26.06.2019 15:11, Christian M wrote: > Running tcpdump on the host while running iperf3 between the 12.0 VM's > results in a lot of incorrect cksum like this. > > tcpdump -i vif54.0 -v -nn| grep -i incorrect > 172.31.16.125.63013 > 172.31.16.126.5201: Flags [.], cksum 0x7f08 > (incorrect -> 0x030f), seq 223153882:223155330, ack 1, win 1026, options > [nop,nop,TS val 4104002274 ecr 3926764642], length 1448
Incorrect checksum shown by tcpdump is normal and expected for outgoing packets if txcsum offload is not disabled because networking stack skips checksum calculation offloading it to "hardware". It still indicates a bug at sending side if seen for outgoing packets when txcsum is disabled. Incorrect checksum shown by tcpdump for incoming packets always indicates a problem at sending side or intermediate network (if any). You should check output of "netstat -sp ip" and "netstat -sp tcp" for non-zero and growing checksum error counters at receiving side. _______________________________________________ freebsd-net@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
