Changed the Diffie Hellman parameter maximum size

This introduces the variable haproxy_ssl_dh_param

It sets the maximum size of the DH parameters used
for generating key in DHE key exchange.

Higher values increase CPU load but is more secure.

This value is ignored if static DH params are given
in cert file.

Change-Id: Idca02a8337fa3790ddfb849d9e2e87d60076c399

playbooks/roles/haproxy_server/defaults/main.yml

@@ -71,6 +71,7 @@ haproxy_bind_on_non_local: False
 
 ## haproxy SSL
 haproxy_ssl: no
+haproxy_ssl_dh_param: 2048
 haproxy_ssl_self_signed_regen: no
 haproxy_ssl_cert: /etc/ssl/certs/haproxy.cert
 haproxy_ssl_key: /etc/ssl/private/haproxy.key

playbooks/roles/haproxy_server/templates/haproxy.cfg.j2

@@ -10,6 +10,7 @@ global
         maxconn 4096
         tune.bufsize 384000
         stats socket /var/run/haproxy.stat level admin mode 600
+        {% if haproxy_ssl | bool %}tune.ssl.default-dh-param {{haproxy_ssl_dh_param}}{% endif %}
 
 defaults
         log global