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").
Kubernetes distributions:
Container engines:
Tools:
| Version | Status |
|---|---|
| v1.2.x | :white_check_mark: Active |
| v1.1.x | End of Life (May 2, 2022) |
| v1.0.x | End of Life (Jun 2, 2020) |
| v0.4.x | End of Life (Sep 30, 2020) |
| v0.3.x | End of Life (Mar 31, 2020) |
| v0.2.x | End of Life (Aug 30, 2019) |
| Early versions prior to v0.2.x | End of Life (Jan 5, 2019) |
See https://github.com/rootless-containers/slirp4netns/releases for the releases.
See https://github.com/rootless-containers/slirp4netns/security/advisories for the past security advisories.
:warning: We had been collecting the vulnerabilities of QEMU/libslirp in this slirp4netns repo until the end of 2020, as the slirp4netns releases prior to v1.0.0 were always statically linked with a specific version of QEMU/libslirp. Starting with 2021, the vulnerabilities of libslirp are no longer collected in this slirp4netns repo, as slirp4netns >= v1.0.0 can be linked with an arbitrary version of libslirp.
slirp4netns --version to check the version of the linked libslirp. ```console $ slirp4netns --version slirp4netns version 1.1.8 commit: d361001f495417b880f20329121e3aa431a8f90f libslirp: 4.4.0 SLIRP_CONFIG_VERSION_MAX: 3 libseccomp: 2.4.3 ```
Statically linked binaries available for x86_64, aarch64, armv7l, s390x, ppc64le, and riscv64: https://github.com/rootless-containers/slirp4netns/releases
Also available as a package on almost all Linux distributions:
e.g.
$ sudo apt-get install slirp4netnsTo install slirp4netns from the source, see Install from source.
Terminal 1: Create user/network/mount namespaces
(host)$ unshare --user --map-root-user --net --mount
(namespace)$ echo $$ > /tmp/pidIn this documentation, we use (host)$ as the prompt of the host shell, (namespace)$ as the prompt of the shell running in the namespaces.
If unshare fails, try the following commands (known to be needed on Debian, Arch, and old CentOS 7.X):
(host)$ sudo sh -c 'echo "user.max_user_namespaces=28633" >> /etc/sysctl.d/userns.conf'
(host)$ [ -f /proc/sys/kernel/unprivileged_userns_clone ] && sudo sh -c 'echo "kernel.unprivileged_userns_clone=1" >> /etc/sysctl.d/userns.conf'
(host)$ sudo sysctl --systemTerminal 2: Start slirp4netns
(host)$ slirp4netns --configure --mtu=65520 --disable-host-loopback $(cat /tmp/pid) tap0
starting slirp, MTU=65520
...Terminal 1: Make sure the tap0 is configured and connected to the Internet
(namespace)$ ip a
1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
3: tap0: <BROADCAST,UP,LOWER_UP> mtu 65520 qdisc fq_codel state UNKNOWN group default qlen 1000
link/ether c2:28:0c:0e:29:06 brd ff:ff:ff:ff:ff:ff
inet 10.0.2.100/24 brd 10.0.2.255 scope global tap0
valid_lft forever preferred_lft forever
inet6 fe80::c028:cff:fe0e:2906/64 scope link
valid_lft forever preferred_lft forever
(namespace)$ echo "nameserver 10.0.2.3" > /tmp/resolv.conf
(namespace)$ mount --bind /tmp/resolv.conf /etc/resolv.conf
(namespace)$ curl https://example.comManual: slirp4netns.1.md
Aug 28, 2018, on RootlessKit Travis: https://github.com/rootless-containers/rootlesskit/pull/16
| Implementation | MTU=1500 | MTU=4000 | MTU=16384 | MTU=65520 |
|---|---|---|---|---|
| vde_plug | 763 Mbps | Unsupported | Unsupported | Unsupported |
| VPNKit | 514 Mbps | 526 Mbps | 540 Mbps | Unsupported |
| slirp4netns | 1.07 Gbps | 2.78 Gbps | 4.55 Gbps | 9.21 Gbps |
slirp4netns is faster than vde_plug and VPNKit because slirp4netns is optimized to avoid copying packets across the namespaces.
The latest revision of slirp4netns is regularly benchmarked (make benchmark) on CI.
Build dependencies (apt-get):
$ sudo apt-get install libglib2.0-dev libslirp-dev libcap-dev libseccomp-devBuild dependencies (dnf):
$ sudo dnf install glib2-devel libslirp-devel libcap-devel libseccomp-develInstallation steps:
$ ./autogen.sh
$ ./configure --prefix=/usr
$ make
$ sudo make installslirp4netns as a static binary, run ./configure with LDFLAGS=-static.--prefix to $HOME, you don't need to run make install with sudo.See vendor/README.md.