1 files changed, 20 insertions, 6 deletions
diff --git a/contrib/mandoc/mandocd.8 b/contrib/mandoc/mandocd.8
index d679deb1b9e4..aaf4e3dede70 100644
--- a/contrib/mandoc/mandocd.8
+++ b/contrib/mandoc/mandocd.8
@@ -1,6 +1,6 @@
-.\"	$Id: mandocd.8,v 1.3 2021/09/28 15:41:41 schwarze Exp $
+.\" $Id: mandocd.8,v 1.5 2025/06/30 15:07:38 schwarze Exp $
 .\"
-.\" Copyright (c) 2017 Ingo Schwarze <schwarze@openbsd.org>
+.\" Copyright (c) 2017, 2025 Ingo Schwarze <schwarze@openbsd.org>
 .\"
 .\" Permission to use, copy, modify, and distribute this software for any
 .\" purpose with or without fee is hereby granted, provided that the above
@@ -14,7 +14,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: September 28 2021 $
+.Dd $Mdocdate: June 30 2025 $
 .Dt MANDOCD 8
 .Os
 .Sh NAME
@@ -78,6 +78,19 @@ or
 input, the second one for formatted output, and the third one
 for error output.
 .Pp
+After accepting each message,
+.Nm
+replies with a one-byte message of its own,
+such that the parent process can keep track of how many messages
+.Nm
+has already accepted and how many file descriptors
+consequently are still in flight, such that the parent process
+can limit the number of file descriptors in flight at any given time
+in order to prevent
+.Er EMFILE
+failure of
+.Xr sendmsg 2 .
+.Pp
 The options are as follows:
 .Bl -tag -width Ds
 .It Fl I Cm os Ns = Ns Ar name
@@ -112,7 +125,7 @@ Other output options are not supported.
 After exhausting one input file descriptor, all three file descriptors
 are closed before reading the next dummy byte and control message.
 .Pp
-When a zero-byte message is read, when the
+When a zero-byte message or a misformatted message is read, when the
 .Ar socket_fd
 is closed by the parent process,
 or when an error occurs,
@@ -131,9 +144,10 @@ missing, invalid, or excessive
 .Xr exec 3
 arguments
 .It
+communication failure with the parent, for example failure in
 .Xr recvmsg 2
-failure, for example due to
-.Er EMSGSIZE
+or
+.Xr send 2
 .It
 missing or unexpected control data, in particular a
 .Fa cmsg_level