A newly created network namespace may disallow ICMP echo sockets for
unprivileged users even when their GIDs are mapped into the container.
When creating both user and network namespaces, initialize
net.ipv4.ping_group_range using the mapped GID range capped at INT32_MAX.
This follows the system-wide default from sysctl.d/50-default.conf while
respecting the user namespace mapping and the kernel's accepted limit.
Leave externally supplied network namespaces untouched and treat write
failures as non-fatal warnings.
Add regression coverage for the default 64K mapped range using the tools
already available in the minimal container image.
Fixes#41603
totoro
2fa149f2c4