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From: | Bernhard 'Gustl' Bauer |
Subject: | Re: [lwip-users] ping with packet size greater than MSS |
Date: | Tue, 21 Jul 2009 07:39:01 +0200 |
User-agent: | Thunderbird 2.0.0.22 (Windows/20090605) |
address@hidden schrieb:
Bernhard 'Gustl' Bauer wrote:Hi, how does LWIP treat these pings?Incoming or outgoing? For incoming, IP_REASSEMBLY must be set to 1. For outgoing, IP_FRAG must be set to 1. If so, the pings should be handled correctly. If not, some error counter in LWIP_STATS should be increased.What Kieran remembered was a problem where the incoming ping packet did not have enough memory to be re-used as an outgoing packet (which is the default implementation of ping). However, since LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN defaults to 1 and is not exposed in opt.h, there should be no need to change it.
IP_REASSEMBLY and IP_FRAG are set to 1 by default. I did not change this. I cannot find LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN!! But I'm using some 1.3 version. How can I verify which one? init.h contains no version info.
My TCP_MSS is 1460. A ping -s1472 does work, but a ping -s1473 does not! A large ping can even crash my program.
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