# Multi-Channel Feature - Detailed Design Document

## 1. Overview

SMB3 Multi-Channel enables the use of multiple network connections between client and server, providing increased throughput, network fault tolerance, and automatic failover capabilities. This feature aggregates bandwidth across multiple NICs and provides seamless failover when network paths fail.

## 2. Protocol Specification Reference

    /**
     * Server supports leasing
     */
    public static final int SMB2_GLOBAL_CAP_LEASING = 0x2;

    /**
     * Server supports multi-credit operations
     */
    public static final int SMB2_GLOBAL_CAP_LARGE_MTU = 0x4;

    /**
     * Server supports multi-channel connections
     */
    public static final int SMB2_GLOBAL_CAP_MULTI_CHANNEL = 0x8;

    /**
     * Server supports persistent handles

        // This should fail because localhost doesn't support SMB multi-channel
        // but the method should not throw NullPointerException
        try {
            method.invoke(multiChannelManager, localhost, loopback);
            // If it doesn't throw, that's unexpected for localhost
            fail("Expected CIFSException for localhost multi-channel attempt");
        } catch (java.lang.reflect.InvocationTargetException e) {

- Update `Smb2CreateRequest/Response` for durable contexts

---

### Phase 3: Multi-Channel Support
**Priority: MEDIUM** | **Estimated Effort: 5-6 weeks**

Multi-channel enables using multiple network connections for improved performance and reliability.

#### 3.1 Core Multi-Channel Infrastructure
```
Package: jcifs.internal.smb2.multichannel

import jcifs.CIFSException;
import jcifs.Configuration;

/**
 * SMB3 Multi-Channel Manager.
 *
 * Manages multiple network connections for improved performance and redundancy
 * as specified in the SMB 3.x multi-channel feature.
 */
public class MultiChannelManager {

    private static final Logger log = LoggerFactory.getLogger(MultiChannelManager.class);

    // Multi-channel configuration
    private final Configuration config;

import jcifs.internal.smb2.ServerMessageBlock2Request;
import jcifs.smb.SmbSessionInternal;
import jcifs.smb.SmbTransportInternal;

/**
 * Unit tests for SMB3 Multi-Channel functionality
 *
 * These tests verify the multi-channel implementation without requiring a real SMB server.
 */
@ExtendWith(MockitoExtension.class)
@MockitoSettings(strictness = Strictness.LENIENT)
class MultiChannelIntegrationTest {

        discoverLocalInterfaces();

        // Enable multi-channel if we have multiple usable interfaces
        if (canEnableMultiChannel()) {
            multiChannelEnabled = true;
            establishAdditionalChannels();
            log.info("Multi-channel enabled with {} channels", channels.size());
        }
    }

    /**
     * Check if multi-channel is enabled
     *
     * @return true if enabled

 */
package jcifs.internal.smb2.multichannel;

/**
 * SMB2/SMB3 Multi-Channel capabilities and constants
 */
public final class Smb2ChannelCapabilities {

    private Smb2ChannelCapabilities() {
    }

    /**
     * Multi-channel specific capability flag
     */
    public static final int SMB2_GLOBAL_CAP_MULTI_CHANNEL = 0x00000008;

    /**

    UUID DCERPC_UUID_SYNTAX_NDR = new UUID("8a885d04-1ceb-11c9-9fe8-08002b104860");

    /**
     * First fragment flag - indicates first fragment of a multi-fragment message
     */
    int DCERPC_FIRST_FRAG = 0x01; /* First fragment */
    /**
     * Last fragment flag - indicates last fragment of a multi-fragment message
     */
    int DCERPC_LAST_FRAG = 0x02; /* Last fragment */
    /**

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package jcifs.internal.smb2.multichannel;

/**
 * Load balancing strategies for multi-channel connections
 */
public enum LoadBalancingStrategy {
    /**
     * Round-robin selection through available channels
     */
    ROUND_ROBIN,

    /**