keepalived配置说明（长期翻译更新。。。）

系统管理员 2022-04-15 06:43 213阅读 0赞

[https://github.com/acassen/keepalived/blob/master/doc/keepalived.conf.SYNOPSIS][https_github.com_acassen_keepalived_blob_master_doc_keepalived.conf.SYNOPSIS]

### 配置概述 ###

*  此文件描述所有可获得的Keepalived关键字。keepalived.conf文件由三个配置部分组成 :
    
     *  Globals 配置
     *  VRRP 配置
     *  LVS 配置
     *  BFD 配置(2层转发相关)

##### 注释 #####

*  两种有效的注释字符串 : 如果要写注释就使用 \# 或者 !

##### 参数语法 #####

##### 条件配置和配置id #####

1).config-id默认是节点名的第一部分。可以通过keepalived的-i或者--config-id来进行覆盖,任何以'@'开头的配置行就是条件配置行。跟在@后面的那个单词与-i(或者--config-id)指定的id名进行比较，如果不匹配，则忽略。
    2).另外，'@^'是一个消极的比较，如果其他配置都不匹配，那么就匹配这个。
    3).这样做的目的是一个配置文件可以被不同的系统使用，其中唯一的区别可能是router_id，vrrp实例优先级，可能还有接口名
    
    例子:
    global_defs
    {
        
    @main   router_id main_router
    @backup router_id backup_router
    }
    ...
    vrrp_instance VRRP1 {
        
        ...
    @main    unicast_src_ip 1.2.3.4
    @backup  unicast_src_ip 1.2.3.5
    @backup2 unicast_src_ip 1.2.3.6
        unicast_peer {
        
    @^main        1.2.3.4
    @^backup      1.2.3.5
    @^backup2     1.2.3.6
        }
    }
    
    4). 如果用-i main来调用keepalived(使用上面的配置)，或者如果使用-i，配置id没有指定，那么配置id默认就是main.xxxx(xxx为其他字符串)那么keepalived将会使用router_id为main_router。如果用-i backup来调用keepalived或者配置id为backup，那么backup_router会被使用。如果没有使用-i backup来调用keepalived或者配置id部位main或backup，而是-i带了别的参数。那么backup_router就不会被使用
    5). 如果用-i backup调用keepalived，或者配置id为backup，则使用backup_router，如果没有使用-i调用，则节点名不是main或backup或者带的是其他参数，router_id则将不会被设置。
    6). 配置id为main的unicast peers配置则为1.2.3.5和1.2.3.6.（1.2.3.4）

##### 脚本 #####

*  三种类型的脚本可以被配置执行。
    
     *  a. 通知脚本：当vrrp实例或vrrp组的状态时发生变化，或者虚拟服务器的状态发生了up或者down时候调用的通知脚本
     *  b. vrrp跟踪脚本：这些脚本的调用如果退出码为非0会导致vrrp实例退出，或者如果权值被指定，那么将会加减vrrp实例相应的优先级
     *  c. lvs checker misc脚本：如果脚本以非零值退出，那么会直接down调real server服务.

默认这些脚本会以用户keepalived_script来执行，如果用户不存在，且没有指定root来执行。那就以每一个脚本的指定用户/组来执行
    为了能够被SIGTERM终止，所有的脚本必须有写权限。当父进程终止的时候，脚本会收到SIGTERM信号。keepalived会等待脚本运行结束

##### 配置导入 #####

这个可以让支持多文件导入.
    include directive格式为：
    include FILENAME

##### 配置文件语法解析 #####

### 全局配置 ###

这个块有5个子块
        * Global definitions
        * Static track groups
        * Static addresses
        * Static rules
        * Static routes

##### Global definitions #####

The configuration block 如下：
    global_defs {
                                         # 块的标识
        notification_email {
                              # 告警邮件地址
           <EMAIL ADDRESS>                        # 标准邮件地址
           <EMAIL ADDRESS>
           ...
        }
        notification_email_from <EMAIL ADDRESS>   # 发件人(smtp协议)
                                                  #   defaults to keepalived@<local host name>
        smtp_server <ADDRESS>|<DOMAIN_NAME> [<PORT>]
                                                  # SMTP 服务器IP地址或者域名
                                                  #  端口可选 (默认是25)
        smtp_helo_name <HOST_NAME>                # 指定在HELO消息中所使用的名称。默认为本地主机名。
        smtp_connect_timeout <INTEGER>            # smtp服务器连接超时时间
        smtp_alert <BOOL>                         # 设置所有smtp_alerts的默认状态，当master状态变迁时激活smtp通知
        smtp_alert_vrrp <BOOL>                    # 设置vrrp的smtp_alerts的状态
        smtp_alert_checker <BOOL>                 # 设置checker的smtp_alerts的状态
        no_email_faults                           # 当处于fault状态时不发送smtp alerts
        router_id <STRING>                        # router标识
        vrrp_garp_interval <DECIMAL>              # 默认的免费arp之间的发送间隔，单位秒，可以精确到毫秒
        vrrp_gna_interval <DECIMAL>               # 默认的ipv6 NA之间的发送间隔，单位秒，可以精确到毫秒
        vrrp_mcast_group4 <IPv4 ADDRESS>          # 指定发送VRRP组播消息使用的IPV4组播地址。默认是224.0.0.18
        vrrp_mcast_group6 <IPv6 ADDRESS>          # 指定发送VRRP组播消息所使用的IPV6组播地址。默认是ff02::12
        vrrp_skip_check_adv_addr <BOOL>           # 默认是不跳过检查。检查收到的VRRP通告中的所有地址，设置此命令的意思是，如果通告与接收的上一个通告来自相同的master路由器，则不执行检查(跳过检查)。
        default_interface <INTERFACE>             # 为static address设置默认接口，默认是eth0
        lvs_sync_daemon <INTERFACE> <VRRP_INSTANCE> [id <SYNC_ID>] [maxlen <LEN>] [port <PORT>] [ttl <TTL>] [group <IP ADDR>]
                                                  # 设置LVS同步服务的相关内容。可以同步LVS的状态信息。
                                                  # INTERFACE：指定同步服务绑定的接口。
                                                  # VRRP_INSTANCE：指定同步服务绑定的VRRP实例。
                                                  # id <SYNC_ID>：指定同步服务所使用的SYNCID，只有相同的SYNCID才会同步。范围是0-255.
                                                  # maxlen：指定数据包的最大长度。范围是1-65507
                                                  # port：指定同步所使用的UDP端口。
                                                  # group：指定组播IP地址                                                
                                                  # 注意：maxlen, port, ttl and group 只能在Linux 4.3或者之后的版本使用.
        lvs_flush                                 # 在keepalived启动时，刷新所有已经存在的LVS配置。（在1.2.7版本上不可用，1.3.5可用）
        vrrp_garp_master_delay <INTEGER>          # 当转换为MASTER状态时，延迟多少秒发送第二组的免费ARP。默认为5s，0表示不发送第二组免的免费ARP。（在1.2.7版本上不可用，1.3.5可用）
        vrrp_garp_master_repeat <INTEGER>         # 当转换为MASTER状态时，在一组中一次发送的免费ARP数量。默认是5.
        vrrp_garp_lower_prio_delay <INTEGER>      # 当MASTER收到更低优先级的通告时，延迟多少秒发送第二组的免费ARP。
        vrrp_garp_lower_prio_repeat <INTEGER>     # 当MASTER收到更低优先级的通告时，在一组中一次发送的免费ARP数量。
        vrrp_garp_master_refresh <INTEGER>        # 当keepalived成为MASTER以后，刷新免费ARP的最小时间间隔(会再次发送免费ARP)。默认是0，表示不会刷新。
        vrrp_garp_master_refresh_repeat <INTEGER> # 当keepalived成为MASTER以后，每次刷新会发送多少个免费ARP。默认是1
        vrrp_lower_prio_no_advert [<BOOL>]        # 默认是false。如果收到低优先级的通告，不发送任何通告。
        vrrp_higher_prio_send_advert [<BOOL>]     # 如果我们是master，收到一个更高优先级的vrrp，在我们变成backup之前发送一个通告。这意味如果其他master设置了garp_lower_priority_repeat，他将重新发送免费arp信息。这是为了解决出现双master的情况，且最后一个看到的免费arp是从我们为您这里发出的。
        vrrp_version <INTEGER:2..3>               # vrrp版本，默认是vrrp version 2
        vrrp_iptables [keepalived_in [keepalived_out]] # 默认是INPUT，指定iptables chains添加。如果没有指定，则不添加
        vrrp_ipsets ipset4 [ipset6 [ipset_if6]]   # 设置ipset的名字，如果没设置就不被使用。默认值为keepalived
                                                  # 人如果ipset6没有指定，那么名字为ipset的名字后面加个6，如果ipset_if6没有被指定，那就删除ipset6中的那个6，然后加上_if6
        vrrp_check_unicast_src                    # 在单播模式中，开启对VRRP数据包的源地址做检查，源地址必须是单播邻居之一。
        vrrp_strict                               # 严格遵守VRRP协议。下列情况将会阻止启动Keepalived：1. 没有VIP地址。2. 单播邻居。3. 在VRRP版本2中有IPv6地址（1.2.7中无效，1.3.5有效）
        vrrp_priority <INTEGER:-20..19>           # 设置VRRP进程的优先级。
        checker_priority <INTEGER:-20..19>        # 设置checker进程的优先级。
        bfd_priority <INTEGER:-20..19>            # 设置BFD进程的优先级。（高版本才有BFD）
        vrrp_no_swap                              # vrrp进程不能够被交换
        checker_no_swap                           # checker进程不能够被交换
        bfd_no_swap                               # checker进程不能够被交换
        vrrp_rt_priority <INTEGER:1..99>          # 将vrrp子进程设置为在指定的优先级使用实时调度（1.3.5版本无此功能）
        checker_rt_priority <INTEGER:1..99>       # 将checker子进程设置为在指定的优先级使用实时调度（1.3.5版本无此功能）
        bfd_rt_priority <INTEGER:1..99>           # 将bfd子进程设置为在指定的优先级使用实时调度（1.3.5版本无此功能）
        vrrp_rlimit_rtime <INTEGER>               # 设置阻塞系统调用之间的CPU时间限制，以微秒为单位(默认为1000)
        checker_rlimit_rtime <INTEGER>            # 设置阻塞系统调用之间的CPU时间限制，以微秒为单位(默认为1000)e
        bfd_rlimit_rtime <INTEGER>                # 设置阻塞系统调用之间的CPU时间限制，以微秒为单位(默认为1000)
                                                  #
                                                  # 如果keepalived编译了SNMP的支持
                                                  # 那么以下的这些是可用的
                                                  # Note: keepalived, checker and rfc support can be
                                                  #   individually enabled/disabled
        snmp_socket <PROTOCOL>:<ADDRESS>[:<PORT>] # specify socket to use for connecting to SNMP master agent (default unix:/var/agentx/master)
                                                  #   (see source module keepalived/vrrp/vrrp_snmp.c for more details)
        enable_snmp_vrrp                          # enable SNMP handling of vrrp element of KEEPALIVED MIB
        enable_snmp_checker                       # enable SNMP handling of checker element of KEEPALIVED MIB
        enable_snmp_rfc                           # enable SNMP handling of RFC2787 and RFC6527 VRRP MIBs
        enable_snmp_rfcv2                         # enable SNMP handling of RFC2787 VRRPv2 MIB
        enable_snmp_rfcv3                         # enable SNMP handling of RFC6527 VRRPv3 MIB
        enable_traps                              # enable SNMP trap generation
                                                  #
        enable_dbus                               # 使能DBus接口
        dbus_service_name SERVICE_NAME            # dbus服务名，默认是org.keepalived.Vrrp1
                                                  # 如果你想运行多个keepalived进程才有用
                                                  #
        script_user USERNAME [GROUPNAME]          # 设置运行脚本默认用户和组。如果没有指定，则默认用户为keepalived_script(需要该用户存在)，否则为root用户。默认groupname同username。
        enable_script_security                    # 如果脚本路径的任一部分对于非root用户来说，都具有可写权限，则不会以root身份运行脚本。
        notify_fifo FIFO_NAME                     # 向FIFO写入通知事件，输出格式参见vrrp_notify_fifo和lvs_notify_fifo，有关详细信息，请参见vrrp_sync_group下的描述，doc/sample/sample_notify_fifo.sh的示例用法。
        notify_fifo_script STRING|QUOTED_STRING [username [groupname]]
                                                  # keepalived运行的脚本，用来处理通知事件，FIFO名称将作为最后一个参数传递给脚本
        vrrp_notify_fifo FIFO_NAME                # FIFO要将vrrp通知事件写入(必须与其他FIFO名称不同)，写入的字符串将是表单的一行:INSTANCE "VI_1" MASTER 100，并将以新的行字符结束。有关输出的详细信息，请参见vrrp_sync_group下的描述。和doc/sample/sample_notify_fifo.sh的示例用法。
        vrrp_notify_fifo_script STRING|QUOTED_STRING [username [groupname]]
                                                  # keepalived运行的脚本，用来处理通知事件，FIFO名称将作为最后一个参数传递给脚本
        lvs_notify_fifo FIFO_NAME                 # FIFO要将notify healthchecker事件写入(必须与其他FIFO名称不同)，所写的字符串将是表单的一行:
                                                  #   VS [192.168.201.15]:tcp:80 {UP|DOWN}
                                                  #   RS [1.2.3.4]:tcp:80 [192.168.201.15]:tcp:80 {UP|DOWN}
                                                  # 以换行符为结束符.
        lvs_notify_fifo_script STRING|QUOTED_STRING [username [groupname]]
                                                  # script to be run by keepalived to process healthchecher notify events
                                                  # The FIFO name will be passed to the script as the last parameter
        dynamic_interfaces                        # 允许配置包含启动时不存在的接口。这允许keepalived使用可能被删除的接口，并恢复，也允许VMAC接口上的虚拟和静态路由和规则
    
                                                  # The following options are only needed for large configurations, where either
                                                  # keepalived creates a large number of interface, or the system has a large
                                                  # number of interface. These options only need using if
                                                  # "Netlink: Receive buffer overrun" messages are seen in the system logs.
                                                  # If the buffer size needed exceeds the value in /proc/sys/net/core/rmem_max
                                                  #  the corresponding force option will need to be set.
        vrrp_netlink_cmd_rcv_bufs BYTES           # Set netlink receive buffer size. This is useful for
        vrrp_netlink_cmd_rcv_bufs_force <BOOL>    #  very large configurations where a large number of interfaces exist, and
        vrrp_netlink_monitor_rcv_bufs BYTES       #  the initial read of the interfaces on the system causes a netlink buffer
        vrrp_netlink_monitor_rcv_bufs_force <BOOL> # overrun.
        lvs_netlink_cmd_rcv_bufs BYTES            #  The vrrp netlink command and monitor socket and the checker command
        lvs_netlink_cmd_rcv_bufs_force <BOOL>     #  and monitor socket buffer sizes can be independently set. 
        lvs_netlink_monitor_rcv_bufs BYTES        #  The force flag means to use SO_RCVBUFFORCE, so that the buffer size can
        lvs_netlink_monitor_rcv_bufs_force <BOOL> #  exceed /proc/sys/net/core/rmem_max.
                                                  # When a socket is opened, the kernel configures the max rx buffer size for
                                                  # the socket to /proc/sys/net/core/rmem_default. On some systems this can be
                                                  # very large, and even generally this can be much larger than necessary.
                                                  # This isn't a problem so long as keepalived is reading all queued data from
                                                  # it's sockets, but if rmem_default was set sufficiently large, and if for
                                                  # some reason keepalived stopped reading, it could consume all system memory.
                                                  # The vrrp_rx_bufs_policy allows configuring of the rx bufs size when the
                                                  # sockets are opened. If the policy is MTU, the rx buf size is configured
                                                  # to the total of interface's MTU * vrrp_rx_bufs_multiplier for each vrrp
                                                  # instance using the socket. Likewise, if the policy is ADVERT, then it is
                                                  # the total of each vrrp instances advert packet size * multiplier.
                                                  # If policy is set to a number, the rx buf size is configured to that number.
        vrrp_rx_bufs_policy [MTU|ADVERT|NUMBER]   # default is to use system default
        vrrp_rx_bufs_multiplier NUMBER            # default 3
        rs_init_notifies                  # Send notifies at startup for real servers that are starting up
        no_checker_emails                         # Don't send an email every time a real server checker changes state;
                                                  #   only send email when a real server is added or removed
    }
    net_namespace NAME                            # 设置命名空间
                                                  # The directory /var/run/keepalived will be created as an unshared mount point,
                                                  #   for example for pid files.
                                                  # syslog entries will have _NAME appended to the ident.
                                                  # Note: the namespace cannot be changed on a configuration reload
    namespace_with_ipsets                         # ipsets wasn't network namespace aware until Linux 3.13, and so if running with
                                                  # an earlier version of the kernel, by default use of ipsets is disabled if using
                                                  # a namespace and vrrp_ipsets isn't specified.
                                                  # This options overrides the default and allows ipsets to be used
                                                  # with a namespace on kernels prior to 3.13.
    instance NAME                                 # 如果多个keepalived实例在相同的名称空间中运行，则会出现这种情况。在/var/run/keepalived中以名称作为文件名的一部分创建pid文件。注意:在重新加载配置时不能更改实例名
    use_pid_dir                                   # Create pid files in /var/run/keepalived
    linkbeat_use_polling                          # Use media link failure detection polling fashion
    child_wait_time SECS                          # Time for main process to allow for child processes to exit on termination
                                                  #   in seconds (default 5). This can be needed for very large configurations.

##### Static track groups #####

静态跟踪组用于允许vrrp实例跟踪静态地址路线和规则。如果一个静态地址/路由/规则指定了一个跟踪组，那么如果删除了地址/路由/规则，地址/路由/规则不能被重新添加的情况下，则vrrp实例将转换为备份或者故障状态
    track group的语法如下:
        track_group GROUP1 {
        
            group {
        
                VI_1
                VI_2
            }
        }

##### Static addresses #####

The configuration block looks like :
    static_ipaddress {
                                    # block identification
                                                  # 没有指定设备则默认用eth0
                                                  # track_group规范是指一个指定的track_group，它列出了将跟踪地址的vrrp实例，
                                                  # 即如果地址被删除且无法恢复，那么vrrp实例将转换为fault state。no_track意味着如果地址被删除，它将不会被恢复
                                                  # no_track意味着如果地址被删除，它将不会被恢复
                                                  # Note: the broadcast address may be specified as '-' or '+' to clear or set the host bits of the address.
        <IP ADDRESS>[/<MASK>] [brd <IP ADDRESS>] [dev <STRING>] [scope <SCOPE>] [label <LABEL>] [peer <IP ADDRESS>] [home] [-nodad] [mngtmpaddr] [noprefixroute] [autojoin] [track_group GROUP|no_track]
        <IP ADDRESS>[/<MASK>] ...
        ...
    
    }
    SCOPE can take the following values :
        * site
        * link
        * host
        * nowhere
        * global
    
    参考：doc/samples/keepalived.conf.vrrp.static_ipaddress

##### Static rules #####

static_rules {
                                        # block identification
                                                  # The syntax is that same as for ip rule add, without "ip rule add"
                                                  # with the addition of tunnel-id option (except shortened option names
                                                  #   aren't supported due to ambiguities).
                                                  # For a description of track_group and no_track, see static_addresses
                                                  # NOTE: since rules without preferences can be added in different orders
                                                  #   due to vrrp instances transitioning from master to backup etc, rules need
                                                  #   to have a preference. If a preference is not specified, keepalived will
                                                  #   assign one, but it will probably not be what you want.
        from 192.168.28.0/24 to 192.168.29.0/26 table small iif p33p1 oif wlan0 tos 22 fwmark 24/12 preference 39 realms 30/20 track_group GROUP1
        to 1:2:3:4:5:6:7:0/112 from 7:6:5:4:3:2::/96 table 6908 uidrange 10000-19999 no_track
        to 1:2:3:4:6:6:7:0/112 from 8:6:5:4:3:2::/96 l3mdev protocol 12 ip_proto UDP sport 10-20 dport 20-30
    }

##### Static routes #####

The configuration block looks like :
    static_routes {
                                       # block identification
                                                  # 语法类似于 ip route add, 只是没有 "ip route add"
                                                  #   (except shorted option names aren't supported due to ambiguities)
                                                  # For a description of track_group and no_track, see static_addresses
                                                  # Use "default" or "default6" to specify the default IPv4 or IPv6 route
        192.168.100.0/24 table 6909 nexthop via 192.168.101.1 dev wlan0 onlink weight 1 nexthop via 192.168.101.2 dev wlan0 onlink weight 2
        192.168.200.0/24 dev p33p1.2 table 6909 tos 0x04 protocol bird scope link priority 12 mtu 1000 hoplimit 100 advmss 101 rtt 102 rttvar 103 reordering 104 window 105 cwnd 106 ssthresh lock 107 realms PQA/0x14 rto_min 108 initcwnd 109 initrwnd 110 features ecn track_group GROUP1
        2001:470:69e9:1:2::4 dev p33p1.2 table 6909 tos 0x04 protocol bird scope link priority 12 mtu 1000 hoplimit 100 advmss 101 rtt 102 rttvar 103 reordering 104 window 105 cwnd 106 ssthresh lock 107 rto_min 108 initcwnd 109 initrwnd 110 features ecn fastopen_no_cookie 1 no_track
    }
    参考：doc/samples/keepalived.conf.vrrp.static_ipaddress

### VRRP configuration ###

This block is divided in 5 sub-blocks:
        * VRRP scripts
        * VRRP track files
        * VRRP track BFDs
        * VRRP synchronization group
        * VRRP gratuitous ARP/NA intervals
        * VRRP instance

##### VRRP scripts #####

The configuration block looks like :
    vrrp_script <STRING> {
                  # VRRP script declaration
        script <QUOTED_STRING>      # script to run periodically
        interval <INTEGER>          # run the script this every seconds
        timeout <INTEGER>           # script considered failed after 'timeout' seconds
        weight <INTEGER:-253..253>  # adjust priority by this weight
        fall <INTEGER>              # required number of failures for KO switch
        rise <INTEGER>              # required number of successes for OK switch
        user USERNAME [GROUPNAME]   # specify user/group to run script under
        init_fail                   # assume script initially is in failed state
    }
    脚本将周期性地执行，每隔<interval>秒执行一次。它的退出代码将被记录为所有监视它的VRRP实例。注意，只有在至少有一个VRRP实例监视脚本时，脚本才会被执行。默认权值等于0，这意味着监视脚本的任何VRRP实例在<fall>脚本连续失败后将转换到错误状态。之后，<rise>连续成功将导致VRRP实例离开错误状态，除非它们也由于正在跟踪的其他脚本或接口而处于错误状态。一个正的权重意味着<rise> success将把<weight>添加到监视它的所有VRRP实例的优先级。相反，如果<fall>失败，则从初始优先级中减去一个负值。
    
    说白就是，某个vrrp实例里面如果会周期性调用这个脚本，如果如果调用失败了就会把优先级减去相应的权值，成功了优先级就会增加相应的权值

##### VRRP track files #####

The configuration block looks like:
    vrrp_track_file <STRING> {
              # VRRP track file declaration
        file <QUOTED_STRING>        # file to monitor
        weight <-254..254>          # default weight (default is 1)
        init_file [VALUE] [overwrite] # create the file and/or initialise the value
                                    # This causes VALUE (default 0) to be written to
                                    # the specified file at startup if the file doesn't
                                    # exist, unless overwrite is specified in which case
                                    # any existing file contents will be overwritten with
                                    # the specified value.
    }
    
    The file will be read whenever it is modified. The value in the file
    will be recorded for all VRRP instances and sync groups which monitor it.
    Note that the file will only be read if at least one VRRP instance or
    sync group monitors it.
    A value will be read as a number in text from the file.  If the weight
    configured against the track_file is 0, a non-zero value in the file will
    be treated as a failure status, and a zero value will be treated as
    an OK status, otherwise the value will be  multiplied by the weight configured
    in the track_file statement. If the result is less than -253 any VRRP
    instance or sync group monitoring the script will transition to the fault state
    (the weight can be 254 to allow for a negative value being read from the file).
    If the vrrp instance or sync group is not the address owner and the result is between
    -253 and 253, the result will be added to the initial priority of the VRRP instance
    (a negative value will reduce the priority), although the effective priority will
    be limited to the range [1,254].
    If a vrrp instance using a track_file is a member of a sync group, unless
    sync_group_tracking_weight is set on the group weight 0 must be set.
    Likewise, if the vrrp instance is the address owner, weight 0 must also be set.

##### BFD Configuration #####

This is an implementation of RFC5880 (Bidirectional forwarding detection),
        and this can be configured to work between 2 keepalived instances, but using
        unweighted track_bfds between a master/backup pair of VRRP instances means that
        the VRRP instance will only be able to come up if both VRRP instance are running,
        which somewhat defeats the purpose of VRRP.
        This imlpementation has been tested with OpenBFDD (available at
        https://github.com/dyninc/OpenBFDD).
        The configuration block looks like :
    bfd_instance <STRING> {
        
        neighbor_ip <IP ADDRESS>           # BFD Neighbor IP (synonym neighbour_ip)
        source_ip <IP ADDRESS>             # Source IP to use (optional)
        mix_rx <INTEGER>                   # Required min RX interval, in ms
                                           # (default is 10 ms)
        min_tx <INTEGER>                   # Desired min TX interval, in ms
                                           # (default is 10 ms)
        idle_tx <INTEGER>                  # Desired idle TX interval, in ms
                                           # (default is 1000 ms)
        multiplier <INTEGER>               # Number of missed packets after
                                           # which the session is declared down
                                           # (default is 5)
        passive                            # Operate in passive mode (default is active)
        ttl <INTEGER 0..255>               # outgoing IPv4 ttl to use (default 255)
        hoplimit <INTEGER 0..255>          # outgoing IPv6 hoplimit to use (default 64)
        max_hops <INTEGER 0..255>          # maximum reduction of ttl/hoplimit in received packet (default 0)
                                           #   (255 disables hop count checking)
        weight                             # Default tracking weight
        vrrp|checker                       # Only notify vrrp or checker process. Default is notify both.
    }

##### VRRP synchronization group #####

The configuration block looks like :
    vrrp_sync_group <STRING> {
              # VRRP sync group declaration
        group {
                             # group of instance to sync together
          <STRING>                  #   a
          <STRING>                  #       set
          ...                       #             of VRRP_Instance string
        }
        global_tracking             # DEPRECATED. Use track_interface, track_script and
                                    # track_file on vrrp_sync_groups instead.
        sync_group_tracking_weight  # allow sync groups to use differing weights. This
                                    # probably WON'T WORK, but is a replacement for
                                    # global_tracking in case different weights were used
                                    # across different vrrp instances in the same sync
                                    # group.
        track_interface {
                   # 如果下列接口有挂了的就把该实例状态设置为fault
          <STRING>
          <STRING>
          <STRING> weight <INTEGER:-253..253>
          ...
        }
        track_script {
                      # Scripts state we monitor
          <STRING>
          <STRING> weight <INTEGER:-253..253>
          ...
        }
        track_file {
                        # Files state we monitor
          <STRING>          # weight defaults to value configured in the vrrp_track_file
          <STRING> weight <INTEGER: -254..254>
          ...
        }
        track_bfd {
                         # BFD instance we monitor
          <STRING>
          <STRING>
          <STRING> weight <INTEGER: -253..253>
          ...
        }
                                    # The username and groupname specify the user and group
                                    # under which the scripts should be run. If username is
                                    # specified, the group defaults to the group of the user.
                                    # If username is not specified, they default to the
                                    # global script_user and script_group
        notify_master <STRING>|<QUOTED-STRING> [username [groupname]]
                                    # Script to run during MASTER transit
        notify_backup <STRING>|<QUOTED-STRING> [username [groupname]]
                                    # Script to run during BACKUP transit
        notify_fault <STRING>|<QUOTED-STRING> [username [groupname]]
                                    # Script to run during FAULT transit
        notify_stop <STRING>|<QUOTED-STRING> [username [groupname]]
                                    # Script to launch when stopping vrrp
        notify <STRING>|<QUOTED-STRING> [username [groupname]]
                                    # Script to run during ANY state transit (1)
        smtp_alert <BOOL>           # Send email notification during state transit
                                    #   (default no, unless global smtp_alert/smtp_alert_vrrp set)
    }
        Synchronization group tracking scripts and files will update
        the status/priority of all VRRP instances which are members of
        the sync group.
    (1) The "notify" script is called AFTER the corresponding notify_* script has
        been called, and is given 4 additional arguments following the configured
        arguments:
        $(n-3) = A string indicating whether it's a "GROUP" or an "INSTANCE"
        $(n-2) = The name of said group or instance
        $(n-1) = The state it's transitioning to ("MASTER", "BACKUP", "FAULT" or "STOP")
        $(n)   = The priority value
        $(n-3) and $(n-1) are ALWAYS sent in uppercase, and the possible strings sent are the
        same ones listed above ("GROUP"/"INSTANCE", "MASTER"/"BACKUP"/"FAULT"/"STOP")
        (note: STOP is only applicable to instances)
    Important: for a SYNC group to run reliably, it is vital that all instances in
               the group are MASTER or that they are all either BACKUP or FAULT. A
               situation with half instances having higher priority on machine A
               half others with higher priority on machine B will lead to constant
               re-elections. For this reason, when instances are grouped, any
               track scripts/files configured against member VRRP instances will have
               their tracking weights automatically set to zero, in order to avoid
               inconsistent priorities across instances.
    (2) The notify fifo output is the same as the last 4 parameters for the "notify"
        script, with the addition of "MASTER_RX_LOWER_PRI" instead of state for an
        instance. This is used if a master needs to set some external state, such as
        setting a secondary IP address when using Amazon AWS; if another keepalived
        has transitioned to master due to a communications break, the lower priority
        instance will have taken over the secondary IP address, and the proper master
        needs to be able to restore it.
    ##### VRRP gratuitous ARP/NA intervals
    ```bash
        This section allows the setting of delays between sending gratuitous ARPs
        and unsolicited neighbour advertisements. This is intended for when an
        upstream switch is unable to handle being flooded with ARPs/NAs.
        Use interface when the limits apply on the single physical interface.
        Use interfaces when a group of interfaces are linked to the same switch
        and the limits apply to the switch as a whole.
        Note: Only one of interface or interfaces should be used per block.
    garp_group {
        
        garp_interval <DECIMAL>     # Sets the interval between Gratuitous ARP
                                    #   (in seconds, resolution microseconds)
        gna_interval <DECIMAL>      # Sets the default interval between unsolicited NA
                                    #   (in seconds, resolution microseconds)
        interface <STRING>          # The physical interface to which the intervals apply
        interfaces {
                        # A list of interfaces across which the delays are
            <STRING>                #   aggregated.
            <STRING>
            ...
        }
    }
        If the global vrrp_garp_interval and/or vrrp_gna_interval are set, any
        interfaces that aren't specified in a garp_group will inherit the global
        settings.

##### VRRP instance #####

The configuration block looks like :
    vrrp_instance <STRING> {
                              # VRRP instance declaration
        use_vmac [<NAME>]                         # Use VRRP Virtual MAC, optional NAME of interface
                                                  # NOTE: If sysctl net.ipv4.conf.all.rp_filter is set,
                                                  # and this vrrp_instance is an IPv4 instance, using
                                                  # this option will cause the individual interfaces to be
                                                  # updated to the greater of their current setting and
                                                  # all.rp_filter, as will default.rp_filter, and all.rp_filter
                                                  # will be set to 0.
                                                  # The original settings are restored on termination.
        version <INTEGER:2..3>                    # VRRP version to use
        vmac_xmit_base                            # Send/Recv VRRP messages from base
                                                  #  interface instead of VMAC interface
        native_ipv6                               # Force instance to use IPv6 (this option is deprecated since
                                                  #   the virtual addresses determine whether IPv4 or IPv6 is used)
        state MASTER|BACKUP                       # Start-up default state
        interface <STRING>                        # Binding interface
        accept                                    # Allow a non address-owner to process packets
                                                  # destined to VIPs and eVIPs. This is the default
                                                  # unless strict mode is set.
        no_accept                                 # Set non-accept mode (default if strict mode)
                                                  #
        skip_check_adv_addr [BOOL]                # See description of global vrrp_skip_check_adv_addr, which
                                                  # sets the default value. Defaults to vrrp_skip_check_adv_addr
        track_interface {
                                 # Interfaces state we monitor
          <STRING>
          <STRING>
          <STRING> weight <INTEGER:-253..253>
          ...
        }
        track_script {
                                    # Scripts state we monitor
          <STRING>
          <STRING> weight <INTEGER:-253..253>
          ...
        }
        track_file {
                                      # Files state we monitor
          <STRING>
          <STRING>
          <STRING> weight <INTEGER: -254..254>
          ...
        }
        track_bfd {
                                       # BFD instance we monitor
          <STRING>
          <STRING>
          <STRING> weight <INTEGER: -253..253>
          ...
        }
        dont_track_primary                        # (default unset) ignore VRRP interface faults.
                                                  #  useful for cross-connect VRRP config.
        mcast_src_ip <IP ADDRESS>                 # src_ip to use into the VRRP packets
        unicast_src_ip <IP ADDRESS>               # src_ip to use into the VRRP packets (alias to mcast_src_ip)
        track_src_ip                              # if the configured src_ip doesn't exist or is removed
                                                  # put the instance into fault state
        unicast_peer {
                                    # Do not use multicast, instead send VRRP
          <IP ADDRESS>                            #  adverts to following list of ip address
          ...                                     #  in unicast design fashion
        }
        old_unicast_checksum [never]              # The checksum calculation when using VRRPv3 changed after v1.3.6.
                                                  #  Setting this flag forces the old checksum algorithm to be used
                                                  #  to maintain backward compatibility, although keepalived will
                                                  #  attempt to maintain compatibility anyway if it sees an old
                                                  #  version checksum. Specifying never will turn off autodetection
                                                  #  of old checksums. [This option may not be enabled - check output
                                                  #  of `keepalived -v` for OLD_CHKSUM_COMPAT.]
        # The following garp parameters take their defaults from the global config for vrrp_garp_...
        # See their descriptions for the meaning of the parameters.
        garp_master_delay <INTEGER>
        garp_master_repeat <INTEGER>
        garp_lower_priority_delay <INTEGER>
        garp_lower_priority_repeat <INTEGER>
        garp_master_refresh <INTEGER>
        garp_master_refresh_repeat <INTEGER>
        virtual_router_id <INTEGER-1..255>        # VRRP VRID
        priority <INTEGER-1..255>                 # VRRP PRIO
        advert_int <FLOAT>                        # VRRP Advert interval (use default)
        lower_prio_no_advert [<BOOL>]             # If a lower priority advert is received, don't
                                                  # send another advert. This causes adherence
                                                  # to the RFCs (defaults to global
                                                  # vrrp_lower_priority_dont_send_advert).
        higher_prio_send_advert [<BOOL>]          # If we are master and receive a higher priority
                                                  # advert, send an advert (which will be lower priority
                                                  # than the other master), before we transition to
                                                  # backup. This means that if the other master has
                                                  # garp_lower_priority_repeat set, it will resend garp
                                                  # messages. This is to get around the problem of their
                                                  # having been two simultaneous masters, and the last GARP
                                                  # messages seen were from us.
        # Note: authentication was removed from the VRRPv2 specification by RFC3768 in 2004.
        #   Use of this option is non-compliant and can cause problems; avoid using if possible,
        #   except when using unicast, when it can be helpful.
        authentication {
                                  # Authentication block
            auth_type PASS|AH                     # Simple password or IPSEC AH
            auth_pass <STRING>                    # Password string (up to 8 characters)
        }
        # For virutal_ipaddress and virtual_ipaddress_excluded most of the options match the options
        #   of the command ip address add, likewise for virtual_routes and virtual_rules and the
        #   respective ip route/rule add commands. no_track is specific to keepalived and means that the
        #   vrrp_instance will not transition out of master state if the address/route/rule is deleted
        #   and the address/route/rule will not be reinstated until the vrrp instance next transitions
        #   to master.
        # The track_group option only applies to static addresses/routes/rules.
        virtual_ipaddress {
                               # VRRP IP addres block
            <IP ADDRESS>[/<MASK>] [brd <IP ADDRESS>] [dev <STRING>] [scope <SCOPE>] [label <LABEL>] [peer <IP ADDRESS>] [home] [-nodad] [mngtmpaddr] [noprefixroute] [autojoin] [no_track]
            <IP ADDRESS>[/<MASK>] ...
            ...
        }
        virtual_ipaddress_excluded {
                      # VRRP IP excluded from VRRP packets
            <IP ADDRESS>[/<MASK>] [brd <IP ADDRESS>] [dev <STRING>] [scope <SCOPE>] [label <LABEL>] [peer <IP ADDRESS>] [home] [-nodad] [mngtmpaddr] [noprefixroute] [autojoin] [no_track]
            <IP ADDRESS>[/<MASK>] ...
            ...
        }
        promote_secondaries                       # Set the promote_secondaries flag on the interface to stop other
                                                  # addresses in the same CIDR being removed when 1 of them is removed
        virtual_routes {
                                  # VRRP virtual routes
                                                  # The syntax is the same as static_routes with the additional option [no_track]
                                                  #   and excluding track_group.
        }
        virtual_rules {
                                   # VRRP virtual rules
                                                  # The syntax is the same as static_rules with the additional option [no_track]
                                                  #   and excluding track_group.
        }
        nopreempt                                 # Override VRRP RFC preemption default
        preempt_delay <FLOAT>                     # Seconds after startup or seeing a lower priority master
                                                  #  until preemption. 0 (default) to 1,000
        strict_mode [<BOOL>]                      # See description of global vrrp_strict
                                                  # If vrrp_strict is not specified, it takes the value of vrrp_strict
                                                  # If strict_mode without a parameter is specified, it defaults to on
        debug <LEVEL>                             # Debug level. LEVEL is a number in the range 0 to 4.
        notify_master <STRING>|<QUOTED-STRING> [username [groupname]]
                                                  # Same as vrrp_sync_group
        notify_backup <STRING>|<QUOTED-STRING> [username [groupname]]
                                                  # Same as vrrp_sync_group
        notify_fault <STRING>|<QUOTED-STRING> [username [groupname]]
                                                  # Same as vrrp_sync_group
        notify_stop <STRING>|<QUOTED-STRING> [username [groupname]]
                                                  # Script to launch when stopping vrrp
        notify <STRING>|<QUOTED-STRING> [username [groupname]]
                                                  # Same as vrrp_sync_group
        notify_master_rx_lower_pri <STRING>|<QUOTED-STRING> [username [groupname]]
                                                  # Script to run if a master receives a lower priority advert
        smtp_alert <BOOL>                         # Same as vrrp_sync_group
                                                  #   (default no, unless global smtp_alert/smtp_alert_vrrp set)
        kernel_rx_buf_size                        # Set socket receive buffer size (see global_defs
                                                  #   vrrp_rx_bufs_policy for explanation)
    }
    SCOPE can take the following values :
        * site
        * link
        * host
        * nowhere
        * global
    LABEL is optional and creates a name for the alias. For compatibility with
    "ifconfig", it should be of the form <realdev>:<anytext>, for example
    eth0:1 for an alias on eth0.
    METRIC is optional and specify a route priority.
    When a weight is specified in track_interface, instead of setting the vrrp
    instance to the FAULT state in case of failure, its priority will be
    increased by the weight when the interface is up (for positive weights),
    or decreased by the weight's absolute value when the interface is down
    (for negative weights). The weight must be comprised between -254 and +254
    inclusive. 0 is the default behaviour which means that a failure implies a
    FAULT state. The common practice is to use positive weights to count a
    limited number of good services so that the server with the highest count
    becomes master. Negative weights are better to count unexpected failures
    among a high number of interfaces, as it will not saturate even with high
    number of interfaces.
    The same principle can be applied to track_script entries, except that an
    unspecified weight means that the default weight declared in the script
    will be used (which itself defaults to 0).

### LVS configuration ###

This block is divided in 2 sub-block :
        * Virtual server group
        * Virtual server
        * SSL config

##### Virtual server group #####

The configuration block looks like :
    virtual_server_group <STRING> {
        
        <IP ADDRESS> <PORT>         # VIP VPORT
        <IP ADDRESS> <PORT>
        ...
        <IP ADDRESS RANGE> <PORT>   # VIP range VPORT
        <IP ADDRESS RANGE> <PORT>
        ...
        fwmark <INTEGER>            # fwmark
        fwmark <INTEGER>
        ...
    }
    Note:   <IP ADDRESS RANGE> has the form of : XXX.YYY.ZZZ.WWW-VVV, define
            the IP address range starting at WWW and monotonaly incremented by
            one to VVV. Example : 192.168.200.1-10 means .1 to .10 IP addresses.

##### Virtual server #####

The configuration block looks like :
        A virtual_server can be either :
        * vip vport declaration
        * fwmark declaration
        * group declaration
        Note: Where an option can be configured for a virtual server, real server,
        and possibly checker, the virtual server setting is the default for real servers,
        and the real server setting is the default for checkers.
        Note 2: Tunnelled real/sorry servers can differ from the address family of
        the virtual server and non tunnelled real/sorry servers, which all have to be the
        same. If a virtual server uses a fwmark, and all the real/sorry servers are
        tunnelled, the address family of the virtual server will be the same as the
        address family of the real/sorry servers if they are all the same, otherwise
        it will default to IPv4 (use ip_family inet6 to override this).
    virtual_server <IP ADDRESS> <PORT> {
                  # VS IP/PORT declaration
    virtual_server fwmark <INTEGER>    {
                  # VS fwmark declaration
    virtual_server group <STRING>      {
                  # VS group declaration
        ip_family inet|inet6                      # Address family
        delay_loop <INTEGER>                      # delay timer for service polling
        lvs_sched rr|wrr|lc|wlc|lblc|sh|dh|fo|ovf|lblcr|sed|nq
                                                  # LVS scheduler used
        hashed                                    # Apply hashing
        flag-1                                    # Apply scheduler flag 1
        flag-2                                    # Apply scheduler flag 2
        flag-3                                    # Apply scheduler flag 3
        sh-port                                   # Apply sh-port scheduler flag (only for sh scheduler,
                                                  #  same as flag-2 for sh scheduler)
        sh-fallback                               # Apply sh-fallback scheduler flag (only for sh scheduler,
                                                  #  same as flag-1 for sh scheduler)
        ops                                       # Apply One-Packet-Scheduling (only for UDP)
        lvs_method NAT|DR|TUN                     # default LVS method to use
        persistence_engine <STRING>               # LVS persistence engine name
        persistence_timeout [<INTEGER>]           # LVS persistence timeout, default 6 minutes
        persistence_granularity <NETMASK>         # LVS granularity mask
        protocol TCP|UDP|SCTP                     # L4 protocol
        ha_suspend                                # If VS IP address is not set, suspend
                                                  #  healthcheckers activity
        virtualhost <STRING>                      # Default VirtualHost string to use for
                                                  #  HTTP_GET or SSL_GET
        # Assume silently all RSs down and healthchecks
        # failed on start. This helps preventing false
        # positive actions on startup. Alpha mode is
        # disabled by default.
        alpha
        # On daemon shutdown, consider quorum and RS
        # down notifiers for execution, where appropriate.
        # Omega mode is disabled by default.
        omega
        # Minimum total weight of all live servers in
        # the pool necessary to operate VS with no
        # quality regression. Defaults to 1.
        quorum <INT>
        # Tolerate this much weight units compared to the
        # nominal quorum, when considering quorum gain
        # or loss. A flap dampener. Defaults to 0.
        hysteresis <INT>
        # Script to launch when quorum is gained.
        quorum_up <STRING>|<QUOTED-STRING> [username [groupname]]
        # Script to launch when quorum is lost.
        quorum_down <STRING>|<QUOTED-STRING> [username [groupname]]
        sorry_server <IP ADDRESS> <PORT>          # RS to add to LVS topology when the
                                                  #  quorum isn't achieved.
                                                  #  If a sorry server is configured, all
                                                  #  real servers will be brought down when
                                                  #  the quorum is not achieved.
        sorry_server_inhibit                      # applies inhibit_on_failure behaviour
                                                  # to the sorry_server
        sorry_server_lvs_method NAT|DR|TUN        # LVS method to use for sorry server
        retry <INTEGER>                           # number of retries before fail
        delay_before_retry <INTEGER>              # delay before retry (default 1 unless otherwise specified)
        warmup <INTEGER>                          # random delay for maximum N seconds
        delay_loop <INTEGER>                      # delay timer for service polling
        inhibit_on_failure                        # Set weight to 0 on healthchecker failure
        smtp_alert <BOOL>                         # Send email notification when quorum gained/lost
                                                  #   (default no, unless global smtp_alert/smtp_alert_checker set)
        real_server <IP ADDRESS> <PORT> {
                 # RS declaration
            weight <INTEGER>                      # weight to use (default: 1)
            lvs_method NAT|DR|TUN                 # LVS method to use
            notify_up <STRING>|<QUOTED-STRING> [username [groupname]]
                                                  # Script to launch when
                                                  #  healthchecker consider service
                                                  #  as up.
            notify_down <STRING>|<QUOTED-STRING> [username [groupname]]
                                                  # Script to launch when
                                                  #  healthchecker consider service
                                                  #  as down.
            uthreshold <INTEGER>                  # maximum number of connections to server
            lthreshold <INTEGER>                  # minimum number of connections to server
            alpha <BOOL>                          # see above
            retry <INTEGER>                       # see above
            delay_before_retry <INTEGER>          # see above
            warmup <INTEGER>                      # see above
            delay_loop <INTEGER>                  # see above
            inhibit_on_failure <BOOL>             # see above
            smtp_alert <BOOL>                     # Send email notification when quorum gained/lost
                                                  #   (default yes, unless global smtp_alert/smtp_alert_checker set)
            virtualhost <STRING>                  # Default VirtualHost string to use for
                                                  #  HTTP_GET or SSL_GET (overrides
                                                  #  virtual_server virtualhost)
            # healthcheckers. Can be multiple of each type
            # HTTP_GET|SSL_GET|TCP_CHECK|SMTP_CHECK|DNS_CHECK|MISC_CHECK|BFD_CHECK
            # All checkers have the following options, except MISC_CHECK which only has alpha onwards,
        #  and BFD_CHECK which has no standard options:
            CHECKER_TYPE {
        
                connect_ip <IP ADDRESS>           # IP address to connect (default real_server address)
                connect_port <PORT>               # Port to connect (default real_server port)
                bindto <IP ADDRESS>               # IP address to bind to
                bind_if <IFNAME>                  # Interface to bind to; needed if the bindto
                                                  #  address is IPv6 link local
                bind_port <PORT>                  # Port to bind to
                connect_timeout <INTEGER>         # Timeout connection
                fwmark <INTEGER>                  # fwmark to set on socket (SO_MARK)
                alpha <BOOL>                      # see above
                retry <INTEGER>                   # number of retries before fail
                delay_before_retry <INTEGER>      # delay before retry (default 1 unless otherwise specified)
                warmup <INTEGER>                  # random delay for maximum N seconds
                delay_loop <INTEGER>              # delay timer for service polling
            }
            # The following options are additional checker specific
            HTTP_GET|SSL_GET {
                            # HTTP and SSL healthcheckers
                url {
                                     # A set of url to test
                  path <STRING>                   # Path
                  digest <STRING>                 # Digest computed with genhash
                  status_code <INTEGER>           # status code returned into the HTTP
                                                  #   header. If not specified, then any
                                                  #   2xx code is accepted.
                  virtualhost <STRING>            # VirtualHost string to use. If not set
                                                  #  uses virtualhost from checker or real
                                                  #  or virtual_server.
                }
                url {
        
                  path <STRING>
                  digest <STRING>
                  status_code <INTEGER>
                  virtualhost <STRING>
                }
                ...
                virtualhost <STRING>              # VirtualHost string to use. If not set
                                                  #  uses virtualhost from real or
                                                  #  virtual_server.
            }
            SSL_GET {
        
                enable_sni            # send Server Name Indication during SSL handshake
            }
            TCP_CHECK {
                                   # TCP healthchecker
                # No additional options
            }
            SMTP_CHECK {
                                  # SMTP healthchecker
                helo_name <STRING>|<QUOTED-STRING> # Host to use for the HELO request
            }
            DNS_CHECK {
                                   # DNS healthchecker
                type A|NS|CNAME|SOA|MX|TXT|AAAA   # DNS query type (default SOA)
                name <STRING>                     # Domain name to use for the DNS query
            }
            MISC_CHECK {
                                  # MISC healthchecker
                misc_path <STRING>|<QUOTED-STRING> # External system script or program
                misc_timeout <INTEGER>            # Script execution timeout
                # If set, exit code from healthchecker is used
                # to dynamically adjust the weight as follows:
                #   exit status 0: svc check success, weight
                #     unchanged.
                #   exit status 1: svc check failed.
                #   exit status 2-255: svc check success, weight
                #     changed to 2 less than exit status.
                #   (for example: exit status of 255 would set
                #     weight to 253)
                # NOTE: do not have more than one dynamic MISC_CHECK per real_server.
                misc_dynamic
                user USERNAME [GROUPNAME]         # Specify user/group to run script under
            }
            BFD_CHECK {
        
                name <STRING>                     # the name of the bfd instance
            }
        }
    }

##### SSL config #####

Parameters used for SSL_GET check.
        If none of the parameters is specified, the SSL context will be auto generated.
    SSL {
        
        password <STRING>           # password
        ca <STRING>                 # ca file
        certificate <STRING>        # certificate file
        key <STRING>                # key file
    }

[https_github.com_acassen_keepalived_blob_master_doc_keepalived.conf.SYNOPSIS]: https://github.com/acassen/keepalived/blob/master/doc/keepalived.conf.SYNOPSIS