By definition, the very first FIN is not a duplicate. Process it normally and don't feed it to congestion control as though it were a dupe. Don't prevent CC from seeing later dupe acks while in a half close state.
By definition, the very first FIN is not a duplicate. Process it normally and don't feed it to congestion control as though it were a dupe. Don't prevent CC from seeing later dupe acks while in a half close state.