core_filters.c 31.1 KB
Newer Older
powelld's avatar
powelld committed
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
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @file  core_filters.c
 * @brief Core input/output network filters.
 */

#include "apr.h"
#include "apr_strings.h"
#include "apr_lib.h"
#include "apr_fnmatch.h"
#include "apr_hash.h"
#include "apr_thread_proc.h"    /* for RLIMIT stuff */

#define APR_WANT_IOVEC
#define APR_WANT_STRFUNC
#define APR_WANT_MEMFUNC
#include "apr_want.h"

#include "ap_config.h"
#include "httpd.h"
#include "http_config.h"
#include "http_core.h"
#include "http_protocol.h" /* For index_of_response().  Grump. */
#include "http_request.h"
#include "http_vhost.h"
#include "http_main.h"     /* For the default_handler below... */
#include "http_log.h"
#include "util_md5.h"
#include "http_connection.h"
#include "apr_buckets.h"
#include "util_filter.h"
#include "util_ebcdic.h"
#include "mpm_common.h"
#include "scoreboard.h"
#include "mod_core.h"
#include "ap_listen.h"

#include "mod_so.h" /* for ap_find_loaded_module_symbol */

#define AP_MIN_SENDFILE_BYTES           (256)

/**
 * Remove all zero length buckets from the brigade.
 */
#define BRIGADE_NORMALIZE(b) \
do { \
    apr_bucket *e = APR_BRIGADE_FIRST(b); \
    do {  \
        if (e->length == 0 && !APR_BUCKET_IS_METADATA(e)) { \
            apr_bucket *d; \
            d = APR_BUCKET_NEXT(e); \
            apr_bucket_delete(e); \
            e = d; \
        } \
        else { \
            e = APR_BUCKET_NEXT(e); \
        } \
    } while (!APR_BRIGADE_EMPTY(b) && (e != APR_BRIGADE_SENTINEL(b))); \
} while (0)

/* we know core's module_index is 0 */
#undef APLOG_MODULE_INDEX
#define APLOG_MODULE_INDEX AP_CORE_MODULE_INDEX

struct core_output_filter_ctx {
    apr_bucket_brigade *buffered_bb;
    apr_bucket_brigade *tmp_flush_bb;
    apr_pool_t *deferred_write_pool;
    apr_size_t bytes_written;
};

struct core_filter_ctx {
    apr_bucket_brigade *b;
    apr_bucket_brigade *tmpbb;
};


apr_status_t ap_core_input_filter(ap_filter_t *f, apr_bucket_brigade *b,
                                  ap_input_mode_t mode, apr_read_type_e block,
                                  apr_off_t readbytes)
{
    apr_status_t rv;
    core_net_rec *net = f->ctx;
    core_ctx_t *ctx = net->in_ctx;
    const char *str;
    apr_size_t len;

    if (mode == AP_MODE_INIT) {
        /*
         * this mode is for filters that might need to 'initialize'
         * a connection before reading request data from a client.
         * NNTP over SSL for example needs to handshake before the
         * server sends the welcome message.
         * such filters would have changed the mode before this point
         * is reached.  however, protocol modules such as NNTP should
         * not need to know anything about SSL.  given the example, if
         * SSL is not in the filter chain, AP_MODE_INIT is a noop.
         */
        return APR_SUCCESS;
    }

    if (!ctx)
    {
        net->in_ctx = ctx = apr_palloc(f->c->pool, sizeof(*ctx));
        ctx->b = apr_brigade_create(f->c->pool, f->c->bucket_alloc);
        ctx->tmpbb = apr_brigade_create(f->c->pool, f->c->bucket_alloc);
        /* seed the brigade with the client socket. */
        rv = ap_run_insert_network_bucket(f->c, ctx->b, net->client_socket);
        if (rv != APR_SUCCESS)
            return rv;
    }
    else if (APR_BRIGADE_EMPTY(ctx->b)) {
        return APR_EOF;
    }

    /* ### This is bad. */
    BRIGADE_NORMALIZE(ctx->b);

    /* check for empty brigade again *AFTER* BRIGADE_NORMALIZE()
     * If we have lost our socket bucket (see above), we are EOF.
     *
     * Ideally, this should be returning SUCCESS with EOS bucket, but
     * some higher-up APIs (spec. read_request_line via ap_rgetline)
     * want an error code. */
    if (APR_BRIGADE_EMPTY(ctx->b)) {
        return APR_EOF;
    }

    if (mode == AP_MODE_GETLINE) {
        /* we are reading a single LF line, e.g. the HTTP headers */
        rv = apr_brigade_split_line(b, ctx->b, block, HUGE_STRING_LEN);
        /* We should treat EAGAIN here the same as we do for EOF (brigade is
         * empty).  We do this by returning whatever we have read.  This may
         * or may not be bogus, but is consistent (for now) with EOF logic.
         */
        if (APR_STATUS_IS_EAGAIN(rv) && block == APR_NONBLOCK_READ) {
            rv = APR_SUCCESS;
        }
        return rv;
    }

    /* ### AP_MODE_PEEK is a horrific name for this mode because we also
     * eat any CRLFs that we see.  That's not the obvious intention of
     * this mode.  Determine whether anyone actually uses this or not. */
    if (mode == AP_MODE_EATCRLF) {
        apr_bucket *e;
        const char *c;

        /* The purpose of this loop is to ignore any CRLF (or LF) at the end
         * of a request.  Many browsers send extra lines at the end of POST
         * requests.  We use the PEEK method to determine if there is more
         * data on the socket, so that we know if we should delay sending the
         * end of one request until we have served the second request in a
         * pipelined situation.  We don't want to actually delay sending a
         * response if the server finds a CRLF (or LF), becuause that doesn't
         * mean that there is another request, just a blank line.
         */
        while (1) {
            if (APR_BRIGADE_EMPTY(ctx->b))
                return APR_EOF;

            e = APR_BRIGADE_FIRST(ctx->b);

            rv = apr_bucket_read(e, &str, &len, APR_NONBLOCK_READ);

            if (rv != APR_SUCCESS)
                return rv;

            c = str;
            while (c < str + len) {
                if (*c == APR_ASCII_LF)
                    c++;
                else if (*c == APR_ASCII_CR && *(c + 1) == APR_ASCII_LF)
                    c += 2;
                else
                    return APR_SUCCESS;
            }

            /* If we reach here, we were a bucket just full of CRLFs, so
             * just toss the bucket. */
            /* FIXME: Is this the right thing to do in the core? */
            apr_bucket_delete(e);
        }
        return APR_SUCCESS;
    }

    /* If mode is EXHAUSTIVE, we want to just read everything until the end
     * of the brigade, which in this case means the end of the socket.
     * To do this, we attach the brigade that has currently been setaside to
     * the brigade that was passed down, and send that brigade back.
     *
     * NOTE:  This is VERY dangerous to use, and should only be done with
     * extreme caution.  FWLIW, this would be needed by an MPM like Perchild;
     * such an MPM can easily request the socket and all data that has been
     * read, which means that it can pass it to the correct child process.
     */
    if (mode == AP_MODE_EXHAUSTIVE) {
        apr_bucket *e;

        /* Tack on any buckets that were set aside. */
        APR_BRIGADE_CONCAT(b, ctx->b);

        /* Since we've just added all potential buckets (which will most
         * likely simply be the socket bucket) we know this is the end,
         * so tack on an EOS too. */
        /* We have read until the brigade was empty, so we know that we
         * must be EOS. */
        e = apr_bucket_eos_create(f->c->bucket_alloc);
        APR_BRIGADE_INSERT_TAIL(b, e);
        return APR_SUCCESS;
    }

    /* read up to the amount they specified. */
    if (mode == AP_MODE_READBYTES || mode == AP_MODE_SPECULATIVE) {
        apr_bucket *e;

        AP_DEBUG_ASSERT(readbytes > 0);

        e = APR_BRIGADE_FIRST(ctx->b);
        rv = apr_bucket_read(e, &str, &len, block);

        if (APR_STATUS_IS_EAGAIN(rv) && block == APR_NONBLOCK_READ) {
            /* getting EAGAIN for a blocking read is an error; for a
             * non-blocking read, return an empty brigade. */
            return APR_SUCCESS;
        }
        else if (rv != APR_SUCCESS) {
            return rv;
        }
        else if (block == APR_BLOCK_READ && len == 0) {
            /* We wanted to read some bytes in blocking mode.  We read
             * 0 bytes.  Hence, we now assume we are EOS.
             *
             * When we are in normal mode, return an EOS bucket to the
             * caller.
             * When we are in speculative mode, leave ctx->b empty, so
             * that the next call returns an EOS bucket.
             */
            apr_bucket_delete(e);

            if (mode == AP_MODE_READBYTES) {
                e = apr_bucket_eos_create(f->c->bucket_alloc);
                APR_BRIGADE_INSERT_TAIL(b, e);
            }
            return APR_SUCCESS;
        }

        /* Have we read as much data as we wanted (be greedy)? */
        if (len < readbytes) {
            apr_size_t bucket_len;

            rv = APR_SUCCESS;
            /* We already registered the data in e in len */
            e = APR_BUCKET_NEXT(e);
            while ((len < readbytes) && (rv == APR_SUCCESS)
                   && (e != APR_BRIGADE_SENTINEL(ctx->b))) {
                /* Check for the availability of buckets with known length */
                if (e->length != -1) {
                    len += e->length;
                    e = APR_BUCKET_NEXT(e);
                }
                else {
                    /*
                     * Read from bucket, but non blocking. If there isn't any
                     * more data, well than this is fine as well, we will
                     * not wait for more since we already got some and we are
                     * only checking if there isn't more.
                     */
                    rv = apr_bucket_read(e, &str, &bucket_len,
                                         APR_NONBLOCK_READ);
                    if (rv == APR_SUCCESS) {
                        len += bucket_len;
                        e = APR_BUCKET_NEXT(e);
                    }
                }
            }
        }

        /* We can only return at most what we read. */
        if (len < readbytes) {
            readbytes = len;
        }

        rv = apr_brigade_partition(ctx->b, readbytes, &e);
        if (rv != APR_SUCCESS) {
            return rv;
        }

        /* Must do move before CONCAT */
        ctx->tmpbb = apr_brigade_split_ex(ctx->b, e, ctx->tmpbb);

        if (mode == AP_MODE_READBYTES) {
            APR_BRIGADE_CONCAT(b, ctx->b);
        }
        else if (mode == AP_MODE_SPECULATIVE) {
            apr_bucket *copy_bucket;

            for (e = APR_BRIGADE_FIRST(ctx->b);
                 e != APR_BRIGADE_SENTINEL(ctx->b);
                 e = APR_BUCKET_NEXT(e))
            {
                rv = apr_bucket_copy(e, &copy_bucket);
                if (rv != APR_SUCCESS) {
                    return rv;
                }
                APR_BRIGADE_INSERT_TAIL(b, copy_bucket);
            }
        }

        /* Take what was originally there and place it back on ctx->b */
        APR_BRIGADE_CONCAT(ctx->b, ctx->tmpbb);
    }
    return APR_SUCCESS;
}

static void setaside_remaining_output(ap_filter_t *f,
                                      core_output_filter_ctx_t *ctx,
                                      apr_bucket_brigade *bb,
                                      conn_rec *c);

static apr_status_t send_brigade_nonblocking(apr_socket_t *s,
                                             apr_bucket_brigade *bb,
                                             apr_size_t *bytes_written,
                                             conn_rec *c);

static void remove_empty_buckets(apr_bucket_brigade *bb);

static apr_status_t send_brigade_blocking(apr_socket_t *s,
                                          apr_bucket_brigade *bb,
                                          apr_size_t *bytes_written,
                                          conn_rec *c);

static apr_status_t writev_nonblocking(apr_socket_t *s,
                                       struct iovec *vec, apr_size_t nvec,
                                       apr_bucket_brigade *bb,
                                       apr_size_t *cumulative_bytes_written,
                                       conn_rec *c);

#if APR_HAS_SENDFILE
static apr_status_t sendfile_nonblocking(apr_socket_t *s,
                                         apr_bucket *bucket,
                                         apr_size_t *cumulative_bytes_written,
                                         conn_rec *c);
#endif

/* XXX: Should these be configurable parameters? */
#define THRESHOLD_MIN_WRITE 4096
#define THRESHOLD_MAX_BUFFER 65536
#define MAX_REQUESTS_IN_PIPELINE 5

/* Optional function coming from mod_logio, used for logging of output
 * traffic
 */
extern APR_OPTIONAL_FN_TYPE(ap_logio_add_bytes_out) *ap__logio_add_bytes_out;

apr_status_t ap_core_output_filter(ap_filter_t *f, apr_bucket_brigade *new_bb)
{
    conn_rec *c = f->c;
    core_net_rec *net = f->ctx;
    core_output_filter_ctx_t *ctx = net->out_ctx;
    apr_bucket_brigade *bb = NULL;
    apr_bucket *bucket, *next, *flush_upto = NULL;
    apr_size_t bytes_in_brigade, non_file_bytes_in_brigade;
    int eor_buckets_in_brigade, morphing_bucket_in_brigade;
    apr_status_t rv;

    /* Fail quickly if the connection has already been aborted. */
    if (c->aborted) {
        if (new_bb != NULL) {
            apr_brigade_cleanup(new_bb);
        }
        return APR_ECONNABORTED;
    }

    if (ctx == NULL) {
        ctx = apr_pcalloc(c->pool, sizeof(*ctx));
        net->out_ctx = (core_output_filter_ctx_t *)ctx;
        /*
         * Need to create tmp brigade with correct lifetime. Passing
         * NULL to apr_brigade_split_ex would result in a brigade
         * allocated from bb->pool which might be wrong.
         */
        ctx->tmp_flush_bb = apr_brigade_create(c->pool, c->bucket_alloc);
        /* same for buffered_bb and ap_save_brigade */
        ctx->buffered_bb = apr_brigade_create(c->pool, c->bucket_alloc);
    }

    if (new_bb != NULL)
        bb = new_bb;

    if ((ctx->buffered_bb != NULL) &&
        !APR_BRIGADE_EMPTY(ctx->buffered_bb)) {
        if (new_bb != NULL) {
            APR_BRIGADE_PREPEND(bb, ctx->buffered_bb);
        }
        else {
            bb = ctx->buffered_bb;
        }
        c->data_in_output_filters = 0;
    }
    else if (new_bb == NULL) {
        return APR_SUCCESS;
    }

    /* Scan through the brigade and decide whether to attempt a write,
     * and how much to write, based on the following rules:
     *
     *  1) The new_bb is null: Do a nonblocking write of as much as
     *     possible: do a nonblocking write of as much data as possible,
     *     then save the rest in ctx->buffered_bb.  (If new_bb == NULL,
     *     it probably means that the MPM is doing asynchronous write
     *     completion and has just determined that this connection
     *     is writable.)
     *
     *  2) Determine if and up to which bucket we need to do a blocking
     *     write:
     *
     *  a) The brigade contains a flush bucket: Do a blocking write
     *     of everything up that point.
     *
     *  b) The request is in CONN_STATE_HANDLER state, and the brigade
     *     contains at least THRESHOLD_MAX_BUFFER bytes in non-file
     *     buckets: Do blocking writes until the amount of data in the
     *     buffer is less than THRESHOLD_MAX_BUFFER.  (The point of this
     *     rule is to provide flow control, in case a handler is
     *     streaming out lots of data faster than the data can be
     *     sent to the client.)
     *
     *  c) The request is in CONN_STATE_HANDLER state, and the brigade
     *     contains at least MAX_REQUESTS_IN_PIPELINE EOR buckets:
     *     Do blocking writes until less than MAX_REQUESTS_IN_PIPELINE EOR
     *     buckets are left. (The point of this rule is to prevent too many
     *     FDs being kept open by pipelined requests, possibly allowing a
     *     DoS).
     *
     *  d) The brigade contains a morphing bucket: If there was no other
     *     reason to do a blocking write yet, try reading the bucket. If its
     *     contents fit into memory before THRESHOLD_MAX_BUFFER is reached,
     *     everything is fine. Otherwise we need to do a blocking write the
     *     up to and including the morphing bucket, because ap_save_brigade()
     *     would read the whole bucket into memory later on.
     *
     *  3) Actually do the blocking write up to the last bucket determined
     *     by rules 2a-d. The point of doing only one flush is to make as
     *     few calls to writev() as possible.
     *
     *  4) If the brigade contains at least THRESHOLD_MIN_WRITE
     *     bytes: Do a nonblocking write of as much data as possible,
     *     then save the rest in ctx->buffered_bb.
     */

    if (new_bb == NULL) {
        rv = send_brigade_nonblocking(net->client_socket, bb,
                                      &(ctx->bytes_written), c);
        if (rv != APR_SUCCESS && !APR_STATUS_IS_EAGAIN(rv)) {
            /* The client has aborted the connection */
            ap_log_cerror(APLOG_MARK, APLOG_TRACE1, rv, c,
                          "core_output_filter: writing data to the network");
            apr_brigade_cleanup(bb);
            c->aborted = 1;
            return rv;
        }
        setaside_remaining_output(f, ctx, bb, c);
        return APR_SUCCESS;
    }

    bytes_in_brigade = 0;
    non_file_bytes_in_brigade = 0;
    eor_buckets_in_brigade = 0;
    morphing_bucket_in_brigade = 0;

    for (bucket = APR_BRIGADE_FIRST(bb); bucket != APR_BRIGADE_SENTINEL(bb);
         bucket = next) {
        next = APR_BUCKET_NEXT(bucket);

        if (!APR_BUCKET_IS_METADATA(bucket)) {
            if (bucket->length == (apr_size_t)-1) {
                /*
                 * A setaside of morphing buckets would read everything into
                 * memory. Instead, we will flush everything up to and
                 * including this bucket.
                 */
                morphing_bucket_in_brigade = 1;
            }
            else {
                bytes_in_brigade += bucket->length;
                if (!APR_BUCKET_IS_FILE(bucket))
                    non_file_bytes_in_brigade += bucket->length;
            }
        }
        else if (AP_BUCKET_IS_EOR(bucket)) {
            eor_buckets_in_brigade++;
        }

        if (APR_BUCKET_IS_FLUSH(bucket)
            || non_file_bytes_in_brigade >= THRESHOLD_MAX_BUFFER
            || morphing_bucket_in_brigade
            || eor_buckets_in_brigade > MAX_REQUESTS_IN_PIPELINE) {
            /* this segment of the brigade MUST be sent before returning. */

            if (APLOGctrace6(c)) {
                char *reason = APR_BUCKET_IS_FLUSH(bucket) ?
                               "FLUSH bucket" :
                               (non_file_bytes_in_brigade >= THRESHOLD_MAX_BUFFER) ?
                               "THRESHOLD_MAX_BUFFER" :
                               morphing_bucket_in_brigade ? "morphing bucket" :
                               "MAX_REQUESTS_IN_PIPELINE";
                ap_log_cerror(APLOG_MARK, APLOG_TRACE6, 0, c,
                              "core_output_filter: flushing because of %s",
                              reason);
            }
            /*
             * Defer the actual blocking write to avoid doing many writes.
             */
            flush_upto = next;

            bytes_in_brigade = 0;
            non_file_bytes_in_brigade = 0;
            eor_buckets_in_brigade = 0;
            morphing_bucket_in_brigade = 0;
        }
    }

    if (flush_upto != NULL) {
        ctx->tmp_flush_bb = apr_brigade_split_ex(bb, flush_upto,
                                                 ctx->tmp_flush_bb);
        rv = send_brigade_blocking(net->client_socket, bb,
                                   &(ctx->bytes_written), c);
        if (rv != APR_SUCCESS) {
            /* The client has aborted the connection */
            ap_log_cerror(APLOG_MARK, APLOG_TRACE1, rv, c,
                          "core_output_filter: writing data to the network");
            apr_brigade_cleanup(bb);
            c->aborted = 1;
            return rv;
        }
        APR_BRIGADE_CONCAT(bb, ctx->tmp_flush_bb);
    }

    if (bytes_in_brigade >= THRESHOLD_MIN_WRITE) {
        rv = send_brigade_nonblocking(net->client_socket, bb,
                                      &(ctx->bytes_written), c);
        if ((rv != APR_SUCCESS) && (!APR_STATUS_IS_EAGAIN(rv))) {
            /* The client has aborted the connection */
            ap_log_cerror(APLOG_MARK, APLOG_TRACE1, rv, c,
                          "core_output_filter: writing data to the network");
            apr_brigade_cleanup(bb);
            c->aborted = 1;
            return rv;
        }
    }

    setaside_remaining_output(f, ctx, bb, c);
    return APR_SUCCESS;
}

/*
 * This function assumes that either ctx->buffered_bb == NULL, or
 * ctx->buffered_bb is empty, or ctx->buffered_bb == bb
 */
static void setaside_remaining_output(ap_filter_t *f,
                                      core_output_filter_ctx_t *ctx,
                                      apr_bucket_brigade *bb,
                                      conn_rec *c)
{
    if (bb == NULL) {
        return;
    }
    remove_empty_buckets(bb);
    if (!APR_BRIGADE_EMPTY(bb)) {
        c->data_in_output_filters = 1;
        if (bb != ctx->buffered_bb) {
            if (!ctx->deferred_write_pool) {
                apr_pool_create(&ctx->deferred_write_pool, c->pool);
                apr_pool_tag(ctx->deferred_write_pool, "deferred_write");
            }
            ap_save_brigade(f, &(ctx->buffered_bb), &bb,
                            ctx->deferred_write_pool);
        }
    }
    else if (ctx->deferred_write_pool) {
        /*
         * There are no more requests in the pipeline. We can just clear the
         * pool.
         */
        apr_pool_clear(ctx->deferred_write_pool);
    }
}

#ifndef APR_MAX_IOVEC_SIZE
#define MAX_IOVEC_TO_WRITE 16
#else
#if APR_MAX_IOVEC_SIZE > 16
#define MAX_IOVEC_TO_WRITE 16
#else
#define MAX_IOVEC_TO_WRITE APR_MAX_IOVEC_SIZE
#endif
#endif

static apr_status_t send_brigade_nonblocking(apr_socket_t *s,
                                             apr_bucket_brigade *bb,
                                             apr_size_t *bytes_written,
                                             conn_rec *c)
{
    apr_bucket *bucket, *next;
    apr_status_t rv;
    struct iovec vec[MAX_IOVEC_TO_WRITE];
    apr_size_t nvec = 0;

    remove_empty_buckets(bb);

    for (bucket = APR_BRIGADE_FIRST(bb);
         bucket != APR_BRIGADE_SENTINEL(bb);
         bucket = next) {
        next = APR_BUCKET_NEXT(bucket);
#if APR_HAS_SENDFILE
        if (APR_BUCKET_IS_FILE(bucket)) {
            apr_bucket_file *file_bucket = (apr_bucket_file *)(bucket->data);
            apr_file_t *fd = file_bucket->fd;
            /* Use sendfile to send this file unless:
             *   - the platform doesn't support sendfile,
             *   - the file is too small for sendfile to be useful, or
             *   - sendfile is disabled in the httpd config via "EnableSendfile off"
             */

            if ((apr_file_flags_get(fd) & APR_SENDFILE_ENABLED) &&
                (bucket->length >= AP_MIN_SENDFILE_BYTES)) {
                if (nvec > 0) {
                    (void)apr_socket_opt_set(s, APR_TCP_NOPUSH, 1);
                    rv = writev_nonblocking(s, vec, nvec, bb, bytes_written, c);
                    if (rv != APR_SUCCESS) {
                        (void)apr_socket_opt_set(s, APR_TCP_NOPUSH, 0);
                        return rv;
                    }
                }
                rv = sendfile_nonblocking(s, bucket, bytes_written, c);
                if (nvec > 0) {
                    (void)apr_socket_opt_set(s, APR_TCP_NOPUSH, 0);
                    nvec = 0;
                }
                if (rv != APR_SUCCESS) {
                    return rv;
                }
                break;
            }
        }
#endif /* APR_HAS_SENDFILE */
        /* didn't sendfile */
        if (!APR_BUCKET_IS_METADATA(bucket)) {
            const char *data;
            apr_size_t length;
            
            /* Non-blocking read first, in case this is a morphing
             * bucket type. */
            rv = apr_bucket_read(bucket, &data, &length, APR_NONBLOCK_READ);
            if (APR_STATUS_IS_EAGAIN(rv)) {
                /* Read would block; flush any pending data and retry. */
                if (nvec) {
                    rv = writev_nonblocking(s, vec, nvec, bb, bytes_written, c);
                    if (rv) {
                        return rv;
                    }
                    nvec = 0;
                }
                
                rv = apr_bucket_read(bucket, &data, &length, APR_BLOCK_READ);
            }
            if (rv != APR_SUCCESS) {
                return rv;
            }

            /* reading may have split the bucket, so recompute next: */
            next = APR_BUCKET_NEXT(bucket);
            vec[nvec].iov_base = (char *)data;
            vec[nvec].iov_len = length;
            nvec++;
            if (nvec == MAX_IOVEC_TO_WRITE) {
                rv = writev_nonblocking(s, vec, nvec, bb, bytes_written, c);
                nvec = 0;
                if (rv != APR_SUCCESS) {
                    return rv;
                }
                break;
            }
        }
    }

    if (nvec > 0) {
        rv = writev_nonblocking(s, vec, nvec, bb, bytes_written, c);
        if (rv != APR_SUCCESS) {
            return rv;
        }
    }

    remove_empty_buckets(bb);

    return APR_SUCCESS;
}

static void remove_empty_buckets(apr_bucket_brigade *bb)
{
    apr_bucket *bucket;
    while (((bucket = APR_BRIGADE_FIRST(bb)) != APR_BRIGADE_SENTINEL(bb)) &&
           (APR_BUCKET_IS_METADATA(bucket) || (bucket->length == 0))) {
        apr_bucket_delete(bucket);
    }
}

static apr_status_t send_brigade_blocking(apr_socket_t *s,
                                          apr_bucket_brigade *bb,
                                          apr_size_t *bytes_written,
                                          conn_rec *c)
{
    apr_status_t rv;

    rv = APR_SUCCESS;
    while (!APR_BRIGADE_EMPTY(bb)) {
        rv = send_brigade_nonblocking(s, bb, bytes_written, c);
        if (rv != APR_SUCCESS) {
            if (APR_STATUS_IS_EAGAIN(rv)) {
                /* Wait until we can send more data */
                apr_int32_t nsds;
                apr_interval_time_t timeout;
                apr_pollfd_t pollset;

                pollset.p = c->pool;
                pollset.desc_type = APR_POLL_SOCKET;
                pollset.reqevents = APR_POLLOUT;
                pollset.desc.s = s;
                apr_socket_timeout_get(s, &timeout);
                do {
                    rv = apr_poll(&pollset, 1, &nsds, timeout);
                } while (APR_STATUS_IS_EINTR(rv));
                if (rv != APR_SUCCESS) {
                    break;
                }
            }
            else {
                break;
            }
        }
    }
    return rv;
}

static apr_status_t writev_nonblocking(apr_socket_t *s,
                                       struct iovec *vec, apr_size_t nvec,
                                       apr_bucket_brigade *bb,
                                       apr_size_t *cumulative_bytes_written,
                                       conn_rec *c)
{
    apr_status_t rv = APR_SUCCESS, arv;
    apr_size_t bytes_written = 0, bytes_to_write = 0;
    apr_size_t i, offset;
    apr_interval_time_t old_timeout;

    arv = apr_socket_timeout_get(s, &old_timeout);
    if (arv != APR_SUCCESS) {
        return arv;
    }
    arv = apr_socket_timeout_set(s, 0);
    if (arv != APR_SUCCESS) {
        return arv;
    }

    for (i = 0; i < nvec; i++) {
        bytes_to_write += vec[i].iov_len;
    }
    offset = 0;
    while (bytes_written < bytes_to_write) {
        apr_size_t n = 0;
        rv = apr_socket_sendv(s, vec + offset, nvec - offset, &n);
        if (n > 0) {
            bytes_written += n;
            for (i = offset; i < nvec; ) {
                apr_bucket *bucket = APR_BRIGADE_FIRST(bb);
                if (APR_BUCKET_IS_METADATA(bucket)) {
                    apr_bucket_delete(bucket);
                }
                else if (n >= vec[i].iov_len) {
                    apr_bucket_delete(bucket);
                    offset++;
                    n -= vec[i++].iov_len;
                }
                else {
                    apr_bucket_split(bucket, n);
                    apr_bucket_delete(bucket);
                    vec[i].iov_len -= n;
                    vec[i].iov_base = (char *) vec[i].iov_base + n;
                    break;
                }
            }
        }
        if (rv != APR_SUCCESS) {
            break;
        }
    }
    if ((ap__logio_add_bytes_out != NULL) && (bytes_written > 0)) {
        ap__logio_add_bytes_out(c, bytes_written);
    }
    *cumulative_bytes_written += bytes_written;

    arv = apr_socket_timeout_set(s, old_timeout);
    if ((arv != APR_SUCCESS) && (rv == APR_SUCCESS)) {
        return arv;
    }
    else {
        return rv;
    }
}

#if APR_HAS_SENDFILE

static apr_status_t sendfile_nonblocking(apr_socket_t *s,
                                         apr_bucket *bucket,
                                         apr_size_t *cumulative_bytes_written,
                                         conn_rec *c)
{
    apr_status_t rv = APR_SUCCESS;
    apr_bucket_file *file_bucket;
    apr_file_t *fd;
    apr_size_t file_length;
    apr_off_t file_offset;
    apr_size_t bytes_written = 0;

    if (!APR_BUCKET_IS_FILE(bucket)) {
        ap_log_error(APLOG_MARK, APLOG_ERR, rv, c->base_server, APLOGNO(00006)
                     "core_filter: sendfile_nonblocking: "
                     "this should never happen");
        return APR_EGENERAL;
    }
    file_bucket = (apr_bucket_file *)(bucket->data);
    fd = file_bucket->fd;
    file_length = bucket->length;
    file_offset = bucket->start;

    if (bytes_written < file_length) {
        apr_size_t n = file_length - bytes_written;
        apr_status_t arv;
        apr_interval_time_t old_timeout;

        arv = apr_socket_timeout_get(s, &old_timeout);
        if (arv != APR_SUCCESS) {
            return arv;
        }
        arv = apr_socket_timeout_set(s, 0);
        if (arv != APR_SUCCESS) {
            return arv;
        }
        rv = apr_socket_sendfile(s, fd, NULL, &file_offset, &n, 0);
        if (rv == APR_SUCCESS) {
            bytes_written += n;
            file_offset += n;
        }
        arv = apr_socket_timeout_set(s, old_timeout);
        if ((arv != APR_SUCCESS) && (rv == APR_SUCCESS)) {
            rv = arv;
        }
    }
    if ((ap__logio_add_bytes_out != NULL) && (bytes_written > 0)) {
        ap__logio_add_bytes_out(c, bytes_written);
    }
    *cumulative_bytes_written += bytes_written;
    if ((bytes_written < file_length) && (bytes_written > 0)) {
        apr_bucket_split(bucket, bytes_written);
        apr_bucket_delete(bucket);
    }
    else if (bytes_written == file_length) {
        apr_bucket_delete(bucket);
    }
    return rv;
}

#endif