From 523f60976184f24a2fc1f8d09d2c5eb03aae073c Mon Sep 17 00:00:00 2001
From: soypat <graded.sp@gmail.com>
Date: Sun, 16 Feb 2025 14:47:02 -0300
Subject: [PATCH] now supports partial packet acks

---
 tcp/txqueue.go      |  6 +++---
 tcp/txqueue_test.go | 30 ++++++++++++++++++++++++++++--
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/tcp/txqueue.go b/tcp/txqueue.go
index 33898e2..1bfe450 100644
--- a/tcp/txqueue.go
+++ b/tcp/txqueue.go
@@ -192,7 +192,7 @@ 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 || acked < minBufferSize {
 				panic("unreachable")
 			}
 			off := rtx.addOff(pkt.off, acked)
@@ -266,7 +266,7 @@ func (rtx *ringTx) firstPkt() int {
 	idx := -1
 	for i := 0; i < len(rtx.packets); i++ {
 		pkt := &rtx.packets[i]
-		if pkt.sent() && (idx == -1 || seq.LessThan(pkt.seq)) {
+		if pkt.sent() && (idx == -1 || pkt.seq.LessThan(seq)) {
 			seq = pkt.seq
 			idx = i
 		}
@@ -279,7 +279,7 @@ func (rtx *ringTx) lastPkt() int {
 	idx := -1
 	for i := 0; i < len(rtx.packets); i++ {
 		pkt := &rtx.packets[i]
-		if pkt.sent() && (idx == -1 || pkt.seq.LessThan(seq)) {
+		if pkt.sent() && (idx == -1 || seq.LessThan(pkt.seq)) {
 			seq = pkt.seq
 			idx = i
 		}
diff --git a/tcp/txqueue_test.go b/tcp/txqueue_test.go
index e3488c3..0d0e6b7 100644
--- a/tcp/txqueue_test.go
+++ b/tcp/txqueue_test.go
@@ -12,9 +12,12 @@ func TestTxQueue(t *testing.T) {
 	const bufsize = 1024
 	var msgBuf, ringBuf, readBuf, aux [bufsize]byte
 	rng := rand.New(rand.NewSource(1))
-
+	panicked := true
 	var rtx ringTx
 	defer func() {
+		if panicked {
+			t.Error("panicked, rtx:\n", rtx.string())
+		}
 		testQueueSanity(t, &rtx)
 	}()
 	increasingComplexityTests := []struct {
@@ -92,7 +95,7 @@ func TestTxQueue(t *testing.T) {
 			},
 		},
 		2: {
-			name: "ParialAcks",
+			name: "PartialAcks",
 			test: func(t *testing.T) {
 				const startAck = 0
 				const packets = 100
@@ -153,6 +156,7 @@ func TestTxQueue(t *testing.T) {
 			t.Fatalf("subtest %d/%d %q failed, not running more complex tests until fixed", i+1, len(increasingComplexityTests), test.name)
 		}
 	}
+	panicked = false
 }
 
 func testQueueSanity(t *testing.T, rtx *ringTx) {
@@ -213,6 +217,28 @@ func testQueueSanity(t *testing.T, rtx *ringTx) {
 	} else if !allEmpty && sentEmpty && unsentEmpty {
 		t.Fatal("all buffer not empty but sent&unsentempty")
 	}
+
+	// Check sanenness of last/first packets.
+	last := rtx.lastPkt()
+	first := rtx.firstPkt()
+	if first < 0 && last >= 0 || last < 0 && first >= 0 {
+		t.Fatalf("found first/last(%d,%d) but did not find last/first", first, last)
+	}
+	// Check sent data or return if no sent data available.
+	if sent == 0 {
+		return
+	}
+	lastPkt := rtx.pkt(last)
+	endseq, ok := rtx.endSeq()
+	firstPkt := rtx.pkt(first)
+	lastEndSeq := Add(lastPkt.seq, lastPkt.size)
+	if lastPkt.seq.LessThan(firstPkt.seq) {
+		t.Fatalf("first packet not previous to last packet seq, wanted %d<%d", firstPkt.seq, lastPkt.seq)
+	} else if !ok {
+		t.Fatal("unexpected end sequence not found")
+	} else if lastEndSeq != endseq {
+		t.Fatalf("last packet end sequence not match with got endSeq %d!=%d", lastEndSeq, endseq)
+	}
 }
 
 func (rx *ringTx) string() string {