man: add note to ip-macsec manual about necessary key management

The man page of ip-macsec and the existance of the tool makes it seem like
the user could just configure static keys once, and be done with it. That is
not the case. Some form or key management must be done in user space.

Add a note about that.

Signed-off-by: Thomas Haller <thaller@redhat.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

diff --git a/man/man8/ip-macsec.8 b/man/man8/ip-macsec.8
index 4fd8a5b6591aa27a9e64d53b09bef99ea74a77c4..2179b33683d5b1add0c2929918d4e9b56c36621b 100644 (file)
--- a/man/man8/ip-macsec.8
+++ b/man/man8/ip-macsec.8
@@ -102,8 +102,19 @@ type.
 .SS Display MACsec configuration
 .nf
 # ip macsec show
+
+.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
+with the same IV more than once. Instead, keys must be frequently regenerated and distibuted.
+This tool is thus mostly for debugging and testing, or in combination with a user-space application
+that reconfigures the keys. It is wrong to just configure the keys statically and assume them to work
+indefinitely. The suggested and standardized way for key management is 802.1X-2010, which is implemented
+by wpa_supplicant.
+
 .SH SEE ALSO
 .br
 .BR ip-link (8)
+.BR wpa_supplicant (8)
 .SH AUTHOR
 Sabrina Dubroca <sd@queasysnail.net>