lib/server.c

/*
 * libwebsockets - small server side websockets and web server implementation
 *
 * Copyright (C) 2010-2015 Andy Green <andy@warmcat.com>
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation:
 *  version 2.1 of the License.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 *  MA  02110-1301  USA
 */


#include "private-libwebsockets.h"

int lws_context_init_server(struct lws_context_creation_info *info,
			    struct lws_context *context)
{
	lws_sockfd_type sockfd;
#if LWS_POSIX
	int n;
	struct sockaddr_in sin;
	socklen_t len = sizeof(sin);
#ifdef LWS_USE_IPV6
	struct sockaddr_in6 serv_addr6;
#endif
	struct sockaddr_in serv_addr4;
	struct sockaddr *v;
	int opt = 1;
#endif
	struct lws *wsi;

	/* set up our external listening socket we serve on */

	if (info->port == CONTEXT_PORT_NO_LISTEN)
		return 0;

#if LWS_POSIX
#ifdef LWS_USE_IPV6
	if (LWS_IPV6_ENABLED(context))
		sockfd = socket(AF_INET6, SOCK_STREAM, 0);
	else
#endif
		sockfd = socket(AF_INET, SOCK_STREAM, 0);
		
	if (sockfd == -1) {
#else
	sockfd = mbed3_create_tcp_stream_socket();
	if (!lws_sockfd_valid(sockfd)) {
#endif

		lwsl_err("ERROR opening socket\n");
		return 1;
	}

#if LWS_POSIX
	/*
	 * allow us to restart even if old sockets in TIME_WAIT
	 */
	if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR,
				      (const void *)&opt, sizeof(opt)) < 0) {
		compatible_close(sockfd);
		return 1;
	}
#endif
	lws_plat_set_socket_options(context, sockfd);

#if LWS_POSIX
#ifdef LWS_USE_IPV6
	if (LWS_IPV6_ENABLED(context)) {
		v = (struct sockaddr *)&serv_addr6;
		n = sizeof(struct sockaddr_in6);
		bzero((char *) &serv_addr6, sizeof(serv_addr6));
		serv_addr6.sin6_addr = in6addr_any;
		serv_addr6.sin6_family = AF_INET6;
		serv_addr6.sin6_port = htons(info->port);
	} else
#endif
	{
		v = (struct sockaddr *)&serv_addr4;
		n = sizeof(serv_addr4);
		bzero((char *) &serv_addr4, sizeof(serv_addr4));
		serv_addr4.sin_addr.s_addr = INADDR_ANY;
		serv_addr4.sin_family = AF_INET;

		if (info->iface) {
			if (interface_to_sa(context, info->iface,
				   (struct sockaddr_in *)v, n) < 0) {
				lwsl_err("Unable to find interface %s\n",
							info->iface);
				compatible_close(sockfd);
				return 1;
			}
		}

		serv_addr4.sin_port = htons(info->port);
	} /* ipv4 */

	n = bind(sockfd, v, n);
	if (n < 0) {
		lwsl_err("ERROR on binding to port %d (%d %d)\n",
					      info->port, n, LWS_ERRNO);
		compatible_close(sockfd);
		return 1;
	}

	if (getsockname(sockfd, (struct sockaddr *)&sin, &len) == -1)
		lwsl_warn("getsockname: %s\n", strerror(LWS_ERRNO));
	else
		info->port = ntohs(sin.sin_port);
#endif

	context->listen_port = info->port;

	wsi = lws_zalloc(sizeof(struct lws));
	if (wsi == NULL) {
		lwsl_err("Out of mem\n");
		compatible_close(sockfd);
		return 1;
	}
	wsi->sock = sockfd;
	wsi->mode = LWS_CONNMODE_SERVER_LISTENER;
	wsi->protocol = context->protocols;

	if (insert_wsi_socket_into_fds(context, wsi)) {
		compatible_close(sockfd);
		return 1;
	}

	context->listen_service_modulo = LWS_LISTEN_SERVICE_MODULO;
	context->listen_service_count = 0;
	context->listen_service_fd = sockfd;

#if LWS_POSIX
	listen(sockfd, LWS_SOMAXCONN);
#else
	mbed3_tcp_stream_bind(sockfd, info->port, wsi);
#endif
	lwsl_notice(" Listening on port %d\n", info->port);

	return 0;
}

int
_lws_rx_flow_control(struct lws *wsi)
{
	struct lws_context *context = wsi->protocol->owning_server;

	/* there is no pending change */
	if (!(wsi->rxflow_change_to & LWS_RXFLOW_PENDING_CHANGE))
		return 0;

	/* stuff is still buffered, not ready to really accept new input */
	if (wsi->rxflow_buffer) {
		/* get ourselves called back to deal with stashed buffer */
		lws_callback_on_writable(context, wsi);
		return 0;
	}

	/* pending is cleared, we can change rxflow state */

	wsi->rxflow_change_to &= ~LWS_RXFLOW_PENDING_CHANGE;

	lwsl_info("rxflow: wsi %p change_to %d\n", wsi,
			      wsi->rxflow_change_to & LWS_RXFLOW_ALLOW);

	/* adjust the pollfd for this wsi */

	if (wsi->rxflow_change_to & LWS_RXFLOW_ALLOW) {
		if (lws_change_pollfd(wsi, 0, LWS_POLLIN)) {
			lwsl_info("%s: fail\n", __func__);
			return -1;
		}
	} else
		if (lws_change_pollfd(wsi, LWS_POLLIN, 0))
			return -1;

	return 0;
}

int lws_http_action(struct lws_context *context,
		    struct lws *wsi)
{
	char *uri_ptr = NULL;
	int uri_len = 0;
	enum http_version request_version;
	enum http_connection_type connection_type;
	int http_version_len;
	char content_length_str[32];
	char http_version_str[10];
	char http_conn_str[20];
	unsigned int n, count = 0;
	static const unsigned char methods[] = {
		WSI_TOKEN_GET_URI,
		WSI_TOKEN_POST_URI,
		WSI_TOKEN_OPTIONS_URI,
		WSI_TOKEN_PUT_URI,
		WSI_TOKEN_PATCH_URI,
		WSI_TOKEN_DELETE_URI,
#ifdef LWS_USE_HTTP2
		WSI_TOKEN_HTTP_COLON_PATH,
#endif
	};
#ifdef _DEBUG
	static const char * const method_names[] = {
		"GET", "POST", "OPTIONS", "PUT", "PATCH", "DELETE",
#ifdef LWS_USE_HTTP2
		":path",
#endif
	};
#endif
	
	/* it's not websocket.... shall we accept it as http? */

	for (n = 0; n < ARRAY_SIZE(methods); n++)
		if (lws_hdr_total_length(wsi, methods[n]))
			count++;
	if (!count) {
		lwsl_warn("Missing URI in HTTP request\n");
		goto bail_nuke_ah;
	}

	if (count != 1) {
		lwsl_warn("multiple methods?\n");
		goto bail_nuke_ah;
	}

	if (lws_ensure_user_space(wsi))
		goto bail_nuke_ah;

	for (n = 0; n < ARRAY_SIZE(methods); n++)
		if (lws_hdr_total_length(wsi, methods[n])) {
			uri_ptr = lws_hdr_simple_ptr(wsi, methods[n]);
			uri_len = lws_hdr_total_length(wsi, methods[n]);
			lwsl_info("Method: %s request for '%s'\n",
				  	method_names[n], uri_ptr);
			break;
		}

	/* HTTP header had a content length? */

	wsi->u.http.content_length = 0;
	if (lws_hdr_total_length(wsi, WSI_TOKEN_POST_URI) ||
		lws_hdr_total_length(wsi, WSI_TOKEN_PATCH_URI) ||
		lws_hdr_total_length(wsi, WSI_TOKEN_PUT_URI))
		wsi->u.http.content_length = 100 * 1024 * 1024;

	if (lws_hdr_total_length(wsi, WSI_TOKEN_HTTP_CONTENT_LENGTH)) {
		lws_hdr_copy(wsi, content_length_str,
				sizeof(content_length_str) - 1,
						WSI_TOKEN_HTTP_CONTENT_LENGTH);
		wsi->u.http.content_length = atoi(content_length_str);
	}

	/* http_version? Default to 1.0, override with token: */
	request_version = HTTP_VERSION_1_0;

	/* Works for single digit HTTP versions. : */
	http_version_len = lws_hdr_total_length(wsi, WSI_TOKEN_HTTP);
	if (http_version_len > 7) {
		lws_hdr_copy(wsi, http_version_str,
				sizeof(http_version_str) - 1, WSI_TOKEN_HTTP);
		if (http_version_str[5] == '1' && http_version_str[7] == '1')
			request_version = HTTP_VERSION_1_1;
	}
	wsi->u.http.request_version = request_version;

	/* HTTP/1.1 defaults to "keep-alive", 1.0 to "close" */
	if (request_version == HTTP_VERSION_1_1)
		connection_type = HTTP_CONNECTION_KEEP_ALIVE;
	else
		connection_type = HTTP_CONNECTION_CLOSE;

	/* Override default if http "Connection:" header: */
	if (lws_hdr_total_length(wsi, WSI_TOKEN_CONNECTION)) {
		lws_hdr_copy(wsi, http_conn_str, sizeof(http_conn_str) - 1,
			     WSI_TOKEN_CONNECTION);
		http_conn_str[sizeof(http_conn_str) - 1] = '\0';
		if (!strcasecmp(http_conn_str, "keep-alive"))
			connection_type = HTTP_CONNECTION_KEEP_ALIVE;
		else
			if (!strcasecmp(http_conn_str, "close"))
				connection_type = HTTP_CONNECTION_CLOSE;
	}
	wsi->u.http.connection_type = connection_type;

	n = 0;
	if (wsi->protocol->callback)
		n = wsi->protocol->callback(context, wsi,
					LWS_CALLBACK_FILTER_HTTP_CONNECTION,
					     wsi->user_space, uri_ptr, uri_len);

	if (!n) {
		/*
		 * if there is content supposed to be coming,
		 * put a timeout on it having arrived
		 */
		lws_set_timeout(wsi, PENDING_TIMEOUT_HTTP_CONTENT,
							      AWAITING_TIMEOUT);

		if (wsi->protocol->callback)
			n = wsi->protocol->callback(context, wsi,
			    LWS_CALLBACK_HTTP,
			    wsi->user_space, uri_ptr, uri_len);
	}

	/* now drop the header info we kept a pointer to */
	lws_free2(wsi->u.http.ah);

	if (n) {
		lwsl_info("LWS_CALLBACK_HTTP closing\n");
		return 1; /* struct ah ptr already nuked */		}

	/* 
	 * If we're not issuing a file, check for content_length or
	 * HTTP keep-alive. No keep-alive header allocation for
	 * ISSUING_FILE, as this uses HTTP/1.0. 
	 * 
	 * In any case, return 0 and let lws_read decide how to
	 * proceed based on state
	 */
	if (wsi->state != WSI_STATE_HTTP_ISSUING_FILE)
		/* Prepare to read body if we have a content length: */
		if (wsi->u.http.content_length > 0)
			wsi->state = WSI_STATE_HTTP_BODY;

	return 0;

bail_nuke_ah:
	/* drop the header info */
	lws_free2(wsi->u.hdr.ah);

	return 1;
}


int lws_handshake_server(struct lws_context *context,
		struct lws *wsi, unsigned char **buf, size_t len)
{
	struct allocated_headers *ah;
	int protocol_len;
	char protocol_list[128];
	char protocol_name[32];
	char *p;
	int n, hit;

	/* LWS_CONNMODE_WS_SERVING */

	while (len--) {
		if (lws_parse(context, wsi, *(*buf)++)) {
			lwsl_info("lws_parse failed\n");
			goto bail_nuke_ah;
		}

		if (wsi->u.hdr.parser_state != WSI_PARSING_COMPLETE)
			continue;

		lwsl_parser("lws_parse sees parsing complete\n");

		wsi->mode = LWS_CONNMODE_PRE_WS_SERVING_ACCEPT;
		lws_set_timeout(wsi, NO_PENDING_TIMEOUT, 0);

		/* is this websocket protocol or normal http 1.0? */

		if (!lws_hdr_total_length(wsi, WSI_TOKEN_UPGRADE) ||
			     !lws_hdr_total_length(wsi, WSI_TOKEN_CONNECTION)) {
			
			ah = wsi->u.hdr.ah;
			
			lws_union_transition(wsi, LWS_CONNMODE_HTTP_SERVING_ACCEPTED);
			wsi->state = WSI_STATE_HTTP;
			wsi->u.http.fd = LWS_INVALID_FILE;

			/* expose it at the same offset as u.hdr */
			wsi->u.http.ah = ah;
			
			n = lws_http_action(context, wsi);

			return n;
		}

		if (!strcasecmp(lws_hdr_simple_ptr(wsi, WSI_TOKEN_UPGRADE),
								"websocket"))
			goto upgrade_ws;
#ifdef LWS_USE_HTTP2
		if (!strcasecmp(lws_hdr_simple_ptr(wsi, WSI_TOKEN_UPGRADE),
								"h2c-14"))
			goto upgrade_h2c;
#endif
		/* dunno what he wanted to upgrade to */
		goto bail_nuke_ah;

#ifdef LWS_USE_HTTP2
upgrade_h2c:
		if (!lws_hdr_total_length(wsi, WSI_TOKEN_HTTP2_SETTINGS)) {
			lwsl_err("missing http2_settings\n");
			goto bail_nuke_ah;
		}

		lwsl_err("h2c upgrade...\n");

		p = lws_hdr_simple_ptr(wsi, WSI_TOKEN_HTTP2_SETTINGS);
		/* convert the peer's HTTP-Settings */
		n = lws_b64_decode_string(p, protocol_list, sizeof(protocol_list));
		if (n < 0) {
			lwsl_parser("HTTP2_SETTINGS too long\n");
			return 1;
		}

		/* adopt the header info */

		ah = wsi->u.hdr.ah;

		lws_union_transition(wsi, LWS_CONNMODE_HTTP2_SERVING);
		
		/* http2 union member has http union struct at start */
		wsi->u.http.ah = ah;
		
		lws_http2_init(&wsi->u.http2.peer_settings);
		lws_http2_init(&wsi->u.http2.my_settings);
		
		/* HTTP2 union */
		
		lws_http2_interpret_settings_payload(&wsi->u.http2.peer_settings, (unsigned char *)protocol_list, n);

		strcpy(protocol_list,
		       "HTTP/1.1 101 Switching Protocols\x0d\x0a"
		      "Connection: Upgrade\x0d\x0a"
		      "Upgrade: h2c\x0d\x0a\x0d\x0a");
		n = lws_issue_raw(wsi, (unsigned char *)protocol_list,
					strlen(protocol_list));
		if (n != strlen(protocol_list)) {
			lwsl_debug("http2 switch: ERROR writing to socket\n");
			return 1;
		}
		
		wsi->state = WSI_STATE_HTTP2_AWAIT_CLIENT_PREFACE;
		
		return 0;
#endif

upgrade_ws:
		if (!wsi->protocol)
			lwsl_err("NULL protocol at lws_read\n");

		/*
		 * It's websocket
		 *
		 * Select the first protocol we support from the list
		 * the client sent us.
		 *
		 * Copy it to remove header fragmentation
		 */

		if (lws_hdr_copy(wsi, protocol_list, sizeof(protocol_list) - 1,
				 WSI_TOKEN_PROTOCOL) < 0) {
			lwsl_err("protocol list too long");
			goto bail_nuke_ah;
		}

		protocol_len = lws_hdr_total_length(wsi, WSI_TOKEN_PROTOCOL);
		protocol_list[protocol_len] = '\0';
		p = protocol_list;
		hit = 0;

		while (*p && !hit) {
			unsigned int n = 0;
			while (n < sizeof(protocol_name) - 1 && *p && *p !=',')
				protocol_name[n++] = *p++;
			protocol_name[n] = '\0';
			if (*p)
				p++;

			lwsl_info("checking %s\n", protocol_name);

			n = 0;
			while (wsi->protocol && context->protocols[n].callback) {
				if (!wsi->protocol->name) {
					n++;
					continue;
				}
				if (!strcmp(context->protocols[n].name,
					    protocol_name)) {
					lwsl_info("prot match %d\n", n);
					wsi->protocol = &context->protocols[n];
					hit = 1;
					break;
				}

				n++;
			}
		}

		/* we didn't find a protocol he wanted? */

		if (!hit) {
			if (lws_hdr_simple_ptr(wsi, WSI_TOKEN_PROTOCOL) ==
									 NULL) {
				/*
				 * some clients only have one protocol and
				 * do not sent the protocol list header...
				 * allow it and match to protocol 0
				 */
				lwsl_info("defaulting to prot 0 handler\n");
				wsi->protocol = &context->protocols[0];
			} else {
				lwsl_err("No protocol from list \"%s\" supported\n",
					 protocol_list);
				goto bail_nuke_ah;
			}
		}

		/* allocate wsi->user storage */
		if (lws_ensure_user_space(wsi))
			goto bail_nuke_ah;

		/*
		 * Give the user code a chance to study the request and
		 * have the opportunity to deny it
		 */

		if ((wsi->protocol->callback)(wsi->protocol->owning_server, wsi,
				LWS_CALLBACK_FILTER_PROTOCOL_CONNECTION,
				wsi->user_space,
			      lws_hdr_simple_ptr(wsi, WSI_TOKEN_PROTOCOL), 0)) {
			lwsl_warn("User code denied connection\n");
			goto bail_nuke_ah;
		}


		/*
		 * Perform the handshake according to the protocol version the
		 * client announced
		 */

		switch (wsi->ietf_spec_revision) {
		case 13:
			lwsl_parser("lws_parse calling handshake_04\n");
			if (handshake_0405(context, wsi)) {
				lwsl_info("hs0405 has failed the connection\n");
				goto bail_nuke_ah;
			}
			break;

		default:
			lwsl_warn("Unknown client spec version %d\n",
						       wsi->ietf_spec_revision);
			goto bail_nuke_ah;
		}

		/* drop the header info -- no bail_nuke_ah after this */
		lws_free_header_table(wsi);

		lws_union_transition(wsi, LWS_CONNMODE_WS_SERVING);

		/*
		 * create the frame buffer for this connection according to the
		 * size mentioned in the protocol definition.  If 0 there, use
		 * a big default for compatibility
		 */

		n = wsi->protocol->rx_buffer_size;
		if (!n)
			n = LWS_MAX_SOCKET_IO_BUF;
		n += LWS_SEND_BUFFER_PRE_PADDING + LWS_SEND_BUFFER_POST_PADDING;
		wsi->u.ws.rx_user_buffer = lws_malloc(n);
		if (!wsi->u.ws.rx_user_buffer) {
			lwsl_err("Out of Mem allocating rx buffer %d\n", n);
			return 1;
		}
		lwsl_info("Allocating RX buffer %d\n", n);
#if LWS_POSIX
		if (setsockopt(wsi->sock, SOL_SOCKET, SO_SNDBUF, (const char *)&n, sizeof n)) {
			lwsl_warn("Failed to set SNDBUF to %d", n);
			return 1;
		}
#endif
		lwsl_parser("accepted v%02d connection\n",
						       wsi->ietf_spec_revision);
	} /* while all chars are handled */

	return 0;

bail_nuke_ah:
	/* drop the header info */
	lws_free_header_table(wsi);
	return 1;
}

struct lws *
lws_create_new_server_wsi(struct lws_context *context)
{
	struct lws *new_wsi;

	new_wsi = lws_zalloc(sizeof(struct lws));
	if (new_wsi == NULL) {
		lwsl_err("Out of memory for new connection\n");
		return NULL;
	}

	new_wsi->pending_timeout = NO_PENDING_TIMEOUT;
	new_wsi->rxflow_change_to = LWS_RXFLOW_ALLOW;

	/* intialize the instance struct */

	new_wsi->state = WSI_STATE_HTTP;
	new_wsi->mode = LWS_CONNMODE_HTTP_SERVING;
	new_wsi->hdr_parsing_completed = 0;

#ifdef LWS_OPENSSL_SUPPORT
	new_wsi->use_ssl = LWS_SSL_ENABLED(context);
#endif

	if (lws_allocate_header_table(new_wsi)) {
		lws_free(new_wsi);
		return NULL;
	}

	/*
	 * these can only be set once the protocol is known
	 * we set an unestablished connection's protocol pointer
	 * to the start of the supported list, so it can look
	 * for matching ones during the handshake
	 */
	new_wsi->protocol = context->protocols;
	new_wsi->user_space = NULL;
	new_wsi->ietf_spec_revision = 0;
	new_wsi->sock = LWS_SOCK_INVALID;
	
	/*
	 * outermost create notification for wsi
	 * no user_space because no protocol selection
	 */
	context->protocols[0].callback(context, new_wsi,
			LWS_CALLBACK_WSI_CREATE, NULL, NULL, 0);

	return new_wsi;
}

/**
 * lws_http_transaction_completed() - wait for new http transaction or close
 * @wsi:	websocket connection
 *
 *	Returns 1 if the HTTP connection must close now
 *	Returns 0 and resets connection to wait for new HTTP header /
 *	  transaction if possible
 */

LWS_VISIBLE
int lws_http_transaction_completed(struct lws *wsi)
{
	/* if we can't go back to accept new headers, drop the connection */
	if (wsi->u.http.connection_type != HTTP_CONNECTION_KEEP_ALIVE) {
		lwsl_info("%s: close connection\n", __func__);
		return 1;
	}

	/* otherwise set ourselves up ready to go again */
	wsi->state = WSI_STATE_HTTP;
	wsi->mode = LWS_CONNMODE_HTTP_SERVING;
	wsi->u.http.content_length = 0;

	/* He asked for it to stay alive indefinitely */
	lws_set_timeout(wsi, NO_PENDING_TIMEOUT, 0);

	if (lws_allocate_header_table(wsi))
		return 1;

	/* If we're (re)starting on headers, need other implied init */
	wsi->u.hdr.ues = URIES_IDLE;
	
	lwsl_info("%s: keep-alive await new transaction\n", __func__);
	
	return 0;
}

LWS_VISIBLE
int lws_server_socket_service(struct lws_context *context,
			struct lws *wsi, struct lws_pollfd *pollfd)
{
	struct lws *new_wsi = NULL;
	lws_sockfd_type accept_fd = LWS_SOCK_INVALID;
#if LWS_POSIX
	socklen_t clilen;
	struct sockaddr_in cli_addr;
#endif
	int n;
	int len;

	switch (wsi->mode) {

	case LWS_CONNMODE_HTTP_SERVING:
	case LWS_CONNMODE_HTTP_SERVING_ACCEPTED:
	case LWS_CONNMODE_HTTP2_SERVING:

		/* handle http headers coming in */

		/* pending truncated sends have uber priority */

		if (wsi->truncated_send_len) {
			if (pollfd->revents & LWS_POLLOUT)
				if (lws_issue_raw(wsi, wsi->truncated_send_malloc +
					wsi->truncated_send_offset,
							wsi->truncated_send_len) < 0) {
					lwsl_info("closing from socket service\n");
					return -1;
				}
			/*
			 * we can't afford to allow input processing send
			 * something new, so spin around he event loop until
			 * he doesn't have any partials
			 */
			break;
		}

		/* any incoming data ready? */

		if (pollfd->revents & LWS_POLLIN) {
			len = lws_ssl_capable_read(context, wsi,
					context->service_buffer,
						       sizeof(context->service_buffer));
			lwsl_debug("%s: read %d\r\n", __func__, len);
			switch (len) {
			case 0:
				lwsl_info("lws_server_skt_srv: read 0 len\n");
				/* lwsl_info("   state=%d\n", wsi->state); */
				if (!wsi->hdr_parsing_completed)
					lws_free_header_table(wsi);
				/* fallthru */
			case LWS_SSL_CAPABLE_ERROR:
				lws_close_and_free_session(
						context, wsi,
						LWS_CLOSE_STATUS_NOSTATUS);
				return 0;
			case LWS_SSL_CAPABLE_MORE_SERVICE:
				goto try_pollout;
			}

			/* just ignore incoming if waiting for close */
			if (wsi->state != WSI_STATE_FLUSHING_STORED_SEND_BEFORE_CLOSE) {
			
				/* hm this may want to send (via HTTP callback for example) */
				n = lws_read(context, wsi,
							context->service_buffer, len);
				if (n < 0)
					/* we closed wsi */
					return 0;

				/* hum he may have used up the writability above */
				break;
			}
		}

try_pollout:
		/* this handles POLLOUT for http serving fragments */

		if (!(pollfd->revents & LWS_POLLOUT))
			break;

		/* one shot */
		if (lws_change_pollfd(wsi, LWS_POLLOUT, 0))
			goto fail;
		
		lws_libev_io(context, wsi, LWS_EV_STOP | LWS_EV_WRITE);

		if (wsi->state != WSI_STATE_HTTP_ISSUING_FILE) {
			n = user_callback_handle_rxflow(
					wsi->protocol->callback,
					wsi->protocol->owning_server,
					wsi, LWS_CALLBACK_HTTP_WRITEABLE,
					wsi->user_space,
					NULL,
					0);
			if (n < 0)
				goto fail;
			break;
		}

		/* >0 == completion, <0 == error */
		n = lws_serve_http_file_fragment(context, wsi);
		if (n < 0 || (n > 0 && lws_http_transaction_completed(wsi)))
			goto fail;
		break;

	case LWS_CONNMODE_SERVER_LISTENER:

#if LWS_POSIX
		/* pollin means a client has connected to us then */

		if (!(pollfd->revents & LWS_POLLIN))
			break;

		/* listen socket got an unencrypted connection... */
		
		clilen = sizeof(cli_addr);
		lws_latency_pre(context, wsi);
		accept_fd  = accept(pollfd->fd, (struct sockaddr *)&cli_addr,
								       &clilen);
		lws_latency(context, wsi,
			"unencrypted accept LWS_CONNMODE_SERVER_LISTENER",
						     accept_fd, accept_fd >= 0);
		if (accept_fd < 0) {
			if (LWS_ERRNO == LWS_EAGAIN || LWS_ERRNO == LWS_EWOULDBLOCK) {
				lwsl_debug("accept asks to try again\n");
				break;
			}
			lwsl_warn("ERROR on accept: %s\n", strerror(LWS_ERRNO));
			break;
		}

		lws_plat_set_socket_options(context, accept_fd);
#else
		/* not very beautiful... */
		accept_fd = (lws_sockfd_type)pollfd;
#endif
		/*
		 * look at who we connected to and give user code a chance
		 * to reject based on client IP.  There's no protocol selected
		 * yet so we issue this to protocols[0]
		 */

		if ((context->protocols[0].callback)(context, wsi,
				LWS_CALLBACK_FILTER_NETWORK_CONNECTION,
					   NULL, (void *)(long)accept_fd, 0)) {
			lwsl_debug("Callback denied network connection\n");
			compatible_close(accept_fd);
			break;
		}

		new_wsi = lws_create_new_server_wsi(context);
		if (new_wsi == NULL) {
			compatible_close(accept_fd);
			break;
		}

		new_wsi->sock = accept_fd;

		/* the transport is accepted... give him time to negotiate */
		lws_set_timeout(new_wsi,
			PENDING_TIMEOUT_ESTABLISH_WITH_SERVER,
							AWAITING_TIMEOUT);

#if LWS_POSIX == 0
		mbed3_tcp_stream_accept(accept_fd, new_wsi);
#endif
		
		/*
		 * A new connection was accepted. Give the user a chance to
		 * set properties of the newly created wsi. There's no protocol
		 * selected yet so we issue this to protocols[0]
		 */

		(context->protocols[0].callback)(context, new_wsi,
			LWS_CALLBACK_SERVER_NEW_CLIENT_INSTANTIATED, NULL, NULL, 0);

		lws_libev_accept(context, new_wsi, accept_fd);

		if (!LWS_SSL_ENABLED(context)) {
#if LWS_POSIX
			lwsl_debug("accepted new conn  port %u on fd=%d\n",
					  ntohs(cli_addr.sin_port), accept_fd);
#endif
			if (insert_wsi_socket_into_fds(context, new_wsi))
				goto fail;
		}
		break;

	default:
		break;
	}

	if (lws_server_socket_service_ssl(context, &wsi, new_wsi,
							  accept_fd, pollfd))
		goto fail;

	return 0;

fail:
	lws_close_and_free_session(context, wsi,
						 LWS_CLOSE_STATUS_NOSTATUS);
	return 1;
}

/**
 * lws_serve_http_file() - Send a file back to the client using http
 * @context:		libwebsockets context
 * @wsi:		Websocket instance (available from user callback)
 * @file:		The file to issue over http
 * @content_type:	The http content type, eg, text/html
 * @other_headers:	NULL or pointer to \0-terminated other header string
 *
 *	This function is intended to be called from the callback in response
 *	to http requests from the client.  It allows the callback to issue
 *	local files down the http link in a single step.
 *
 *	Returning <0 indicates error and the wsi should be closed.  Returning
 *	>0 indicates the file was completely sent and
 *	lws_http_transaction_completed() called on the wsi (and close if != 0)
 *	==0 indicates the file transfer is started and needs more service later,
 *	the wsi should be left alone.
 */

LWS_VISIBLE int lws_serve_http_file(
		struct lws_context *context,
			struct lws *wsi, const char *file,
			   const char *content_type, const char *other_headers,
			   int other_headers_len)
{
	unsigned char *response = context->service_buffer + LWS_SEND_BUFFER_PRE_PADDING;
	unsigned char *p = response;
	unsigned char *end = p + sizeof(context->service_buffer) -
					LWS_SEND_BUFFER_PRE_PADDING;
	int ret = 0;

	wsi->u.http.fd = lws_plat_open_file(file, &wsi->u.http.filelen);

	if (wsi->u.http.fd == LWS_INVALID_FILE) {
		lwsl_err("Unable to open '%s'\n", file);
		lws_return_http_status(context, wsi,
						HTTP_STATUS_NOT_FOUND, NULL);
		return -1;
	}

	if (lws_add_http_header_status(context, wsi, 200, &p, end))
		return -1;
	if (lws_add_http_header_by_token(context, wsi, WSI_TOKEN_HTTP_SERVER, (unsigned char *)"libwebsockets", 13, &p, end))
		return -1;
	if (lws_add_http_header_by_token(context, wsi, WSI_TOKEN_HTTP_CONTENT_TYPE, (unsigned char *)content_type, strlen(content_type), &p, end))
		return -1;
	if (lws_add_http_header_content_length(context, wsi, wsi->u.http.filelen, &p, end))
		return -1;

	if (other_headers) {
		if ((end - p) < other_headers_len)
			return -1;
		memcpy(p, other_headers, other_headers_len);
		p += other_headers_len;
	}

	if (lws_finalize_http_header(context, wsi, &p, end))
		return -1;
	
	ret = lws_write(wsi, response,
				   p - response, LWS_WRITE_HTTP_HEADERS);
	if (ret != (p - response)) {
		lwsl_err("_write returned %d from %d\n", ret, (p - response));
		return -1;
	}

	wsi->u.http.filepos = 0;
	wsi->state = WSI_STATE_HTTP_ISSUING_FILE;

	return lws_serve_http_file_fragment(context, wsi);
}


int lws_interpret_incoming_packet(struct lws *wsi,
						 unsigned char *buf, size_t len)
{
	size_t n = 0;
	int m;

#if 0
	lwsl_parser("received %d byte packet\n", (int)len);
	lwsl_hexdump(buf, len);
#endif

	/* let the rx protocol state machine have as much as it needs */

	while (n < len) {
		/*
		 * we were accepting input but now we stopped doing so
		 */
		if (!(wsi->rxflow_change_to & LWS_RXFLOW_ALLOW)) {
			lws_rxflow_cache(wsi, buf, n, len);

			return 1;
		}

		/* account for what we're using in rxflow buffer */
		if (wsi->rxflow_buffer)
			wsi->rxflow_pos++;

		/* process the byte */
		m = lws_rx_sm(wsi, buf[n++]);
		if (m < 0)
			return -1;
	}

	return 0;
}

LWS_VISIBLE void
lws_server_get_canonical_hostname(struct lws_context *context,
				struct lws_context_creation_info *info)
{
	if (info->options & LWS_SERVER_OPTION_SKIP_SERVER_CANONICAL_NAME)
		return;
#if LWS_POSIX
	/* find canonical hostname */
	gethostname((char *)context->canonical_hostname,
				       sizeof(context->canonical_hostname) - 1);

	lwsl_notice(" canonical_hostname = %s\n", context->canonical_hostname);
#else
	(void)context;
#endif
}