p2v-hacking(1)

NAME
p2v-hacking - extending and contributing to virt-p2v

DESCRIPTION
This manual page is for hackers who want to extend virt-p2v itself.

Virt-p2v is a front end on virt-v2v. ie. All it does is act as a GUI front end, and it calls out to virt-v2v to perform the actual conversion. Therefore most of the C code is Gtk (GUI) code, or supporting code for talking to the remote conversion server. There is no special support for physical machines in virt-v2v. They are converted in the same way as foreign VMs.

THE SOURCE CODE
Virt-p2v source is located in the github repository https://github.com/libguestfs/virt-p2v

Virt-p2v uses an autotools-based build system, with the main files being configure.ac and Makefile.am. See "THE BUILD SYSTEM".

To build from source, first read the p2v-building(1).

  SOURCE CODE SUBDIRECTORIES
The majority of the source code is directly in the top level directory of the sources. There are also some subdirectories that contain some specific sub-parts of virt-p2v.

bash
    Bash tab-completion scripts.

build-aux
    Various build scripts used by autotools.

miniexpect
    A copy of the miniexpect library from http://git.annexia.org/?p=miniexpect.git;a=summary.

contrib
    Outside contributions, experimental parts.

docs
    Miscellaneous manual pages.

libguestfs
    Some sources (mostly with utilities) copied from libguestfs. Changes to the sources there ought to be forwarded to libguestfs as well.

m4  M4 macros used by autoconf. See "THE BUILD SYSTEM".

website
    The virt-p2v files of the http://libguestfs.org website.

  THE BUILD SYSTEM
Virt-p2v uses the GNU autotools build system (autoconf, automake).

The ./configure script is generated from configure.ac and m4/p2v-*.m4. Most of the configure script is split over many m4 macro files by topic, for example m4/p2v-libraries.m4 deals with the libraries required by virt-p2v.

subdir-rules.mk is included in every Makefile.am (top level and subdirectories).

  UNDERSTANDING THE CODE
See also: "HOW VIRT-P2V WORKS" in virt-p2v(1)

There are two paths through the code, GUI or non-GUI (parsing the kernel command line):

 main.c ──────┬─────▶ gui.c ──────┬─────▶ conversion.c
              │                   │
              │                   │
              └────▶ kernel.c ────┘

but both paths call back to the conversion.c function "start_conversion" to run the remote virt-v2v.

The main task of gui.c/kernel.c is to populate the virt-v2v configuration (config.c).

During conversion, we need to establish ssh connections, and that is done using two libraries:

 conversion.c ──────▶ ssh.c ──────▶ miniexpect.c

where ssh.c is responsible for managing ssh connections overall, and miniexpect.c implements "expect-like" functionality for talking interactively to the remote virt-v2v conversion server.

(Note that miniexpect is a separate library with its own upstream, so if you patch miniexpect.c, then please make sure the changes get reflected in miniexpect’s upstream too: http://git.annexia.org/?p=miniexpect.git;a=summary)

RUNNING VIRT-P2V
You can run the virt-p2v binary directly, but it will try to convert your machine’s real /dev/sda which is unlikely to work well. However virt-p2v also has a test mode in which you can supply a test disk:

 make run-virt-p2v-directly

This is a wrapper around the virt-p2v(1) --test-disk option. You can control the "physical machine" disk by setting "PHYSICAL_MACHINE" to point to a disk image.

A more realistic test is to run virt-p2v inside a VM on the local machine. To do that, do:

 make run-virt-p2v-in-a-vm
 make run-virt-p2v-in-an-nvme-vm

These also run qemu with the "physical machine" disk (which you can set by setting "PHYSICAL_MACHINE"), a virtual CD, and a variety of network cards for testing. The second target exposes the "physical machine" disk as an NVMe controller, plus adds two blank disks as distinct namespaces of another NVMe controller. You can change the qemu binary and add extra qemu options by setting "QEMU" and/or "QEMU_OPTIONS" on the make commandline.

A third way to run virt-p2v simulates fairly accurately the program being downloaded over PXE and then doing an automatic conversion of the source physical machine (the non-GUI path -- see next section below):

 make run-virt-p2v-non-gui-conversion

EXTENDING VIRT-P2V

  FORMATTING CODE
Our C source code generally adheres to some basic code-formatting conventions. The existing code base is not totally consistent on this front, but we do prefer that contributed code be formatted similarly. In short, use spaces-not-TABs for indentation, use 2 spaces for each indentation level, and other than that, follow the K&R style.

If you use Emacs, add the following to one of your start-up files (e.g., ~/.emacs), to help ensure that you get indentation right:

 ;;; In virt-p2v, indent with spaces everywhere (not TABs).
 ;;; Exceptions: Makefile and ChangeLog modes.
 (add-hook 'find-file-hook
     '(lambda () (if (and buffer-file-name
                          (string-match "/virt-p2v\\>"
                              (buffer-file-name))
                          (not (string-equal mode-name "Change Log"))
                          (not (string-equal mode-name "Makefile")))
                     (setq indent-tabs-mode nil))))

 ;;; When editing C sources in virt-p2v, use this style.
 (defun virt-p2v-c-mode ()
   "C mode with adjusted defaults for use with virt-p2v."
   (interactive)
   (c-set-style "K&R")
   (setq c-indent-level 2)
   (setq c-basic-offset 2))
 (add-hook 'c-mode-hook
           '(lambda () (if (string-match "/virt-p2v\\>"
                               (buffer-file-name))
                           (virt-p2v-c-mode))))

  TESTING YOUR CHANGES
Turn warnings into errors when developing to make warnings hard to ignore:

 ./configure --enable-werror

Useful targets are:

"make check"
    Runs the regular test suite.

    This is implemented using the regular automake "TESTS" target. See the automake documentation for details.

"make check-valgrind"
    Runs a subset of the test suite under valgrind.

"make check-slow"
    Runs some slow/long-running tests which are not run by default.

    To mark a test as slow/long-running:

    •   Add it to the list of "TESTS" in the Makefile.am, just like a normal test.

    •   Modify the test so it checks if the "SLOW=1" environment variable is set, and if not set it skips (ie. returns with exit code 77). If using $TEST_FUNCTIONS, you can call the function "slow_test" for this.

    •   Add a variable "SLOW_TESTS" to the Makefile.am listing the slow tests.

    •   Add a rule to the Makefile.am:

         check-slow:
           $(MAKE) check TESTS="$(SLOW_TESTS)" SLOW=1

  VALGRIND
When you do "make check-valgrind", it searches for any Makefile.am in the tree that has a "check-valgrind:" target and runs it.

Writing the Makefile.am and tests correctly to use valgrind and working with automake parallel tests is subtle.

If your tests are run via a shell script wrapper, then in the wrapper use:

 $VG virt-foo

and in the Makefile.am use:

 check-valgrind:
     make VG="@VG@" check

However, if your binaries run directly from the "TESTS" rule, you have to modify the Makefile.am like this:

 LOG_COMPILER = $(VG)

 check-valgrind:
     make VG="@VG@" check

In either case, check that the right program is being tested by examining the valgrind* log files carefully.

  SUBMITTING PATCHES
Submit patches to the mailing list: https://lists.libguestfs.org and CC to rjones@redhat.com.

You do not need to subscribe to the mailing list if you don’t want to. There may be a short delay while your message is moderated.

SEE ALSO
p2v-building(1), p2v-release-notes(1), http://libguestfs.org/.

AUTHORS
Richard W.M. Jones ("rjones at redhat dot com")

COPYRIGHT
Copyright (C) 2009-2019 Red Hat Inc.

LICENSE
This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this program. If not, see <https://www.gnu.org/licenses/>.

BUGS
To get a list of bugs against libguestfs (which include virt-p2v), use this link: https://bugzilla.redhat.com/buglist.cgi?component=libguestfs&product=Virtualization+Tools

To report a new bug against libguestfs, use this link: https://bugzilla.redhat.com/enter_bug.cgi?component=libguestfs&product=Virtualization+Tools

When reporting a bug, please supply:

•   The version of virt-p2v.

•   Where you got virt-p2v (eg. which Linux distro, compiled from source, etc)

•   Describe the bug accurately and give a way to reproduce it.