Add TFO support to socket BIO and s_client/s_server

Supports Linux, MacOS and FreeBSD
Disabled by default, enabled via `enabled-tfo`
Some tests

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8692)

1 files changed, 29 insertions, 3 deletions

diff --git a/doc/man7/bio.pod b/doc/man7/bio.pod
index 9b86e9493d..0155bf6a40 100644
--- a/doc/man7/bio.pod
+++ b/doc/man7/bio.pod
@@ -36,7 +36,6 @@ BIO and one or more filter BIOs. Data read from or written to the
 first BIO then traverses the chain to the end (normally a source/sink
 BIO).
 
-
 Some BIOs (such as memory BIOs) can be used immediately after calling
 BIO_new(). Others (such as file BIOs) need some additional initialization,
 and frequently a utility function exists to create and initialize such BIOs.
@@ -52,6 +51,29 @@ pointer to a BIO_METHOD. There is a naming convention for such functions:
 a source/sink BIO typically starts with I<BIO_s_> and
 a filter BIO with I<BIO_f_>.
 
+=head2 TCP Fast Open
+
+TCP Fast Open (RFC7413), abbreviated "TFO", is supported by the BIO
+interface since OpenSSL 3.1. TFO is supported in the following operating systems:
+
+=over 4
+
+=item * Linux kernel 3.13 and later, where TFO is enabled by default.
+
+=item * Linux kernel 4.11 and later, using TCP_FASTOPEN_CONNECT.
+
+=item * FreeBSD 10.3 to 11.4, supports server TFO only.
+
+=item * FreeBSD 12.0 and later, supports both client and server TFO.
+
+=item * macOS 10.14 and later.
+
+=back
+
+Each operating system has a slightly different API for TFO. Please
+refer to the operating systems' API documentation when using
+sockets directly.
+
 =head1 EXAMPLES
 
 Create a memory BIO:
@@ -65,7 +87,9 @@ L<BIO_f_base64(3)>, L<BIO_f_buffer(3)>,
 L<BIO_f_cipher(3)>, L<BIO_f_md(3)>,
 L<BIO_f_null(3)>, L<BIO_f_ssl(3)>,
 L<BIO_f_readbuffer(3)>,
-L<BIO_find_type(3)>, L<BIO_new(3)>,
+L<BIO_find_type(3)>,
+L<BIO_get_conn_mode(3)>,
+L<BIO_new(3)>,
 L<BIO_new_bio_pair(3)>,
 L<BIO_push(3)>, L<BIO_read_ex(3)>,
 L<BIO_s_accept(3)>, L<BIO_s_bio(3)>,
@@ -73,6 +97,9 @@ L<BIO_s_connect(3)>, L<BIO_s_fd(3)>,
 L<BIO_s_file(3)>, L<BIO_s_mem(3)>,
 L<BIO_s_null(3)>, L<BIO_s_socket(3)>,
 L<BIO_set_callback(3)>,
+L<BIO_set_conn_mode(3)>,
+L<BIO_set_tfo(3)>,
+L<BIO_set_tfo_accept(3)>,
 L<BIO_should_retry(3)>
 
 =head1 COPYRIGHT
@@ -85,4 +112,3 @@ in the file LICENSE in the source distribution or at
 L<https://www.openssl.org/source/license.html>.
 
 =cut
-