Re: [libvirt] [PATCH v2 5/6] util: Add helpers for safe domain console operations

This patch adds a set of functions used in creating console streams for domains using PTYs and ensures mutualy exculsive access to the PTYs.

If mutualy exclusive access is not used, two clients may open the same

console, which results into corruption on both clients as both of them

race to read data from the PTY. Two approaches are used to ensure this: 1) Internal data structure holding open PTYs. This is used internaly and enables the user to forcibly

terminate another console connection eg. when somebody leaves the console open on another host. 2) UUCP style lock files: This uses UUCP lock files according to the FHS ( http://www.pathname.com/fhs/pub/fhs-2.3.html#VARLOCKLOCKFILES )

to check if other programs (like minicom) are not using the pty device of the console. This feature is disabled by default and may be enabled using configure parameter --with-console-lock-files=/path/to/lock/file/directory or --with-console-lock-files=auto (which tries to infer the location from OS used (currently only linux). On usual linux systems, normal users may not write to the /var/lock directory containing the locks. This poses problems while in session mode. If the current user has no access to the lockfile directory, check for presence of the file is still done, but no lock file is created. This does NOT result into an error. * configure.ac - add option to enable UUCP style PTY file locks * src/Makefile.am - add new files to be built with util module * src/libvirt_private.syms - add private symbol definition * src/util/domain_safe_console.c - implementation of safe console handling * src/util/domain_safe_console.h - header files --- configure.ac | 37 +++- src/Makefile.am | 5 +- src/libvirt_private.syms | 6 + src/util/domain_safe_console.c | 399 ++++++++++++++++++++++++++++++++++++++++ src/util/domain_safe_console.h | 28 +++ 5 files changed, 466 insertions(+), 9 deletions(-) create mode 100644 src/util/domain_safe_console.c create mode 100644 src/util/domain_safe_console.h