From a7a39f89b58da3eb939f7233c23f8eb225826d48 Mon Sep 17 00:00:00 2001
From: Phil Sutter <psutter@redhat.com>
Date: Wed, 30 Mar 2016 16:51:09 +0200
Subject: [PATCH] man: tc-mirred.8: Reword man page a bit, add generic mirror
example
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1275426
Upstream Status: iproute2.git commit 26df2953a5c34
commit 26df2953a5c34fe03986cbf3466321fd8a3af1c5
Author: Phil Sutter <phil@nwl.cc>
Date: Tue Mar 22 15:48:35 2016 +0100
man: tc-mirred.8: Reword man page a bit, add generic mirror example
Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
man/man8/tc-mirred.8 | 26 +++++++++++++++++++-------
1 file changed, 19 insertions(+), 7 deletions(-)
diff --git a/man/man8/tc-mirred.8 b/man/man8/tc-mirred.8
index 52d98bc..bba96e0 100644
--- a/man/man8/tc-mirred.8
+++ b/man/man8/tc-mirred.8
@@ -21,11 +21,9 @@ mirred - mirror/redirect action
.SH DESCRIPTION
The
.B mirred
-action allows to redirect or mirror packets to another network interface on the
-same system. It is typically used in combination with the
-.B ifb
-pseudo device to create a shrared instance where QoS happens, but serves well
-for debugging or monitoring purposes, too.
+action allows packet mirroring (copying) or redirecting (stealing) the packet it
+receives. Mirroring is what is sometimes referred to as Switch Port Analyzer
+(SPAN) and is commonly used to analyze and/or debug flows.
.SH OPTIONS
.TP
.B ingress
@@ -67,9 +65,23 @@ debugging purposes:
.EE
.RE
-Use an
+Mirror all incoming ICMP packets on eth0 to a dummy interface for examination
+with e.g. tcpdump:
+
+.RS
+.EX
+# ip link add dummy0 type dummy
+# ip link set dummy0 up
+# tc qdisc add dev eth0 handle ffff: ingress
+# tc filter add dev eth0 parent ffff: protocol ip \\
+ u32 match ip protocol 1 0xff \\
+ action mirred egress mirror dev dummy0
+.EE
+.RE
+
+Using an
.B ifb
-interface to send ingress traffic on eth0 through an instance of
+interface, it is possible to send ingress traffic through an instance of
.BR sfq :
.RS
--
1.8.3.1