summaryrefslogtreecommitdiffstats
path: root/src/util/nbbio.c
blob: 0f345ed6bfa083e20e2c763a31299aced7e9bc81 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
/*++
/* NAME
/*	nbbio 3
/* SUMMARY
/*	non-blocking buffered I/O
/* SYNOPSIS
/*	#include <nbbio.h>
/*
/*	NBBIO	*nbbio_create(fd, bufsize, label, action, context)
/*	int	fd;
/*	ssize_t	bufsize;
/*	const char *label;
/*	void	(*action)(int event, void *context);
/*	char	*context;
/*
/*	void	nbbio_free(np)
/*	NBBIO	*np;
/*
/*	void	nbbio_enable_read(np, timeout)
/*	NBBIO	*np;
/*	int	timeout;
/*
/*	void	nbbio_enable_write(np, timeout)
/*	NBBIO	*np;
/*	int	timeout;
/*
/*	void	nbbio_disable_readwrite(np)
/*	NBBIO	*np;
/*
/*	void	nbbio_slumber(np, timeout)
/*	NBBIO	*np;
/*	int	timeout;
/*
/*	int	NBBIO_ACTIVE_FLAGS(np)
/*	NBBIO	*np;
/*
/*	int	NBBIO_ERROR_FLAGS(np)
/*	NBBIO	*np;
/*
/*	const ssize_t NBBIO_BUFSIZE(np)
/*	NBBIO	*np;
/*
/*	ssize_t	NBBIO_READ_PEND(np)
/*	NBBIO	*np;
/*
/*	char	*NBBIO_READ_BUF(np)
/*	NBBIO	*np;
/*
/*	const ssize_t NBBIO_WRITE_PEND(np)
/*	NBBIO	*np;
/*
/*	char	*NBBIO_WRITE_BUF(np)
/*	NBBIO	*np;
/* DESCRIPTION
/*	This module implements low-level support for event-driven
/*	I/O on a full-duplex stream. Read/write events are handled
/*	by pseudothreads that run under control by the events(5)
/*	module.  After each I/O operation, the application is
/*	notified via a call-back routine.
/*
/*	It is up to the call-back routine to turn on/off read/write
/*	events as appropriate.  It is an error to leave read events
/*	enabled for a buffer that is full, or to leave write events
/*	enabled for a buffer that is empty.
/*
/*	nbbio_create() creates a pair of buffers of the named size
/*	for the named stream. The label specifies the purpose of
/*	the stream, and is used for diagnostic messages.  The
/*	nbbio(3) event handler invokes the application call-back
/*	routine with the current event type (EVENT_READ etc.) and
/*	with the application-specified context.
/*
/*	nbbio_free() terminates any pseudothreads associated with
/*	the named buffer pair, closes the stream, and destroys the
/*	buffer pair.
/*
/*	nbbio_enable_read() enables a read pseudothread for the
/*	named buffer pair.  It is an error to enable a read
/*	pseudothread while the read buffer is full, or while a read
/*	or write pseudothread is still enabled.
/*
/*	nbbio_enable_write() enables a write pseudothread for the
/*	named buffer pair.  It is an error to enable a write
/*	pseudothread while the write buffer is empty, or while a
/*	read or write pseudothread is still enabled.
/*
/*	nbbio_disable_readwrite() disables any read/write pseudothreads
/*	for the named buffer pair, including timeouts. To ensure
/*	buffer liveness, use nbbio_slumber() instead of
/*	nbbio_disable_readwrite().  It is no error to call this
/*	function while no read/write pseudothread is enabled.
/*
/*	nbbio_slumber() disables any read/write pseudothreads for
/*	the named buffer pair, but keeps the timer active to ensure
/*	buffer liveness. It is no error to call this function while
/*	no read/write pseudothread is enabled.
/*
/*	NBBIO_ERROR_FLAGS() returns the error flags for the named buffer
/*	pair: zero or more of NBBIO_FLAG_EOF (read EOF), NBBIO_FLAG_ERROR
/*	(read/write error) or NBBIO_FLAG_TIMEOUT (time limit
/*	exceeded).
/*
/*	NBBIO_ACTIVE_FLAGS() returns the pseudothread flags for the
/*	named buffer pair: NBBIO_FLAG_READ (read pseudothread is
/*	active), NBBIO_FLAG_WRITE (write pseudothread is active),
/*	or zero (no pseudothread is active).
/*
/*	NBBIO_WRITE_PEND() and NBBIO_WRITE_BUF() evaluate to the
/*	number of to-be-written bytes and the write buffer for the
/*	named buffer pair. NBBIO_WRITE_PEND() must be updated by
/*	the application code that fills the write buffer; no more
/*	than NBBIO_BUFSIZE() bytes may be filled.
/*
/*	NBBIO_READ_PEND() and NBBIO_READ_BUF() evaluate to the
/*	number of unread bytes and the read buffer for the named
/*	buffer pair. NBBIO_READ_PEND() and NBBIO_READ_BUF() must
/*	be updated by the application code that drains the read
/*	buffer.
/* SEE ALSO
/*	events(3) event manager
/* DIAGNOSTICS
/*	Panic: interface violation.
/*
/*	Fatal: out of memory.
/* LICENSE
/* .ad
/* .fi
/*	The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*	Wietse Venema
/*	IBM T.J. Watson Research
/*	P.O. Box 704
/*	Yorktown Heights, NY 10598, USA
/*--*/

 /*
  * System library.
  */
#include <sys_defs.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>			/* memmove() */

 /*
  * Utility library.
  */
#include <mymalloc.h>
#include <msg.h>
#include <events.h>
#include <nbbio.h>

/* nbbio_event - non-blocking event handler */

static void nbbio_event(int event, void *context)
{
    const char *myname = "nbbio_event";
    NBBIO  *np = (NBBIO *) context;
    ssize_t count;

    switch (event) {

	/*
	 * Read data into the read buffer. Leave it up to the application to
	 * drain the buffer until it is empty.
	 */
    case EVENT_READ:
	if (np->read_pend == np->bufsize)
	    msg_panic("%s: socket fd=%d: read buffer is full",
		      myname, np->fd);
	if (np->read_pend < 0 || np->read_pend > np->bufsize)
	    msg_panic("%s: socket fd=%d: bad pending read count %ld",
		      myname, np->fd, (long) np->read_pend);
	count = read(np->fd, np->read_buf + np->read_pend,
		     np->bufsize - np->read_pend);
	if (count > 0) {
	    np->read_pend += count;
	    if (msg_verbose)
		msg_info("%s: read %ld on %s fd=%d",
			 myname, (long) count, np->label, np->fd);
	} else if (count == 0) {
	    np->flags |= NBBIO_FLAG_EOF;
	    if (msg_verbose)
		msg_info("%s: read EOF on %s fd=%d",
			 myname, np->label, np->fd);
	} else {
	    if (errno == EAGAIN)
		msg_warn("%s: read() returns EAGAIN on readable descriptor",
			 myname);
	    np->flags |= NBBIO_FLAG_ERROR;
	    if (msg_verbose)
		msg_info("%s: read %s fd=%d: %m", myname, np->label, np->fd);
	}
	break;

	/*
	 * Drain data from the output buffer.  Notify the application
	 * whenever some bytes are written.
	 * 
	 * XXX Enforce a total time limit to ensure liveness when a hostile
	 * receiver sets a very small TCP window size.
	 */
    case EVENT_WRITE:
	if (np->write_pend == 0)
	    msg_panic("%s: socket fd=%d: empty write buffer", myname, np->fd);
	if (np->write_pend < 0 || np->write_pend > np->bufsize)
	    msg_panic("%s: socket fd=%d: bad pending write count %ld",
		      myname, np->fd, (long) np->write_pend);
	count = write(np->fd, np->write_buf, np->write_pend);
	if (count > 0) {
	    np->write_pend -= count;
	    if (np->write_pend > 0)
		memmove(np->write_buf, np->write_buf + count, np->write_pend);
	} else {
	    if (errno == EAGAIN)
		msg_warn("%s: write() returns EAGAIN on writable descriptor",
			 myname);
	    np->flags |= NBBIO_FLAG_ERROR;
	    if (msg_verbose)
		msg_info("%s: write %s fd=%d: %m", myname, np->label, np->fd);
	}
	break;

	/*
	 * Something bad happened.
	 */
    case EVENT_XCPT:
	np->flags |= NBBIO_FLAG_ERROR;
	if (msg_verbose)
	    msg_info("%s: error on %s fd=%d: %m", myname, np->label, np->fd);
	break;

	/*
	 * Something good didn't happen.
	 */
    case EVENT_TIME:
	np->flags |= NBBIO_FLAG_TIMEOUT;
	if (msg_verbose)
	    msg_info("%s: %s timeout on %s fd=%d",
		     myname, NBBIO_OP_NAME(np), np->label, np->fd);
	break;

    default:
	msg_panic("%s: unknown event %d", myname, event);
    }

    /*
     * Application notification. The application will check for any error
     * flags, copy application data from or to our buffer pair, and decide
     * what I/O happens next.
     */
    np->action(event, np->context);
}

/* nbbio_enable_read - enable reading from socket into buffer */

void    nbbio_enable_read(NBBIO *np, int timeout)
{
    const char *myname = "nbbio_enable_read";

    /*
     * Sanity checks.
     */
    if (np->flags & NBBIO_MASK_ACTIVE)
	msg_panic("%s: socket fd=%d is enabled for %s",
		  myname, np->fd, NBBIO_OP_NAME(np));
    if (timeout <= 0)
	msg_panic("%s: socket fd=%d: bad timeout %d",
		  myname, np->fd, timeout);
    if (np->read_pend >= np->bufsize)
	msg_panic("%s: socket fd=%d: read buffer is full",
		  myname, np->fd);

    /*
     * Enable events.
     */
    event_enable_read(np->fd, nbbio_event, (void *) np);
    event_request_timer(nbbio_event, (void *) np, timeout);
    np->flags |= NBBIO_FLAG_READ;
}

/* nbbio_enable_write - enable writing from buffer to socket */

void    nbbio_enable_write(NBBIO *np, int timeout)
{
    const char *myname = "nbbio_enable_write";

    /*
     * Sanity checks.
     */
    if (np->flags & NBBIO_MASK_ACTIVE)
	msg_panic("%s: socket fd=%d is enabled for %s",
		  myname, np->fd, NBBIO_OP_NAME(np));
    if (timeout <= 0)
	msg_panic("%s: socket fd=%d bad timeout %d",
		  myname, np->fd, timeout);
    if (np->write_pend <= 0)
	msg_panic("%s: socket fd=%d: empty write buffer",
		  myname, np->fd);

    /*
     * Enable events.
     */
    event_enable_write(np->fd, nbbio_event, (void *) np);
    event_request_timer(nbbio_event, (void *) np, timeout);
    np->flags |= NBBIO_FLAG_WRITE;
}

/* nbbio_disable_readwrite - disable read/write/timer events */

void    nbbio_disable_readwrite(NBBIO *np)
{
    np->flags &= ~NBBIO_MASK_ACTIVE;
    event_disable_readwrite(np->fd);
    event_cancel_timer(nbbio_event, (void *) np);
}

/* nbbio_slumber - disable read/write events, keep timer */

void    nbbio_slumber(NBBIO *np, int timeout)
{
    np->flags &= ~NBBIO_MASK_ACTIVE;
    event_disable_readwrite(np->fd);
    event_request_timer(nbbio_event, (void *) np, timeout);
}

/* nbbio_create - create socket buffer */

NBBIO  *nbbio_create(int fd, ssize_t bufsize, const char *label,
		             NBBIO_ACTION action, void *context)
{
    NBBIO  *np;

    /*
     * Sanity checks.
     */
    if (fd < 0)
	msg_panic("nbbio_create: bad file descriptor: %d", fd);
    if (bufsize <= 0)
	msg_panic("nbbio_create: bad buffer size: %ld", (long) bufsize);

    /*
     * Create a new buffer pair.
     */
    np = (NBBIO *) mymalloc(sizeof(*np));
    np->fd = fd;
    np->bufsize = bufsize;
    np->label = mystrdup(label);
    np->action = action;
    np->context = context;
    np->flags = 0;

    np->read_buf = mymalloc(bufsize);
    np->read_pend = 0;

    np->write_buf = mymalloc(bufsize);
    np->write_pend = 0;

    return (np);
}

/* nbbio_free - destroy socket buffer */

void    nbbio_free(NBBIO *np)
{
    nbbio_disable_readwrite(np);
    (void) close(np->fd);
    myfree(np->label);
    myfree(np->read_buf);
    myfree(np->write_buf);
    myfree((void *) np);
}