[tcp] send RST and clear send buffer on abort (openthread#11269)

This commit corrects the timing of Transmission Control Block (TCB)
re-initialization to ensure proper RST packet sending during TCP
connection aborts and to prevent potential issues due to incomplete
TCB cleanup.

Author: dsyx

src/core/net/tcp6.cpp

@@ -1089,13 +1089,9 @@ void tcplp_sys_connection_lost(struct tcpcb *aTcb, uint8_t aErrNum)
 
 void tcplp_sys_on_state_change(struct tcpcb *aTcb, int aNewState)
 {
-    if (aNewState == TCP6S_CLOSED)
-    {
-        /* Re-initialize the TCB. */
-        cbuf_pop(&aTcb->recvbuf, cbuf_used_space(&aTcb->recvbuf));
-        aTcb->accepted_from = nullptr;
-        initialize_tcb(aTcb);
-    }
+    OT_UNUSED_VARIABLE(aTcb);
+    OT_UNUSED_VARIABLE(aNewState);
+
     /* Any adaptive changes to the sleep interval would go here. */
 }
 

third_party/tcplp/bsdtcp/tcp_subr.c

@@ -49,6 +49,8 @@
 
 #include "tcp_const.h"
 
+static void reinitialize_tcb(struct tcpcb* tp);
+
 /*
  * samkumar: This is rewritten to have the host network stack to generate the
  * ISN with appropriate randomness.
@@ -145,6 +147,15 @@ void initialize_tcb(struct tcpcb* tp) {
 	tcp_sack_init(tp);
 }
 
+/* Re-initialize the TCB. */
+static void reinitialize_tcb(struct tcpcb* tp)
+{
+	uint32_t ntraversed;
+	lbuf_pop(&tp->sendbuf, lbuf_used_space(&tp->sendbuf), &ntraversed);
+	cbuf_pop(&tp->recvbuf, cbuf_used_space(&tp->recvbuf));
+	tp->accepted_from = NULL;
+	initialize_tcb(tp);
+}
 
 /*
  * samkumar: Most of this function was no longer needed. It did things like
@@ -165,6 +176,8 @@ tcp_discardcb(struct tcpcb *tp)
 		CC_ALGO(tp)->cb_destroy(tp->ccv);
 
 	tcp_free_sackholes(tp);
+
+	reinitialize_tcb(tp);
 }
 
 
@@ -352,7 +365,7 @@ struct tcpcb *
 tcp_drop(struct tcpcb *tp, int errnum)
 {
 	if (TCPS_HAVERCVDSYN(tp->t_state)) {
-		tcp_state_change(tp, TCPS_CLOSED);
+		tcp_state_change(tp, TCP6S_CLOSED);
 		(void) tcplp_output(tp);
 	}
 	if (errnum == ETIMEDOUT && tp->t_softerror)

third_party/tcplp/bsdtcp/tcp_usrreq.c

@@ -522,7 +522,7 @@ tcp_usr_abort(struct tcpcb* tp)
 	if (tp->t_state != TCP6S_TIME_WAIT &&
 		tp->t_state != TCP6S_CLOSED) {
 		tcp_drop(tp, ECONNABORTED);
-	} else if (tp->t_state == TCPS_TIME_WAIT) { // samkumar: I added this clause
+	} else if (tp->t_state == TCP6S_TIME_WAIT) { // samkumar: I added this clause
 		tp = tcp_close_tcb(tp);
 		tcplp_sys_connection_lost(tp, CONN_LOST_NORMAL);
 	}