Created a new VPS instance, ipv6 worked until installing OMR server

[bdruth]

Just setup a new VPS, Debian 11 x64, ran ping6 to ipv6.google.com - all good. Stopped working in the midst of the OMR server script. What is the script doing to break ipv6 and what can I do to fix it again?

[bdruth]

Not conclusive (yet) - but I monitored where in the install the ipv6 breaks by running a ping6 in the background - it seems to break around when dsvpn or glorytun is installed in the script ... I canceled the script and ran ifconfig and saw the dsvpn/gt-* interfaces ... so, I thought, ok - I'll tear down each of those in turn and see if ipv6 starts working again ... sure enough, ifconfig dsvpn0 down and then ping6 started working again.

[bdruth]

So, after completing the full script & rebooting, it does seem that disabling dsvpn0 consistently fixes ipv6 access from the VPS to the Internet. Not sure what's up there, but I'm able to consistently reproduce now.

[Ysurac]

What is the result of ip -6 r and ip -6 a before and after starting dsvpn ?

[bdruth]

Before

root@debian-13:~# ping6 -c 2 ipv6.google.com; ip -6 r && ip -6 a
PING ipv6.google.com(ord37s36-in-x0e.1e100.net (2607:f8b0:4009:814::200e)) 56 data bytes
64 bytes from ord37s36-in-x0e.1e100.net (2607:f8b0:4009:814::200e): icmp_seq=1 ttl=118 time=1.43 ms
64 bytes from ord37s36-in-x0e.1e100.net (2607:f8b0:4009:814::200e): icmp_seq=2 ttl=118 time=1.42 ms

--- ipv6.google.com ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 1.415/1.423/1.431/0.008 ms
::1 dev lo proto kernel metric 256 pref medium
****:****:1::4:0/110 dev eth0 proto kernel metric 256 pref medium
fdfe:8abf:9104::/48 via fe80::a00:2 dev omr-6in4-user0 metric 1024 pref medium
fe80::a00:0/126 dev omr-6in4-user0 proto kernel metric 256 pref medium
fe80::/64 dev eth0 proto kernel metric 256 pref medium
fe80::/64 dev mlvpn0 proto kernel metric 256 pref medium
fe80::/64 dev gt-tun0 proto kernel metric 256 pref medium
fe80::/64 dev gt-udp-tun0 proto kernel metric 256 pref medium
fe80::/64 dev omr-6in4-user0 proto kernel metric 256 pref medium
fe80::/64 dev tun0 proto kernel metric 256 pref medium
fe80::/64 dev tun1 proto kernel metric 256 pref medium
fe80::/64 dev omr-bonding proto kernel metric 256 pref medium
default via ****:****:1::4:1 dev eth0 metric 1024 onlink pref medium
1: lo: <LOOPBACK,UP,LOWER_UP,80000> mtu 65536 state UNKNOWN qlen 1000
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP qlen 1000
    inet6 ****:****:1::4:248/110 scope global deprecated
       valid_lft forever preferred_lft 0sec
    inet6 fe80::216:3eff:fe5b:e328/64 scope link
       valid_lft forever preferred_lft forever
3: mlvpn0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP,80000> mtu 1444 state UNKNOWN qlen 500
    inet6 fe80::9cab:dd27:484a:4c80/64 scope link stable-privacy
       valid_lft forever preferred_lft forever
4: gt-tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP,80000> mtu 1500 state UNKNOWN qlen 500
    inet6 fe80::5436:5072:69e8:a38f/64 scope link stable-privacy
       valid_lft forever preferred_lft forever
5: gt-udp-tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP,80000> mtu 1500 state UP qlen 100
    inet6 fe80::1cdb:f419:5434:4ad9/64 scope link stable-privacy
       valid_lft forever preferred_lft forever
6: omr-bonding: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP,80000> mtu 1440 state UP qlen 1000
    inet6 fe80::c83a:bbff:fe57:ceb4/64 scope link
       valid_lft forever preferred_lft forever
8: omr-6in4-user0@NONE: <POINTOPOINT,NOARP,UP,LOWER_UP,80000> mtu 1480 state UNKNOWN qlen 1000
    inet6 fe80::aff:ff01/64 scope link
       valid_lft forever preferred_lft forever
    inet6 fe80::a00:1/126 scope link
       valid_lft forever preferred_lft forever
17: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP,80000> mtu 1500 state UNKNOWN qlen 500
    inet6 fe80::c71c:6a2e:7945:7b02/64 scope link stable-privacy
       valid_lft forever preferred_lft forever
18: tun1: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP,80000> mtu 1500 state UNKNOWN qlen 500
    inet6 fe80::de1f:6436:f159:32e/64 scope link stable-privacy
       valid_lft forever preferred_lft forever

After

root@debian-13:~# systemctl start dsvpn-server@dsvpn0
root@debian-13:~# ping6 -c 2 ipv6.google.com; ip -6 r && ip -6 a
PING ipv6.google.com(ord37s36-in-x0e.1e100.net (2607:f8b0:4009:814::200e)) 56 data bytes

--- ipv6.google.com ping statistics ---
2 packets transmitted, 0 received, 100% packet loss, time 1014ms

::1 dev lo proto kernel metric 256 pref medium
****:****:1::4:0/110 dev eth0 proto kernel metric 256 pref medium
fdfe:8abf:9104::/48 via fe80::a00:2 dev omr-6in4-user0 metric 1024 pref medium
fe80::a00:0/126 dev omr-6in4-user0 proto kernel metric 256 pref medium
fe80::/64 dev eth0 proto kernel metric 256 pref medium
fe80::/64 dev mlvpn0 proto kernel metric 256 pref medium
fe80::/64 dev gt-tun0 proto kernel metric 256 pref medium
fe80::/64 dev gt-udp-tun0 proto kernel metric 256 pref medium
fe80::/64 dev omr-6in4-user0 proto kernel metric 256 pref medium
fe80::/64 dev tun0 proto kernel metric 256 pref medium
fe80::/64 dev tun1 proto kernel metric 256 pref medium
fe80::/64 dev omr-bonding proto kernel metric 256 pref medium
fe80::/64 dev dsvpn0 proto kernel metric 256 pref medium
default via ****:****:1::4:1 dev eth0 metric 1024 onlink pref medium
1: lo: <LOOPBACK,UP,LOWER_UP,80000> mtu 65536 state UNKNOWN qlen 1000
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP qlen 1000
    inet6 ****:****:1::4:248/110 scope global deprecated
       valid_lft forever preferred_lft 0sec
    inet6 fe80::216:3eff:fe5b:e328/64 scope link
       valid_lft forever preferred_lft forever
3: mlvpn0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP,80000> mtu 1444 state UNKNOWN qlen 500
    inet6 fe80::9cab:dd27:484a:4c80/64 scope link stable-privacy
       valid_lft forever preferred_lft forever
4: gt-tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP,80000> mtu 1500 state UNKNOWN qlen 500
    inet6 fe80::5436:5072:69e8:a38f/64 scope link stable-privacy
       valid_lft forever preferred_lft forever
5: gt-udp-tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP,80000> mtu 1500 state UP qlen 100
    inet6 fe80::1cdb:f419:5434:4ad9/64 scope link stable-privacy
       valid_lft forever preferred_lft forever
6: omr-bonding: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP,80000> mtu 1440 state UP qlen 1000
    inet6 fe80::c83a:bbff:fe57:ceb4/64 scope link
       valid_lft forever preferred_lft forever
8: omr-6in4-user0@NONE: <POINTOPOINT,NOARP,UP,LOWER_UP,80000> mtu 1480 state UNKNOWN qlen 1000
    inet6 fe80::aff:ff01/64 scope link
       valid_lft forever preferred_lft forever
    inet6 fe80::a00:1/126 scope link
       valid_lft forever preferred_lft forever
17: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP,80000> mtu 1500 state UNKNOWN qlen 500
    inet6 fe80::c71c:6a2e:7945:7b02/64 scope link stable-privacy
       valid_lft forever preferred_lft forever
18: tun1: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP,80000> mtu 1500 state UNKNOWN qlen 500
    inet6 fe80::de1f:6436:f159:32e/64 scope link stable-privacy
       valid_lft forever preferred_lft forever
22: dsvpn0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP,80000> mtu 9000 state UNKNOWN qlen 500
    inet6 64:ff9b::aff:fb01 peer 64:ff9b::aff:fb02/96 scope global
       valid_lft forever preferred_lft forever
    inet6 fe80::610a:bc3a:db18:4cc2/64 scope link stable-privacy
       valid_lft forever preferred_lft forever

Note: I've obfuscated (****) the identifying bits of the prefix for the global address - if you need that, lemme know.