Hi,
> I don't have the -Q option for the ping command, what does it doe on your
> system?
as far as I can guess he talkes about Alexy's ping clone from the iputils
package. It is a enhanced ping with more options, like "-Q".
host_10.0.0.1: ping -help
Usage: ping [-LRUbdfnqrvV] [-c count] [-i interval] [-w wait]
[-p pattern] [-s packetsize] [-t ttl] [-I interface address]
[ -T timestamp option ] [ -Q tos ] host
> Know that ping uses a special type of IP packets, ICMP. I wouldn't be
> surprised if the system changes the DS field automaticly.
Jep, the app sets the DS field (the former TOS field) in the IP
header of the ICMP echo request packets to the choosen value (via
setsockopt). Quit useful for (diffserv) testing...
host_10.0.0.1: ping -Q 0x1a 10.0.0.2
PING 10.0.0.2 (10.0.0.2) from 10.0.0.1 : 56(84) bytes of data.
64 bytes from 10.0.0.2 (10.0.0.2): icmp_seq=0 ttl=244 time=42.965 msec
host_10.0.0.2>: tcpdump icmp
10.0.0.1 > 10.0.0.2: icmp: echo request (DF) [tos 0x1a,ECT]
10.0.0.2 > 10.0.0.1: icmp: echo reply (DF) [tos 0x1a,ECT]
And, look - it really works. Heureka! :)
Kurt
