On Sat, Nov 30, 2024 at 07:11:27PM +0100, Pascal Stumpf wrote:
> This page references options(4), where the section documenting TCP_SACK
> got deleted in 2017.
> 
> This just copies the text that used to be there.
> 
> ok?
> 

ok.
jmc

> 
> Index: tcp.4
> ===================================================================
> RCS file: /home/cvs/src/share/man/man4/tcp.4,v
> diff -u -p -r1.27 tcp.4
> --- tcp.4	11 Aug 2022 14:04:08 -0000	1.27
> +++ tcp.4	30 Nov 2024 18:07:14 -0000
> @@ -159,8 +159,16 @@ Set the maximum segment size for this co
>  The maximum segment size can only be lowered.
>  .It Cd TCP_SACK_ENABLE
>  Use selective acknowledgements for this connection.
> -See
> -.Xr options 4 .
> +Additional information about
> +segments already received can be transmitted back to the sender,
> +thus indicating segments that have been lost and allowing for
> +a swifter recovery.
> +Both communication endpoints need to support
> +.Em SACK .
> +The fallback behaviour is NewReno fast recovery phase, which allows
> +one lost segment to be recovered per round trip time.
> +When more than one segment has been dropped per window, the transmission can
> +continue without waiting for a retransmission timeout.
>  .It Cd TCP_MD5SIG
>  Use TCP MD5 signatures per RFC 2385.
>  This requires
>