[CSE]  Advanced Operating Systems 
 COMP9242 2002/S2 
UNSW

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Next: Example: Send Call Up: 01-l4 Previous: IPC System Call Overview

Deceiving IPC

Clans & chiefs mechanism is supported by a feature called deceiving:
  • If ``deceit'' bit is set by sender, L4 will lie to the receiver about the sender, delivering the sender-specified virtual sender ID
  • The receiver is alerted to the deceit by the deceit bit in the return status
  • Deceiving only works if direction preserving, i.e., if the real sender is along the redirection chain from the virtual sender to the receiver:
    • message goes out of clan and virtual sender ID is within clan (or subclan), or
    • message goes to subclan and virtual sender ID is outside clan.
  • Used by chief to make inter-clan IPC interception transparent to clients



Gernot Heiser 2002-08-07