meta-nvidia: nvl32-obmc: configure mctpd

mctpd is now built by its own recipe, separate from the mctp utilities,
so move its config file to a mctpd bbappend.

The mctpd.service that comes with mctp v2.6 runs the daemon as the
mctpd user [1], but without CAP_NET_RAW, which the kernel requires to
send MCTP control messages from an unprivileged process [2]. Without it
no endpoint can be assigned an EID, so grant it with a drop-in until
mctpd comes from a release that does.

[1] https://github.com/CodeConstruct/mctp/commit/4519db96948d1fca8e5dbd9e00c91fa515a46b86
[2] https://github.com/CodeConstruct/mctp/commit/bdd1627fa57dd53efcdfb09c399e8c25ca6d47cd

Tested: Built an image for the nvl32-obmc machine, flashed it to the
board and checked the result there:

```
# systemctl cat mctpd | grep -E "^# |Ambient"
# /usr/lib/systemd/system/mctpd.service
AmbientCapabilities=CAP_NET_BIND_SERVICE CAP_NET_ADMIN
# /usr/lib/systemd/system/mctpd.service.d/mctpd-net-raw.conf
AmbientCapabilities=CAP_NET_RAW

# grep -E "^Uid|CapEff" /proc/$(pidof mctpd)/status
Uid:    997     997     997     997
CapEff: 0000000000003000

# busctl tree --list au.com.codeconstruct.MCTP1 | grep -c endpoints/
23
```
1. mctpd runs as the mctpd user with CAP_NET_ADMIN and CAP_NET_RAW,
   and reads /etc/mctpd.conf from the mctpd package
2. Every MCTP over USB device and the endpoints behind its bridge are
   assigned an EID
3. Without the drop-in, AssignEndpoint fails with no packet sent on
   the interface, and no endpoint is created

Change-Id: I3b79cdc12d90674b2a30ccc692f10672a239f689
Signed-off-by: Ender Hsieh <andhsieh@nvidia.com>

0 files changed, 0 insertions, 0 deletions