Commit 6299c7a4 authored by Matt Caswell's avatar Matt Caswell
Browse files

Add a note about Nagle's algorithm on the SSL_connect man page 



Fixes #4237

Reviewed-by: default avatarRich Salz <rsalz@openssl.org>
Reviewed-by: default avatarBen Kaduk <kaduk@mit.edu>
(Merged from https://github.com/openssl/openssl/pull/6143)
parent aebd0e5c

doc/man3/SSL_connect.pod

+15 −0
Original line number Diff line number Diff line
@@ -35,6 +35,21 @@ nothing is to be done, but select() can be used to check for the required 
condition. When using a buffering BIO, like a BIO pair, data must be written

into or retrieved out of the BIO before being able to continue.



Many systems implement Nagle's algorithm by default which means that it will

buffer outgoing TCP data if a TCP packet has already been sent for which no

corresponding ACK has been received yet from the peer. This can have performance

impacts after a successful TLSv1.3 handshake or a successful TLSv1.2 (or below)

resumption handshake, because the last peer to communicate in the handshake is

the client. If the client is also the first to send application data (as is

typical for many protocols) then this data could be buffered until an ACK has

been received for the final handshake message.



The B<TCP_NODELAY> socket option is often available to disable Nagle's

algorithm. If an application opts to disable Nagle's algorithm consideration

should be given to turning it back on again later if appropriate. The helper

function BIO_set_tcp_ndelay() can be used to turn on or off the B<TCP_NODELAY>

option.



=head1 RETURN VALUES



The following return values can occur: