背景：
现阶段手头的一个自研的流式计算平台在完善监控体系，对机器资源负载、机器上任务资源消耗进行统计和上报，这里对Linux下获取网卡上限的方法进行梳理。
说明：这里的网卡最大带宽指的是物理网卡的带宽最大值
现阶段是使用系统提供的命令ethtool获取网卡最大值，具体命令如下：
ethtool eth1 | grep Speed
//1000M网卡机器中，ethtool命令的执行结果：
[root@WSC-155-91 ~]# ethtool eth1
Settings for eth1:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Advertised pause frame use: Symmetric
Advertised auto-negotiation: Yes
Speed: 1000Mb/s // 网卡流速上限
Duplex: Full
Port: Twisted Pair
PHYAD: 1
Transceiver: internal
Auto-negotiation: on
MDI-X: off
Supports Wake-on: pumbg
Wake-on: g
Current message level: 0x00000007 (7)
Link detected: yes
[root@WSC-155-91 ~]# ethtool eth1 | grep Speed
Speed: 1000Mb/s
-------------------------------------------------------------------------------------
//10000M网卡机器中，ethtool命令的执行结果：
[root@WSC-32-134 ~]# ethtool eth1
Settings for eth1:
Supported ports: [ TP ]
Supported link modes: 100baseT/Full
1000baseT/Full
10000baseT/Full
Supported pause frame use: No
Supports auto-negotiation: Yes
Advertised link modes: 100baseT/Full
1000baseT/Full
10000baseT/Full
Advertised pause frame use: Symmetric
Advertised auto-negotiation: Yes
Speed: 10000Mb/s // 网卡流速上限
Duplex: Full
Port: Twisted Pair
PHYAD: 0
Transceiver: external
Auto-negotiation: on
MDI-X: Unknown
Supports Wake-on: umbg
Wake-on: g
Current message level: 0x00000007 (7)
drv probe link
Link detected: yes
[root@WSC-32-134 ~]# ethtool eth1 | grep Speed
Speed: 10000Mb/s