Documentation for BIO flags and related functions.

Reviewed-by: Frederik Wedel-Heinen <fwh.openssl@gmail.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/29311)

(cherry picked from commit e12870deb0)

doc/build.info

@@ -691,6 +691,10 @@ DEPEND[html/man3/BIO_set_callback.html]=man3/BIO_set_callback.pod
 GENERATE[html/man3/BIO_set_callback.html]=man3/BIO_set_callback.pod
 DEPEND[man/man3/BIO_set_callback.3]=man3/BIO_set_callback.pod
 GENERATE[man/man3/BIO_set_callback.3]=man3/BIO_set_callback.pod
+DEPEND[html/man3/BIO_set_flags.html]=man3/BIO_set_flags.pod
+GENERATE[html/man3/BIO_set_flags.html]=man3/BIO_set_flags.pod
+DEPEND[man/man3/BIO_set_flags.3]=man3/BIO_set_flags.pod
+GENERATE[man/man3/BIO_set_flags.3]=man3/BIO_set_flags.pod
 DEPEND[html/man3/BIO_should_retry.html]=man3/BIO_should_retry.pod
 GENERATE[html/man3/BIO_should_retry.html]=man3/BIO_should_retry.pod
 DEPEND[man/man3/BIO_should_retry.3]=man3/BIO_should_retry.pod
@@ -3112,6 +3116,7 @@ html/man3/BIO_s_null.html \
 html/man3/BIO_s_socket.html \
 html/man3/BIO_sendmmsg.html \
 html/man3/BIO_set_callback.html \
+html/man3/BIO_set_flags.html \
 html/man3/BIO_should_retry.html \
 html/man3/BIO_socket_wait.html \
 html/man3/BN_BLINDING_new.html \
@@ -3759,6 +3764,7 @@ man/man3/BIO_s_null.3 \
 man/man3/BIO_s_socket.3 \
 man/man3/BIO_sendmmsg.3 \
 man/man3/BIO_set_callback.3 \
+man/man3/BIO_set_flags.3 \
 man/man3/BIO_should_retry.3 \
 man/man3/BIO_socket_wait.3 \
 man/man3/BN_BLINDING_new.3 \

doc/man3/BIO_set_flags.pod

@@ -0,0 +1,194 @@
+=pod
+
+=head1 NAME
+
+BIO_set_flags, BIO_clear_flags, BIO_test_flags, BIO_get_flags,
+BIO_set_retry_read, BIO_set_retry_write, BIO_set_retry_special,
+BIO_clear_retry_flags, BIO_get_retry_flags
+- manipulate and interpret BIO flags
+
+=head1 SYNOPSIS
+
+ #include <openssl/bio.h>
+
+ void BIO_set_flags(BIO *b, int flags);
+ void BIO_clear_flags(BIO *b, int flags);
+ int  BIO_test_flags(const BIO *b, int flags);
+ int  BIO_get_flags(const BIO *b);
+
+ void BIO_set_retry_read(BIO *b);
+ void BIO_set_retry_write(BIO *b);
+ void BIO_set_retry_special(BIO *b);
+ void BIO_clear_retry_flags(BIO *b);
+ int  BIO_get_retry_flags(BIO *b);
+
+=head1 DESCRIPTION
+
+A B<BIO> has an internal set of bit flags that describe its state.  These
+functions and macros are used primarily by B<BIO> implementations and by code
+that builds B<BIO> chains to manipulate those flags.
+
+BIO_set_flags() sets the bits given in I<flags> in the B<BIO> I<b>.  Any bits
+already set in the B<BIO>'s flag word remain set.
+
+BIO_clear_flags() clears the bits given in I<flags> from the B<BIO> I<b>.  Any
+other bits in the flag word are left unchanged.
+
+BIO_test_flags() tests the bits given in I<flags> in the B<BIO> I<b> and
+returns a nonzero value if any of them are currently set and zero
+otherwise.
+
+BIO_get_flags() returns the current flag word from the B<BIO> I<b>.  This is
+equivalent to testing for all bits and returning the result.
+
+The following convenience macros are built on top of these primitives and are
+used to maintain the retry state of a BIO:
+
+BIO_set_retry_read() marks the B<BIO> I<b> as being in a retryable state
+by setting the B<BIO_FLAGS_SHOULD_RETRY> flag. In addition, it sets the
+B<BIO_FLAGS_READ> flag to indicate that the retry condition is
+associated with a read operation.
+
+BIO_set_retry_write() marks the B<BIO> I<b> as being in a retryable state
+by setting the B<BIO_FLAGS_SHOULD_RETRY> flag. In addition, it sets the
+B<BIO_FLAGS_WRITE> flag to indicate that the retry condition is
+associated with a write operation.
+
+BIO_set_retry_special() marks the B<BIO> I<b> as being in a retryable state
+by setting the B<BIO_FLAGS_SHOULD_RETRY> flag. In addition, it sets the
+B<BIO_FLAGS_IO_SPECIAL> flag to indicate that the retry condition is
+associated with a read operation some "special" condition.
+The precise meaning of this condition depends on the B<BIO> type.
+
+BIO_clear_retry_flags() clears all retry-related bits from I<b>, i.e.
+B<BIO_FLAGS_READ>, B<BIO_FLAGS_WRITE>, B<BIO_FLAGS_IO_SPECIAL>, and
+B<BIO_FLAGS_SHOULD_RETRY>.
+
+BIO_get_retry_flags() returns retry-related bits that are
+currently set in I<b>.  The result is a subset of
+B<BIO_FLAGS_RWS|BIO_FLAGS_SHOULD_RETRY>.
+
+The retry bits are interpreted by the higher level macros
+BIO_should_read(), BIO_should_write(), BIO_should_io_special(),
+BIO_retry_type() and BIO_should_retry(), as documented in
+L<BIO_should_retry(3)>.  Application code will typically use those macros
+rather than manipulate the underlying flags directly.
+
+The following flag bits are currently defined for use with BIO_set_flags(),
+BIO_clear_flags() and BIO_test_flags():
+
+=over 4
+
+=item B<BIO_FLAGS_READ>
+
+The last I/O operation should be retried when the B<BIO> becomes readable.
+This flag is normally set by the B<BIO> implementation via BIO_set_retry_read()
+after a failed read operation.
+
+=item B<BIO_FLAGS_WRITE>
+
+The last I/O operation should be retried when the B<BIO> becomes writable.
+This flag is normally set by the B<BIO> implementation via BIO_set_retry_write()
+after a failed write operation.
+
+=item B<BIO_FLAGS_IO_SPECIAL>
+
+The last I/O operation should be retried when some "special" condition
+becomes true.  The precise meaning of this condition depends on the B<BIO>
+type and is usually obtained via BIO_get_retry_BIO() and
+BIO_get_retry_reason() as described in L<BIO_should_retry(3)>.
+This flag is normally set by the B<BIO> implementation via
+BIO_set_retry_special().
+
+=item B<BIO_FLAGS_RWS>
+
+The bitwise OR of B<BIO_FLAGS_READ>, B<BIO_FLAGS_WRITE> and
+B<BIO_FLAGS_IO_SPECIAL>.  This mask is used when clearing or extracting
+the retry-direction bits.
+
+=item B<BIO_FLAGS_SHOULD_RETRY>
+
+Set if the last I/O operation on the B<BIO> should be retried at a later time.
+If this bit is not set then the condition is treated as an error.
+This flag is normally set by the B<BIO> implementation.
+
+=item B<BIO_FLAGS_BASE64_NO_NL>
+
+When set on a base64 filter B<BIO> this flag disables the generation of
+newline characters in the encoded output and causes newlines to be ignored
+in the input.  See also L<BIO_f_base64(3)>.
+The flag has no effect on any other built-in B<BIO> types.
+
+=item B<BIO_FLAGS_MEM_RDONLY>
+
+When set on a memory B<BIO> this flag indicates that the underlying buffer is
+read only.  Attempts to write to such a B<BIO> will fail.
+The flag has no effect on any other built-in B<BIO> types.
+
+=item B<BIO_FLAGS_NONCLEAR_RST>
+
+On a memory B<BIO> this flag modifies the behaviour of BIO_reset().  When it
+is set, resetting the B<BIO> does not clear the underlying buffer but only
+resets the current read position.
+The flag has no effect on any other built-in B<BIO> types.
+
+=item B<BIO_FLAGS_IN_EOF>
+
+This flag may be used by a B<BIO> implementation to indicate that the end
+of the input stream has been reached.  However, B<BIO> types are not
+required to use this flag to signal end-of-file conditions; they may rely
+on other mechanisms such as system calls or by querying the next B<BIO> in a
+chain.  Applications must therefore not test this flag directly to
+determine whether EOF has been reached, and must use BIO_eof() instead.
+
+=back
+
+A range of additional flag values is reserved for internal use by OpenSSL
+to track kernel TLS (KTLS) state.  This range and the corresponding flag
+macros are not part of the public API and must not be used by applications.
+
+=head1 RETURN VALUES
+
+BIO_get_flags() returns a bit mask of the flags currently set on the B<BIO>.
+
+BIO_test_flags() returns a bit mask consisting of those flags from the
+argument that are currently set in the B<BIO>. Consequently, it returns a
+nonzero value if and only if at least one of the requested flags is set.
+
+BIO_get_retry_flags() returns a bit mask consisting of those flags from
+B<BIO_FLAGS_READ>, B<BIO_FLAGS_WRITE>, B<BIO_FLAGS_IO_SPECIAL>, and
+B<BIO_FLAGS_SHOULD_RETRY> that are currently set in the I<BIO>.
+
+=head1 NOTES
+
+Ordinary application code will rarely need to call BIO_set_flags(),
+BIO_clear_flags() or BIO_test_flags() directly.  They are intended for B<BIO>
+implementations and for code that forwards retry state from one B<BIO> in a
+chain to another.
+After a failed I/O operation, applications should normally use
+BIO_should_retry() and related macros as described in
+L<BIO_should_retry(3)> instead of inspecting the flags directly.
+
+These functions and macros are not thread-safe. If a single B<BIO>
+is accessed from multiple threads, the caller must provide appropriate
+external synchronisation.
+
+=head1 SEE ALSO
+
+L<BIO_should_retry(3)>, L<BIO_f_base64(3)>, L<bio(7)>
+
+=head1 HISTORY
+
+The functions and macros described here have been available in OpenSSL since
+at least 1.1.0 (B<BIO_FLAGS_IN_EOF> since 1.1.1).
+
+=head1 COPYRIGHT
+
+Copyright 2025 The OpenSSL Project Authors. All Rights Reserved.
+
+Licensed under the Apache License 2.0 (the "License").  You may not use
+this file except in compliance with the License.  You can obtain a copy
+in the file LICENSE in the source distribution or at
+L<https://www.openssl.org/source/license.html>.
+
+=cut

util/missingcrypto.txt

@@ -170,7 +170,6 @@ BIO_asn1_get_prefix(3)
 BIO_asn1_get_suffix(3)
 BIO_asn1_set_prefix(3)
 BIO_asn1_set_suffix(3)
-BIO_clear_flags(3)
 BIO_copy_next_retry(3)
 BIO_dgram_is_sctp(3)
 BIO_dgram_non_fatal_error(3)
@@ -208,7 +207,6 @@ BIO_nwrite(3)
 BIO_nwrite0(3)
 BIO_s_datagram_sctp(3)
 BIO_s_log(3)
-BIO_set_flags(3)
 BIO_set_tcp_ndelay(3)
 BIO_sock_error(3)
 BIO_sock_info(3)
@@ -217,7 +215,6 @@ BIO_sock_non_fatal_error(3)
 BIO_sock_should_retry(3)
 BIO_socket_ioctl(3)
 BIO_socket_nbio(3)
-BIO_test_flags(3)
 BN_GF2m_add(3)
 BN_GF2m_arr2poly(3)
 BN_GF2m_mod(3)

util/other.syms

@@ -203,6 +203,8 @@ BIO_get_conn_port                       define
 BIO_get_conn_ip_family                  define
 BIO_get_conn_mode                       define
 BIO_get_fd                              define
+BIO_get_flags                           define
+BIO_get_retry_flags                     define
 BIO_get_fp                              define
 BIO_get_indent                          define
 BIO_get_info_callback                   define
@@ -237,6 +239,12 @@ BIO_set_conn_port                       define
 BIO_set_conn_ip_family                  define
 BIO_set_conn_mode                       define
 BIO_set_fd                              define
+BIO_set_flags                           define
+BIO_set_retry_read                      define
+BIO_set_retry_write                     define
+BIO_set_retry_special                   define
+BIO_clear_flags                         define
+BIO_clear_retry_flags                   define
 BIO_set_fp                              define
 BIO_set_indent                          define
 BIO_set_info_callback                   define