On 5/14/25 3:56 PM, chia-yu.ch...@nokia-bell-labs.com wrote:
> From: Ilpo Järvinen <i...@kernel.org>
>
> As SACK blocks tend to eat all option space when there are
> many holes, it is useful to compromise on sending many SACK
> blocks in every ACK and try to fit AccECN option there
> by reduction the number of SACK blocks. But never go below
> two SACK blocks because of AccECN option.
>
> As AccECN option is often not put to every ACK, the space
> hijack is usually only temporary.
>
> Signed-off-by: Ilpo Järvinen <i...@kernel.org>
> Signed-off-by: Chia-Yu Chang <chia-yu.ch...@nokia-bell-labs.com>
> ---
> net/ipv4/tcp_output.c | 15 ++++++++++++++-
> 1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index b630923c4cef..d9d3cc8dbb5b 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -982,8 +982,21 @@ static int tcp_options_fit_accecn(struct tcp_out_options
> *opts, int required,
> opts->num_accecn_fields--;
> size -= TCPOLEN_ACCECN_PERFIELD;
> }
> - if (opts->num_accecn_fields < required)
> + if (opts->num_accecn_fields < required) {
> + if (opts->num_sack_blocks > 2) {
> + /* Try to fit the option by removing one SACK block */
> + opts->num_sack_blocks--;
> + size = tcp_options_fit_accecn(opts, required,
> + remaining +
> + TCPOLEN_SACK_PERBLOCK,
> + max_combine_saving);
How deep is the recursion level, worst case? In any case please try to
avoid recursion entirely. Possibly a 'goto' statement would help.
/P
