I am creating socket as follows:

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static void create_new_read_socket( const uint64_t card_pos )
{
     const int read_sock = available_cards[card_pos].read_socket = socket( PF_PACKET, SOCK_RAW|SOCK_NONBLOCK, htons( ETH_P_ALL ) );
       
     if( read_sock < 0 ) 
     {
          fprintf( stderr, "%s %d Unable to create read_sock", __func__, __LINE__ );
          return;
     }
         
     struct ifreq ifr;
     strncpy( ifr.ifr_name, available_cards[card_pos].card_name, IFNAMSIZ );
     if( ioctl( read_sock, SIOCGIFFLAGS, &ifr ) == -1 )
     {
          fprintf( stderr, "%s %d Unable to get flag", __func__, __LINE__ );
          return;
     }
     available_cards[card_pos].ifr_flags_backup = ifr.ifr_flags;
     ifr.ifr_flags |= ( IFF_PROMISC | IFF_UP );
     if( ioctl( read_sock, SIOCSIFFLAGS, &ifr ) == -1 )
     {
          fprintf( stderr, "%s %d Unable to set promiscious flag", __func__, __LINE__ );
          return;
     }

     struct sockaddr_ll ll =
     {   
          .sll_family = PF_PACKET,
          .sll_protocol = htons(ETH_P_ALL),
          .sll_ifindex = (int)available_cards[card_pos].index
     };            
     if( bind( read_sock, (struct sockaddr *) &ll, sizeof(ll) ) < 0 ) 
     {
          fprintf( stderr, "%s %d Unable to bind", __func__, __LINE__ );
          return;
     }
     const int one = 1;         
     if( setsockopt( read_sock, SOL_PACKET, PACKET_AUXDATA, &one, sizeof(one)) < 0 ) 
     {        
          fprintf( stderr, "%s %d Unable to setsockopt PACKET_AUXDATA", __func__, __LINE__ );
          return;
     }        
}

=============================

reading the packet as follows:

=============================

read_return = recvmsg( read_socket, &msg, MSG_DONTWAIT );

=============================

I am seeing recvmsg is returning buffer filled with zeros but returning size is accurate.