Turris Omnia (Knot resolver): t.co does not resolve. twitter.com does

My Turris Omnia cannot resolve t.co, but has no problems with other domains such as twitter.com or x.co. Local names (hpdisk.lan) also work: ~~~ root@turris:~# ping t.co ping: t.co: Name does not resolve root@turris:~# ping twitter.com PING twitter.com (104.244.42.193) 56(84) bytes of data. 64 bytes from 104.244.42.193 (104.244.42.193): icmp_seq=1 ttl=58 time=11.5 ms tange@turris:~$ ping x.co PING x.co (148.72.51.157) 56(84) bytes of data. 64 bytes from 157.51.72.148.host.secureserver.net (148.72.51.157): icmp_seq=1 ttl=42 time=139 ms tange@turris:~$ ping hpdisk.lan PING hpdisk.lan (192.168.1.30) 56(84) bytes of data. 64 bytes from 192.168.1.30 (192.168.1.30): icmp_seq=1 ttl=64 time=0.374 ms ~~~ The router has no problem querying the auth name servers, so it is not caused by some network filtering or routing problem: ~~~ root@turris:/tmp/log# dig @a.r06.twtrdns.net. t.co ; > DiG 9.18.24 > @a.r06.twtrdns.net. t.co ; (1 server found) ;; global options: +cmd ;; Got answer: ;; ->>HEADER 156.154.105.25.53: 20216% [1au] A? U.CO. (33) 14:36:00.484396 IP 156.154.105.25.53 > 100.100.246.190.51757: 20216- 0/6/1 (639) 14:36:00.485495 IP 100.100.246.190.55245 > 193.108.91.245.53: 25634% [1au] A? Ns50.DoMAInCoNtROL.COm. (51) 14:36:00.500380 IP 193.108.91.245.53 > 100.100.246.190.55245: 25634*- 1/0/1 A 173.201.72.25 (67) 14:36:00.500659 IP 100.100.246.190.60650 > 173.201.72.25.53: 49104% [1au] A? U.Co. (33) 14:36:00.513975 IP 173.201.72.25.53 > 100.100.246.190.60650: 49104*- 2/2/1 A 15.197.142.173, A 3.33.152.147 (120) ~~~ Looking up t.co causes no traffic. It smells as if Knot Resolver thinks it is auth for t.co I have tried rebooting the router. This did not fix the issue. ~~~ root@turris:~# uname -a Linux turris 5.15.148 #0 SMP Tue Apr 2 01:04:13 2024 armv7l GNU/Linux root@turris:~# kresd --version Knot Resolver, version 5.7.1 root@turris:~# netstat -anp |grep 0:53 tcp 0 0 0.0.0.0:53 0.0.0.0:* LISTEN 18768/kresd udp 0 0 0.0.0.0:53 0.0.0.0:* 18768/kresd tange@turris:~$ cat /etc/resolv.conf search lan nameserver 127.0.0.1 nameserver ::1 root@turris:/tmp/log# cat /var/log/resolver Apr 27 11:52:30 turris kresd: [system] warning: hard limit for number of file-descriptors is only 4096 but recommended value is 524288 Apr 27 11:52:50 turris kresd: [system] warning: hard limit for number of file-descriptors is only 4096 but recommended value is 524288 ~~~