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106 lines
3.5 KiB
106 lines
3.5 KiB
Linux network namespace support for HAProxy
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===========================================
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HAProxy supports proxying between Linux network namespaces. This
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feature can be used, for example, in a multi-tenant networking
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environment to proxy between different networks. HAProxy can also act
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as a front-end proxy for non namespace-aware services.
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The proxy protocol has been extended to support transferring the
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namespace information, so the originating namespace information can be
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kept. This is useful when chaining multiple proxies and services.
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To enable Linux namespace support, compile HAProxy with the `USE_NS=1`
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make option.
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## Setting up namespaces on Linux
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To create network namespaces, use the 'ip netns' command. See the
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manual page ip-netns(8) for details.
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Make sure that the file descriptors representing the network namespace
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are located under `/var/run/netns`.
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For example, you can create a network namespace and assign one of the
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networking interfaces to the new namespace:
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```
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$ ip netns add netns1
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$ ip link set eth7 netns netns1
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```
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## Listing namespaces in the configuration file
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HAProxy uses namespaces explicitly listed in its configuration file.
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If you are not using namespace information received through the proxy
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protocol, this usually means that you must specify namespaces for
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listeners and servers in the configuration file with the 'namespace'
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keyword.
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However, if you're using the namespace information received through
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the proxy protocol to determine the namespace of servers (see
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'namespace * below'), you have to explicitly list all allowed
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namespaces in the namespace_list section of your configuration file:
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```
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namespace_list
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namespace netns1
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namespace netns2
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```
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## Namespace information flow
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The haproxy process always runs in the namespace it was started on.
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This is the default namespace.
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The bind addresses of listeners can have their namespace specified in
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the configuration file. Unless specified, sockets associated with
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listener bind addresses are created in the default namespace. For
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example, this creates a listener in the netns2 namespace:
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```
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frontend f_example
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bind 192.168.1.1:80 namespace netns2
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default_backend http
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```
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Each client connection is associated with its source namespace. By
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default, this is the namespace of the bind socket it arrived on, but
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can be overridden by information received through the proxy protocol.
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Proxy protocol v2 supports transferring namespace information, so if
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it is enabled for the listener, it can override the associated
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namespace of the connection.
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Servers can have their namespaces specified in the configuration file
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with the 'namespace' keyword:
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```
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backend b_example
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server s1 192.168.1.100:80 namespace netns2
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```
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If no namespace is set for a server, it is assumed that it is in the
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default namespace. When specified, outbound sockets to the server are
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created in the network namespace configured. To create the outbound
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(server) connection in the namespace associated with the client, use
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the '*' namespace. This is especially useful when using the
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destination address and namespace received from the proxy protocol.
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```
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frontend f_example
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bind 192.168.1.1:9990 accept-proxy
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default_backend b_example
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backend b_example
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mode tcp
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source 0.0.0.0 usesrc clientip
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server snodes * namespace *
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```
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If HAProxy is configured to send proxy protocol v2 headers to the
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server, the outgoing header will always contain the namespace
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associated with the client connection, not the namespace configured
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for the server.
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