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.
Example Configuration
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;
}
Directives
Syntax:
ssl_preread on | off;
Default:
ssl_preread off;
Context:
stream, server
Enables extracting information from the ClientHello message at the preread phase.
Embedded Variables
$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.
