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Re: [lwip-users] Ping Causing "not enough space for new header size" Ove

From: address@hidden
Subject: Re: [lwip-users] Ping Causing "not enough space for new header size" Over PPP
Date: Mon, 23 May 2016 21:00:42 +0200
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2

Greg Smith wrote:


Using lwIP 2.0.0 Beta1, I have been able to connect my target via PPP to an embedded Linux control.  After successful connection, I am trying to ping the lwIP target.  It has about 25-33% packet loss over time.  From the debug output, I see that I'm occasionally getting a "(not enough space for new header size)" message from pbuf_header_impl() in pbuf.c.


I don't really understand what that's trying to tell me since I'm only receiving about 90 bytes from the ping packet, but I think I have my pbuf size set well above that.  (I've tried setting PBUF_POOL_BUFSIZE to 500, 600, 1500, and 1520).

PBUF_POOL_BUFSIZE has nothing to do with this. This is not a RAM issue but a config issue. Can you tell us the call stack when pbuf_header() fails? Without this info, I can't tell you where the problem is right now...

To give you an insight: when rx packets are fed into the various layers, headers are stripped. pbuf_header() is later used to restore the space for more headers at the front of the buffer. Somehow, this fails for your configuration. This is a only problem when having PPP *AND* ethernet, since the two interfaces require different header sizes...


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