Create a document to describe the how it works and known limitations and update the NEWS accordingly.
Signed-off-by: Flavio Leitner <f...@sysclose.org> --- Documentation/topics/networking-namespaces.rst | 69 ++++++++++++++++++++++++++ NEWS | 1 + 2 files changed, 70 insertions(+) create mode 100644 Documentation/topics/networking-namespaces.rst diff --git a/Documentation/topics/networking-namespaces.rst b/Documentation/topics/networking-namespaces.rst new file mode 100644 index 000000000..96589b513 --- /dev/null +++ b/Documentation/topics/networking-namespaces.rst @@ -0,0 +1,69 @@ +.. + Licensed under the Apache License, Version 2.0 (the "License"); you may + not use this file except in compliance with the License. You may obtain + a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, WITHOUT + WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the + License for the specific language governing permissions and limitations + under the License. + + Convention for heading levels in Open vSwitch documentation: + + ======= Heading 0 (reserved for the title in a document) + ------- Heading 1 + ~~~~~~~ Heading 2 + +++++++ Heading 3 + ''''''' Heading 4 + + Avoid deeper levels because they do not render well. + +=========================================== +Open vSwitch Networking Namespaces on Linux +=========================================== + +The Open vSwitch has networking namespaces basic support on Linux. That allows +ovs-vswitchd daemon to continue tracking status and statistics after moving a +port to another networking namespace. + + +How It Works +------------ + +The daemon ovs-vswitchd runs on what is called parent network namespace. It +listens to netlink event messages from all networking namespaces (netns) +with an identifier on the parent. Each netlink message contains the network +namespace identifier (netnsid) as ancillary data which is used to match the +event to the corresponding port. + +The ovs-vswitchd uses an extended openvswitch kernel API _ to get the +current netnsid (stored in struct netdev_linux) and statistics from a specific +port. The netnsid remains cached in userspace until a changing event is +received, for example, when the port is moved to another network namespace. + +Using another extended kernel API _, the daemon gets port's information +such as flags, MTU, MAC address and ifindex from a port already in another +namespace. + +The upstream kernel 4.15 includes the necessary changes for the basic support. +In case of the running kernel doesn't provide the APIs, the daemon falls back +to the previous behavior. + +..  Request cmd: OVS_VPORT_CMD_GET, attribute: OVS_VPORT_ATTR_NETNSID +..  Request cmd: RTM_GETLINK passing IFLA_IF_NETNSID attribute. + + +Limitations +----------- + +Currently it is only possible to retrieve the information listed in the +above section. Most of other operations, for example querying MII or +setting MTU, lacks the proper API in the kernel, so they remain unsupported. + +In most use cases that needs to move ports to another networking namespaces +should use veth pairs instead because it offers a cleaner and more robust +solution with no noticeable performance penalty. + diff --git a/NEWS b/NEWS index 757d648a1..83fbe6038 100644 --- a/NEWS +++ b/NEWS @@ -6,6 +6,7 @@ Post-v2.9.0 "table#". These are not helpful names for the purpose of accepting and displaying table names, so now tables by default have no names. * The "null" interface type, deprecated since 2013, has been removed. + * Add minimum network namespace support for Linux. - ovs-ofctl: * ovs-ofctl now accepts and display table names in place of numbers. By default it always accepts names and in interactive use it displays them; -- 2.14.3 _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev