============================================================================ README DOCUMENT FOR ASYNCHRONOUS REVERSE NAME RESOLVING ---------------------------------------------------------------------------- DESCRIPTION ----------- IPTraf-ng incorporates a function to resolve IP addresses to host names in the background, keeping IPTraf-ng from waiting until the lookup is completed. If Reverse Lookup is enabled in the Options menu, the IP Traffic Monitor will fork another process and this process will attempt to resolve addresses. When the traffic monitor is done, IPTraf-ng tells this resolving process to quit. PROTOCOL -------- Resolving process and IPTraf-ng communicate with each other with the UNIX domain socket IPC facility. They use datagram sockets. The communication protocol recognizes only 4 types of messages: RVN_HELLO the Hello packet. This simply causes to throw it back, telling it is active. RVN_REQUEST a reverse lookup request. This message includes an IP address to resolve. Upon receive of this request, resolving process checks its internal cache to see if this IP address is already resolved or being resolved. If it isn't in the cache yet, it forks off a copy which resolves in the background, while it returns the IP address in the meantime. Subsequent requests will get the IP address until such time that the child has completed the resolution, at which time, a request will get the host name in reply. RVN_REPLY resolving process marks reply packets with this tag. Reply packets contain the resolved host name or the ASCII representation of the IP address, and an indicator of the state of the resolution for this address (NOTRESOLVED, RESOLVING or RESOLVED). RVN_QUIT Tells resolving process to terminate. The datagram structure and #define's are found in the rvnamed.h header file. Important rvnamed messages are written to /var/log/iptraf-ng/rvnamed.log.