[lwip-users] Re: [lwip] Memory leak and queued packets in etharp.c

[Adam Dunkels]

Hi!

On Mon, 2002-11-11 at 16:51, address@hidden wrote:
> > > Another issue is the queueing of packets that
> > > are created by the user code with netbuf_ref().
> > > This creates a chained pbuf with at least one
> > > one element having the attribute PBUF_ROM.
> > > There's a pending danger that the data part
> > > of such a buffer gets overwritten by the
> > > application before the queued packet is sent.
> > > Should these be copied?
> 
> > The application must only overwrite that area when it's
> > certain that it got sent.How it is to be notified I don't know.
> > But the point of PBUF_ROM is to tell the stack not to copy so
> > I think it shouldn't.
> >
> Very good mentioning this, as this is an outstanding issue not
> yet resolved.

Pbufs of type PBUF_ROM are never supposed to be overwritten by the
application (hence the name ROM = Read Only Memory). If there are
problems with netbuf_ref() and pbufs, it is better to change the netbuf_
API than the core code.

So: no copying of PBUF_ROM pbuf, since this should have been done by the
application (into a PBUF_RAM pbuf) if the application intended to
overwrite the data.

Cheers,

/adam

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