extensions fix deflate stream vs mux and veto it on mux children

This patch gets deflate-stream working with x-google-mux.

It adds a clean veto system where are extension can veto the proposal
of any extension when opening a new connection.  x-google-mux uses that
in its callback to defeat any use of deflate-stream on mux children.

However deflate stream is allowed on the parent connection and works
transparently now alongside x-google-mux.

Signed-off-by: Andy Green <andy@warmcat.com>

5 files changed, 136 insertions, 77 deletions

diff --git a/lib/extension-x-google-mux.c b/lib/extension-x-google-mux.c
index 13bc461..95253b4 100644
--- a/lib/extension-x-google-mux.c
+++ b/lib/extension-x-google-mux.c
@@ -5,6 +5,7 @@
 
 static int ongoing_subchannel;
 static struct libwebsocket * tag_with_parent = NULL;
+static int client_handshake_generation_is_for_mux_child;
 
 static int lws_addheader_mux_opcode(unsigned char *pb, int len)
 {
@@ -96,8 +97,10 @@ static int lws_ext_x_google_mux__send_addchannel(
 
 	wsi_child->ietf_spec_revision = wsi->ietf_spec_revision;
 
+	client_handshake_generation_is_for_mux_child = 1;
 	p = libwebsockets_generate_client_handshake(context, wsi_child,
 								 delta_headers);
+	client_handshake_generation_is_for_mux_child = 0;
 	delta_headers_len = p - delta_headers;
 
 	subcommand_length = lws_mux_subcommand_header(
@@ -122,7 +125,7 @@ static int lws_ext_x_google_mux__send_addchannel(
 
 	/* send the request to the server */
 
-	n = lws_issue_raw(wsi, &send_buf[LWS_SEND_BUFFER_PRE_PADDING],
+	n = lws_issue_raw_ext_access(wsi, &send_buf[LWS_SEND_BUFFER_PRE_PADDING],
 				   pb - &send_buf[LWS_SEND_BUFFER_PRE_PADDING]);
 
 	parent_conn->defeat_mux_opcode_wrapping = 0;
@@ -443,6 +446,10 @@ bail2:
 		wsi->xor_mask = xor_no_mask;
 		child_conn = lws_get_extension_user_matching_ext(wsi_child,
 								      this_ext);
+		if (!child_conn) {
+			fprintf(stderr, "wsi_child %p has no child conn!", (void *)wsi_child);
+			break;
+		}
 		child_conn->wsi_parent = wsi;
 		conn->sticky_mux_used = 1;
 		child_conn->subchannel = conn->block_subchannel;
@@ -526,7 +533,7 @@ bail2:
 		 * afterwards
 		 */
 		if (conn->block_subchannel - MUX_REAL_CHILD_INDEX_OFFSET >= conn->highest_child_subchannel) {
-			fprintf(stderr, "Illegal subchannel\n");
+			fprintf(stderr, "Illegal subchannel %d\n", conn->block_subchannel);
 			return -1;
 		}
 
@@ -541,6 +548,11 @@ bail2:
 		} else
 			wsi_child = conn->wsi_children[conn->block_subchannel - MUX_REAL_CHILD_INDEX_OFFSET];
 
+		if (!wsi_child) {
+			fprintf(stderr, "Bad subchannel %d\n", conn->block_subchannel);
+			return -1;
+		}
+
 		switch (wsi_child->mode) {
 
 		/* client receives something */
@@ -1078,7 +1090,7 @@ handle_additions:
 		 * recurse to allow nesting
 		 */
 
-		lws_issue_raw(wsi_parent, basepin, (pin - basepin) + len);
+		lws_issue_raw_ext_access(wsi_parent, basepin, (pin - basepin) + len);
 
 		return 1; /* handled */
 
@@ -1144,7 +1156,7 @@ handle_additions:
 		memcpy(pb, in, len);
 		pb += len;
 
-		lws_issue_raw(wsi->extension_handles, &send_buf[LWS_SEND_BUFFER_PRE_PADDING],
+		lws_issue_raw_ext_access(wsi->extension_handles, &send_buf[LWS_SEND_BUFFER_PRE_PADDING],
 					   pb - &send_buf[LWS_SEND_BUFFER_PRE_PADDING]);
 
 
@@ -1190,6 +1202,18 @@ handle_additions:
 		}
 		break;
 
+	case LWS_EXT_CALLBACK_CHECK_OK_TO_PROPOSE_EXTENSION:
+
+		/* disallow deflate-stream if we are a mux child connection */
+
+		if (strcmp(in, "deflate-stream") == 0 &&
+				 client_handshake_generation_is_for_mux_child) {
+
+			fprintf(stderr, "mux banned deflate-stream on child connection\n");
+			return 1; /* disallow */
+		}
+		break;
+
 	default:
 		break;
 	}
diff --git a/lib/libwebsockets.c b/lib/libwebsockets.c
index 0021eb4..90e1fbe 100644
--- a/lib/libwebsockets.c
+++ b/lib/libwebsockets.c
@@ -784,6 +784,7 @@ libwebsockets_generate_client_handshake(struct libwebsocket_context *context,
 	char *p = pkt;
 	int n;
 	struct libwebsocket_extension *ext;
+	struct libwebsocket_extension *ext1;
 	int ext_count = 0;
 	unsigned char buf[LWS_SEND_BUFFER_PRE_PADDING + 1 + MAX_BROADCAST_PAYLOAD +
 						  LWS_SEND_BUFFER_POST_PADDING];
@@ -957,6 +958,24 @@ libwebsockets_generate_client_handshake(struct libwebsocket_context *context,
 	while (ext && ext->callback) {
 
 		n = 0;
+		ext1 = context->extensions;
+		while (ext1 && ext1->callback) {
+
+			n |= ext1->callback(context, ext1, wsi,
+				LWS_EXT_CALLBACK_CHECK_OK_TO_PROPOSE_EXTENSION,
+					NULL, (char *)ext->name, 0);
+
+			ext1++;
+		}
+
+		if (n) {
+
+			/* an extension vetos us */
+			fprintf(stderr, "ext %s vetoed\n", (char *)ext->name);
+			ext++;
+			continue;
+		}
+
 		n = context->protocols[0].callback(context, wsi,
 			LWS_CALLBACK_CLIENT_CONFIRM_EXTENSION_SUPPORTED,
 				wsi->user_space, (char *)ext->name, 0);
@@ -1010,6 +1029,8 @@ libwebsockets_generate_client_handshake(struct libwebsocket_context *context,
 
 issue_hdr:
 
+	puts(pkt);
+
 	/* done with these now */
 
 	free(wsi->c_path);
diff --git a/lib/libwebsockets.h b/lib/libwebsockets.h
index 49bf648..2ab918d 100644
--- a/lib/libwebsockets.h
+++ b/lib/libwebsockets.h
@@ -83,6 +83,7 @@ enum libwebsocket_extension_callback_reasons {
 	LWS_EXT_CALLBACK_CONSTRUCT,
 	LWS_EXT_CALLBACK_CLIENT_CONSTRUCT,
 	LWS_EXT_CALLBACK_CHECK_OK_TO_REALLY_CLOSE,
+	LWS_EXT_CALLBACK_CHECK_OK_TO_PROPOSE_EXTENSION,
 	LWS_EXT_CALLBACK_DESTROY,
 	LWS_EXT_CALLBACK_DESTROY_ANY_WSI_CLOSING,
 	LWS_EXT_CALLBACK_ANY_WSI_ESTABLISHED,
diff --git a/lib/parsers.c b/lib/parsers.c
index 3e3ac19..7ad040e 100644
--- a/lib/parsers.c
+++ b/lib/parsers.c
@@ -1450,6 +1450,87 @@ int lws_issue_raw(struct libwebsocket *wsi, unsigned char *buf, size_t len)
 	return 0;
 }
 
+int
+lws_issue_raw_ext_access(struct libwebsocket *wsi,
+						 unsigned char *buf, size_t len)
+{
+	int ret;
+	struct lws_tokens eff_buf;
+	int m;
+	int n;
+
+	eff_buf.token = (char *)buf;
+	eff_buf.token_len = len;
+
+	/*
+	 * while we have original buf to spill ourselves, or extensions report
+	 * more in their pipeline
+	 */
+
+	ret = 1;
+	while (ret == 1) {
+
+		/* default to nobody has more to spill */
+
+		ret = 0;
+
+		/* show every extension the new incoming data */
+
+		for (n = 0; n < wsi->count_active_extensions; n++) {
+			m = wsi->active_extensions[n]->callback(
+					wsi->protocol->owning_server,
+					wsi->active_extensions[n], wsi,
+					LWS_EXT_CALLBACK_PACKET_TX_PRESEND,
+				   wsi->active_extensions_user[n], &eff_buf, 0);
+			if (m < 0) {
+				fprintf(stderr, "Extension reports fatal error\n");
+				return -1;
+			}
+			if (m)
+				/*
+				 * at least one extension told us he has more
+				 * to spill, so we will go around again after
+				 */
+				ret = 1;
+		}
+
+		/* assuming they left us something to send, send it */
+
+		if (eff_buf.token_len)
+			if (lws_issue_raw(wsi, (unsigned char *)eff_buf.token,
+							     eff_buf.token_len))
+				return -1;
+
+		/* we used up what we had */
+
+		eff_buf.token = NULL;
+		eff_buf.token_len = 0;
+
+		/*
+		 * Did that leave the pipe choked?
+		 */
+
+		if (!lws_send_pipe_choked(wsi))
+			/* no we could add more */
+			continue;
+
+		fprintf(stderr, "choked\n");
+
+		/*
+		 * Yes, he's choked.  Don't spill the rest now get a callback
+		 * when he is ready to send and take care of it there
+		 */
+		libwebsocket_callback_on_writable(
+					     wsi->protocol->owning_server, wsi);
+		wsi->extension_data_pending = 1;
+		ret = 0;
+	}
+
+	debug("written %d bytes to client\n", eff_buf.token_len);
+
+	return 0;
+}
+
 /**
  * libwebsocket_write() - Apply protocol then write data to client
  * @wsi:	Websocket instance (available from user callback)
@@ -1479,12 +1560,9 @@ int libwebsocket_write(struct libwebsocket *wsi, unsigned char *buf,
 			  size_t len, enum libwebsocket_write_protocol protocol)
 {
 	int n;
-	int m;
 	int pre = 0;
 	int post = 0;
 	int shift = 7;
-	struct lws_tokens eff_buf;
-	int ret;
 	int masked7 = wsi->mode == LWS_CONNMODE_WS_CLIENT && wsi->xor_mask != xor_no_mask;
 	unsigned char *dropmask = NULL;
 	unsigned char is_masked_bit = 0;
@@ -1780,76 +1858,7 @@ send_raw:
 	 * callback returns 1 in case it wants to spill more buffers
 	 */
 
-	eff_buf.token = (char *)buf - pre;
-	eff_buf.token_len = len + pre + post;
-
-	/*
-	 * while we have original buf to spill ourselves, or extensions report
-	 * more in their pipeline
-	 */
-
-	ret = 1;
-	while (ret == 1) {
-
-		/* default to nobody has more to spill */
-
-		ret = 0;
-
-		/* show every extension the new incoming data */
-
-		for (n = 0; n < wsi->count_active_extensions; n++) {
-			m = wsi->active_extensions[n]->callback(
-					wsi->protocol->owning_server,
-					wsi->active_extensions[n], wsi,
-					LWS_EXT_CALLBACK_PACKET_TX_PRESEND,
-				   wsi->active_extensions_user[n], &eff_buf, 0);
-			if (m < 0) {
-				fprintf(stderr, "Extension reports fatal error\n");
-				return -1;
-			}
-			if (m)
-				/*
-				 * at least one extension told us he has more
-				 * to spill, so we will go around again after
-				 */
-				ret = 1;
-		}
-
-		/* assuming they left us something to send, send it */
-
-		if (eff_buf.token_len)
-			if (lws_issue_raw(wsi, (unsigned char *)eff_buf.token,
-							     eff_buf.token_len))
-				return -1;
-
-		/* we used up what we had */
-
-		eff_buf.token = NULL;
-		eff_buf.token_len = 0;
-
-		/*
-		 * Did that leave the pipe choked?
-		 */
-
-		if (!lws_send_pipe_choked(wsi))
-			/* no we could add more */
-			continue;
-
-		fprintf(stderr, "choked\n");
-
-		/*
-		 * Yes, he's choked.  Don't spill the rest now get a callback
-		 * when he is ready to send and take care of it there
-		 */
-		libwebsocket_callback_on_writable(
-					     wsi->protocol->owning_server, wsi);
-		wsi->extension_data_pending = 1;
-		ret = 0;
-	}
-
-	debug("written %d bytes to client\n", eff_buf.token_len);
-
-	return 0;
+	return lws_issue_raw_ext_access(wsi, buf - pre, len + pre + post);
 }
 
 
diff --git a/lib/private-libwebsockets.h b/lib/private-libwebsockets.h
index bf2865d..e706bf5 100644
--- a/lib/private-libwebsockets.h
+++ b/lib/private-libwebsockets.h
@@ -415,6 +415,10 @@ lws_client_interpret_server_handshake(struct libwebsocket_context *context,
 extern int
 libwebsocket_rx_sm(struct libwebsocket *wsi, unsigned char c);
 
+extern int
+lws_issue_raw_ext_access(struct libwebsocket *wsi,
+						unsigned char *buf, size_t len);
+
 #ifndef LWS_OPENSSL_SUPPORT
 
 unsigned char *