Sort SRV records by priority

[alex-zel]

In some cases where multiple SRV records are present, LDAP and Kerberos records were returned in different order, causing replication issues in a multi master enviorment.

Replication:

DNS configuration (using PfSense):

srv-host=_kerberos._udp.example.com,server01.example.com,88,0,1
srv-host=_kerberos._tcp.example.com,server01.example.com,88,0,1
srv-host=_kerberos-master._tcp.example.com,server01.example.com,88,0,1
srv-host=_kerberos-master._udp.example.com,server01.example.com,88,0,1
srv-host=_kpasswd._tcp.example.com,server01.example.com,88,0,1
srv-host=_kpasswd._udp.example.com,server01.example.com,88,0,1
srv-host=_ldap._tcp.example.com,server01.example.com,389,0,1
srv-host=_kerberos._udp.example.com,server02.example.com,88,0,2
srv-host=_kerberos._tcp.example.com,server02.example.com,88,0,2
srv-host=_kerberos-master._tcp.example.com,server02.example.com,88,0,2
srv-host=_kerberos-master._udp.example.com,server02.example.com,88,0,2
srv-host=_kpasswd._tcp.example.com,server02.example.com,88,0,2
srv-host=_kpasswd._udp.example.com,server02.example.com,88,0,2
srv-host=_ldap._tcp.example.com,server02.example.com,389,0,2
txt-record=_kerberos.example.com,EXAMPLE.COM

Client installation:
Host record is added beforehand from web UI on server01.example.com ONLY.
/usr/sbin/ipa-client-install --force-join --principal=bind_user --password=bind_pass --hostname=hostname -f --unattended

/var/log/ipaclient-install.log:

2017-04-02T10:54:09Z DEBUG [IPA Discovery]
2017-04-02T10:54:09Z DEBUG Starting IPA discovery with domain=None, servers=None, hostname=client01.example.com
2017-04-02T10:54:09Z DEBUG Start searching for LDAP SRV record in "example.com" (domain of the hostname) and its sub-domains
2017-04-02T10:54:09Z DEBUG Search DNS for SRV record of _ldap._tcp.example.com
2017-04-02T10:54:09Z DEBUG DNS record found: 0 1 389 server01.example.com.
2017-04-02T10:54:09Z DEBUG DNS record found: 0 2 389 server02.example.com.
2017-04-02T10:54:09Z DEBUG [Kerberos realm search]
2017-04-02T10:54:09Z DEBUG Search DNS for TXT record of _kerberos.example.com
2017-04-02T10:54:09Z DEBUG DNS record not found: NoAnswer
2017-04-02T10:54:09Z DEBUG Search DNS for SRV record of _kerberos._udp.example.com
2017-04-02T10:54:09Z DEBUG DNS record found: 0 2 88 server02.example.com.
2017-04-02T10:54:09Z DEBUG DNS record found: 0 1 88 server01.example.com.

Notice the records are not in the same order, ipa-client-install did not return any error and the client machine could see user, groups, netgroups, but users could not authenticate.
Looking at the web UI, server01.example.com shows the client is not enrolled and no kerberos key is present, but server02.example.com shows the client is enrolled and has a key.

In cases were either server01 or server02 were returned first in IPA Discovery the installation and replication went fine.

[tiran]

Minor style nitpicks

[tiran]

Please leave the order of imports.

[tiran]

Please use import operator and move the import before import socket. The operator module is a stdlib module and belongs in the top section.

[MartinBasti]

@alex-zel Please merge your commits into one, thanks.

[alex-zel]

Sorry I think I messed up trying to squash the commits

[MartinBasti]

git reset HEAD~3
git commit add -p
git commit --amend

should help

[MartinBasti]

I squashed your commits, please check

[alex-zel]

Thanks, sorry I didn't get to it.

[MartinBasti]

master:

• 8ec8e24 Sort SRV records by priority