> Also, what is teh purpose of the sequence number at all??? The latter > is used in ipc_buildid() .. but we didnt get the exact purpose of its > existence I believe the original intent was security related. If the IPC id's are monotonously increasing integers starting from zero, it is easy for someone to try attaching to all possible ids (since there are only a small number of them active at any time). If proper permissions aren't set on one of them, they can attach to the IPC entity (shm, sem or msg) and cause some damage. By using the sequence number as a multiplier, the id's are widely spaced. So it takes more effort to scan all IPC id's. Of course, none of this is really valid on Linux, or any other Unix variants that I know of. One can always list all IPC id's (with permissions) using the 'ipcs' command. I don't know if there is any other reason for using the sequence number as multiplier. BTW, seq_max is used to make sure the id wraps around at some point. Ravi. __________________________________________________ Do you Yahoo!? Y! Web Hosting - Let the expert host your web site http://webhosting.yahoo.com/ -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
