T5722: Failover route add option onlink (backport #3313)

[mergify]

Change Summary

onlink pretend that the nexthop is directly attached to this link, even if it does not match any interface prefix.

Useful when the gateway is not in the same interface network

vyos@r4# sudo ip route add 192.0.2.111/32 via 10.20.30.0 dev eth0.10 metric 1 proto failover
Error: Nexthop has invalid gateway.
[edit]
vyos@r4#
[edit]
vyos@r4# sudo ip route add 192.0.2.111/32 via 10.20.30.0 dev eth0.10 onlink metric 1 proto failover
[edit]
vyos@r4#

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Migration from an old Vyatta component to vyos-1x, please link to related PR inside obsoleted component
• Other (please describe): New option some kind of bugfix

Related Task(s)

• https://vyos.dev/T5722

Related PR(s)

Component(s) name

routing, failover route

Proposed changes

How to test

set interfaces ethernet eth0 vif 10 address '10.20.30.1/32'
set protocols static route 10.20.30.0/32 interface eth0.10

set protocols failover route 192.0.2.11/32 next-hop 10.20.30.0 check target '10.20.30.0'
set protocols failover route 192.0.2.11/32 next-hop 10.20.30.0 check timeout '5'
set protocols failover route 192.0.2.11/32 next-hop 10.20.30.0 check type 'icmp'
set protocols failover route 192.0.2.11/32 next-hop 10.20.30.0 interface 'eth0.10'
set protocols failover route 192.0.2.11/32 next-hop 10.20.30.0 metric '1'
commit

Before, this route cannot be added due to gateway and interface not in the same network

Route 192.0.2.11/32 for protocol failover was not found
    [NEW_ROUTE_DETECTED] route: [192.0.2.11/32]
    [ CHECK-TARGET ]: [/usr/bin/ping -q 10.20.30.0 -I eth0.10 -n -c 2 -W 1] -- return-code [RC: 0]
    [ ADD ] -- ip route add 192.0.2.11/32 via 10.20.30.0 dev eth0.10 metric 1 proto failover
Error: Nexthop has invalid gateway. -- return-code [RC: 2] 10.20.30.0 dev eth0.10


vyos@r4# sudo ip route add 192.0.2.11/32 via 10.20.30.0 dev eth0.10 metric 1 proto failover
Error: Nexthop has invalid gateway.
[edit]
vyos@r4# 

The iproute2 option onlink fixes these cases

set protocols failover route 192.0.2.11/32 next-hop 10.20.30.0 onlink
commit

vyos@r4# run show ip route kernel 
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, F - PBR,
       f - OpenFabric,
       > - selected route, * - FIB route, q - queued, r - rejected, b - backup
       t - trapped, o - offload failure

K>* 192.0.2.11/32 [0/1] via 10.20.30.0, eth0.10 onlink, 00:00:03
[edit]
vyos@r4# 

Smoketest result

Checklist:

• I have read the CONTRIBUTING document
• I have linked this PR to one or more Phabricator Task(s)
• I have run the components SMOKETESTS if applicable
• My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly

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This is an automatic backport of pull request #3313 done by [Mergify](https://mergify.com).