slirp4netns
slirp4netns provides user-mode networking ("slirp") for unprivileged network
namespaces.
Starting with Linux 3.8, unprivileged users can create network_namespaces(7)
along with user_namespaces(7). However, unprivileged network namespaces had
not been very useful, because creating veth(4) pairs across the host and
network namespaces still requires the root privileges. (i.e. No internet
connection)
slirp4netns allows connecting a network namespace to the Internet in a
completely unprivileged way, by connecting a TAP device in a network namespace
to the usermode TCP/IP stack ("slirp").
63daf9f79a