On Mon, May 30, 2016 at 10:03:33PM -0700, Randy Bush wrote:
> .-----------------.
> | |
> | B |--------- D
> S ---------| A R |
> | C |--------- (toward S)
> | |
> `-----------------'
>
> if the source of a traceroute from S toward D with TTL to expire on R,
> and R's FIB wants to exit via C to get back to S (yes, virginia, the
> internet is highly asymmetric), the source address of the time exceeded
> message should be C.
>
> of course, simpletons such as i would desire the source of the time
> exceeded message to be A. after all, this is the interface to which i
> sent the icmp with the TTL to expire.
>
> is anyone seeing the dreaded rfc1812 behavior in a citable fashion? how
> common is it?
On most Linux the default behaviour is using source address "C", but
this can be corrected by setting the following somewhere in your
/etc/sysctl.d/ files:
# make traceroute nice
net.ipv4.icmp_errors_use_inbound_ifaddr=1
Kind regards,
Job
