[PATCH main v3 2/2] macsec: add user manual description for extended packet number feature

[Emeel Hakim <ehakim@nvidia.com>]

Update the user manual describing how to use extended packet number (XPN)
feature for macsec. As part of configuring XPN, providing ssci and salt is
required hence update user manual on  how to provide the above as part of
the ip macsec command.

Signed-off-by: Emeel Hakim <ehakim@nvidia.com>
---
V1->V2: 
- Updated documentation.

V2->V3:

 man/man8/ip-macsec.8 | 52 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/man/man8/ip-macsec.8 b/man/man8/ip-macsec.8
index bb816157..991a775a 100644
--- a/man/man8/ip-macsec.8
+++ b/man/man8/ip-macsec.8
@@ -19,6 +19,7 @@ ip-macsec \- MACsec device configuration
 .BR scb " { " on " | " off " } ] ["
 .BR protect " { " on " | " off " } ] ["
 .BR replay " { " on " | " off " } ] ["
+.BR xpn " { " on " | " off " } ] ["
 .BI window " WINDOW"
 ] [
 .BR validate " { " strict " | " check " | " disabled " } ] ["
@@ -63,7 +64,13 @@ ip-macsec \- MACsec device configuration
 
 .IR OPTS " := [ "
 .BR pn " { "
-.IR 1..2^32-1 " } ] ["
+.IR 1..2^32-1 " } |"
+.BR xpn " { "
+.IR 1..2^64-1 " } ] ["
+.B salt
+.IR SALT " ] ["
+.B ssci
+.IR <u32> " ] ["
 .BR on " | " off " ]"
 .br
 .IR SCI " := { "
@@ -75,6 +82,8 @@ ip-macsec \- MACsec device configuration
 }
 .br
 .IR PORT " := { " 1..2^16-1 " } "
+.br
+.IR SALT " := 96-bit hex string "
 
 
 .SH DESCRIPTION
@@ -116,6 +125,29 @@ type.
 .nf
 # ip link add link eth0 macsec0 type macsec port 11 encrypt on offload mac
 
+.SH EXTENDED PACKET NUMBER EXAMPLES
+.PP
+.SS Create a MACsec device on link eth0 with enabled extended packet number (offload is disabled by default)
+.nf
+# ip link add link eth0 macsec0 type macsec port 11 encrypt on xpn on
+.PP
+.SS Configure a secure association on that device
+.nf
+# ip macsec add macsec0 tx sa 0 xpn 1024 on salt 838383838383838383838383 ssci 123 key 01 81818181818181818181818181818181
+.PP
+.SS Configure a receive channel
+.nf
+# ip macsec add macsec0 rx port 11 address c6:19:52:8f:e6:a0
+.PP
+.SS Configure a receive association
+.nf
+# ip macsec add macsec0 rx port 11 address c6:19:52:8f:e6:a0 sa 0 xpn 1 on salt 838383838383838383838383 ssci 123 key 00 82828282828282828282828282828282
+.PP
+.SS Display MACsec configuration
+.nf
+# ip macsec show
+.PP
+
 .SH NOTES
 This tool can be used to configure the 802.1AE keys of the interface. Note that 802.1AE uses GCM-AES
 with a initialization vector (IV) derived from the packet number. The same key must not be used
@@ -125,6 +157,24 @@ that reconfigures the keys. It is wrong to just configure the keys statically an
 indefinitely. The suggested and standardized way for key management is 802.1X-2010, which is implemented
 by wpa_supplicant.
 
+.SH EXTENDED PACKET NUMBER NOTES
+Passing flag
+.B xpn
+to
+.B ip link add
+command using the
+.I macsec
+type requires using the keyword
+.B 'xpn'
+instead of
+.B 'pn'
+in addition to providing a salt using the
+.B 'salt'
+keyword when using the
+.B ip macsec
+command.
+
+
 .SH SEE ALSO
 .br
 .BR ip-link (8)
-- 
2.21.3