iptables and TOS 15

[Jason Opperisano]

On Fri, 2004-11-12 at 03:40, tepesu at australia.edu wrote:
>     hi,
> 
>  my ISP mark packets from some internet traffic with TOS 15 and i musst
> filter this traffic. how and where i must odified iptables to can do some
> filtering using this marks, TOS 15.

as far as i'm aware, "15" is not a valid TOS value.  as a result of the
way the TOS bits are set in the packet header, there are only 5 possible
TOS settings (from RFC 1349):

  1000   --   minimize delay
  0100   --   maximize throughput
  0010   --   maximize reliability
  0001   --   minimize monetary cost
  0000   --   normal service

some products configure these simply as values 1 - 5 (i.e. cisco boxes).
iptables allows you to use two different notations, decimal and hex:

  Minimize-Delay 16 (0x10)
  Maximize-Throughput 8 (0x08)
  Maximize-Reliability 4 (0x04)
  Minimize-Cost 2 (0x02)
  Normal-Service 0 (0x00)

so for the "minimize delay" TOS value, you could write your rule as:

  iptables -t mangle -A PREROUTING -m tos --tos 16 [ ... ]

or

  iptables -t mangle -A PREROUTING -m tos --tos 0x10 [ ... ]

but before you do anything--talk with your ISP and figure out what TOS
setting they are actually using (i.e. "15" is not the right answer).

-j

--
"I hope I didn't brain my damage."
	--The Simpsons