Subject: [6lowpan] question about IP payload length computation in BLip

From: amy wang <[email-masked]>
Date: Mon, 21 Jun 2010 11:20:01 +0800

hi,
In lib6lowpanIP.c the payload length can be computed in two ways and if the
packet has no fragmentation header:
/////////////
    size = pkt->len - (buf - pkt->data);
    size += extra_header_length;
    size -= getLowpanPayload(pkt) - pkt->data;
////////////
The first step we get the size of payload excluding headers.
The second step we set the size to include the UDP or EXT headers as they
are also the payload of IPv6.
I don't know the third step mean?Why should we subtract the 6lowpan headers?
Where we have include the 6lowpan headers in size?

Hope someone can help.
thanks very much.

Amy