m/n/core/network: implement LLDP transmission

Implements simple LLDP transmission-only support for Monogon OS. It
advertises enough to do topology discovery through LLDP. Currently it
supports MAC address, interface name, node name and product
name/version. More information can be added in the future.

Tested using Wireshark on launch-cluster node/switch traffic.

Change-Id: If5777bc042ef87bd8d26c548324c6de6f14f7270
Reviewed-on: https://review.monogon.dev/c/monogon/+/4282
Tested-by: Jenkins CI
Reviewed-by: Tim Windelschmidt <tim@monogon.tech>
diff --git a/go.sum b/go.sum
index 0be3b8e..09387ae 100644
--- a/go.sum
+++ b/go.sum
@@ -2429,6 +2429,8 @@
 github.com/mdlayher/genetlink v1.3.2/go.mod h1:tcC3pkCrPUGIKKsCsp0B3AdaaKuHtaxoJRz3cc+528o=
 github.com/mdlayher/kobject v0.0.0-20200520190114-19ca17470d7d h1:JmrZTpS0GAyMV4ZQVVH/AS0Y6r2PbnYNSRUuRX+HOLA=
 github.com/mdlayher/kobject v0.0.0-20200520190114-19ca17470d7d/go.mod h1:+SexPO1ZvdbbWUdUnyXEWv3+4NwHZjKhxOmQqHY4Pqc=
+github.com/mdlayher/lldp v0.0.0-20150915211757-afd9f83164c5 h1:i4JJtLb5iDVsncU7splD9ZCQXvxN13tGDUWihfKOq18=
+github.com/mdlayher/lldp v0.0.0-20150915211757-afd9f83164c5/go.mod h1:IZAsRpRUv/4B6NhGzofHK/+I+N31NTUz/hrEm4ssUwA=
 github.com/mdlayher/netlink v0.0.0-20190409211403-11939a169225/go.mod h1:eQB3mZE4aiYnlUsyGGCOpPETfdQq4Jhsgf1fk3cwQaA=
 github.com/mdlayher/netlink v0.0.0-20190516121005-0087c778e469/go.mod h1:gOrA34zDL0K3RsACQe54bDYLF/CeFspQ9m5DOycycQ8=
 github.com/mdlayher/netlink v0.0.0-20190828143259-340058475d09/go.mod h1:KxeJAFOFLG6AjpyDkQ/iIhxygIUKD+vcwqcnu43w/+M=