Index: sys/net/iflib.h
===================================================================
--- sys/net/iflib.h
+++ sys/net/iflib.h
@@ -248,7 +248,7 @@
 
 	/* fields necessary for probe */
 	pci_vendor_info_t *isc_vendor_info;
-	char *isc_driver_version;
+	const char *isc_driver_version;
 	/* optional function to transform the read values to match the table*/
 	void (*isc_parse_devinfo) (uint16_t *device_id, uint16_t *subvendor_id,
 				   uint16_t *subdevice_id, uint16_t *rev_id);
Index: sys/net/iflib.c
===================================================================
--- sys/net/iflib.c
+++ sys/net/iflib.c
@@ -6230,8 +6230,8 @@
 						      CTLFLAG_RD, NULL, "IFLIB fields");
 	oid_list = SYSCTL_CHILDREN(node);
 
-	SYSCTL_ADD_STRING(ctx_list, oid_list, OID_AUTO, "driver_version",
-		       CTLFLAG_RD, ctx->ifc_sctx->isc_driver_version, 0,
+	SYSCTL_ADD_CONST_STRING(ctx_list, oid_list, OID_AUTO, "driver_version",
+		       CTLFLAG_RD, ctx->ifc_sctx->isc_driver_version,
 		       "driver version");
 
 	SYSCTL_ADD_U16(ctx_list, oid_list, OID_AUTO, "override_ntxqs",
Index: sys/sys/sysctl.h
===================================================================
--- sys/sys/sysctl.h
+++ sys/sys/sysctl.h
@@ -354,6 +354,25 @@
 	    NULL); \
 })
 
+/* Oid for a constant '\0' terminated string. */
+#define	SYSCTL_CONST_STRING(parent, nbr, name, access, arg, descr)	\
+	SYSCTL_OID(parent, nbr, name, CTLTYPE_STRING|(access),		\
+	    __DECONST(char *, arg), 0, sysctl_handle_string, "A", descr); \
+	CTASSERT(!(access & CTLFLAG_WR));				\
+	CTASSERT(((access) & CTLTYPE) == 0 ||				\
+	    ((access) & SYSCTL_CT_ASSERT_MASK) == CTLTYPE_STRING)
+
+#define	SYSCTL_ADD_CONST_STRING(ctx, parent, nbr, name, access, arg, descr) \
+({									\
+	char *__arg = __DECONST(char *, arg);				\
+	CTASSERT(!(access & CTLFLAG_WR));				\
+	CTASSERT(((access) & CTLTYPE) == 0 ||				\
+	    ((access) & SYSCTL_CT_ASSERT_MASK) == CTLTYPE_STRING);	\
+	sysctl_add_oid(ctx, parent, nbr, name, CTLTYPE_STRING|(access),	\
+	    __arg, 0, sysctl_handle_string, "A", __DESCR(descr),	\
+	    NULL); \
+})
+
 /* Oid for a bool.  If ptr is NULL, val is returned. */
 #define	SYSCTL_NULL_BOOL_PTR ((bool *)NULL)
 #define	SYSCTL_BOOL(parent, nbr, name, access, ptr, val, descr)	\