Missing UDP packets between docker containers
packets ``dropped by kernel'' (this is the number of packets that were dropped, due to a lack of buffer space, by the packet capture mechanism in the OS on which tcpdump is running, if the OS reports that information to applications; if not, it will be reported as 0).
kernel writes captured data to special buffer and tcpdump reads data from that buffer. If buffer is full packet is dropped.
Network often faster than disk, which mean sometimes you can't just capture all the packets. But since number of packed dropped is small this is not your case so you could do the following.
- Increase buffer for tcpdump, -B or --buffer-size options, size in KB. Default is 2048KB.
- sudo nice -10 tcpdump - give tcpdump additional priority (or even -20)
- if you on linux sudo nice -10 ionice -c 1 tcpdump additional disk write priority