snmp_exporter解析mib原理

snmp_exporter

创建mib文件目录,下载mib文件

make all

首先从给定的uri中下载mib文件

解析mib文件

./generator generate

解析根据generator.yml规则,从MIB目录中生成snmp.yml格式文件

原理

net_snmp.go文件中使用了C库中net-snmp/net-snmp-config.h,net-snmp/mib_api.h
处理原始mib文件

C.netsnmp_init_mib解析MIB文件

C.get_tree_head()获取C.struct_tree

buildMIBTree(递归)函数将C.struct_tree转换成go的tree存储

生成配置文件

export MIBDIRS=mibs
./generator generate

生成器从 generator.yml 读取并写入 snmp.yml。
其他命令可用于调试,help 命令查看。

文件格式

generator.yml 提供模块列表。最简单的模块只是一个名称和一组要遍历的 OID。

modules:
  module_name:  # The module name. You can have as many modules as you want.
    walk:       # List of OIDs to walk. Can also be SNMP object names or specific instances.
      - 1.3.6.1.2.1.2              # Same as "interfaces"
      - sysUpTime                  # Same as "1.3.6.1.2.1.1.3"
      - 1.3.6.1.2.1.31.1.1.1.6.40  # Instance of "ifHCInOctets" with index "40"

    version: 2  # SNMP version to use. Defaults to 2.
                # 1 will use GETNEXT, 2 and 3 use GETBULK.
    max_repetitions: 25  # How many objects to request with GET/GETBULK, defaults to 25.
                         # May need to be reduced for buggy devices.
    retries: 3   # How many times to retry a failed request, defaults to 3.
    timeout: 10s # Timeout for each walk, defaults to 10s.

    auth:
      # Community string is used with SNMP v1 and v2. Defaults to "public".
      community: public

      # v3 has different and more complex settings.
      # Which are required depends on the security_level.
      # The equivalent options on NetSNMP commands like snmpbulkwalk
      # and snmpget are also listed. See snmpcmd(1).
      username: user  # Required, no default. -u option to NetSNMP.
      security_level: noAuthNoPriv  # Defaults to noAuthNoPriv. -l option to NetSNMP.
                                    # Can be noAuthNoPriv, authNoPriv or authPriv.
      password: pass  # Has no default. Also known as authKey, -A option to NetSNMP.
                      # Required if security_level is authNoPriv or authPriv.
      auth_protocol: MD5  # MD5 or SHA, defaults to MD5. -a option to NetSNMP.
                          # Used if security_level is authNoPriv or authPriv.
      priv_protocol: DES  # DES or AES, defaults to DES. -x option to NetSNMP.
                          # Used if security_level is authPriv.
      priv_password: otherPass # Has no default. Also known as privKey, -X option to NetSNMP.
                               # Required if security_level is authPriv.
      context_name: context # Has no default. -n option to NetSNMP.
                            # Required if context is configured on the device.

    lookups:  # Optional list of lookups to perform.
              # The default for `keep_source_indexes` is false. Indexes must be unique for this option to be used.

      # If the index of a table is bsnDot11EssIndex, usually that'd be the label
      # on the resulting metrics from that table. Instead, use the index to
      # lookup the bsnDot11EssSsid table entry and create a bsnDot11EssSsid label
      # with that value.
      - source_indexes: [bsnDot11EssIndex]
        lookup: bsnDot11EssSsid
        drop_source_indexes: false  # If true, delete source index labels for this lookup.
                                    # This avoids label clutter when the new index is unique.

     overrides: # Allows for per-module overrides of bits of MIBs
       metricName:
         ignore: true # Drops the metric from the output.
         regex_extracts:
           Temp: # A new metric will be created appending this to the metricName to become metricNameTemp.
             - regex: '(.*)' # Regex to extract a value from the returned SNMP walks's value.
               value: '$1' # The result will be parsed as a float64, defaults to $1.
           Status:
             - regex: '.*Example'
               value: '1'
             - regex: '.*'
               value: '0'
         type: DisplayString # Override the metric type, possible types are:
                             #   gauge:   An integer with type gauge.
                             #   counter: An integer with type counter.
                             #   OctetString: A bit string, rendered as 0xff34.
                             #   DateAndTime: An RFC 2579 DateAndTime byte sequence. If the device has no time zone data, UTC is used.
                             #   DisplayString: An ASCII or UTF-8 string.
                             #   PhysAddress48: A 48 bit MAC address, rendered as 00:01:02:03:04:ff.
                             #   Float: A 32 bit floating-point value with type gauge.
                             #   Double: A 64 bit floating-point value with type gauge.
                             #   InetAddressIPv4: An IPv4 address, rendered as 1.2.3.4.
                             #   InetAddressIPv6: An IPv6 address, rendered as 0102:0304:0506:0708:090A:0B0C:0D0E:0F10.
                             #   InetAddress: An InetAddress per RFC 4001. Must be preceded by an InetAddressType.
                             #   InetAddressMissingSize: An InetAddress that violates section 4.1 of RFC 4001 by
                             #       not having the size in the index. Must be preceded by an InetAddressType.
                             #   EnumAsInfo: An enum for which a single timeseries is created. Good for constant values.
                             #   EnumAsStateSet: An enum with a time series per state. Good for variable low-cardinality enums.