Add a number of documentation files, mostly for SSL routines, but also

for a few BIO routines.
Submitted by Lutz Jaenicke <Lutz.Jaenicke@aet.TU-Cottbus.DE>

1 files changed, 102 insertions, 0 deletions

diff --git a/doc/crypto/BIO_new_bio_pair.pod b/doc/crypto/BIO_new_bio_pair.pod
new file mode 100644
index 0000000000..c331bd02b8
--- /dev/null
+++ b/doc/crypto/BIO_new_bio_pair.pod
@@ -0,0 +1,102 @@
+=pod
+
+=head1 NAME
+
+BIO_new_bio_pair - create a new BIO pair
+
+=head1 SYNOPSIS
+
+ #include <openssl/bio.h>
+
+ int BIO_new_bio_pair(BIO **bio1, size_t writebuf1, BIO **bio2, size_t writebuf2);
+
+=head1 DESCRIPTION
+
+BIO_new_bio_pair() creates a buffering BIO pair. It has two endpoints between
+data can be buffered. Its typical use is to connect one endpoint as underlying
+input/output BIO to an SSL and access the other one controlled by the program
+instead of accessing the network connection directly.
+
+The two new BIOs B<bio1> and B<bio2> are symmetric with respect to their
+functionality. The size of their buffers is determined by B<writebuf1> and
+B<writebuf2>. If the size give is 0, the default size is used.
+
+BIO_new_bio_pair() does not check whether B<bio1> or B<bio2> do point to
+some other BIO, the values are overwritten, BIO_free() is not called.
+
+The two BIOs, even though forming a BIO pair and must be BIO_free()'ed
+seperately. This can be of importance, as some SSL-functions like SSL_set_bio()
+or SSL_free() call BIO_free() implicitely, so that the peer-BIO is left
+untouched and must also be BIO_free()'ed.
+
+=head1 EXAMPLE
+
+The BIO pair can be used to have full control over the network access of an
+application. The application can call select() on the socket as required
+without having to go through the SSL-interface.
+
+ BIO *internal_bio, *network_bio;
+ ...
+ BIO_new_bio_pair(internal_bio, 0, network_bio, 0);
+ SSL_set_bio(ssl, internal_bio);
+ SSL_operations();
+ ...
+
+ application |   TLS-engine
+    |        |
+    +----------> SSL_operations()
+             |     /\    ||
+             |     ||    \/
+             |   BIO-pair (internal_bio)
+    +----------< BIO-pair (network_bio)
+    |        |
+  socket     |
+
+  ...
+  SSL_free(ssl);		/* implicitely frees internal_bio */
+  BIO_free(network_bio);
+  ...
+
+As the BIO pair will only buffer the data and never directly access the
+connection, it behaves non-blocking and will return as soon as the write
+buffer is full or the read buffer is drained. Then the application has to
+flush the write buffer and/or fill the read buffer.
+
+Use the BIO_ctrl_pending(), to find out whether data is buffered in the BIO
+and must be transfered to the network. Use BIO_ctrl_get_read_request() to
+find out, how many bytes must be written into the buffer before the
+SSL_operation() can successfully be continued.
+
+=head1 IMPORTANT
+
+As the data is buffered, SSL_operation() may return with a ERROR_SSL_WANT_READ
+condition, but there is still data in the write buffer. An application must
+not rely on the error value of SSL_operation() but must assure that the
+write buffer is always flushed first. Otherwise a deadlock may occur as
+the peer might be waiting for the data before being able to continue.
+
+=head1 RETURN VALUES
+
+The following return values can occur:
+
+=over 4
+
+=item 1
+
+The BIO pair was created successfully. The new BIOs are available in
+B<bio1> and B<bio2>.
+
+=item 0
+
+The operation failed. The NULL pointer is stored into the locations for
+B<bio1> and B<bio2>. Check the error stack for more information.
+
+=back
+
+=head1 SEE ALSO
+
+L<SSL_set_bio(3)|SSL_set_bio(3)>, L<ssl(3)|ssl(3)>, L<bio(3)|bio(3)>,
+L<BIO_ctrl_pending(3)|BIO_ctrl_pending(3)>,
+L<BIO_ctrl_get_read_request(3)|BIO_ctrl_get_read_request(3)>
+
+=cut