wangyu-
[WARN]huge packet, data_len > 1800,dropped
环境：ss+kcptun+udp2raw(20181113.0)，udp2raw装在路由器上，路由器是用的ambian做的软路由，也就是arm路由器，非虚拟机，所以不存在桥接或NAT问题。
在看youtube时会大量出现这个警告，但似乎并不影响视频的正常播放，速度也还不错，在一些其它网站也会出现这个警告，但没有y2那么多，比如PC端的google play也会少量出现这个警告。
搜索到之前issue，怀疑可能是mtu问题，分别测试kcptun的mtu为1200，1000，500，都还有这个警告。
怀疑是否kcptun有BUG,在发送大包，于是抓发，发现在设置mtu值为1300的情况下，抓到的包最大也确实只有1300，udp2raw对外发送的最大包是1344，这说明udp2raw对包的处理会加44个字节？
所以应该不是kcptun发送了大包给udp2raw，请大佬看看是什么问题，抓的包放在二楼的，如果要其它日志请告诉我。
[2019-03-26 08:53:58][INFO]new packet from 127.0.0.1:47399,conv_id=1b7d13eb [2019-03-26 08:53:58][INFO]new packet from 127.0.0.1:51778,conv_id=59b87bba [2019-03-26 08:54:01][WARN]huge packet, data_len > 1800,dropped [2019-03-26 08:54:08][WARN]huge packet, data_len > 1800,dropped [2019-03-26 08:54:08][WARN]huge packet, data_len > 1800,dropped [2019-03-26 08:54:08][WARN]huge packet, data_len > 1800,dropped [2019-03-26 08:54:09][WARN]huge packet, data_len > 1800,dropped [2019-03-26 08:54:10][WARN]huge packet, data_len > 1800,dropped [2019-03-26 08:54:10][WARN]huge packet, data_len > 1800,dropped [2019-03-26 08:54:11][WARN]huge packet, data_len > 1800,dropped [2019-03-26 08:54:11][WARN]huge packet, data_len > 1800,dropped [2019-03-26 08:54:43][WARN]huge packet, data_len > 1800,dropped [2019-03-26 08:54:43][WARN]huge packet, data_len > 1800,dropped [2019-03-26 08:54:49][WARN]huge packet, data_len > 1800,dropped
08:54:49.075957 IP localhost.4000 > localhost.42406: UDP, length 1300 08:54:49.076128 IP localhost.4000 > localhost.42406: UDP, length 1300 08:54:49.076632 IP localhost.4000 > localhost.42406: UDP, length 1300 08:54:49.076811 IP localhost.4000 > localhost.42406: UDP, length 1300 08:54:49.077177 IP localhost.4000 > localhost.42406: UDP, length 1300 08:54:49.077404 IP localhost.4000 > localhost.42406: UDP, length 1300 08:54:49.077635 IP localhost.4000 > localhost.42406: UDP, length 1300 08:54:49.077818 IP localhost.4000 > localhost.42406: UDP, length 1300 08:54:49.078216 IP localhost.4000 > localhost.42406: UDP, length 1300 08:54:49.078446 IP localhost.4000 > localhost.42406: UDP, length 1300 08:54:49.078656 IP localhost.4000 > localhost.42406: UDP, length 1300 08:54:49.078656 IP localhost.42406 > localhost.4000: UDP, length 916 08:54:49.078985 IP localhost.4000 > localhost.42406: UDP, length 1300
09:10:02.242078 IP aml.27402 > ...: Flags [.], seq 147584:148496, ack 856081, win 41288, options [nop,nop,TS val 249260691 ecr 65055964], length 912 09:10:02.242556 IP aml.27402 > ...: Flags [.], seq 148496:149728, ack 856081, win 40963, options [nop,nop,TS val 249260692 ecr 65055964], length 1232 09:10:02.242578 IP aml.27402 > ...: Flags [.], seq 148496:149728, ack 856081, win 40963, options [nop,nop,TS val 249260692 ecr 65055964], length 1232 09:10:02.242724 IP aml.27402 > ...: Flags [.], seq 149728:151072, ack 856081, win 40981, options [nop,nop,TS val 249260692 ecr 65055964], length 1344 09:10:02.242747 IP aml.27402 > ...: Flags [.], seq 149728:151072, ack 856081, win 40981, options [nop,nop,TS val 249260692 ecr 65055964], length 1344 09:10:02.242889 IP aml.27402 > ...: Flags [.], seq 151072:152416, ack 856081, win 41151, options [nop,nop,TS val 249260692 ecr 65055964], length 1344 09:10:02.242911 IP aml.27402 > ...: Flags [.], seq 151072:152416, ack 856081, win 41151, options [nop,nop,TS val 249260692 ecr 65055964], length 1344 09:10:02.243043 IP aml.27402 > ...: Flags [.], seq 152416:153760, ack 856081, win 41121, options [nop,nop,TS val 249260692 ecr 65055964], length 1344
一个issue里给出了临时解决方案，就是关闭gso和gro，实测有效，具体原因和详情可以去这个issue里查看。 https://github.com/wangyu-/udp2raw-tunnel/issues/226 我这里就写下命令吧： 查看 ethtool --show-offload eth0 | egrep 'generic-segmentation-offload|generic-receive-offload' generic-segmentation-offload: on generic-receive-offload: on
关闭 ethtool -K eth0 gso off ethtool -K eth0 gro off
再查看 ethtool --show-offload eth0 | egrep 'generic-segmentation-offload|generic-receive-offload' generic-segmentation-offload: off generic-receive-offload: off
最后添加到开机启动就可以了。
