Re: [lwip-users] PPP: how to enable the MRU negotiation?

[Simon Goldschmidt]

I'll try to help, anyway:

Having had a quick look at RFC 1661, it seems like we would always have to 
support an MRU of 1500 at least (chapter 6.1 in that RFC). 

- PPP_MRU is set to 1500, which also is used as the rx/tx buffer size (if I see 
that correctly).
- PPP_MAXMRU has been changed from 16384 (pppd) to 1500 (lwIP), but I don't 
think that's a problem as 2 ppp instances seem to need to actively agree on 
that to make it happen
- PPP_MINMRU is still 128
- PPP_DEFMRU has been changed from 1500 (pppd) to 296 (lwIP).

Now from reading the code, to me it seems as lwIP would send PPP_DEFMRU as the 
MRU option but go on normally with the connection receiving 1500-byte-sized 
packets, or am I wrong there?

In any case, you could just add "#define PPP_DEFMRU 1500" to your lwipopts.h 
and you'd have the original pppd behaviour.

Simon
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