Linux: add lag support and bonding plugin for non-lag cases

[jbemmel]

• Refactor and reuse FRR logic for bond creation on Linux, both for the lag module and for the bonding plugin
• Support all the Linux bonding modes, split into:
  • lag module: [ 802.3ad, balance-rr, balance-xor, broadcast ]
  • bonding plugin: [ active-backup, balance-tlb, balance-alb ]

In all cases, bonding devices are created in initial such that any IP addresses can be assigned. Bond/lag members are then added in the respective lag module and bonding plugin

[ipspace]

A few minor details plus a major problem: we don't get the Linux static routes for the lab pools (they are supposed to point to the first data-plane interface), so the Linux host cannot reach anything but the adjacent router.

Fix the nits and I'll add the static routes part.

[ipspace]

Also, just wondering: how does netplan-based Ubuntu configuration work with handcrafted bond devices?

[jbemmel]

Also, just wondering: how does netplan-based Ubuntu configuration work with handcrafted bond devices?

It shows them as "unmanaged" just like the 'lo' device (odd to see that), but I agree it would be nicer to craft netplan configs where available. Will adjust

[ipspace]

Fix the nits and I'll add the static routes part.

Static route issue is tracked in #1641. I will probably go for a simple fix in the configuration template (that code is ancient)

[jbemmel]

Ready to add the static route bits