bgpd: fix wrong automatic router-id use

[anlancs]

Only considers the automatic rd scenario without a bgp connection and without configuring any rd in the command line.

This automatic rd is created and used for bgp at this case, but it should not be used for vpn if rd vpn export is set in command line. And both IPv4 and IPv6 family also have this issue.

With the configuration:

router bgp 88 vrf vrf1
 neighbor 3.3.3.3 remote-as 99
 !
 address-family ipv4 unicast
  rd vpn export 4:4
  rt vpn export 4:4
  export vpn
  import vpn
 exit-address-family
exit

At the beginning, there was no address in vrf1, then set address 1.1.1.1/24. The running is changed:

router bgp 88 vrf xx
 neighbor 3.3.3.3 remote-as 99
 !
 address-family ipv4 unicast
  rd vpn export 4:4
  rt vpn export 1.1.1.1:4 <--
  export vpn
  import vpn
 exit-address-family

[mjstapp]

I'm a little confused: the example in the description makes it appear that the config changes if environmental/OS changes occur. isn't that the bug?

[ton31337]

LGTM

[ton31337]

@Mergifyio backport stable/10.4 stable/10.3 stable/10.2

[mergify]

backport stable/10.4 stable/10.3 stable/10.2

🟠 Waiting for conditions to match

• merged [📌 backport requirement]

[ton31337]

Without reading the code (not the changes) => don't we miss to do the leaking stuff (just in case), except just handling configuration issue?

[anlancs]

Without reading the code (not the changes) => don't we miss to do the leaking stuff (just in case), except just handling configuration issue?

I have tested it. In this situation, the vpn doesn't work for the magic/unknown rt.
Unless the magic rt is manually configured on the other bgp neighbor:

rt vpn import 1.1.1.1:4

[anlancs]

I'm a little confused: the example in the description makes it appear that the config changes if environmental/OS changes occur. isn't that the bug?

not a bug, but it looks a little complicated: #2929

[mjstapp]

you referenced an old PR about router-id zapi messaging from zebra. but ... this isn't about the router-id, is it? you're not proposing changes to router-id here are you?

I'm a little confused: the example in the description makes it appear that the config changes if environmental/OS changes occur. isn't that the bug?

not a bug, but it looks a little complicated: #2929

[anlancs]

you referenced an old PR about router-id zapi messaging from zebra. but ... this isn't about the router-id, is it? you're not proposing changes to router-id here are you?

I'm a little confused: the example in the description makes it appear that the config changes if environmental/OS changes occur. isn't that the bug?

not a bug, but it looks a little complicated: #2929

There is no change with router-id here, just avoid the environment/OS changes the running config and vpn function.
If no router-id, vpn will use the automatic router-id created by ipv4 address with zebra's ZEBRA_ROUTER_ID_UPDATE.

[riw777]

looks good