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Re: [lwip-users] Crash in ip_init and very slow ping times


From: Leon Woestenberg
Subject: Re: [lwip-users] Crash in ip_init and very slow ping times
Date: Mon, 03 May 2004 20:16:58 +0200
User-agent: Mozilla Thunderbird 0.5 (Windows/20040207)

Hello Eric,

Eric Shufro wrote:
I have lwip 7.1 working (barely) with ucos-ii and a Motorola hcs12 micro-controller. I have some questions.
>
> First, it crashes within ip_init when a dhcp response arrives.

ip_init() is empty, there is nothing that could crash there.

void ip_init(void) { }


I noticed ip_init checks to see if netif == NULL and in this case, the netif is not null.

You probably mean some other function. Could you re-cap on this please?

Why would lwip check for a null netif when receiving a dhcp response message?

Idem.

Also, I know this may be more of an open ended question, but why on earth are the ping times soooo slow!?

How slow? Should be a few ms for any general microcontroller or processor.

When I wrote a custom protocol stack in motorola assembly, I was getting ping times of <1ms on the same hardware platform. Additionally, when I look at the cpu utilization, it doesn’t seem very busy, even when generating responses.

You should merely find minor overhead from C versus assembly, and so your ping times should be approx. 1 ms as well with lwIP.

lwIP does the minimal stuff *required* by any TCP/IP stack, and cannot
be very much more optimized in its code paths, except for replacing linear search loops by smarter algorithms.

Regards,

Leon.





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