Repository: quic-go/quic-go
Pull request #3847 (2023-05-20 08:14:04)

ackhandler: simplify sentPacketHandler.SentPacket
No functional change expected.

codecov[bot]: ## [Codecov](https://app.codecov.io/gh/quic-go/quic-go/pull/3847?src=pr&el=h1&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) Report
> Merging [#3847](https://app.codecov.io/gh/quic-go/quic-go/pull/3847?src=pr&el=desc&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) (2fc9367) into [master](https://app.codecov.io/gh/quic-go/quic-go/commit/f401a73d271b76a353313de227fb19ff53a8bedd?el=desc&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) (f401a73) will **increase** coverage by `0.02%`.
> The diff coverage is `78.95%`.

```diff
@@            Coverage Diff             @@
##           master    #3847      +/-   ##
==========================================
+ Coverage   83.92%   83.93%   +0.02%     
==========================================
  Files         146      146              
  Lines       14307    14303       -4     
==========================================
- Hits        12006    12005       -1     
+ Misses       1860     1858       -2     
+ Partials      441      440       -1     
```


| [Impacted Files](https://app.codecov.io/gh/quic-go/quic-go/pull/3847?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | |
|---|---|---|
| [internal/ackhandler/sent\_packet\_handler.go](https://app.codecov.io/gh/quic-go/quic-go/pull/3847?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-aW50ZXJuYWwvYWNraGFuZGxlci9zZW50X3BhY2tldF9oYW5kbGVyLmdv) | `78.07% <78.95%> (-0.14%)` | :arrow_down: |

... and [1 file with indirect coverage changes](https://app.codecov.io/gh/quic-go/quic-go/pull/3847/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None)



Patch:
diff --git a/connection.go b/connection.go
index 6833a7b9..c4a91a35 100644
--- a/connection.go
+++ b/connection.go
@@ -312,9 +312,14 @@ var newConnection = func(
 		DisableActiveMigration:          true,
 		StatelessResetToken:             &statelessResetToken,
 		OriginalDestinationConnectionID: origDestConnID,
-		ActiveConnectionIDLimit:         protocol.MaxActiveConnectionIDs,
-		InitialSourceConnectionID:       srcConnID,
-		RetrySourceConnectionID:         retrySrcConnID,
+		// For interoperability with quic-go versions before May 2023, this value must be set to a value
+		// different from protocol.DefaultActiveConnectionIDLimit.
+		// If set to the default value, it will be omitted from the transport parameters, which will make
+		// old quic-go versions interpret it as 0, instead of the default value of 2.
+		// See https://github.com/quic-go/quic-go/pull/3806.
+		ActiveConnectionIDLimit:   protocol.MaxActiveConnectionIDs,
+		InitialSourceConnectionID: srcConnID,
+		RetrySourceConnectionID:   retrySrcConnID,
 	}
 	if s.config.EnableDatagrams {
 		params.MaxDatagramFrameSize = protocol.MaxDatagramFrameSize
@@ -426,8 +431,13 @@ var newClientConnection = func(
 		MaxAckDelay:                    protocol.MaxAckDelayInclGranularity,
 		AckDelayExponent:               protocol.AckDelayExponent,
 		DisableActiveMigration:         true,
-		ActiveConnectionIDLimit:        protocol.MaxActiveConnectionIDs,
-		InitialSourceConnectionID:      srcConnID,
+		// For interoperability with quic-go versions before May 2023, this value must be set to a value
+		// different from protocol.DefaultActiveConnectionIDLimit.
+		// If set to the default value, it will be omitted from the transport parameters, which will make
+		// old quic-go versions interpret it as 0, instead of the default value of 2.
+		// See https://github.com/quic-go/quic-go/pull/3806.
+		ActiveConnectionIDLimit:   protocol.MaxActiveConnectionIDs,
+		InitialSourceConnectionID: srcConnID,
 	}
 	if s.config.EnableDatagrams {
 		params.MaxDatagramFrameSize = protocol.MaxDatagramFrameSize
diff --git a/framer.go b/framer.go
index 0b205916..79c28e23 100644
--- a/framer.go
+++ b/framer.go
@@ -6,6 +6,7 @@ import (
 
 	"github.com/quic-go/quic-go/internal/ackhandler"
 	"github.com/quic-go/quic-go/internal/protocol"
+	"github.com/quic-go/quic-go/internal/utils/ringbuffer"
 	"github.com/quic-go/quic-go/internal/wire"
 	"github.com/quic-go/quic-go/quicvarint"
 )
@@ -28,7 +29,7 @@ type framerI struct {
 	streamGetter streamGetter
 
 	activeStreams map[protocol.StreamID]struct{}
-	streamQueue   []protocol.StreamID
+	streamQueue   ringbuffer.RingBuffer[protocol.StreamID]
 
 	controlFrameMutex sync.Mutex
 	controlFrames     []wire.Frame
@@ -45,7 +46,7 @@ func newFramer(streamGetter streamGetter) framer {
 
 func (f *framerI) HasData() bool {
 	f.mutex.Lock()
-	hasData := len(f.streamQueue) > 0
+	hasData := !f.streamQueue.Empty()
 	f.mutex.Unlock()
 	if hasData {
 		return true
@@ -84,7 +85,7 @@ func (f *framerI) AppendControlFrames(frames []*ackhandler.Frame, maxLen protoco
 func (f *framerI) AddActiveStream(id protocol.StreamID) {
 	f.mutex.Lock()
 	if _, ok := f.activeStreams[id]; !ok {
-		f.streamQueue = append(f.streamQueue, id)
+		f.streamQueue.PushBack(id)
 		f.activeStreams[id] = struct{}{}
 	}
 	f.mutex.Unlock()
@@ -95,13 +96,12 @@ func (f *framerI) AppendStreamFrames(frames []*ackhandler.Frame, maxLen protocol
 	var lastFrame *ackhandler.Frame
 	f.mutex.Lock()
 	// pop STREAM frames, until less than MinStreamFrameSize bytes are left in the packet
-	numActiveStreams := len(f.streamQueue)
+	numActiveStreams := f.streamQueue.Len()
 	for i := 0; i < numActiveStreams; i++ {
 		if protocol.MinStreamFrameSize+length > maxLen {
 			break
 		}
-		id := f.streamQueue[0]
-		f.streamQueue = f.streamQueue[1:]
+		id := f.streamQueue.PopFront()
 		// This should never return an error. Better check it anyway.
 		// The stream will only be in the streamQueue, if it enqueued itself there.
 		str, err := f.streamGetter.GetOrOpenSendStream(id)
@@ -117,7 +117,7 @@ func (f *framerI) AppendStreamFrames(frames []*ackhandler.Frame, maxLen protocol
 		remainingLen += quicvarint.Len(uint64(remainingLen))
 		frame, hasMoreData := str.popStreamFrame(remainingLen, v)
 		if hasMoreData { // put the stream back in the queue (at the end)
-			f.streamQueue = append(f.streamQueue, id)
+			f.streamQueue.PushBack(id)
 		} else { // no more data to send. Stream is not active any more
 			delete(f.activeStreams, id)
 		}
@@ -146,7 +146,7 @@ func (f *framerI) Handle0RTTRejection() error {
 	defer f.mutex.Unlock()
 
 	f.controlFrameMutex.Lock()
-	f.streamQueue = f.streamQueue[:0]
+	f.streamQueue.Clear()
 	for id := range f.activeStreams {
 		delete(f.activeStreams, id)
 	}
diff --git a/go.mod b/go.mod
index bdb8183f..9cdfd0d6 100644
--- a/go.mod
+++ b/go.mod
@@ -5,25 +5,26 @@ go 1.19
 require (
 	github.com/francoispqt/gojay v1.2.13
 	github.com/golang/mock v1.6.0
-	github.com/onsi/ginkgo/v2 v2.2.0
-	github.com/onsi/gomega v1.20.1
+	github.com/onsi/ginkgo/v2 v2.9.5
+	github.com/onsi/gomega v1.27.6
 	github.com/quic-go/qpack v0.4.0
 	github.com/quic-go/qtls-go1-19 v0.3.2
 	github.com/quic-go/qtls-go1-20 v0.2.2
 	golang.org/x/crypto v0.4.0
 	golang.org/x/exp v0.0.0-20221205204356-47842c84f3db
-	golang.org/x/net v0.7.0
-	golang.org/x/sync v0.1.0
-	golang.org/x/sys v0.5.0
+	golang.org/x/net v0.10.0
+	golang.org/x/sync v0.2.0
+	golang.org/x/sys v0.8.0
 )
 
 require (
-	github.com/go-task/slim-sprig v0.0.0-20210107165309-348f09dbbbc0 // indirect
-	github.com/google/go-cmp v0.5.8 // indirect
+	github.com/go-logr/logr v1.2.4 // indirect
+	github.com/go-task/slim-sprig v0.0.0-20230315185526-52ccab3ef572 // indirect
+	github.com/google/go-cmp v0.5.9 // indirect
 	github.com/google/pprof v0.0.0-20210407192527-94a9f03dee38 // indirect
-	golang.org/x/mod v0.6.0 // indirect
-	golang.org/x/text v0.7.0 // indirect
-	golang.org/x/tools v0.2.0 // indirect
+	golang.org/x/mod v0.10.0 // indirect
+	golang.org/x/text v0.9.0 // indirect
+	golang.org/x/tools v0.9.1 // indirect
 	gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
diff --git a/go.sum b/go.sum
index a2375b03..3a777327 100644
--- a/go.sum
+++ b/go.sum
@@ -28,8 +28,10 @@ github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMo
 github.com/ghodss/yaml v1.0.0/go.mod h1:4dBDuWmgqj2HViK6kFavaiC9ZROes6MMH2rRYeMEF04=
 github.com/gliderlabs/ssh v0.1.1/go.mod h1:U7qILu1NlMHj9FlMhZLlkCdDnU1DBEAqr0aevW3Awn0=
 github.com/go-errors/errors v1.0.1/go.mod h1:f4zRHt4oKfwPJE5k8C9vpYG+aDHdBFUsgrm6/TyX73Q=
-github.com/go-task/slim-sprig v0.0.0-20210107165309-348f09dbbbc0 h1:p104kn46Q8WdvHunIJ9dAyjPVtrBPhSr3KT2yUst43I=
-github.com/go-task/slim-sprig v0.0.0-20210107165309-348f09dbbbc0/go.mod h1:fyg7847qk6SyHyPtNmDHnmrv/HOrqktSC+C9fM+CJOE=
+github.com/go-logr/logr v1.2.4 h1:g01GSCwiDw2xSZfjJ2/T9M+S6pFdcNtFYsp+Y43HYDQ=
+github.com/go-logr/logr v1.2.4/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
+github.com/go-task/slim-sprig v0.0.0-20230315185526-52ccab3ef572 h1:tfuBGBXKqDEevZMzYi5KSi8KkcZtzBcTgAUUtapy0OI=
+github.com/go-task/slim-sprig v0.0.0-20230315185526-52ccab3ef572/go.mod h1:9Pwr4B2jHnOSGXyyzV8ROjYa2ojvAY6HCGYYfMoC3Ls=
 github.com/gogo/protobuf v1.1.1/go.mod h1:r8qH/GZQm5c6nD/R0oafs1akxWv10x8SbQlK7atdtwQ=
 github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
 github.com/golang/lint v0.0.0-20180702182130-06c8688daad7/go.mod h1:tluoj9z5200jBnyusfRPU2LqT6J+DAorxEvtC7LHB+E=
@@ -39,11 +41,11 @@ github.com/golang/mock v1.6.0 h1:ErTB+efbowRARo13NNdxyJji2egdxLGQhRaY+DUumQc=
 github.com/golang/mock v1.6.0/go.mod h1:p6yTPP+5HYm5mzsMV8JkE6ZKdX+/wYM6Hr+LicevLPs=
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
-github.com/golang/protobuf v1.5.2 h1:ROPKBNFfQgOUMifHyP+KYbvpjbdoFNs+aK7DXlji0Tw=
+github.com/golang/protobuf v1.5.3 h1:KhyjKVUg7Usr/dYsdSqoFveMYd5ko72D+zANwlG1mmg=
 github.com/google/btree v0.0.0-20180813153112-4030bb1f1f0c/go.mod h1:lNA+9X1NB3Zf8V7Ke586lFgjr2dZNuvo3lPJSGZ5JPQ=
 github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=
-github.com/google/go-cmp v0.5.8 h1:e6P7q2lk1O+qJJb4BtCQXlK8vWEO8V1ZeuEdJNOqZyg=
-github.com/google/go-cmp v0.5.8/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
+github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/go-github v17.0.0+incompatible/go.mod h1:zLgOLi98H3fifZn+44m+umXrS52loVEgC2AApnigrVQ=
 github.com/google/go-querystring v1.0.0/go.mod h1:odCYkC5MyYFN7vkCjXpyrEuKhc/BUO6wN/zVPAxq5ck=
 github.com/google/martian v2.1.0+incompatible/go.mod h1:9I4somxYTbIHy5NJKHRl3wXiIaQGbYVAs8BPL6v8lEs=
@@ -74,10 +76,10 @@ github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd/go.mod h1:6dJ
 github.com/modern-go/reflect2 v1.0.1/go.mod h1:bx2lNnkwVCuqBIxFjflWJWanXIb3RllmbCylyMrvgv0=
 github.com/neelance/astrewrite v0.0.0-20160511093645-99348263ae86/go.mod h1:kHJEU3ofeGjhHklVoIGuVj85JJwZ6kWPaJwCIxgnFmo=
 github.com/neelance/sourcemap v0.0.0-20151028013722-8c68805598ab/go.mod h1:Qr6/a/Q4r9LP1IltGz7tA7iOK1WonHEYhu1HRBA7ZiM=
-github.com/onsi/ginkgo/v2 v2.2.0 h1:3ZNA3L1c5FYDFTTxbFeVGGD8jYvjYauHD30YgLxVsNI=
-github.com/onsi/ginkgo/v2 v2.2.0/go.mod h1:MEH45j8TBi6u9BMogfbp0stKC5cdGjumZj5Y7AG4VIk=
-github.com/onsi/gomega v1.20.1 h1:PA/3qinGoukvymdIDV8pii6tiZgC8kbmJO6Z5+b002Q=
-github.com/onsi/gomega v1.20.1/go.mod h1:DtrZpjmvpn2mPm4YWQa0/ALMDj9v4YxLgojwPeREyVo=
+github.com/onsi/ginkgo/v2 v2.9.5 h1:+6Hr4uxzP4XIUyAkg61dWBw8lb/gc4/X5luuxN/EC+Q=
+github.com/onsi/ginkgo/v2 v2.9.5/go.mod h1:tvAoo1QUJwNEU2ITftXTpR7R1RbCzoZUOs3RonqW57k=
+github.com/onsi/gomega v1.27.6 h1:ENqfyGeS5AX/rlXDd/ETokDz93u0YufY1Pgxuy/PvWE=
+github.com/onsi/gomega v1.27.6/go.mod h1:PIQNjfQwkP3aQAH7lf7j87O/5FiNr+ZR8+ipb+qQlhg=
 github.com/openzipkin/zipkin-go v0.1.1/go.mod h1:NtoC/o8u3JlF1lSlyPNswIbeQH9bJTmOf0Erfk+hxe8=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
@@ -120,8 +122,8 @@ github.com/sourcegraph/annotate v0.0.0-20160123013949-f4cad6c6324d/go.mod h1:Udh
 github.com/sourcegraph/syntaxhighlight v0.0.0-20170531221838-bd320f5d308e/go.mod h1:HuIsMU8RRBOtsCgI77wP899iHVBQpCmg4ErYMZB+2IA=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
-github.com/stretchr/testify v1.5.1 h1:nOGnQDM7FYENwehXlg/kFVnos3rEvtKTjRvOWSzb6H4=
-github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
+github.com/stretchr/testify v1.6.1 h1:hDPOHmpOpP40lSULcqw7IrRb/u7w6RpDC9399XyoNd0=
+github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/tarm/serial v0.0.0-20180830185346-98f6abe2eb07/go.mod h1:kDXzergiv9cbyO7IOYJZWg1U88JhDg3PB6klq9Hg2pA=
 github.com/viant/assertly v0.4.8/go.mod h1:aGifi++jvCrUaklKEKT0BU95igDNaqkvz+49uaYMPRU=
 github.com/viant/toolbox v0.24.0/go.mod h1:OxMCG57V0PXuIP2HNQrtJf2CjqdmbrOx5EkMILuUhzM=
@@ -142,8 +144,8 @@ golang.org/x/lint v0.0.0-20180702182130-06c8688daad7/go.mod h1:UVdnD1Gm6xHRNCYTk
 golang.org/x/lint v0.0.0-20181026193005-c67002cb31c3/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
 golang.org/x/lint v0.0.0-20190227174305-5b3e6a55c961/go.mod h1:wehouNa3lNwaWXcvxsM5YxQ5yQlVC4a0KAMCusXpPoU=
 golang.org/x/mod v0.4.2/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
-golang.org/x/mod v0.6.0 h1:b9gGHsz9/HhJ3HF5DHQytPpuwocVTChQJK3AvoLRD5I=
-golang.org/x/mod v0.6.0/go.mod h1:4mET923SAdbXp2ki8ey+zGs1SLqsuM2Y0uvdZR/fUNI=
+golang.org/x/mod v0.10.0 h1:lFO9qtOdlre5W1jxS3r/4szv2/6iXxScdzjoBMXNhYk=
+golang.org/x/mod v0.10.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
 golang.org/x/net v0.0.0-20180724234803-3673e40ba225/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20180826012351-8a410e7b638d/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20180906233101-161cd47e91fd/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
@@ -155,8 +157,8 @@ golang.org/x/net v0.0.0-20190313220215-9f648a60d977/go.mod h1:t9HGtf8HONx5eT2rtn
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20210405180319-a5a99cb37ef4/go.mod h1:p54w0d4576C0XHj96bSt6lcn1PtDYWL6XObtHCRCNQM=
-golang.org/x/net v0.7.0 h1:rJrUqqhjsgNp7KqAIc25s9pZnjU7TUcSY7HcVZjdn1g=
-golang.org/x/net v0.7.0/go.mod h1:2Tu9+aMcznHK/AK1HMvgo6xiTLG5rD5rZLDS+rp2Bjs=
+golang.org/x/net v0.10.0 h1:X2//UzNDwYmtCLn7To6G58Wr6f5ahEAQgKNzv9Y951M=
+golang.org/x/net v0.10.0/go.mod h1:0qNGK6F8kojg2nk9dLZ2mShWaEBan6FAoqfSigmmuDg=
 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/oauth2 v0.0.0-20181017192945-9dcd33a902f4/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/oauth2 v0.0.0-20181203162652-d668ce993890/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
@@ -168,8 +170,8 @@ golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20190227155943-e225da77a7e6/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=
-golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.2.0 h1:PUR+T4wwASmuSTYdKjYHI5TD22Wy5ogLU5qZCOLxBrI=
+golang.org/x/sync v0.2.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180909124046-d0be0721c37e/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20181029174526-d69651ed3497/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
@@ -180,14 +182,14 @@ golang.org/x/sys v0.0.0-20191204072324-ce4227a45e2e/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210330210617-4fbd30eecc44/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210510120138-977fb7262007/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.5.0 h1:MUK/U/4lj1t1oPg0HfuXDN/Z1wv31ZJ/YcPiGccS4DU=
-golang.org/x/sys v0.5.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.8.0 h1:EBmGv8NaZBZTWvrbjNoL6HVt+IVy3QDQpJs7VRIw3tU=
+golang.org/x/sys v0.8.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.1-0.20180807135948-17ff2d5776d2/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/text v0.7.0 h1:4BRB4x83lYWy72KwLD/qYDuTu7q9PjSagHvijDw7cLo=
-golang.org/x/text v0.7.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
+golang.org/x/text v0.9.0 h1:2sjJmO8cDvYveuX97RDLsxlyUxLl+GHoLxBiRdHllBE=
+golang.org/x/text v0.9.0/go.mod h1:e1OnstbJyHTd6l/uOt8jFFHp6TRDWZR/bV3emEE/zU8=
 golang.org/x/time v0.0.0-20180412165947-fbb02b2291d2/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/time v0.0.0-20181108054448-85acf8d2951c/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/tools v0.0.0-20180828015842-6cd1fcedba52/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
@@ -197,8 +199,8 @@ golang.org/x/tools v0.0.0-20190114222345-bf090417da8b/go.mod h1:n7NCudcB/nEzxVGm
 golang.org/x/tools v0.0.0-20190226205152-f727befe758c/go.mod h1:9Yl7xja0Znq3iFh3HoIrodX9oNMXvdceNzlUR8zjMvY=
 golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.1.1/go.mod h1:o0xws9oXOQQZyjljx8fwUC0k7L1pTE6eaCbjGeHmOkk=
-golang.org/x/tools v0.2.0 h1:G6AHpWxTMGY1KyEYoAQ5WTtIekUUvDNjan3ugu60JvE=
-golang.org/x/tools v0.2.0/go.mod h1:y4OqIKeOV/fWJetJ8bXPU1sEVniLMIyDAZWeHdV+NTA=
+golang.org/x/tools v0.9.1 h1:8WMNJAz3zrtPmnYC7ISf5dEn3MT0gY7jBJfw27yrrLo=
+golang.org/x/tools v0.9.1/go.mod h1:owI94Op576fPu3cIGQeHs3joujW/2Oc6MtlxbF5dfNc=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
@@ -225,7 +227,7 @@ gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8
 gopkg.in/inf.v0 v0.9.1/go.mod h1:cWUDdTG/fYaXco+Dcufb5Vnc6Gp2YChqWtbxRZE0mXw=
 gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
-gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 grpc.go4.org v0.0.0-20170609214715-11d0a25b4919/go.mod h1:77eQGdRu53HpSqPFJFmuJdjuHRquDANNeA4x7B8WQ9o=
diff --git a/http3/client.go b/http3/client.go
index 9c94a31e..c54de5ea 100644
--- a/http3/client.go
+++ b/http3/client.go
@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"net"
 	"net/http"
 	"strconv"
 	"sync"
@@ -92,6 +93,14 @@ func newClient(hostname string, tlsConf *tls.Config, opts *roundTripperOpts, con
 	} else {
 		tlsConf = tlsConf.Clone()
 	}
+	if tlsConf.ServerName == "" {
+		sni, _, err := net.SplitHostPort(hostname)
+		if err != nil {
+			// It's ok if net.SplitHostPort returns an error - it could be a hostname/IP address without a port.
+			sni = hostname
+		}
+		tlsConf.ServerName = sni
+	}
 	// Replace existing ALPNs by H3
 	tlsConf.NextProtos = []string{versionToALPN(conf.Versions[0])}
 
diff --git a/http3/roundtrip.go b/http3/roundtrip.go
index eef93c28..066b762b 100644
--- a/http3/roundtrip.go
+++ b/http3/roundtrip.go
@@ -17,9 +17,6 @@ import (
 	"github.com/quic-go/quic-go"
 )
 
-// declare this as a variable, such that we can it mock it in the tests
-var quicDialer = quic.DialEarly
-
 type roundTripCloser interface {
 	RoundTripOpt(*http.Request, RoundTripOpt) (*http.Response, error)
 	HandshakeComplete() bool
@@ -89,7 +86,7 @@ type RoundTripper struct {
 
 	newClient func(hostname string, tlsConf *tls.Config, opts *roundTripperOpts, conf *quic.Config, dialer dialFunc) (roundTripCloser, error) // so we can mock it in tests
 	clients   map[string]*roundTripCloserWithCount
-	udpConn   *net.UDPConn
+	transport *quic.Transport
 }
 
 // RoundTripOpt are options for the Transport.RoundTripOpt method.
@@ -187,11 +184,12 @@ func (r *RoundTripper) getClient(hostname string, onlyCached bool) (rtc *roundTr
 		}
 		dial := r.Dial
 		if dial == nil {
-			if r.udpConn == nil {
-				r.udpConn, err = net.ListenUDP("udp", nil)
+			if r.transport == nil {
+				udpConn, err := net.ListenUDP("udp", nil)
 				if err != nil {
 					return nil, false, err
 				}
+				r.transport = &quic.Transport{Conn: udpConn}
 			}
 			dial = r.makeDialer()
 		}
@@ -240,9 +238,14 @@ func (r *RoundTripper) Close() error {
 		}
 	}
 	r.clients = nil
-	if r.udpConn != nil {
-		r.udpConn.Close()
-		r.udpConn = nil
+	if r.transport != nil {
+		if err := r.transport.Close(); err != nil {
+			return err
+		}
+		if err := r.transport.Conn.Close(); err != nil {
+			return err
+		}
+		r.transport = nil
 	}
 	return nil
 }
@@ -282,7 +285,7 @@ func (r *RoundTripper) makeDialer() func(ctx context.Context, addr string, tlsCf
 		if err != nil {
 			return nil, err
 		}
-		return quicDialer(ctx, r.udpConn, udpAddr, tlsCfg, cfg)
+		return r.transport.DialEarly(ctx, udpAddr, tlsCfg, cfg)
 	}
 }
 
diff --git a/internal/ackhandler/sent_packet_handler.go b/internal/ackhandler/sent_packet_handler.go
index 732bbc3a..550dc74d 100644
--- a/internal/ackhandler/sent_packet_handler.go
+++ b/internal/ackhandler/sent_packet_handler.go
@@ -234,11 +234,31 @@ func (h *sentPacketHandler) SentPacket(p *Packet) {
 	if h.perspective == protocol.PerspectiveClient && p.EncryptionLevel == protocol.EncryptionHandshake && h.initialPackets != nil {
 		h.dropPackets(protocol.EncryptionInitial)
 	}
-	isAckEliciting := h.sentPacketImpl(p)
+
+	pnSpace := h.getPacketNumberSpace(p.EncryptionLevel)
+	if h.logger.Debug() && pnSpace.history.HasOutstandingPackets() {
+		for pn := utils.Max(0, pnSpace.largestSent+1); pn < p.PacketNumber; pn++ {
+			h.logger.Debugf("Skipping packet number %d", pn)
+		}
+	}
+
+	pnSpace.largestSent = p.PacketNumber
+	isAckEliciting := len(p.Frames) > 0
+
 	if isAckEliciting {
-		h.getPacketNumberSpace(p.EncryptionLevel).history.SentAckElicitingPacket(p)
+		pnSpace.lastAckElicitingPacketTime = p.SendTime
+		p.includedInBytesInFlight = true
+		h.bytesInFlight += p.Length
+		if h.numProbesToSend > 0 {
+			h.numProbesToSend--
+		}
+	}
+	h.congestion.OnPacketSent(p.SendTime, h.bytesInFlight, p.PacketNumber, p.Length, isAckEliciting)
+
+	if isAckEliciting {
+		pnSpace.history.SentAckElicitingPacket(p)
 	} else {
-		h.getPacketNumberSpace(p.EncryptionLevel).history.SentNonAckElicitingPacket(p.PacketNumber, p.EncryptionLevel, p.SendTime)
+		pnSpace.history.SentNonAckElicitingPacket(p.PacketNumber, p.EncryptionLevel, p.SendTime)
 		putPacket(p)
 		p = nil //nolint:ineffassign // This is just to be on the safe side.
 	}
@@ -263,31 +283,6 @@ func (h *sentPacketHandler) getPacketNumberSpace(encLevel protocol.EncryptionLev
 	}
 }
 
-func (h *sentPacketHandler) sentPacketImpl(packet *Packet) bool /* is ack-eliciting */ {
-	pnSpace := h.getPacketNumberSpace(packet.EncryptionLevel)
-
-	if h.logger.Debug() && pnSpace.history.HasOutstandingPackets() {
-		for p := utils.Max(0, pnSpace.largestSent+1); p < packet.PacketNumber; p++ {
-			h.logger.Debugf("Skipping packet number %d", p)
-		}
-	}
-
-	pnSpace.largestSent = packet.PacketNumber
-	isAckEliciting := len(packet.Frames) > 0
-
-	if isAckEliciting {
-		pnSpace.lastAckElicitingPacketTime = packet.SendTime
-		packet.includedInBytesInFlight = true
-		h.bytesInFlight += packet.Length
-		if h.numProbesToSend > 0 {
-			h.numProbesToSend--
-		}
-	}
-	h.congestion.OnPacketSent(packet.SendTime, h.bytesInFlight, packet.PacketNumber, packet.Length, isAckEliciting)
-
-	return isAckEliciting
-}
-
 func (h *sentPacketHandler) ReceivedAck(ack *wire.AckFrame, encLevel protocol.EncryptionLevel, rcvTime time.Time) (bool /* contained 1-RTT packet */, error) {
 	pnSpace := h.getPacketNumberSpace(encLevel)
 
diff --git a/internal/protocol/protocol.go b/internal/protocol/protocol.go
index 8241e274..93ad96cc 100644
--- a/internal/protocol/protocol.go
+++ b/internal/protocol/protocol.go
@@ -77,6 +77,9 @@ const MinConnectionIDLenInitial = 8
 // DefaultAckDelayExponent is the default ack delay exponent
 const DefaultAckDelayExponent = 3
 
+// DefaultActiveConnectionIDLimit is the default active connection ID limit
+const DefaultActiveConnectionIDLimit = 2
+
 // MaxAckDelayExponent is the maximum ack delay exponent
 const MaxAckDelayExponent = 20
 
diff --git a/internal/utils/ringbuffer/ringbuffer.go b/internal/utils/ringbuffer/ringbuffer.go
new file mode 100644
index 00000000..81a5ad44
--- /dev/null
+++ b/internal/utils/ringbuffer/ringbuffer.go
@@ -0,0 +1,86 @@
+package ringbuffer
+
+// A RingBuffer is a ring buffer.
+// It acts as a heap that doesn't cause any allocations.
+type RingBuffer[T any] struct {
+	ring             []T
+	headPos, tailPos int
+	full             bool
+}
+
+// Init preallocs a buffer with a certain size.
+func (r *RingBuffer[T]) Init(size int) {
+	r.ring = make([]T, size)
+}
+
+// Len returns the number of elements in the ring buffer.
+func (r *RingBuffer[T]) Len() int {
+	if r.full {
+		return len(r.ring)
+	}
+	if r.tailPos >= r.headPos {
+		return r.tailPos - r.headPos
+	}
+	return r.tailPos - r.headPos + len(r.ring)
+}
+
+// Empty says if the ring buffer is empty.
+func (r *RingBuffer[T]) Empty() bool {
+	return !r.full && r.headPos == r.tailPos
+}
+
+// PushBack adds a new element.
+// If the ring buffer is full, its capacity is increased first.
+func (r *RingBuffer[T]) PushBack(t T) {
+	if r.full || len(r.ring) == 0 {
+		r.grow()
+	}
+	r.ring[r.tailPos] = t
+	r.tailPos++
+	if r.tailPos == len(r.ring) {
+		r.tailPos = 0
+	}
+	if r.tailPos == r.headPos {
+		r.full = true
+	}
+}
+
+// PopFront returns the next element.
+// It must not be called when the buffer is empty, that means that
+// callers might need to check if there are elements in the buffer first.
+func (r *RingBuffer[T]) PopFront() T {
+	if r.Empty() {
+		panic("github.com/quic-go/quic-go/internal/utils/ringbuffer: pop from an empty queue")
+	}
+	r.full = false
+	t := r.ring[r.headPos]
+	r.ring[r.headPos] = *new(T)
+	r.headPos++
+	if r.headPos == len(r.ring) {
+		r.headPos = 0
+	}
+	return t
+}
+
+// Grow the maximum size of the queue.
+// This method assume the queue is full.
+func (r *RingBuffer[T]) grow() {
+	oldRing := r.ring
+	newSize := len(oldRing) * 2
+	if newSize == 0 {
+		newSize = 1
+	}
+	r.ring = make([]T, newSize)
+	headLen := copy(r.ring, oldRing[r.headPos:])
+	copy(r.ring[headLen:], oldRing[:r.headPos])
+	r.headPos, r.tailPos, r.full = 0, len(oldRing), false
+}
+
+// Clear removes all elements.
+func (r *RingBuffer[T]) Clear() {
+	var zeroValue T
+	for i := range r.ring {
+		r.ring[i] = zeroValue
+	}
+	r.headPos, r.tailPos, r.full = 0, 0, false
+}
diff --git a/internal/utils/rtt_stats.go b/internal/utils/rtt_stats.go
index 527539e1..2cd9a191 100644
--- a/internal/utils/rtt_stats.go
+++ b/internal/utils/rtt_stats.go
@@ -103,8 +103,12 @@ func (r *RTTStats) SetMaxAckDelay(mad time.Duration) {
 // SetInitialRTT sets the initial RTT.
 // It is used during the 0-RTT handshake when restoring the RTT stats from the session state.
 func (r *RTTStats) SetInitialRTT(t time.Duration) {
+	// On the server side, by the time we get to process the session ticket,
+	// we might already have obtained an RTT measurement.
+	// This can happen if we received the ClientHello in multiple pieces, and one of those pieces was lost.
+	// Discard the restored value. A fresh measurement is always better.
 	if r.hasMeasurement {
-		panic("initial RTT set after first measurement")
+		return
 	}
 	r.smoothedRTT = t
 	r.latestRTT = t
diff --git a/internal/wire/ack_frame.go b/internal/wire/ack_frame.go
index f145c8b4..2f816c78 100644
--- a/internal/wire/ack_frame.go
+++ b/internal/wire/ack_frame.go
@@ -90,13 +90,22 @@ func parseAckFrame(r *bytes.Reader, typ uint64, ackDelayExponent uint8, _ protoc
 		return nil, errInvalidAckRanges
 	}
 
-	// parse (and skip) the ECN section
 	if ecn {
-		for i := 0; i < 3; i++ {
-			if _, err := quicvarint.Read(r); err != nil {
-				return nil, err
-			}
+		ect0, err := quicvarint.Read(r)
+		if err != nil {
+			return nil, err
+		}
+		frame.ECT0 = ect0
+		ect1, err := quicvarint.Read(r)
+		if err != nil {
+			return nil, err
+		}
+		frame.ECT1 = ect1
+		ecnce, err := quicvarint.Read(r)
+		if err != nil {
+			return nil, err
 		}
+		frame.ECNCE = ecnce
 	}
 
 	return frame, nil
diff --git a/internal/wire/header.go b/internal/wire/header.go
index 6e8d4f9f..37f48cce 100644
--- a/internal/wire/header.go
+++ b/internal/wire/header.go
@@ -13,8 +13,6 @@ import (
 )
 
 // ParseConnectionID parses the destination connection ID of a packet.
-// It uses the data slice for the connection ID.
-// That means that the connection ID must not be used after the packet buffer is released.
 func ParseConnectionID(data []byte, shortHeaderConnIDLen int) (protocol.ConnectionID, error) {
 	if len(data) == 0 {
 		return protocol.ConnectionID{}, io.EOF
diff --git a/internal/wire/transport_parameters.go b/internal/wire/transport_parameters.go
index 8eb4cf46..dc1f2b95 100644
--- a/internal/wire/transport_parameters.go
+++ b/internal/wire/transport_parameters.go
@@ -118,6 +118,7 @@ func (p *TransportParameters) unmarshal(r *bytes.Reader, sentBy protocol.Perspec
 	var (
 		readOriginalDestinationConnectionID bool
 		readInitialSourceConnectionID       bool
+		readActiveConnectionIDLimit         bool
 	)
 
 	p.AckDelayExponent = protocol.DefaultAckDelayExponent
@@ -139,6 +140,9 @@ func (p *TransportParameters) unmarshal(r *bytes.Reader, sentBy protocol.Perspec
 		}
 		parameterIDs = append(parameterIDs, paramID)
 		switch paramID {
+		case activeConnectionIDLimitParameterID:
+			readActiveConnectionIDLimit = true
+			fallthrough
 		case maxIdleTimeoutParameterID,
 			maxUDPPayloadSizeParameterID,
 			initialMaxDataParameterID,
@@ -148,7 +152,6 @@ func (p *TransportParameters) unmarshal(r *bytes.Reader, sentBy protocol.Perspec
 			initialMaxStreamsBidiParameterID,
 			initialMaxStreamsUniParameterID,
 			maxAckDelayParameterID,
-			activeConnectionIDLimitParameterID,
 			maxDatagramFrameSizeParameterID,
 			ackDelayExponentParameterID:
 			if err := p.readNumericTransportParameter(r, paramID, int(paramLen)); err != nil {
@@ -196,6 +199,9 @@ func (p *TransportParameters) unmarshal(r *bytes.Reader, sentBy protocol.Perspec
 		}
 	}
 
+	if !readActiveConnectionIDLimit {
+		p.ActiveConnectionIDLimit = protocol.DefaultActiveConnectionIDLimit
+	}
 	if !fromSessionTicket {
 		if sentBy == protocol.PerspectiveServer && !readOriginalDestinationConnectionID {
 			return errors.New("missing original_destination_connection_id")
@@ -402,7 +408,9 @@ func (p *TransportParameters) Marshal(pers protocol.Perspective) []byte {
 		}
 	}
 	// active_connection_id_limit
-	b = p.marshalVarintParam(b, activeConnectionIDLimitParameterID, p.ActiveConnectionIDLimit)
+	if p.ActiveConnectionIDLimit != protocol.DefaultActiveConnectionIDLimit {
+		b = p.marshalVarintParam(b, activeConnectionIDLimitParameterID, p.ActiveConnectionIDLimit)
+	}
 	// initial_source_connection_id
 	b = quicvarint.Append(b, uint64(initialSourceConnectionIDParameterID))
 	b = quicvarint.Append(b, uint64(p.InitialSourceConnectionID.Len()))
diff --git a/packet_packer.go b/packet_packer.go
index 14befd46..180a03e1 100644
--- a/packet_packer.go
+++ b/packet_packer.go
@@ -417,7 +417,7 @@ func (p *packetPacker) PackCoalescedPacket(onlyAck bool, v protocol.VersionNumbe
 			if oneRTTPayload.length > 0 {
 				size += p.shortHeaderPacketLength(connID, oneRTTPacketNumberLen, oneRTTPayload) + protocol.ByteCount(oneRTTSealer.Overhead())
 			}
-		} else if p.perspective == protocol.PerspectiveClient { // 0-RTT
+		} else if p.perspective == protocol.PerspectiveClient && !onlyAck { // 0-RTT packets can't contain ACK frames
 			var err error
 			zeroRTTSealer, err = p.cryptoSetup.Get0RTTSealer()
 			if err != nil && err != handshake.ErrKeysDropped && err != handshake.ErrKeysNotYetAvailable {
diff --git a/server.go b/server.go
index f5b04549..4043c58c 100644
--- a/server.go
+++ b/server.go
@@ -98,10 +98,12 @@ type baseServer struct {
 		protocol.VersionNumber,
 	) quicConn
 
-	serverError error
-	errorChan   chan struct{}
-	closed      bool
-	running     chan struct{} // closed as soon as run() returns
+	serverError             error
+	errorChan               chan struct{}
+	closed                  bool
+	running                 chan struct{} // closed as soon as run() returns
+	versionNegotiationQueue chan *receivedPacket
+	invalidTokenQueue       chan *receivedPacket
 
 	connQueue    chan quicConn
 	connQueueLen int32 // to be used as an atomic
@@ -229,26 +231,29 @@ func newServer(
 		return nil, err
 	}
 	s := &baseServer{
-		conn:             conn,
-		tlsConf:          tlsConf,
-		config:           config,
-		tokenGenerator:   tokenGenerator,
-		connIDGenerator:  connIDGenerator,
-		connHandler:      connHandler,
-		connQueue:        make(chan quicConn),
-		errorChan:        make(chan struct{}),
-		running:          make(chan struct{}),
-		receivedPackets:  make(chan *receivedPacket, protocol.MaxServerUnprocessedPackets),
-		newConn:          newConnection,
-		tracer:           tracer,
-		logger:           utils.DefaultLogger.WithPrefix("server"),
-		acceptEarlyConns: acceptEarly,
-		onClose:          onClose,
+		conn:                    conn,
+		tlsConf:                 tlsConf,
+		config:                  config,
+		tokenGenerator:          tokenGenerator,
+		connIDGenerator:         connIDGenerator,
+		connHandler:             connHandler,
+		connQueue:               make(chan quicConn),
+		errorChan:               make(chan struct{}),
+		running:                 make(chan struct{}),
+		receivedPackets:         make(chan *receivedPacket, protocol.MaxServerUnprocessedPackets),
+		versionNegotiationQueue: make(chan *receivedPacket, 4),
+		invalidTokenQueue:       make(chan *receivedPacket, 4),
+		newConn:                 newConnection,
+		tracer:                  tracer,
+		logger:                  utils.DefaultLogger.WithPrefix("server"),
+		acceptEarlyConns:        acceptEarly,
+		onClose:                 onClose,
 	}
 	if acceptEarly {
 		s.zeroRTTQueues = map[protocol.ConnectionID]*zeroRTTQueue{}
 	}
 	go s.run()
+	go s.runSendQueue()
 	s.logger.Debugf("Listening for %s connections on %s", conn.LocalAddr().Network(), conn.LocalAddr().String())
 	return s, nil
 }
@@ -272,6 +277,19 @@ func (s *baseServer) run() {
 	}
 }
 
+func (s *baseServer) runSendQueue() {
+	for {
+		select {
+		case <-s.running:
+			return
+		case p := <-s.versionNegotiationQueue:
+			s.maybeSendVersionNegotiationPacket(p)
+		case p := <-s.invalidTokenQueue:
+			s.maybeSendInvalidToken(p)
+		}
+	}
+}
+
 // Accept returns connections that already completed the handshake.
 // It is only valid if acceptEarlyConns is false.
 func (s *baseServer) Accept(ctx context.Context) (Connection, error) {
@@ -353,27 +371,28 @@ func (s *baseServer) handlePacketImpl(p *receivedPacket) bool /* is the buffer s
 		panic(fmt.Sprintf("misrouted packet: %#v", p.data))
 	}
 	v, err := wire.ParseVersion(p.data)
+	// drop the packet if we failed to parse the protocol version
+	if err != nil {
+		s.logger.Debugf("Dropping a packet with an unknown version")
+		if s.tracer != nil {
+			s.tracer.DroppedPacket(p.remoteAddr, logging.PacketTypeNotDetermined, p.Size(), logging.PacketDropUnexpectedPacket)
+		}
+		return false
+	}
 	// send a Version Negotiation Packet if the client is speaking a different protocol version
-	if err != nil || !protocol.IsSupportedVersion(s.config.Versions, v) {
-		if err != nil || p.Size() < protocol.MinUnknownVersionPacketSize {
-			s.logger.Debugf("Dropping a packet with an unknown version that is too small (%d bytes)", p.Size())
-			if s.tracer != nil {
-				s.tracer.DroppedPacket(p.remoteAddr, logging.PacketTypeNotDetermined, p.Size(), logging.PacketDropUnexpectedPacket)
-			}
+	if !protocol.IsSupportedVersion(s.config.Versions, v) {
+		if s.config.DisableVersionNegotiationPackets {
 			return false
 		}
-		_, src, dest, err := wire.ParseArbitraryLenConnectionIDs(p.data)
-		if err != nil { // should never happen
-			s.logger.Debugf("Dropping a packet with an unknown version for which we failed to parse connection IDs")
+
+		if p.Size() < protocol.MinUnknownVersionPacketSize {
+			s.logger.Debugf("Dropping a packet with an unsupported version number %d that is too small (%d bytes)", v, p.Size())
 			if s.tracer != nil {
 				s.tracer.DroppedPacket(p.remoteAddr, logging.PacketTypeNotDetermined, p.Size(), logging.PacketDropUnexpectedPacket)
 			}
 			return false
 		}
-		if !s.config.DisableVersionNegotiationPackets {
-			go s.sendVersionNegotiationPacket(p.remoteAddr, src, dest, p.info.OOB(), v)
-		}
-		return false
+		return s.enqueueVersionNegotiationPacket(p)
 	}
 
 	if wire.Is0RTTPacket(p.data) {
@@ -557,12 +576,7 @@ func (s *baseServer) handleInitialImpl(p *receivedPacket, hdr *wire.Header) erro
 			// For Retry tokens, we send an INVALID_ERROR if
 			// * the token is too old, or
 			// * the token is invalid, in case of a retry token.
-			go func() {
-				defer p.buffer.Release()
-				if err := s.maybeSendInvalidToken(p, hdr); err != nil {
-					s.logger.Debugf("Error sending INVALID_TOKEN error: %s", err)
-				}
-			}()
+			s.enqueueInvalidToken(p)
 			return nil
 		}
 	}
@@ -730,7 +744,27 @@ func (s *baseServer) sendRetry(remoteAddr net.Addr, hdr *wire.Header, info *pack
 	return err
 }
 
-func (s *baseServer) maybeSendInvalidToken(p *receivedPacket, hdr *wire.Header) error {
+func (s *baseServer) enqueueInvalidToken(p *receivedPacket) {
+	select {
+	case s.invalidTokenQueue <- p:
+	default:
+		// it's fine to drop INVALID_TOKEN packets when we are busy
+		p.buffer.Release()
+	}
+}
+
+func (s *baseServer) maybeSendInvalidToken(p *receivedPacket) {
+	defer p.buffer.Release()
+
+	hdr, _, _, err := wire.ParsePacket(p.data)
+	if err != nil {
+		if s.tracer != nil {
+			s.tracer.DroppedPacket(p.remoteAddr, logging.PacketTypeNotDetermined, p.Size(), logging.PacketDropHeaderParseError)
+		}
+		s.logger.Debugf("Error parsing packet: %s", err)
+		return
+	}
+
 	// Only send INVALID_TOKEN if we can unprotect the packet.
 	// This makes sure that we won't send it for packets that were corrupted.
 	sealer, opener := handshake.NewInitialAEAD(hdr.DestConnectionID, protocol.PerspectiveServer, hdr.Version)
@@ -740,21 +774,21 @@ func (s *baseServer) maybeSendInvalidToken(p *receivedPacket, hdr *wire.Header)
 		if s.tracer != nil {
 			s.tracer.DroppedPacket(p.remoteAddr, logging.PacketTypeInitial, p.Size(), logging.PacketDropHeaderParseError)
 		}
-		// don't return the error here. Just drop the packet.
-		return nil
+		return
 	}
 	hdrLen := extHdr.ParsedLen()
 	if _, err := opener.Open(data[hdrLen:hdrLen], data[hdrLen:], extHdr.PacketNumber, data[:hdrLen]); err != nil {
-		// don't return the error here. Just drop the packet.
 		if s.tracer != nil {
 			s.tracer.DroppedPacket(p.remoteAddr, logging.PacketTypeInitial, p.Size(), logging.PacketDropPayloadDecryptError)
 		}
-		return nil
+		return
 	}
 	if s.logger.Debug() {
 		s.logger.Debugf("Client sent an invalid retry token. Sending INVALID_TOKEN to %s.", p.remoteAddr)
 	}
-	return s.sendError(p.remoteAddr, hdr, sealer, qerr.InvalidToken, p.info)
+	if err := s.sendError(p.remoteAddr, hdr, sealer, qerr.InvalidToken, p.info); err != nil {
+		s.logger.Debugf("Error sending INVALID_TOKEN error: %s", err)
+	}
 }
 
 func (s *baseServer) sendConnectionRefused(remoteAddr net.Addr, hdr *wire.Header, info *packetInfo) error {
@@ -807,14 +841,41 @@ func (s *baseServer) sendError(remoteAddr net.Addr, hdr *wire.Header, sealer han
 	return err
 }
 
-func (s *baseServer) sendVersionNegotiationPacket(remote net.Addr, src, dest protocol.ArbitraryLenConnectionID, oob []byte, v protocol.VersionNumber) {
+func (s *baseServer) enqueueVersionNegotiationPacket(p *receivedPacket) (bufferInUse bool) {
+	select {
+	case s.versionNegotiationQueue <- p:
+		return true
+	default:
+		// it's fine to not send version negotiation packets when we are busy
+	}
+	return false
+}
+
+func (s *baseServer) maybeSendVersionNegotiationPacket(p *receivedPacket) {
+	defer p.buffer.Release()
+
+	v, err := wire.ParseVersion(p.data)
+	if err != nil {
+		s.logger.Debugf("failed to parse version for sending version negotiation packet: %s", err)
+		return
+	}
+
+	_, src, dest, err := wire.ParseArbitraryLenConnectionIDs(p.data)
+	if err != nil { // should never happen
+		s.logger.Debugf("Dropping a packet with an unknown version for which we failed to parse connection IDs")
+		if s.tracer != nil {
+			s.tracer.DroppedPacket(p.remoteAddr, logging.PacketTypeNotDetermined, p.Size(), logging.PacketDropUnexpectedPacket)
+		}
+		return
+	}
+
 	s.logger.Debugf("Client offered version %s, sending Version Negotiation", v)
 
 	data := wire.ComposeVersionNegotiation(dest, src, s.config.Versions)
 	if s.tracer != nil {
-		s.tracer.SentVersionNegotiationPacket(remote, src, dest, s.config.Versions)
+		s.tracer.SentVersionNegotiationPacket(p.remoteAddr, src, dest, s.config.Versions)
 	}
-	if _, err := s.conn.WritePacket(data, remote, oob); err != nil {
+	if _, err := s.conn.WritePacket(data, p.remoteAddr, p.info.OOB()); err != nil {
 		s.logger.Debugf("Error sending Version Negotiation: %s", err)
 	}
 }


Test patch:
diff --git a/client_test.go b/client_test.go
index 23847329..50346891 100644
--- a/client_test.go
+++ b/client_test.go
@@ -293,7 +293,7 @@ var _ = Describe("Client", func() {
 				conn := NewMockQUICConn(mockCtrl)
 				conn.EXPECT().run()
 				conn.EXPECT().HandshakeComplete().Return(make(chan struct{}))
-				conn.EXPECT().destroy(gomock.Any())
+				conn.EXPECT().destroy(gomock.Any()).MaxTimes(1)
 				close(done)
 				return conn
 			}
diff --git a/http3/client_test.go b/http3/client_test.go
index d0f68295..2bc00884 100644
--- a/http3/client_test.go
+++ b/http3/client_test.go
@@ -90,6 +90,22 @@ var _ = Describe("Client", func() {
 		Expect(dialAddrCalled).To(BeTrue())
 	})
 
+	It("sets the ServerName in the tls.Config, if not set", func() {
+		const host = "foo.bar"
+		dialCalled := false
+		dialFunc := func(ctx context.Context, addr string, tlsCfg *tls.Config, cfg *quic.Config) (quic.EarlyConnection, error) {
+			Expect(tlsCfg.ServerName).To(Equal(host))
+			dialCalled = true
+			return nil, errors.New("test done")
+		}
+		client, err := newClient(host, nil, &roundTripperOpts{}, nil, dialFunc)
+		Expect(err).ToNot(HaveOccurred())
+		req, err := http.NewRequest("GET", "https://foo.bar", nil)
+		Expect(err).ToNot(HaveOccurred())
+		client.RoundTripOpt(req, RoundTripOpt{})
+		Expect(dialCalled).To(BeTrue())
+	})
+
 	It("uses the TLS config and QUIC config", func() {
 		tlsConf := &tls.Config{
 			ServerName: "foo.bar",
diff --git a/http3/roundtrip_test.go b/http3/roundtrip_test.go
index 8e859de5..0c219db7 100644
--- a/http3/roundtrip_test.go
+++ b/http3/roundtrip_test.go
@@ -6,13 +6,11 @@ import (
 	"crypto/tls"
 	"errors"
 	"io"
-	"net"
 	"net/http"
 	"sync/atomic"
 	"time"
 
 	"github.com/quic-go/quic-go"
-	mockquic "github.com/quic-go/quic-go/internal/mocks/quic"
 	"github.com/quic-go/quic-go/internal/qerr"
 
 	"github.com/golang/mock/gomock"
@@ -368,66 +366,4 @@ var _ = Describe("RoundTripper", func() {
 			Expect(len(rt.clients)).To(Equal(0))
 		})
 	})
-
-	Context("reusing udpconn", func() {
-		var originalDialer func(ctx context.Context, pconn net.PacketConn, remoteAddr net.Addr, tlsConf *tls.Config, config *quic.Config) (quic.EarlyConnection, error)
-		var req1, req2 *http.Request
-
-		BeforeEach(func() {
-			var err error
-			originalDialer = quicDialer
-			req1, err = http.NewRequest("GET", "https://site1.com", nil)
-			Expect(err).ToNot(HaveOccurred())
-			req2, err = http.NewRequest("GET", "https://site2.com", nil)
-			Expect(err).ToNot(HaveOccurred())
-			Expect(req1.Host).ToNot(Equal(req2.Host))
-		})
-
-		AfterEach(func() {
-			quicDialer = originalDialer
-			err := rt.Close()
-			Expect(err).ToNot(HaveOccurred())
-		})
-
-		It("creates udpconn at first request", func() {
-			Expect(rt.udpConn).To(BeNil())
-			rt.newClient = func(hostname string, tlsConf *tls.Config, opts *roundTripperOpts, conf *quic.Config, dialer dialFunc) (roundTripCloser, error) {
-				cl := NewMockRoundTripCloser(mockCtrl)
-				cl.EXPECT().RoundTripOpt(gomock.Any(), gomock.Any())
-				cl.EXPECT().Close()
-				return cl, nil
-			}
-			_, err := rt.RoundTrip(req1)
-			Expect(err).ToNot(HaveOccurred())
-			Expect(rt.udpConn).ToNot(BeNil())
-		})
-
-		It("reuses udpconn in different hosts", func() {
-			Expect(rt.udpConn).To(BeNil())
-			quicDialer = func(_ context.Context, pconn net.PacketConn, _ net.Addr, _ *tls.Config, _ *quic.Config) (quic.EarlyConnection, error) {
-				conn := mockquic.NewMockEarlyConnection(mockCtrl)
-				conn.EXPECT().LocalAddr().Return(pconn.LocalAddr())
-				return conn, nil
-			}
-			rt.newClient = func(hostname string, tlsConf *tls.Config, _ *roundTripperOpts, conf *quic.Config, dialer dialFunc) (roundTripCloser, error) {
-				cl := NewMockRoundTripCloser(mockCtrl)
-				cl.EXPECT().RoundTripOpt(gomock.Any(), gomock.Any()).DoAndReturn(func(_ *http.Request, _ RoundTripOpt) (*http.Response, error) {
-					header := make(http.Header)
-					quicConn, err := dialer(context.Background(), hostname, tlsConf, conf)
-					Expect(err).ToNot(HaveOccurred())
-					header.Set("udpconn", quicConn.LocalAddr().String())
-					return &http.Response{Header: header}, nil
-				})
-				cl.EXPECT().Close()
-				return cl, nil
-			}
-			rsp1, err := rt.RoundTrip(req1)
-			Expect(err).ToNot(HaveOccurred())
-			Expect(rsp1.Header.Get("udpconn")).ToNot(Equal(""))
-			rsp2, err := rt.RoundTrip(req2)
-			Expect(err).ToNot(HaveOccurred())
-			Expect(rsp2.Header.Get("udpconn")).ToNot(Equal(""))
-			Expect(rsp1.Header.Get("udpconn")).To(Equal(rsp2.Header.Get("udpconn")))
-		})
-	})
 })
diff --git a/integrationtests/gomodvendor/go.sum b/integrationtests/gomodvendor/go.sum
index 9ba8661b..c7b64468 100644
--- a/integrationtests/gomodvendor/go.sum
+++ b/integrationtests/gomodvendor/go.sum
@@ -28,8 +28,12 @@ github.com/fsnotify/fsnotify v1.4.9/go.mod h1:znqG4EE+3YCdAaPaxE2ZRY/06pZUdp0tY4
 github.com/ghodss/yaml v1.0.0/go.mod h1:4dBDuWmgqj2HViK6kFavaiC9ZROes6MMH2rRYeMEF04=
 github.com/gliderlabs/ssh v0.1.1/go.mod h1:U7qILu1NlMHj9FlMhZLlkCdDnU1DBEAqr0aevW3Awn0=
 github.com/go-errors/errors v1.0.1/go.mod h1:f4zRHt4oKfwPJE5k8C9vpYG+aDHdBFUsgrm6/TyX73Q=
-github.com/go-task/slim-sprig v0.0.0-20210107165309-348f09dbbbc0 h1:p104kn46Q8WdvHunIJ9dAyjPVtrBPhSr3KT2yUst43I=
+github.com/go-logr/logr v1.2.3/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
+github.com/go-logr/logr v1.2.4 h1:g01GSCwiDw2xSZfjJ2/T9M+S6pFdcNtFYsp+Y43HYDQ=
+github.com/go-logr/logr v1.2.4/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
 github.com/go-task/slim-sprig v0.0.0-20210107165309-348f09dbbbc0/go.mod h1:fyg7847qk6SyHyPtNmDHnmrv/HOrqktSC+C9fM+CJOE=
+github.com/go-task/slim-sprig v0.0.0-20230315185526-52ccab3ef572 h1:tfuBGBXKqDEevZMzYi5KSi8KkcZtzBcTgAUUtapy0OI=
+github.com/go-task/slim-sprig v0.0.0-20230315185526-52ccab3ef572/go.mod h1:9Pwr4B2jHnOSGXyyzV8ROjYa2ojvAY6HCGYYfMoC3Ls=
 github.com/gogo/protobuf v1.1.1/go.mod h1:r8qH/GZQm5c6nD/R0oafs1akxWv10x8SbQlK7atdtwQ=
 github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
 github.com/golang/lint v0.0.0-20180702182130-06c8688daad7/go.mod h1:tluoj9z5200jBnyusfRPU2LqT6J+DAorxEvtC7LHB+E=
@@ -46,16 +50,18 @@ github.com/golang/protobuf v1.4.0-rc.4.0.20200313231945-b860323f09d0/go.mod h1:W
 github.com/golang/protobuf v1.4.0/go.mod h1:jodUvKwWbYaEsadDk5Fwe5c77LiNKVO9IDvqG2KuDX0=
 github.com/golang/protobuf v1.4.2/go.mod h1:oDoupMAO8OvCJWAcko0GGGIgR6R6ocIYbsSw735rRwI=
 github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
-github.com/golang/protobuf v1.5.2 h1:ROPKBNFfQgOUMifHyP+KYbvpjbdoFNs+aK7DXlji0Tw=
 github.com/golang/protobuf v1.5.2/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiuN0vRsmY=
+github.com/golang/protobuf v1.5.3 h1:KhyjKVUg7Usr/dYsdSqoFveMYd5ko72D+zANwlG1mmg=
+github.com/golang/protobuf v1.5.3/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiuN0vRsmY=
 github.com/google/btree v0.0.0-20180813153112-4030bb1f1f0c/go.mod h1:lNA+9X1NB3Zf8V7Ke586lFgjr2dZNuvo3lPJSGZ5JPQ=
 github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=
 github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
-github.com/google/go-cmp v0.5.8 h1:e6P7q2lk1O+qJJb4BtCQXlK8vWEO8V1ZeuEdJNOqZyg=
 github.com/google/go-cmp v0.5.8/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
+github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/go-github v17.0.0+incompatible/go.mod h1:zLgOLi98H3fifZn+44m+umXrS52loVEgC2AApnigrVQ=
 github.com/google/go-querystring v1.0.0/go.mod h1:odCYkC5MyYFN7vkCjXpyrEuKhc/BUO6wN/zVPAxq5ck=
 github.com/google/martian v2.1.0+incompatible/go.mod h1:9I4somxYTbIHy5NJKHRl3wXiIaQGbYVAs8BPL6v8lEs=
@@ -93,14 +99,33 @@ github.com/onsi/ginkgo v1.16.4 h1:29JGrr5oVBm5ulCWet69zQkzWipVXIol6ygQUe/EzNc=
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@@ -143,8 +168,9 @@ github.com/sourcegraph/annotate v0.0.0-20160123013949-f4cad6c6324d/go.mod h1:Udh
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@@ -175,8 +201,12 @@ golang.org/x/mod v0.3.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
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 golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
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@@ -197,9 +227,14 @@ golang.org/x/net v0.0.0-20220225172249-27dd8689420f/go.mod h1:CfG3xpIq0wQ8r1q4Su
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-golang.org/x/net v0.7.0 h1:rJrUqqhjsgNp7KqAIc25s9pZnjU7TUcSY7HcVZjdn1g=
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 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/oauth2 v0.0.0-20181017192945-9dcd33a902f4/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/oauth2 v0.0.0-20181203162652-d668ce993890/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
@@ -214,6 +249,7 @@ golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
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@@ -239,14 +275,22 @@ golang.org/x/sys v0.0.0-20220422013727-9388b58f7150/go.mod h1:oPkhp1MJrh7nUepCBc
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@@ -254,8 +298,11 @@ golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
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-golang.org/x/text v0.7.0 h1:4BRB4x83lYWy72KwLD/qYDuTu7q9PjSagHvijDw7cLo=
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@@ -268,8 +315,12 @@ golang.org/x/tools v0.0.0-20201224043029-2b0845dc783e/go.mod h1:emZCQorbCU4vsT4f
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+golang.org/x/tools v0.4.0/go.mod h1:UE5sM2OK9E/d67R0ANs2xJizIymRP5gJU295PvKXxjQ=
+golang.org/x/tools v0.6.0/go.mod h1:Xwgl3UAJ/d3gWutnCtw505GrjyAbvKui8lOU390QaIU=
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+golang.org/x/tools v0.9.1/go.mod h1:owI94Op576fPu3cIGQeHs3joujW/2Oc6MtlxbF5dfNc=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
@@ -309,8 +360,8 @@ gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.4/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.3.0/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
-gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
 gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 grpc.go4.org v0.0.0-20170609214715-11d0a25b4919/go.mod h1:77eQGdRu53HpSqPFJFmuJdjuHRquDANNeA4x7B8WQ9o=
diff --git a/integrationtests/self/hotswap_test.go b/integrationtests/self/hotswap_test.go
index 6cd73079..ac75a494 100644
--- a/integrationtests/self/hotswap_test.go
+++ b/integrationtests/self/hotswap_test.go
@@ -61,6 +61,7 @@ var _ = Describe("HTTP3 Server hotswap test", func() {
 		mux1    *http.ServeMux
 		mux2    *http.ServeMux
 		client  *http.Client
+		rt      *http3.RoundTripper
 		server1 *http3.Server
 		server2 *http3.Server
 		ln      *listenerWrapper
@@ -97,17 +98,17 @@ var _ = Describe("HTTP3 Server hotswap test", func() {
 	})
 
 	AfterEach(func() {
+		Expect(rt.Close()).NotTo(HaveOccurred())
 		Expect(ln.Close()).NotTo(HaveOccurred())
 	})
 
 	BeforeEach(func() {
-		client = &http.Client{
-			Transport: &http3.RoundTripper{
-				TLSClientConfig:    getTLSClientConfig(),
-				DisableCompression: true,
-				QuicConfig:         getQuicConfig(&quic.Config{MaxIdleTimeout: 10 * time.Second}),
-			},
+		rt = &http3.RoundTripper{
+			TLSClientConfig:    getTLSClientConfig(),
+			DisableCompression: true,
+			QuicConfig:         getQuicConfig(&quic.Config{MaxIdleTimeout: 10 * time.Second}),
 		}
+		client = &http.Client{Transport: rt}
 	})
 
 	It("hotswap works", func() {
diff --git a/integrationtests/self/http_test.go b/integrationtests/self/http_test.go
index 29385aef..f8d563b9 100644
--- a/integrationtests/self/http_test.go
+++ b/integrationtests/self/http_test.go
@@ -40,6 +40,7 @@ var _ = Describe("HTTP tests", func() {
 	var (
 		mux            *http.ServeMux
 		client         *http.Client
+		rt             *http3.RoundTripper
 		server         *http3.Server
 		stoppedServing chan struct{}
 		port           string
@@ -77,6 +78,12 @@ var _ = Describe("HTTP tests", func() {
 			w.Write(body) // don't check the error here. Stream may be reset.
 		})
 
+		mux.HandleFunc("/remoteAddr", func(w http.ResponseWriter, r *http.Request) {
+			defer GinkgoRecover()
+			w.Header().Set("X-RemoteAddr", r.RemoteAddr)
+			w.WriteHeader(http.StatusOK)
+		})
+
 		server = &http3.Server{
 			Handler:    mux,
 			TLSConfig:  getTLSConfig(),
@@ -99,18 +106,18 @@ var _ = Describe("HTTP tests", func() {
 	})
 
 	AfterEach(func() {
+		Expect(rt.Close()).NotTo(HaveOccurred())
 		Expect(server.Close()).NotTo(HaveOccurred())
 		Eventually(stoppedServing).Should(BeClosed())
 	})
 
 	BeforeEach(func() {
-		client = &http.Client{
-			Transport: &http3.RoundTripper{
-				TLSClientConfig:    getTLSClientConfig(),
-				DisableCompression: true,
-				QuicConfig:         getQuicConfig(&quic.Config{MaxIdleTimeout: 10 * time.Second}),
-			},
+		rt = &http3.RoundTripper{
+			TLSClientConfig:    getTLSClientConfigWithoutServerName(),
+			DisableCompression: true,
+			QuicConfig:         getQuicConfig(&quic.Config{MaxIdleTimeout: 10 * time.Second}),
 		}
+		client = &http.Client{Transport: rt}
 	})
 
 	It("downloads a hello", func() {
@@ -122,6 +129,20 @@ var _ = Describe("HTTP tests", func() {
 		Expect(string(body)).To(Equal("Hello, World!\n"))
 	})
 
+	It("requests to different servers with the same udpconn", func() {
+		resp, err := client.Get("https://localhost:" + port + "/remoteAddr")
+		Expect(err).ToNot(HaveOccurred())
+		Expect(resp.StatusCode).To(Equal(200))
+		addr1 := resp.Header.Get("X-RemoteAddr")
+		Expect(addr1).ToNot(Equal(""))
+		resp, err = client.Get("https://127.0.0.1:" + port + "/remoteAddr")
+		Expect(err).ToNot(HaveOccurred())
+		Expect(resp.StatusCode).To(Equal(200))
+		addr2 := resp.Header.Get("X-RemoteAddr")
+		Expect(addr2).ToNot(Equal(""))
+		Expect(addr1).To(Equal(addr2))
+	})
+
 	It("downloads concurrently", func() {
 		group, ctx := errgroup.WithContext(context.Background())
 		for i := 0; i < 2; i++ {
diff --git a/integrationtests/self/self_suite_test.go b/integrationtests/self/self_suite_test.go
index 10adc856..8f9436e6 100644
--- a/integrationtests/self/self_suite_test.go
+++ b/integrationtests/self/self_suite_test.go
@@ -90,10 +90,11 @@ var (
 	qlogTracer func(context.Context, logging.Perspective, quic.ConnectionID) logging.ConnectionTracer
 	enableQlog bool
 
-	version            quic.VersionNumber
-	tlsConfig          *tls.Config
-	tlsConfigLongChain *tls.Config
-	tlsClientConfig    *tls.Config
+	version                          quic.VersionNumber
+	tlsConfig                        *tls.Config
+	tlsConfigLongChain               *tls.Config
+	tlsClientConfig                  *tls.Config
+	tlsClientConfigWithoutServerName *tls.Config
 )
 
 // read the logfile command line flag
@@ -131,6 +132,10 @@ func init() {
 		RootCAs:    root,
 		NextProtos: []string{alpn},
 	}
+	tlsClientConfigWithoutServerName = &tls.Config{
+		RootCAs:    root,
+		NextProtos: []string{alpn},
+	}
 }
 
 var _ = BeforeSuite(func() {
@@ -165,6 +170,10 @@ func getTLSClientConfig() *tls.Config {
 	return tlsClientConfig.Clone()
 }
 
+func getTLSClientConfigWithoutServerName() *tls.Config {
+	return tlsClientConfigWithoutServerName.Clone()
+}
+
 func getQuicConfig(conf *quic.Config) *quic.Config {
 	if conf == nil {
 		conf = &quic.Config{}
diff --git a/integrationtests/tools/crypto.go b/integrationtests/tools/crypto.go
index d0bdfb41..6bd02ee0 100644
--- a/integrationtests/tools/crypto.go
+++ b/integrationtests/tools/crypto.go
@@ -9,6 +9,7 @@ import (
 	"crypto/x509"
 	"crypto/x509/pkix"
 	"math/big"
+	"net"
 	"time"
 )
 
@@ -44,6 +45,7 @@ func GenerateLeafCert(ca *x509.Certificate, caPriv crypto.PrivateKey) (*x509.Cer
 	certTempl := &x509.Certificate{
 		SerialNumber: big.NewInt(1),
 		DNSNames:     []string{"localhost"},
+		IPAddresses:  []net.IP{net.IPv4(127, 0, 0, 1)},
 		NotBefore:    time.Now(),
 		NotAfter:     time.Now().Add(24 * time.Hour),
 		ExtKeyUsage:  []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth},
diff --git a/integrationtests/tools/proxy/proxy.go b/integrationtests/tools/proxy/proxy.go
index 01e6a4a9..4ed2d89d 100644
--- a/integrationtests/tools/proxy/proxy.go
+++ b/integrationtests/tools/proxy/proxy.go
@@ -169,6 +169,12 @@ func NewQuicProxy(local string, opts *Opts) (*QuicProxy, error) {
 	if err != nil {
 		return nil, err
 	}
+	if err := conn.SetReadBuffer(protocol.DesiredReceiveBufferSize); err != nil {
+		return nil, err
+	}
+	if err := conn.SetWriteBuffer(protocol.DesiredSendBufferSize); err != nil {
+		return nil, err
+	}
 	raddr, err := net.ResolveUDPAddr("udp", opts.RemoteAddr)
 	if err != nil {
 		return nil, err
@@ -225,13 +231,19 @@ func (p *QuicProxy) LocalPort() int {
 }
 
 func (p *QuicProxy) newConnection(cliAddr *net.UDPAddr) (*connection, error) {
-	srvudp, err := net.DialUDP("udp", nil, p.serverAddr)
+	conn, err := net.DialUDP("udp", nil, p.serverAddr)
 	if err != nil {
 		return nil, err
 	}
+	if err := conn.SetReadBuffer(protocol.DesiredReceiveBufferSize); err != nil {
+		return nil, err
+	}
+	if err := conn.SetWriteBuffer(protocol.DesiredSendBufferSize); err != nil {
+		return nil, err
+	}
 	return &connection{
 		ClientAddr:      cliAddr,
-		ServerConn:      srvudp,
+		ServerConn:      conn,
 		incomingPackets: make(chan packetEntry, 10),
 		Incoming:        newQueue(),
 		Outgoing:        newQueue(),
diff --git a/internal/utils/ringbuffer/ringbuffer_bench_test.go b/internal/utils/ringbuffer/ringbuffer_bench_test.go
new file mode 100644
index 00000000..ac92ed33
--- /dev/null
+++ b/internal/utils/ringbuffer/ringbuffer_bench_test.go
@@ -0,0 +1,12 @@
+package ringbuffer
+
+import "testing"
+
+func BenchmarkRingBuffer(b *testing.B) {
+	r := RingBuffer[int]{}
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		r.PushBack(i)
+		r.PopFront()
+	}
+}
diff --git a/internal/utils/ringbuffer/ringbuffer_suite_test.go b/internal/utils/ringbuffer/ringbuffer_suite_test.go
new file mode 100644
index 00000000..c537d459
--- /dev/null
+++ b/internal/utils/ringbuffer/ringbuffer_suite_test.go
@@ -0,0 +1,13 @@
+package ringbuffer
+
+import (
+	"testing"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+)
+
+func TestTestdata(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "ringbuffer suite")
+}
diff --git a/internal/utils/ringbuffer/ringbuffer_test.go b/internal/utils/ringbuffer/ringbuffer_test.go
new file mode 100644
index 00000000..13241a30
--- /dev/null
+++ b/internal/utils/ringbuffer/ringbuffer_test.go
@@ -0,0 +1,38 @@
+package ringbuffer
+
+import (
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("RingBuffer", func() {
+	It("push and pop", func() {
+		r := RingBuffer[int]{}
+		Expect(len(r.ring)).To(Equal(0))
+		Expect(func() { r.PopFront() }).To(Panic())
+		r.PushBack(1)
+		r.PushBack(2)
+		r.PushBack(3)
+		Expect(r.PopFront()).To(Equal(1))
+		Expect(r.PopFront()).To(Equal(2))
+		r.PushBack(4)
+		r.PushBack(5)
+		Expect(r.Len()).To(Equal(3))
+		r.PushBack(6)
+		Expect(r.Len()).To(Equal(4))
+		Expect(r.PopFront()).To(Equal(3))
+		Expect(r.PopFront()).To(Equal(4))
+		Expect(r.PopFront()).To(Equal(5))
+		Expect(r.PopFront()).To(Equal(6))
+	})
+	It("clear", func() {
+		r := RingBuffer[int]{}
+		r.Init(2)
+		r.PushBack(1)
+		r.PushBack(2)
+		Expect(r.full).To(BeTrue())
+		r.Clear()
+		Expect(r.full).To(BeFalse())
+		Expect(r.Len()).To(Equal(0))
+	})
+})
diff --git a/internal/utils/rtt_stats_test.go b/internal/utils/rtt_stats_test.go
index 29892c6f..eae31926 100644
--- a/internal/utils/rtt_stats_test.go
+++ b/internal/utils/rtt_stats_test.go
@@ -154,4 +154,14 @@ var _ = Describe("RTT stats", func() {
 		Expect(rttStats.SmoothedRTT()).To(Equal(200 * time.Millisecond))
 		Expect(rttStats.MeanDeviation()).To(Equal(100 * time.Millisecond))
 	})
+
+	It("doesn't restore the RTT if we already have a measurement", func() {
+		const rtt = 10 * time.Millisecond
+		rttStats.UpdateRTT(rtt, 0, time.Now())
+		Expect(rttStats.LatestRTT()).To(Equal(rtt))
+		Expect(rttStats.SmoothedRTT()).To(Equal(rtt))
+		rttStats.SetInitialRTT(time.Minute)
+		Expect(rttStats.LatestRTT()).To(Equal(rtt))
+		Expect(rttStats.SmoothedRTT()).To(Equal(rtt))
+	})
 })
diff --git a/internal/wire/ack_frame_test.go b/internal/wire/ack_frame_test.go
index 49d11374..f80335c0 100644
--- a/internal/wire/ack_frame_test.go
+++ b/internal/wire/ack_frame_test.go
@@ -170,6 +170,9 @@ var _ = Describe("ACK Frame (for IETF QUIC)", func() {
 				Expect(frame.LargestAcked()).To(Equal(protocol.PacketNumber(100)))
 				Expect(frame.LowestAcked()).To(Equal(protocol.PacketNumber(90)))
 				Expect(frame.HasMissingRanges()).To(BeFalse())
+				Expect(frame.ECT0).To(BeEquivalentTo(0x42))
+				Expect(frame.ECT1).To(BeEquivalentTo(0x12345))
+				Expect(frame.ECNCE).To(BeEquivalentTo(0x12345678))
 				Expect(b.Len()).To(BeZero())
 			})
 
diff --git a/internal/wire/transport_parameter_test.go b/internal/wire/transport_parameter_test.go
index f4c39603..5526750e 100644
--- a/internal/wire/transport_parameter_test.go
+++ b/internal/wire/transport_parameter_test.go
@@ -289,15 +289,16 @@ var _ = Describe("Transport Parameters", func() {
 		Expect(float32(dataLen) / num).To(BeNumerically("~", float32(defaultLen)/num+float32(entryLen), 1))
 	})
 
-	It("sets the default value for the ack_delay_exponent, when no value was sent", func() {
+	It("sets the default value for the ack_delay_exponent and max_active_connection_id_limit, when no values were sent", func() {
 		data := (&TransportParameters{
 			AckDelayExponent:        protocol.DefaultAckDelayExponent,
 			StatelessResetToken:     &protocol.StatelessResetToken{},
-			ActiveConnectionIDLimit: 2,
+			ActiveConnectionIDLimit: protocol.DefaultActiveConnectionIDLimit,
 		}).Marshal(protocol.PerspectiveServer)
 		p := &TransportParameters{}
 		Expect(p.Unmarshal(data, protocol.PerspectiveServer)).To(Succeed())
 		Expect(p.AckDelayExponent).To(BeEquivalentTo(protocol.DefaultAckDelayExponent))
+		Expect(p.ActiveConnectionIDLimit).To(BeEquivalentTo(protocol.DefaultActiveConnectionIDLimit))
 	})
 
 	It("errors when the varint value has the wrong length", func() {
diff --git a/packet_packer_test.go b/packet_packer_test.go
index 31caa17a..05dc8689 100644
--- a/packet_packer_test.go
+++ b/packet_packer_test.go
@@ -316,6 +316,12 @@ var _ = Describe("Packet packer", func() {
 				Expect(p.longHdrPackets[0].EncryptionLevel()).To(Equal(protocol.Encryption0RTT))
 				Expect(p.longHdrPackets[0].frames).To(Equal([]*ackhandler.Frame{cf}))
 			})
+
+			It("doesn't add an ACK-only 0-RTT packet", func() { // ACK frames cannot be sent in 0-RTT packets
+				p, err := packer.PackCoalescedPacket(true, protocol.Version1)
+				Expect(err).ToNot(HaveOccurred())
+				Expect(p).To(BeNil())
+			})
 		})
 
 		Context("packing CONNECTION_CLOSE", func() {