[tcp] add rewrite of TCPlp's interface code to support OpenThread's TCP API (#7190)

third_party/tcplp/bsdtcp/tcp_const.h

@@ -43,9 +43,23 @@
 #include "tcp_var.h"
 #include "tcp_timer.h"
 
+/*
+ * samkumar: these are TCPlp-specific constants that I added. They were not
+ * present in the FreeBSD-derived code.
+ */
+
+#define FRAMES_PER_SEG 5
+#define FRAMECAP_6LOWPAN (122 - 11 - 5)
+#define IP6HDR_SIZE (2 + 1 + 1 + 16 + 16) // IPHC header (2) + Next header (1) + Hop count (1) + Dest. addr (16) + Src. addr (16)
 #define MSS_6LOWPAN ((FRAMES_PER_SEG * FRAMECAP_6LOWPAN) - IP6HDR_SIZE - sizeof(struct tcphdr))
 
-// I may change some of these flags later
+/*
+ * samkumar: The remaining constants were present in the original FreeBSD code,
+ * but I set their values.
+ */
+
+#define hz 1000 // number of ticks per second, assuming millisecond ticks
+
 enum tcp_input_consts {
 	tcp_keepcnt = TCPTV_KEEPCNT,
 	tcp_fast_finwait2_recycle = 0,

third_party/tcplp/bsdtcp/tcp_subr.c

@@ -48,12 +48,12 @@
 
 #include "tcp_const.h"
 
-/* samkumar: Eventually, replace this with OpenThread's random generator. */
-// A simple linear congruential number generator
-tcp_seq seed = (tcp_seq) 0xbeaddeed;
+/*
+ * samkumar: This is rewritten to have the host network stack to generate the
+ * ISN with appropriate randomness.
+ */
 tcp_seq tcp_new_isn(struct tcpcb* tp) {
-	seed = (((tcp_seq) 0xfaded011) * seed) + (tcp_seq) 0x1ead1eaf;
-	return seed;
+	return (uint32_t) tcplp_sys_generate_isn();
 }
 
 /*

third_party/tcplp/bsdtcp/tcp_timer.c

@@ -59,10 +59,11 @@ int V_tcp_pmtud_blackhole_activated_min_mss = 0;
 /*
  * samkumar: I changed these functions to accept "struct tcpcb* tp" their
  * argument instead of "void *xtp". This is possible since we're no longer
- * relying on FreeBSD's callout subsystem in TCPlp.
+ * relying on FreeBSD's callout subsystem in TCPlp. I also changed them to
+ * return 1 if the connection is dropped, or 0 otherwise.
  */
 
-void
+int
 tcp_timer_delack(struct tcpcb* tp)
 {
 	/* samkumar: I added this, to replace the code I removed below. */
@@ -80,9 +81,10 @@ tcp_timer_delack(struct tcpcb* tp)
 	 */
 	tp->t_flags |= TF_ACKNOW;
 	(void) tcp_output(tp);
+	return 0;
 }
 
-void
+int
 tcp_timer_keep(struct tcpcb* tp)
 {
 	uint32_t ticks = tcplp_sys_get_ticks();
@@ -158,17 +160,19 @@ tcp_timer_keep(struct tcpcb* tp)
 	 * that handled debug tracing/probes, vnet, and locking. I removed that
 	 * code.
 	 */
-	return;
+	return 0;
 
 dropit:
 	tp = tcp_drop(tp, ETIMEDOUT);
 	(void) tp; /* samkumar: prevent a compiler warning */
+	return 1;
 }
 
-void
+int
 tcp_timer_persist(struct tcpcb* tp)
 {
 	uint32_t ticks = tcplp_sys_get_ticks();
+	int dropped = 0;
 
 	/* samkumar: I added this, to replace the code I removed below. */
 	KASSERT(tpistimeractive(tp, TT_PERSIST), ("Persist timer running, but unmarked\n"));
@@ -202,6 +206,7 @@ tcp_timer_persist(struct tcpcb* tp)
 	    (ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
 	     ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
 		tp = tcp_drop(tp, ETIMEDOUT);
+		dropped = 1;
 		goto out;
 	}
 
@@ -212,6 +217,7 @@ tcp_timer_persist(struct tcpcb* tp)
 	if (tp->t_state > TCPS_CLOSE_WAIT &&
 	    (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) {
 		tp = tcp_drop(tp, ETIMEDOUT);
+		dropped = 1;
 		goto out;
 	}
 
@@ -227,13 +233,14 @@ out:
 	 * tracing/probes, vnet, and locking. I removed that code.
 	 */
 	(void) tp; /* samkumar: prevent a compiler warning */
-	return;
+	return dropped;
 }
 
-void
+int
 tcp_timer_2msl(struct tcpcb* tp)
 {
 	uint32_t ticks = tcplp_sys_get_ticks();
+	int dropped = 0;
 
 	/* samkumar: I added this, to replace the code I removed below. */
 	KASSERT(tpistimeractive(tp, TT_2MSL), ("2MSL timer running, but unmarked\n"));
@@ -281,7 +288,8 @@ tcp_timer_2msl(struct tcpcb* tp)
 	if (tp->t_state == TCP6S_TIME_WAIT) {
 		tp = tcp_close(tp);
 		tcplp_sys_connection_lost(tp, CONN_LOST_NORMAL);
-		return;
+		dropped = 1;
+		return dropped;
 	}
 	/*
 	 * samkumar: This if statement also used to check that an inpcb is still
@@ -297,6 +305,7 @@ tcp_timer_2msl(struct tcpcb* tp)
 	    tpiscantrcv(tp)) {
 		tp = tcp_close(tp);
 		tcplp_sys_connection_lost(tp, CONN_LOST_NORMAL);
+		dropped = 1;
 	} else {
 		if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) {
 			/*
@@ -308,19 +317,22 @@ tcp_timer_2msl(struct tcpcb* tp)
 		} else {
 			tp = tcp_close(tp);
 			tcplp_sys_connection_lost(tp, CONN_LOST_NORMAL);
+			dropped = 1;
 		}
 	}
 	/*
 	 * samkumar: There used to be some code here that handled debug
 	 * tracing/probes, vnet, and locking. I removed that code.
 	 */
+	return dropped;
 }
 
-void
+int
 tcp_timer_rexmt(struct tcpcb *tp)
 {
 	int rexmt;
 	uint32_t ticks = tcplp_sys_get_ticks();
+	int dropped = 0;
 
 	/* samkumar: I added this, to replace the code I removed below. */
 	KASSERT(tpistimeractive(tp, TT_REXMT), ("Rexmt timer running, but unmarked\n"));
@@ -348,6 +360,7 @@ tcp_timer_rexmt(struct tcpcb *tp)
 
 		tp = tcp_drop(tp, tp->t_softerror ?
 			      tp->t_softerror : ETIMEDOUT);
+		dropped = 1;
 		goto out;
 	}
 	if (tp->t_state == TCPS_SYN_SENT) {
@@ -450,7 +463,7 @@ out:
 	 * tracing/probes, vnet, and locking. I removed that code.
 	 */
 	(void) tp; /* samkumar: Prevent a compiler warning */
-	return;
+	return dropped;
 }
 
 int

third_party/tcplp/bsdtcp/tcp_timer.h

@@ -154,11 +154,15 @@ static const int	tcp_backoff[TCP_MAXRXTSHIFT + 1] =
 
 static const int tcp_totbackoff = 2559;	/* sum of tcp_backoff[] */
 
-void tcp_timer_delack(struct tcpcb* tp);
-void tcp_timer_keep(struct tcpcb* tp);
-void tcp_timer_persist(struct tcpcb* tp);
-void tcp_timer_2msl(struct tcpcb* tp);
-void tcp_timer_rexmt(struct tcpcb *tp);
+/*
+ * samkumar: Changed return value to int to indicate whether connection was
+ * dropped or not.
+ */
+int tcp_timer_delack(struct tcpcb* tp);
+int tcp_timer_keep(struct tcpcb* tp);
+int tcp_timer_persist(struct tcpcb* tp);
+int tcp_timer_2msl(struct tcpcb* tp);
+int tcp_timer_rexmt(struct tcpcb *tp);
 int tcp_timer_active(struct tcpcb *tp, uint32_t timer_type);
 
 /*

third_party/tcplp/tcplp.h

@@ -50,14 +50,6 @@ extern "C" {
 #include <openthread/ip6.h>
 #include <openthread/message.h>
 
-#define hz 1000 // number of ticks per second
-#define MICROS_PER_TICK 1000 // number of microseconds per tick
-
-#define FRAMES_PER_SEG 5
-#define FRAMECAP_6LOWPAN (122 - 11 - 5)
-
-#define IP6HDR_SIZE (2 + 1 + 1 + 16 + 16) // IPHC header (2) + Next header (1) + Hop count (1) + Dest. addr (16) + Src. addr (16)
-
 #define RELOOKUP_REQUIRED -1
 #define CONN_LOST_NORMAL 0
 
@@ -85,6 +77,7 @@ void tcplp_sys_connection_lost(struct tcpcb* tcb, uint8_t errnum);
 void tcplp_sys_on_state_change(struct tcpcb* tcb, int newstate);
 void tcplp_sys_log(const char* format, ...);
 bool tcplp_sys_autobind(otInstance *aInstance, const otSockAddr *aPeer, otSockAddr *aToBind, bool aBindAddress, bool aBindPort);
+uint32_t tcplp_sys_generate_isn();
 
 #ifdef __cplusplus
 } // extern "C"