[systemd-devel] systemd-resolve SERVFAIL on lookups found by upstream DNS server

[Francesco Belladonna]

Greetings,
I’ve been trying to debug why systemd-resolve is not able to perform nslookup
static-exp1.licdn.com.
Altering /etc/resolv.conf to point directly to the DNS server (or my router
in this case) solves the problem, which seems to suggest the problem is
isolated to systemd-resolve.
The problem is identical on both my laptops which are running 2 different
O.S. (Kubuntu 18.04 and Fedora 33).
The entire DNS configuration is provided by the router acting as DHCP
server.

The system I’m performing my tests is Kubuntu, where the systemd version is:

systemd --version
systemd 237
+PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP
+LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS
+KMOD -IDN2 +IDN -PCRE2 default-hierarchy=hybrid

SYSTEMD_LOG_LEVEL is set to debug.
Is there any other useful tool I can use to debug this further?
The problematic domain is static-exp1.licdn.com which is the CDN for
LinkedIn. I have no idea why *this* specific domain is affected.

Attached the output of journalctl -u systemd-resolved -f, located at this
URL:
https://gist.github.com/Fire-Dragon-DoL/8369b07dc27f57f7f05ffa25fd1d6962
The output is obtained by running nslookup static-exp1.licdn.com after
systemd-resolve
--flush-caches.

Any help is greatly appreciated.
My temporary fix is to alter /etc/resolv.conf to sidestep systemd-resolve.
I’d like to avoid this approach since it removes local caching

—
Francesco Belladonna
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