flow_mask_hash_fields(const struct flow *flow, struct flow_wildcards *wc,
                      enum nx_hash_fields fields)
{
    int i;
    switch (fields) {
    case NX_HASH_FIELDS_ETH_SRC:
        memset(&wc->masks.dl_src, 0xff, sizeof wc->masks.dl_src);
        break;

    case NX_HASH_FIELDS_SYMMETRIC_L4:
        memset(&wc->masks.dl_src, 0xff, sizeof wc->masks.dl_src);
        memset(&wc->masks.dl_dst, 0xff, sizeof wc->masks.dl_dst);
        if (flow->dl_type == htons(ETH_TYPE_IP)) {
            memset(&wc->masks.nw_src, 0xff, sizeof wc->masks.nw_src);
            memset(&wc->masks.nw_dst, 0xff, sizeof wc->masks.nw_dst);
        } else if (flow->dl_type == htons(ETH_TYPE_IPV6)) {
            memset(&wc->masks.ipv6_src, 0xff, sizeof wc->masks.ipv6_src);
            memset(&wc->masks.ipv6_dst, 0xff, sizeof wc->masks.ipv6_dst);
        }
        if (is_ip_any(flow)) {
            memset(&wc->masks.nw_proto, 0xff, sizeof wc->masks.nw_proto);
            /* Unwildcard port only for non-UDP packets as udp port
             * numbers are not used in hash calculations.
             */
            if (flow->nw_proto != IPPROTO_UDP) {
                flow_unwildcard_tp_ports(flow, wc);
            }
        }
        for (i = 0; i < FLOW_MAX_VLAN_HEADERS; i++) {
            wc->masks.vlans[i].tci |= htons(VLAN_VID_MASK | VLAN_CFI);
        }
        break;
    case NX_HASH_FIELDS_SYMMETRIC_L3L4_UDP:
        if (is_ip_any(flow) && flow->nw_proto == IPPROTO_UDP
            && !(flow->nw_frag & FLOW_NW_FRAG_MASK)) {
            memset(&wc->masks.tp_src, 0xff, sizeof wc->masks.tp_src);
            memset(&wc->masks.tp_dst, 0xff, sizeof wc->masks.tp_dst);
        }
        /* fall through */
    case NX_HASH_FIELDS_SYMMETRIC_L3L4:
        if (flow->dl_type == htons(ETH_TYPE_IP)) {
            memset(&wc->masks.nw_src, 0xff, sizeof wc->masks.nw_src);
            memset(&wc->masks.nw_dst, 0xff, sizeof wc->masks.nw_dst);
        } else if (flow->dl_type == htons(ETH_TYPE_IPV6)) {
            memset(&wc->masks.ipv6_src, 0xff, sizeof wc->masks.ipv6_src);
            memset(&wc->masks.ipv6_dst, 0xff, sizeof wc->masks.ipv6_dst);
        } else {
            break; /* non-IP flow */
        }
        memset(&wc->masks.nw_proto, 0xff, sizeof wc->masks.nw_proto);
        if ((flow->nw_proto == IPPROTO_TCP || flow->nw_proto == IPPROTO_SCTP)
             && !(flow->nw_frag & FLOW_NW_FRAG_MASK)) {
            memset(&wc->masks.tp_src, 0xff, sizeof wc->masks.tp_src);
            memset(&wc->masks.tp_dst, 0xff, sizeof wc->masks.tp_dst);
        }
        break;

    case NX_HASH_FIELDS_NW_SRC:
        if (flow->dl_type == htons(ETH_TYPE_IP)) {
            memset(&wc->masks.nw_src, 0xff, sizeof wc->masks.nw_src);
        } else if (flow->dl_type == htons(ETH_TYPE_IPV6)) {
            memset(&wc->masks.ipv6_src, 0xff, sizeof wc->masks.ipv6_src);
        }
        break;

    case NX_HASH_FIELDS_NW_DST:
        if (flow->dl_type == htons(ETH_TYPE_IP)) {
            memset(&wc->masks.nw_dst, 0xff, sizeof wc->masks.nw_dst);
        } else if (flow->dl_type == htons(ETH_TYPE_IPV6)) {
            memset(&wc->masks.ipv6_dst, 0xff, sizeof wc->masks.ipv6_dst);
        }
        break;

    case NX_HASH_FIELDS_SYMMETRIC_L3:
        if (flow->dl_type == htons(ETH_TYPE_IP)) {
            memset(&wc->masks.nw_src, 0xff, sizeof wc->masks.nw_src);
            memset(&wc->masks.nw_dst, 0xff, sizeof wc->masks.nw_dst);
        } else if (flow->dl_type == htons(ETH_TYPE_IPV6)) {
            memset(&wc->masks.ipv6_src, 0xff, sizeof wc->masks.ipv6_src);
            memset(&wc->masks.ipv6_dst, 0xff, sizeof wc->masks.ipv6_dst);
        }
        break;

    default:
        OVS_NOT_REACHED();
    }
}