Description
This issue is transferred from here.
In this ticket, the user is trying to reach the IPv6 address of Google by running the command "curl -6 https://www.google.com" on the GitHub-hosted Ubuntu runner, but it always failed to connect and returned the message "Couldn't connect to server".
The command "curl https://www.google.com" or "curl -4 https://www.google.com" can work fine to reach the IPv4 address.
I also tested directly ping the IPv6 address of Google via the command "ping6 ipv6.google.com", it also failed to connect and returned the message "connect: Network is unreachable".
To check whether the current Linux kernel supports IPv6 via the command,
[ -f /proc/net/if_inet6 ] && echo 'IPv6 ready system!' || echo 'No IPv6 support found! Compile the kernel!!'
It returns "IPv6 ready system!", looks like IPv6 is supported.
Then to check whether the IPv6 module has loaded,
lsmod | grep -qw ipv6 && echo "IPv6 kernel driver loaded and configured." || echo "IPv6 not configured and/or driver loaded on the system."
It returns "IPv6 not configured and/or driver loaded on the system.", looks like the IPv6 module is not loaded.
Load the IPv6 module and check again.
modprobe ipv6
lsmod | grep -qw ipv6 && echo "IPv6 kernel driver loaded and configured." || echo "IPv6 not configured and/or driver loaded on the system."
The returned result still shows that the IPv6 module is not loaded. Looks like this should be the reason for failed to reach the IPv6 address.
Why it can't load the IPv6 module on the GitHub-hosted runner? Whether this is an expected behavior for some limitations set on the hosted runners?