【OVS2.5源码解读】datapath的netlink机制

ovs datapath是通过netlink与用户态进行通信的，实现dp、端口、流表、packet的操作。 netlink的注册是在datapath模块的初始化函数中实现的。

1、dp_init函数

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();   //注册netlink处理函数      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;  }  

2、genl_register_family函数

#define genl_register_family rpl_genl_register_family  static inline int rpl_genl_register_family(struct genl_family *family)  {      family->module = THIS_MODULE;      return rpl___genl_register_family(family);        //注册netlink  }  

3、rpl___genl_register_family函数

int rpl___genl_register_family(struct rpl_genl_family *f)  {      int err;      f->compat_family.id = f->id;      f->compat_family.hdrsize = f->hdrsize;      strncpy(f->compat_family.name, f->name, GENL_NAMSIZ);      f->compat_family.version = f->version;      f->compat_family.maxattr = f->maxattr;      f->compat_family.netnsok = f->netnsok;  #ifdef HAVE_PARALLEL_OPS      f->compat_family.parallel_ops = f->parallel_ops;  #endif      err = genl_register_family_with_ops(&f->compat_family,       //调用系统接口，可以不用关注消息处理，可以把ops作为netlink的处理入口函数                          (struct genl_ops *) f->ops, f->n_ops);      if (err)          goto error;      if (f->mcgrps) {          /* Need to Fix GROUP_ID() for more than one group. */          BUG_ON(f->n_mcgrps > 1);          err = genl_register_mc_group(&f->compat_family,      //调用系统接口，暂时只看到dp中用ovs_notify中在使用                           (struct genl_multicast_group *) f->mcgrps);          if (err)              goto error;      }  error:      return err;  }  

netlink的操作是由dp_genl_families定义的，一共有4类。

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

1、datapath netlink定义：

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      /*创建datapath*/    },      { .cmd = OVS_DP_CMD_DEL,        .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */        .policy = datapath_policy,        .doit = ovs_dp_cmd_del     /*删除datapath*/     },      { .cmd = OVS_DP_CMD_GET,        .flags = 0,           /* OK for unprivileged users. */        .policy = datapath_policy,        .doit = ovs_dp_cmd_get,        .dumpit = ovs_dp_cmd_dump   /*导出datapath*/     },      { .cmd = OVS_DP_CMD_SET,        .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */        .policy = datapath_policy,        .doit = ovs_dp_cmd_set,     /*修改datapath*/    },  };  

2、vport netlink定义：

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 /*创建vport*/      },      { .cmd = OVS_VPORT_CMD_DEL,        .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */        .policy = vport_policy,        .doit = ovs_vport_cmd_del /*删除vport*/      },      { .cmd = OVS_VPORT_CMD_GET,        .flags = 0,           /* OK for unprivileged users. */        .policy = vport_policy,        .doit = ovs_vport_cmd_get,        .dumpit = ovs_vport_cmd_dump  /*导出vport*/     },      { .cmd = OVS_VPORT_CMD_SET,        .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */        .policy = vport_policy,        .doit = ovs_vport_cmd_set,    /*修改vport*/      },  };  

3、精确流表 netlink定义：

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,  /* datapath流表更新的入口函数 */    .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  /*添加精确流表 */    },      { .cmd = OVS_FLOW_CMD_DEL,        .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */        .policy = flow_policy,        .doit = ovs_flow_cmd_del  /*删除精确流表*/    },      { .cmd = OVS_FLOW_CMD_GET,        .flags = 0,           /* OK for unprivileged users. */        .policy = flow_policy,        .doit = ovs_flow_cmd_get,        .dumpit = ovs_flow_cmd_dump   /*导出精确流表*/      },      { .cmd = OVS_FLOW_CMD_SET,        .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */        .policy = flow_policy,        .doit = ovs_flow_cmd_set, /*修改精确流表*/      },  };  

4、packet netlink定义：

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    /*执行报文action操作*/      }  };  

upcall线程与netlink

假设upcall handler线程有两个，vport有四个，那么每个vport下都将持有两个NetLink连接的信息，这两个NetLink连接将被用来上送upcall消息。
每个NetLink连接被对应的upcall handler线程接管，多个vport在同一线程中的NetLink连接被epoll管理。

1：每个vport下都挂多个NetLink连接，数量等同于upcall处理线程的数量
2：线程中routine函数为udpif_upcall_handler，伪码如下：

routine {     while(线程不设自杀标记) {          if(从epoll中收到了一些upcall消息，则进一步处理upcall) {               continue;           } else {               注册poll：当epoll_fd有骚动时解除当前线程的block          }          block当前线程     }}

3：每个NetLink连接被称为一个upcall channel