diff --git a/sys/kern/subr_sbuf.c b/sys/kern/subr_sbuf.c
--- a/sys/kern/subr_sbuf.c
+++ b/sys/kern/subr_sbuf.c
@@ -383,7 +383,7 @@
 /*
  * Call the drain and process the return.
  */
-static int
+int
 sbuf_drain(struct sbuf *s)
 {
 	int len;
diff --git a/sys/sys/sbuf.h b/sys/sys/sbuf.h
--- a/sys/sys/sbuf.h
+++ b/sys/sys/sbuf.h
@@ -95,6 +95,7 @@
 int		 sbuf_nl_terminate(struct sbuf *);
 int		 sbuf_putc(struct sbuf *, int);
 void		 sbuf_set_drain(struct sbuf *, sbuf_drain_func *, void *);
+int		 sbuf_drain(struct sbuf *);
 int		 sbuf_trim(struct sbuf *);
 int		 sbuf_error(const struct sbuf *);
 int		 sbuf_finish(struct sbuf *);