tcp: fix indefinite deferral of RTO with SACK reneging Many thanks to Jakub Kicinski and Neil Spring, who reported... issue. Also, many thanks to Jakub Kicinski for testing this fix. Reported-by: Jakub Kicinski <kuba@kernel.org> Tested-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Jakub Kicinski <kuba@kernel.org>