DoS, ICMP, proxies, SYNDefender

Thu Oct 3 22:26:06 UTC 1996

>From: Tim Bass <bass at linux.silkroad.com>
>
>>    Tim, unfortunately ICMP UNREACHABLE can be sent some intermediate
>> router during routing flip process. For this reason some customer
>> prefer cut off this sort of ICMP - it would break running TCP connection.
>
>Understood, however the conditions to terminate the connection
>is not just as simple as UNREACHABLE.  A few possible conditions:
>(1) UNREACHABLE && TCP_SYN_STATE
>(2) UNREACHABLE && TCP_SYN_STATE && sk->time_in_state

    I am not shure that it is in _ALL_ host types.
Experience gave me that some time I had problem with uninterraptable
service up to I configure router to cut off ICMP UNREACHABLE from
outside.

				- Leonid Yegoshin, LY22