bad udp cksum messages in tcpdump for wg0
cs at lost-frequencies.eu
Fri Dec 20 14:47:55 CET 2019
My DNS server is available via a wireguard interface. Because of many requests I did a tcpdump on the traffic and found messages like.
14:05:34.881307 IP (tos 0x0, ttl 63, id 33826, offset 0, flags [DF], proto UDP (17), length 54)
10.99.97.15.53628 > 10.99.97.17.domain: [bad udp cksum 0xd719 -> 0x6360!] 8446+ A? postgres. (26)
I could turn that messages off with turning off check validation on the interface
ethtool -K wg0 tx off rx off
The tcpdump traffic looks now like this
14:08:36.494987 IP (tos 0x0, ttl 63, id 61627, offset 0, flags [DF], proto UDP (17), length 54)
10.99.97.15.40185 > 10.99.97.17.domain: [udp sum ok] 1324+ A? postgres. (26)
I want to know if the behavior described above with the checksum errors is to be expected? Or is it necessary to turn those checks off on all the interfaces?
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