Remember to turn off TSO GSO
Before start capturing your packets to troubleshoot, remember to turn off tso and gso. Segment offloading is to let your NIC deal with packet processing, such as packet fragmentation and retransmission. This generally is good but hides your real packet transmission. In linux, you can disable this features by executing below commands.
Capture TCP packet to a host:port
- -s 0: do not truncate packets
Capture TCP packet of a subnet
Capture UDP packet of specific bytes
Filter out a tcpdump file to another file