5.1.14 Network Namespace Support

Prior to using network namespace support in MySQL, these host system prerequisites must be satisfied:

The instructions in the following example set up network namespaces named red and blue. The names you choose may differ, as may the network addresses and interfaces on your host system.

Invoke the commands shown here either as the root operating system user or by prefixing each command with sudo. For example, to invoke the ip or setcap command if you are not root, use sudo ip or sudo setcap.

To configure network namespaces, use the ip command. For some operations, the ip command must execute within a particular namespace (which must already exist). In such cases, begin the command like this:

ip netns exec namespace_name

For example, this command executes within the red namespace to bring up the loopback interface:

ip netns exec red ip link set lo up

To add namespaces named red and blue, each with its own virtual Ethernet device used as a link between namespaces and its own loopback interface:

ip netns add red
ip link add veth-red type veth peer name vpeer-red
ip link set vpeer-red netns red
ip addr add 192.0.2.1/24 dev veth-red
ip link set veth-red up
ip netns exec red ip addr add 192.0.2.2/24 dev vpeer-red
ip netns exec red ip link set vpeer-red up
ip netns exec red ip link set lo up

ip netns add blue
ip link add veth-blue type veth peer name vpeer-blue
ip link set vpeer-blue netns blue
ip addr add 198.51.100.1/24 dev veth-blue
ip link set veth-blue up
ip netns exec blue ip addr add 198.51.100.2/24 dev vpeer-blue
ip netns exec blue ip link set vpeer-blue up
ip netns exec blue ip link set lo up

# if you want to enable inter-subnet routing...
sysctl net.ipv4.ip_forward=1
ip netns exec red ip route add default via 192.0.2.1
ip netns exec blue ip route add default via 198.51.100.1

A diagram of the links between namespaces looks like this:

red              global           blue

192.0.2.2   <=>  192.0.2.1
(vpeer-red)      (veth-red)

                 198.51.100.1 <=> 198.51.100.2
                 (veth-blue)      (vpeer-blue)

To check which namespaces and links exist:

ip netns list
ip link list

To see the routing tables for the global and named namespaces:

ip route show
ip netns exec red ip route show
ip netns exec blue ip route show

To remove the red and blue links and namespaces:

ip link del veth-red
ip link del veth-blue

ip netns del red
ip netns del blue

sysctl net.ipv4.ip_forward=0

So that the MySQL binaries that include network namespace support can actually use namespaces, you must grant them the CAP_SYS_ADMIN capability. The following setcap commands assume that you have changed location to the directory containing your MySQL binaries (adjust the pathname for your system as necessary):

cd /usr/local/mysql/bin

To grant CAP_SYS_ADMIN capability to the appropriate binaries:

setcap cap_sys_admin+ep ./mysqld
setcap cap_sys_admin+ep ./mysql
setcap cap_sys_admin+ep ./mysqlxtest

To check CAP_SYS_ADMIN capability:

$> getcap ./mysqld ./mysql ./mysqlxtest
./mysqld = cap_sys_admin+ep
./mysql = cap_sys_admin+ep
./mysqlxtest = cap_sys_admin+ep

To remove CAP_SYS_ADMIN capability:

setcap -r ./mysqld
setcap -r ./mysql
setcap -r ./mysqlxtest

[ERROR] [MY-013408] [Server] setns() failed with error 'Operation not permitted'

ERROR: Network namespace error: Operation not permitted

Assuming that the preceding host system prerequisites have been satisfied, MySQL enables configuring the server-side namespace for the listening (inbound) side of connections and the client-side namespace for the outbound side of connections.

On the server side, the bind_address, admin_address, and mysqlx_bind_address system variables have extended syntax for specifying the network namespace to use for a given IP address or host name on which to listen for incoming connections. To specify a namespace for an address, add a slash and the namespace name. For example, a server my.cnf file might contain these lines:

[mysqld]
bind_address = 127.0.1.1,192.0.2.2/red,198.51.100.2/blue
admin_address = 102.0.2.2/red
mysqlx_bind_address = 102.0.2.2/red

These rules apply:

If an error occurs during server startup for attempts to use a namespace, the server does not start. If errors occur for X Plugin during plugin initialization such that it is unable to bind to any address, the plugin fails its initialization sequence and the server does not load it.

On the client side, a network namespace can be specified in these contexts:

The following example sets up a MySQL server that listens for connections in the global, red, and blue namespaces, and shows how to configure accounts that connect from the red and blue namespaces. It is assumed that the red and blue namespaces have already been created as shown in Host System Prerequisites.

For replication monitoring purposes, these information sources have a column that displays the applicable network namespace for connections: