1 /*
2 * libwebsockets - small server side websockets and web server implementation
3 *
4 * Copyright (C) 2010 - 2019 Andy Green <andy@warmcat.com>
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a copy
7 * of this software and associated documentation files (the "Software"), to
8 * deal in the Software without restriction, including without limitation the
9 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
10 * sell copies of the Software, and to permit persons to whom the Software is
11 * furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
19 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
21 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
22 * IN THE SOFTWARE.
23 */
24
25 /*! \defgroup sending-data Sending data
26
27 APIs related to writing data on a connection
28 */
29 //@{
30 #if !defined(LWS_SIZEOFPTR)
31 #define LWS_SIZEOFPTR ((int)sizeof (void *))
32 #endif
33
34 #if defined(__x86_64__)
35 #define _LWS_PAD_SIZE 16 /* Intel recommended for best performance */
36 #else
37 #define _LWS_PAD_SIZE LWS_SIZEOFPTR /* Size of a pointer on the target arch */
38 #endif
39 #define _LWS_PAD(n) (((n) % _LWS_PAD_SIZE) ? \
40 ((n) + (_LWS_PAD_SIZE - ((n) % _LWS_PAD_SIZE))) : (n))
41 /* last 2 is for lws-meta */
42 #define LWS_PRE _LWS_PAD(4 + 10 + 2)
43 /* used prior to 1.7 and retained for backward compatibility */
44 #define LWS_SEND_BUFFER_PRE_PADDING LWS_PRE
45 #define LWS_SEND_BUFFER_POST_PADDING 0
46
47 #define LWS_WRITE_RAW LWS_WRITE_HTTP
48
49 /*
50 * NOTE: These public enums are part of the abi. If you want to add one,
51 * add it at where specified so existing users are unaffected.
52 */
53 enum lws_write_protocol {
54 LWS_WRITE_TEXT = 0,
55 /**< Send a ws TEXT message,the pointer must have LWS_PRE valid
56 * memory behind it.
57 *
58 * The receiver expects only valid utf-8 in the payload */
59 LWS_WRITE_BINARY = 1,
60 /**< Send a ws BINARY message, the pointer must have LWS_PRE valid
61 * memory behind it.
62 *
63 * Any sequence of bytes is valid */
64 LWS_WRITE_CONTINUATION = 2,
65 /**< Continue a previous ws message, the pointer must have LWS_PRE valid
66 * memory behind it */
67 LWS_WRITE_HTTP = 3,
68 /**< Send HTTP content */
69
70 /* LWS_WRITE_CLOSE is handled by lws_close_reason() */
71 LWS_WRITE_PING = 5,
72 LWS_WRITE_PONG = 6,
73
74 /* Same as write_http but we know this write ends the transaction */
75 LWS_WRITE_HTTP_FINAL = 7,
76
77 /* HTTP2 */
78
79 LWS_WRITE_HTTP_HEADERS = 8,
80 /**< Send http headers (http2 encodes this payload and LWS_WRITE_HTTP
81 * payload differently, http 1.x links also handle this correctly. so
82 * to be compatible with both in the future,header response part should
83 * be sent using this regardless of http version expected)
84 */
85 LWS_WRITE_HTTP_HEADERS_CONTINUATION = 9,
86 /**< Continuation of http/2 headers
87 */
88
89 /****** add new things just above ---^ ******/
90
91 /* flags */
92
93 LWS_WRITE_BUFLIST = 0x20,
94 /**< Don't actually write it... stick it on the output buflist and
95 * write it as soon as possible. Useful if you learn you have to
96 * write something, have the data to write to hand but the timing is
97 * unrelated as to whether the connection is writable or not, and were
98 * otherwise going to have to allocate a temp buffer and write it
99 * later anyway */
100
101 LWS_WRITE_NO_FIN = 0x40,
102 /**< This part of the message is not the end of the message */
103
104 LWS_WRITE_H2_STREAM_END = 0x80,
105 /**< Flag indicates this packet should go out with STREAM_END if h2
106 * STREAM_END is allowed on DATA or HEADERS.
107 */
108
109 LWS_WRITE_CLIENT_IGNORE_XOR_MASK = 0x80
110 /**< client packet payload goes out on wire unmunged
111 * only useful for security tests since normal servers cannot
112 * decode the content if used */
113 };
114
115 /* used with LWS_CALLBACK_CHILD_WRITE_VIA_PARENT */
116
117 struct lws_write_passthru {
118 struct lws *wsi;
119 unsigned char *buf;
120 size_t len;
121 enum lws_write_protocol wp;
122 };
123
124
125 /**
126 * lws_write() - Apply protocol then write data to client
127 *
128 * \param wsi: Websocket instance (available from user callback)
129 * \param buf: The data to send. For data being sent on a websocket
130 * connection (ie, not default http), this buffer MUST have
131 * LWS_PRE bytes valid BEFORE the pointer.
132 * This is so the protocol header data can be added in-situ.
133 * \param len: Count of the data bytes in the payload starting from buf
134 * \param protocol: Use LWS_WRITE_HTTP to reply to an http connection, and one
135 * of LWS_WRITE_BINARY or LWS_WRITE_TEXT to send appropriate
136 * data on a websockets connection. Remember to allow the extra
137 * bytes before and after buf if LWS_WRITE_BINARY or LWS_WRITE_TEXT
138 * are used.
139 *
140 * This function provides the way to issue data back to the client, for any
141 * role (h1, h2, ws, raw, etc). It can only be called from the WRITEABLE
142 * callback.
143 *
144 * IMPORTANT NOTICE!
145 *
146 * When sending with ws protocol
147 *
148 * LWS_WRITE_TEXT,
149 * LWS_WRITE_BINARY,
150 * LWS_WRITE_CONTINUATION,
151 * LWS_WRITE_PING,
152 * LWS_WRITE_PONG,
153 *
154 * or sending on http/2... the send buffer has to have LWS_PRE bytes valid
155 * BEFORE the buffer pointer you pass to lws_write(). Since you'll probably
156 * want to use http/2 before too long, it's wise to just always do this with
157 * lws_write buffers... LWS_PRE is typically 16 bytes it's not going to hurt
158 * usually.
159 *
160 * start of alloc ptr passed to lws_write end of allocation
161 * | | |
162 * v <-- LWS_PRE bytes --> v v
163 * [---------------- allocated memory ---------------]
164 * (for lws use) [====== user buffer ======]
165 *
166 * This allows us to add protocol info before the data, and send as one packet
167 * on the network without payload copying, for maximum efficiency.
168 *
169 * So for example you need this kind of code to use lws_write with a
170 * 128-byte payload
171 *
172 * char buf[LWS_PRE + 128];
173 *
174 * // fill your part of the buffer... for example here it's all zeros
175 * memset(&buf[LWS_PRE], 0, 128);
176 *
177 * if (lws_write(wsi, &buf[LWS_PRE], 128, LWS_WRITE_TEXT) < 128) {
178 * ... the connection is dead ...
179 * return -1;
180 * }
181 *
182 * LWS_PRE is currently 16, which covers ws and h2 frame headers, and is
183 * compatible with 32 and 64-bit alignment requirements.
184 *
185 * (LWS_SEND_BUFFER_POST_PADDING is deprecated, it's now 0 and can be left off.)
186 *
187 * Return may be -1 is the write failed in a way indicating that the connection
188 * has ended already, in which case you can close your side, or a positive
189 * number that is at least the number of bytes requested to send (under some
190 * encapsulation scenarios, it can indicate more than you asked was sent).
191 *
192 * The recommended test of the return is less than what you asked indicates
193 * the connection has failed.
194 *
195 * Truncated Writes
196 * ================
197 *
198 * The OS may not accept everything you asked to write on the connection.
199 *
200 * Posix defines POLLOUT indication from poll() to show that the connection
201 * will accept more write data, but it doesn't specifiy how much. It may just
202 * accept one byte of whatever you wanted to send.
203 *
204 * LWS will buffer the remainder automatically, and send it out autonomously.
205 *
206 * During that time, WRITABLE callbacks to user code will be suppressed and
207 * instead used internally. After it completes, it will send an extra WRITEABLE
208 * callback to the user code, in case any request was missed. So it is possible
209 * to receive unasked-for WRITEABLE callbacks, the user code should have enough
210 * state to know if it wants to write anything and just return if not.
211 *
212 * This is to handle corner cases where unexpectedly the OS refuses what we
213 * usually expect it to accept. It's not recommended as the way to randomly
214 * send huge payloads, since it is being copied on to heap and is inefficient.
215 *
216 * Huge payloads should instead be sent in fragments that are around 2 x mtu,
217 * which is almost always directly accepted by the OS. To simplify this for
218 * ws fragments, there is a helper lws_write_ws_flags() below that simplifies
219 * selecting the correct flags to give lws_write() for each fragment.
220 *
221 * In the case of RFC8441 ws-over-h2, you cannot send ws fragments larger than
222 * the max h2 frame size, typically 16KB, but should further restrict it to
223 * the same ~2 x mtu limit mentioned above.
224 */
225 LWS_VISIBLE LWS_EXTERN int
226 lws_write(struct lws *wsi, unsigned char *buf, size_t len,
227 enum lws_write_protocol protocol);
228
229 /* helper for case where buffer may be const */
230 #define lws_write_http(wsi, buf, len) \
231 lws_write(wsi, (unsigned char *)(buf), len, LWS_WRITE_HTTP)
232
233 /**
234 * lws_write_ws_flags() - Helper for multi-frame ws message flags
235 *
236 * \param initial: the lws_write flag to use for the start fragment, eg,
237 * LWS_WRITE_TEXT
238 * \param is_start: nonzero if this is the first fragment of the message
239 * \param is_end: nonzero if this is the last fragment of the message
240 *
241 * Returns the correct LWS_WRITE_ flag to use for each fragment of a message
242 * in turn.
243 */
244 static LWS_INLINE int
lws_write_ws_flags(int initial,int is_start,int is_end)245 lws_write_ws_flags(int initial, int is_start, int is_end)
246 {
247 int r;
248
249 if (is_start)
250 r = initial;
251 else
252 r = LWS_WRITE_CONTINUATION;
253
254 if (!is_end)
255 r |= LWS_WRITE_NO_FIN;
256
257 return r;
258 }
259
260 /**
261 * lws_raw_transaction_completed() - Helper for flushing before close
262 *
263 * \param wsi: the struct lws to operate on
264 *
265 * Returns -1 if the wsi can close now. However if there is buffered, unsent
266 * data, the wsi is marked as to be closed when the output buffer data is
267 * drained, and it returns 0.
268 *
269 * For raw cases where the transaction completed without failure,
270 * `return lws_raw_transaction_completed(wsi)` should better be used than
271 * return -1.
272 */
273 LWS_VISIBLE LWS_EXTERN int LWS_WARN_UNUSED_RESULT
274 lws_raw_transaction_completed(struct lws *wsi);
275
276 ///@}
277