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path: root/morphlib/exts/simple-network.configure
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#!/usr/bin/python
# Copyright (C) 2013,2015  Codethink Limited
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program.  If not, see <http://www.gnu.org/licenses/>.

'''A Morph deployment configuration extension to handle network configutation

This extension prepares /etc/network/interfaces and networkd .network files
in /etc/systemd/network/ with the interfaces specified during deployment.

If no network configuration is provided, eth0 will be configured for DHCP
with the hostname of the system in the case of /etc/network/interfaces.
In the case of networkd, any interface starting by e* will be configured
for DHCP
'''


import os
import sys
import cliapp

import morphlib


class SimpleNetworkError(morphlib.Error):
    '''Errors associated with simple network setup'''
    pass


class SimpleNetworkConfigurationExtension(cliapp.Application):
    '''Configure /etc/network/interfaces and generate networkd .network files

    Reading NETWORK_CONFIG, this extension sets up /etc/network/interfaces
    and .network files in /etc/systemd/network/.
    '''

    def process_args(self, args):
        network_config = os.environ.get("NETWORK_CONFIG")

        self.rename_networkd_chunk_file(args)

        if network_config is None:
            self.generate_default_network_config(args)
        else:
            self.status(msg="Processing NETWORK_CONFIG=%(nc)s",
                        nc=network_config)

            stanzas = self.parse_network_stanzas(network_config)

            self.generate_interfaces_file(args, stanzas)
            self.generate_networkd_files(args, stanzas)

    def rename_networkd_chunk_file(self, args):
        """Rename the 10-dchp.network file generated in the systemd chunk

        The systemd chunk will place something in 10-dhcp.network, which will
        have higher precedence than anything added in this extension (we
        start at 50-*).

        We should check for that file and rename it instead remove it in
        case the file is being used by the user.

        Until both the following happen, we should continue to rename that
        default config file:

        1.  simple-network.configure is always run when systemd is included
        2.  We've been building systems without systemd including that default
            networkd config for long enough that nobody should be including
            that config file.
        """
        file_path = os.path.join(args[0], "etc", "systemd", "network",
                                 "10-dhcp.network")
        try:
            os.rename(file_path, file_path + ".morph")
            self.status(msg="Renaming networkd file from systemd chunk: %(f)s \
                        to %(f)s.morph", f=file_path)
        except OSError:
            pass

    def generate_default_network_config(self, args):
        """Generate default network config: DHCP in all the interfaces"""

        default_network_config_interfaces = "lo:loopback;" \
                                            "eth0:dhcp,hostname=$(hostname)"
        default_network_config_networkd = "e*:dhcp"

        stanzas_interfaces = self.parse_network_stanzas(
            default_network_config_interfaces)
        stanzas_networkd = self.parse_network_stanzas(
            default_network_config_networkd)

        self.generate_interfaces_file(args, stanzas_interfaces)
        self.generate_networkd_files(args, stanzas_networkd)

    def generate_interfaces_file(self, args, stanzas):
        """Generate /etc/network/interfaces file"""

        iface_file = self.generate_iface_file(stanzas)
        with open(os.path.join(args[0], "etc/network/interfaces"), "w") as f:
            f.write(iface_file)

    def generate_iface_file(self, stanzas):
        """Generate an interfaces file from the provided stanzas.

        The interfaces will be sorted by name, with loopback sorted first.
        """

        def cmp_iface_names(a, b):
            a = a['name']
            b = b['name']
            if a == "lo":
                return -1
            elif b == "lo":
                return 1
            else:
                return cmp(a,b)

        return "\n".join(self.generate_iface_stanza(stanza)
                         for stanza in sorted(stanzas, cmp=cmp_iface_names))

    def generate_iface_stanza(self, stanza):
        """Generate an interfaces stanza from the provided data."""

        name = stanza['name']
        itype = stanza['type']
        lines  = ["auto %s" % name, "iface %s inet %s" % (name, itype)]
        lines += ["    %s %s" % elem for elem in stanza['args'].items()]
        lines += [""]
        return "\n".join(lines)

    def generate_networkd_files(self, args, stanzas):
        """Generate .network files"""

        for i, stanza in enumerate(stanzas, 50):
            iface_file = self.generate_networkd_file(stanza)

            if iface_file is None:
                continue

            path = os.path.join(args[0], "etc", "systemd", "network",
                                "%s-%s.network" % (i, stanza['name']))

            with open(path, "w") as f:
                f.write(iface_file)

    def generate_networkd_file(self, stanza):
        """Generate an .network file from the provided data."""

        name = stanza['name']
        itype = stanza['type']
        pairs = stanza['args'].items()

        if itype == "loopback":
            return

        lines = ["[Match]"]
        lines += ["Name=%s\n" % name]
        lines += ["[Network]"]
        if itype == "dhcp":
            lines += ["DHCP=yes"]
        else:
            lines += self.generate_networkd_entries(pairs)

        return "\n".join(lines)

    def generate_networkd_entries(self, pairs):
        """Generate networkd configuration entries with the other parameters"""

        address = None
        netmask = None
        gateway = None
        lines = []
        for pair in pairs:
            if pair[0] == 'address':
                address = pair[1]
            elif pair[0] == 'netmask':
                netmask = pair[1]
            elif pair[0] == 'gateway':
                gateway = pair[1]

        if address and netmask:
            network_suffix = self.convert_net_mask_to_cidr_suffix (netmask);
            address_line = address + '/' + str(network_suffix)
            lines += ["Address=%s" % address_line]
        elif address or netmask:
            raise Exception('address and netmask must be specified together')

        if gateway is not None:
            lines += ["Gateway=%s" % gateway]

        return lines

    def convert_net_mask_to_cidr_suffix(self, mask):
        """Convert dotted decimal form of a subnet mask to CIDR suffix notation

        For example: 255.255.255.0 -> 24
        """
        return sum(bin(int(x)).count('1') for x in mask.split('.'))

    def parse_network_stanzas(self, config):
        """Parse a network config environment variable into stanzas.

        Network config stanzas are semi-colon separated.
        """

        return [self.parse_network_stanza(s) for s in config.split(";")]

    def parse_network_stanza(self, stanza):
        """Parse a network config stanza into name, type and arguments.

        Each stanza is of the form name:type[,arg=value]...

        For example:
                   lo:loopback
                   eth0:dhcp
                   eth1:static,address=10.0.0.1,netmask=255.255.0.0
        """
        elements = stanza.split(",")
        lead = elements.pop(0).split(":")
        if len(lead) != 2:
            raise SimpleNetworkError("Stanza '%s' is missing its type" %
                                     stanza)
        iface = lead[0]
        iface_type = lead[1]

        if iface_type not in ['loopback', 'static', 'dhcp']:
            raise SimpleNetworkError("Stanza '%s' has unknown interface type"
                                     " '%s'" % (stanza, iface_type))

        argpairs = [element.split("=", 1) for element in elements]
        output_stanza = { "name": iface,
                          "type": iface_type,
                          "args": {} }
        for argpair in argpairs:
            if len(argpair) != 2:
                raise SimpleNetworkError("Stanza '%s' has bad argument '%r'"
                                         % (stanza, argpair.pop(0)))
            if argpair[0] in output_stanza["args"]:
                raise SimpleNetworkError("Stanza '%s' has repeated argument"
                                         " %s" % (stanza, argpair[0]))
            output_stanza["args"][argpair[0]] = argpair[1]

        return output_stanza

    def status(self, **kwargs):
        '''Provide status output.

        The ``msg`` keyword argument is the actual message,
        the rest are values for fields in the message as interpolated
        by %.

        '''

        self.output.write('%s\n' % (kwargs['msg'] % kwargs))

SimpleNetworkConfigurationExtension().run()