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  • Openvswitch原理与代码分析(3): openvswitch内核模块的加载

     

    上一节我们讲了ovs-vswitchd，其中虚拟网桥初始化的时候，对调用内核模块来添加虚拟网卡。

     

    我们从openvswitch内核模块的加载过程，来看这个过程。

     

    在datapath/datapath.c中会调用module_init(dp_init);来初始化内核模块。

     

    1. static int __init dp_init(void)
    2. {
    3.    int err;
    4.  
    5.    BUILD_BUG_ON(sizeof(struct ovs_skb_cb) > FIELD_SIZEOF(struct sk_buff, cb));
    6.  
    7.    pr_info("Open vSwitch switching datapath %s ", VERSION);
    8.  
    9.    err = compat_init();
    10.    if (err)
    11.       goto error;
    12.  
    13.    err = action_fifos_init();
    14.    if (err)
    15.       goto error_compat_exit;
    16.  
    17.    err = ovs_internal_dev_rtnl_link_register();
    18.    if (err)
    19.       goto error_action_fifos_exit;
    20.  
    21.    err = ovs_flow_init();
    22.    if (err)
    23.       goto error_unreg_rtnl_link;
    24.  
    25.    err = ovs_vport_init();
    26.    if (err)
    27.       goto error_flow_exit;
    28.  
    29.    err = register_pernet_device(&ovs_net_ops);
    30.    if (err)
    31.       goto error_vport_exit;
    32.  
    33.    err = register_netdevice_notifier(&ovs_dp_device_notifier);
    34.    if (err)
    35.       goto error_netns_exit;
    36.  
    37.    err = ovs_netdev_init();
    38.    if (err)
    39.       goto error_unreg_notifier;
    40.  
    41.    err = dp_register_genl();
    42.    if (err < 0)
    43.       goto error_unreg_netdev;
    44.  
    45.    return 0;
    46.  
    47. error_unreg_netdev:
    48.    ovs_netdev_exit();
    49. error_unreg_notifier:
    50.    unregister_netdevice_notifier(&ovs_dp_device_notifier);
    51. error_netns_exit:
    52.    unregister_pernet_device(&ovs_net_ops);
    53. error_vport_exit:
    54.    ovs_vport_exit();
    55. error_flow_exit:
    56.    ovs_flow_exit();
    57. error_unreg_rtnl_link:
    58.    ovs_internal_dev_rtnl_link_unregister();
    59. error_action_fifos_exit:
    60.    action_fifos_exit();
    61. error_compat_exit:
    62.    compat_exit();
    63. error:
    64.    return err;
    65. }

     

    其中比较重要的是调用了dp_register_genl()，这个就是注册netlink函数，从而ovs-vswitchd可以通过netlink调用内核。

     

    1. static int dp_register_genl(void)
    2. {
    3.    int err;
    4.    int i;
    5.  
    6.    for (i = 0; i < ARRAY_SIZE(dp_genl_families); i++) {
    7.  
    8.       err = genl_register_family(dp_genl_families[i]);
    9.       if (err)
    10.          goto error;
    11.    }
    12.  
    13.    return 0;
    14.  
    15. error:
    16.    dp_unregister_genl(i);
    17.    return err;
    18. }

     

    这里dp_genl_families由四个netlink的family组成

     

    1. static struct genl_family *dp_genl_families[] = {
    2.    &dp_datapath_genl_family,
    3.    &dp_vport_genl_family,
    4.    &dp_flow_genl_family,
    5.    &dp_packet_genl_family,
    6. };

     

    其中分别定义了以下的操作：

     

    Family名称

    .name

    .ops

    dp_datapath_genl_family

    1. static struct genl_family dp_datapath_genl_family = {
    2.    .id = GENL_ID_GENERATE,
    3.    .hdrsize = sizeof(struct ovs_header),
    4.    .name = OVS_DATAPATH_FAMILY,
    5.    .version = OVS_DATAPATH_VERSION,
    6.    .maxattr = OVS_DP_ATTR_MAX,
    7.    .netnsok = true,
    8.    .parallel_ops = true,
    9.    .ops = dp_datapath_genl_ops,
    10.    .n_ops = ARRAY_SIZE(dp_datapath_genl_ops),
    11.    .mcgrps = &ovs_dp_datapath_multicast_group,
    12.    .n_mcgrps = 1,
    13. };
    1. static struct genl_ops dp_datapath_genl_ops[] = {
    2.    { .cmd = OVS_DP_CMD_NEW,
    3.      .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
    4.      .policy = datapath_policy,
    5.      .doit = ovs_dp_cmd_new
    6.    },
    7.    { .cmd = OVS_DP_CMD_DEL,
    8.      .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
    9.      .policy = datapath_policy,
    10.      .doit = ovs_dp_cmd_del
    11.    },
    12.    { .cmd = OVS_DP_CMD_GET,
    13.      .flags = 0, /* OK for unprivileged users. */
    14.      .policy = datapath_policy,
    15.      .doit = ovs_dp_cmd_get,
    16.      .dumpit = ovs_dp_cmd_dump
    17.    },
    18.    { .cmd = OVS_DP_CMD_SET,
    19.      .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
    20.      .policy = datapath_policy,
    21.      .doit = ovs_dp_cmd_set,
    22.    },
    23. };

    dp_vport_genl_family

    1. struct genl_family dp_vport_genl_family = {
    2.    .id = GENL_ID_GENERATE,
    3.    .hdrsize = sizeof(struct ovs_header),
    4.    .name = OVS_VPORT_FAMILY,
    5.    .version = OVS_VPORT_VERSION,
    6.    .maxattr = OVS_VPORT_ATTR_MAX,
    7.    .netnsok = true,
    8.    .parallel_ops = true,
    9.    .ops = dp_vport_genl_ops,
    10.    .n_ops = ARRAY_SIZE(dp_vport_genl_ops),
    11.    .mcgrps = &ovs_dp_vport_multicast_group,
    12.    .n_mcgrps = 1,
    13. };
    1. static struct genl_ops dp_vport_genl_ops[] = {
    2.    { .cmd = OVS_VPORT_CMD_NEW,
    3.      .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
    4.      .policy = vport_policy,
    5.      .doit = ovs_vport_cmd_new
    6.    },
    7.    { .cmd = OVS_VPORT_CMD_DEL,
    8.      .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
    9.      .policy = vport_policy,
    10.      .doit = ovs_vport_cmd_del
    11.    },
    12.    { .cmd = OVS_VPORT_CMD_GET,
    13.      .flags = 0, /* OK for unprivileged users. */
    14.      .policy = vport_policy,
    15.      .doit = ovs_vport_cmd_get,
    16.      .dumpit = ovs_vport_cmd_dump
    17.    },
    18.    { .cmd = OVS_VPORT_CMD_SET,
    19.      .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
    20.      .policy = vport_policy,
    21.      .doit = ovs_vport_cmd_set,
    22.    },
    23. };

    dp_flow_genl_family

    1. static struct genl_family dp_flow_genl_family = {
    2.    .id = GENL_ID_GENERATE,
    3.    .hdrsize = sizeof(struct ovs_header),
    4.    .name = OVS_FLOW_FAMILY,
    5.    .version = OVS_FLOW_VERSION,
    6.    .maxattr = OVS_FLOW_ATTR_MAX,
    7.    .netnsok = true,
    8.    .parallel_ops = true,
    9.    .ops = dp_flow_genl_ops,
    10.    .n_ops = ARRAY_SIZE(dp_flow_genl_ops),
    11.    .mcgrps = &ovs_dp_flow_multicast_group,
    12.    .n_mcgrps = 1,
    13. };
    1. static struct genl_ops dp_flow_genl_ops[] = {
    2.    { .cmd = OVS_FLOW_CMD_NEW,
    3.      .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
    4.      .policy = flow_policy,
    5.      .doit = ovs_flow_cmd_new
    6.    },
    7.    { .cmd = OVS_FLOW_CMD_DEL,
    8.      .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
    9.      .policy = flow_policy,
    10.      .doit = ovs_flow_cmd_del
    11.    },
    12.    { .cmd = OVS_FLOW_CMD_GET,
    13.      .flags = 0, /* OK for unprivileged users. */
    14.      .policy = flow_policy,
    15.      .doit = ovs_flow_cmd_get,
    16.      .dumpit = ovs_flow_cmd_dump
    17.    },
    18.    { .cmd = OVS_FLOW_CMD_SET,
    19.      .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
    20.      .policy = flow_policy,
    21.      .doit = ovs_flow_cmd_set,
    22.    },
    23. };

    dp_packet_genl_family

    1. static struct genl_family dp_packet_genl_family = {
    2.    .id = GENL_ID_GENERATE,
    3.    .hdrsize = sizeof(struct ovs_header),
    4.    .name = OVS_PACKET_FAMILY,
    5.    .version = OVS_PACKET_VERSION,
    6.    .maxattr = OVS_PACKET_ATTR_MAX,
    7.    .netnsok = true,
    8.    .parallel_ops = true,
    9.    .ops = dp_packet_genl_ops,
    10.    .n_ops = ARRAY_SIZE(dp_packet_genl_ops),
    11. };
    1. static struct genl_ops dp_packet_genl_ops[] = {
    2.    { .cmd = OVS_PACKET_CMD_EXECUTE,
    3.      .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
    4.      .policy = packet_policy,
    5.      .doit = ovs_packet_cmd_execute
    6.    }
    7. };

     

    如上一节中，ovs-vswitchd启动的时候，将虚拟网卡添加到虚拟交换机上的时候，会调用netlink的OVS_VPORT_CMD_NEW命令，因而会调用函数ovs_vport_cmd_new。

    会调用static struct vport *new_vport(const struct vport_parms *parms)

    会调用struct vport *ovs_vport_add(const struct vport_parms *parms)里面会调用vport = ops->create(parms);

    ops是什么呢？在dp_init函数中会调用ovs_netdev_init，它会调用ovs_vport_ops_register(&ovs_netdev_vport_ops);

    1. static struct vport_ops ovs_netdev_vport_ops = {
    2.    .type = OVS_VPORT_TYPE_NETDEV,
    3.    .create = netdev_create,
    4.    .destroy = netdev_destroy,
    5.    .send = dev_queue_xmit,
    6. };

     

    所以ops->create会调用netdev_create，它会调用ovs_netdev_link，其中有下面的代码：

    1. err = netdev_rx_handler_register(vport->dev, netdev_frame_hook,
    2.                 vport);

     

    注册一个方法叫做netdev_frame_hook，每当网卡收到包的时候，就调用这个方法。

     

    在下面的章节中，我们会从这个函数开始，解析整个网络包的处理过程。

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  • 原文地址：https://www.cnblogs.com/popsuper1982/p/5868772.html
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