[bug#63508] [PATCH] gnu: udev: Allow EUDEV_RULES_DIRECTORY to shadow built-in rules.

[Liliana Marie Prikler <liliana.prikler@gmail.com>]

* gnu/packages/patches/eudev-rules-directory.patch (rules_dirs):
Move placeholder to the start of the array.
(rules_dirs_real): New procedure.
(udev_rules_dirs_new, udev_rules_check_timestamp): Adjust accordingly.
---
Hi Felix,

Am Sonntag, dem 14.05.2023 um 21:56 -0700 schrieb Felix Lechner:
> > I don't see how this change allows users *or upstream package
> > maintainers* to continue using onboard names as they have done for
> > ages and as they would want to continue to do.
> 
> I have one of those cards. While the interface name did not change
> when I fiddled with the PCI configuration, I am not sure that
> prioritizing ID_NET_NAME_ONBOARD over ID_NET_NAME_MAC is a reasonable
> default for Guix.
> 
> To rank ID_NET_NAME_ONBOARD below ID_NET_NAME_MAC would not address
> the shortcoming you perceived because the latter always exists.
> 
> Instead, I think people wishing to use ID_NET_NAME_ONBOARD should
> install a custom udev script (and those should be recognized by the
> udevadm we ship).
I think the current default is probably fine for more users than the
proposed change (ain't no one got the time to type their MAC addresses).

I do however see your point in that udev should let you choose to prefer
ID_NET_NAME_MAC over the other rules.  Now, the shortcoming here
actually lies with our incomplete support for EUDEV_RULES_DIRECTORY,
see the patch :)

> For Guix, I think we would like to see ID_NET_NAME_MAC at the top.
Now, I respectully disagree on that proposition, but am here to fix the
original bug of udev not honouring your preference.  With the following
patch your udev-rule-service should be able to override the default
behaviour.  If not, try matching the file name.  There shouldn't be any
weird predicates on the name, but if there are, that's how we'll find
out.

Cheers

 .../patches/eudev-rules-directory.patch       | 44 ++++++++++++++++---
 1 file changed, 37 insertions(+), 7 deletions(-)

diff --git a/gnu/packages/patches/eudev-rules-directory.patch b/gnu/packages/patches/eudev-rules-directory.patch
index 54fc01c6d5..7cc3f97451 100644
--- a/gnu/packages/patches/eudev-rules-directory.patch
+++ b/gnu/packages/patches/eudev-rules-directory.patch
@@ -4,14 +4,17 @@ The old udev 182 supported $UDEV_CONFIG_FILE, which in turn allowed
 the search path to be customized, but eudev no longer has this, hence
 this hack.
 
---- eudev-3.1.5/src/udev/udev-rules.c	2015-10-13 06:22:14.000000000 +0800
-+++ eudev-3.1.5/src/udev/udev-rules.c	2015-10-16 20:45:38.491934336 +0800
-@@ -47,15 +47,11 @@
+Index: eudev/src/udev/udev-rules.c
+===================================================================
+--- eudev.orig/src/udev/udev-rules.c
++++ eudev/src/udev/udev-rules.c
+@@ -48,15 +48,11 @@ struct uid_gid {
          };
  };
  
 -static const char* const rules_dirs[] = {
 +static const char* rules_dirs[] = {
++        NULL,			/* placeholder for $EUDEV_RULES_DIRECTORY */
          UDEV_CONF_DIR "/rules.d",
          UDEV_RULES_DIR,
 -        UDEV_ROOT_RUN "/udev/rules.d",
@@ -20,17 +23,44 @@ this hack.
 -        "/lib/udev/rules.d",
 -        "/usr/lib/udev/rules.d",
 -#endif
-+        NULL,			/* placeholder for $EUDEV_RULES_DIRECTORY */
          NULL};
  
  struct udev_rules {
-@@ -1704,6 +1700,9 @@
+@@ -1691,6 +1687,14 @@ static int parse_file(struct udev_rules
+         return 0;
+ }
+ 
++static const char** rules_dirs_real()
++{
++        if (rules_dirs[0])
++                return rules_dirs;
++        else
++                return rules_dirs + 1;
++}
++
+ struct udev_rules *udev_rules_new(struct udev *udev, int resolve_names) {
+         struct udev_rules *rules;
+         struct udev_list file_list;
+@@ -1717,7 +1721,10 @@ struct udev_rules *udev_rules_new(struct
  
          udev_rules_check_timestamp(rules);
  
+-        r = conf_files_list_strv(&files, ".rules", NULL, rules_dirs);
 +        /* Allow the user to specify an additional rules directory.  */
-+        rules_dirs[3] = getenv("EUDEV_RULES_DIRECTORY");
++        rules_dirs[0] = getenv("EUDEV_RULES_DIRECTORY");
 +
-         r = conf_files_list_strv(&files, ".rules", NULL, rules_dirs);
++        r = conf_files_list_strv(&files, ".rules", NULL, rules_dirs_real ());
          if (r < 0) {
                  log_error_errno(r, "failed to enumerate rules files: %m");
+                 return udev_rules_unref(rules);
+@@ -1776,7 +1783,9 @@ bool udev_rules_check_timestamp(struct u
+         if (!rules)
+                 return false;
+ 
+-        return paths_check_timestamp(rules_dirs, &rules->dirs_ts_usec, true);
++        return paths_check_timestamp(rules_dirs_real (),
++                                     &rules->dirs_ts_usec,
++                                     true);
+ }
+ 
+ static int match_key(struct udev_rules *rules, struct token *token, const char *val) {

base-commit: 28bfc5cd081458313fa8601133386209b23deb12
-- 
2.40.1