最近在VM虚拟机里调试iptables，发现网卡上面有很多DROP的数据包，开启iptables 记录日志功能，发现了以下几个日志非常频繁。
# 开启iptables 记录日志
iptables -A INPUT -i ens38 -j LOG --log-prefix "iptables_INPUT_ens38_DROP: " --log-level notice
iptables -A INPUT -i ens38 -j DROP
iptables -A OUTPUT -o ens38 -j LOG --log-prefix "iptables_OUTPUT_ens38_DROP: " --log-level notice
iptables -A OUTPUT -o ens38 -j DROP
日志文件
Jan 26 21:06:43 localhost kernel: iptables_INPUT_ens38_DROP: IN=ens38 OUT= MAC=ff:ff:ff:ff:ff:ff:00:50:56:c0:00:02:08:00 SRC=192.168.81.1 DST=192.168.81.255 LEN=291 TOS=0x00 PREC=0x00 TTL=128 ID=19920 PROTO=UDP SPT=54915 DPT=54
915 LEN=271
Jan 27 09:50:13 localhost kernel: iptables_INPUT_ens38_DROP: IN=ens38 OUT= MAC=ff:ff:ff:ff:ff:ff:00:50:56:c0:00:02:08:00 SRC=192.168.81.1 DST=192.168.81.255 LEN=173 TOS=0x00 PREC=0x00 TTL=128 ID=59712 PROTO=UDP SPT=17500 DPT=17500 LEN=153
第一个 UDP 5419端口的为 鼠标Logitech‘s 程序的广播包，详细的文档如下：
http://support.moonpoint.com/network/udp/port_54915/
Why may you see UDP packets with a source port of 54915 and a destination port of 54915 being sent to the broadcast address for a subnet? When I searched for information on these packets, I found they are associated with Logitech‘s Arx control software. Logitech states in regards to that software:
Win the information war and stay ahead of the competition with critical in-game information on your tablet or smartphone. Arx control serves as a second screen for supported titles.
Arx Control lets you monitor and control your Logitech G peripherals without ever leaving the game. Fine-tune your mouse DPI in real time, or call up a list of your G-Key macros for quick reference right on your smartphone or tablet device.
Troubleshoot and monitor your system hardware with GPU/CPU temperatures and usage levels. Control your media or launch games remotely with built-in controls.
Arx Control is available on Android and iOS on tablets and smartphones, and works on any system with Logitech Gaming Software installed. Stand your smartphone upright in the adjustable Arx Smart Dock, on select Logitech keyboards, for convenient viewing.
You can find the software on Apple’s App Store at Logitech Arx Control. The page states “This app is only available on the App Store for iOS devices. Apple employs the iOS operating system on its iPhone, iPad, and iPod Touch devices. The software apparently looks for other devices with the Arx Conrol software installed by sending out the broadcast packets to UDP port 54,915 and then waits for those devices to respond.
第二个 UDP 包17500 为 DropBox 的LAN同步功能发的广播包。
关闭掉程序或者禁用这个LAN同步，以上两个广播包消失。