lib/extension-deflate-frame.c

#include "private-libwebsockets.h"
#include "extension-deflate-frame.h"
#include <stdio.h>
#include <string.h>
#include <assert.h>

#define LWS_ZLIB_WINDOW_BITS 15
#define LWS_ZLIB_MEMLEVEL 8

int lws_extension_callback_deflate_frame(
		struct libwebsocket_context *context,
		struct libwebsocket_extension *ext,
		struct libwebsocket *wsi,
		enum libwebsocket_extension_callback_reasons reason,
		void *user, void *in, size_t len)
{
	struct lws_ext_deflate_frame_conn *conn =
				     (struct lws_ext_deflate_frame_conn *)user;
	struct lws_tokens *eff_buf = (struct lws_tokens *)in;
	size_t current_payload, remaining_payload, total_payload;
	int n;
	size_t len_so_far;

	switch (reason) {

	/*
	 * for deflate-frame, both client and server sides act the same
	 */

	case LWS_EXT_CALLBACK_CLIENT_CONSTRUCT:
	case LWS_EXT_CALLBACK_CONSTRUCT:
		conn->zs_in.zalloc = conn->zs_out.zalloc = Z_NULL;
		conn->zs_in.zfree = conn->zs_out.zfree = Z_NULL;
		conn->zs_in.opaque = conn->zs_out.opaque = Z_NULL;
		n = inflateInit2(&conn->zs_in, -LWS_ZLIB_WINDOW_BITS);
		if (n != Z_OK) {
			lwsl_ext("deflateInit returned %d\n", n);
			return 1;
		}
		n = deflateInit2(&conn->zs_out,
				 (context->listen_port ?
					DEFLATE_FRAME_COMPRESSION_LEVEL_SERVER :
					DEFLATE_FRAME_COMPRESSION_LEVEL_CLIENT),
				 Z_DEFLATED,
				 -LWS_ZLIB_WINDOW_BITS, LWS_ZLIB_MEMLEVEL,
				 Z_DEFAULT_STRATEGY);
		if (n != Z_OK) {
			lwsl_ext("deflateInit2 returned %d\n", n);
			return 1;
		}
		conn->buf_pre_used = 0;
		conn->buf_pre_length = 0;
		conn->buf_in_length = sizeof(conn->buf_in);
		conn->buf_out_length = sizeof(conn->buf_out);
		conn->compressed_out = 0;
		conn->buf_pre = NULL;
		conn->buf_in = lws_malloc(LWS_SEND_BUFFER_PRE_PADDING +
					  conn->buf_in_length +
					  LWS_SEND_BUFFER_POST_PADDING);
		if (!conn->buf_in)
			goto bail;
		conn->buf_out = lws_malloc(LWS_SEND_BUFFER_PRE_PADDING +
					   conn->buf_out_length +
					   LWS_SEND_BUFFER_POST_PADDING);
		if (!conn->buf_out)
			goto bail;
		lwsl_ext("zlibs constructed\n");
		break;
bail:
		lwsl_err("Out of mem\n");
		(void)inflateEnd(&conn->zs_in);
		(void)deflateEnd(&conn->zs_out);
		return -1;

	case LWS_EXT_CALLBACK_DESTROY:
		lws_free(conn->buf_pre);
		lws_free(conn->buf_in);
		lws_free(conn->buf_out);
		conn->buf_pre_used = 0;
		conn->buf_pre_length = 0;
		conn->buf_in_length = 0;
		conn->buf_out_length = 0;
		conn->compressed_out = 0;
		(void)inflateEnd(&conn->zs_in);
		(void)deflateEnd(&conn->zs_out);
		lwsl_ext("zlibs destructed\n");
		break;

	case LWS_EXT_CALLBACK_PAYLOAD_RX:
		if (!(wsi->u.ws.rsv & 0x40))
			return 0;

		/*
		 * inflate the incoming payload
		 */
		current_payload = eff_buf->token_len;

		remaining_payload = wsi->u.ws.rx_packet_length;
		if (remaining_payload) {
			total_payload = conn->buf_pre_used +
					current_payload +
					remaining_payload;

			if (conn->buf_pre_length < total_payload) {
				conn->buf_pre_length = total_payload;
				lws_free(conn->buf_pre);
				conn->buf_pre = lws_malloc(total_payload + 4);
				if (!conn->buf_pre) {
					lwsl_err("Out of memory\n");
					return -1;
				}
			}

			memcpy(conn->buf_pre + conn->buf_pre_used,
					      eff_buf->token, current_payload);
			conn->buf_pre_used += current_payload;

			eff_buf->token = NULL;
			eff_buf->token_len = 0;

			return 0;
		}
		if (conn->buf_pre_used) {
			total_payload = conn->buf_pre_used +
					current_payload;

			memcpy(conn->buf_pre + conn->buf_pre_used,
					      eff_buf->token, current_payload);
			conn->buf_pre_used = 0;

			conn->zs_in.next_in = conn->buf_pre;
		} else {
			total_payload = current_payload;

			conn->zs_in.next_in = (unsigned char *)eff_buf->token;
		}

		conn->zs_in.next_in[total_payload + 0] = 0;
		conn->zs_in.next_in[total_payload + 1] = 0;
		conn->zs_in.next_in[total_payload + 2] = 0xff;
		conn->zs_in.next_in[total_payload + 3] = 0xff;

		conn->zs_in.avail_in = total_payload + 4;

		conn->zs_in.next_out =
				conn->buf_in + LWS_SEND_BUFFER_PRE_PADDING;
		conn->zs_in.avail_out = conn->buf_in_length;

		while (1) {
			n = inflate(&conn->zs_in, Z_SYNC_FLUSH);
			switch (n) {
			case Z_NEED_DICT:
			case Z_STREAM_ERROR:
			case Z_DATA_ERROR:
			case Z_MEM_ERROR:
				/*
				 * screwed.. close the connection...
				 * we will get a destroy callback to take care
				 * of closing nicely
				 */
				lwsl_info("zlib error inflate %d: %s\n",
							   n, conn->zs_in.msg);
				return -1;
			}

			if (conn->zs_in.avail_out)
				break;

			len_so_far = conn->zs_in.next_out -
				(conn->buf_in + LWS_SEND_BUFFER_PRE_PADDING);

			conn->buf_in_length *= 2;
			if (conn->buf_in_length > LWS_MAX_ZLIB_CONN_BUFFER) {
				lwsl_ext("zlib in buffer hit limit %u\n",
						LWS_MAX_ZLIB_CONN_BUFFER);
				return -1;
			}
			conn->buf_in = lws_realloc(conn->buf_in,
						   LWS_SEND_BUFFER_PRE_PADDING +
						   conn->buf_in_length +
						   LWS_SEND_BUFFER_POST_PADDING);
			if (!conn->buf_in) {
				lwsl_err("Out of memory\n");
				return -1;
			}
			lwsl_debug(
				"deflate-frame ext RX did realloc to %ld\n",
					conn->buf_in_length);
			conn->zs_in.next_out = conn->buf_in +
				LWS_SEND_BUFFER_PRE_PADDING + len_so_far;
			conn->zs_in.avail_out =
					conn->buf_in_length - len_so_far;
		}

		/* rewrite the buffer pointers and length */
		eff_buf->token =
			(char *)(conn->buf_in + LWS_SEND_BUFFER_PRE_PADDING);
		eff_buf->token_len = (int)(conn->zs_in.next_out -
				 (conn->buf_in + LWS_SEND_BUFFER_PRE_PADDING));

		return 0;

	case LWS_EXT_CALLBACK_PAYLOAD_TX:
		/*
		 * deflate the outgoing payload
		 */
		current_payload = eff_buf->token_len;

		conn->zs_out.next_in = (unsigned char *)eff_buf->token;
		conn->zs_out.avail_in = current_payload;

		conn->zs_out.next_out =
				conn->buf_out + LWS_SEND_BUFFER_PRE_PADDING;
		conn->zs_out.avail_out = conn->buf_out_length;

		while (1) {
			n = deflate(&conn->zs_out, Z_SYNC_FLUSH);
			if (n == Z_STREAM_ERROR) {
				/*
				 * screwed.. close the connection... we will
				 * get a destroy callback to take care of
				 * closing nicely
				 */
				lwsl_ext("zlib error deflate\n");

				return -1;
			}

			if (conn->zs_out.avail_out)
				break;

			len_so_far = (conn->zs_out.next_out -
					(conn->buf_out +
						 LWS_SEND_BUFFER_PRE_PADDING));
			conn->buf_out_length *= 2;
			if (conn->buf_out_length > LWS_MAX_ZLIB_CONN_BUFFER) {
				lwsl_ext("zlib out hit limit %u\n",
						LWS_MAX_ZLIB_CONN_BUFFER);
				return -1;
			}
			conn->buf_out = lws_realloc(conn->buf_out,
						    LWS_SEND_BUFFER_PRE_PADDING +
						    conn->buf_out_length +
						    LWS_SEND_BUFFER_POST_PADDING);
			if (!conn->buf_out) {
				lwsl_err("Out of memory\n");
				return -1;
			}
			lwsl_debug(
				"deflate-frame ext TX did realloc to %ld\n",
					conn->buf_in_length);

			conn->zs_out.next_out = (conn->buf_out +
				     LWS_SEND_BUFFER_PRE_PADDING + len_so_far);
			conn->zs_out.avail_out =
					   (conn->buf_out_length - len_so_far);
		}

		conn->compressed_out = 1;

		/* rewrite the buffer pointers and length */
		eff_buf->token = (char *)(conn->buf_out +
						LWS_SEND_BUFFER_PRE_PADDING);
		eff_buf->token_len = (int)(conn->zs_out.next_out -
			    (conn->buf_out + LWS_SEND_BUFFER_PRE_PADDING)) - 4;

		return 0;

	case LWS_EXT_CALLBACK_PACKET_TX_PRESEND:
		if (conn->compressed_out) {
			conn->compressed_out = 0;
			*((unsigned char *)eff_buf->token) |= 0x40;
		}
		break;

	case LWS_EXT_CALLBACK_CHECK_OK_TO_PROPOSE_EXTENSION:
		/* Avoid x-webkit-deflate-frame extension on client */
		if (!strcmp((char *)in, "x-webkit-deflate-frame"))
			return 1;
		break;

	default:
		break;
	}

	return 0;
}