batman-adv: drop batman-adv specific version

Bumping the version number on the first pull request after each merge
window was deemed inappropriate for an in-tree component. The version
number carries little meaningful information in the context of the Linux
kernel release model, where stable and distribution might all carry
slightly different patches (without any change to the batman-adv version).

Instead, expose a UTS_RELEASE-based string to consumers of the netlink and
ethtool interfaces. To avoid recompilation for each (re)generate of
generated/utsrelease.h, init_utsname()->release is used in code which can
dynamically retrieve the version string. The MODULE_VERSION is moved to a
separate file because it doesn't support dynamic retrieval of the version
string (but constant "at compile time" string) and it is required for the
/sys/module/batman_adv/version. The latter is unfortunately still required
by userspace tools.

Link: https://lore.kernel.org/r/20210203163302.13e8a2a7@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com
Link: https://lore.kernel.org/r/YnfjtpuAaH+Zkf9S@unreal
Link: https://lore.kernel.org/r/Y9faTA0rNSXg%2FsLD@nanopsycho
Signed-off-by: Sven Eckelmann <sven@narfation.org>

6 files changed, 19 insertions, 8 deletions

diff --git a/net/batman-adv/Makefile b/net/batman-adv/Makefile
index d3c4d4143c14..5d7456f1240d 100644
--- a/net/batman-adv/Makefile
+++ b/net/batman-adv/Makefile
@@ -30,5 +30,6 @@ batman-adv-$(CONFIG_BATMAN_ADV_TRACING) += trace.o
 batman-adv-y += tp_meter.o
 batman-adv-y += translation-table.o
 batman-adv-y += tvlv.o
+batman-adv-y += version.o
 
 CFLAGS_trace.o := -I$(src)
diff --git a/net/batman-adv/main.c b/net/batman-adv/main.c
index a4d33ee0fda5..82bba3489378 100644
--- a/net/batman-adv/main.c
+++ b/net/batman-adv/main.c
@@ -33,6 +33,7 @@
 #include <linux/sprintf.h>
 #include <linux/stddef.h>
 #include <linux/string.h>
+#include <linux/utsname.h>
 #include <linux/workqueue.h>
 #include <net/dsfield.h>
 #include <net/genetlink.h>
@@ -112,7 +113,7 @@ static int __init batadv_init(void)
 	batadv_netlink_register();
 
 	pr_info("B.A.T.M.A.N. advanced %s (compatibility version %i) loaded\n",
-		BATADV_SOURCE_VERSION, BATADV_COMPAT_VERSION);
+		init_utsname()->release, BATADV_COMPAT_VERSION);
 
 	return 0;
 
@@ -684,6 +685,5 @@ MODULE_LICENSE("GPL");
 
 MODULE_AUTHOR(BATADV_DRIVER_AUTHOR);
 MODULE_DESCRIPTION(BATADV_DRIVER_DESC);
-MODULE_VERSION(BATADV_SOURCE_VERSION);
 MODULE_ALIAS_RTNL_LINK("batadv");
 MODULE_ALIAS_GENL_FAMILY(BATADV_NL_NAME);
diff --git a/net/batman-adv/main.h b/net/batman-adv/main.h
index af230b017bc1..f68fc8b7239c 100644
--- a/net/batman-adv/main.h
+++ b/net/batman-adv/main.h
@@ -12,10 +12,6 @@
 #define BATADV_DRIVER_DESC   "B.A.T.M.A.N. advanced"
 #define BATADV_DRIVER_DEVICE "batman-adv"
 
-#ifndef BATADV_SOURCE_VERSION
-#define BATADV_SOURCE_VERSION "2025.5"
-#endif
-
 /* B.A.T.M.A.N. parameters */
 
 #define BATADV_TQ_MAX_VALUE 255
diff --git a/net/batman-adv/mesh-interface.c b/net/batman-adv/mesh-interface.c
index e7aa45bc6b7a..f25b86102957 100644
--- a/net/batman-adv/mesh-interface.c
+++ b/net/batman-adv/mesh-interface.c
@@ -36,6 +36,7 @@
 #include <linux/stddef.h>
 #include <linux/string.h>
 #include <linux/types.h>
+#include <linux/utsname.h>
 #include <net/netlink.h>
 #include <net/rtnetlink.h>
 #include <uapi/linux/batadv_packet.h>
@@ -892,7 +893,7 @@ static void batadv_get_drvinfo(struct net_device *dev,
 			       struct ethtool_drvinfo *info)
 {
 	strscpy(info->driver, "B.A.T.M.A.N. advanced", sizeof(info->driver));
-	strscpy(info->version, BATADV_SOURCE_VERSION, sizeof(info->version));
+	strscpy(info->version, init_utsname()->release, sizeof(info->version));
 	strscpy(info->fw_version, "N/A", sizeof(info->fw_version));
 	strscpy(info->bus_info, "batman", sizeof(info->bus_info));
 }
diff --git a/net/batman-adv/netlink.c b/net/batman-adv/netlink.c
index 78c651f634cd..b30f018740fc 100644
--- a/net/batman-adv/netlink.c
+++ b/net/batman-adv/netlink.c
@@ -28,6 +28,7 @@
 #include <linux/skbuff.h>
 #include <linux/stddef.h>
 #include <linux/types.h>
+#include <linux/utsname.h>
 #include <net/genetlink.h>
 #include <net/net_namespace.h>
 #include <net/netlink.h>
@@ -233,7 +234,7 @@ static int batadv_netlink_mesh_fill(struct sk_buff *msg,
 	if (!hdr)
 		return -ENOBUFS;
 
-	if (nla_put_string(msg, BATADV_ATTR_VERSION, BATADV_SOURCE_VERSION) ||
+	if (nla_put_string(msg, BATADV_ATTR_VERSION, init_utsname()->release) ||
 	    nla_put_string(msg, BATADV_ATTR_ALGO_NAME,
 			   bat_priv->algo_ops->name) ||
 	    nla_put_u32(msg, BATADV_ATTR_MESH_IFINDEX, mesh_iface->ifindex) ||
diff --git a/net/batman-adv/version.c b/net/batman-adv/version.c
new file mode 100644
index 000000000000..2b8006fe85b5
--- /dev/null
+++ b/net/batman-adv/version.c
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <generated/utsrelease.h>
+#include <linux/module.h>
+
+/* WARNING userspace tools like batctl were relying on
+ * /sys/module/batman_adv/version to check if the module was loaded. If it
+ * isn't present, they usually error out before finishing setup of the batadv
+ * interface. It should be kept until it is unlikely that there are active
+ * installations of these "broken" versions of these tools with recent kernels.
+ */
+MODULE_VERSION(UTS_RELEASE);