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Tcp rst handling (#40)

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* claude suggests a way forward

* add timing to capture printer

* add pcap.Flags

* fix ICMP CRC calculation and add test

* bugfix: still send data on half-close state(close-wait)

* fix pcap test
This commit is contained in:
Pat Whittingslow
2026-02-23 13:50:13 +01:00
committed by GitHub
parent 08423d0dba
commit 7d323aae19
10 changed files with 386 additions and 46 deletions
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x/xnet/xnet_test.go
+80
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@@ -11,6 +11,7 @@ import (
"github.com/soypat/lneto/arp"
"github.com/soypat/lneto/ethernet"
"github.com/soypat/lneto/internal/ltesto"
"github.com/soypat/lneto/internet/pcap"
"github.com/soypat/lneto/ipv4"
"github.com/soypat/lneto/tcp"
@@ -909,3 +910,82 @@ func TestTCPConn_BufferNotClearedOnPassiveClose(t *testing.T) {
t.Fatalf("read wrong data: got %q, want %q", readBuf[:n], sendData)
}
}
func TestStackAsync_ICMPEchoChecksum(t *testing.T) {
const MTU = 1500
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}
routerMAC := [6]byte{0x00, 0x11, 0x22, 0x33, 0x44, 0x55}
stack := new(StackAsync)
err := stack.Reset(StackConfig{
Hostname: "ICMPTest",
RandSeed: 42,
StaticAddress: stackAddr,
HardwareAddress: stackMAC,
MTU: MTU,
})
if err != nil {
t.Fatal(err)
}
gen := ltesto.PacketGen{
SrcMAC: routerMAC,
DstMAC: stackMAC,
SrcIPv4: routerAddr,
DstIPv4: stackAddr.As4(),
}
icmpPayload := []byte("abcdefghijklmnopqrstuvwxyz012345") // 32 bytes, typical ping payload.
// Test 1: Valid ICMP echo request should be accepted.
pkt := gen.AppendIPv4ICMPEcho(nil, ltesto.ICMPEchoConfig{
Identifier: 0x1234,
SequenceNumber: 1,
Payload: icmpPayload,
})
err = stack.Demux(pkt, 0)
if err != nil {
t.Fatalf("valid ICMP echo rejected: %v", err)
}
// Test 2: Valid ICMP with trailing FCS bytes (simulates real PIO hardware capture).
// This is a regression test for the bug where recvicmp checksummed ifrm.RawData()
// instead of ifrm.Payload(), causing the 4 trailing FCS bytes to corrupt the checksum.
pkt = gen.AppendIPv4ICMPEcho(nil, ltesto.ICMPEchoConfig{
Identifier: 0x1234,
SequenceNumber: 2,
Payload: icmpPayload,
})
pkt = append(pkt, 0xDE, 0xAD, 0xBE, 0xEF) // Simulate Ethernet FCS.
err = stack.Demux(pkt, 0)
if err != nil {
t.Fatalf("valid ICMP with trailing FCS rejected: %v", err)
}
// Test 3: Corrupted ICMP checksum should be rejected.
pkt = gen.AppendIPv4ICMPEcho(nil, ltesto.ICMPEchoConfig{
Identifier: 0x1234,
SequenceNumber: 3,
Payload: icmpPayload,
})
pkt[len(pkt)-1] ^= 0xFF // Flip bits in last payload byte to corrupt ICMP checksum.
err = stack.Demux(pkt, 0)
if err == nil {
t.Fatal("corrupted ICMP accepted, expected CRC error")
}
// Test 4: Corrupted ICMP with trailing FCS should also be rejected.
pkt = gen.AppendIPv4ICMPEcho(nil, ltesto.ICMPEchoConfig{
Identifier: 0x1234,
SequenceNumber: 4,
Payload: icmpPayload,
})
pkt[len(pkt)-1] ^= 0xFF // Corrupt ICMP payload.
pkt = append(pkt, 0xDE, 0xAD, 0xBE, 0xEF) // Simulate Ethernet FCS.
err = stack.Demux(pkt, 0)
if err == nil {
t.Fatal("corrupted ICMP with FCS accepted, expected CRC error")
}
}