Openvswitch原理与代码分析: openvswitch内核模块的加载

Posted 2022-08-31 liuhongru

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

 

static int __init dp_init(void)

   int err;
 
   BUILD_BUG_ON(sizeof(struct ovs_skb_cb) > FIELD_SIZEOF(struct sk_buff, cb));
 
   pr_info("Open vSwitch switching datapath %s\n", VERSION);
 
   err = compat_init();
   if (err)
      goto error;
 
   err = action_fifos_init();
   if (err)
      goto error_compat_exit;
 
   err = ovs_internal_dev_rtnl_link_register();
   if (err)
      goto error_action_fifos_exit;
 
   err = ovs_flow_init();
   if (err)
      goto error_unreg_rtnl_link;
 
   err = ovs_vport_init();
   if (err)
      goto error_flow_exit;
 
   err = register_pernet_device(&ovs_net_ops);
   if (err)
      goto error_vport_exit;
 
   err = register_netdevice_notifier(&ovs_dp_device_notifier);
   if (err)
      goto error_netns_exit;
 
   err = ovs_netdev_init();
   if (err)
      goto error_unreg_notifier;
 
   err = dp_register_genl();
   if (err < 0)
      goto error_unreg_netdev;
 
   return 0;
 
error_unreg_netdev:
   ovs_netdev_exit();
error_unreg_notifier:
   unregister_netdevice_notifier(&ovs_dp_device_notifier);
error_netns_exit:
   unregister_pernet_device(&ovs_net_ops);
error_vport_exit:
   ovs_vport_exit();
error_flow_exit:
   ovs_flow_exit();
error_unreg_rtnl_link:
   ovs_internal_dev_rtnl_link_unregister();
error_action_fifos_exit:
   action_fifos_exit();
error_compat_exit:
   compat_exit();
error:
   return err;

 

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。

 

static int dp_register_genl(void)

   int err;
   int i;
 
   for (i = 0; i < ARRAY_SIZE(dp_genl_families); i++)
 
      err = genl_register_family(dp_genl_families[i]);
      if (err)
         goto error;
   
 
   return 0;
 
error:
   dp_unregister_genl(i);
   return err;

 

这里dp_genl_families由四个netlink的family组成

 

static struct genl_family *dp_genl_families[] =
   &dp_datapath_genl_family,
   &dp_vport_genl_family,
   &dp_flow_genl_family,
   &dp_packet_genl_family,
;
 

其中分别定义了以下的操作：

 

Family名称

.name

.ops

dp_datapath_genl_family

static struct genl_family dp_datapath_genl_family =
   .id = GENL_ID_GENERATE,
   .hdrsize = sizeof(struct ovs_header),
   .name = OVS_DATAPATH_FAMILY,
   .version = OVS_DATAPATH_VERSION,
   .maxattr = OVS_DP_ATTR_MAX,
   .netnsok = true,
   .parallel_ops = true,
   .ops = dp_datapath_genl_ops,
   .n_ops = ARRAY_SIZE(dp_datapath_genl_ops),
   .mcgrps = &ovs_dp_datapath_multicast_group,
   .n_mcgrps = 1,
;
static struct genl_ops dp_datapath_genl_ops[] =
    .cmd = OVS_DP_CMD_NEW,
     .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
     .policy = datapath_policy,
     .doit = ovs_dp_cmd_new
   ,
    .cmd = OVS_DP_CMD_DEL,
     .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
     .policy = datapath_policy,
     .doit = ovs_dp_cmd_del
   ,
    .cmd = OVS_DP_CMD_GET,
     .flags = 0, /* OK for unprivileged users. */
     .policy = datapath_policy,
     .doit = ovs_dp_cmd_get,
     .dumpit = ovs_dp_cmd_dump
   ,
    .cmd = OVS_DP_CMD_SET,
     .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
     .policy = datapath_policy,
     .doit = ovs_dp_cmd_set,
   ,
;
dp_vport_genl_family

struct genl_family dp_vport_genl_family =
   .id = GENL_ID_GENERATE,
   .hdrsize = sizeof(struct ovs_header),
   .name = OVS_VPORT_FAMILY,
   .version = OVS_VPORT_VERSION,
   .maxattr = OVS_VPORT_ATTR_MAX,
   .netnsok = true,
   .parallel_ops = true,
   .ops = dp_vport_genl_ops,
   .n_ops = ARRAY_SIZE(dp_vport_genl_ops),
   .mcgrps = &ovs_dp_vport_multicast_group,
   .n_mcgrps = 1,
;
static struct genl_ops dp_vport_genl_ops[] =
    .cmd = OVS_VPORT_CMD_NEW,
     .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
     .policy = vport_policy,
     .doit = ovs_vport_cmd_new
   ,
    .cmd = OVS_VPORT_CMD_DEL,
     .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
     .policy = vport_policy,
     .doit = ovs_vport_cmd_del
   ,
    .cmd = OVS_VPORT_CMD_GET,
     .flags = 0, /* OK for unprivileged users. */
     .policy = vport_policy,
     .doit = ovs_vport_cmd_get,
     .dumpit = ovs_vport_cmd_dump
   ,
    .cmd = OVS_VPORT_CMD_SET,
     .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
     .policy = vport_policy,
     .doit = ovs_vport_cmd_set,
   ,
;
dp_flow_genl_family

static struct genl_family dp_flow_genl_family =
   .id = GENL_ID_GENERATE,
   .hdrsize = sizeof(struct ovs_header),
   .name = OVS_FLOW_FAMILY,
   .version = OVS_FLOW_VERSION,
   .maxattr = OVS_FLOW_ATTR_MAX,
   .netnsok = true,
   .parallel_ops = true,
   .ops = dp_flow_genl_ops,
   .n_ops = ARRAY_SIZE(dp_flow_genl_ops),
   .mcgrps = &ovs_dp_flow_multicast_group,
   .n_mcgrps = 1,
;
static struct genl_ops dp_flow_genl_ops[] =
    .cmd = OVS_FLOW_CMD_NEW,
     .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
     .policy = flow_policy,
     .doit = ovs_flow_cmd_new
   ,
    .cmd = OVS_FLOW_CMD_DEL,
     .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
     .policy = flow_policy,
     .doit = ovs_flow_cmd_del
   ,
    .cmd = OVS_FLOW_CMD_GET,
     .flags = 0, /* OK for unprivileged users. */
     .policy = flow_policy,
     .doit = ovs_flow_cmd_get,
     .dumpit = ovs_flow_cmd_dump
   ,
    .cmd = OVS_FLOW_CMD_SET,
     .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
     .policy = flow_policy,
     .doit = ovs_flow_cmd_set,
   ,
;
dp_packet_genl_family

static struct genl_family dp_packet_genl_family =
   .id = GENL_ID_GENERATE,
   .hdrsize = sizeof(struct ovs_header),
   .name = OVS_PACKET_FAMILY,
   .version = OVS_PACKET_VERSION,
   .maxattr = OVS_PACKET_ATTR_MAX,
   .netnsok = true,
   .parallel_ops = true,
   .ops = dp_packet_genl_ops,
   .n_ops = ARRAY_SIZE(dp_packet_genl_ops),
;
static struct genl_ops dp_packet_genl_ops[] =
    .cmd = OVS_PACKET_CMD_EXECUTE,
     .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
     .policy = packet_policy,
     .doit = ovs_packet_cmd_execute
   
;
 

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);

static struct vport_ops ovs_netdev_vport_ops =
   .type = OVS_VPORT_TYPE_NETDEV,
   .create = netdev_create,
   .destroy = netdev_destroy,
   .send = dev_queue_xmit,
;
 

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

err = netdev_rx_handler_register(vport->dev, netdev_frame_hook,
                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。