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| From: | Bill Auerbach |
| Subject: | Re: [lwip-users] Incoming packet bigger than PBUF_POOL_BUFSIZE |
| Date: | Thu, 8 Dec 2011 08:19:44 -0500 |
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A pbuf of PBUF_POOL_BUFSIZE is
alloctated for every pbuf_alloc of PBUF_POOL. So PBUF_POOL_BUFSIZE must be the
same or larger than any incoming our outgoing packet that’s going to use a
pbuf_alloc to obtain a packet buffer. I had a similar problem to yours in not
adding ETH_PAD_SIZE (2) to PBUF_POOL_BUFSIZE and every pbuf_alloc for a packet
had a chained pbuf with the second pbuf containing the 2 bytes. PBUF_POOL_BUFSIZE doesn’t constrain
the incoming our outgoing packet size – it’s the maximum size that’s going to
be used for all PBUF_POOL pbuf_allocs. Bill From:
address@hidden
[mailto:address@hidden On Behalf
Of Gary Spivey Thanks, this doesn’t yet work
for me … but it does change the problem and leads me to another question that
might help. It appears that the buffer
allocate does not give me a buffer of the size requested, but constructs a
chain of buffers whose total size is what has been requested. What I have been doing is
getting the buffer address and copying the entire received Ethernet buffer into
that address. With this change, it seems clear that I cannot do this, but that
I have to manage the copy into this chain of buffers. Is there an lwip-provided
method to do this, or do I just need to follow the chain myself? I am looking
through the documentation, but I haven’t found anything yet. -Gary |
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