hostname and domainname for BGP peers

[SwimGeek]

Description

I'd like to configure the hostname and domainname sent to BGP peers.

Please see discussion: #16903

It seems that FRR needs to be able to use the output of: dnsdomainname

Version

FRR v10.1.1

How to reproduce

Try to configure domainname in FRR.

Expected behavior

FRR needs to inherit the value of the command dnsdomainname and be able to add it to frr.conf.

Actual behavior

I can't configure domainname in frr.

Additional context

No response

Checklist

• I have searched the open issues for this bug.
• I have not included sensitive information in this report.

[ton31337]

uname() returns nodename as FQDN (not a short version), thus it's tricky. We could treat the first occurrence (stripped by dot) as a short name, while the rest is the domain name, but this is not true again if multi-level domains are used...

[SwimGeek]

Hi

This is from the dnssdomainname man page:

'The DNS domain name is the part after the first dot.'

...

   You cannot change the FQDN with hostname or dnsdomainname.

   The  recommended  method of setting the FQDN is to make the hostname be an alias
   for the fully qualified name using /etc/hosts, DNS, or NIS. For example, if  the
   hostname was "ursula", one might have a line in /etc/hosts which reads

          127.0.1.1    ursula.example.com ursula

   Technically:  The  FQDN is the name getaddrinfo(3) returns for the host name re‐
   turned by gethostname(2).  The DNS domain name is the part after the first dot.

[ton31337]

If we just follow this, then this is the easy FIX. Would you like to test this branch?

[SwimGeek]

Thanks. Will this allow me to set domainname in vtysh? and then save to frr.conf

Does it do any checking, must match host domainname?

[ton31337]

Thanks. Will this allow me to set domainname in vtysh? and then save to frr.conf

Nope, it will just strip the first part before the dot and treat everything else as a domain name, that's it :)

[SwimGeek]

Ok, example case:

If I wanted to configure a router to send 'localhost.localdomain' to BGP peer, I would add the following to frr.conf

hostname localhost.localdomain