Module ngx_stream_ssl_preread_module

The ngx_stream_ssl_preread_module module (1.11.5) allows extracting information from the ClientHello message without terminating SSL/TLS, for example, the server name requested through SNI or protocols advertised in ALPN. This module is not built by default, it should be enabled with the --with-stream_ssl_preread_module configuration parameter.

Selecting an upstream based on server name:

map $ssl_preread_server_name $name {
 backend.example.com backend;
 default backend2;
}
upstream backend {
 server 192.168.0.1:12345;
 server 192.168.0.2:12345;
}
upstream backend2 {
 server 192.168.0.3:12345;
 server 192.168.0.4:12345;
}
server {
 listen 12346;
 proxy_pass $name;
 ssl_preread on;
}

Selecting an upstream based on protocol:

map $ssl_preread_alpn_protocols $proxy {
 ~\bh2\b 127.0.0.1:8001;
 ~\bhttp/1.1\b 127.0.0.1:8002;
 ~\bxmpp-client\b 127.0.0.1:8003;
}
server {
 listen 9000;
 proxy_pass $proxy;
 ssl_preread on;
}

Selecting an upstream based on SSL protocol version:

map $ssl_preread_protocol $upstream {
 "" ssh.example.com:22;
 "TLSv1.2" new.example.com:443;
 default tls.example.com:443;
}
# ssh and https on the same port
server {
 listen 192.168.0.1:443;
 proxy_pass $upstream;
 ssl_preread on;
}

ssl_preread off;

Enables extracting information from the ClientHello message at the preread phase.

$ssl_preread_protocol

the highest SSL protocol version supported by the client (1.15.2)

$ssl_preread_server_name

server name requested through SNI

$ssl_preread_alpn_protocols

list of protocols advertised by the client through ALPN (1.13.10). The values are separated by commas.