[Guy Harris <gharris@xxxxxxxxx>]

TJ Li wrote:

> What is purpose of pinfo->fd->flags.visited?

To allow dissectors to do something differently the first time a packet 
is seen, for example to save state for subsequent dissections of the packet.

> The core dump happened because pinfo->fd->flags.visited is 1 in packet-dcerpc-mapi.c, but
> mmd=g_hash_table_lookup(mapi_decrypted_table, &mmd_key) return NULL.

The MAPI dissector was "decrypting" (if you call XORing data with 0xA5 
"encrypting" it) the packet data and saving the decrypted data on the 
first pass, and trying to fetch the decrypted data on subsequent passes 
- but it wasn't finding the data, for some reason.

It's probably simpler just to decrypt the data every time; I've checked 
in a change to do that, which should fix this crash.