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Tcp buffer bug fix (#79)

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* start working on tracking down tcp buffer bug

* mtu refactor

* modularize test

* more precise testing

* tests fail, but is it the failure we are looking for?

* fix typo in espradio link (#76)

* implement a new backoff abstraction (#75)

* rewrite backoff api

* rewrite tcp.Conn.Write

* keep fixing small things

* much better Conn.Read implementation

* fix critical overflow bug in internal.ConnRWBackoff

---------

Co-authored-by: Joel Wetzell <jwetzell@yahoo.com>
This commit is contained in:
Pat Whittingslow
2026-04-14 19:11:29 -03:00
committed by GitHub
parent 5bde7a9979
commit 75a812a8d7
22 changed files with 354 additions and 109 deletions
Download Patch File Download Diff File Expand all files Collapse all files
x/xnet/xnet_arp_test.go
+3 -1
View File
@@ -4,10 +4,12 @@ import (
"bytes"
"net/netip"
"testing"
"github.com/soypat/lneto/ethernet"
)
func TestARPLocal(t *testing.T) {
const mtu = 1500
const mtu = ethernet.MaxMTU
const seed = 1
s1, s2, c1, c2 := newTCPStacks(t, seed, mtu)
routerHw := [6]byte{1, 2, 3, 4, 5, 6}
x/xnet/xnet_bench_test.go
+4 -4
View File
@@ -9,8 +9,8 @@ import (
)
func BenchmarkARPExchange(b *testing.B) {
const MTU = 1500
const frameSize = MTU + ethernet.MaxOverheadSize
const MTU = ethernet.MaxMTU
const frameSize = ethernet.MaxFrameLength
c1, c2 := new(StackAsync), new(StackAsync)
queryAddr := netip.AddrFrom4([4]byte{192, 168, 1, 2})
@@ -76,8 +76,8 @@ func BenchmarkARPExchange(b *testing.B) {
}
func BenchmarkTCPHandshake(b *testing.B) {
const MTU = 1500
const frameSize = MTU + ethernet.MaxOverheadSize
const MTU = ethernet.MaxMTU
const frameSize = ethernet.MaxFrameLength
const svPort = 8080
client, sv := new(StackAsync), new(StackAsync)
clconn, svconn := new(tcp.Conn), new(tcp.Conn)
x/xnet/xnet_concurrent_test.go
+152 -2
View File
@@ -4,14 +4,19 @@ import (
"bytes"
"context"
"fmt"
"log/slog"
"math/rand"
"net/netip"
"os"
"runtime"
"sync"
"testing"
"time"
"github.com/soypat/lneto"
"github.com/soypat/lneto/ethernet"
"github.com/soypat/lneto/internal"
"github.com/soypat/lneto/ipv4"
"github.com/soypat/lneto/tcp"
)
@@ -142,8 +147,8 @@ func TestTCPListener_ConcurrentEcho(t *testing.T) {
}
func kernelLoop(ctx context.Context, server *StackAsync, clients []StackAsync) {
const MTU = 1500
const carrierDataSize = MTU + ethernet.MaxOverheadSize
const MTU = ethernet.MaxMTU
const carrierDataSize = ethernet.MaxFrameLength
buf := make([]byte, carrierDataSize)
rng := rand.New(rand.NewSource(1)) // Seed 1 for deterministic but randomized order
order := make([]int, len(clients))
@@ -285,3 +290,148 @@ func runClient(t *testing.T, id int, stack *StackAsync, conn *tcp.Conn,
}
return true
}
func TestCloseTransmitsPending(t *testing.T) {
const mtu = ipv4.MinimumMTU
const tcpbufsize = mtu * 2
const tcpDataPerPkt = mtu - 14 - 20 - 20 // Ethernet=14, IPv4=20, TCP=20
const expectPkts = 2*tcpbufsize/tcpDataPerPkt + 1
const queueSize = 5
const port1, port2 = 10, 20
tst := testerFrom(t, mtu)
tst.buf = tst.buf[:mtu+14]
s1, s2, c1, c2 := newTCPStacks(t, 0x1337_c0de, mtu)
t.Run("sync", func(t *testing.T) {
// testCloseTransmitsPending(tst, s1, s2, c1, c2, queueSize, tcpbufsize, tcpbufsize, tcpbufsize)
})
t.Run("async", func(t *testing.T) {
testCloseTransmitsPending(tst, s1, s2, c1, c2, queueSize, tcpbufsize, tcpbufsize, 2*tcpbufsize)
})
}
func testCloseTransmitsPending(tst *tester, s1, s2 *StackAsync, c1, c2 *tcp.Conn, queueSize, tx1Buf, rx2Buf, datalen int) {
t := tst.t
buf := tst.buf
defer func() {
c1.Abort()
c2.Abort()
// Ensure they are unregistered.
s1.EgressIP(buf)
s2.EgressIP(buf)
}()
logger := slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
Level: slog.LevelDebug - 99,
}))
err := c1.Configure(tcp.ConnConfig{
RxBuf: nil,
TxBuf: make([]byte, tx1Buf),
TxPacketQueueSize: queueSize,
RWBackoff: backoffGosched,
Logger: logger,
})
if err != nil {
t.Fatal(err)
}
err = c2.InternalHandler().SetBuffers(nil, make([]byte, rx2Buf), queueSize)
if err != nil {
t.Fatal(err)
}
const (
port1, port2 = 10, 20
)
tst.TestTCPSetupAndEstablish(s1, s2, c1, c2, port1, port2)
if c1.FreeOutput() != tx1Buf {
t.Fatalf("want %d free bytes, got %d", tx1Buf, c1.FreeOutput())
}
data := make([]byte, datalen)
for i := range datalen {
data[i] = byte(i)
}
deadline := time.Now().Add(3600 * time.Second)
err = c1.SetDeadline(deadline)
err2 := c2.SetDeadline(deadline)
if err != nil || err2 != nil {
t.Fatal(err)
}
async := datalen > tx1Buf
if async {
// Since data does not fit in TCP Tx buffer the test must be run asynchronously.
c1.InternalHandler().SetLoggers(logger, logger)
// c1.InternalHandler().SetLoggers(nil, nil)
go func() {
n, err := c1.Write(data)
if err != nil {
t.Error("async write", err)
} else if n != len(data) {
t.Error("io.Writer faulty implementation")
}
err = c1.Close()
if err != nil {
t.Fatal("async close", err)
}
}()
} else {
n, err := c1.Write(data)
if err != nil || n != len(data) {
t.Fatal(err, n)
}
err = c1.Close()
if err != nil {
t.Fatal(err)
}
}
exchanges := -1
exchanging := 1
tcpData := 0
totalRead := 0
for exchanging > 0 || c1.State().TxDataOpen() {
exchanges++
exchanging = exchangeEthernetOnce(t, s1, s2, buf)
frm, ok := getTCPFrame(buf[:exchanging])
if ok {
n := len(frm.Payload())
tcpData += n
if async && tcpData > 0 {
ngot, err := c2.Read(buf[:n])
if err != nil {
t.Error(err)
} else if ngot != n {
t.Errorf("want %d data read c1->c1, got %d", n, ngot)
} else if !internal.BytesEqual(buf[:n], data[totalRead:totalRead+n]) {
t.Errorf("exch%d data rx mismatch, want:\n%q\ngot:\n%q\n", exchanges, data[totalRead:totalRead+n], buf[:n])
}
totalRead += ngot
runtime.Gosched() // Yield to let c1 write via goroutine.
acks := exchangeEthernetOnce(t, s2, s1, buf) // Send ACK s1's way.
if acks == 0 {
t.Error("no data sent back to s1")
}
}
}
}
if c1.BufferedUnsent() != 0 {
t.Errorf("done %s: want no data left unsent got %d/%d", c1.State(), c1.BufferedUnsent(), len(data))
}
if tcpData != datalen {
t.Errorf("done %s: want %d bytes sent, got %d", c1.State(), len(data), tcpData)
}
if t.Failed() {
t.Logf("test params: txsz1=%d rxsz2=%d queuesize=%d data(sent/had)=%d/%d", tx1Buf, rx2Buf, queueSize, tcpData, datalen)
}
if totalRead < datalen {
n, err := c2.Read(buf)
if err != nil {
t.Error(err)
} else if !internal.BytesEqual(buf[:n], data[totalRead:]) {
t.Errorf("expected last bytes equal: want:\n%q\ngot:\n%q\n", data[totalRead:], buf[:n])
}
}
}
func backoffGosched(consecutiveBackoffs int) (sleep time.Duration) {
return lneto.BackoffFlagGosched
}
x/xnet/xnet_deadline_test.go
+5 -4
View File
@@ -5,12 +5,13 @@ import (
"testing"
"time"
"github.com/soypat/lneto/ethernet"
"github.com/soypat/lneto/tcp"
)
func TestTCPConn_SetDeadline_Established(t *testing.T) {
const seed = 9999
const MTU = 1500
const MTU = ethernet.MaxMTU
const svPort = 8080
client, sv, clconn, svconn := newTCPStacks(t, seed, MTU)
tst := testerFrom(t, MTU)
@@ -37,7 +38,7 @@ func TestTCPConn_SetDeadline_Established(t *testing.T) {
func TestTCPConn_ReadDeadlineExceeded(t *testing.T) {
const seed = 10001
const MTU = 1500
const MTU = ethernet.MaxMTU
const svPort = 8080
client, sv, clconn, svconn := newTCPStacks(t, seed, MTU)
tst := testerFrom(t, MTU)
@@ -63,7 +64,7 @@ func TestTCPConn_ReadDeadlineExceeded(t *testing.T) {
func TestTCPConn_WriteDeadlineExceeded(t *testing.T) {
const seed = 10002
const MTU = 1500
const MTU = ethernet.MaxMTU
const svPort = 8080
client, sv, clconn, svconn := newTCPStacks(t, seed, MTU)
tst := testerFrom(t, MTU)
@@ -88,7 +89,7 @@ func TestTCPConn_WriteDeadlineExceeded(t *testing.T) {
func TestTCPConn_FlushEmptyNoop(t *testing.T) {
const seed = 10003
const MTU = 1500
const MTU = ethernet.MaxMTU
const svPort = 8080
client, sv, clconn, svconn := newTCPStacks(t, seed, MTU)
tst := testerFrom(t, MTU)
x/xnet/xnet_dns_test.go
+2 -2
View File
@@ -14,7 +14,7 @@ import (
func TestDNS_QueryReceivesAnswer(t *testing.T) {
const seed = 9876
const MTU = 1500
const MTU = ethernet.MaxMTU
// Create client stack with DNS server configured.
client := new(StackAsync)
@@ -47,7 +47,7 @@ func TestDNS_QueryReceivesAnswer(t *testing.T) {
}
// Client sends DNS query.
const carrierDataSize = MTU + ethernet.MaxOverheadSize
const carrierDataSize = ethernet.MaxFrameLength
var buf [carrierDataSize]byte
n, err := client.EgressEthernet(buf[:])
if err != nil {
x/xnet/xnet_fuzz_test.go
+5 -5
View File
@@ -17,9 +17,9 @@ import (
)
func FuzzStackPacketHTTP(f *testing.F) {
const MTU = 1500
const MTU = ethernet.MaxMTU
const seed = 1
var buf [MTU + ethernet.MaxOverheadSize]byte
var buf [ethernet.MaxFrameLength]byte
s1, s2, c1, c2 := newTCPStacks(f, seed, MTU)
var hdr httpraw.Header
err := s1.ListenTCP(c1, 80)
@@ -78,7 +78,7 @@ func FuzzStackPacketHTTP(f *testing.F) {
}
f.Fuzz(func(t *testing.T, pktnum int, a []byte) {
var buf [MTU + ethernet.MaxOverheadSize]byte
var buf [ethernet.MaxFrameLength]byte
s1, s2, c1, c2 := newTCPStacks(t, seed, MTU)
err = s1.EnableICMP(true)
if err != nil {
@@ -268,8 +268,8 @@ func testStackSeeded(t *testing.T, seed1, seed2 int64) {
}
}
const mtu = 1500
const mfl = mtu + 14 // frame length includes ethernet header
const mtu = ethernet.MaxMTU
const mfl = mtu + ethernet.MaxOverheadSize // frame length includes ethernet header
var buf [mfl]byte
var s1, s2 StackAsync
v1, v2 := byte(seed1), byte(seed2)
x/xnet/xnet_icmp_test.go
+7 -7
View File
@@ -42,11 +42,11 @@ func TestStackAsync_ICMPEcho(t *testing.T) {
t.Fatal(err)
}
echoSent := exchangeEthernetOnce(t, sender, receiver, buf)
if !echoSent {
if echoSent == 0 {
t.Error("ECHO not sent")
}
echoReplySent := exchangeEthernetOnce(t, receiver, sender, buf)
if !echoReplySent {
if echoReplySent == 0 {
t.Error("ECHOREPLY not sent")
}
n, err = sender.EgressEthernet(buf)
@@ -70,19 +70,19 @@ func TestStackAsync_ICMPEcho(t *testing.T) {
}
// exchangeEthernetOnce sends one Ethernet frame from src to dst if available.
func exchangeEthernetOnce(t *testing.T, src, dst *StackAsync, buf []byte) bool {
func exchangeEthernetOnce(t *testing.T, src, dst *StackAsync, buf []byte) int {
t.Helper()
n, err := src.EgressEthernet(buf)
if err != nil {
t.Fatal(err)
t.Error(err)
}
if n == 0 {
return false
return 0
}
if err := dst.IngressEthernet(buf[:n]); err != nil {
t.Fatal(err)
t.Error(err)
}
return true
return n
}
// newICMPStacks creates two test stacks with distinct static addresses and hardware addresses.
x/xnet/xnet_listener_test.go
+2 -2
View File
@@ -11,7 +11,7 @@ import (
func TestStackAsyncListener_SingleConnection(t *testing.T) {
const seed int64 = 1234
const MTU = 1500
const MTU = ethernet.MaxMTU
const carrierSize = MTU + ethernet.MaxOverheadSize
const svPort = 80
const clPort = 1337
@@ -122,7 +122,7 @@ func TestStackAsyncListener_SingleConnection(t *testing.T) {
func TestStackAsyncListener_MultiSequentialConn(t *testing.T) {
const seed int64 = 1234
const MTU = 1500
const MTU = ethernet.MaxMTU
const carrierSize = MTU + ethernet.MaxOverheadSize
const svPort = 80
const clPort = 1337
x/xnet/xnet_mdns_test.go
+4 -4
View File
@@ -14,7 +14,7 @@ import (
)
func TestMDNS_QueryResponse(t *testing.T) {
const MTU = 1500
const MTU = ethernet.MaxMTU
svcName, err := dns.NewName("My Web._http._tcp.local")
if err != nil {
t.Fatal(err)
@@ -196,7 +196,7 @@ func TestMDNS_QueryResponse(t *testing.T) {
}
func TestMDNS_SRVThroughStack(t *testing.T) {
const MTU = 1500
const MTU = ethernet.MaxMTU
svcName, err := dns.NewName("My Web._http._tcp.local")
if err != nil {
t.Fatal(err)
@@ -275,7 +275,7 @@ func newMDNSStack(t *testing.T, hostname string, seed int64,
mdnsCfg mdns.ClientConfig,
) (*StackAsync, *mdns.Client) {
t.Helper()
const MTU = 1500
const MTU = ethernet.MaxMTU
stack := new(StackAsync)
err := stack.Reset(StackConfig{
Hostname: hostname,
@@ -335,7 +335,7 @@ func mdnsQueryRespond(t *testing.T, querier, responder *StackAsync, buf []byte)
}
func TestMDNS_RealWorldQueries(t *testing.T) {
const MTU = 1500
const MTU = ethernet.MaxMTU
responderMAC := [6]byte{0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0x01}
querierMAC := [6]byte{0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0x02}
x/xnet/xnet_test.go
+35 -7
View File
@@ -9,6 +9,7 @@ import (
"testing"
"time"
"github.com/soypat/lneto"
"github.com/soypat/lneto/arp"
"github.com/soypat/lneto/ethernet"
"github.com/soypat/lneto/internal"
@@ -29,7 +30,7 @@ const (
func TestTCPConn_ReadBlocksUntilDataAvailable(t *testing.T) {
const seed = 5678
const MTU = 1500
const MTU = ethernet.MaxMTU
const svPort = 8080
client, sv, clconn, svconn := newTCPStacks(t, seed, MTU)
tst := testerFrom(t, MTU)
@@ -151,7 +152,7 @@ func TestStackAsyncTCP_multipacket(t *testing.T) {
func TestStackAsyncTCP_singlepacket(t *testing.T) {
const seed = 1234
const MTU = 1500
const MTU = ethernet.MaxMTU
const svPort = 80
client, sv, clconn, svconn := newTCPStacks(t, seed, MTU)
tst := testerFrom(t, MTU)
@@ -283,8 +284,19 @@ func (tst *tester) TestTCPHandshake(stack1, stack2 *StackAsync) {
noExchange(0),
noExchange(1),
}
for _, wants := range exch {
tst.TCPExchange(wants, stack1, stack2)
var got [len(exch)]struct {
seg tcp.Segment
}
for i, wants := range exch {
haveFailed := tst.t.Failed()
got[i].seg = tst.TCPExchange(wants, stack1, stack2)
if haveFailed != tst.t.Failed() {
tst.t.Logf("print out sent segments (%d):\n", i+1)
for k := range i + 1 {
str := tcp.StringExchange(got[k].seg, 255, 255, exch[k].SourceIdx == 0) // states unknown.
tst.t.Log(str)
}
}
}
}
@@ -734,7 +746,7 @@ func (tst *tester) getARPOperation() arp.Operation {
// The bug was that reset() cleared bufRx when state became CLOSED.
func TestTCPConn_BufferNotClearedOnPassiveClose(t *testing.T) {
const seed = 9999
const MTU = 1500
const MTU = ethernet.MaxMTU
const svPort = 8080
client, sv, clconn, svconn := newTCPStacks(t, seed, MTU)
tst := testerFrom(t, MTU)
@@ -915,8 +927,8 @@ func TestTCPConn_BufferNotClearedOnPassiveClose(t *testing.T) {
}
func TestStackAsync_ICMPEchoChecksum(t *testing.T) {
const MTU = 1500
const MaxFrameLength = MTU + 14 + 4 // Ethernet header+FCS.
const MTU = ethernet.MaxMTU
const MaxFrameLength = MTU + ethernet.MaxOverheadSize // Ethernet header+FCS+VLAN.
stackAddr := netip.AddrFrom4([4]byte{192, 168, 1, 99})
stackMAC := [6]byte{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff}
routerAddr := [4]byte{192, 168, 1, 1}
@@ -1017,3 +1029,19 @@ const (
protoIPv4 = "IPv4"
protoTCP = "TCP"
)
func getTCPFrame(etherFrame []byte) (tcp.Frame, bool) {
efrm, err := ethernet.NewFrame(etherFrame)
if err != nil || efrm.EtherTypeOrSize() != ethernet.TypeIPv4 {
return tcp.Frame{}, false
}
ifrm, err := ipv4.NewFrame(efrm.Payload())
if err != nil || ifrm.Protocol() != lneto.IPProtoTCP {
return tcp.Frame{}, false
}
tfrm, err := tcp.NewFrame(ifrm.Payload())
if err != nil {
return tcp.Frame{}, false
}
return tfrm, true
}