On Thu, Feb 08, 2007 at 10:53:37PM -0600, Pisano, Edward A wrote: > Hi all, > It's interesting that this e-mail thread came up when it did. I just > noticed that I, too, see the same 2 byte offset issue with the payload > after the headers have been removed.
I don't have the source to hand, and this is from memory, so perhaps not very accurate... The ethernet frame header is of course 14 bytes. The reason I suspect that the PBUF_LINK_HLEN is set to 16 bytes is to ensure that subsequent headers and payload are aligned to a 4 byte boundary. This is configurable if this is not what you require. > I'm using the xemac driver from XiLinx to interface lwIP to their EMAC > core. It has a hardcoded value of 14 in it for, what appears to be, > removing the Ethernet Frame (6 byte dest. Addr + 6 byte src. Addr + 2 > byte type) from the payload on received packets. Although, > PBUF_LINK_HLEN is defined as 16, it only appears to be used for > transmitted packets. For received packets you may need the help of the network driver to ensure that there is a 2 byte padding at the start of the frame to ensure that subsequent headers and payload are aligned to your requirements. Kieran _______________________________________________ lwip-users mailing list [email protected] http://lists.nongnu.org/mailman/listinfo/lwip-users
