From 329513fdde49301e68891ca781e003689cb352c4 Mon Sep 17 00:00:00 2001
From: Mark Spanbroek <mark@spanbroek.net>
Date: Mon, 21 Sep 2020 11:00:44 +0200
Subject: [PATCH] Supported version field for version negotation packets

---
 quic/packets.nim           | 12 +++++++++++-
 tests/quic/testPackets.nim | 10 ++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/quic/packets.nim b/quic/packets.nim
index 28e5fbc..9a584a0 100644
--- a/quic/packets.nim
+++ b/quic/packets.nim
@@ -88,9 +88,19 @@ proc `$`*(header: PacketHeader): string =
 
 proc `==`*(x: ConnectionId, y: ConnectionId): bool {.borrow.}
 
+proc supportedVersionSlice(header: PacketHeader): Slice[int] =
+  let start = header.sourceSlice().b + 1
+  result = start..<start+4
+
+proc supportedVersion*(header: PacketHeader): uint32 =
+  let versionBytes = header.bytes[header.supportedVersionSlice]
+  result.bytes[0] = versionBytes[0]
+  result.bytes[1] = versionBytes[1]
+  result.bytes[2] = versionBytes[2]
+  result.bytes[3] = versionBytes[3]
 proc packetLength*(header: PacketHeader): int =
   case header.kind:
   of packetVersionNegotiation:
-    return header.sourceSlice.b + 1 + 4
+    return header.supportedVersionSlice.b + 1
   else:
     return 0
diff --git a/tests/quic/testPackets.nim b/tests/quic/testPackets.nim
index f7d0055..a79c276 100644
--- a/tests/quic/testPackets.nim
+++ b/tests/quic/testPackets.nim
@@ -121,6 +121,16 @@ suite "long headers":
         source.len + 1 +
         version1.len
 
+    test "has a supported version field":
+      let header = newPacketHeader(
+        type0 &
+        version0 &
+        destination.len.uint8 & destination &
+        source.len.uint8 & source &
+        version1
+      )
+      check header.supportedVersion == 1'u32
+
 suite "packet numbers":
 
   test "packet numbers are in the range 0 to 2^62-1":