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#1 2018-08-16 01:36:11

Herodotus
Member
Registered: 2015-06-16
Posts: 24

nscd breaks ssh due to link-local IPv6 address on recent upgrade

Recently I upgraded (pacman -Syu) and rebooted my laptop. I couldn't connect to a headless server with ssh. Both laptop and server get configured via a Linksys router using DHCP. The router is kind enough to keep track of the hostnames they request in the DHCP leases, so that is how I've been talking to the server - by "ssh myserver" where "myserver" is the name I put in /etc/hostname on the server.

The problem was intermittent and I traced it to nscd.

Something about link-local IPv6 addresses. ssh wanted to have an interface specified as part of the address, but there was none. I didn't even know that I was using IPv6, when I run ifconfig I see an IPv4 address and ignore the "inet6" line. 'host' returns an IPv4 address. Sometimes 'ssh' resolves the host to an IPv4 address, but every few minutes this changes to an IPv6 address that it doesn't like. So 'ssh' works for a minute or two, then breaks, then works, etc.

Turning off nscd with 'sudo systemctl stop nscd.service' fixes the problem. Now 'ssh' gets IPv6 link-local addresses with an interface specified, and it can connect successfully.

Wondering if this is a bug.

More details on superuser.com: https://superuser.com/questions/1349197 … st-myserve

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