Hello there! In our IPv6 network, the address of a Recursive DNS Server (RDNSS) is supplied in a Router Advertisement (RA), with a lifetime of 60 seconds.
It appears that RDNSS lifetime is not being honoured (RFC 8106, section 5.1<https://www.rfc-editor.org/rfc/rfc8106.html#section-5.1:~:text=in the option.-,Lifetime,-32-bit unsigned>). I reviewed the code and can see where the RDNSS lifetime is being saved<https://github.com/systemd/systemd-stable/blob/4a31fa2fb040005b73253da75cf84949b8485175/src/network/networkd-ndisc.c#L712>, though I was unable to determine how it was being handled upon expiry. How do I configure networkd so that the RA's RDNSS lifetime is honoured? Here is a summary of the simple protocol exchange: 1. Router: Send RA [RDNSS address of "nameserver60s", lifetime: "60"] 2. Host: "resolvectl" shows the link's DNS server now lists the RDNSS address of "nameserver60s" 3. ** Wait for more than 60 seconds - the RDNSS entry should expire ** 4. Host: * "resolvectl" continues to list the address of "nameserver60s" on the link. * Using tcpdump to trace "ping test.example.com", the "nameserver60s" is still being used. It never timed out. Here is my network configuration, showing UseDNS and UseDomains both set to "yes": ------------------------------------------------------------ $ cat /etc/systemd/network/10-eno0.network [Match] KernelCommandLine=!nfsroot Name=eno0 [DHCP] ClientIdentifier=mac RouteMetric=10 UseDomains=yes UseHostname=yes UseMTU=yes [Network] #DHCP=ipv6 Address=10.1.1.1/24 #DNS=1.2.3.6 Gateway=1.1.1.2 IPv6AcceptRA=yes [IPv6AcceptRA] UseDNS=yes UseDomains=yes ------------------------------------------------------------ Grateful for any suggestions. Kind regards, Matt. PS: We're on systemd 250. I've searched later versions of the release notes<https://github.com/systemd/systemd/releases> and it seems there have been no changes in this area.
