五 OVS--流表创建

dp_register_genl初始化了流表的操作，流表创建的入口函数是ovs_flow_cmd_new

/**
 * struct genl_info - receiving information
 * @snd_seq: sending sequence number
 * @snd_portid: netlink portid of sender
 * @nlhdr: netlink message header
 * @genlhdr: generic netlink message header
 * @userhdr: user specific header
 * @attrs: netlink attributes
 * @_net: network namespace
 * @user_ptr: user pointers
 */
struct genl_info {
    u32         snd_seq;
    u32         snd_portid;
    struct nlmsghdr *   nlhdr;
    struct genlmsghdr * genlhdr;
    void *          userhdr;
    struct nlattr **    attrs;
    possible_net_t      _net;
    void *          user_ptr[2];
};

 

static int ovs_flow_cmd_new(struct sk_buff *skb, struct genl_info *info)
{
    struct net *net = sock_net(skb->sk);
    struct nlattr **a = info->attrs;
    struct ovs_header *ovs_header = info->userhdr;
    struct sw_flow *flow = NULL, *new_flow;
    struct sw_flow_mask mask;
    struct sk_buff *reply;
    struct datapath *dp; 
    struct sw_flow_key key; 
    struct sw_flow_actions *acts;
    struct sw_flow_match match;
    u32 ufid_flags = ovs_nla_get_ufid_flags(a[OVS_FLOW_ATTR_UFID_FLAGS]);
    int error;
    bool log = !a[OVS_FLOW_ATTR_PROBE];

    /* Must have key and actions. */
    error = -EINVAL;
    if (!a[OVS_FLOW_ATTR_KEY]) {
        OVS_NLERR(log, "Flow key attr not present in new flow.");
        goto error;
    }    
    if (!a[OVS_FLOW_ATTR_ACTIONS]) {
        OVS_NLERR(log, "Flow actions attr not present in new flow.");
        goto error;
    }    

    /* Most of the time we need to allocate a new flow, do it before
     * locking.
     */
    new_flow = ovs_flow_alloc();
    if (IS_ERR(new_flow)) {
        error = PTR_ERR(new_flow);
        goto error;
    }    

    /* Extract key. */
    ovs_match_init(&match, &key, &mask);
    error = ovs_nla_get_match(net, &match, a[OVS_FLOW_ATTR_KEY],
                  a[OVS_FLOW_ATTR_MASK], log);
    if (error)
        goto err_kfree_flow;

    ovs_flow_mask_key(&new_flow->key, &key, true, &mask);

    /* Extract flow identifier. */
    error = ovs_nla_get_identifier(&new_flow->id, a[OVS_FLOW_ATTR_UFID],
                       &key, log);
    if (error)
        goto err_kfree_flow;

    /* Validate actions. */
    error = ovs_nla_copy_actions(net, a[OVS_FLOW_ATTR_ACTIONS],
                     &new_flow->key, &acts, log);
    if (error) {
        OVS_NLERR(log, "Flow actions may not be safe on all matching packets.");
        goto err_kfree_flow;
    }

    reply = ovs_flow_cmd_alloc_info(acts, &new_flow->id, info, false,
                    ufid_flags);
    if (IS_ERR(reply)) {
        error = PTR_ERR(reply);
        goto err_kfree_acts;
    }

    ovs_lock();
    dp = get_dp(net, ovs_header->dp_ifindex);
    if (unlikely(!dp)) {
        error = -ENODEV;
        goto err_unlock_ovs;
    }

    /* Check if this is a duplicate flow */
    if (ovs_identifier_is_ufid(&new_flow->id))
        flow = ovs_flow_tbl_lookup_ufid(&dp->table, &new_flow->id);
    if (!flow)
        flow = ovs_flow_tbl_lookup(&dp->table, &key);
    if (likely(!flow)) {
        rcu_assign_pointer(new_flow->sf_acts, acts);

        /* Put flow in bucket. */
        error = ovs_flow_tbl_insert(&dp->table, new_flow, &mask);
        if (unlikely(error)) {
            acts = NULL;
            goto err_unlock_ovs;
        }

        if (unlikely(reply)) {
            error = ovs_flow_cmd_fill_info(new_flow,
                               ovs_header->dp_ifindex,
                               reply, info->snd_portid,
                               info->snd_seq, 0,
                               OVS_FLOW_CMD_NEW,
                               ufid_flags);
            BUG_ON(error < 0);
        }
        ovs_unlock();
    } else {
        struct sw_flow_actions *old_acts;

        /* Bail out if we're not allowed to modify an existing flow.
         * We accept NLM_F_CREATE in place of the intended NLM_F_EXCL
         * because Generic Netlink treats the latter as a dump
         * request.  We also accept NLM_F_EXCL in case that bug ever
         * gets fixed.
         */
        if (unlikely(info->nlhdr->nlmsg_flags & (NLM_F_CREATE
                             | NLM_F_EXCL))) {
            error = -EEXIST;
            goto err_unlock_ovs;
        }
        /* The flow identifier has to be the same for flow updates.
         * Look for any overlapping flow.
         */
        if (unlikely(!ovs_flow_cmp(flow, &match))) {
            if (ovs_identifier_is_key(&flow->id))
                flow = ovs_flow_tbl_lookup_exact(&dp->table,
                                 &match);
            else /* UFID matches but key is different */
                flow = NULL;
            if (!flow) {
                error = -ENOENT;
                goto err_unlock_ovs;
            }
        }
        /* Update actions. */
        old_acts = ovsl_dereference(flow->sf_acts);
        rcu_assign_pointer(flow->sf_acts, acts);

        if (unlikely(reply)) {
            error = ovs_flow_cmd_fill_info(flow,
                               ovs_header->dp_ifindex,
                               reply, info->snd_portid,
                               info->snd_seq, 0,
                               OVS_FLOW_CMD_NEW,
                               ufid_flags);
            BUG_ON(error < 0);
        }
        ovs_unlock();

        ovs_nla_free_flow_actions_rcu(old_acts);
        ovs_flow_free(new_flow, false);
    }

    if (reply)
        ovs_notify(&dp_flow_genl_family, &ovs_dp_flow_multicast_group, reply, info);
    return 0;

err_unlock_ovs:
    ovs_unlock();
    kfree_skb(reply);
err_kfree_acts:
    ovs_nla_free_flow_actions(acts);
err_kfree_flow:
    ovs_flow_free(new_flow, false);
error:
    return error;
}