The 08/21/2019 09:20, Igor Russkikh wrote:

quoted

Talking about packet numbers, can you describe how PN exhaustion is
handled?  I couldn't find much about packet numbers at all in the
driver patches (I hope the hw doesn't wrap around from 2^32-1 to 0 on
the same SA).  At some point userspace needs to know that we're
getting close to 2^32 and that it's time to re-key.  Since the whole
TX path of the software implementation is bypassed, it looks like the
PN (as far as drivers/net/macsec.c is concerned) never increases, so
userspace can't know when to negotiate a new SA.

I think there should be driver specific implementation of this functionality.
As an example, our macsec HW issues an interrupt towards the host to indicate
PN threshold has reached and it's time for userspace to change the keys.

In contrast, current SW macsec implementation just stops this SA/secy.

quoted

I don't see how this implementation handles non-macsec traffic (on TX,
that would be packets sent directly through the real interface, for
example by wpa_supplicant - on RX, incoming MKA traffic for
wpa_supplicant). Unless I missed something, incoming MKA traffic will
end up on the macsec interface as well as the lower interface (not
entirely critical, as long as wpa_supplicant can grab it on the lower
device, but not consistent with the software implementation). How does
the driver distinguish traffic that should pass through unmodified
from traffic that the HW needs to encapsulate and encrypt?

I can comment on our HW engine - where it has special bypass rules
for configured ethertypes. This way macsec engine skips encryption on TX and
passes in RX unencrypted for the selected control packets.

In our case it is a TCAM which can look at various fields (including ethertype),
but is sounds like we have a vary similar design.

But thats true, realdev driver is hard to distinguish encrypted/unencrypted
packets. In case realdev should make a decision where to put RX packet,
it only may do some heuristic (since after macsec decription all the
macsec related info is dropped. Thats true at least for our HW implementation).

Same for ours.

quoted

If you look at IPsec offloading, the networking stack builds up the
ESP header, and passes the unencrypted data down to the driver. I'm
wondering if the same would be possible with MACsec offloading: the
macsec virtual interface adds the header (and maybe a dummy ICV), and
then the HW does the encryption. In case of HW that needs to add the
sectag itself, the driver would first strip the headers that the stack
created. On receive, the driver would recreate a sectag and the macsec
interface would just skip all verification (decrypt, PN).

I don't think this way is good, as driver have to do per packet header mangling.
That'll harm linerate performance heavily.

Agree, and it will also prevent MACsec offload in offloaded bridge devices.

/Allan