flow_push_mpls(struct flow *flow, int n, ovs_be16 mpls_eth_type,
               struct flow_wildcards *wc, bool clear_flow_L3)
{
    ovs_assert(eth_type_mpls(mpls_eth_type));
    ovs_assert(n < FLOW_MAX_MPLS_LABELS);

    if (n) {
        int i;

        if (wc) {
            memset(&wc->masks.mpls_lse, 0xff, sizeof *wc->masks.mpls_lse * n);
        }
        for (i = n; i >= 1; i--) {
            flow->mpls_lse[i] = flow->mpls_lse[i - 1];
        }
        flow->mpls_lse[0] = (flow->mpls_lse[1] & htonl(~MPLS_BOS_MASK));
    } else {
        int label = 0;          /* IPv4 Explicit Null. */
        int tc = 0;
        int ttl = 64;

        if (flow->dl_type == htons(ETH_TYPE_IPV6)) {
            label = 2;
        }

        if (is_ip_any(flow)) {
            tc = (flow->nw_tos & IP_DSCP_MASK) >> 2;
            if (wc) {
                wc->masks.nw_tos |= IP_DSCP_MASK;
                wc->masks.nw_ttl = 0xff;
            }

            if (flow->nw_ttl) {
                ttl = flow->nw_ttl;
            }
        }

        flow->mpls_lse[0] = set_mpls_lse_values(ttl, tc, 1, htonl(label));

        if (clear_flow_L3) {
            /* Clear all L3 and L4 fields and dp_hash. */
            BUILD_ASSERT(FLOW_WC_SEQ == 42);
            memset((char *) flow + FLOW_SEGMENT_2_ENDS_AT, 0,
                   sizeof(struct flow) - FLOW_SEGMENT_2_ENDS_AT);
            flow->dp_hash = 0;
        }
    }
    flow->dl_type = mpls_eth_type;
}
flow_push_mpls(struct flow *flow, int n, ovs_be16 mpls_eth_type,
               struct flow_wildcards *wc, bool clear_flow_L3)
{
    ovs_assert(eth_type_mpls(mpls_eth_type));
    ovs_assert(n < FLOW_MAX_MPLS_LABELS);

    if (n) {
        int i;

        if (wc) {
            memset(&wc->masks.mpls_lse, 0xff, sizeof *wc->masks.mpls_lse * n);
        }
        for (i = n; i >= 1; i--) {
            flow->mpls_lse[i] = flow->mpls_lse[i - 1];
        }
        flow->mpls_lse[0] = (flow->mpls_lse[1] & htonl(~MPLS_BOS_MASK));
    } else {
        int label = 0;           
        int tc = 0;
        int ttl = 64;

        if (flow->dl_type == htons(ETH_TYPE_IPV6)) {
            label = 2;
        }

        if (is_ip_any(flow)) {
            tc = (flow->nw_tos & IP_DSCP_MASK) >> 2;
            if (wc) {
                wc->masks.nw_tos |= IP_DSCP_MASK;
                wc->masks.nw_ttl = 0xff;
            }

            if (flow->nw_ttl) {
                ttl = flow->nw_ttl;
            }
        }

        flow->mpls_lse[0] = set_mpls_lse_values(ttl, tc, 1, htonl(label));

        if (clear_flow_L3) {
             
            BUILD_ASSERT(FLOW_WC_SEQ == 42);
            memset((char *) flow + FLOW_SEGMENT_2_ENDS_AT, 0,
                   sizeof(struct flow) - FLOW_SEGMENT_2_ENDS_AT);
            flow->dp_hash = 0;
        }
    }
    flow->dl_type = mpls_eth_type;
}