Summary: ICMP TTL is not decremented
Project: lwIP - A Lightweight TCP/IP stack
Submitted by: jifl
Submitted on: Thursday 04/12/2007 at 02:19
Severity: 2 - Minor
Item Group: Faulty Behaviour
Status: In Progress
Assigned to: jifl
Discussion Lock: Any
I'm not sure that a host have to decrement ttl. I'm agree for a switch or
router. I have experiment on my LAN, and when from my pc, I ping another host
(pc/windows), TTL is the same in the ECHO & ECHO REPLY. When I ping my
router, the TTL is 128 in ECHO packet, and 64 in ECHO REPLY.
I don't have RFC here, do you have check what is the good behavior?
Hmm, yes. After now researching this, I think the reporter got it the wrong
way round. In fact we should send out an echo reply with the TTL reset back
to default. I guess this is because the return route may be assymetric. The
patch is much simpler now.