【neutron源码分析】neutron-dhcp-agent源码分析

迈不过友情╰ 2022-06-12 07:50 339阅读 0赞

## 1 概念 ##

neutron dhcp为租户网络提供DHCP服务IP地址动态分配，另外还会提供metadata请求服务。

重要的配置选项

*  interface\_driver：dhcp agent使用interface\_driver来创建tap设备。
 *  dhcp\_driver：默认配置是neutron.agent.linux.dhcp.Dnsmasq。dhcp agent默认使用dnsmasq来实现dhcp服务。
 *  dhcp\_agent\_manager：RPC服务的manager，默认是neutron.agent.dhcp\_agent.DhcpAgentWithStateReport

dhcp agent主要三个功能：

*  报告状态。
 *  处理RPC API。
 *  启动dhcp服务

1). 启动一个协程定期上报neutron-dhcp-agent network状态，通过rpc上报给neutron-server启动时创建。然后通过core\_plugin上报给数据库并进行更新network壮体啊。

2). 启动dnsmasq进程，检测qdhcp-xxxx namespace中的ns-xxxx端口接收到的dhcp discover请求。在启动dnsmasq进程的过程中，是否需要创建namespace中的ns-xxx端口，是否需要配置namespace中的iptables，是否需要refresh dnsmasq进程所需配置文件。

创建 network 并在 subnet 上 enable DHCP 时，网络节点上的 DHCP agent 会启动一个 dnsmasq 进程为 network 提供 DHCP 服务。dnsmasq 与 network 是一对一关系，一个 dnsmasq 进程可以为同一 netowrk 中所有 enable 了 DHCP 的 subnet 提供服务。

***dnsmasq 重要的启动参数：***

\--dhcp-hostsfile  
存放 DHCP host 的文件，这里的 host 在就是 instance。 dnsmasq 从该文件获取 host 的 IP 与 MAC 的对应关系。 每个 host 对应一个条目，来源于 Neutron 数据库。

\# cat /var/lib/neutron/dhcp/c4206574-8125-41e6-be09-5a624dadb570/host  
fa:16:3f:ba:33:99,host-10-10-10-102.openstacklocal,10.10.10.102

\--interface  
指定提供 DHCP 服务的 interface。 dnsmasq 会在该 interface 上监听 instance 的 DHCP 请求。

\# ip netns exec qdhcp-c4206574-8125-41e6-be09-5a624dadb570 ip link  
1: lo: <LOOPBACK,UP,LOWER\_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT  
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00  
20: tap07130e1c-a6: <BROADCAST,MULTICAST,UP,LOWER\_UP> mtu 1500 qdisc noqueue state UNKNOWN mode DEFAULT  
    link/ether fa:16:3f:ba:33:99 brd ff:ff:ff:ff:ff:ff

--------------------

## 2 源码分析 ##

[entry_points] console_scripts = neutron-bgp-dragent = neutron.cmd.eventlet.agents.bgp_dragent:main neutron-db-manage = neutron.db.migration.cli:main neutron-debug = neutron.debug.shell:main neutron-dhcp-agent = neutron.cmd.eventlet.agents.dhcp:main neutron-keepalived-state-change = neutron.cmd.keepalived_state_change:main

neutron-dhcp-agent的入口为neutron.agent.dhcp\_agent:main，以Service启动；Manager类为DhcpAgentWithStateReport，汇报DHCPAgent的状态。

def main():
        register_options(cfg.CONF)
        common_config.init(sys.argv[1:])
        config.setup_logging()
        server = neutron_service.Service.create(
            binary='neutron-dhcp-agent', topic=topics.DHCP_AGENT, report_interval=cfg.CONF.AGENT.report_interval, manager='neutron.agent.dhcp.agent.DhcpAgentWithStateReport')
        service.launch(cfg.CONF, server).wait()

读取注册配置（包括dhcpagent、interface\_driver、use\_namespace等）。

创建一个service。主题是DHCP\_AGENT，默认驱动是Dnsmasq，默认的管理器是DhcpAgentWithStateReport

##     ##

##      plugin端的rpc调用方法（一般由neutron.api.v2.base.py发出）在neutron.api.rpc.agentnoftifiers.DhcpAgentNotifyAPI中实现，发出notification消息，会调用agent中对应的方法：    ##

VALID_RESOURCES = ['network', 'subnet', 'port']
    VALID_METHOD_NAMES = ['network.create.end', 'network.update.end', 'network.delete.end', 'subnet.create.end', 'subnet.update.end', 'subnet.delete.end', 'port.create.end', 'port.update.end', 'port.delete.end']

## 2.1 DhcpAgentWithStateReport类 ##

class DhcpAgentWithStateReport(DhcpAgent): def __init__(self, host=None, conf=None): super(DhcpAgentWithStateReport, self).__init__(host=host, conf=conf) self.state_rpc = agent_rpc.PluginReportStateAPI(topics.REPORTS) self.agent_state = { 'binary': 'neutron-dhcp-agent', 'host': host, 'availability_zone': self.conf.AGENT.availability_zone, 'topic': topics.DHCP_AGENT, 'configurations': { 'dhcp_driver': self.conf.dhcp_driver, 'dhcp_lease_duration': self.conf.dhcp_lease_duration, 'log_agent_heartbeats': self.conf.AGENT.log_agent_heartbeats}, 'start_flag': True, 'agent_type': constants.AGENT_TYPE_DHCP} report_interval = self.conf.AGENT.report_interval if report_interval: self.heartbeat = loopingcall.FixedIntervalLoopingCall( self._report_state) self.heartbeat.start(interval=report_interval)

DhcpAgentWithStateReport继承2.2中的DhcpAgent类，主要作用时创建一个协程定期向neutron-server上报agent的network状态，然后更新到数据库。

## 2.2 DhcpAgent类 ##

DhcpAgent初始化过程：继承manager.Manager继承n\_rpc.RpcCallback和periodic\_task.PeriodicTasks，提供周期性运行任务的方法。

*         NetworCache: 保存active的dhcp networks，DhcpAgentWithStateReport类的\_report\_state将数据信息上报到neutron-server
 *         dhcp\_dir：保存dhcp networks信息，/var/lib/neutron/dhcp
 *         dhcp\_driver: neutron.agent.linux.dhcp.Dnsmasq，dhcp\_driver\_cls是Dnsmasq的实例化
 *         DhcpPluginApi中topics.PLUGIN为q-plugin，agent一端rpc api，作为向plugin发出rpc消息的handler

def __init__(self, host=None, conf=None):
        super(DhcpAgent, self).__init__(host=host)
        self.needs_resync_reasons = collections.defaultdict(list)
        self.conf = conf or cfg.CONF
        self.cache = NetworkCache()
        self.dhcp_driver_cls = importutils.import_class(self.conf.dhcp_driver)
        ctx = context.get_admin_context_without_session()
        self.plugin_rpc = DhcpPluginApi(topics.PLUGIN, ctx, self.conf.host)
        # create dhcp dir to store dhcp info dhcp_dir = os.path.dirname("/%s/dhcp/" % self.conf.state_path)
        utils.ensure_dir(dhcp_dir)
        self.dhcp_version = self.dhcp_driver_cls.check_version()
        self._populate_networks_cache()
        # keep track of mappings between networks and routers for # metadata processing self._metadata_routers = {}  # {network_id: router_id} self._process_monitor = external_process.ProcessMonitor(
            config=self.conf, resource_type='dhcp')

def _populate_networks_cache(self): """Populate the networks cache when the DHCP-agent starts.""" try: existing_networks = self.dhcp_driver_cls.existing_dhcp_networks( self.conf ) for net_id in existing_networks: net = dhcp.NetModel({ "id": net_id, "subnets": [], "ports": []}) self.cache.put(net) except NotImplementedError: # just go ahead with an empty networks cache LOG.debug("The '%s' DHCP-driver does not support retrieving of a " "list of existing networks", self.conf.dhcp_driver)

@classmethod def existing_dhcp_networks(cls, conf): """Return a list of existing networks ids that we have configs for.""" confs_dir = cls.get_confs_dir(conf) try: return [ c for c in os.listdir(confs_dir) if uuidutils.is_uuid_like(c) ] except OSError: return []

@staticmethod def get_confs_dir(conf):
        return os.path.abspath(os.path.normpath(conf.dhcp_confs))

\_populate\_networks\_cache: /var/lib/neutron/dhcp目录下的dhcp netoworks实例NetModel对象存入self.cache中。

def after_start(self): self.run()
            LOG.info(_LI("DHCP agent started")) def run(self):
            """Activate the DHCP agent.""" self.sync_state()
            self.periodic_resync()

@utils.synchronized('dhcp-agent')
    def sync_state(self, networks=None):
        """Sync the local DHCP state with Neutron. If no networks are passed, or 'None' is one of the networks, sync all of the networks. """ only_nets = set([] if (not networks or None in networks) else networks)
        LOG.info(_LI('Synchronizing state'))
        pool = eventlet.GreenPool(self.conf.num_sync_threads)
        known_network_ids = set(self.cache.get_network_ids())
    
        try:
            active_networks = self.plugin_rpc.get_active_networks_info()
            LOG.info(_LI('All active networks have been fetched through RPC.'))
            active_network_ids = set(network.id for network in active_networks)
            for deleted_id in known_network_ids - active_network_ids:
                try:
                    self.disable_dhcp_helper(deleted_id)
                except Exception as e:
                    self.schedule_resync(e, deleted_id)
                    LOG.exception(_LE('Unable to sync network state on ' 'deleted network %s'), deleted_id)
    
            for network in active_networks:
                if (not only_nets or # specifically resync all network.id not in known_network_ids or # missing net network.id in only_nets):  # specific network to sync pool.spawn(self.safe_configure_dhcp_for_network, network)
            pool.waitall()
            LOG.info(_LI('Synchronizing state complete'))

sync\_state：会发出rpc消息给plugin，获取最新的网络状态并更新本地信息，在调用dnsmasq进程使之生效。在启动后只运行一次。将未在数据库中的，从cache中移除，更新active的dhcp networks。调用safe\_configure\_dhcp\_for\_network，代码如下所示：

def configure_dhcp_for_network(self, network): if not network.admin_state_up: return enable_metadata = self.dhcp_driver_cls.should_enable_metadata( self.conf, network) dhcp_network_enabled = False for subnet in network.subnets: if subnet.enable_dhcp: if self.call_driver('enable', network): dhcp_network_enabled = True self.cache.put(network) break if enable_metadata and dhcp_network_enabled: for subnet in network.subnets: if subnet.ip_version == 4 and subnet.enable_dhcp: self.enable_isolated_metadata_proxy(network) break elif (not self.conf.force_metadata and not self.conf.enable_isolated_metadata): # In the case that the dhcp agent ran with metadata enabled, # and dhcp agent now starts with metadata disabled, check and # delete any metadata_proxy. self.disable_isolated_metadata_proxy(network)

最终调用call\_driver:

def call_driver(self, action, network, **action_kwargs): """Invoke an action on a DHCP driver instance.""" LOG.debug('Calling driver for network: %(net)s action: %(action)s', { 'net': network.id, 'action': action}) try: # the Driver expects something that is duck typed similar to # the base models. driver = self.dhcp_driver_cls(self.conf, network, self._process_monitor, self.dhcp_version, self.plugin_rpc) getattr(driver, action)(**action_kwargs) return True

call\_driver调用Dnsmasq中enable方法

def enable(self): """Enables DHCP for this network by spawning a local process.""" if self.active: self.restart() elif self._enable_dhcp(): common_utils.ensure_dir(self.network_conf_dir) interface_name = self.device_manager.setup(self.network) self.interface_name = interface_name self.spawn_process()

def _get_process_manager(self, cmd_callback=None):
        return external_process.ProcessManager(
            conf=self.conf, uuid=self.network.id, namespace=self.network.namespace, default_cmd_callback=cmd_callback, pid_file=self.get_conf_file_name('pid'), run_as_root=True)

如果dnsmasq进程处于active状态则重启，从/var/lib/neutron/dhcp/$\{networkid\}下取pid

def active(self):
        pid = self.pid
        if pid is None:
            return False cmdline = '/proc/%s/cmdline' % pid
        try:
            with open(cmdline, "r") as f:
                return self.uuid in f.readline()
        except IOError:
            return False

查看/proc/$\{pid\}/cmdline是否有网络id，如果有dnsmasq处于active状态。处于active则进行重启

def restart(self):
        """Restart the dhcp service for the network.""" self.disable(retain_port=True)
        self.enable()

先disable，然后在enable，

enable函数在创建dnsmasq判断network下是否有enable dhcp的subnet，network至少有一个subnet enable dhcp才会执行创建dnsmasq进程。

device\_manager.setup，为dhcp network创建和初始化设备

def setup(self, network): """Create and initialize a device for network's DHCP on this host.""" port = self.setup_dhcp_port(network) self._update_dhcp_port(network, port) interface_name = self.get_interface_name(network, port) if ip_lib.ensure_device_is_ready(interface_name, namespace=network.namespace): LOG.debug('Reusing existing device: %s.', interface_name) else: try: self.driver.plug(network.id, port.id, interface_name, port.mac_address, namespace=network.namespace, mtu=network.get('mtu')) except Exception: with excutils.save_and_reraise_exception(): LOG.exception(_LE('Unable to plug DHCP port for ' 'network %s. Releasing port.'), network.id) self.plugin.release_dhcp_port(network.id, port.device_id) self.fill_dhcp_udp_checksums(namespace=network.namespace) ip_cidrs = [] for fixed_ip in port.fixed_ips: subnet = fixed_ip.subnet if not ipv6_utils.is_auto_address_subnet(subnet): net = netaddr.IPNetwork(subnet.cidr) ip_cidr = '%s/%s' % (fixed_ip.ip_address, net.prefixlen) ip_cidrs.append(ip_cidr) if self.driver.use_gateway_ips: # For each DHCP-enabled subnet, add that subnet's gateway # IP address to the Linux device for the DHCP port. for subnet in network.subnets: if not subnet.enable_dhcp: continue gateway = subnet.gateway_ip if gateway: net = netaddr.IPNetwork(subnet.cidr) ip_cidrs.append('%s/%s' % (gateway, net.prefixlen)) if self.conf.force_metadata or self.conf.enable_isolated_metadata: ip_cidrs.append(METADATA_DEFAULT_CIDR) self.driver.init_l3(interface_name, ip_cidrs, namespace=network.namespace) self._set_default_route(network, interface_name) try: self._cleanup_stale_devices(network, port) except Exception: # catch everything as we don't want to fail because of # cleanup step LOG.error(_LE("Exception during stale dhcp device cleanup")) return interface_name

setup\_dhcp\_port函数的作用为创建或更新dhcp port信息

def setup_dhcp_port(self, network): """Create/update DHCP port for the host if needed and return port.""" # The ID that the DHCP port will have (or already has). device_id = self.get_device_id(network) # Get the set of DHCP-enabled subnets on this network. dhcp_subnets = {subnet.id: subnet for subnet in network.subnets if subnet.enable_dhcp} # There are 3 cases: either the DHCP port already exists (but # might need to be updated for a changed set of subnets); or # some other code has already prepared a 'reserved' DHCP port, # and we just need to adopt that; or we need to create a new # DHCP port. Try each of those in turn until we have a DHCP # port. for setup_method in (self._setup_existing_dhcp_port, self._setup_reserved_dhcp_port, self._setup_new_dhcp_port): dhcp_port = setup_method(network, device_id, dhcp_subnets) if dhcp_port: break else: raise exceptions.Conflict() # Convert subnet_id to subnet dict fixed_ips = [dict(subnet_id=fixed_ip.subnet_id, ip_address=fixed_ip.ip_address, subnet=dhcp_subnets[fixed_ip.subnet_id]) for fixed_ip in dhcp_port.fixed_ips] ips = [DictModel(item) if isinstance(item, dict) else item for item in fixed_ips] dhcp_port.fixed_ips = ips return dhcp_port

get\_device\_id 为：dhcp-%\{networkid\}，例如：qdhcp-c4206574-8125-41e6-be09-5a624dadb570

get\_interface\_name为：tap%\{portkid的11位\}，例如：tap07130e1c-a6

![Image 1][]

ensure\_device\_is\_ready: 检验interface\_name是否已经在本地的host的命名空间中被创建，执行命令：ip netns exec qdhcp-xxxx ip link tapxxxx up

def ensure_device_is_ready(device_name, namespace=None):
        dev = IPDevice(device_name, namespace=namespace)
        dev.set_log_fail_as_error(False)
        try:
            # Ensure the device is up, even if it is already up. If the device # doesn't exist, a RuntimeError will be raised. dev.link.set_up()
        except RuntimeError:
            return False return True

反正就是执行了一大堆 ip netns exec这些命令，没有就创建的命令ip link add，plug在root namespace和dhcp namespace创建veth pair，实现通信。

def spawn_process(self):
        """Spawn the process, if it's not spawned already.""" # we only need to generate the lease file the first time dnsmasq starts # rather than on every reload since dnsmasq will keep the file current self._output_init_lease_file()
        self._spawn_or_reload_process(reload_with_HUP=False)

spawn\_process创建一个进程监听虚拟机dhcp discover请求，

\_output\_init\_lease\_file函数/var/lib/neutron/dhcp/$\{network\_id\}下生成leases文件，该文件保存IP，MAC对应关系，以及他们的租赁时间

def _spawn_or_reload_process(self, reload_with_HUP): """Spawns or reloads a Dnsmasq process for the network. When reload_with_HUP is True, dnsmasq receives a HUP signal, or it's reloaded if the process is not running. """ self._output_config_files() pm = self._get_process_manager( cmd_callback=self._build_cmdline_callback) pm.enable(reload_cfg=reload_with_HUP) self.process_monitor.register(uuid=self.network.id, service_name=DNSMASQ_SERVICE_NAME, monitored_process=pm)

\_spawn\_or\_reload\_process函产生一些dnsmasq命令参数，启动dnsmasq进程去监听接口，接收dhcp discover请求

def _output_config_files(self):
        self._output_hosts_file()
        self._output_addn_hosts_file()
        self._output_opts_file()

在/var/lib/neutron/dhcp/$\{networkid\}目录下生成addn\_hosts，host，opts文件

创建dnsmasq进程的命令行为：\_build\_cmdline\_callback函数：

ef _build_cmdline_callback(self, pid_file):
        # We ignore local resolv.conf if dns servers are specified # or if local resolution is explicitly disabled. _no_resolv = (
            '--no-resolv' if self.conf.dnsmasq_dns_servers or not self.conf.dnsmasq_local_resolv else '')
        cmd = [
            'dnsmasq', '--no-hosts', _no_resolv, '--strict-order', '--except-interface=lo', '--pid-file=%s' % pid_file, '--dhcp-hostsfile=%s' % self.get_conf_file_name('host'), '--addn-hosts=%s' % self.get_conf_file_name('addn_hosts'), '--dhcp-optsfile=%s' % self.get_conf_file_name('opts'), '--dhcp-leasefile=%s' % self.get_conf_file_name('leases'), '--dhcp-match=set:ipxe,175', ]

Dnsmasq通过/var/lib/neutron/dhcp/目录下的配置文件启动dnsmasq进程，在DHCP更新的时候，更新这些配置文件并reload配置。

dnsmasq --no-hosts --no-resolv --strict-order --except-interface=lo

\--pid-file=/var/lib/neutron/dhcp/e2a32993-48b4-4202-95ea-07d6b865a13e/pid

\--dhcp-hostsfile=/var/lib/neutron/dhcp/e2a32993-48b4-4202-95ea-07d6b865a13e/host

\--addn-hosts=/var/lib/neutron/dhcp/e2a32993-48b4-4202-95ea-07d6b865a13e/addn\_hosts

\--dhcp-optsfile=/var/lib/neutron/dhcp/e2a32993-48b4-4202-95ea-07d6b865a13e/opts

\--dhcp-leasefile=/var/lib/neutron/dhcp/e2a32993-48b4-4202-95ea-07d6b865a13e/leases

\--dhcp-match=set:ipxe,175 --bind-interfaces

\--interface=tap5b9921f2-be

\--dhcp-range=set:tag0,10.248.128.0,static,86400s

\--dhcp-option-force=option:mtu,1500 --dhcp-lease-max=256

\--conf-file= --domain=openstacklocal

except-interface=lo 多个dnsmasq实例可以同时运行在同一台主机上并监听不同的interface，不监听回环接口

dhcp-hostsfile IP与虚拟机的静态映射关系

interface: dnsmasp进程监听接口是否有dhcp diskcover请求

dhcp-optsfile DNS服务器地址等选项,tftp-server

periodic\_resync：一个协程来运行\_periodic\_resync\_helper方法，一个无限循环周期性的调用sync\_state。

## 2.3 DhcpPluginApi类 ##

从agent往plugin进行rpc调用的api

class DhcpPluginApi(object): def __init__(self, topic, context, host):
            self.context = context
            self.host = host
            target = oslo_messaging.Target(
                    topic=topic, namespace=constants.RPC_NAMESPACE_DHCP_PLUGIN, version='1.0')
            self.client = n_rpc.get_client(target)
    
        def get_active_networks_info(self):
    
        def get_network_info(self, network_id):
    
        def create_dhcp_port(self, port):
    
        def update_dhcp_port(self, port_id, port):
           
        def release_dhcp_port(self, network_id, device_id):

##     ##

[Image 1]: