TUN-6695: Implement ICMP proxy for linux

ingress/icmp_linux_test.go

@@ -0,0 +1,52 @@
+//go:build linux
+
+package ingress
+
+import (
+	"errors"
+	"net"
+	"net/netip"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/cloudflare/cloudflared/packet"
+)
+
+func TestCloseIdleFlow(t *testing.T) {
+	const (
+		echoID      = 19234
+		idleTimeout = time.Millisecond * 100
+	)
+	conn, err := newICMPConn(localhostIP)
+	require.NoError(t, err)
+	flow := packet.Flow{
+		Src: netip.MustParseAddr("172.16.0.1"),
+	}
+	icmpFlow := newICMPFlow(conn, &flow, echoID, &noopLogger)
+	shutdownC := make(chan struct{})
+	flowErr := make(chan error)
+	go func() {
+		flowErr <- icmpFlow.serve(shutdownC, idleTimeout)
+	}()
+
+	require.Equal(t, errFlowInactive, <-flowErr)
+}
+
+func TestCloseConnStopFlow(t *testing.T) {
+	const (
+		echoID = 19234
+	)
+	conn, err := newICMPConn(localhostIP)
+	require.NoError(t, err)
+	flow := packet.Flow{
+		Src: netip.MustParseAddr("172.16.0.1"),
+	}
+	icmpFlow := newICMPFlow(conn, &flow, echoID, &noopLogger)
+	shutdownC := make(chan struct{})
+	conn.Close()
+
+	err = icmpFlow.serve(shutdownC, defaultCloseAfterIdle)
+	require.True(t, errors.Is(err, net.ErrClosed))
+}