| 1 | .\" Automatically generated by Pod::Man 2.25 (Pod::Simple 3.19) |
| 2 | .\" |
| 3 | .\" Standard preamble: |
| 4 | .\" ======================================================================== |
| 5 | .de Sp \" Vertical space (when we can't use .PP) |
| 6 | .if t .sp .5v |
| 7 | .if n .sp |
| 8 | .. |
| 9 | .de Vb \" Begin verbatim text |
| 10 | .ft CW |
| 11 | .nf |
| 12 | .ne \\$1 |
| 13 | .. |
| 14 | .de Ve \" End verbatim text |
| 15 | .ft R |
| 16 | .fi |
| 17 | .. |
| 18 | .\" Set up some character translations and predefined strings. \*(-- will |
| 19 | .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left |
| 20 | .\" double quote, and \*(R" will give a right double quote. \*(C+ will |
| 21 | .\" give a nicer C++. Capital omega is used to do unbreakable dashes and |
| 22 | .\" therefore won't be available. \*(C` and \*(C' expand to `' in nroff, |
| 23 | .\" nothing in troff, for use with C<>. |
| 24 | .tr \(*W- |
| 25 | .ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' |
| 26 | .ie n \{\ |
| 27 | . ds -- \(*W- |
| 28 | . ds PI pi |
| 29 | . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch |
| 30 | . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch |
| 31 | . ds L" "" |
| 32 | . ds R" "" |
| 33 | . ds C` "" |
| 34 | . ds C' "" |
| 35 | 'br\} |
| 36 | .el\{\ |
| 37 | . ds -- \|\(em\| |
| 38 | . ds PI \(*p |
| 39 | . ds L" `` |
| 40 | . ds R" '' |
| 41 | 'br\} |
| 42 | .\" |
| 43 | .\" Escape single quotes in literal strings from groff's Unicode transform. |
| 44 | .ie \n(.g .ds Aq \(aq |
| 45 | .el .ds Aq ' |
| 46 | .\" |
| 47 | .\" If the F register is turned on, we'll generate index entries on stderr for |
| 48 | .\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index |
| 49 | .\" entries marked with X<> in POD. Of course, you'll have to process the |
| 50 | .\" output yourself in some meaningful fashion. |
| 51 | .ie \nF \{\ |
| 52 | . de IX |
| 53 | . tm Index:\\$1\t\\n%\t"\\$2" |
| 54 | .. |
| 55 | . nr % 0 |
| 56 | . rr F |
| 57 | .\} |
| 58 | .el \{\ |
| 59 | . de IX |
| 60 | .. |
| 61 | .\} |
| 62 | .\" |
| 63 | .\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2). |
| 64 | .\" Fear. Run. Save yourself. No user-serviceable parts. |
| 65 | . \" fudge factors for nroff and troff |
| 66 | .if n \{\ |
| 67 | . ds #H 0 |
| 68 | . ds #V .8m |
| 69 | . ds #F .3m |
| 70 | . ds #[ \f1 |
| 71 | . ds #] \fP |
| 72 | .\} |
| 73 | .if t \{\ |
| 74 | . ds #H ((1u-(\\\\n(.fu%2u))*.13m) |
| 75 | . ds #V .6m |
| 76 | . ds #F 0 |
| 77 | . ds #[ \& |
| 78 | . ds #] \& |
| 79 | .\} |
| 80 | . \" simple accents for nroff and troff |
| 81 | .if n \{\ |
| 82 | . ds ' \& |
| 83 | . ds ` \& |
| 84 | . ds ^ \& |
| 85 | . ds , \& |
| 86 | . ds ~ ~ |
| 87 | . ds / |
| 88 | .\} |
| 89 | .if t \{\ |
| 90 | . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" |
| 91 | . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' |
| 92 | . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' |
| 93 | . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' |
| 94 | . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' |
| 95 | . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' |
| 96 | .\} |
| 97 | . \" troff and (daisy-wheel) nroff accents |
| 98 | .ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V' |
| 99 | .ds 8 \h'\*(#H'\(*b\h'-\*(#H' |
| 100 | .ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#] |
| 101 | .ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H' |
| 102 | .ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u' |
| 103 | .ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#] |
| 104 | .ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#] |
| 105 | .ds ae a\h'-(\w'a'u*4/10)'e |
| 106 | .ds Ae A\h'-(\w'A'u*4/10)'E |
| 107 | . \" corrections for vroff |
| 108 | .if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u' |
| 109 | .if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u' |
| 110 | . \" for low resolution devices (crt and lpr) |
| 111 | .if \n(.H>23 .if \n(.V>19 \ |
| 112 | \{\ |
| 113 | . ds : e |
| 114 | . ds 8 ss |
| 115 | . ds o a |
| 116 | . ds d- d\h'-1'\(ga |
| 117 | . ds D- D\h'-1'\(hy |
| 118 | . ds th \o'bp' |
| 119 | . ds Th \o'LP' |
| 120 | . ds ae ae |
| 121 | . ds Ae AE |
| 122 | .\} |
| 123 | .rm #[ #] #H #V #F C |
| 124 | .\" ======================================================================== |
| 125 | .\" |
| 126 | .IX Title "BIO_s_bio 3" |
| 127 | .TH BIO_s_bio 3 "2012-01-04" "1.0.0f" "OpenSSL" |
| 128 | .\" For nroff, turn off justification. Always turn off hyphenation; it makes |
| 129 | .\" way too many mistakes in technical documents. |
| 130 | .if n .ad l |
| 131 | .nh |
| 132 | .SH "NAME" |
| 133 | BIO_s_bio, BIO_make_bio_pair, BIO_destroy_bio_pair, BIO_shutdown_wr, |
| 134 | BIO_set_write_buf_size, BIO_get_write_buf_size, BIO_new_bio_pair, |
| 135 | BIO_get_write_guarantee, BIO_ctrl_get_write_guarantee, BIO_get_read_request, |
| 136 | BIO_ctrl_get_read_request, BIO_ctrl_reset_read_request \- BIO pair BIO |
| 137 | .SH "SYNOPSIS" |
| 138 | .IX Header "SYNOPSIS" |
| 139 | .Vb 1 |
| 140 | \& #include <openssl/bio.h> |
| 141 | \& |
| 142 | \& BIO_METHOD *BIO_s_bio(void); |
| 143 | \& |
| 144 | \& #define BIO_make_bio_pair(b1,b2) (int)BIO_ctrl(b1,BIO_C_MAKE_BIO_PAIR,0,b2) |
| 145 | \& #define BIO_destroy_bio_pair(b) (int)BIO_ctrl(b,BIO_C_DESTROY_BIO_PAIR,0,NULL) |
| 146 | \& |
| 147 | \& #define BIO_shutdown_wr(b) (int)BIO_ctrl(b, BIO_C_SHUTDOWN_WR, 0, NULL) |
| 148 | \& |
| 149 | \& #define BIO_set_write_buf_size(b,size) (int)BIO_ctrl(b,BIO_C_SET_WRITE_BUF_SIZE,size,NULL) |
| 150 | \& #define BIO_get_write_buf_size(b,size) (size_t)BIO_ctrl(b,BIO_C_GET_WRITE_BUF_SIZE,size,NULL) |
| 151 | \& |
| 152 | \& int BIO_new_bio_pair(BIO **bio1, size_t writebuf1, BIO **bio2, size_t writebuf2); |
| 153 | \& |
| 154 | \& #define BIO_get_write_guarantee(b) (int)BIO_ctrl(b,BIO_C_GET_WRITE_GUARANTEE,0,NULL) |
| 155 | \& size_t BIO_ctrl_get_write_guarantee(BIO *b); |
| 156 | \& |
| 157 | \& #define BIO_get_read_request(b) (int)BIO_ctrl(b,BIO_C_GET_READ_REQUEST,0,NULL) |
| 158 | \& size_t BIO_ctrl_get_read_request(BIO *b); |
| 159 | \& |
| 160 | \& int BIO_ctrl_reset_read_request(BIO *b); |
| 161 | .Ve |
| 162 | .SH "DESCRIPTION" |
| 163 | .IX Header "DESCRIPTION" |
| 164 | \&\fIBIO_s_bio()\fR returns the method for a \s-1BIO\s0 pair. A \s-1BIO\s0 pair is a pair of source/sink |
| 165 | BIOs where data written to either half of the pair is buffered and can be read from |
| 166 | the other half. Both halves must usually by handled by the same application thread |
| 167 | since no locking is done on the internal data structures. |
| 168 | .PP |
| 169 | Since \s-1BIO\s0 chains typically end in a source/sink \s-1BIO\s0 it is possible to make this |
| 170 | one half of a \s-1BIO\s0 pair and have all the data processed by the chain under application |
| 171 | control. |
| 172 | .PP |
| 173 | One typical use of \s-1BIO\s0 pairs is to place \s-1TLS/SSL\s0 I/O under application control, this |
| 174 | can be used when the application wishes to use a non standard transport for |
| 175 | \&\s-1TLS/SSL\s0 or the normal socket routines are inappropriate. |
| 176 | .PP |
| 177 | Calls to \fIBIO_read()\fR will read data from the buffer or request a retry if no |
| 178 | data is available. |
| 179 | .PP |
| 180 | Calls to \fIBIO_write()\fR will place data in the buffer or request a retry if the |
| 181 | buffer is full. |
| 182 | .PP |
| 183 | The standard calls \fIBIO_ctrl_pending()\fR and \fIBIO_ctrl_wpending()\fR can be used to |
| 184 | determine the amount of pending data in the read or write buffer. |
| 185 | .PP |
| 186 | \&\fIBIO_reset()\fR clears any data in the write buffer. |
| 187 | .PP |
| 188 | \&\fIBIO_make_bio_pair()\fR joins two separate BIOs into a connected pair. |
| 189 | .PP |
| 190 | \&\fIBIO_destroy_pair()\fR destroys the association between two connected BIOs. Freeing |
| 191 | up any half of the pair will automatically destroy the association. |
| 192 | .PP |
| 193 | \&\fIBIO_shutdown_wr()\fR is used to close down a \s-1BIO\s0 \fBb\fR. After this call no further |
| 194 | writes on \s-1BIO\s0 \fBb\fR are allowed (they will return an error). Reads on the other |
| 195 | half of the pair will return any pending data or \s-1EOF\s0 when all pending data has |
| 196 | been read. |
| 197 | .PP |
| 198 | \&\fIBIO_set_write_buf_size()\fR sets the write buffer size of \s-1BIO\s0 \fBb\fR to \fBsize\fR. |
| 199 | If the size is not initialized a default value is used. This is currently |
| 200 | 17K, sufficient for a maximum size \s-1TLS\s0 record. |
| 201 | .PP |
| 202 | \&\fIBIO_get_write_buf_size()\fR returns the size of the write buffer. |
| 203 | .PP |
| 204 | \&\fIBIO_new_bio_pair()\fR combines the calls to \fIBIO_new()\fR, \fIBIO_make_bio_pair()\fR and |
| 205 | \&\fIBIO_set_write_buf_size()\fR to create a connected pair of BIOs \fBbio1\fR, \fBbio2\fR |
| 206 | with write buffer sizes \fBwritebuf1\fR and \fBwritebuf2\fR. If either size is |
| 207 | zero then the default size is used. \fIBIO_new_bio_pair()\fR does not check whether |
| 208 | \&\fBbio1\fR or \fBbio2\fR do point to some other \s-1BIO\s0, the values are overwritten, |
| 209 | \&\fIBIO_free()\fR is not called. |
| 210 | .PP |
| 211 | \&\fIBIO_get_write_guarantee()\fR and \fIBIO_ctrl_get_write_guarantee()\fR return the maximum |
| 212 | length of data that can be currently written to the \s-1BIO\s0. Writes larger than this |
| 213 | value will return a value from \fIBIO_write()\fR less than the amount requested or if the |
| 214 | buffer is full request a retry. \fIBIO_ctrl_get_write_guarantee()\fR is a function |
| 215 | whereas \fIBIO_get_write_guarantee()\fR is a macro. |
| 216 | .PP |
| 217 | \&\fIBIO_get_read_request()\fR and \fIBIO_ctrl_get_read_request()\fR return the |
| 218 | amount of data requested, or the buffer size if it is less, if the |
| 219 | last read attempt at the other half of the \s-1BIO\s0 pair failed due to an |
| 220 | empty buffer. This can be used to determine how much data should be |
| 221 | written to the \s-1BIO\s0 so the next read will succeed: this is most useful |
| 222 | in \s-1TLS/SSL\s0 applications where the amount of data read is usually |
| 223 | meaningful rather than just a buffer size. After a successful read |
| 224 | this call will return zero. It also will return zero once new data |
| 225 | has been written satisfying the read request or part of it. |
| 226 | Note that \fIBIO_get_read_request()\fR never returns an amount larger |
| 227 | than that returned by \fIBIO_get_write_guarantee()\fR. |
| 228 | .PP |
| 229 | \&\fIBIO_ctrl_reset_read_request()\fR can also be used to reset the value returned by |
| 230 | \&\fIBIO_get_read_request()\fR to zero. |
| 231 | .SH "NOTES" |
| 232 | .IX Header "NOTES" |
| 233 | Both halves of a \s-1BIO\s0 pair should be freed. That is even if one half is implicit |
| 234 | freed due to a \fIBIO_free_all()\fR or \fISSL_free()\fR call the other half needs to be freed. |
| 235 | .PP |
| 236 | When used in bidirectional applications (such as \s-1TLS/SSL\s0) care should be taken to |
| 237 | flush any data in the write buffer. This can be done by calling \fIBIO_pending()\fR |
| 238 | on the other half of the pair and, if any data is pending, reading it and sending |
| 239 | it to the underlying transport. This must be done before any normal processing |
| 240 | (such as calling \fIselect()\fR ) due to a request and \fIBIO_should_read()\fR being true. |
| 241 | .PP |
| 242 | To see why this is important consider a case where a request is sent using |
| 243 | \&\fIBIO_write()\fR and a response read with \fIBIO_read()\fR, this can occur during an |
| 244 | \&\s-1TLS/SSL\s0 handshake for example. \fIBIO_write()\fR will succeed and place data in the write |
| 245 | buffer. \fIBIO_read()\fR will initially fail and \fIBIO_should_read()\fR will be true. If |
| 246 | the application then waits for data to be available on the underlying transport |
| 247 | before flushing the write buffer it will never succeed because the request was |
| 248 | never sent! |
| 249 | .SH "RETURN VALUES" |
| 250 | .IX Header "RETURN VALUES" |
| 251 | \&\fIBIO_new_bio_pair()\fR returns 1 on success, with the new BIOs available in |
| 252 | \&\fBbio1\fR and \fBbio2\fR, or 0 on failure, with \s-1NULL\s0 pointers stored into the |
| 253 | locations for \fBbio1\fR and \fBbio2\fR. Check the error stack for more information. |
| 254 | .PP |
| 255 | [\s-1XXXXX:\s0 More return values need to be added here] |
| 256 | .SH "EXAMPLE" |
| 257 | .IX Header "EXAMPLE" |
| 258 | The \s-1BIO\s0 pair can be used to have full control over the network access of an |
| 259 | application. The application can call \fIselect()\fR on the socket as required |
| 260 | without having to go through the SSL-interface. |
| 261 | .PP |
| 262 | .Vb 6 |
| 263 | \& BIO *internal_bio, *network_bio; |
| 264 | \& ... |
| 265 | \& BIO_new_bio_pair(internal_bio, 0, network_bio, 0); |
| 266 | \& SSL_set_bio(ssl, internal_bio, internal_bio); |
| 267 | \& SSL_operations(); |
| 268 | \& ... |
| 269 | \& |
| 270 | \& application | TLS\-engine |
| 271 | \& | | |
| 272 | \& +\-\-\-\-\-\-\-\-\-\-> SSL_operations() |
| 273 | \& | /\e || |
| 274 | \& | || \e/ |
| 275 | \& | BIO\-pair (internal_bio) |
| 276 | \& +\-\-\-\-\-\-\-\-\-\-< BIO\-pair (network_bio) |
| 277 | \& | | |
| 278 | \& socket | |
| 279 | \& |
| 280 | \& ... |
| 281 | \& SSL_free(ssl); /* implicitly frees internal_bio */ |
| 282 | \& BIO_free(network_bio); |
| 283 | \& ... |
| 284 | .Ve |
| 285 | .PP |
| 286 | As the \s-1BIO\s0 pair will only buffer the data and never directly access the |
| 287 | connection, it behaves non-blocking and will return as soon as the write |
| 288 | buffer is full or the read buffer is drained. Then the application has to |
| 289 | flush the write buffer and/or fill the read buffer. |
| 290 | .PP |
| 291 | Use the \fIBIO_ctrl_pending()\fR, to find out whether data is buffered in the \s-1BIO\s0 |
| 292 | and must be transfered to the network. Use \fIBIO_ctrl_get_read_request()\fR to |
| 293 | find out, how many bytes must be written into the buffer before the |
| 294 | \&\fISSL_operation()\fR can successfully be continued. |
| 295 | .SH "WARNING" |
| 296 | .IX Header "WARNING" |
| 297 | As the data is buffered, \fISSL_operation()\fR may return with a \s-1ERROR_SSL_WANT_READ\s0 |
| 298 | condition, but there is still data in the write buffer. An application must |
| 299 | not rely on the error value of \fISSL_operation()\fR but must assure that the |
| 300 | write buffer is always flushed first. Otherwise a deadlock may occur as |
| 301 | the peer might be waiting for the data before being able to continue. |
| 302 | .SH "SEE ALSO" |
| 303 | .IX Header "SEE ALSO" |
| 304 | \&\fISSL_set_bio\fR\|(3), \fIssl\fR\|(3), \fIbio\fR\|(3), |
| 305 | \&\fIBIO_should_retry\fR\|(3), \fIBIO_read\fR\|(3) |