[ee122] Extracting our datagram from packet_parser

Lisa Fowler fowler at eecs.berkeley.edu
Mon Dec 10 10:05:05 PST 2007

On Dec 10, 2007 9:49 AM,  <waden at berkeley.edu> wrote:
> Hi, right now Im working on the packet_parser and I just wanted to make
> sure that our full UDP datagram with payload is encapsulated within the
> real UDP/IP/ETHERNET headers.

Your UDP payload, which includes your custom protocol's header and
payload, are encapsulated within the headers Ethernet>IP>UDP>

So, Ethernet>IP>UDP>YourHeaderGoesHere>YourPayload

>  Second, that the capture_len variable
> refers to the length in bytes of the "packet" argument, because when I
> printf the variable at the beginning of the function its only between like
> 50 and 80.  Thanks!

>From the comments:

 * Note that "capture_len" is the length of the packet *as captured by the
 * tracing program*, and thus might be less than the full length of the
 * packet.  However, the packet pointer only holds that much data, so
 * we have to be careful not to read beyond it.

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