Since key.dns_resolver isn't given a TTL for the address information obtained for getaddrinfo(), no expiry is set on dns_resolver keys in the kernel for NFS, CIFS or Ceph. AFS gets one if it looks up a cell SRV or AFSDB record because that is looked up in the DNS directly, but it doesn't look up A or AAAA records, so doesn't get an expiry for the addresses themselves. I've previously asked the libc folks if there's a way to get this information exposed in struct addrinfo, but I don't think that ended up going anywhere - and, in any case, would take a few years to work through the system. For the moment, I think I should put a default on any dns_resolver keys and have it applied either by the kernel (configurable with a /proc/sys/ setting) or by the key.dnf_resolver program (configurable with an /etc file). Any suggestion as to the preferred default TTL? 10 minutes? David
