struct packet_mreq {
                  int            mr_ifindex;    /* interface index */
                  unsigned short mr_type;       /* action */
                  unsigned short mr_alen;       /* address length */
                  unsigned char  mr_address[8]; /* physical-layer address */
              };

          mr_ifindex contains the interface index for the interface
          whose status should be changed.  The mr_type field specifies
          which action to perform.  PACKET_MR_PROMISC enables receiving
          all packets on a shared medium (often known as "promiscuous
          mode"), PACKET_MR_MULTICAST binds the socket to the physical-
          layer multicast group specified in mr_address and mr_alen, and
          PACKET_MR_ALLMULTI sets the socket up to receive all multicast
          packets arriving at the interface.

          In addition, the traditional ioctls SIOCSIFFLAGS, SIOCADD‐
          MULTI, SIOCDELMULTI can be used for the same purpose.

              struct tpacket_auxdata {
                  __u32 tp_status;
                  __u32 tp_len;      /* packet length */
                  __u32 tp_snaplen;  /* captured length */
                  __u16 tp_mac;
                  __u16 tp_net;
                  __u16 tp_vlan_tci;
                  __u16 tp_vlan_tpid; /* Since Linux 3.14; earlier, these
                                         were unused padding bytes */
              };