udev: Introduce UDEV_PROPAGATE_LOG macro (#5302)

As per commit 25e773e "udev: switch to systemd logging functions"
Now log_set_max_level() in udev_new() overwites system wide log level.

Propagate the udev.conf setting to log_set_max_level()
only if udev_new() is called from within udevd or one of its helpers.

Introduce a UDEV_PROPAGATE_LOG macro that we set with -D on
the gcc command line for all udev binaries we build, but not
for any others. The log_set_max_level() call is guarded by an
ifdef check for that macro, so that it only effects the various
udev binaries.

closes: #4525

Makefile.am

@@ -3914,7 +3914,8 @@ gperf_gperf_sources += \
 libudev_core_la_CFLAGS = \
 	$(AM_CFLAGS) \
 	$(BLKID_CFLAGS) \
-	$(KMOD_CFLAGS)
+	$(KMOD_CFLAGS) \
+	-D UDEV_PROPAGATE_LOG
 
 libudev_core_la_LIBADD = \
 	libsystemd-network.la \
@@ -4089,6 +4090,10 @@ EXTRA_DIST += \
 ata_id_SOURCES = \
 	src/udev/ata_id/ata_id.c
 
+ata_id_CFLAGS = \
+	$(AM_CFLAGS)
+	-D UDEV_PROPAGATE_LOG
+
 ata_id_LDADD = \
 	libshared.la
 
@@ -4099,6 +4104,10 @@ udevlibexec_PROGRAMS += \
 cdrom_id_SOURCES = \
 	src/udev/cdrom_id/cdrom_id.c
 
+cdrom_id_CFLAGS = \
+	$(AM_CFLAGS)
+	-D UDEV_PROPAGATE_LOG
+
 cdrom_id_LDADD = \
 	libshared.la
 
@@ -4112,6 +4121,10 @@ dist_udevrules_DATA += \
 collect_SOURCES = \
 	src/udev/collect/collect.c
 
+collect_CFLAGS = \
+	$(AM_CFLAGS)
+	-D UDEV_PROPAGATE_LOG
+
 collect_LDADD = \
 	libshared.la
 
@@ -4125,6 +4138,10 @@ scsi_id_SOURCES =\
 	src/udev/scsi_id/scsi.h \
 	src/udev/scsi_id/scsi_id.h
 
+scsi_id_CFLAGS = \
+	$(AM_CFLAGS)
+	-D UDEV_PROPAGATE_LOG
+
 scsi_id_LDADD = \
 	libshared.la
 
@@ -4153,6 +4170,10 @@ mtd_probe_SOURCES =  \
 	src/udev/mtd_probe/mtd_probe.h \
 	src/udev/mtd_probe/probe_smartmedia.c
 
+mtd_probe_CFLAGS = \
+	$(AM_CFLAGS)
+	-D UDEV_PROPAGATE_LOG
+
 dist_udevrules_DATA += \
 	rules/75-probe_mtd.rules
 

src/libudev/libudev.c

@@ -103,6 +103,8 @@ _public_ struct udev *udev_new(void) {
         }
         udev->refcount = 1;
 
+#ifdef UDEV_PROPAGATE_LOG
+
         f = fopen("/etc/udev/udev.conf", "re");
         if (f != NULL) {
                 char line[UTIL_LINE_SIZE];
@@ -178,6 +180,7 @@ _public_ struct udev *udev_new(void) {
                         }
                 }
         }
+#endif
 
         return udev;
 }