ICMP tests and various fixes (#68)

* various icmp fixes

* improve existing tests

x/xnet/xnet_icmp_test.go

@@ -0,0 +1,123 @@
+package xnet
+
+import (
+	"net/netip"
+	"testing"
+)
+
+func TestStackAsync_ICMPEcho(t *testing.T) {
+	tests := []struct {
+		name    string
+		pattern []byte
+		size    uint16
+	}{
+		{"1 EchoRequestReply", []byte("icmp-test"), 56},
+		{"2 ReplyToManualRequest", []byte("manual-echo"), 32},
+	}
+	sender, receiver := newICMPStacks(t, 42, 1500) // seed 42 is arbitrary, stacks get unique IPs
+	if err := sender.EnableICMP(true); err != nil {
+		t.Fatal(err)
+	}
+	if err := receiver.EnableICMP(true); err != nil {
+		t.Fatal(err)
+	}
+	buf := make([]byte, 2048)
+	n, err := sender.EgressEthernet(buf)
+	if n > 0 || err != nil {
+		t.Fatal("sender unexpected data sent or error", n, err)
+	}
+	n, err = receiver.EgressEthernet(buf)
+	if n > 0 || err != nil {
+		t.Fatal("receiver unexpected data sent or error", n, err)
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+
+			sender.SetGateway6(receiver.HardwareAddress())
+			receiver.SetGateway6(sender.HardwareAddress())
+
+			key, err := sender.icmp.PingStart(receiver.Addr().As4(), tt.pattern, tt.size)
+			if err != nil {
+				t.Fatal(err)
+			}
+			echoSent := exchangeEthernetOnce(t, sender, receiver, buf)
+			if !echoSent {
+				t.Error("ECHO not sent")
+			}
+			echoReplySent := exchangeEthernetOnce(t, receiver, sender, buf)
+			if !echoReplySent {
+				t.Error("ECHOREPLY not sent")
+			}
+			n, err = sender.EgressEthernet(buf)
+			if n > 0 || err != nil {
+				t.Error("sender excess data sent or error", n, err)
+			}
+			n, err = receiver.EgressEthernet(buf)
+			if n > 0 || err != nil {
+				t.Error("receiver excess data sent or error", n, err)
+			}
+
+			completed, ok := sender.icmp.PingPop(key)
+			if !ok {
+				t.Fatal("ping key not found")
+			}
+			if !completed {
+				t.Fatal("expected ping to complete")
+			}
+		})
+	}
+}
+
+// exchangeEthernetOnce sends one Ethernet frame from src to dst if available.
+func exchangeEthernetOnce(t *testing.T, src, dst *StackAsync, buf []byte) bool {
+	t.Helper()
+	n, err := src.EgressEthernet(buf)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if n == 0 {
+		return false
+	}
+	if err := dst.IngressEthernet(buf[:n]); err != nil {
+		t.Fatal(err)
+	}
+	return true
+}
+
+// newICMPStacks creates two test stacks with distinct static addresses and hardware addresses.
+func newICMPStacks(t testing.TB, randSeed int64, mtu int) (*StackAsync, *StackAsync) {
+	const icmpQueue = 4
+	s1, s2 := new(StackAsync), new(StackAsync)
+
+	// Use the seed to generate two adjacent IPs (10.0.0.x) and MACs.
+	base := byte(randSeed & 0x7F) // keep in safe range 0..127
+	addr1 := netip.AddrFrom4([4]byte{10, 0, 0, base})
+	addr2 := netip.AddrFrom4([4]byte{10, 0, 0, base + 1})
+	mac1 := [6]byte{0xbe, 0xef, 0, 0, 0, base}
+	mac2 := [6]byte{0xbe, 0xef, 0, 0, 0, base + 1}
+
+	if err := s1.Reset(StackConfig{
+		Hostname:        "icmp-stack-1",
+		RandSeed:        randSeed,
+		StaticAddress:   addr1,
+		HardwareAddress: mac1,
+		MTU:             uint16(mtu),
+		ICMPQueueLimit:  icmpQueue,
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := s2.Reset(StackConfig{
+		Hostname:        "icmp-stack-2",
+		RandSeed:        ^randSeed,
+		StaticAddress:   addr2,
+		HardwareAddress: mac2,
+		MTU:             uint16(mtu),
+		ICMPQueueLimit:  icmpQueue,
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	return s1, s2
+}