Broken remote-as config validation for peer groups (e.g. for remote-as auto)

[robinchrist]

Description

The config validation for remote-as for peers with peer groups is inconsistent and broken. It appears like when remote-as auto was added, the config validation was not considered.

Version

FRRouting 10.5.2

How to reproduce

vyos(config)# router bgp 123
vyos(config-router)# neighbor 1.1.1.1 peer-group foo
vyos(config-router)# neighbor 2.2.2.2 peer-group foo
vyos(config-router)# neighbor 1.1.1.1 remote-as auto 
vyos(config-router)# neighbor 2.2.2.2 remote-as internal 
% Peer-group members must be all internal or all external.
vyos(config-router)# neighbor 2.2.2.2 remote-as auto
% Peer-group members must be all internal or all external.
vyos(config-router)# neighbor 2.2.2.2 remote-as external
vyos(config-router)#

When one neighbor has remote-as auto, why can the other one be configured with external, but not internal or auto?

Expected behavior

Proper handling of neighbors with remote-as auto in peer groups.

Peer-group members must be all internal or all external. -> What is the reason for this in general? Is this still necessary?
What happens when you have a peer group with remote-as auto and thus potentially have peer group members with mixed AS?

Actual behavior

See above.

Additional context

No response

Checklist

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

[ton31337]

Fixed in #21450.