Stream: proxy_ssl_conf_command directive.

Similarly to ssl_conf_command, proxy_ssl_conf_command can be used to
set arbitrary OpenSSL configuration parameters as long as nginx is
compiled with OpenSSL 1.0.2 or later, when connecting to upstream
servers with SSL.  Full list of available configuration commands
can be found in the SSL_CONF_cmd manual page
(https://www.openssl.org/docs/man1.1.1/man3/SSL_CONF_cmd.html).
diff --git a/src/stream/ngx_stream_proxy_module.c b/src/stream/ngx_stream_proxy_module.c
index db11dd8..0c86083 100644
--- a/src/stream/ngx_stream_proxy_module.c
+++ b/src/stream/ngx_stream_proxy_module.c
@@ -49,6 +49,7 @@
     ngx_str_t                        ssl_certificate;
     ngx_str_t                        ssl_certificate_key;
     ngx_array_t                     *ssl_passwords;
+    ngx_array_t                     *ssl_conf_commands;
 
     ngx_ssl_t                       *ssl;
 #endif
@@ -94,6 +95,8 @@
 static ngx_int_t ngx_stream_proxy_send_proxy_protocol(ngx_stream_session_t *s);
 static char *ngx_stream_proxy_ssl_password_file(ngx_conf_t *cf,
     ngx_command_t *cmd, void *conf);
+static char *ngx_stream_proxy_ssl_conf_command_check(ngx_conf_t *cf, void *post,
+    void *data);
 static void ngx_stream_proxy_ssl_init_connection(ngx_stream_session_t *s);
 static void ngx_stream_proxy_ssl_handshake(ngx_connection_t *pc);
 static void ngx_stream_proxy_ssl_save_session(ngx_connection_t *c);
@@ -112,6 +115,9 @@
     { ngx_null_string, 0 }
 };
 
+static ngx_conf_post_t  ngx_stream_proxy_ssl_conf_command_post =
+    { ngx_stream_proxy_ssl_conf_command_check };
+
 #endif
 
 
@@ -331,6 +337,13 @@
       0,
       NULL },
 
+    { ngx_string("proxy_ssl_conf_command"),
+      NGX_STREAM_MAIN_CONF|NGX_STREAM_SRV_CONF|NGX_CONF_TAKE2,
+      ngx_conf_set_keyval_slot,
+      NGX_STREAM_SRV_CONF_OFFSET,
+      offsetof(ngx_stream_proxy_srv_conf_t, ssl_conf_commands),
+      &ngx_stream_proxy_ssl_conf_command_post },
+
 #endif
 
       ngx_null_command
@@ -1008,6 +1021,17 @@
 }
 
 
+static char *
+ngx_stream_proxy_ssl_conf_command_check(ngx_conf_t *cf, void *post, void *data)
+{
+#ifndef SSL_CONF_FLAG_FILE
+    return "is not supported on this platform";
+#endif
+
+    return NGX_CONF_OK;
+}
+
+
 static void
 ngx_stream_proxy_ssl_init_connection(ngx_stream_session_t *s)
 {
@@ -1985,6 +2009,7 @@
     conf->ssl_verify = NGX_CONF_UNSET;
     conf->ssl_verify_depth = NGX_CONF_UNSET_UINT;
     conf->ssl_passwords = NGX_CONF_UNSET_PTR;
+    conf->ssl_conf_commands = NGX_CONF_UNSET_PTR;
 #endif
 
     return conf;
@@ -2072,6 +2097,9 @@
 
     ngx_conf_merge_ptr_value(conf->ssl_passwords, prev->ssl_passwords, NULL);
 
+    ngx_conf_merge_ptr_value(conf->ssl_conf_commands,
+                              prev->ssl_conf_commands, NULL);
+
     if (conf->ssl_enable && ngx_stream_proxy_set_ssl(cf, conf) != NGX_OK) {
         return NGX_CONF_ERROR;
     }
@@ -2156,6 +2184,12 @@
         return NGX_ERROR;
     }
 
+    if (ngx_ssl_conf_commands(cf, pscf->ssl, pscf->ssl_conf_commands)
+        != NGX_OK)
+    {
+        return NGX_ERROR;
+    }
+
     return NGX_OK;
 }