diff --git a/lib/libcasper/services/cap_sysctl/cap_sysctl.3 b/lib/libcasper/services/cap_sysctl/cap_sysctl.3
index 0a7d009e1c3c..381315fcbdd7 100644
--- a/lib/libcasper/services/cap_sysctl/cap_sysctl.3
+++ b/lib/libcasper/services/cap_sysctl/cap_sysctl.3
@@ -1,192 +1,220 @@
 .\" Copyright (c) 2018 Mariusz Zaborski <oshogbo@FreeBSD.org>
 .\" All rights reserved.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
 .\" are met:
 .\" 1. Redistributions of source code must retain the above copyright
 .\"    notice, this list of conditions and the following disclaimer.
 .\" 2. Redistributions in binary form must reproduce the above copyright
 .\"    notice, this list of conditions and the following disclaimer in the
 .\"    documentation and/or other materials provided with the distribution.
 .\"
 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
 .\" $FreeBSD$
 .\"
-.Dd May 5, 2020
+.Dd December 1, 2022
 .Dt CAP_SYSCTL 3
 .Os
 .Sh NAME
 .Nm cap_sysctl
 .Nd "library for getting or setting system information in capability mode"
 .Sh LIBRARY
 .Lb libcap_sysctl
 .Sh SYNOPSIS
 .In libcasper.h
 .In casper/cap_sysctl.h
 .Ft int
 .Fn cap_sysctl "cap_channel_t *chan" "const int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "const void *newp" "size_t newlen"
 .Ft int
 .Fn cap_sysctlbyname "cap_channel_t *chan" "const char *name" "void *oldp" "size_t *oldlenp" "const void *newp" "size_t newlen"
 .Ft int
 .Fn cap_sysctlnametomib "cap_channel_t *chan" "const char *name" "int *mibp" "size_t *sizep"
-.Ft void *
+.Ft cap_sysctl_limit_t *
 .Fn cap_sysctl_limit_init "cap_channel_t *chan"
-.Ft void *
-.Fn cap_sysctl_limit_name "void *limit" "const char *name" "int flags"
-.Ft void *
-.Fn cap_sysctl_limit_mib "void *limit" "const int *mibp" "u_int miblen" "int flags"
+.Ft cap_sysctl_limit_t *
+.Fn cap_sysctl_limit_name "cap_sysctl_limit_t *limit" "const char *name" "int flags"
+.Ft cap_sysctl_limit_t *
+.Fn cap_sysctl_limit_mib "cap_sysctl_limit_t *limit" "const int *mibp" "u_int miblen" "int flags"
 .Ft int
-.Fn cap_sysctl_limit "void *limit"
+.Fn cap_sysctl_limit "cap_sysctl_limit_t *limit"
 .Sh DESCRIPTION
 The
 .Fn cap_sysctl ,
 .Fn cap_sysctlbyname
 and
 .Fn cap_sysctlnametomib
 functions are equivalent to
 .Xr sysctl 3 ,
 .Xr sysctlbyname 3
 and
 .Xr sysctlnametomib 3 ,
 except that they are implemented by the
 .Ql system.sysctl
 .Xr libcasper 3
 service and require a corresponding
 .Xr libcasper 3
 capability.
 .Sh LIMITS
 By default, the
 .Nm
 capability provides unrestricted access to the sysctl namespace.
 Applications typically only require access to a small number of sysctl
 variables; the
 .Fn cap_sysctl_limit
 interface can be used to restrict the sysctls that can be accessed using
 the
 .Nm
 capability.
 .Fn cap_sysctl_limit_init
 returns an opaque limit handle used to store a list of permitted sysctls
 and access rights.
 Rights are encoded using the following flags:
 .Pp
 .Bd -literal -offset indent -compact
 CAP_SYSCTL_READ		allow reads of the sysctl variable
 CAP_SYSCTL_WRITE        allow writes of the sysctl variable
 CAP_SYSCTL_RDWR         allow reads and writes of the sysctl variable
 CAP_RECURSIVE           permit access to any child of the sysctl variable
 .Ed
 .Pp
 The
 .Fn cap_sysctl_limit_name
 function adds the sysctl identified by
 .Ar name
 to the limit list, and
 .Fn cap_sysctl_limit_mib
 function adds the sysctl identified by
 .Ar mibp
 to the limit list.
 The access rights for the sysctl are specified in the
 .Ar flags
 parameter; at least one of
 .Dv CAP_SYSCTL_READ ,
 .Dv CAP_SYSCTL_WRITE
 and
 .Dv CAP_SYSCTL_RDWR
 must be specified.
 .Fn cap_sysctl_limit
 applies a set of sysctl limits to the capability, denying access to sysctl
 variables not belonging to the set.
+It consumes the limit handle.
+After either success or failure, the user must not access the handle again.
 .Pp
 Once a set of limits is applied, subsequent calls to
 .Fn cap_sysctl_limit
 will fail unless the new set is a subset of the current set.
 .Pp
 .Fn cap_sysctlnametomib
 will succeed so long as the named sysctl variable is present in the limit set,
 regardless of its access rights.
 When a sysctl variable name is added to a limit set, its MIB identifier is
 automatically added to the set.
 .Sh EXAMPLES
 The following example first opens a capability to casper, uses this
 capability to create the
 .Nm system.sysctl
 casper service, and then uses the
 .Nm
 capability to get the value of
 .Dv kern.trap_enotcap .
 .Bd -literal
 cap_channel_t *capcas, *capsysctl;
 const char *name = "kern.trap_enotcap";
 void *limit;
 size_t size;
 bool value;
 
 /* Open capability to Casper. */
 capcas = cap_init();
 if (capcas == NULL)
 	err(1, "Unable to contact Casper");
 
 /* Enter capability mode sandbox. */
 if (cap_enter() < 0 && errno != ENOSYS)
 	err(1, "Unable to enter capability mode");
 
 /* Use Casper capability to create capability to the system.sysctl service. */
 capsysctl = cap_service_open(capcas, "system.sysctl");
 if (capsysctl == NULL)
 	err(1, "Unable to open system.sysctl service");
 
 /* Close Casper capability, we don't need it anymore. */
 cap_close(capcas);
 
 /* Create limit for one MIB with read access only. */
 limit = cap_sysctl_limit_init(capsysctl);
 (void)cap_sysctl_limit_name(limit, name, CAP_SYSCTL_READ);
 
 /* Limit system.sysctl. */
 if (cap_sysctl_limit(limit) < 0)
 	err(1, "Unable to set limits");
 
 /* Fetch value. */
 size = sizeof(value);
 if (cap_sysctlbyname(capsysctl, name, &value, &size, NULL, 0) < 0)
 	err(1, "Unable to get value of sysctl");
 
 printf("The value of %s is %d.\\n", name, value);
 
 cap_close(capsysctl);
 .Ed
+.Sh RETURN VALUES
+.Fn cap_sysctl_limit_init
+will return a new limit handle on success or
+.Dv NULL
+on failure, and set
+.Va errno .
+.Fn cap_sysctl_limit_mib
+and
+.Fn cap_sysctl_limit_name
+will return the modified limit handle on success or
+.Dv NULL
+on failure and set
+.Va errno .
+After failure, the caller must not access the limit handle again.
+.Fn cap_sysctl_limit
+will return
+.Dv -1
+on failure and set
+.Va errno .
+.Fn cap_sysctl ,
+.Fn cap_sysctlbyname ,
+and
+.Fn cap_sysctlnametomib
+have the same return values as their non-capability-mode equivalents as
+documented in
+.Xr sysctl 3 .
 .Sh SEE ALSO
 .Xr cap_enter 2 ,
 .Xr err 3 ,
 .Xr sysctl 3 ,
 .Xr sysctlbyname 3 ,
 .Xr sysctlnametomib 3 ,
 .Xr capsicum 4 ,
 .Xr nv 9
 .Sh HISTORY
 The
 .Nm cap_sysctl
 service first appeared in
 .Fx 10.3 .
 .Sh AUTHORS
 The
 .Nm cap_sysctl
 service was implemented by
 .An Pawel Jakub Dawidek Aq Mt pawel@dawidek.net
 under sponsorship from the FreeBSD Foundation.
 .Pp
 This manual page was written by
 .An Mariusz Zaborski Aq Mt oshogbo@FreeBSD.org .