Add a drain function for struct sysctl_req, and use it for a variety of

handlers, some of which had to do awkward things to get a large enough
FIXEDLEN buffer.

Note that some sysctl handlers were explicitly outputting a trailing NUL
byte.  This behaviour was preserved, though it should not be necessary.

Reviewed by:	phk

1 files changed, 2 insertions, 2 deletions

diff --git a/sys/kern/subr_sbuf.c b/sys/kern/subr_sbuf.c
index d7b57a5..58964fb 100644
--- a/sys/kern/subr_sbuf.c
+++ b/sys/kern/subr_sbuf.c
@@ -305,8 +305,8 @@ sbuf_drain(struct sbuf *s)
 		SBUF_SETFLAG(s, SBUF_OVERFLOWED);
 		return (s->s_error);
 	}
-
-	KASSERT(len > 0, ("Drain must either error or work!"));
+	KASSERT(len > 0 && len <= s->s_len,
+	    ("Bad drain amount %d for sbuf %p", len, s));
 	s->s_len -= len;
 	/*
 	 * Fast path for the expected case where all the data was