feature: randomized port iterator (#90)

pkg/ip/ip.go

@@ -8,21 +8,6 @@ import (
 
 var ErrInvalidAddr = errors.New("invalid IP subnet/host")
 
-func Inc(ip net.IP) {
-	for j := len(ip) - 1; j >= 0; j-- {
-		ip[j]++
-		if ip[j] > 0 {
-			break
-		}
-	}
-}
-
-func DupIP(ip net.IP) net.IP {
-	dup := make([]byte, 4)
-	copy(dup, ip.To4())
-	return dup
-}
-
 func ParseIPNet(subnet string) (*net.IPNet, error) {
 	_, result, err := net.ParseCIDR(subnet)
 	if err == nil {

pkg/ip/ip_test.go

@@ -7,56 +7,6 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func TestInc(t *testing.T) {
-	t.Parallel()
-	tests := []struct {
-		name     string
-		input    net.IP
-		expected net.IP
-	}{
-		{
-			name:     "ZeroNet",
-			input:    net.IPv4(0, 0, 0, 0),
-			expected: net.IPv4(0, 0, 0, 1),
-		},
-		{
-			name:     "Inc3rd",
-			input:    net.IPv4(1, 1, 0, 255),
-			expected: net.IPv4(1, 1, 1, 0),
-		},
-		{
-			name:     "Inc2nd",
-			input:    net.IPv4(1, 1, 255, 255),
-			expected: net.IPv4(1, 2, 0, 0),
-		},
-		{
-			name:     "Inc1st",
-			input:    net.IPv4(1, 255, 255, 255),
-			expected: net.IPv4(2, 0, 0, 0),
-		},
-	}
-
-	for _, vtt := range tests {
-		tt := vtt
-		t.Run(tt.name, func(t *testing.T) {
-			t.Parallel()
-			Inc(tt.input)
-			assert.Equal(t, tt.expected, tt.input)
-		})
-	}
-}
-
-func TestDupIP(t *testing.T) {
-	t.Parallel()
-	ipAddr := net.IPv4(192, 168, 0, 1).To4()
-
-	dupAddr := DupIP(ipAddr)
-	assert.Equal(t, ipAddr, dupAddr)
-
-	dupAddr[3]++
-	assert.Equal(t, net.IPv4(192, 168, 0, 1).To4(), ipAddr)
-}
-
 func TestParseIPNetWithError(t *testing.T) {
 	t.Parallel()
 	_, err := ParseIPNet("")

pkg/scan/request.go

@@ -1,4 +1,4 @@
-//go:generate mockgen -package scan -destination=mock_request_test.go -source request.go
+//go:generate mockgen -package scan -destination=mock_request_test.go . PortGenerator,IPGenerator,RequestGenerator,IPContainer
 //go:generate easyjson -output_filename request_easyjson.go request.go
 
 package scan
@@ -31,37 +31,67 @@ type Request struct {
 	Err     error
 }
 
+type PortGetter interface {
+	GetPort() (uint16, error)
+}
+
+type WrapPort uint16
+
+func (p WrapPort) GetPort() (uint16, error) {
+	return uint16(p), nil
+}
+
+type portError struct {
+	error
+}
+
+func (err *portError) GetPort() (uint16, error) {
+	return 0, err
+}
+
 type PortGenerator interface {
-	Ports(ctx context.Context, r *Range) (<-chan uint16, error)
+	Ports(ctx context.Context, r *Range) (<-chan PortGetter, error)
 }
 
 func NewPortGenerator() PortGenerator {
 	return &portGenerator{}
 }
 
-// TODO randomizedPortGenerator
 type portGenerator struct{}
 
-func (*portGenerator) Ports(ctx context.Context, r *Range) (<-chan uint16, error) {
+func (*portGenerator) Ports(ctx context.Context, r *Range) (<-chan PortGetter, error) {
 	if err := validatePorts(r.Ports); err != nil {
 		return nil, err
 	}
-	out := make(chan uint16, 100)
+	out := make(chan PortGetter, 100)
 	go func() {
 		defer close(out)
 		for _, portRange := range r.Ports {
-			for port := int(portRange.StartPort); port <= int(portRange.EndPort); port++ {
-				select {
-				case <-ctx.Done():
-					return
-				case out <- uint16(port):
+			it, err := newRangeIterator(int64(portRange.EndPort) - int64(portRange.StartPort) + 1)
+			if err != nil {
+				writePort(ctx, out, &portError{err})
+				continue
+			}
+			basePort := int64(portRange.StartPort) - 1
+			for {
+				writePort(ctx, out, WrapPort(basePort+it.Int().Int64()))
+				if !it.Next() {
+					break
 				}
 			}
 		}
 	}()
 	return out, nil
 }
 
+func writePort(ctx context.Context, out chan<- PortGetter, port PortGetter) {
+	select {
+	case <-ctx.Done():
+		return
+	case out <- port:
+	}
+}
+
 func validatePorts(ports []*PortRange) error {
 	if len(ports) == 0 {
 		return ErrPortRange
@@ -153,7 +183,12 @@ func (rg *ipPortGenerator) GenerateRequests(ctx context.Context, r *Range) (<-ch
 	out := make(chan *Request, 100)
 	go func() {
 		defer close(out)
-		for port := range ports {
+		for p := range ports {
+			port, err := p.GetPort()
+			if err != nil {
+				writeRequest(ctx, out, &Request{Err: err})
+				continue
+			}
 			for ipaddr := range ips {
 				dstip, err := ipaddr.GetIP()
 				writeRequest(ctx, out, &Request{