Алгоритмы защиты ARP

[redrumage]

Algorithm 1 update arp cache

1: if DHCP packet is received then

2: if message type is DHCPACK then

3: IP ← ‘your IP address’ field value

4: if IP != server’s IP then

5: MAC ← ‘client’s hardware address’ field value

6: Add (IP, MAC) to server’s ARP cache

7: Add (IP, MAC) to backup file

8: end if

9: else if message type is DHCPRELEASE then

10: IP ← ‘your IP address’ field value

11: if IP != server’s IP then

12: Remove (IP, ?) from server’s ARP cache

13: Remove (IP, ?) from backup file

14: end if

15: else if message type is DHCPDECLINE then

16: IP ← ‘requested IP address’ options field value

17: if IP != server’s IP then

18: Remove (IP, ?) from server’s ARP cache

19: Remove (IP, ?) from backup file

20: end if

21: else

22: NOOP

23: end if

24:end if

Algorithm 2 send arp reply

1: if ARP message is received then

2: if operation field = REQUEST then

3: TPA ← Target Protocol Address field value

4: Create an ARP REPLY message

5: Sender Protocol Address field ← TPA

6: if TPA = server’s IP address then

7: SHA ← server’s MAC address

8: else

9: Find (TPA, MAC) mapping in ARP cache

10: if (TPA, MAC) does not exist then

11: return //No response is sent

12: end if

13: SHA ← MAC address in (TPA, MAC)

14: end if

15: Sender Hardware Address field ← SHA

16: Send ARP response to requesting host

17: end if

18:end if

Источник