MSSQL: Minor refactor (#113976)

* Moving things around

* Copy parseURL function to where it's used

* Update test

* Remove experimental-strip-types

* Revert "Remove experimental-strip-types"

This reverts commit 70fbc1c0cd.

* Trigger build

pkg/tsdb/mssql/sqleng/proxy_test.go

@@ -0,0 +1,77 @@
+package sqleng
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"net"
+	"testing"
+
+	mssql "github.com/microsoft/go-mssqldb"
+	"github.com/stretchr/testify/require"
+	"golang.org/x/net/proxy"
+)
+
+type testDialer struct {
+	Host string
+}
+
+func (d *testDialer) Dial(network, addr string) (c net.Conn, err error) {
+	return nil, fmt.Errorf("test-dialer: Dial is not functional")
+}
+
+func (d *testDialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
+	hostWithPort := d.HostName() + ":1433"
+	if address != hostWithPort {
+		return nil, fmt.Errorf("test-dialer: address does not match hostname")
+	}
+	return nil, fmt.Errorf("test-dialer: DialContext is not functional")
+}
+
+func (d *testDialer) HostName() string {
+	return d.Host
+}
+
+var _ proxy.Dialer = (&testDialer{})
+
+func TestMSSQLProxyDriver(t *testing.T) {
+	t.Run("Connector should use dialer context that routes through the socks proxy to db", func(t *testing.T) {
+		host := "127.0.0.1"
+		cnnstr := fmt.Sprintf("server=%s;port=1433;user id=sa;password=yourStrong(!)Password;database=db", host)
+		connector, err := mssql.NewConnector(cnnstr)
+		require.NoError(t, err)
+
+		td := testDialer{
+			Host: host,
+		}
+		dialer, err := newMSSQLProxyDialer("%s", &td)
+		require.NoError(t, err)
+
+		connector.Dialer = (dialer)
+
+		db := sql.OpenDB(connector)
+		err = db.Ping()
+
+		require.Contains(t, err.Error(), "test-dialer: DialContext is not functional")
+	})
+
+	t.Run("Connector should use hostname rather than attempting to resolve IP", func(t *testing.T) {
+		host := "www.grafana.com"
+		cnnstr := fmt.Sprintf("server=%s;port=1433;user id=sa;password=yourStrong(!)Password;database=db", host)
+		connector, err := mssql.NewConnector(cnnstr)
+		require.NoError(t, err)
+
+		td := testDialer{
+			Host: host,
+		}
+		dialer, err := newMSSQLProxyDialer(host, &td)
+		require.NoError(t, err)
+
+		connector.Dialer = (dialer)
+
+		db := sql.OpenDB(connector)
+		err = db.Ping()
+
+		require.Contains(t, err.Error(), "test-dialer: DialContext is not functional")
+	})
+}