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Re: [lwip-users] Add new header & tail
From: |
dhosa |
Subject: |
Re: [lwip-users] Add new header & tail |
Date: |
Wed, 12 Sep 2018 14:48:01 -0700 (MST) |
@Sergio R. Caprile Thank you for time ,
Sergio R. Caprile wrote
> Perhaps if you could think your actions in terms of OSI layers it would
> be easier to understand.
> You say "before IP" but you draw "after IP" (well, sort of...), so I
> don't really get what you need.
Layer 3 in OSI layers, The new header will be between IP header and (TCP |
UDP) header and tail at the end.
Sergio R. Caprile wrote
> What is it that you are trying to accomplish, do you want to encapsulate
> TCP/IP into an "ESP" (whatever it is) datagram/frame ?
Exactly, below figure shows IP packet before and after (ignore encryption &
auth)
<http://lwip.100.n7.nabble.com/file/t2118/ESPheader.png>
Sergio R. Caprile wrote
> or do you want to run that "ESP" protocol over IP ?
phase 2
Sergio R. Caprile wrote
> If "ESP" runs over Ethernet, you handle this at the netif level, outside
> lwIP. Instead of lwIP calling and being called by the netif, you add a
> netif layer that is
> outbound: called by lwIP and calls the netif output function. Basically
> you replace netif->output by your output function, which after adding
> header and footer calls what was in there.
> inbound: called by the netif and calls the lwIP input function, which
> depends on whether you are actually using an OS or not (baremetal).
> Basically, conversely, you replace netif->input by your function, which
> after removing header and footer calls what was in there.
>
> Running "ESP" over IP requires you use the "raw IP" access functions.
> Having other TCP/IP stack protocols over this is a bit trickier, since
> you need to sit "in the middle" inside lwIP. I personally don't know how
> to do this.
Interesting .
Note:
I am using FreeRTOS With LwIP (1.4.1) .
--
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