Willy Tarreau | baaee00 | 2006-06-26 02:48:02 +0200 | [diff] [blame] | 1 | /* |
Willy Tarreau | 7c3c541 | 2009-12-13 15:53:05 +0100 | [diff] [blame] | 2 | * include/types/buffers.h |
| 3 | * Buffer management definitions, macros and inline functions. |
| 4 | * |
| 5 | * Copyright (C) 2000-2009 Willy Tarreau - w@1wt.eu |
| 6 | * |
| 7 | * This library is free software; you can redistribute it and/or |
| 8 | * modify it under the terms of the GNU Lesser General Public |
| 9 | * License as published by the Free Software Foundation, version 2.1 |
| 10 | * exclusively. |
| 11 | * |
| 12 | * This library is distributed in the hope that it will be useful, |
| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 15 | * Lesser General Public License for more details. |
| 16 | * |
| 17 | * You should have received a copy of the GNU Lesser General Public |
| 18 | * License along with this library; if not, write to the Free Software |
| 19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 20 | */ |
Willy Tarreau | baaee00 | 2006-06-26 02:48:02 +0200 | [diff] [blame] | 21 | |
| 22 | #ifndef _TYPES_BUFFERS_H |
| 23 | #define _TYPES_BUFFERS_H |
| 24 | |
Willy Tarreau | e3ba5f0 | 2006-06-29 18:54:54 +0200 | [diff] [blame] | 25 | #include <common/config.h> |
Willy Tarreau | 2dd0d47 | 2006-06-29 17:53:05 +0200 | [diff] [blame] | 26 | #include <common/memory.h> |
Willy Tarreau | 0a5d5dd | 2008-11-23 19:31:35 +0100 | [diff] [blame] | 27 | #include <types/stream_interface.h> |
Willy Tarreau | baaee00 | 2006-06-26 02:48:02 +0200 | [diff] [blame] | 28 | |
Willy Tarreau | 5446940 | 2006-07-29 16:59:06 +0200 | [diff] [blame] | 29 | /* The BF_* macros designate Buffer Flags, which may be ORed in the bit field |
Willy Tarreau | 3da77c5 | 2008-08-29 09:58:42 +0200 | [diff] [blame] | 30 | * member 'flags' in struct buffer. Here we have several types of flags : |
| 31 | * |
| 32 | * - pure status flags, reported by the lower layer, which must be cleared |
| 33 | * before doing further I/O : |
| 34 | * BF_*_NULL, BF_*_PARTIAL |
| 35 | * |
| 36 | * - pure status flags, reported by mid-layer, which must also be cleared |
| 37 | * before doing further I/O : |
| 38 | * BF_*_TIMEOUT, BF_*_ERROR |
| 39 | * |
| 40 | * - read-only indicators reported by lower levels : |
| 41 | * BF_STREAMER, BF_STREAMER_FAST |
| 42 | * |
| 43 | * - write-once status flags reported by the mid-level : BF_SHUTR, BF_SHUTW |
| 44 | * |
| 45 | * - persistent control flags managed only by higher level : |
| 46 | * BF_SHUT*_NOW, BF_*_ENA, BF_HIJACK |
| 47 | * |
| 48 | * The flags have been arranged for readability, so that the read and write |
Willy Tarreau | 418fd47 | 2009-09-06 21:37:23 +0200 | [diff] [blame] | 49 | * bits have the same position in a byte (read being the lower byte and write |
| 50 | * the second one). All flag names are relative to the buffer. For instance, |
| 51 | * 'write' indicates the direction from the buffer to the stream interface. |
Willy Tarreau | 5446940 | 2006-07-29 16:59:06 +0200 | [diff] [blame] | 52 | */ |
Willy Tarreau | e393fe2 | 2008-08-16 22:18:07 +0200 | [diff] [blame] | 53 | |
Willy Tarreau | 3da77c5 | 2008-08-29 09:58:42 +0200 | [diff] [blame] | 54 | #define BF_READ_NULL 0x000001 /* last read detected on producer side */ |
| 55 | #define BF_READ_PARTIAL 0x000002 /* some data were read from producer */ |
| 56 | #define BF_READ_TIMEOUT 0x000004 /* timeout while waiting for producer */ |
| 57 | #define BF_READ_ERROR 0x000008 /* unrecoverable error on producer side */ |
| 58 | #define BF_READ_ACTIVITY (BF_READ_NULL|BF_READ_PARTIAL|BF_READ_ERROR) |
Willy Tarreau | 0f9f505 | 2006-07-29 17:39:25 +0200 | [diff] [blame] | 59 | |
Willy Tarreau | 7c3c541 | 2009-12-13 15:53:05 +0100 | [diff] [blame] | 60 | #define BF_FULL 0x000010 /* buffer cannot accept any more data (l >= max len) */ |
Willy Tarreau | 3da77c5 | 2008-08-29 09:58:42 +0200 | [diff] [blame] | 61 | #define BF_SHUTR 0x000020 /* producer has already shut down */ |
Willy Tarreau | 418fd47 | 2009-09-06 21:37:23 +0200 | [diff] [blame] | 62 | #define BF_SHUTR_NOW 0x000040 /* the producer must shut down for reads ASAP */ |
Willy Tarreau | 86491c3 | 2008-12-14 09:04:47 +0100 | [diff] [blame] | 63 | #define BF_READ_NOEXP 0x000080 /* producer should not expire */ |
Willy Tarreau | 5446940 | 2006-07-29 16:59:06 +0200 | [diff] [blame] | 64 | |
Willy Tarreau | 3da77c5 | 2008-08-29 09:58:42 +0200 | [diff] [blame] | 65 | #define BF_WRITE_NULL 0x000100 /* write(0) or connect() succeeded on consumer side */ |
| 66 | #define BF_WRITE_PARTIAL 0x000200 /* some data were written to the consumer */ |
| 67 | #define BF_WRITE_TIMEOUT 0x000400 /* timeout while waiting for consumer */ |
| 68 | #define BF_WRITE_ERROR 0x000800 /* unrecoverable error on consumer side */ |
| 69 | #define BF_WRITE_ACTIVITY (BF_WRITE_NULL|BF_WRITE_PARTIAL|BF_WRITE_ERROR) |
Willy Tarreau | 5446940 | 2006-07-29 16:59:06 +0200 | [diff] [blame] | 70 | |
Willy Tarreau | ba0b63d | 2009-09-20 08:09:44 +0200 | [diff] [blame] | 71 | #define BF_OUT_EMPTY 0x001000 /* send_max and pipe are empty. Set by last change. */ |
Willy Tarreau | 3da77c5 | 2008-08-29 09:58:42 +0200 | [diff] [blame] | 72 | #define BF_SHUTW 0x002000 /* consumer has already shut down */ |
Willy Tarreau | 418fd47 | 2009-09-06 21:37:23 +0200 | [diff] [blame] | 73 | #define BF_SHUTW_NOW 0x004000 /* the consumer must shut down for writes ASAP */ |
Willy Tarreau | 520d95e | 2009-09-19 21:04:57 +0200 | [diff] [blame] | 74 | #define BF_AUTO_CLOSE 0x008000 /* producer can forward shutdown to other side */ |
Willy Tarreau | 5446940 | 2006-07-29 16:59:06 +0200 | [diff] [blame] | 75 | |
Willy Tarreau | 418fd47 | 2009-09-06 21:37:23 +0200 | [diff] [blame] | 76 | /* When either BF_SHUTR_NOW or BF_HIJACK is set, it is strictly forbidden for |
| 77 | * the producer to alter the buffer contents. When BF_SHUTW_NOW is set, the |
| 78 | * consumer is free to perform a shutw() when it has consumed the last contents, |
| 79 | * otherwise the session processor will do it anyway. |
| 80 | * |
| 81 | * The SHUT* flags work like this : |
| 82 | * |
| 83 | * SHUTR SHUTR_NOW meaning |
| 84 | * 0 0 normal case, connection still open and data is being read |
| 85 | * 0 1 closing : the producer cannot feed data anymore but can close |
| 86 | * 1 0 closed: the producer has closed its input channel. |
| 87 | * 1 1 impossible |
| 88 | * |
| 89 | * SHUTW SHUTW_NOW meaning |
| 90 | * 0 0 normal case, connection still open and data is being written |
| 91 | * 0 1 closing: the consumer can send last data and may then close |
| 92 | * 1 0 closed: the consumer has closed its output channel. |
| 93 | * 1 1 impossible |
| 94 | * |
Willy Tarreau | 520d95e | 2009-09-19 21:04:57 +0200 | [diff] [blame] | 95 | * The SHUTW_NOW flag should be set by the session processor when SHUTR and AUTO_CLOSE |
Willy Tarreau | 418fd47 | 2009-09-06 21:37:23 +0200 | [diff] [blame] | 96 | * are both set. It may also be set by a hijacker at the end of data. And it may also |
| 97 | * be set by the producer when it detects SHUTR while directly forwarding data to the |
| 98 | * consumer. |
| 99 | * |
| 100 | * The SHUTR_NOW flag is mostly used to force the producer to abort when an error is |
| 101 | * detected on the consumer side. |
| 102 | */ |
| 103 | |
Willy Tarreau | 3da77c5 | 2008-08-29 09:58:42 +0200 | [diff] [blame] | 104 | #define BF_STREAMER 0x010000 /* the producer is identified as streaming data */ |
| 105 | #define BF_STREAMER_FAST 0x020000 /* the consumer seems to eat the stream very fast */ |
Willy Tarreau | 0f9f505 | 2006-07-29 17:39:25 +0200 | [diff] [blame] | 106 | |
Willy Tarreau | 01bf867 | 2008-12-07 18:03:29 +0100 | [diff] [blame] | 107 | #define BF_HIJACK 0x040000 /* the producer is temporarily replaced by ->hijacker */ |
Willy Tarreau | 9a2d154 | 2008-08-30 12:31:07 +0200 | [diff] [blame] | 108 | #define BF_ANA_TIMEOUT 0x080000 /* the analyser timeout has expired */ |
| 109 | #define BF_READ_ATTACHED 0x100000 /* the read side is attached for the first time */ |
Willy Tarreau | 259de1b | 2009-01-18 21:56:21 +0100 | [diff] [blame] | 110 | #define BF_KERN_SPLICING 0x200000 /* kernel splicing desired for this buffer */ |
Willy Tarreau | 1b194fe | 2009-03-21 21:10:04 +0100 | [diff] [blame] | 111 | #define BF_READ_DONTWAIT 0x400000 /* wake the task up after every read (eg: HTTP request) */ |
Willy Tarreau | 520d95e | 2009-09-19 21:04:57 +0200 | [diff] [blame] | 112 | #define BF_AUTO_CONNECT 0x800000 /* consumer may attempt to establish a new connection */ |
Willy Tarreau | 9a2d154 | 2008-08-30 12:31:07 +0200 | [diff] [blame] | 113 | |
Willy Tarreau | f1ba4b3 | 2009-10-17 14:37:52 +0200 | [diff] [blame] | 114 | #define BF_DONT_READ 0x1000000 /* disable reading for now */ |
Willy Tarreau | face839 | 2010-01-03 11:37:54 +0100 | [diff] [blame] | 115 | #define BF_EXPECT_MORE 0x2000000 /* more data expected to be sent very soon (one-shoot) */ |
Willy Tarreau | 2be3939 | 2010-01-03 17:24:51 +0100 | [diff] [blame] | 116 | #define BF_SEND_DONTWAIT 0x4000000 /* don't wait for sending data (one-shoot) */ |
Willy Tarreau | f1ba4b3 | 2009-10-17 14:37:52 +0200 | [diff] [blame] | 117 | |
Willy Tarreau | 9a2d154 | 2008-08-30 12:31:07 +0200 | [diff] [blame] | 118 | /* Use these masks to clear the flags before going back to lower layers */ |
| 119 | #define BF_CLEAR_READ (~(BF_READ_NULL|BF_READ_PARTIAL|BF_READ_ERROR|BF_READ_ATTACHED)) |
| 120 | #define BF_CLEAR_WRITE (~(BF_WRITE_NULL|BF_WRITE_PARTIAL|BF_WRITE_ERROR)) |
| 121 | #define BF_CLEAR_TIMEOUT (~(BF_READ_TIMEOUT|BF_WRITE_TIMEOUT|BF_ANA_TIMEOUT)) |
Willy Tarreau | fa7e102 | 2008-10-19 07:30:41 +0200 | [diff] [blame] | 122 | |
Willy Tarreau | fe3718a | 2008-11-30 18:14:12 +0100 | [diff] [blame] | 123 | /* Masks which define input events for stream analysers */ |
Willy Tarreau | 4ffd51a | 2008-08-30 13:36:43 +0200 | [diff] [blame] | 124 | #define BF_MASK_ANALYSER (BF_READ_ATTACHED|BF_READ_ACTIVITY|BF_READ_TIMEOUT|BF_ANA_TIMEOUT|BF_WRITE_ACTIVITY) |
Willy Tarreau | fe3718a | 2008-11-30 18:14:12 +0100 | [diff] [blame] | 125 | |
| 126 | /* Mask for static flags which are not events, but might change during processing */ |
Willy Tarreau | ba0b63d | 2009-09-20 08:09:44 +0200 | [diff] [blame] | 127 | #define BF_MASK_STATIC (BF_OUT_EMPTY|BF_FULL|BF_HIJACK|BF_AUTO_CLOSE|BF_AUTO_CONNECT|BF_SHUTR|BF_SHUTW|BF_SHUTR_NOW|BF_SHUTW_NOW) |
Willy Tarreau | 3da77c5 | 2008-08-29 09:58:42 +0200 | [diff] [blame] | 128 | |
Willy Tarreau | 2df28e8 | 2008-08-17 15:20:19 +0200 | [diff] [blame] | 129 | |
| 130 | /* Analysers (buffer->analysers). |
| 131 | * Those bits indicate that there are some processing to do on the buffer |
Willy Tarreau | 70cb633 | 2008-12-07 11:28:08 +0100 | [diff] [blame] | 132 | * contents. It will probably evolve into a linked list later. Those |
Willy Tarreau | 2df28e8 | 2008-08-17 15:20:19 +0200 | [diff] [blame] | 133 | * analysers could be compared to higher level processors. |
| 134 | * The field is blanked by buffer_init() and only by analysers themselves |
| 135 | * afterwards. |
| 136 | */ |
| 137 | #define AN_REQ_INSPECT 0x00000001 /* inspect request contents */ |
Willy Tarreau | 1d0dfb1 | 2009-07-07 15:10:31 +0200 | [diff] [blame] | 138 | #define AN_REQ_WAIT_HTTP 0x00000002 /* wait for an HTTP request */ |
| 139 | #define AN_REQ_HTTP_PROCESS_FE 0x00000004 /* process the frontend's HTTP part */ |
| 140 | #define AN_REQ_SWITCHING_RULES 0x00000008 /* apply the switching rules */ |
| 141 | #define AN_REQ_HTTP_PROCESS_BE 0x00000010 /* process the backend's HTTP part */ |
| 142 | #define AN_REQ_HTTP_INNER 0x00000020 /* inner processing of HTTP request */ |
| 143 | #define AN_REQ_HTTP_TARPIT 0x00000040 /* wait for end of HTTP tarpit */ |
| 144 | #define AN_REQ_HTTP_BODY 0x00000080 /* inspect HTTP request body */ |
Emeric Brun | 1d33b29 | 2010-01-04 15:47:17 +0100 | [diff] [blame] | 145 | #define AN_REQ_STICKING_RULES 0x00000100 /* table persistence matching */ |
| 146 | /* unused: 0x200 */ |
Emeric Brun | 647caf1 | 2009-06-30 17:57:00 +0200 | [diff] [blame] | 147 | #define AN_REQ_PRST_RDP_COOKIE 0x00000400 /* persistence on rdp cookie */ |
Willy Tarreau | d98cf93 | 2009-12-27 22:54:55 +0100 | [diff] [blame] | 148 | #define AN_REQ_HTTP_XFER_BODY 0x00000800 /* forward request body */ |
Willy Tarreau | 2df28e8 | 2008-08-17 15:20:19 +0200 | [diff] [blame] | 149 | |
Willy Tarreau | b37c27e | 2009-10-18 22:53:08 +0200 | [diff] [blame] | 150 | /* response analysers */ |
| 151 | #define AN_RES_INSPECT 0x00010000 /* content inspection */ |
| 152 | #define AN_RES_WAIT_HTTP 0x00020000 /* wait for HTTP response */ |
| 153 | #define AN_RES_HTTP_PROCESS_BE 0x00040000 /* process backend's HTTP part */ |
| 154 | #define AN_RES_HTTP_PROCESS_FE 0x00040000 /* process frontend's HTTP part (same for now) */ |
Emeric Brun | 1d33b29 | 2010-01-04 15:47:17 +0100 | [diff] [blame] | 155 | #define AN_RES_STORE_RULES 0x00080000 /* table persistence matching */ |
Willy Tarreau | d98cf93 | 2009-12-27 22:54:55 +0100 | [diff] [blame] | 156 | #define AN_RES_HTTP_XFER_BODY 0x00100000 /* forward response body */ |
Willy Tarreau | b37c27e | 2009-10-18 22:53:08 +0200 | [diff] [blame] | 157 | |
| 158 | |
Willy Tarreau | 31971e5 | 2009-09-20 12:07:52 +0200 | [diff] [blame] | 159 | /* Magic value to forward infinite size (TCP, ...), used with ->to_forward */ |
| 160 | #define BUF_INFINITE_FORWARD (~0UL) |
| 161 | |
Willy Tarreau | baaee00 | 2006-06-26 02:48:02 +0200 | [diff] [blame] | 162 | /* describes a chunk of string */ |
| 163 | struct chunk { |
| 164 | char *str; /* beginning of the string itself. Might not be 0-terminated */ |
Krzysztof Piotr Oledzki | 78abe61 | 2009-09-27 13:23:20 +0200 | [diff] [blame] | 165 | size_t size; /* total size of the buffer, 0 if the *str is read-only */ |
Krzysztof Piotr Oledzki | 6f61b21 | 2009-10-04 23:34:15 +0200 | [diff] [blame] | 166 | int len; /* current size of the string from first to last char. <0 = uninit. */ |
Willy Tarreau | baaee00 | 2006-06-26 02:48:02 +0200 | [diff] [blame] | 167 | }; |
| 168 | |
Willy Tarreau | 01bf867 | 2008-12-07 18:03:29 +0100 | [diff] [blame] | 169 | /* needed for a declaration below */ |
| 170 | struct session; |
| 171 | |
Willy Tarreau | baaee00 | 2006-06-26 02:48:02 +0200 | [diff] [blame] | 172 | struct buffer { |
Willy Tarreau | aad2e49 | 2006-10-15 23:32:18 +0200 | [diff] [blame] | 173 | unsigned int flags; /* BF_* */ |
Willy Tarreau | 0c303ee | 2008-07-07 00:09:58 +0200 | [diff] [blame] | 174 | int rex; /* expiration date for a read, in ticks */ |
Willy Tarreau | 26ed74d | 2008-08-17 12:11:14 +0200 | [diff] [blame] | 175 | int wex; /* expiration date for a write or connect, in ticks */ |
Willy Tarreau | 0c303ee | 2008-07-07 00:09:58 +0200 | [diff] [blame] | 176 | int rto; /* read timeout, in ticks */ |
| 177 | int wto; /* write timeout, in ticks */ |
| 178 | int cto; /* connect timeout, in ticks */ |
Willy Tarreau | baaee00 | 2006-06-26 02:48:02 +0200 | [diff] [blame] | 179 | unsigned int l; /* data length */ |
Willy Tarreau | e09e0ce | 2007-03-18 16:31:29 +0100 | [diff] [blame] | 180 | char *r, *w, *lr; /* read ptr, write ptr, last read */ |
Willy Tarreau | a07a34e | 2009-08-16 23:27:46 +0200 | [diff] [blame] | 181 | unsigned int size; /* buffer size in bytes */ |
Willy Tarreau | 0abebcc | 2009-01-08 00:09:41 +0100 | [diff] [blame] | 182 | unsigned int send_max; /* number of bytes the sender can consume om this buffer, <= l */ |
Willy Tarreau | 31971e5 | 2009-09-20 12:07:52 +0200 | [diff] [blame] | 183 | unsigned long to_forward; /* number of bytes to forward after send_max without a wake-up */ |
Willy Tarreau | 2df28e8 | 2008-08-17 15:20:19 +0200 | [diff] [blame] | 184 | unsigned int analysers; /* bit field indicating what to do on the buffer */ |
Willy Tarreau | ffab5b4 | 2008-08-17 18:03:28 +0200 | [diff] [blame] | 185 | int analyse_exp; /* expiration date for current analysers (if set) */ |
Willy Tarreau | 01bf867 | 2008-12-07 18:03:29 +0100 | [diff] [blame] | 186 | void (*hijacker)(struct session *, struct buffer *); /* alternative content producer */ |
Willy Tarreau | 8a7af60 | 2008-05-03 23:07:14 +0200 | [diff] [blame] | 187 | unsigned char xfer_large; /* number of consecutive large xfers */ |
| 188 | unsigned char xfer_small; /* number of consecutive small xfers */ |
Willy Tarreau | baaee00 | 2006-06-26 02:48:02 +0200 | [diff] [blame] | 189 | unsigned long long total; /* total data read */ |
Willy Tarreau | fa7e102 | 2008-10-19 07:30:41 +0200 | [diff] [blame] | 190 | struct stream_interface *prod; /* producer attached to this buffer */ |
| 191 | struct stream_interface *cons; /* consumer attached to this buffer */ |
Willy Tarreau | 3eba98a | 2009-01-25 13:56:13 +0100 | [diff] [blame] | 192 | struct pipe *pipe; /* non-NULL only when data present */ |
Willy Tarreau | a07a34e | 2009-08-16 23:27:46 +0200 | [diff] [blame] | 193 | char data[0]; /* <size> bytes */ |
Willy Tarreau | baaee00 | 2006-06-26 02:48:02 +0200 | [diff] [blame] | 194 | }; |
| 195 | |
Willy Tarreau | baaee00 | 2006-06-26 02:48:02 +0200 | [diff] [blame] | 196 | |
Willy Tarreau | 0abebcc | 2009-01-08 00:09:41 +0100 | [diff] [blame] | 197 | /* Note about the buffer structure |
| 198 | |
| 199 | The buffer contains two length indicators, one to_forward counter and one |
| 200 | send_max limit. First, it must be understood that the buffer is in fact |
| 201 | split in two parts : |
| 202 | - the visible data (->data, for ->l bytes) |
| 203 | - the invisible data, typically in kernel buffers forwarded directly from |
Willy Tarreau | 3eba98a | 2009-01-25 13:56:13 +0100 | [diff] [blame] | 204 | the source stream sock to the destination stream sock (->pipe->data |
Willy Tarreau | 0abebcc | 2009-01-08 00:09:41 +0100 | [diff] [blame] | 205 | bytes). Those are used only during forward. |
| 206 | |
| 207 | In order not to mix data streams, the producer may only feed the invisible |
| 208 | data with data to forward, and only when the visible buffer is empty. The |
| 209 | consumer may not always be able to feed the invisible buffer due to platform |
| 210 | limitations (lack of kernel support). |
| 211 | |
| 212 | Conversely, the consumer must always take data from the invisible data first |
| 213 | before ever considering visible data. There is no limit to the size of data |
| 214 | to consume from the invisible buffer, as platform-specific implementations |
| 215 | will rarely leave enough control on this. So any byte fed into the invisible |
| 216 | buffer is expected to reach the destination file descriptor, by any means. |
| 217 | However, it's the consumer's responsibility to ensure that the invisible |
| 218 | data has been entirely consumed before consuming visible data. This must be |
Willy Tarreau | 3eba98a | 2009-01-25 13:56:13 +0100 | [diff] [blame] | 219 | reflected by ->pipe->data. This is very important as this and only this can |
Willy Tarreau | 0abebcc | 2009-01-08 00:09:41 +0100 | [diff] [blame] | 220 | ensure strict ordering of data between buffers. |
| 221 | |
| 222 | The producer is responsible for decreasing ->to_forward and increasing |
| 223 | ->send_max. The ->to_forward parameter indicates how many bytes may be fed |
Willy Tarreau | 31971e5 | 2009-09-20 12:07:52 +0200 | [diff] [blame] | 224 | into either data buffer without waking the parent up. The special value |
| 225 | BUF_INFINITE_FORWARD is never decreased nor increased. The ->send_max |
Willy Tarreau | 0abebcc | 2009-01-08 00:09:41 +0100 | [diff] [blame] | 226 | parameter says how many bytes may be read from the visible buffer. Thus it |
| 227 | may never exceed ->l. This parameter is updated by any buffer_write() as |
| 228 | well as any data forwarded through the visible buffer. |
| 229 | |
| 230 | The consumer is responsible for decreasing ->send_max when it sends data |
Willy Tarreau | 3eba98a | 2009-01-25 13:56:13 +0100 | [diff] [blame] | 231 | from the visible buffer, and ->pipe->data when it sends data from the |
Willy Tarreau | 0abebcc | 2009-01-08 00:09:41 +0100 | [diff] [blame] | 232 | invisible buffer. |
| 233 | |
| 234 | A real-world example consists in part in an HTTP response waiting in a |
| 235 | buffer to be forwarded. We know the header length (300) and the amount of |
| 236 | data to forward (content-length=9000). The buffer already contains 1000 |
| 237 | bytes of data after the 300 bytes of headers. Thus the caller will set |
| 238 | ->send_max to 300 indicating that it explicitly wants to send those data, |
| 239 | and set ->to_forward to 9000 (content-length). This value must be normalised |
| 240 | immediately after updating ->to_forward : since there are already 1300 bytes |
| 241 | in the buffer, 300 of which are already counted in ->send_max, and that size |
| 242 | is smaller than ->to_forward, we must update ->send_max to 1300 to flush the |
| 243 | whole buffer, and reduce ->to_forward to 8000. After that, the producer may |
| 244 | try to feed the additional data through the invisible buffer using a |
| 245 | platform-specific method such as splice(). |
Willy Tarreau | 7c3c541 | 2009-12-13 15:53:05 +0100 | [diff] [blame] | 246 | |
| 247 | The ->to_forward entry is also used to detect whether we can fill the buffer |
| 248 | or not. The idea is that we need to save some space for data manipulation |
| 249 | (mainly header rewriting in HTTP) so we don't want to have a full buffer on |
| 250 | input before processing a request or response. Thus, we ensure that there is |
| 251 | always global.maxrewrite bytes of free space. Since we don't want to forward |
| 252 | chunks without filling the buffer, we rely on ->to_forward. When ->to_forward |
| 253 | is null, we may have some processing to do so we don't want to fill the |
| 254 | buffer. When ->to_forward is non-null, we know we don't care for at least as |
| 255 | many bytes. In the end, we know that each of the ->to_forward bytes will |
| 256 | eventually leave the buffer. So as long as ->to_forward is larger than |
| 257 | global.maxrewrite, we can fill the buffer. If ->to_forward is smaller than |
| 258 | global.maxrewrite, then we don't want to fill the buffer with more than |
| 259 | ->size - global.maxrewrite + ->to_forward. |
| 260 | |
| 261 | Note that this also means that anyone touching ->to_forward must also take |
| 262 | care of updating the BF_FULL flag. For this reason, it's really advised to |
| 263 | use buffer_forward() only. |
Willy Tarreau | 0abebcc | 2009-01-08 00:09:41 +0100 | [diff] [blame] | 264 | */ |
| 265 | |
Willy Tarreau | baaee00 | 2006-06-26 02:48:02 +0200 | [diff] [blame] | 266 | #endif /* _TYPES_BUFFERS_H */ |
| 267 | |
| 268 | /* |
| 269 | * Local variables: |
| 270 | * c-indent-level: 8 |
| 271 | * c-basic-offset: 8 |
| 272 | * End: |
| 273 | */ |