kernel: sysctl: Add sysctl_clearstr()

Introduce the sysctl_clearstr() function to clear string variables that
aren't readonly to a known state.

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 28 insertions, 0 deletions

diff --git a/sys/include/sys/sysctl.h b/sys/include/sys/sysctl.h
index d13b0f8..d258860 100644
--- a/sys/include/sys/sysctl.h
+++ b/sys/include/sys/sysctl.h
@@ -64,6 +64,7 @@ struct sysctl_entry {
 };
 
 scret_t sys_sysctl(struct syscall_args *scargs);
+int sysctl_clearstr(int name);
 #endif  /* _KERNEL */
 
 /*
diff --git a/sys/kern/kern_sysctl.c b/sys/kern/kern_sysctl.c
index 7679aa1..f5d8bdc 100644
--- a/sys/kern/kern_sysctl.c
+++ b/sys/kern/kern_sysctl.c
@@ -154,6 +154,33 @@ done:
     return retval;
 }
 
+/*
+ * Clear a writable sysctl string variable to the
+ * value of "(undef)"
+ *
+ * @name: Name to clear
+ */
+int
+sysctl_clearstr(int name)
+{
+    struct sysctl_args args;
+    char val[] = "(undef)";
+    int error;
+
+    args.name = &name;
+    args.nlen = 1;
+    args.oldlenp = 0;
+    args.oldp = NULL;
+    args.newp = val;
+    args.newlen = sizeof(val);
+
+    if ((error = sysctl(&args)) != 0) {
+        return error;
+    }
+
+    return 0;
+}
+
 int
 sysctl(struct sysctl_args *args)
 {