improve the MTU discovery integration test

integrationtests/self/mtu_test.go

@@ -45,7 +45,8 @@ var _ = Describe("DPLPMTUD", func() {
  }()
 
  var mx sync.Mutex
- var maxPacketSizeClient, maxPacketSizeServer int
+ var maxPacketSizeServer int
+ var clientPacketSizes []int
  serverPort := ln.Addr().(*net.UDPAddr).Port
  proxy, err := quicproxy.NewQuicProxy("localhost:0", &quicproxy.Opts{
  RemoteAddr: fmt.Sprintf("localhost:%d", serverPort),
@@ -58,9 +59,7 @@ var _ = Describe("DPLPMTUD", func() {
  defer mx.Unlock()
  switch dir {
  case quicproxy.DirectionIncoming:
- if len(packet) > maxPacketSizeClient {
- maxPacketSizeClient = len(packet)
- }
+ clientPacketSizes = append(clientPacketSizes, len(packet))
  case quicproxy.DirectionOutgoing:
  if len(packet) > maxPacketSizeServer {
  maxPacketSizeServer = len(packet)
@@ -122,17 +121,27 @@ var _ = Describe("DPLPMTUD", func() {
 
  mx.Lock()
  defer mx.Unlock()
+ Expect(mtus).ToNot(BeEmpty())
+ maxPacketSizeClient := int(mtus[len(mtus)-1])
  fmt.Fprintf(GinkgoWriter, "max client packet size: %d, MTU: %d\n", maxPacketSizeClient, mtu)
  fmt.Fprintf(GinkgoWriter, "max datagram size: initial: %d, final: %d\n", initialMaxDatagramSize, finalMaxDatagramSize)
  fmt.Fprintf(GinkgoWriter, "max server packet size: %d, MTU: %d\n", maxPacketSizeServer, mtu)
- Expect(maxPacketSizeClient).To(BeEquivalentTo(mtus[len(mtus)-1]))
  Expect(maxPacketSizeClient).To(BeNumerically(">=", mtu-25))
  const maxDiff = 40 // this includes the 21 bytes for the short header, 16 bytes for the encryption tag, and framing overhead
  Expect(initialMaxDatagramSize).To(BeNumerically(">=", protocol.MinInitialPacketSize-maxDiff))
  Expect(finalMaxDatagramSize).To(BeNumerically(">=", maxPacketSizeClient-maxDiff))
- Expect(mtus).ToNot(BeEmpty())
  // MTU discovery was disabled on the server side
  Expect(maxPacketSizeServer).To(Equal(1234))
+
+ var numPacketsLargerThanDiscoveredMTU int
+ for _, s := range clientPacketSizes {
+ if s > maxPacketSizeClient {
+ numPacketsLargerThanDiscoveredMTU++
+ }
+ }
+ // The client shouldn't have sent any packets larger than the MTU it discovered,
+ // except for at most one MTU probe packet.
+ Expect(numPacketsLargerThanDiscoveredMTU).To(BeNumerically("<=", 1))
  })
 
  It("uses the initial packet size", func() {