tcp: clean scoreboard when releasing the socket buffer

The SACK scoreboard is conceptually an extention of the socket
buffer. Remove it when the socket buffer goes away with
soisdisconnected(). Verify that this is also the expected
state in tcp_discardcb().

PR:			276761
Reviewed by:		glebius, tuexen, #transport
Sponsored by:		NetApp, Inc.
Differential Revision:	https://reviews.freebsd.org/D43805

sys/netinet/tcp_input.c

@@ -3022,6 +3022,7 @@ tcp_do_segment(struct tcpcb *tp, struct mbuf *m, struct tcphdr *th,
 				 * we'll hang forever.
 				 */
 				if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
+					tcp_free_sackholes(tp);
 					soisdisconnected(so);
 					tcp_timer_activate(tp, TT_2MSL,
 					    (tcp_fast_finwait2_recycle ?

sys/netinet/tcp_subr.c

@@ -2383,6 +2383,7 @@ tcp_discardcb(struct tcpcb *tp)
 #endif
 
 	INP_WLOCK_ASSERT(inp);
+	MPASS(TAILQ_EMPTY(&tp->snd_holes));
 
 	tcp_timer_stop(tp);
 
@@ -2394,9 +2395,6 @@ tcp_discardcb(struct tcpcb *tp)
 	if (tp->t_flags & TF_TOE)
 		tcp_offload_detach(tp);
 #endif
-
-	tcp_free_sackholes(tp);
-
 #ifdef TCPPCAP
 	/* Free the TCP PCAP queues. */
 	tcp_pcap_drain(&(tp->t_inpkts));
@@ -2531,6 +2529,7 @@ tcp_close(struct tcpcb *tp)
 	if (tp->t_state != TCPS_CLOSED)
 		tcp_state_change(tp, TCPS_CLOSED);
 	KASSERT(inp->inp_socket != NULL, ("tcp_close: inp_socket NULL"));
+	tcp_free_sackholes(tp);
 	soisdisconnected(so);
 	if (inp->inp_flags & INP_SOCKREF) {
 		inp->inp_flags &= ~INP_SOCKREF;

sys/netinet/tcp_timewait.c

@@ -119,6 +119,7 @@ tcp_twstart(struct tcpcb *tp)
 	    "(inp->inp_flags & INP_DROPPED) != 0"));
 
 	tcp_state_change(tp, TCPS_TIME_WAIT);
+	tcp_free_sackholes(tp);
 	soisdisconnected(inp->inp_socket);
 
 	if (tp->t_flags & TF_ACKNOW)

sys/netinet/tcp_usrreq.c

@@ -2777,6 +2777,7 @@ tcp_usrclosed(struct tcpcb *tp)
 	if (tp->t_acktime == 0)
 		tp->t_acktime = ticks;
 	if (tp->t_state >= TCPS_FIN_WAIT_2) {
+		tcp_free_sackholes(tp);
 		soisdisconnected(tptosocket(tp));
 		/* Prevent the connection hanging in FIN_WAIT_2 forever. */
 		if (tp->t_state == TCPS_FIN_WAIT_2) {