Use own namespace

[T-X]

This patchset allows loading and running the mainline batman-adv (compat 15) and the batman-adv-legacy (compat 14) fork simultaneously.

Together with the gluon-scheduled-domain-switch package (freifunk-gluon/gluon#1555) this should ease the migration from compat 14 to compat 15 and speed-up the deprecation of this fork.

(Changing the module name was first proposed in #3 three years ago.)

[ecsv]

The build fails here against /usr/src/linux-headers-4.18.0-2-amd64 with

make[1]: Leaving directory '/usr/src/linux-headers-4.18.0-2-amd64'
objcopy: /home/sven/tmp/batman-adv-legacy/updated-syms.txt: Multiple redefinition of symbol "batadv_compare_eth"
make: *** [Makefile:61: updatesyms] Error 

This really seems to be the case:

$ grep -r batadv_compare_eth /home/sven/tmp/batman-adv-legacy/updated-syms.txt 
batadv_compare_eth batadv_legacy_compare_eth
batadv_compare_eth batadv_legacy_compare_eth

I've worked around it via

diff --git a/Makefile b/Makefile
index 657d4ee..4ee9ffa 100644
--- a/Makefile
+++ b/Makefile
@@ -60,8 +60,9 @@ build: config
 updatesyms:
 	@if ! $(OBJDUMP) -j .init.text -t batman-adv-legacy.ko| grep -q "batadv_legacy_init"; then \
 		$(OBJDUMP) -t batman-adv-legacy.ko | grep batadv_ | grep -v "batadv_legacy" | \
-			sed "s/.* \([^ ]*\)batadv_\([^ ]*\)$$/\1batadv_\2 \1batadv_legacy_\2/" \
-				>> $(PWD)/updated-syms.txt; \
+			sed "s/.* \([^ ]*\)batadv_\([^ ]*\)$$/\1batadv_\2 \1batadv_legacy_\2/" | \
+			sort | uniq \
+				> $(PWD)/updated-syms.txt; \
 		$(OBJCOPY) --redefine-syms=$(PWD)/updated-syms.txt $(PWD)/batman-adv-legacy.ko; \
 	fi

[neocturne]

These are some things that should be fixed if we decide to merge this.

[neocturne]

As this is always built out-of-tree, I don't see a point in renaming these config symbols.

[neocturne]

Let's not touch this file and generate a batman-adv.ko from this build step.

[neocturne]

Using the same filename for input and output of the objcopy is making this more fragile than necessary. Just use batman-adv.ko as input, batman-adv-legacy.ko as output, and drop the whole if conditional.

We can use proper file targets then, which will also improve error handling:

• rename build to batman-adv.ko
• rename updatesyms to batman-adv-legacy.ko
• create a proper target to updated-syms.txt
• properly define dependencies between the different targets

[neocturne]

Add a space between compat and 14?

[neocturne]

I'm not really a fan of these changes. I don't see why it should be necessary to load both modules at the same time to allow a scheduled domain switch - shouldn't it be enough to be able to install both modules into the same image, and decide at runtime which one to load? That way we would need to adjust way less code to the "-legacy" namespace (batctl calls, netlink queries, ...).

[T-X]

Good point. You are right, the scheduled domain switcher will trigger a reboot anyway. And not making both loadable at the same time would indeed make this pull-request way simpler.

The one advantage to be able to load both modules simultaneously I can think of right now would to ease migration on the gateway side. Summing up the list in the wiki there are currently 39 site.conf/mk's of which 13 are still using batman-adv-legacy/compat-14 (counting Freifunk Rheinland as one).

With being able to load modules simultaneously it would probably just be a "git clone, run these dkms commands to build and install, update a few config lines". Compared to a setting up and integrating a new, additional system/OS somehow.

Depending on how active these 13 communities still are and how quick they'd be in setting up a new VM or root server we would need to maintain the batman-adv-legacy fork for a longer or shorter amount of time.

(anyone from these 13 communities having some opinion or strong preference?)

[T-X]

Changelog v2:

• "compat14" -> "compat 14" in main.h
• Makefile: use file targets instead of PHONY ones (I could not remove the renaming of the object targets in Makefile.kbuild though, it seems that obj-m += <module_name>.ko determines the loaded modules name. when I tried to not rename that the loaded batman-adv-legacy module was still listed as "batman_adv" in lsmod.)
• Added a "| sort | uniq >" to prevent duplicate symbol renaming lines with some compilers
• Dumped the CONFIG_ renames ("batman-adv-legacy: Add "LEGACY" infix to CONFIG parameters")

Edit:

• removed the unnecessary sysfs rename of /sys/class/net/bat0/mesh to mesh_legacy in "batman-adv-legacy: Changing batman-adv sysfs directory". There is no clash as bat0 always belongs to either batman-adv or batman-adv-legacy. This fixes some previously ignored parameters set in /etc/config/batman-adv and alfred init script start up issues.