Check the header version on arrival and say what the error window actually spans

2026-08-04 21:29:03 -07:00
parent 49de171ad0
commit 01d673dc83
2 changed files with 9 additions and 3 deletions
@@ -11,6 +11,7 @@ const (
 	ethHdrLen = 14
 	hdrLen    = 20
 	hdrMagic  = 0x43424c54
+	hdrVer    = 1
 	minFrame  = ethHdrLen + hdrLen
 	maxFrame  = 9216

@@ -138,7 +139,7 @@ func headerCheck(h []byte) uint16 {
 func putHeader(buf []byte, patIdx int, stream uint16, seq uint64, payLen int) {
 	h := buf[ethHdrLen:]
 	binary.BigEndian.PutUint32(h[0:4], hdrMagic)
-	h[4] = 1
+	h[4] = hdrVer
 	h[5] = byte(patIdx)
 	binary.BigEndian.PutUint16(h[6:8], stream)
 	binary.BigEndian.PutUint64(h[8:16], seq)
@@ -176,6 +177,11 @@ func parseHeader(buf []byte) (parsed, hdrStatus) {
 	if binary.BigEndian.Uint16(h[hdrCheckOff:]) != headerCheck(h) {
 		return p, hdrDamaged
 	}
+	// Both halves are the same build, so the only way this differs is a checksum
+	// that happened to agree over damaged bytes.
+	if h[4] != hdrVer {
+		return p, hdrDamaged
+	}
 	p.patIdx = int(h[5])
 	p.stream = binary.BigEndian.Uint16(h[6:8])
 	p.seq = binary.BigEndian.Uint64(h[8:16])