[lwip-users] PBUF_RAM etc

[Mason]

Hello,

Can you explain why the pbuf struct and the payload buffer
need to be contiguous? What problems are solved by having
the struct and the buffer stored contiguously?

There is a pointer to a buffer in the struct, it is redundant
if the payload is at a known offset, right?

Simon once wrote to me:
> The problem here is that pbuf_header() can't grow such pbufs (as it
> doesn't know the original length). This would have to be fixed by
> changing the struct pbuf (if only for PBUF_REF pbufs).

What does it mean? What is pbuf_header supposed to do?
And what does it mean to grow a pbuf?

-- 
Regards.