获取远程IP地址的替代方法，不用抓取netstat？

Question

我现在在Linux上使用netstat -n -A inet命令，和在Mac OSX上使用netstat -n -f inet命令，来抓取机器连接的远程IP地址和端口。我用的是下面这个（Python默认的）正则表达式：

'(?:[0-9]+\.){3}[0-9]+[.:][0-9]+\s+((?:[0-9]+\.){3}[0-9]+)[.:]([0-9]+)'

这个正则表达式能让我在第一个组里得到远程IP，在第二个组里得到远程端口。

不过，这种方法似乎不够灵活，也不容易维护（而且只适用于IPv4地址）。

有没有更好的方法来获取活动的远程IP列表呢？

Answer 1

如果你对C语言和U*X的内部结构不感到害怕的话，可以尝试对netstat进行逆向工程。

你可以在这里查看相关内容 https://unix.stackexchange.com/questions/21503/source-code-of-netstat

Answer 2

嗯，总是可以用SNMP来解决这个问题……完整的TCP连接表在.1.3.6.1.2.1.6.19（也叫做.iso.org.dod.internet.mgmt.mib-2.tcp.tcpConnectionTable），而完整的UDP表在.1.3.6.1.2.1.7.7（也叫做.iso.org.dod.internet.mgmt.mib-2.udp.udpEndpointTable）。

这里有一个我本地Linux机器的例子：

$ snmpbulkwalk -v2c -c xxxx -m ALL 83.137.17.100 .iso.org.dod.internet.mgmt.mib-2.tcp.tcpConnectionTable
TCP-MIB::tcpConnectionState.ipv4."83.137.17.100".44463.ipv4."91.189.89.90".80 = INTEGER: timeWait(11)
TCP-MIB::tcpConnectionState.ipv4."83.137.17.100".44470.ipv4."91.189.89.90".80 = INTEGER: timeWait(11)
TCP-MIB::tcpConnectionState.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:89:11:64".80.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:55:f2:7b".51612 = INTEGER: timeWait(11)
TCP-MIB::tcpConnectionState.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:89:11:64".80.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:55:f2:7b".51622 = INTEGER: timeWait(11)
TCP-MIB::tcpConnectionState.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:89:11:64".80.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:55:f2:7b".51623 = INTEGER: timeWait(11)
TCP-MIB::tcpConnectionState.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:89:11:64".80.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:55:f2:7b".51624 = INTEGER: finWait2(7)
TCP-MIB::tcpConnectionState.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:89:11:64".80.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:f7:0a:da".59728 = INTEGER: timeWait(11)
TCP-MIB::tcpConnectionState.ipv6."20:01:40:38:00:00:00:16:00:00:00:00:00:00:00:16".22.ipv6."2a:00:86:40:00:01:00:00:54:f4:06:96:6c:48:aa:a9".49644 = INTEGER: established(5)
TCP-MIB::tcpConnectionProcess.ipv4."83.137.17.100".44463.ipv4."91.189.89.90".80 = Gauge32: 0
TCP-MIB::tcpConnectionProcess.ipv4."83.137.17.100".44470.ipv4."91.189.89.90".80 = Gauge32: 0
TCP-MIB::tcpConnectionProcess.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:89:11:64".80.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:55:f2:7b".51612 = Gauge32: 0
TCP-MIB::tcpConnectionProcess.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:89:11:64".80.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:55:f2:7b".51622 = Gauge32: 0
TCP-MIB::tcpConnectionProcess.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:89:11:64".80.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:55:f2:7b".51623 = Gauge32: 0
TCP-MIB::tcpConnectionProcess.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:89:11:64".80.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:55:f2:7b".51624 = Gauge32: 0
TCP-MIB::tcpConnectionProcess.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:89:11:64".80.ipv6."00:00:00:00:00:00:00:00:00:00:ff:ff:53:f7:0a:da".59728 = Gauge32: 0
TCP-MIB::tcpConnectionProcess.ipv6."20:01:40:38:00:00:00:16:00:00:00:00:00:00:00:16".22.ipv6."2a:00:86:40:00:01:00:00:54:f4:06:96:6c:48:aa:a9".49644 = Gauge32: 0

Net-SNMP工具可以让输出结果看起来更容易理解。用数字形式表示，第一行输出会是：

1.3.6.1.2.1.6.19.1.7.1.4.83.137.17.100.44463.1.4.91.189.89.90.80 = INTEGER: 11

或者用完全展开的文本表示：

.iso.org.dod.internet.mgmt.mib-2.tcp.tcpConnectionTable.tcpConnectionEntry.tcpConnectionState.ipv4."83.137.17.100".44463.ipv4."91.189.89.90".80

我不确定这是否比你现在的做法更简单，但这确实是一种标准化的方法……