add IPV6_RECVDSTPORT socket option, which enables us to get original

(= before divert) destination port of a UDP packet.  The way to use
this option is same as IP_RECVDSTPORT.

from UMEZAWA Takeshi
tweaks from jmc; ok henning bluhm

1 files changed, 13 insertions, 2 deletions

diff --git a/share/man/man4/ip6.4 b/share/man/man4/ip6.4
index dc54d77f0f8..e704a96de4a 100644
--- a/share/man/man4/ip6.4
+++ b/share/man/man4/ip6.4
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: ip6.4,v 1.26 2012/06/20 07:37:01 guenther Exp $
+.\"	$OpenBSD: ip6.4,v 1.27 2012/09/17 20:01:26 yasuoka Exp $
 .\"
 .\" Copyright (c) 1983, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -26,7 +26,7 @@
 .\" 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.
-.Dd $Mdocdate: June 20 2012 $
+.Dd $Mdocdate: September 17 2012 $
 .Dt IP6 4
 .Os
 .Sh NAME
@@ -421,6 +421,17 @@ Get or set the ESP encapsulation level.
 Get or set the
 .Xr ipcomp 4
 level.
+.It Dv IPV6_RECVDSTPORT Fa "int *"
+Get or set the status of whether the destination port for a UDP datagram
+will be provided as ancillary data along with the payload in subsequent 
+.Xr recvmsg 2
+calls.
+The information is stored as a single value of type
+.Vt u_int16_t
+in network byte order.
+.Pp
+Turning this option on will result in this socket getting cmsg data of
+type IPV6_RECVDSTPORT.
 .El
 .Pp
 The