h2: add prior knowledge support

include/libwebsockets/lws-client.h

@@ -58,6 +58,7 @@ enum lws_client_connect_ssl_connection_flags {
 		 * HTTP/2:   always possible... uses parallel streams
 		 */
 	LCCSCF_MUXABLE_STREAM			= (1 << 17),
+	LCCSCF_H2_PRIOR_KNOWLEDGE		= (1 << 18)
 };
 
 /** struct lws_client_connect_info - parameters to connect with when using

include/libwebsockets/lws-context-vhost.h

@@ -221,6 +221,11 @@
 #define LWS_SERVER_OPTION_GLIB					 (1ll << 33)
 	/**< (CTX) Use glib event loop */
 
+#define LWS_SERVER_OPTION_H2_PRIOR_KNOWLEDGE				(1ll << 34)
+	/**< (VH) Tell the vhost to treat plain text http connections as
+	 * H2 with prior knowledge (no upgrade request involved)
+	 */
+
 	/****** add new things just above ---^ ******/
 
 

lib/roles/h1/ops-h1.c

@@ -907,11 +907,20 @@ rops_adoption_bind_h1(struct lws *wsi, int type, const char *vh_prot_name)
 		return 1;
 	}
 
-	lws_role_transition(wsi, LWSIFR_SERVER, (type & LWS_ADOPT_ALLOW_SSL) ?
-			    LRS_SSL_INIT : LRS_HEADERS, &role_ops_h1);
+	/* If Non-TLS and HTTP2 prior knowledge is enabled, skip to clear text HTTP2 */
+
+#if defined(LWS_WITH_HTTP2)
+	if ((!(type & LWS_ADOPT_ALLOW_SSL)) && (wsi->vhost->options & LWS_SERVER_OPTION_H2_PRIOR_KNOWLEDGE)) {
+		lwsl_info("http/2 prior knowledge\n");
+		lws_role_call_alpn_negotiated(wsi, "h2");
+	}
+	else
+#endif
+		lws_role_transition(wsi, LWSIFR_SERVER, (type & LWS_ADOPT_ALLOW_SSL) ?
+				LRS_SSL_INIT : LRS_HEADERS, &role_ops_h1);
 
 	/*
-	 * We have to bind to h1 as a default even when we're actually going to
+	 * Otherwise, we have to bind to h1 as a default even when we're actually going to
 	 * replace it as an h2 bind later.  So don't take this seriously if the
 	 * default is disabled (ws upgrade caees properly about it)
 	 */

lib/roles/h2/http2.c

@@ -765,6 +765,11 @@ int lws_h2_do_pps_send(struct lws *wsi)
 #endif
 			if (lws_is_ssl(lws_get_network_wsi(wsi)))
 				break;
+
+			if (wsi->vhost->options &
+				LWS_SERVER_OPTION_H2_PRIOR_KNOWLEDGE)
+				break;
+
 			/*
 			 * we need to treat the headers from the upgrade as the
 			 * first job.  So these need to get shifted to sid 1.

lib/roles/http/client/client-http.c

@@ -232,8 +232,13 @@ start_ws_handshake:
 				cce = ebuf;
 				goto bail3;
 			}
-		} else
+		} else {
 			wsi->tls.ssl = NULL;
+			if(wsi->flags & LCCSCF_H2_PRIOR_KNOWLEDGE) {
+				lwsl_info("h2 prior knowledge\n");
+				lws_role_call_alpn_negotiated(wsi, "h2");
+			}
+		}
 #endif
 #if defined(LWS_WITH_DETAILED_LATENCY)
 		if (context->detailed_latency_cb) {
@@ -248,14 +253,18 @@ start_ws_handshake:
 #if defined (LWS_WITH_HTTP2)
 		if (wsi->client_h2_alpn) {
 			/*
-			 * We connected to the server and set up tls, and
-			 * negotiated "h2".
+			 * We connected to the server and set up tls and
+			 * negotiated "h2" or connected as clear text
+			 * with http/2 prior knowledge.
 			 *
 			 * So this is it, we are an h2 master client connection
 			 * now, not an h1 client connection.
 			 */
+
 #if defined(LWS_WITH_TLS)
-			lws_tls_server_conn_alpn(wsi);
+			if (wsi->tls.use_ssl & LCCSCF_USE_SSL) {
+				lws_tls_server_conn_alpn(wsi);
+			}
 #endif
 
 			/* send the H2 preface to legitimize the connection */

minimal-examples/http-client/minimal-http-client/minimal-http-client.c

@@ -204,6 +204,9 @@ system_notify_cb(lws_state_manager_t *mgr, lws_state_notify_link_t *link,
 	if (lws_cmdline_option(a->argc, a->argv, "--h1"))
 		i.alpn = "http/1.1";
 
+	if (lws_cmdline_option(a->argc, a->argv, "--h2-prior-knowledge"))
+		i.ssl_connection |= LCCSCF_H2_PRIOR_KNOWLEDGE;
+
 	if ((p = lws_cmdline_option(a->argc, a->argv, "-p")))
 		i.port = atoi(p);
 

minimal-examples/http-server/minimal-http-server/minimal-http-server.c

@@ -72,6 +72,9 @@ int main(int argc, const char **argv)
 	info.options =
 		LWS_SERVER_OPTION_HTTP_HEADERS_SECURITY_BEST_PRACTICES_ENFORCE;
 
+	if (lws_cmdline_option(argc, argv, "--h2-prior-knowledge"))
+		info.options |= LWS_SERVER_OPTION_H2_PRIOR_KNOWLEDGE;
+
 	context = lws_create_context(&info);
 	if (!context) {
 		lwsl_err("lws init failed\n");