macvlan源码分析

本文主要分析macvlan代码实现。分为如下几部分
a. 分析命令行参数如何传递
b. 分析kernel端代码如何解析命令行参数，并创建macvlan虚接口
c. 分析将网卡up起来时需要设置哪些东西
d. 分析报文接收流程。几种模式下不同的操作
e. 分析报文发送流程。只有bridge模式有特殊操作，其他模式直接从父接口发送出去

下面是比较重要的几点注意事项

a. 如果没有指定mtu，则使用父接口的mtu，如果指定了，则不能大于父接口的mtu。
b. passthru 模式下，不能再创建别的macvlan子接口,如果没有配置非混杂，则也要使能父接口的混杂模式。
c. 在macvlan接口上使能混杂或者allmulticast时，会设置filter为全1，这样就可以接收所有组播/广播报文。否则filter只设置广播或者动态添加的组播报文。
d. 如果没设置mode，则默认为 VEPA。
e. 将macvlan子接口up起来后，会将macvlan子接口的mac地址添加到父接口的单播链表中，以便父接口可以接收到macvlan的报文。如果父接口支持单播过滤(IFF_UNICAST_FLT)，则将macvlan子接口的mac地址添加到父接口网卡内部过滤表中(可通过bridge fdb list查看单播地址列表)，如果父接口不支持单播过滤，则将父接口设置为混杂模式(通过ip -d link show查看promiscuity为1)。这样父接口才会接收目的mac为macvlan子接口的报文。

数据结构

image.png

命令行ip端代码

通过下面命令添加一个macvlan设备
ip link add link ens8 dev macvlan1 type macvlan

命令行填充参数代码如下

    link = ens8
    ifindex = ll_name_to_index(link);
    addattr32(&req->n, sizeof(*req), IFLA_LINK, ifindex);
    req->i.ifi_index = 0; //这里仍然是0
    
    name = dev = macvlan1
    addattr_l(&req->n, sizeof(*req), IFLA_IFNAME, name, strlen(name) + 1);
        
    type = macvlan      
    linkinfo = addattr_nest(&req.n, sizeof(req), IFLA_LINKINFO);
    addattr_l(&req.n, sizeof(req), IFLA_INFO_KIND, type, strlen(type)); 
    //macvlan私有参数
    struct link_util *lu = get_link_kind(type);
    iflatype = IFLA_INFO_DATA;
    data = addattr_nest(&req.n, sizeof(req), iflatype);
    lu->parse_opt(lu, argc, argv, &req.n) //macvlan_parse_opt
        addattr32(n, 1024, IFLA_MACVLAN_MODE, mode);
        addattr16(n, 1024, IFLA_MACVLAN_FLAGS, flags);
        addattr32(n, 1024, IFLA_MACVLAN_MACADDR_MODE, mac_mode);
        //如果 mac_mode 为 MACVLAN_MACADDR_ADD 或者 MACVLAN_MACADDR_DEL，则只添加/删除一个mac
            addattr_l(n, 1024, IFLA_MACVLAN_MACADDR, &mac, ETH_ALEN);
        //如果 mac_mode 为 MACVLAN_MACADDR_SET，则循环添加多个mac
            nmac = addattr_nest(n, 1024, IFLA_MACVLAN_MACADDR_DATA);
                while
                    addattr_l(n, 1024, IFLA_MACVLAN_MACADDR, &mac, ETH_ALEN);
                addattr_nest_end(n, nmac);
    addattr_nest_end(&req.n, data);
    addattr_nest_end(&req.n, linkinfo);

kernel端代码

1. 首先需要加载macvlan驱动

root@ubuntu:~# modprobe macvlan
root@ubuntu:~# lsmod | grep macvlan
macvlan                24576  0

驱动初始化代码如下，主要是注册macvlan_link_ops 到静态链表link_ops，添加macvlan设备时，会查找到此ops进行相关操作。

static struct rtnl_link_ops macvlan_link_ops = {
    .kind       = "macvlan",
    .setup      = macvlan_setup,
    .newlink    = macvlan_newlink,
    .dellink    = macvlan_dellink,
};
 
module_init(macvlan_init_module);
static int __init macvlan_init_module(void)
    macvlan_link_register(&macvlan_link_ops);
        /* common fields */
        ops->priv_size      = sizeof(struct macvlan_dev);
        ops->validate       = macvlan_validate;
        ops->maxtype        = IFLA_MACVLAN_MAX;
        ops->policy     = macvlan_policy;
        ops->changelink     = macvlan_changelink;
        ops->get_size       = macvlan_get_size;
        ops->fill_info      = macvlan_fill_info;
 
        return rtnl_link_register(ops);
            __rtnl_link_register(ops);
                if (rtnl_link_ops_get(ops->kind))
                    return -EEXIST;
                //static LIST_HEAD(link_ops); 为静态全局链表头
                list_add_tail(&ops->list, &link_ops);

1. 执行下面命令添加macvlan设备时，kernel端会调用rtnl_newlink添加macvlan虚接口
   ip link add link ens8 dev macvlan1 type macvlan

static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh)
    nlmsg_parse(nlh, sizeof(*ifm), tb, IFLA_MAX, ifla_policy);
    nla_strlcpy(ifname, tb[IFLA_IFNAME], IFNAMSIZ);
    ifm = nlmsg_data(nlh);
    //ifm->ifi_index 在创建macvlan时为0
    if (ifm->ifi_index > 0)
        dev = __dev_get_by_index(net, ifm->ifi_index);
    else {
        if (ifname[0])
            dev = __dev_get_by_name(net, ifname); //此时还没有创建此dev，所以dev为空
        else
            dev = NULL;
    }
    //获取嵌套的 linkinfo
    nla_parse_nested(linkinfo, IFLA_INFO_MAX, tb[IFLA_LINKINFO], ifla_info_policy);
    //获取 kind，此处为 macvlan
    nla_strlcpy(kind, linkinfo[IFLA_INFO_KIND], sizeof(kind));
    ops = rtnl_link_ops_get(kind); //对于macvlan来说，macvlan_link_ops
    if (ops) {
        //获取 kind 私有数据
        if (ops->maxtype && linkinfo[IFLA_INFO_DATA]) {
            err = nla_parse_nested(attr, ops->maxtype,
                           linkinfo[IFLA_INFO_DATA],
                           ops->policy);
            if (err < 0)
                return err;
            data = attr;
        }
        //调用 macvlan_validate 验证私有数据
        if (ops->validate) {
            err = ops->validate(tb, data);
            if (err < 0)
                return err;
        }
    }
    //获取 net，如果没有指定其他net namespace，则使用当前net
    dest_net = rtnl_link_get_net(net, tb);
        if (tb[IFLA_NET_NS_PID])
            net = get_net_ns_by_pid(nla_get_u32(tb[IFLA_NET_NS_PID]));
        else if (tb[IFLA_NET_NS_FD])
            net = get_net_ns_by_fd(nla_get_u32(tb[IFLA_NET_NS_FD]));
        else
            net = get_net(src_net);
        return net;
    dev = rtnl_create_link(dest_net, ifname, name_assign_type, ops, tb);
        //获取tx/rx队列个数，如果没配置，则默认为1
        if (tb[IFLA_NUM_TX_QUEUES])
            num_tx_queues = nla_get_u32(tb[IFLA_NUM_TX_QUEUES]);
        else if (ops->get_num_tx_queues)
            num_tx_queues = ops->get_num_tx_queues();
 
        if (tb[IFLA_NUM_RX_QUEUES])
            num_rx_queues = nla_get_u32(tb[IFLA_NUM_RX_QUEUES]);
        else if (ops->get_num_rx_queues)
            num_rx_queues = ops->get_num_rx_queues();
        //ops->priv_size = sizeof(struct macvlan_dev);
        dev = alloc_netdev_mqs(ops->priv_size, ifname, name_assign_type, ops->setup, num_tx_queues, num_rx_queues);
            alloc_size = sizeof(struct net_device);
            if (sizeof_priv) {
                /* ensure 32-byte alignment of private area */
                alloc_size = ALIGN(alloc_size, NETDEV_ALIGN);
                alloc_size += sizeof_priv;
            }
            /* ensure 32-byte alignment of whole construct */
            alloc_size += NETDEV_ALIGN - 1;
 
            p = kzalloc(alloc_size, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
            dev = PTR_ALIGN(p, NETDEV_ALIGN);
            dev_mc_init(dev);
            dev_uc_init(dev);
            dev_net_set(dev, &init_net);
            dev->gso_max_size = GSO_MAX_SIZE;
            dev->gso_max_segs = GSO_MAX_SEGS;
            dev->gso_min_segs = 0;
            setup(dev); //macvlan_setup
                macvlan_common_setup(dev);
                    ether_setup(dev);
                        dev->header_ops     = &eth_header_ops;
                        dev->type       = ARPHRD_ETHER;
                        dev->hard_header_len    = ETH_HLEN;
                        dev->mtu        = ETH_DATA_LEN;
                        dev->addr_len       = ETH_ALEN;
                        dev->tx_queue_len   = 1000; /* Ethernet wants good queues */
                        dev->flags      = IFF_BROADCAST|IFF_MULTICAST;
                        dev->priv_flags     |= IFF_TX_SKB_SHARING;
                        memset(dev->broadcast, 0xFF, ETH_ALEN);
                    dev->priv_flags        &= ~IFF_TX_SKB_SHARING;
                    netif_keep_dst(dev);
                    dev->priv_flags        |= IFF_UNICAST_FLT;
                    dev->netdev_ops     = &macvlan_netdev_ops;
                    dev->destructor     = free_netdev;
                    dev->header_ops     = &macvlan_hard_header_ops;
                    dev->ethtool_ops    = &macvlan_ethtool_ops;
                dev->tx_queue_len   = 0;
            strcpy(dev->name, name);
        dev_net_set(dev, net);
        dev->rtnl_link_ops = ops;
        dev->rtnl_link_state = RTNL_LINK_INITIALIZING;
        //下面的参数，如果指定了就赋值即可
        if (tb[IFLA_MTU])
            dev->mtu = nla_get_u32(tb[IFLA_MTU]);
        if (tb[IFLA_ADDRESS]) {
            memcpy(dev->dev_addr, nla_data(tb[IFLA_ADDRESS]),
                    nla_len(tb[IFLA_ADDRESS]));
            dev->addr_assign_type = NET_ADDR_SET;
        }
        if (tb[IFLA_BROADCAST])
            memcpy(dev->broadcast, nla_data(tb[IFLA_BROADCAST]),
                    nla_len(tb[IFLA_BROADCAST]));
        if (tb[IFLA_TXQLEN])
            dev->tx_queue_len = nla_get_u32(tb[IFLA_TXQLEN]);
        if (tb[IFLA_OPERSTATE])
            set_operstate(dev, nla_get_u8(tb[IFLA_OPERSTATE]));
        if (tb[IFLA_LINKMODE])
            dev->link_mode = nla_get_u8(tb[IFLA_LINKMODE]);
        if (tb[IFLA_GROUP])
            dev_set_group(dev, nla_get_u32(tb[IFLA_GROUP]));    
    if (ops->newlink) {
        ops->newlink(net, dev, tb, data); //macvlan_newlink
            macvlan_common_newlink(src_net, dev, tb, data);
                struct macvlan_dev *vlan = netdev_priv(dev);
                struct macvlan_port *port;
                struct net_device *lowerdev;
                //IFLA_LINK 表示macvlan的父接口，如果没有指定肯定不能创建
                if (!tb[IFLA_LINK])
                    return -EINVAL;
                //获取父接口，会把父接口赋给 macvlan->lowerdev 保存下来，以便指定此macvlan虚拟接口的父接口是哪个设备
                struct net_device *lowerdev = __dev_get_by_index(src_net, nla_get_u32(tb[IFLA_LINK]));
                //如果基于macvlan接口创建另一个macvlan接口，则使用真实的父接口
                if (netif_is_macvlan(lowerdev)) //return dev->priv_flags & IFF_MACVLAN;
                    lowerdev = macvlan_dev_real_dev(lowerdev);
                        struct macvlan_dev *macvlan = netdev_priv(dev);
                        return macvlan->lowerdev;
                //如果没有指定mtu，则使用父接口的mtu
                //如果指定了，则不能大于父接口的mtu
                if (!tb[IFLA_MTU])
                    dev->mtu = lowerdev->mtu;
                else if (dev->mtu > lowerdev->mtu)
                    return -EINVAL;
                //如果没有指定mac地址，则随机生成一个
                if (!tb[IFLA_ADDRESS])
                    eth_hw_addr_random(dev);
                        dev->addr_assign_type = NET_ADDR_RANDOM;
                        eth_random_addr(dev->dev_addr);
                            get_random_bytes(addr, ETH_ALEN);
                            addr[0] &= 0xfe;    /* clear multicast bit */
                            addr[0] |= 0x02;    /* set local assignment bit (IEEE802) */
                //如果父接口没有此标志 IFF_MACVLAN_PORT，说明是第一个给这个设备添加macvlan子接口
                if (!macvlan_port_exists(lowerdev)) { //#define macvlan_port_exists(dev) (dev->priv_flags & IFF_MACVLAN_PORT)
                    macvlan_port_create(lowerdev);
                        //如果不是 ether 类型或者是 loopback 类型，则返回错误
                        if (dev->type != ARPHRD_ETHER || dev->flags & IFF_LOOPBACK)
                            return -EINVAL;
                        struct macvlan_port *port = kzalloc(sizeof(*port), GFP_KERNEL);
                        port->passthru = false;
                        port->dev = dev;
                        //初始化链表，用于存放所有的macvlan子接口
                        INIT_LIST_HEAD(&port->vlans);
                        //初始化 hash 链表，用于存放所有的 up 状态的子接口(调用了 _dev_open)
                        for (i = 0; i < MACVLAN_HASH_SIZE; i++)
                            INIT_HLIST_HEAD(&port->vlan_hash[i]);
                        //初始化 hash 链表
                        for (i = 0; i < MACVLAN_HASH_SIZE; i++)
                            INIT_HLIST_HEAD(&port->vlan_source_hash[i]);
                        //组播/广播报文会放在链表，由 macvlan_process_broadcast 发给所有的up状态的macvlan子接口
                        skb_queue_head_init(&port->bc_queue);
                        INIT_WORK(&port->bc_work, macvlan_process_broadcast);
                        
                        //注册收包函数，这样在 netif_receive_skb 收到报文会调用 macvlan_handle_frame
                        err = netdev_rx_handler_register(dev, macvlan_handle_frame, port);
                                rcu_assign_pointer(dev->rx_handler_data, rx_handler_data);
                                rcu_assign_pointer(dev->rx_handler, rx_handler);
                        if (err)
                            kfree(port);
                        else
                            //设置标志位
                            dev->priv_flags |= IFF_MACVLAN_PORT;
                port = macvlan_port_get_rtnl(lowerdev); //rtnl_dereference(dev->rx_handler_data);
                /* Only 1 macvlan device can be created in passthru mode */
                //passthru 模式下，不能再创建别的macvlan子接口
                if (port->passthru)
                    return -EINVAL;
                vlan->lowerdev = lowerdev;
                vlan->dev      = dev;
                vlan->port     = port;
                vlan->set_features = MACVLAN_FEATURES;
                vlan->nest_level = dev_get_nest_level(lowerdev, netif_is_macvlan) + 1;
                vlan->mode     = MACVLAN_MODE_VEPA;
                if (data && data[IFLA_MACVLAN_MODE])
                    vlan->mode = nla_get_u32(data[IFLA_MACVLAN_MODE]);
                if (data && data[IFLA_MACVLAN_FLAGS])
                    vlan->flags = nla_get_u16(data[IFLA_MACVLAN_FLAGS]);
                
                if (vlan->mode == MACVLAN_MODE_PASSTHRU) {
                    //port->count不为0，说明已经有其他模式的macvlan子接口了，这种情况也不允许
                    if (port->count)
                        return -EINVAL;
                    //设置标志位
                    port->passthru = true;
                    //将父接口的mac地址，赋给 passthru 模式的macvlan子接口
                    eth_hw_addr_inherit(dev, lowerdev);
                        dst->addr_assign_type = src->addr_assign_type;
                        ether_addr_copy(dst->dev_addr, src->dev_addr);
                }
                
                if (data && data[IFLA_MACVLAN_MACADDR_MODE]) {
                    if (vlan->mode != MACVLAN_MODE_SOURCE)
                        return -EINVAL;
                    macmode = nla_get_u32(data[IFLA_MACVLAN_MACADDR_MODE]);
                    macvlan_changelink_sources(vlan, macmode, data);
                        if (mode == MACVLAN_MACADDR_ADD) {
                            macvlan_hash_add_source(vlan, addr);
                                struct macvlan_port *port = vlan->port;
                                struct macvlan_source_entry *entry = kmalloc(sizeof(*entry), GFP_KERNEL);
                                ether_addr_copy(entry->addr, addr);
                                entry->vlan = vlan;
                                h = &port->vlan_source_hash[macvlan_eth_hash(addr)];
                                hlist_add_head_rcu(&entry->hlist, h);
                                vlan->macaddr_count++;
 
                //增加macvlan子接口个数的计数
                port->count += 1;
                //注册macvlan子接口
                register_netdevice(dev);
                //设置标志位
                dev->priv_flags |= IFF_MACVLAN;
                netdev_upper_dev_link(lowerdev, dev);
                    __netdev_upper_dev_link(dev, upper_dev, false, NULL);
                //将macvlan子接口添加到父接口的 vlans 链表
                list_add_tail_rcu(&vlan->list, &port->vlans);
                netif_stacked_transfer_operstate(lowerdev, dev);
    rtnl_configure_link(dev, ifm);
        old_flags = dev->flags;
        if (ifm && (ifm->ifi_flags || ifm->ifi_change)) {
            err = __dev_change_flags(dev, rtnl_dev_combine_flags(dev, ifm));
            if (err < 0)
                return err;
        }
 
        dev->rtnl_link_state = RTNL_LINK_INITIALIZED;

1. 通过ip命令将网卡up起来，或者通过socket ioctl操作网卡时，都会调用dev_change_flags进行相关操作

 
#通过 ip 命令修改网卡配置时
#ip link set dev xxx up
    req->i.ifi_change |= IFF_UP;
    req->i.ifi_flags |= IFF_UP;
 
static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh)
    dev = __dev_get_by_index(net, ifm->ifi_index);
    do_setlink(skb, dev, ifm, tb, ifname, status);
        if (ifm->ifi_flags || ifm->ifi_change) {
            err = dev_change_flags(dev, rtnl_dev_combine_flags(dev, ifm));
 
#通过socket修改网卡配置时
static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
    if (cmd >= SIOCDEVPRIVATE && cmd <= (SIOCDEVPRIVATE + 15)) {
        dev_ioctl(net, cmd, argp);
            switch (cmd) {
            case SIOCSIFFLAGS:
                if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
                    return -EPERM;
                dev_load(net, ifr.ifr_name);
                dev_ifsioc(net, &ifr, cmd);
                    struct net_device *dev = __dev_get_by_name(net, ifr->ifr_name);
                    switch (cmd) {
                    case SIOCSIFFLAGS:  /* Set interface flags */
                        dev_change_flags(dev, ifr->ifr_flags);
//都会调用dev_change_flags进行相关操作
int dev_change_flags(struct net_device *dev, unsigned int flags)
    __dev_change_flags(dev, flags); 
        unsigned int old_flags = dev->flags;
        dev->flags = (flags & (IFF_DEBUG | IFF_NOTRAILERS | IFF_NOARP |
               IFF_DYNAMIC | IFF_MULTICAST | IFF_PORTSEL | IFF_AUTOMEDIA)) |
             (dev->flags & (IFF_UP | IFF_VOLATILE | IFF_PROMISC | IFF_ALLMULTI));
        if ((old_flags ^ flags) & IFF_MULTICAST)
            dev_change_rx_flags(dev, IFF_MULTICAST);
                ops->ndo_change_rx_flags(dev, flags); //macvlan_change_rx_flags
        dev_set_rx_mode(dev);
        
        //新旧flag不一样时，如果旧flag是up，说明新flag是down，需要调用 __dev_close
        //如果旧flag不是up，说明新flag是up，需要调用 __dev_open
        if ((old_flags ^ flags) & IFF_UP)
            ret = ((old_flags & IFF_UP) ? __dev_close : __dev_open)(dev);
            static int __dev_open(struct net_device *dev)
                const struct net_device_ops *ops = dev->netdev_ops;
                ops->ndo_open(dev); //对于macvlan设备来说，macvlan_open
                    struct macvlan_dev *vlan = netdev_priv(dev);
                    struct net_device *lowerdev = vlan->lowerdev;
                    int err;
                    //passthrough 模式下，如果没有配置非混杂，则也要使能父接口的混杂模式
                    if (vlan->port->passthru) {
                        if (!(vlan->flags & MACVLAN_FLAG_NOPROMISC)) {
                            err = dev_set_promiscuity(lowerdev, 1);
                            if (err < 0)
                                goto out;
                        }
                        goto hash_add;
                    }
                    //和硬件offload相关的，暂时不管
                    if (lowerdev->features & NETIF_F_HW_L2FW_DOFFLOAD &&
                        dev->rtnl_link_ops == &macvlan_link_ops) {
                        vlan->fwd_priv =
                              lowerdev->netdev_ops->ndo_dfwd_add_station(lowerdev, dev);
 
                        /* If we get a NULL pointer back, or if we get an error
                         * then we should just fall through to the non accelerated path
                         */
                        if (IS_ERR_OR_NULL(vlan->fwd_priv)) {
                            vlan->fwd_priv = NULL;
                        } else
                            return 0;
                    }
                    if (macvlan_addr_busy(vlan->port, dev->dev_addr))
                        if (ether_addr_equal_64bits(port->dev->dev_addr, addr))
                            return 1;
                        if (macvlan_hash_lookup(port, addr))
                            return 1;
                        return 0;
                        goto out;
                    //将macvlan子接口的mac地址添加到父接口的单播链表中，以便父接口可以接收到macvlan的报文
                    err = dev_uc_add(lowerdev, dev->dev_addr);
                         __hw_addr_add(&dev->uc, addr, dev->addr_len, NETDEV_HW_ADDR_T_UNICAST);
                         __dev_set_rx_mode(dev);
                            //如果dev不支持单播过滤功能，即IFF_UNICAST_FLT
                            if (!(dev->priv_flags & IFF_UNICAST_FLT)) {
                                /* Unicast addresses changes may only happen under the rtnl,
                                 * therefore calling __dev_set_promiscuity here is safe.
                                 */
                                 //单播链表不为空，并且uc_promisc为false，则使能混杂模式。
                                //对于macvlan设备来说，这里就是使能父接口的混杂模式
                                if (!netdev_uc_empty(dev) && !dev->uc_promisc) {
                                    __dev_set_promiscuity(dev, 1, false);
                                    dev->uc_promisc = true;
                                } else if (netdev_uc_empty(dev) && dev->uc_promisc) {
                                    __dev_set_promiscuity(dev, -1, false);
                                    dev->uc_promisc = false;
                                }
                            }
                    if (dev->flags & IFF_ALLMULTI) {
                        err = dev_set_allmulti(lowerdev, 1);
                        if (err < 0)
                            goto del_unicast;
                    }
                hash_add:
                    //macvlan设备open后，将设备添加到父接口的 vlan_hash hash链表中
                    macvlan_hash_add(vlan);
                        struct macvlan_port *port = vlan->port;
                        const unsigned char *addr = vlan->dev->dev_addr;
                        u32 idx = macvlan_eth_hash(addr);
                        hlist_add_head_rcu(&vlan->hlist, &port->vlan_hash[idx]);
                    return 0;
 
        if ((flags ^ dev->gflags) & IFF_PROMISC) {
            int inc = (flags & IFF_PROMISC) ? 1 : -1;
            unsigned int old_flags = dev->flags;
 
            dev->gflags ^= IFF_PROMISC;
 
            if (__dev_set_promiscuity(dev, inc, false) >= 0)
                dev->flags |= IFF_PROMISC;
                dev->promiscuity += inc;
                if (dev->flags != old_flags)
                    dev_set_rx_mode(dev);
        }
        if ((flags ^ dev->gflags) & IFF_ALLMULTI) {
            int inc = (flags & IFF_ALLMULTI) ? 1 : -1;
            dev->gflags ^= IFF_ALLMULTI;
            __dev_set_allmulti(dev, inc, false);
                dev->flags |= IFF_ALLMULTI;
                dev->allmulti += inc;
                if (dev->flags ^ old_flags) {
                    dev_change_rx_flags(dev, IFF_ALLMULTI);
                        ops->ndo_change_rx_flags(dev, flags); //macvlan_change_rx_flags
                            //如果macvlan使能了 ALLMULTI，则也要设置父接口使能 ALLMULTI
                            struct macvlan_dev *vlan = netdev_priv(dev);
                            //取出父接口
                            struct net_device *lowerdev = vlan->lowerdev;
                            if (dev->flags & IFF_UP) {
                                if (change & IFF_ALLMULTI)
                                    dev_set_allmulti(lowerdev, dev->flags & IFF_ALLMULTI ? 1 : -1);
                                        __dev_set_allmulti(dev, inc, true);
                    dev_set_rx_mode(dev);
                        __dev_set_rx_mode(dev);
                            ops->ndo_set_rx_mode(dev); //macvlan_set_mac_lists
                                //如果使能了混杂模式或者allmulti，则设置 vlan->mc_filter 所有 bit 位为1，表示可以接收所有报文
                                if (dev->flags & (IFF_PROMISC | IFF_ALLMULTI)) {
                                    bitmap_fill(vlan->mc_filter, MACVLAN_MC_FILTER_SZ);
                                } else {
                                    struct netdev_hw_addr *ha;
                                    DECLARE_BITMAP(filter, MACVLAN_MC_FILTER_SZ);
                                    //如果没有使能混杂模式或者allmulti，则只设置设备的dev->mc组播列表地址和广播地址
                                    bitmap_zero(filter, MACVLAN_MC_FILTER_SZ);
                                    netdev_for_each_mc_addr(ha, dev) {
                                        __set_bit(mc_hash(vlan, ha->addr), filter);
                                    }
 
                                    __set_bit(mc_hash(vlan, dev->broadcast), filter);
 
                                    bitmap_copy(vlan->mc_filter, filter, MACVLAN_MC_FILTER_SZ);
                                }
                                //将macvlan子接口的组播列表和单播列表传递给父接口，以便父接口可以接收到这些报文
                                dev_uc_sync(vlan->lowerdev, dev);
                                dev_mc_sync(vlan->lowerdev, dev);

1. 报文接收流程
   在协议栈入口函数__netif_receive_skb_core中，如果接收数据包的dev的rx_handler不为空，说明需要进行处理，对于macvlan来说，rx_handler为macvlan_handle_frame。

对于组播/广播报文：
bridge模式下的macvlan子接口发出去的报文，经过外部交换机反射回来后，会被主接口和其他模式为vepa的macvlan子接口收到。
vepa模式下的macvlan子接口发出去的报文，经过外部交换机反射回来后，会被主接口和其他模式为vepa和bridge的macvlan子接口收到。
private模式下的macvlan子接口发出去的报文，经过外部交换机反射回来后，只会被发送报文的macvlan子接口收到。
pathrough模式下的macvlan子接口发出去的报文，经过外部交换机反射回来后，只会被发送报文的macvlan子接口收到。

static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc)
another_round:
    skb->skb_iif = skb->dev->ifindex;
    ...
    ...
    //对于macvlan来说，macvlan_handle_frame
    rx_handler = rcu_dereference(skb->dev->rx_handler);
    if (rx_handler) {
        if (pt_prev) {
            ret = deliver_skb(skb, pt_prev, orig_dev);
            pt_prev = NULL;
        }
        switch (rx_handler(&skb)) {
        //说明报文被释放了
        case RX_HANDLER_CONSUMED:
            ret = NET_RX_SUCCESS;
            goto out;
        //说明报文找到了目的地，需要重新走一遍协议栈
        case RX_HANDLER_ANOTHER:
            goto another_round;
        case RX_HANDLER_EXACT:
            deliver_exact = true;
        //表明报文被复制一份处理，可以后续流程
        case RX_HANDLER_PASS:
            break;
        default:
            BUG();
        }
    }
 
static rx_handler_result_t macvlan_handle_frame(struct sk_buff **pskb)
    struct macvlan_port *port = macvlan_port_get_rcu(skb->dev);
        rcu_dereference(dev->rx_handler_data);
    //组播/广播处理流程
    if (is_multicast_ether_addr(eth->h_dest)) {
        skb = ip_check_defrag(skb, IP_DEFRAG_MACVLAN);
        if (!skb)
            return RX_HANDLER_CONSUMED;
        eth = eth_hdr(skb);
        macvlan_forward_source(skb, port, eth->h_source);
        //根据源mac到主接口的 vlan_hash 查找
        src = macvlan_hash_lookup(port, eth->h_source);
        if (src && src->mode != MACVLAN_MODE_VEPA &&
            src->mode != MACVLAN_MODE_BRIDGE) {
            /* forward to original port. */
            struct macvlan_dev *vlan = src;
            ret = macvlan_broadcast_one(skb, vlan, eth, 0) ?:netif_rx(skb);
            handle_res = RX_HANDLER_CONSUMED;
            goto out;
        }
 
        MACVLAN_SKB_CB(skb)->src = src;
        macvlan_broadcast_enqueue(port, skb);
            nskb = skb_clone(skb, GFP_ATOMIC);
            //将skb复制一份，存入队列
            if (skb_queue_len(&port->bc_queue) < MACVLAN_BC_QUEUE_LEN) {
                __skb_queue_tail(&port->bc_queue, nskb);
            //bc_work 为 macvlan_process_broadcast，从队列取出报文，根据macvlan mode进行转发
            schedule_work(&port->bc_work);
        return RX_HANDLER_PASS;
    }
    //单播处理流程
    macvlan_forward_source(skb, port, eth->h_source);
    
    if (port->passthru)
        //list_first_or_null_rcu 获取链表的第一个元素，对于 passthru 模式来说，也只有一个 macvlan 子接口
        vlan = list_first_or_null_rcu(&port->vlans, struct macvlan_dev, list);
    else
        //根据目的mac 到父接口的 hash 链表 vlan_hash 中查找是否有匹配的macvlan子接口的mac
        vlan = macvlan_hash_lookup(port, eth->h_dest);
    //如果没有找到合适的macvlan子接口，则返回 RX_HANDLER_PASS，表明此报文没有被macvlan处理，可以继续后面协议栈流程
    if (vlan == NULL)
        return RX_HANDLER_PASS;
 
    //目的地是此设备，但是设备是down的，则释放skb，并返回RX_HANDLER_CONSUMED，表明报文已经被释放
    dev = vlan->dev;
    if (unlikely(!(dev->flags & IFF_UP))) {
        kfree_skb(skb);
        return RX_HANDLER_CONSUMED;
    }
    len = skb->len + ETH_HLEN;
    skb = skb_share_check(skb, GFP_ATOMIC);
    if (!skb) {
        ret = NET_RX_DROP;
        handle_res = RX_HANDLER_CONSUMED;
        goto out;
    }
    //将真正的目的设备 dev 赋给 skb->dev
    skb->dev = dev;
    //表明报文是发给本机的
    skb->pkt_type = PACKET_HOST;
 
    ret = NET_RX_SUCCESS;
    //说明报文找到了目的地，需要重新走一遍协议栈
    handle_res = RX_HANDLER_ANOTHER;
out:
    //增加报文计数
    macvlan_count_rx(vlan, len, ret == NET_RX_SUCCESS, false);
    return handle_res;
 
#组播/广播处理流程
static void macvlan_process_broadcast(struct work_struct *w)
    struct macvlan_port *port = container_of(w, struct macvlan_port, bc_work);
    struct sk_buff *skb;
    struct sk_buff_head list;
 
    __skb_queue_head_init(&list);
    //将链表port->bc_queue上的报文全部删除，存入本地链表 list
    spin_lock_bh(&port->bc_queue.lock);
    skb_queue_splice_tail_init(&port->bc_queue, &list);
    spin_unlock_bh(&port->bc_queue.lock);
 
    //从本地链表list中循环取出报文进行转发
    while ((skb = __skb_dequeue(&list))) {
        const struct macvlan_dev *src = MACVLAN_SKB_CB(skb)->src;
        rcu_read_lock();
        //src为空，说明报文是从外部主机发过来的，此时，如果macvlan子接口都可以收到此
        //报文(目的mac还得满足 vlan->mc_filter)
        if (!src)
            //外部来的报文，不会发送到模式为 source 的macvlan子接口
            /* frame comes from an external address */
            macvlan_broadcast(skb, port, NULL,
                      MACVLAN_MODE_PRIVATE |
                      MACVLAN_MODE_VEPA    |
                      MACVLAN_MODE_PASSTHRU|
                      MACVLAN_MODE_BRIDGE);
        //如果src不为空，说明是本机发出去的报文，经过外面交换机处理后又收到了。
        //如果发送此报文的macvlan子接口模式为 MACVLAN_MODE_VEPA，则将
        //报文发送给模式为 MACVLAN_MODE_VEPA 和 MACVLAN_MODE_BRIDGE 的macvlan子接口
        else if (src->mode == MACVLAN_MODE_VEPA)
            /* flood to everyone except source */
            macvlan_broadcast(skb, port, src->dev, MACVLAN_MODE_VEPA | MACVLAN_MODE_BRIDGE);
        else
            /*
             * flood only to VEPA ports, bridge ports
             * already saw the frame on the way out.
             */
            //如果发送此报文的macvlan子接口模式不为 MACVLAN_MODE_VEPA，则将
            //报文发送给模式为 MACVLAN_MODE_VEPA 的 macvlan 子接口
            macvlan_broadcast(skb, port, src->dev, MACVLAN_MODE_VEPA);
                      
        rcu_read_unlock();
        kfree_skb(skb);
    }
 
static void macvlan_broadcast(struct sk_buff *skb, const struct macvlan_port *port,
                  struct net_device *src, enum macvlan_mode mode)
{
    const struct ethhdr *eth = eth_hdr(skb);
    const struct macvlan_dev *vlan;
    struct sk_buff *nskb;
    unsigned int i;
    int err;
    unsigned int hash;
 
    if (skb->protocol == htons(ETH_P_PAUSE))
        return;
 
    for (i = 0; i < MACVLAN_HASH_SIZE; i++) {
        hlist_for_each_entry_rcu(vlan, &port->vlan_hash[i], hlist) {
            if (vlan->dev == src || !(vlan->mode & mode))
                continue;
 
            hash = mc_hash(vlan, eth->h_dest);
            //目的mac得匹配vlan->mc_filter，对于ipv4广播来说，已经设置好了。
            //对于ipv4组播和ipv6组播，需要使能混杂模式或者allmulticast。
            if (!test_bit(hash, vlan->mc_filter))
                continue;
 
            err = NET_RX_DROP;
            nskb = skb_clone(skb, GFP_ATOMIC);
            if (likely(nskb))
                err = macvlan_broadcast_one(nskb, vlan, eth, mode == MACVLAN_MODE_BRIDGE) ?: netif_rx_ni(nskb);
            macvlan_count_rx(vlan, skb->len + ETH_HLEN,
                     err == NET_RX_SUCCESS, true);
        }
    }
}

1. 报文发送流程
   从macvlan虚接口发送报文时，调用函数macvlan_start_xmit

static netdev_tx_t macvlan_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
    unsigned int len = skb->len;
    int ret;
    struct macvlan_dev *vlan = netdev_priv(dev);
 
    if (unlikely(netpoll_tx_running(dev)))
        return macvlan_netpoll_send_skb(vlan, skb);
    //和网卡offload相关的，暂时不看
    if (vlan->fwd_priv) {
        skb->dev = vlan->lowerdev;
        ret = dev_queue_xmit_accel(skb, vlan->fwd_priv);
    } else {//直接看这个流程
        ret = macvlan_queue_xmit(skb, dev);
    }
 
    if (likely(ret == NET_XMIT_SUCCESS || ret == NET_XMIT_CN)) {
        struct vlan_pcpu_stats *pcpu_stats;
 
        pcpu_stats = this_cpu_ptr(vlan->pcpu_stats);
        u64_stats_update_begin(&pcpu_stats->syncp);
        pcpu_stats->tx_packets++;
        pcpu_stats->tx_bytes += len;
        u64_stats_update_end(&pcpu_stats->syncp);
    } else {
        this_cpu_inc(vlan->pcpu_stats->tx_dropped);
    }
    return ret;
}
在bridge模式下，如果是广播/组播，则将报文发送给其他所
有macvlan子接口，然后从父接口发送出去。如果是单播，则
查找目的mac是否为其他macvlan子接口的地址，如果找到
了，则发送给这个子接口，不再通过父接口发送出去。如果
查找不到，说明是外部的报文，需要跳转到xmit_world，通过
父接口发送到外部。
其他模式下，直接从父接口发送出去。
static int macvlan_queue_xmit(struct sk_buff *skb, struct net_device *dev)
{
    const struct macvlan_dev *vlan = netdev_priv(dev);
    const struct macvlan_port *port = vlan->port;
    const struct macvlan_dev *dest;
    //macvlan 为 bridge 模式
    if (vlan->mode == MACVLAN_MODE_BRIDGE) {
        const struct ethhdr *eth = (void *)skb->data;
        //如果是目的mac为组播，则需要转发给同一个父接口上的其他所有macvlan子接口，不包括本身，也不包括父接口
        //最后还有跳转到xmit_world，通过父接口发送到外部
        /* send to other bridge ports directly */
        if (is_multicast_ether_addr(eth->h_dest)) {
            macvlan_broadcast(skb, port, dev, MACVLAN_MODE_BRIDGE);
            goto xmit_world;
        }
        //如果是目的mac为单播，则查找目的mac是否为其他macvlan子接口的地址，如果找到了，则发送给这个子接口，不再通过父接口发送出去。
        //如果查找不到，说明是外部的报文，需要跳转到xmit_world，通过父接口发送到外部
        dest = macvlan_hash_lookup(port, eth->h_dest);
        if (dest && dest->mode == MACVLAN_MODE_BRIDGE) {
            /* send to lowerdev first for its network taps */
            dev_forward_skb(vlan->lowerdev, skb);
 
            return NET_XMIT_SUCCESS;
        }
    }
xmit_world:
    skb->dev = vlan->lowerdev;
    return dev_queue_xmit(skb);
}

也可参考：macvlan源码分析 - 简书 (jianshu.com)