Current state of Network Namespaces (NETNS, CLONE_NEWNET)?

Sorry for the shotgun mail, but in the end, it's
not clear who can best answer my question(s).

I'm currently trying to add documentation of all of the undocumented CLONE_* flags. One of these is CLONE_NEWNET, and I could use (quite a lot of) help.

My questions:

What is the current state of the network namespace implementation? Is it complete?

What objects are considered part of the network namespace, and therefore distinct for a new network namespace?

Is there any documentation for network namespaces
already?

Are there any test programs for network namespaces?

Thanks,

Michael

Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git
man-pages online: http://www.kernel.org/doc/man-pages/online_pages.html
Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html

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No. It is fairly close though and there is general agreement on what it is.

ipv4 and ipv6 are mostly complete and useable.
ip tables support is in progress.
sysfs support is in progress.

decnet and other protocols are possible but there is not currently any active work in that direction.

A network namespace is to user space a new logical instance of the kernel networking stack.

The full kernel networking stack is available in the initial network namespace. A subset of the kernel networking stack is available in other network namespaces depending upon how much code has been converted.

Network devices live in exactly one network namespace.

Not much. Nor should it need much unique documentation.

Currently the truly unique command is:
ip link set <netdev> netns <pid>

Which moves a network device from one network namespace to another.

There are the veth pair network devices.
Designed so you can put one end in one network namespace and another end in another network namespace.

There is the macvlan driver that can be sued to create multiple mac addresses for your ethernet devices allowing native speed inside of a network namespace on a machine with only one NIC.

There is the fact that /proc/net is now network namespace unique There is the interesting games we play with /proc/sys/ so we have per network namespace sysctls.

Other unique network namespace work under discussion.
- Unix domain sockets across network namespaces.
Is doable but we haven't considered all of the technical details.
- The ongoing discussion about how we provide a more managable interface to network namespaces for people doing the whole linux-vrf thing.

Eric

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iptables will be mostly complete in 2.6.28.

It is not complete but mostly usable for ipv4 and ipv6.

There is a network namespace status I filled at:

http://lxc.sourceforge.net/network/status.php

It should be up-to-date.

The network namespace brings isolation from the layer-2 to upper layers.

http://lxc.sourceforge.net/network.php
http://lxc.sourceforge.net/doc/sigops/appcr.pdf

http://sourceforge.net/projects/lxc/

follow the README page. It is still in development but mainly usable - any feedbacks are welcome :)

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And also at:

http://ltp.cvs.sourceforge.net/viewvc/ltp/ltp/testcases/kernel/containers/

Regards--
Subrata

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Based on my reading of some of the kernel source, various documentation that I've now read, and comments I received from people to my earlier mail ("Current state of Network Namespaces (NETNS, CLONE_NEWNET)?"), I've written the patch below to document the CLONE_NEWNET clone(2) flag. Fixes and suggestions for improvements welcome.

Cheers,

Michael

CLONE_NEWNET (since Linux 2.6.24)
(The implementation of this flag is not yet com- plete, but probably will be mostly complete by about Linux 2.6.28.)

If CLONE_NEWNET is set, then create the process in a new network namespace. If this flag is not set, then (as with fork(2)), the process is created in the same network namespace as the calling process. This flag is intended for the implementation of containers.

A network namespace provides an isolated view of the networking stack (network device interfaces, IPv4 and IPv6 protocol stacks, IP routing tables, firewall rules, the /proc/net and /sys/class/net directory trees, sockets, etc.). A physical net- work device can live in exactly one network names- pace. A virtual network device ("veth") pair pro- vides a pipe-like abstraction that can be used to create tunnels between network namespaces, and can be used to create a bridge to a physical network device in another namespace.

Use of this flag requires: a kernel configured with the CONFIG_NET_NS option and that the process be privileged (CAP_SYS_ADMIN).

@@ -286,10 +285,41 @@ and
 configuration options and that the process be privileged
 .RB ( CAP_SYS_ADMIN ).
 This flag can't be specified in conjunction with
 .BR CLONE_SYSVSEM .
 .TP
+.BR CLONE_NEWNET " (since Linux 2.6.24)"
+(The implementation of this flag is not yet complete,
+but probably will be mostly complete by about Linux 2.6.28.)
+
+If
+.B CLONE_NEWNET
+is set, then create the process in a new network namespace.
+If this flag is not set, then (as with
+.BR fork (2)),
+the process is created in the same network namespace as
+the calling process.
+This flag is intended for the implementation of containers.
+
+A network namespace provides an isolated view of the networking stack
+(network device interfaces, IPv4 and IPv6 protocol stacks,
+IP routing tables, firewall rules, the
+.I /proc/net
+and
+.I /sys/class/net
+directory trees, sockets, etc.).
+A physical network device can live in exactly one
+network namespace.
+A virtual network device ("veth") pair provides a pipe-like abstraction
+that can be used to create tunnels between network namespaces,
+and can be used to create a bridge to a physical network device
+in another namespace.
+
+Use of this flag requires: a kernel configured with the
+.B CONFIG_NET_NS
+option and that the process be privileged
+.RB ( CAP_SYS_ADMIN ).
+.TP
 .BR CLONE_NEWNS " (since Linux 2.4.19)"
 Start the child in a new mount namespace.
 
 Every process lives in a mount namespace.

The
@@ -822,10 +852,18 @@ but the kernel was not configured with the
and
.BR CONFIG_IPC_NS
options.
.TP
.B EINVAL
+.BR CLONE_NEWNET
+was specified in
+.IR flags ,
+but the kernel was not configured with the
+.B CONFIG_NET_NS
+option.
+.TP
+.B EINVAL
.BR CLONE_NEWPID
was specified in
.IR flags ,
but the kernel was not configured with the
.B CONFIG_PID_NS
@@ -844,10 +882,11 @@ Cannot allocate sufficient memory to allocate a task structure for the
child, or to copy those parts of the caller's context that need to be copied.
.TP
.B EPERM
.BR CLONE_NEWIPC ,
+.BR CLONE_NEWNET ,
.BR CLONE_NEWNS ,
.BR CLONE_NEWPID ,
or
.BR CLONE_NEWUTS
was specified by a non-root process (process without \fBCAP_SYS_ADMIN\fP).