Issue

• The /proc/net/ptype file shows a current list of ethertypes recognized by the kernel. If dhclient or some other program is using an AF_PACKET socket, you can be aware of it by the ALL/packet_rcv entry in the output:

  [root@r74 ~]# cat /proc/net/ptype 
  Type Device      Function
  ALL  eth0     packet_rcv
  0800          ip_rcv
  0011          llc_rcv [llc]
  0004          llc_rcv [llc]
  0806          arp_rcv
  86dd          ipv6_rcv
  

• But after updating to RHEL 7.5, the entry is no longer present even though it can be confirmed that the program is still using the AF_PACKET socket:

  [root@r75 ~]# cat /proc/net/ptype 
  Type Device      Function
  0800          ip_rcv
  0011          llc_rcv [llc]
  0004          llc_rcv [llc]
  0806          arp_rcv
  86dd          ipv6_rcv