SSL: Next Protocol Negotiation extension support.

Not only this is useful for the upcoming SPDY support, but it can
also help to improve HTTPS performance by enabling TLS False Start
in Chrome/Chromium browsers [1].  So, we always enable NPN for HTTPS
if it is supported by OpenSSL.

[1] http://www.imperialviolet.org/2012/04/11/falsestart.html


git-svn-id: svn://svn.nginx.org/nginx/trunk@5107 73f98a42-aea0-e011-b76d-00259023448c

src/http/modules/ngx_http_ssl_module.c

@@ -18,6 +18,11 @@ typedef ngx_int_t (*ngx_ssl_variable_handler_pt)(ngx_connection_t *c,
 #define NGX_DEFAULT_ECDH_CURVE  "prime256v1"
 
 
+#ifdef TLSEXT_TYPE_next_proto_neg
+static int ngx_http_ssl_npn_advertised(ngx_ssl_conn_t *ssl_conn,
+    const unsigned char **out, unsigned int *outlen, void *arg);
+#endif
+
 static ngx_int_t ngx_http_ssl_static_variable(ngx_http_request_t *r,
     ngx_http_variable_value_t *v, uintptr_t data);
 static ngx_int_t ngx_http_ssl_variable(ngx_http_request_t *r,
@@ -262,6 +267,30 @@ static ngx_http_variable_t  ngx_http_ssl_vars[] = {
 static ngx_str_t ngx_http_ssl_sess_id_ctx = ngx_string("HTTP");
 
 
+#ifdef TLSEXT_TYPE_next_proto_neg
+
+#define NGX_HTTP_NPN_ADVERTISE  "\x08http/1.1"
+
+static int
+ngx_http_ssl_npn_advertised(ngx_ssl_conn_t *ssl_conn,
+    const unsigned char **out, unsigned int *outlen, void *arg)
+{
+#if (NGX_DEBUG)
+    ngx_connection_t  *c;
+
+    c = ngx_ssl_get_connection(ssl_conn);
+    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "SSL NPN advertised");
+#endif
+
+    *out = (unsigned char *) NGX_HTTP_NPN_ADVERTISE;
+    *outlen = sizeof(NGX_HTTP_NPN_ADVERTISE) - 1;
+
+    return SSL_TLSEXT_ERR_OK;
+}
+
+#endif
+
+
 static ngx_int_t
 ngx_http_ssl_static_variable(ngx_http_request_t *r,
     ngx_http_variable_value_t *v, uintptr_t data)
@@ -490,6 +519,11 @@ ngx_http_ssl_merge_srv_conf(ngx_conf_t *cf, void *parent, void *child)
 
 #endif
 
+#ifdef TLSEXT_TYPE_next_proto_neg
+    SSL_CTX_set_next_protos_advertised_cb(conf->ssl.ctx,
+                                          ngx_http_ssl_npn_advertised, NULL);
+#endif
+
     cln = ngx_pool_cleanup_add(cf->pool, 0);
     if (cln == NULL) {
         return NGX_CONF_ERROR;