A case of weird UDP

2023-06-10

weird behavior for dns

continous udp dns queries to service will fail for a period of time, and then succeed for 30 seconds or so and then fail again
if udp queries are failing, tcp queries will also fail
if queries begin succeeding, then both tcp+udp will succeed together
if the tcp queries continue to be sent (and work), the udp queries also continue to work
if the queries are only udp, no tcp, the queries will succed for ~30 seconds and then begin failing
the period of time that queries fail is variable
- counted 7, 4, 5, 6, 2 in tests

packet dump udp - fail

- request comes into ethernet
01:17:33.445296 enp3s0 In  IP6 2001:19f0:5c00:26a2:5400:4ff:fe74:77a5.49901 > 2602:814:4000:8888::53.53: 19099+ A? facebook.com. (30)

- request gets pushed into cni0
01:17:33.445382 cni0  Out IP6 2001:19f0:5c00:26a2:5400:4ff:fe74:77a5.49901 > fdc0:9e85:e99e:6::12.53: 19099+ A? facebook.com. (30)

- veth254 gets the request
01:17:33.445393 veth254cdd8d Out IP6 2001:19f0:5c00:26a2:5400:4ff:fe74:77a5.49901 > fdc0:9e85:e99e:6::12.53: 19099+ A? facebook.com. (30)

- veth254 sends response
01:17:33.445764 veth254cdd8d P   IP6 fdc0:9e85:e99e:6::12.53 > 2001:19f0:5c00:26a2:5400:4ff:fe74:77a5.49901: 19099 1/0/0 A 31.13.71.36 (46)

- cni0 receives the responseq
01:17:33.445764 cni0  In  IP6 fdc0:9e85:e99e:6::12.53 > 2001:19f0:5c00:26a2:5400:4ff:fe74:77a5.49901: 19099 1/0/0 A 31.13.71.36 (46)

+++++++++ where's the outbound packet out of enp3s0? ++++++++++++

packet dump udp - success

01:31:48.358012 enp3s0 In  IP6 2001:19f0:5c00:26a2:5400:4ff:fe74:77a5.60044 > 2602:814:4000:8888::53.53: 37444+ A? facebook.com. (30)

01:31:48.358141 cni0  Out IP6 2001:19f0:5c00:26a2:5400:4ff:fe74:77a5.60044 > fdc0:9e85:e99e:6::12.53: 37444+ A? facebook.com. (30)

01:31:48.358156 veth254cdd8d Out IP6 2001:19f0:5c00:26a2:5400:4ff:fe74:77a5.60044 > fdc0:9e85:e99e:6::12.53: 37444+ A? facebook.com. (30)

01:31:48.358661 veth254cdd8d P   IP6 fdc0:9e85:e99e:6::12.53 > 2001:19f0:5c00:26a2:5400:4ff:fe74:77a5.60044: 37444 1/0/0 A 31.13.71.36 (46)

01:31:48.358661 cni0  In  IP6 fdc0:9e85:e99e:6::12.53 > 2001:19f0:5c00:26a2:5400:4ff:fe74:77a5.60044: 37444 1/0/0 A 31.13.71.36 (46)

01:31:48.358715 enp3s0 Out IP6 2602:814:4000:8888::53.53 > 2001:19f0:5c00:26a2:5400:4ff:fe74:77a5.60044: 37444 1/0/0 A 31.13.71.36 (46)