【OVS2.5.0源码分析】sFlow实现分析（3）

本篇分析，sflow的消息处理，处理入口函数是在process_upcall函数。

1、process_upcall函数

    case SFLOW_UPCALL:
        if (upcall->sflow) {
            union user_action_cookie cookie;
            const struct nlattr *actions;
            size_t actions_len = 0;
            struct dpif_sflow_actions sflow_actions;
            memset(&sflow_actions, 0, sizeof sflow_actions);
            memset(&cookie, 0, sizeof cookie);
            memcpy(&cookie, nl_attr_get(userdata), sizeof cookie.sflow);	//读取user data信息
            if (upcall->actions) {
                /* Actions were passed up from datapath. */
                actions = nl_attr_get(upcall->actions);
                actions_len = nl_attr_get_size(upcall->actions);
                if (actions && actions_len) {
                    dpif_sflow_read_actions(flow, actions, actions_len,		//获取sflow action
                                            &sflow_actions);
                }
            }
            if (actions_len == 0) {
                /* Lookup actions in userspace cache. */
                struct udpif_key *ukey = ukey_lookup(udpif, upcall->ufid);	//用户态cache，加速
                if (ukey) {
                    ukey_get_actions(ukey, &actions, &actions_len);
                    dpif_sflow_read_actions(flow, actions, actions_len,
                                            &sflow_actions);
                }
            }
            dpif_sflow_received(upcall->sflow, packet, flow,			//sflow消息处理
                                flow->in_port.odp_port, &cookie,
                                actions_len > 0 ? &sflow_actions : NULL);
        }
        break;

2、dpif_sflow_received函数

void
dpif_sflow_received(struct dpif_sflow *ds, const struct dp_packet *packet,
		    const struct flow *flow, odp_port_t odp_in_port,
		    const union user_action_cookie *cookie,
		    const struct dpif_sflow_actions *sflow_actions)
    OVS_EXCLUDED(mutex)
{
    SFL_FLOW_SAMPLE_TYPE fs;
    SFLFlow_sample_element hdrElem;
    SFLSampled_header *header;
    SFLFlow_sample_element switchElem;
    uint8_t tnlInProto, tnlOutProto;
    SFLFlow_sample_element tnlInElem, tnlOutElem;
    SFLFlow_sample_element vniInElem, vniOutElem;
    SFLFlow_sample_element mplsElem;
    uint32_t mpls_lse_buf[FLOW_MAX_MPLS_LABELS];
    SFLSampler *sampler;
    struct dpif_sflow_port *in_dsp;
    struct dpif_sflow_port *out_dsp;
    ovs_be16 vlan_tci;

    ovs_mutex_lock(&mutex);
    sampler = ds->sflow_agent->samplers;	//获取第一个sampler
    if (!sampler) {
        goto out;
    }

    /* Build a flow sample. */
    memset(&fs, 0, sizeof fs);

    /* Look up the input ifIndex if this port has one. Otherwise just
     * leave it as 0 (meaning 'unknown') and continue. */
    in_dsp = dpif_sflow_find_port(ds, odp_in_port);
    if (in_dsp) {
        fs.input = SFL_DS_INDEX(in_dsp->dsi);
    }

    /* Make the assumption that the random number generator in the datapath converges
     * to the configured mean, and just increment the samplePool by the configured
     * sampling rate every time. */
    sampler->samplePool += sfl_sampler_get_sFlowFsPacketSamplingRate(sampler);

    /* Sampled header. */
    memset(&hdrElem, 0, sizeof hdrElem);
    hdrElem.tag = SFLFLOW_HEADER;
    header = &hdrElem.flowType.header;
    header->header_protocol = SFLH