quic: decode packet numbers >255 in tests

Decoding QUIC packet numbers requires keeping track of the largest
packet number received so far from the peer. Our tests haven't
bothered doing that so far, so tests can't work with packet
numbers past 255.

Fix that so we can write tests that use more packets.

Change-Id: Icb795e5cf69794381c12a3a03b0da6bcf47a69c0
Reviewed-on: https://go-review.googlesource.com/c/net/+/664296
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Auto-Submit: Damien Neil <dneil@google.com>

quic/conn_test.go

diff --git a/quic/conn_test.go b/quic/conn_test.go
index e17efcc..4b0511f 100644
--- a/quic/conn_test.go
+++ b/quic/conn_test.go
@@ -161,6 +161,9 @@
 	peerConnID        []byte                         // source conn id of peer's packets
 	peerNextPacketNum [numberSpaceCount]packetNumber // next packet number to use
 
+	// Maximum packet number received from the conn.
+	pnumMax [numberSpaceCount]packetNumber
+
 	// Datagrams, packets, and frames sent by the conn,
 	// but not yet processed by the test.
 	sentDatagrams [][]byte
@@ -845,6 +848,7 @@
 			}
 		case packetTypeInitial, packetTypeHandshake:
 			var k fixedKeys
+			var pnumMax packetNumber
 			if tc == nil {
 				if ptype == packetTypeInitial {
 					p, _ := parseGenericLongHeaderPacket(buf)
@@ -856,18 +860,27 @@
 				switch ptype {
 				case packetTypeInitial:
 					k = tc.keysInitial.r
+					pnumMax = tc.pnumMax[initialSpace]
 				case packetTypeHandshake:
 					k = tc.keysHandshake.r
+					pnumMax = tc.pnumMax[handshakeSpace]
 				}
 			}
 			if !k.isSet() {
 				t.Fatalf("reading %v packet with no read key", ptype)
 			}
-			var pnumMax packetNumber // TODO: Track packet numbers.
 			p, n := parseLongHeaderPacket(buf, k, pnumMax)
 			if n < 0 {
 				t.Fatalf("packet parse error")
 			}
+			if tc != nil {
+				switch ptype {
+				case packetTypeInitial:
+					tc.pnumMax[initialSpace] = max(pnumMax, p.num)
+				case packetTypeHandshake:
+					tc.pnumMax[handshakeSpace] = max(pnumMax, p.num)
+				}
+			}
 			frames, err := parseTestFrames(t, p.payload)
 			if err != nil {
 				t.Fatal(err)
@@ -891,7 +904,10 @@
 			if tc == nil || !tc.rkeyAppData.hdr.isSet() {
 				t.Fatalf("reading 1-RTT packet with no read key")
 			}
-			var pnumMax packetNumber // TODO: Track packet numbers.
+			var pnumMax packetNumber
+			if tc != nil {
+				pnumMax = tc.pnumMax[appDataSpace]
+			}
 			pnumOff := 1 + len(tc.peerConnID)
 			// Try unprotecting the packet with the first maxTestKeyPhases keys.
 			var phase int
@@ -914,6 +930,9 @@
 			if err != nil {
 				t.Fatalf("1-RTT packet payload parse error")
 			}
+			if tc != nil {
+				tc.pnumMax[appDataSpace] = max(pnumMax, pnum)
+			}
 			frames, err := parseTestFrames(t, pay)
 			if err != nil {
 				t.Fatal(err)