TCP is the protocol for many popular applications and services, such as LDAP, MySQL, and RTMP. UDP (User Datagram Protocol) is the protocol for many popular non-transactional applications, such as DNS, syslog, and RADIUS.

APISIX can dynamically load balancing TCP/UDP proxy. In Nginx world, we call TCP/UDP proxy to stream proxy, we followed this statement.

How to enable stream proxy?

Setting the stream_proxy option in conf/config.yaml, specify a list of addresses that require dynamic proxy. By default, no stream proxy is enabled.

apisix:
  stream_proxy: # TCP/UDP proxy
    tcp: # TCP proxy address list
      - 9100
      - "127.0.0.1:9101"
    udp: # UDP proxy address list
      - 9200
      - "127.0.0.1:9211"

If apisix.enable_admin is true, both HTTP and stream proxy are enabled with the configuration above.

If you have set the enable_admin to false, and need to enable both HTTP and stream proxy, set the only to false:

apisix:
  enable_admin: false
  stream_proxy: # TCP/UDP proxy
    only: false
    tcp: # TCP proxy address list
      - 9100

How to set route?

Here is a mini example:

curl http://127.0.0.1:9080/apisix/admin/stream_routes/1 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -d '
{
    "remote_addr": "127.0.0.1",
    "upstream": {
        "nodes": {
            "127.0.0.1:1995": 1
        },
        "type": "roundrobin"
    }
}'

It means APISIX will proxy the request to 127.0.0.1:1995 which the client remote address is 127.0.0.1.

For more use cases, please take a look at test case.

More route match options

And we can add more options to match a route. Currently stream route configuration supports 3 fields for filtering:

• server_addr: The address of the APISIX server that accepts the L4 stream connection.
• server_port: The port of the APISIX server that accepts the L4 stream connection.
• remote_addr: The address of client from which the request has been made.

Here is an example:

curl http://127.0.0.1:9080/apisix/admin/stream_routes/1 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -d '
{
    "server_addr": "127.0.0.1",
    "server_port": 2000,
    "upstream": {
        "nodes": {
            "127.0.0.1:1995": 1
        },
        "type": "roundrobin"
    }
}'

It means APISIX will proxy the request to 127.0.0.1:1995 when the server address is 127.0.0.1 and the server port is equal to 2000.

Let's take another real world example:

1. Put this config inside config.yaml

   apisix:
     stream_proxy: # TCP/UDP proxy
       tcp: # TCP proxy address list
         - 9100 # by default uses 0.0.0.0
         - "127.0.0.10:9101"

2. Now run a mysql docker container and expose port 3306 to the host

   $ docker run --name mysql -e MYSQL_ROOT_PASSWORD=toor -p 3306:3306 -d mysql
   # check it using a mysql client that it works
   $ mysql --host=127.0.0.1 --port=3306 -u root -p
   Enter password:
   Welcome to the MySQL monitor.  Commands end with ; or \g.
   Your MySQL connection id is 25
   ...
   mysql>

3. Now we are going to create a stream route with server filtering:

   curl http://127.0.0.1:9080/apisix/admin/stream_routes/1 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -d '
   {
       "server_addr": "127.0.0.10",
       "server_port": 9101,
       "upstream": {
           "nodes": {
               "127.0.0.1:3306": 1
           },
           "type": "roundrobin"
       }
   }'

   It only forwards the request to the mysql upstream whenever a connection is received at APISIX server 127.0.0.10 and port 9101. Let's test that behaviour:

4. Making a request to 9100 (stream proxy port enabled inside config.yaml), filter matching fails.

   $ mysql --host=127.0.0.1 --port=9100 -u root -p
   Enter password:
   ERROR 2013 (HY000): Lost connection to MySQL server at 'reading initial communication packet', system error: 2
   

   Instead making a request to the APISIX host and port where the filter matching succeeds:

   mysql --host=127.0.0.10 --port=9101 -u root -p
   Enter password:
   Welcome to the MySQL monitor.  Commands end with ; or \g.
   Your MySQL connection id is 26
   ...
   mysql>

Read Admin API's Stream Route section for the complete options list.

Accept TLS over TCP connection

APISIX can accept TLS over TCP connection.

First of all, we need to enable TLS for the TCP address:

apisix:
  stream_proxy: # TCP/UDP proxy
    tcp: # TCP proxy address list
      - addr: 9100
        tls: true

Second, we need to configure certificate for the given SNI. See Admin API's SSL section for how to do. mTLS is also supported, see Protect Route for how to do.

Third, we need to configure a stream route to match and proxy it to the upstream:

curl http://127.0.0.1:9080/apisix/admin/stream_routes/1 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -d '
{
    "upstream": {
        "nodes": {
            "127.0.0.1:1995": 1
        },
        "type": "roundrobin"
    }
}'

When the connection is TLS over TCP, we can use the SNI to match a route, like:

curl http://127.0.0.1:9080/apisix/admin/stream_routes/1 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -d '
{
    "sni": "a.test.com",
    "upstream": {
        "nodes": {
            "127.0.0.1:5991": 1
        },
        "type": "roundrobin"
    }
}'

In this case, a connection handshaked with SNI a.test.com will be proxied to 127.0.0.1:5991.

Proxy to TLS over TCP upstream

APISIX also supports proxying to TLS over TCP upstream.

curl http://127.0.0.1:9080/apisix/admin/stream_routes/1 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -d '
{
    "upstream": {
        "scheme": "tls",
        "nodes": {
            "127.0.0.1:1995": 1
        },
        "type": "roundrobin"
    }
}'

By setting the scheme to "tls", APISIX will do TLS handshake with the upstream.

When the client is also speaking TLS over TCP, the SNI from the client will pass through to the upstream. Otherwise, a dummy SNI "apisix_backend" will be used.