Hello!
I have a dissector that is added to handle tcp.port == 14000 which works
well until segmented PDUs are received.
I read section 2.7 "Reassembly/desegmentation" in the README.developer
but cannot seem to get it work the way I want.
When my dissector gets called I do (OCP_HEADER_SIZE = 4):
if(data_length < OCP_HEADER_SIZE)
{
/* Make sure that the entire OCP header is readable before dissection
begins */
pinfo->desegment_offset = data_length;
pinfo->desegment_len = OCP_HEADER_SIZE - data_length;
return;
}
else
{
/* At least the OCP header should be received by now */
g_assert(data_length >= OCP_HEADER_SIZE);
ocp_message_length = tvb_get_ntohs(tvb, 0) + OCP_HEADER_SIZE;
/* Make sure that at least one whole OCP PDU is ready for dissection */
if(data_length != ocp_message_length)
{
if(data_length < ocp_message_length)
{
/* Too little data for dissection */
pinfo->desegment_offset = data_length;
pinfo->desegment_len = ocp_message_length - data_length;
return;
}
else
{
/* More than one OCP message exists in the PDU, make sure that
the next OCP message is dissected later */
pinfo->desegment_offset = ocp_message_length;
pinfo->desegment_len = data_length - ocp_message_length;
}
}
}
If the data_length was 3 in the first call to the dissector I return
that I want 1 additional byte from offset 3 in the next received tvb.
This is probably where I have misunderstood something. The next tvb I
receive contains the additional bytes that I requested, but only those.
Hence the 3 bytes received the first time are now lost.
I thought that I should be able to handle the PDU in its entirety. What
am I missing?
/ Regards, Peter
