Implement new connection id callback using randomConnectionId()

quic/connectionid.nim

@@ -11,5 +11,5 @@ proc `len`*(x: ConnectionId): int {.borrow.}
 proc `$`*(id: ConnectionId): string =
   "0x" & cast[string](id).toHex
 
-proc randomConnectionId*: ConnectionId =
-  ConnectionId(@(getRandomBytes(DefaultConnectionIdLength)))
+proc randomConnectionId*(len = DefaultConnectionIdLength): ConnectionId =
+  ConnectionId(@(getRandomBytes(len)))

quic/ngtcp2/ids.nim

@@ -8,11 +8,6 @@ proc toCid*(id: ConnectionId): ngtcp2_cid =
   let bytes = seq[byte](id)
   toCid(unsafeAddr bytes[0], bytes.len.uint)
 
-var nextConnectionId = 1'u8
-
 proc getNewConnectionId*(connection: ptr ngtcp2_conn, id: ptr ngtcp2_cid, token: ptr uint8, cidlen: uint, userData: pointer): cint {.cdecl.} =
-  zeroMem(addr id.data[0], cidlen)
-  id.data[0] = nextConnectionId
-  inc(nextConnectionId)
-  id.datalen = cidlen
+  id[] = randomConnectionId(cidlen.int).toCid
   zeroMem(token, NGTCP2_STATELESS_RESET_TOKENLEN)

tests/quic/testConnectionId.nim

@@ -8,3 +8,6 @@ suite "Connection Ids":
 
   test "random ids are of the correct length":
     check randomConnectionId().len == DefaultConnectionIdLength
+
+  test "random ids can have custom length":
+    check randomConnectionId(5).len == 5