From 46137bbbec787af3fb7215b8a89663e7f94331eb Mon Sep 17 00:00:00 2001
From: Patricio Whittingslow <graded.sp@gmail.com>
Date: Mon, 27 Oct 2025 23:21:41 -0300
Subject: [PATCH] begin adding TxQueue failing multipacket test

---
 tcp/txqueue.go      |  3 +-
 tcp/txqueue_test.go | 70 +++++++++++++++++++++++++++++++++++++++++++++
 x/xnet/xnet_test.go | 17 +++++++----
 3 files changed, 82 insertions(+), 8 deletions(-)

diff --git a/tcp/txqueue.go b/tcp/txqueue.go
index 479e579..755c067 100644
--- a/tcp/txqueue.go
+++ b/tcp/txqueue.go
@@ -158,7 +158,6 @@ func (rtx *ringTx) RecvACK(ack Value) error {
 	pkt0 := rtx.pkt(first)
 	if ack.LessThanEq(pkt0.seq) {
 		return fmt.Errorf("incoming ack %d older than first packet seq %d", ack, pkt0.seq)
-		// return errors.New("old packet")
 	}
 	// lastAckedPkt stores last fully acked packet.
 	var lastAckedPkt *ringidx
@@ -195,7 +194,7 @@ func (rtx *ringTx) RecvACK(ack Value) error {
 			acked := int(ack - pkt.seq)
 			pring := rtx.ring(pkt.off, pkt.end)
 			buffered := pring.Buffered()
-			if acked > buffered || acked < minBufferSize {
+			if acked > buffered {
 				panic("unreachable")
 			}
 			off := rtx.addOff(pkt.off, acked)
diff --git a/tcp/txqueue_test.go b/tcp/txqueue_test.go
index 0d0e6b7..d463a9b 100644
--- a/tcp/txqueue_test.go
+++ b/tcp/txqueue_test.go
@@ -8,6 +8,76 @@ import (
 	"testing"
 )
 
+func TestTxQueue_multipacket(t *testing.T) {
+	const mtu = 256
+	const iss = 1
+	const maxPkts = 3
+	const maxWrites = 20
+	const maxWriteSize = mtu / maxWrites
+	var rtx ringTx
+	internalbuff := make([]byte, mtu)
+	rng := rand.New(rand.NewSource(1))
+	var wbuf, rbuf [mtu]byte
+	for itest := 0; itest < 32; itest++ {
+		err := rtx.Reset(internalbuff, maxPkts, iss)
+		if err != nil {
+			t.Fatal(err)
+		}
+		numWrites := rng.Intn(maxWrites) + 1
+		total := 0
+		woff := 0
+		for iw := 0; iw < numWrites; iw++ {
+			wlen := rng.Intn(maxWriteSize) + 1
+			towrite := wbuf[woff : woff+wlen]
+			rng.Read(towrite)
+			n, err := rtx.Write(towrite)
+			testQueueSanity(t, &rtx)
+			woff += n
+			if err != nil {
+				t.Fatal(err)
+			} else if n != wlen {
+				t.Fatal("expected wlen==n", wlen, n)
+			}
+			total += wlen
+		}
+		npkt := rng.Intn(maxPkts) + 1
+		roff := 0
+		seq := Value(iss)
+		for ipkt := 0; ipkt < npkt; ipkt++ {
+			maxToPacket := min(total-roff, maxWriteSize)
+			pktlen := rng.Intn(maxToPacket) + 1
+			pkt := rbuf[roff : roff+pktlen]
+			expectPkt := wbuf[roff : roff+pktlen]
+			ngot, err := rtx.MakePacket(pkt, seq)
+			testQueueSanity(t, &rtx)
+			roff += ngot
+			seq += Value(ngot)
+			if err != nil {
+				t.Fatal(err)
+			} else if pktlen != ngot && roff != total {
+				t.Fatal(err)
+			} else if !bytes.Equal(expectPkt, pkt) {
+				t.Fatal("mismatched data written", expectPkt, pkt)
+			}
+			if roff == total {
+				break // made packet from all data.
+			}
+		}
+		acked := 0
+		for acked < roff {
+			maxToack := min(roff-acked, maxWriteSize)
+			toack := rng.Intn(maxToack) + 1
+			t.Log("\n", rtx.string())
+			err = rtx.RecvACK(iss + Value(acked+toack))
+			testQueueSanity(t, &rtx)
+			if err != nil {
+				t.Fatal(err)
+			}
+			acked += toack
+		}
+	}
+}
+
 func TestTxQueue(t *testing.T) {
 	const bufsize = 1024
 	var msgBuf, ringBuf, readBuf, aux [bufsize]byte
diff --git a/x/xnet/xnet_test.go b/x/xnet/xnet_test.go
index 95449b7..ffabb64 100644
--- a/x/xnet/xnet_test.go
+++ b/x/xnet/xnet_test.go
@@ -34,16 +34,21 @@ func TestStackAsyncTCP_multipacket(t *testing.T) {
 	tst.TestTCPSetupAndEstablish(sv, client, svconn, clconn, svPort, 1337)
 	tst.TestTCPClose(client, sv, clconn, svconn)
 	var buf [MTU]byte
-	for i := 0; i < 30; i++ {
+	for i := 0; i < 1; i++ {
 		payloadSize := rng.Intn(maxPktLen) + 1
 		tst.TestTCPSetupAndEstablish(sv, client, svconn, clconn, svPort, 1337)
-		npkt := rng.Intn(maxNPkt-1) + 2
-		for ipkt := 0; ipkt < npkt; ipkt++ {
-			a, _ := rng.Read(buf[:payloadSize])
-			tst.TestTCPEstablishedSingleData(sv, client, svconn, clconn, buf[:a])
-		}
+		// npkt := rng.Intn(maxNPkt-1) + 2
+		a, _ := rng.Read(buf[:payloadSize])
+		tst.TestTCPEstablishedSingleData(sv, client, svconn, clconn, buf[:a])
+		a, _ = rng.Read(buf[:payloadSize])
+		tst.TestTCPEstablishedSingleData(sv, client, svconn, clconn, buf[:a])
+		// for ipkt := 0; ipkt < npkt; ipkt++ {
+		// 	a, _ := rng.Read(buf[:payloadSize])
+		// 	tst.TestTCPEstablishedSingleData(sv, client, svconn, clconn, buf[:a])
+		// }
 		tst.TestTCPClose(client, sv, clconn, svconn)
 		if t.Failed() {
+			t.Error("multi failed")
 			t.FailNow()
 		}
 	}