if os.path.isfile(vtysh_filename):
        with open(vtysh_filename, "r") as fh:
            for line in fh.readlines():
                line = line.strip()

                if line == "no service integrated-vtysh-config":
                    service_integrated_vtysh_config = False
                    break

    if not args.test and not service_integrated_vtysh_config and not args.daemon:
        log.error(
            "'service integrated-vtysh-config' is not configured, this is required for 'service frr reload'"
        )
        sys.exit(1)

    log.info('Called via "%s"', str(args))

    # Create a Config object from the config generated by newconf
    newconf = Config(vtysh)
    try:
        newconf.load_from_file(args.filename)
        reload_ok = True
    except VtyshException as ve:
        log.error("vtysh failed to process new configuration: {}".format(ve))
        reload_ok = False

    if args.test:
        # Create a Config object from the running config
        running = Config(vtysh)

        if args.input:
            running.load_from_file(args.input)
        else:
            running.load_from_show_running(args.daemon)

        (lines_to_add, lines_to_del) = compare_context_objects(newconf, running)

        if lines_to_del:
            if not args.test_reset:
                print("\nLines To Delete")
                print("===============")

            for ctx_keys, line in lines_to_del:
                if line == "!":
                    continue

                nolines = lines_to_config(ctx_keys, line, True)

                if args.test_reset:
                    # For topotests the original code stripped the lines, and ommitted blank lines
                    # after, do that here
                    nolines = [x.strip() for x in nolines]
                    # For topotests leave these lines in (don't delete them)
                    # [chopps: why is "log file" more special than other "log" commands?]
                    nolines = [
                        x for x in nolines if "debug" not in x and "log file" not in x
                    ]
                    if not nolines:
                        continue

                cmd = "\n".join(nolines)
                print(cmd)

        if lines_to_add:
            if not args.test_reset:
                print("\nLines To Add")
                print("============")

            for ctx_keys, line in lines_to_add:
                if line == "!":
                    continue

                lines = lines_to_config(ctx_keys, line, False)

                if args.test_reset:
                    # For topotests the original code stripped the lines, and ommitted blank lines
                    # after, do that here
                    lines = [x.strip() for x in lines if x.strip()]
                    if not lines:
                        continue

                cmd = "\n".join(lines)
                print(cmd)

    elif args.reload:
        lines_to_configure = []

        # We will not be able to do anything, go ahead and exit(1)
        if not vtysh.is_config_available() or not reload_ok:
            sys.exit(1)

        log.debug("New Frr Config\n%s", newconf.get_lines())

        # This looks a little odd but we have to do this twice...here is why
        # If the user had this running bgp config:
        #
        # router bgp 10
        #  neighbor 1.1.1.1 remote-as 50
        #  neighbor 1.1.1.1 route-map FOO out
        #
        # and this config in the newconf config file
        #
        # router bgp 10
        #  neighbor 1.1.1.1 remote-as 999
        #  neighbor 1.1.1.1 route-map FOO out
        #
        #
        # Then the script will do
        # - no neighbor 1.1.1.1 remote-as 50
        # - neighbor 1.1.1.1 remote-as 999
        #
        # The problem is the "no neighbor 1.1.1.1 remote-as 50" will also remove
        # the "neighbor 1.1.1.1 route-map FOO out" line...so we compare the
        # configs again to put this line back.

        # There are many keywords in FRR that can only appear one time under
        # a context, take "bgp router-id" for example. If the config that we are
        # reloading against has the following:
        #
        # router bgp 10
        #   bgp router-id 1.1.1.1
        #   bgp router-id 2.2.2.2
        #
        # The final config needs to contain "bgp router-id 2.2.2.2". On the
        # first pass we will add "bgp router-id 2.2.2.2" but then on the second
        # pass we will see that "bgp router-id 1.1.1.1" is missing and add that
        # back which cancels out the "bgp router-id 2.2.2.2". The fix is for the
        # second pass to include all of the "adds" from the first pass.
        lines_to_add_first_pass = []

        for x in range(2):
            running = Config(vtysh)
            running.load_from_show_running(args.daemon)
            log.debug("Running Frr Config (Pass #%d)\n%s", x, running.get_lines())

            (lines_to_add, lines_to_del) = compare_context_objects(newconf, running)

            if x == 0:
                lines_to_add_first_pass = lines_to_add
            else:
                lines_to_add.extend(lines_to_add_first_pass)

            # Only do deletes on the first pass. The reason being if we
            # configure a bgp neighbor via "neighbor swp1 interface" FRR
            # will automatically add:
            #
            # interface swp1
            #  ipv6 nd ra-interval 10
            #  no ipv6 nd suppress-ra
            # !
            #
            # but those lines aren't in the config we are reloading against so
            # on the 2nd pass they will show up in lines_to_del.  This could
            # apply to other scenarios as well where configuring FOO adds BAR
            # to the config.
            if lines_to_del and x == 0:
                for ctx_keys, line in lines_to_del:
                    if line == "!":
                        continue

                    # 'no' commands are tricky, we can't just put them in a file and
                    # vtysh -f that file. See the next comment for an explanation
                    # of their quirks
                    cmd = lines_to_config(ctx_keys, line, True)
                    original_cmd = cmd

                    # Some commands in frr are picky about taking a "no" of the entire line.
                    # OSPF is bad about this, you can't "no" the entire line, you have to "no"
                    # only the beginning. If we hit one of these command an exception will be
                    # thrown.  Catch it and remove the last '-c', 'FOO' from cmd and try again.
                    #
                    # Example:
                    # frr(config-if)# ip ospf authentication message-digest 1.1.1.1
                    # frr(config-if)# no ip ospf authentication message-digest 1.1.1.1
                    #  % Unknown command.
                    # frr(config-if)# no ip ospf authentication message-digest
                    #  % Unknown command.
                    # frr(config-if)# no ip ospf authentication
                    # frr(config-if)#

                    stdouts = []
                    while True:
                        try:
                            vtysh(["configure"] + cmd, stdouts)

                        except VtyshException:
                            # - Pull the last entry from cmd (this would be
                            #   'no ip ospf authentication message-digest 1.1.1.1' in
                            #   our example above
                            # - Split that last entry by whitespace and drop the last word
                            log.error("Failed to execute %s", " ".join(cmd))
                            last_arg = cmd[-1].split(" ")

                            if len(last_arg) <= 2:
                                log.error(
                                    '"%s" we failed to remove this command',
                                    " -- ".join(original_cmd),
                                )
                                # Log first error msg for original_cmd
                                if stdouts:
                                    log.error(stdouts[0])
                                reload_ok = False
                                break

                            new_last_arg = last_arg[0:-1]
                            cmd[-1] = " ".join(new_last_arg)
                        else:
                            log.info('Executed "%s"', " ".join(cmd))
                            break

            if lines_to_add:
                lines_to_configure = []

                for ctx_keys, line in lines_to_add:
                    if line == "!":
                        continue

                    # Don't run "no" commands twice since they can error
                    # out the second time due to first deletion
                    if x == 1 and ctx_keys[0].startswith("no "):
                        continue

                    cmd = "\n".join(lines_to_config(ctx_keys, line, False)) + "\n"
                    lines_to_configure.append(cmd)

                if lines_to_configure:
                    random_string = "".join(
                        random.SystemRandom().choice(
                            string.ascii_uppercase + string.digits
                        )
                        for _ in range(6)
                    )

                    filename = args.rundir + "/reload-%s.txt" % random_string
                    log.info("%s content\n%s" % (filename, pformat(lines_to_configure)))

                    with open(filename, "w") as fh:
                        for line in lines_to_configure:
                            fh.write(line + "\n")

                    try:
                        vtysh.exec_file(filename)
                    except VtyshException as e:
                        log.warning("frr-reload.py failed due to\n%s" % e.args)
                        reload_ok = False
                    os.unlink(filename)

        # Make these changes persistent
        target = str(args.confdir + "/frr.conf")
        if args.overwrite or (not args.daemon and args.filename != target):
            vtysh("write")

    if not reload_ok:
        sys.exit(1)