Messaging

Samba Messaging

Multiple smbd processes usually run simultaneously - a main daemon process and couple of connections processes. Samba code has special API that allows different processes send messages each other. There are two implementations of Messaging code - different in current Samba3 and Samba4 code.

Samba 3 implementation

This implementaion uses Tdb file for storing messages and UNIX signals for notifying message receiver.

All messages are stored in messages.tdb file (one can find it in var/locks directory). Each message is just a database record that has six fields:

• messaging version (there is only one version now - 1)
• message type
• sender process id
• receiver process id
• message data length
• message data

There are lot of message types in Samba3, you can see them all in include/messages.h file.

Process sends a message to other process with special function message_send_pid and to all processes with message_send_all. Each process should call message_dispatch routinely to check if messages were received and run appropriate handler.

Samba 4 implementation

This implementation uses UNIX domain sockets.