Re: [lwip-users] question about pbuf_chain

[Mike Tesch]

Hey,

I realized just after I sent it that I should have included a diff
to show what I meant more clearly...  The tot_len update never gets
done if p->next is NULL...

@@ -706,12 +706,14 @@
  LWIP_ASSERT("t != NULL", t != NULL);

  /* proceed to last pbuf of chain */
-  for (p = h; p->next != NULL; p = p->next) {
+  for (p = h; p != NULL; p = p->next) {
    /* add total length of second chain to all totals of first chain */
    p->tot_len += t->tot_len;
  }


Regards,
mt


David Haas wrote:

> Hi,
>
> I had some questions about that code too, but I actually think it 
> works. In the old definition of tot_len, it is only set in the first 
> buffer of the chain. This code makes sure that's true and also sets it 
> in the other buffers in the chain. Upon inspection, I think its OK, 
> but I am just stepping through udp_send() now. I'll let you know what 
> I find.
>
> regards,
> David.
>
> Mike Tesch wrote:
>
> > Hello,
> >
> > I'm having a problem sending udp data through the sockets interface ;-)
> >
> > I think part of it is because pbuf_chain() is updating tot_len 
> > incorrectly.
> > Just to clarify, tot_len is "the sum of 'len' of all pbufs following 
> > this one?"
> >
> > Is the following correct?
> > (changed line marked by <<<<<<<)
> >
> > void
> > pbuf_chain(struct pbuf *h, struct pbuf *t)
> > {
> >  struct pbuf *p;
> >
> >  LWIP_ASSERT("h != NULL", h != NULL);
> >  LWIP_ASSERT("t != NULL", t != NULL);
> >
> >  /* proceed to last pbuf of chain */
> >  for (p = h; p != NULL; p = p->next) { <<<<<<<<
> >    /* add total length of second chain to all totals of first chain */
> >    p->tot_len += t->tot_len;
> >  }
> >  /* chain last pbuf of h chain (p) with first of tail (t) */
> >  p->next = t;
> >  /* t is now referenced to one more time */
> >  pbuf_ref(t);
> >  DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_chain: referencing tail 
> > %p\n", (void *) t));
> > }
> >
> >
> >
> >
> > _______________________________________________
> > lwip-users mailing list
> > address@hidden
> > http://mail.nongnu.org/mailman/listinfo/lwip-users
>
>
>
>
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