[systemd-devel] systemd-resolved only returns v6 addresses

[Stefan Tatschner]

Heya,

I was confronted with a weird problem this morning. On my location
there is only IPv4 available. My company uses the shiny new Office365
service for email. This morning I was not able to connect to my email
account. The reason was systemd-resolved returning only IPv6 addresses
for the email host:

$ resolvectl query outlook.office365.com
outlook.office365.com: 2603:1026:c0a:855::2    -- link: enp3s0
                       2603:1026:c0a:857::2    -- link: enp3s0
                       2603:1026:c0a:8b7::2    -- link: enp3s0
                       2603:1026:c0a:850::2    -- link: enp3s0
                       2603:1026:c0a:852::2    -- link: enp3s0
                       2603:1026:c0a:851::2    -- link: enp3s0
                       2603:1026:101:1::2      -- link: enp3s0
                       2603:1026:c0a:854::2    -- link: enp3s0
                       (outlook.ha.office365.com)

-- Information acquired via protocol DNS in 820us.
-- Data is authenticated: no

The `host` utility instead reports this:

$ host outlook.office365.com
outlook.office365.com is an alias for outlook.ha.office365.com.
outlook.ha.office365.com is an alias for outlook.ms-acdc.office.com.
outlook.ms-acdc.office.com is an alias for AMS-efz.ms-acdc.office.com.
AMS-efz.ms-acdc.office.com has address 40.101.12.66
AMS-efz.ms-acdc.office.com has address 52.97.250.210
AMS-efz.ms-acdc.office.com has address 40.101.121.34
AMS-efz.ms-acdc.office.com has address 52.97.155.114
AMS-efz.ms-acdc.office.com has IPv6 address 2603:1026:c03:581b::2
AMS-efz.ms-acdc.office.com has IPv6 address 2603:1026:207:177::2
AMS-efz.ms-acdc.office.com has IPv6 address 2603:1026:207:64::2
AMS-efz.ms-acdc.office.com has IPv6 address 2603:1026:206:4::2

The problem was that systemd-resolved only returned ipv6 addresses
although I have no ipv6 connectivity. Why does this happen? Is there an
artificial max. addresses limit with the sorting rule ipv6 first in
systemd-resolved?

I work-arounded it with an entry in /etc/hosts for now.

Stefan