sysctl_string
err = sysctl_string(oldp, oldlenp, newp, newlen, type, sizeof type);
error = sysctl_string(oldp, oldlenp, newp, newlen, newname, sizeof(newname));
err = sysctl_string(oldp, oldlenp, newp, newlen, policy, sizeof(policy));
int sysctl_string(void *, size_t *, void *, size_t, char *, size_t);
return (sysctl_string(oldp, oldlenp, newp, newlen,