GODRIVER-141: Expose local address in conn package

mongo/internal/conntest/mock.go

@@ -9,6 +9,7 @@ package conntest
 import (
 	"context"
 	"fmt"
+	"net"
 
 	"github.com/10gen/mongo-go-driver/mongo/model"
 	"github.com/10gen/mongo-go-driver/mongo/private/msg"
@@ -56,6 +57,11 @@ func (c *MockConnection) Expired() bool {
 	return c.Dead
 }
 
+// LocalAddr returns nil.
+func (c *MockConnection) LocalAddr() net.Addr {
+	return nil
+}
+
 // Read reads a server response from the MockConnection.
 func (c *MockConnection) Read(ctx context.Context, responseTo int32) (msg.Response, error) {
 	if c.ReadErr != nil {

mongo/internal/servertest/monitor.go

@@ -9,6 +9,7 @@ package servertest
 import (
 	"context"
 	"fmt"
+	"net"
 	"sync"
 
 	"github.com/10gen/mongo-go-driver/bson"
@@ -90,6 +91,10 @@ func (c *fakeMonitorConn) CloseIgnoreError() {
 	_ = c.Close()
 }
 
+func (c *fakeMonitorConn) LocalAddr() net.Addr {
+	return nil
+}
+
 func (c *fakeMonitorConn) MarkDead() {
 	c.Lock()
 	defer c.Unlock()

mongo/private/cluster/monitor_test.go

@@ -9,6 +9,7 @@ package cluster_test
 import (
 	"context"
 	"fmt"
+	"net"
 	"sync"
 	"testing"
 
@@ -77,6 +78,10 @@ func (c *fakeMonitorConn) Model() *model.Conn {
 	return &model.Conn{}
 }
 
+func (c *fakeMonitorConn) LocalAddr() net.Addr {
+	return nil
+}
+
 func (c *fakeMonitorConn) Expired() bool {
 	return c.dead
 }

mongo/private/conn/conn.go

@@ -93,6 +93,8 @@ type Connection interface {
 	Model() *model.Conn
 	// Expired indicates if the connection has expired.
 	Expired() bool
+	// LocalAddr returns the local address of the connection.
+	LocalAddr() net.Addr
 	// Read reads a message from the connection.
 	Read(context.Context, int32) (msg.Response, error)
 	// Write writes a number of messages to the connection.
@@ -176,6 +178,11 @@ func (c *connImpl) Expired() bool {
 	return c.dead
 }
 
+// LocalAddr returns the local address of a connection.
+func (c *connImpl) LocalAddr() net.Addr {
+	return c.rw.LocalAddr()
+}
+
 func (c *connImpl) Read(ctx context.Context, responseTo int32) (msg.Response, error) {
 	if c.dead {
 		return nil, &Error{

mongo/private/conn/conn_test.go

@@ -9,6 +9,7 @@ package conn_test
 import (
 	"context"
 	"fmt"
+	"net"
 	"testing"
 	"time"
 
@@ -207,6 +208,14 @@ func TestConnection_Read_timeout(t *testing.T) {
 	require.False(t, subject.Alive())
 }
 
+func TestConnection_LocalAddr(t *testing.T) {
+	t.Parallel()
+	subject, err := createIntegrationTestConn()
+	require.NoError(t, err)
+	localAddr := subject.LocalAddr()
+	require.NotEqual(t, localAddr, &net.TCPAddr{})
+}
+
 func TestConnection_Read_after_connection_is_dead(t *testing.T) {
 	if testing.Short() {
 		t.Skip("skipping integration test in short mode")