nanog mailing list archives
Re: rfc 1812 third party address on traceroute
From: Owen DeLong <owen () delong com>
Date: Tue, 31 May 2016 07:35:30 -0700
It seems to me that a plain text reading of RFC-1812 is as Randy describes undesirable. It also seems that the violation of this text is commonplace in actual implementations because of yet another time where operators have made it clear to developers that the IETF is silly. I like the Linux solution... Comply with the RFC by default and provide a knob to do the "right thing" if desired. Best of all would be to put forth an errata against RFC1813 to change the text to specify the inbound interface of the packet triggering the ICMP message when applicable. The behavior currently described should be preserved for ICMP packets which are not triggered by inbound packets. Owen
On May 31, 2016, at 01:27, Job Snijders <job () instituut net> wrote: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
Current thread:
- rfc 1812 third party address on traceroute Randy Bush (May 30)
- Re: rfc 1812 third party address on traceroute Mikael Abrahamsson (May 30)
- Re: rfc 1812 third party address on traceroute Larry Sheldon (May 30)
- Re: rfc 1812 third party address on traceroute Job Snijders (May 31)
- Re: rfc 1812 third party address on traceroute Owen DeLong (May 31)
- Re: rfc 1812 third party address on traceroute William Herrin (May 31)
- Re: rfc 1812 third party address on traceroute Octavio Alvarez (May 31)
- Re: rfc 1812 third party address on traceroute Hugo Slabbert (May 31)
- Re: rfc 1812 third party address on traceroute William Herrin (May 31)
- Re: rfc 1812 third party address on traceroute Mikael Abrahamsson (May 30)