feat(netcore): write tests for dialer.go (#63)

This commit adds tests for dialer.go. While there, add some extra
comments regarding things to do next.

netcore/dialer.go

@@ -52,6 +52,9 @@ func (nx *Network) sequentialDial(
 		}
 		errv = append(errv, err)
 	}
+	if len(errv) <= 0 {
+		return nil, errors.New("no endpoints to dial")
+	}
 	return nil, errors.Join(errv...)
 }
 
@@ -68,7 +71,8 @@ func (nx *Network) dialLog(ctx context.Context, network, address string) (net.Co
 	// Emit structured event after the dial
 	nx.emitConnectDone(ctx, network, address, t0, conn, err)
 
-	// Maybe wrap the connection if it's not nil and it makes sense to wrap it
+	// Maybe wrap the connection if it's not nil and it makes sense
+	// to wrap it (i.e., we have logging enabled)
 	conn = nx.maybeWrapConn(ctx, conn)
 
 	// Return the connection and error to the caller
@@ -83,6 +87,8 @@ func (nx *Network) dialNet(ctx context.Context, network, address string) (net.Co
 	}
 
 	// otherwise use the net package
+	// TODO(bassosimone): either make multipath TCP configurable
+	// or document that we disable it by default
 	child := &net.Dialer{}
 	child.SetMultipathTCP(false)
 	return child.DialContext(ctx, network, address)

netcore/dialer_test.go

@@ -0,0 +1,293 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package netcore
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"log/slog"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/rbmk-project/common/mocks"
+	"github.com/rbmk-project/common/runtimex"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNetwork_DialContext(t *testing.T) {
+	t.Run("lookup failure", func(t *testing.T) {
+		expectedErr := errors.New("mocked lookup error")
+		nx := &Network{
+			LookupHostFunc: func(ctx context.Context, domain string) ([]string, error) {
+				return nil, expectedErr
+			},
+		}
+		conn, err := nx.DialContext(context.Background(), "tcp", "example.com:80")
+		assert.ErrorIs(t, err, expectedErr)
+		assert.Nil(t, conn)
+	})
+
+	t.Run("dial failure", func(t *testing.T) {
+		expectedErr := errors.New("mocked dial error")
+		nx := &Network{
+			LookupHostFunc: func(ctx context.Context, domain string) ([]string, error) {
+				return []string{"1.2.3.4"}, nil
+			},
+			DialContextFunc: func(ctx context.Context, network, address string) (net.Conn, error) {
+				return nil, expectedErr
+			},
+		}
+		conn, err := nx.DialContext(context.Background(), "tcp", "example.com:80")
+		assert.ErrorIs(t, err, expectedErr)
+		assert.Nil(t, conn)
+	})
+
+	t.Run("successful dial", func(t *testing.T) {
+		mockConn := &mocks.Conn{
+			MockLocalAddr: func() net.Addr {
+				return &net.TCPAddr{IP: net.ParseIP("127.0.0.1"), Port: 1234}
+			},
+			MockRemoteAddr: func() net.Addr {
+				return &net.TCPAddr{IP: net.ParseIP("1.2.3.4"), Port: 80}
+			},
+		}
+		nx := &Network{
+			LookupHostFunc: func(ctx context.Context, domain string) ([]string, error) {
+				return []string{"1.2.3.4"}, nil
+			},
+			DialContextFunc: func(ctx context.Context, network, address string) (net.Conn, error) {
+				return mockConn, nil
+			},
+		}
+		conn, err := nx.DialContext(context.Background(), "tcp", "example.com:80")
+		assert.NoError(t, err)
+		assert.Equal(t, mockConn, conn)
+	})
+}
+
+func TestNetwork_sequentialDial(t *testing.T) {
+	t.Run("empty endpoints list", func(t *testing.T) {
+		nx := &Network{}
+		conn, err := nx.sequentialDial(context.Background(), "tcp", nx.dialLog)
+		assert.Error(t, err)
+		assert.Nil(t, conn)
+	})
+
+	t.Run("all endpoints fail", func(t *testing.T) {
+		expectedErr1 := errors.New("error 1")
+		expectedErr2 := errors.New("error 2")
+		dialAttempts := 0
+		nx := &Network{
+			DialContextFunc: func(ctx context.Context, network, address string) (net.Conn, error) {
+				dialAttempts++
+				if address == "1.1.1.1:80" {
+					return nil, expectedErr1
+				}
+				return nil, expectedErr2
+			},
+		}
+		conn, err := nx.sequentialDial(context.Background(), "tcp", nx.dialLog, "1.1.1.1:80", "2.2.2.2:80")
+		assert.Error(t, err)
+		assert.Nil(t, conn)
+		assert.Equal(t, 2, dialAttempts)
+		assert.ErrorIs(t, err, expectedErr1)
+		assert.ErrorIs(t, err, expectedErr2)
+	})
+
+	t.Run("first endpoint succeeds", func(t *testing.T) {
+		mockConn := &mocks.Conn{}
+		nx := &Network{
+			DialContextFunc: func(ctx context.Context, network, address string) (net.Conn, error) {
+				return mockConn, nil
+			},
+		}
+		conn, err := nx.sequentialDial(context.Background(), "tcp", nx.dialLog, "1.1.1.1:80", "2.2.2.2:80")
+		assert.NoError(t, err)
+		assert.Equal(t, mockConn, conn)
+	})
+
+	t.Run("second endpoint succeeds", func(t *testing.T) {
+		mockConn := &mocks.Conn{}
+		expectedErr := errors.New("first endpoint fails")
+		dialAttempts := 0
+		nx := &Network{
+			DialContextFunc: func(ctx context.Context, network, address string) (net.Conn, error) {
+				dialAttempts++
+				if dialAttempts == 1 {
+					return nil, expectedErr
+				}
+				return mockConn, nil
+			},
+		}
+		conn, err := nx.sequentialDial(context.Background(), "tcp", nx.dialLog, "1.1.1.1:80", "2.2.2.2:80")
+		assert.NoError(t, err)
+		assert.Equal(t, mockConn, conn)
+		assert.Equal(t, 2, dialAttempts)
+	})
+}
+
+func TestNetwork_dialLog(t *testing.T) {
+	t.Run("successful dial with logging", func(t *testing.T) {
+		var buf bytes.Buffer
+		fixedTime := time.Date(2024, 1, 1, 0, 0, 0, 0, time.UTC)
+		logger := slog.New(slog.NewJSONHandler(&buf, &slog.HandlerOptions{
+			Level: slog.LevelInfo,
+			ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
+				if a.Key == slog.TimeKey {
+					return slog.Attr{}
+				}
+				return a
+			},
+		}))
+
+		mockConn := &mocks.Conn{
+			MockLocalAddr: func() net.Addr {
+				return &net.TCPAddr{IP: net.ParseIP("127.0.0.1"), Port: 1234}
+			},
+			MockRemoteAddr: func() net.Addr {
+				return &net.TCPAddr{IP: net.ParseIP("1.1.1.1"), Port: 80}
+			},
+		}
+
+		nx := &Network{
+			Logger: logger,
+			TimeNow: func() time.Time {
+				return fixedTime
+			},
+			DialContextFunc: func(ctx context.Context, network, address string) (net.Conn, error) {
+				return mockConn, nil
+			},
+		}
+
+		conn, err := nx.dialLog(context.Background(), "tcp", "1.1.1.1:80")
+		assert.NoError(t, err)
+		assert.Equal(t, mockConn, conn)
+
+		logs := strings.Split(strings.TrimSpace(buf.String()), "\n")
+		assert.Len(t, logs, 2)
+
+		// Verify connectStart log
+		var startLog map[string]interface{}
+		err = json.Unmarshal([]byte(logs[0]), &startLog)
+		assert.NoError(t, err)
+		assert.Equal(t, map[string]interface{}{
+			"level":      "INFO",
+			"msg":        "connectStart",
+			"protocol":   "tcp",
+			"remoteAddr": "1.1.1.1:80",
+			"t":          fixedTime.Format(time.RFC3339Nano),
+		}, startLog)
+
+		// Verify connectDone log
+		var doneLog map[string]interface{}
+		err = json.Unmarshal([]byte(logs[1]), &doneLog)
+		assert.NoError(t, err)
+		assert.Equal(t, map[string]interface{}{
+			"level":      "INFO",
+			"msg":        "connectDone",
+			"err":        nil,
+			"errClass":   "",
+			"localAddr":  "127.0.0.1:1234",
+			"protocol":   "tcp",
+			"remoteAddr": "1.1.1.1:80",
+			"t0":         fixedTime.Format(time.RFC3339Nano),
+			"t":          fixedTime.Format(time.RFC3339Nano),
+		}, doneLog)
+	})
+
+	t.Run("dial failure with logging", func(t *testing.T) {
+		var buf bytes.Buffer
+		fixedTime := time.Date(2024, 1, 1, 0, 0, 0, 0, time.UTC)
+		logger := slog.New(slog.NewJSONHandler(&buf, &slog.HandlerOptions{
+			Level: slog.LevelInfo,
+			ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
+				if a.Key == slog.TimeKey {
+					return slog.Attr{}
+				}
+				return a
+			},
+		}))
+
+		expectedErr := errors.New("mocked dial error")
+		nx := &Network{
+			Logger: logger,
+			TimeNow: func() time.Time {
+				return fixedTime
+			},
+			DialContextFunc: func(ctx context.Context, network, address string) (net.Conn, error) {
+				return nil, expectedErr
+			},
+		}
+
+		conn, err := nx.dialLog(context.Background(), "tcp", "1.1.1.1:80")
+		assert.ErrorIs(t, err, expectedErr)
+		assert.Nil(t, conn)
+
+		logs := strings.Split(strings.TrimSpace(buf.String()), "\n")
+		assert.Len(t, logs, 2)
+
+		// Verify connectStart log
+		var startLog map[string]interface{}
+		err = json.Unmarshal([]byte(logs[0]), &startLog)
+		assert.NoError(t, err)
+		assert.Equal(t, map[string]interface{}{
+			"level":      "INFO",
+			"msg":        "connectStart",
+			"protocol":   "tcp",
+			"remoteAddr": "1.1.1.1:80",
+			"t":          fixedTime.Format(time.RFC3339Nano),
+		}, startLog)
+
+		// Verify connectDone log
+		var doneLog map[string]interface{}
+		err = json.Unmarshal([]byte(logs[1]), &doneLog)
+		assert.NoError(t, err)
+		assert.Equal(t, map[string]interface{}{
+			"level":      "INFO",
+			"msg":        "connectDone",
+			"err":        expectedErr.Error(),
+			"errClass":   "EGENERIC",
+			"localAddr":  "",
+			"protocol":   "tcp",
+			"remoteAddr": "1.1.1.1:80",
+			"t0":         fixedTime.Format(time.RFC3339Nano),
+			"t":          fixedTime.Format(time.RFC3339Nano),
+		}, doneLog)
+	})
+}
+
+func TestNetwork_dialNet(t *testing.T) {
+	t.Run("using custom dialer", func(t *testing.T) {
+		mockConn := &mocks.Conn{}
+		nx := &Network{
+			DialContextFunc: func(ctx context.Context, network, address string) (net.Conn, error) {
+				return mockConn, nil
+			},
+		}
+		conn, err := nx.dialNet(context.Background(), "tcp", "1.1.1.1:80")
+		assert.NoError(t, err)
+		assert.Equal(t, mockConn, conn)
+	})
+
+	t.Run("using net package", func(t *testing.T) {
+		// create a server using localhost to test against
+		server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.WriteHeader(http.StatusOK)
+		}))
+		defer server.Close()
+
+		nx := &Network{}
+		parsed := runtimex.Try1(url.Parse(server.URL))
+		conn, err := nx.dialNet(context.Background(), "tcp", parsed.Host)
+		assert.NoError(t, err)
+		assert.NotNil(t, conn)
+		conn.Close()
+	})
+}