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bgpd: fix ipv4-mapped ipv6 use cases #17019

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bgpd: fix ipv4-mapped ipv6 use cases #17019

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Commits on Oct 7, 2024

  1. topotests: add an ebgp 6vpe test 

    This test uses the connected ipv4 mapped ipv6 prefix
to resolve the received BGP routes.

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
Signed-off-by: Philippe Guibert <philippe.guibert@6wind.com>
Signed-off-by: François Dumontet <francois.dumontet@6wind.com>
    @pguibert6WIND @louis-6wind
    pguibert6WIND authored and louis-6wind committed Oct 7, 2024
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  2. bgpd: optimize bgp_interface_address_add 

    Move common checks outside of the loop.

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
    @louis-6wind
    louis-6wind committed Oct 7, 2024
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  3. bgpd: reduce bgp_interface_address_add indentation 

    Reduce bgp_interface_address_add indentation

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
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    louis-6wind committed Oct 7, 2024
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  4. bgpd: log new ipv6 global in bgp_interface_address_add 

    Log new IPv6 global address in bgp_interface_address_add

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
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    louis-6wind committed Oct 7, 2024
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  5. bgpd: fix sending ipv6 local nexthop if global present 

    bgpd keeps on advertising IPv6 prefixes with a IPv6 link-local nexthop
after a valid IPv6 global appears.

At bgpd startup, the IPv6 global is announced by zebra after the
link-local. Only the link-local is advertised. Clearing the BGP sessions
make the global to to be announced.

Update the nexthops with the global IPv6 when available.

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
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  6. topotests: add bgp_nexthop_mp_ipv4_6 test 

    Add bgp_nexthop_mp_ipv4_6 topotest to test to nexhop value with
MP-BGP IPv4 and IPv6 on IPv4 peering. The test has route-reflector,
route-server, iBGP and eBGP peers.

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
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    louis-6wind committed Oct 7, 2024
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  7. bgpd: optimize bgp_interface_address_del 

    Move common checks outside of the loop.

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
    @louis-6wind
    louis-6wind committed Oct 7, 2024
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  8. bgpd: fix removing ipv6 global nexhop 

    When the IPv6 global is removed on an interface towards a peer, the
IPv6 nexthop global that is sent is a IPv4-mapped IPv6 address. It
should be the link-local.

At removal, replace the global by the next global address or the
link-local as last resort.

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
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  9. bgpd: fix "used" json key on link-local nexthop 

    When a peer has no IPv6 global address to send as nexthop, it sends the
IPv6 link-local instead as global. "show bgp ipv6 json" displays the
same address in global and link-local scopes.

> "nexthops": [
>   {
>     "ip": "fe80::a495:38ff:fea6:6ea3",
>     "afi": "ipv6",
>     "scope": "global",
>     "used": true
>   },
>   {
>     "ip": "fe80::a495:38ff:fea6:6ea3",
>     "afi": "ipv6",
>     "scope": "link-local"
>   }
> ]

However, "used" key is set on the global nexthop but not in link-local.
It is correct but it makes difficult to test JSON to expect the usage of
a link-local. The contrary is also correct.

Set "used" key on the link-local nexhop instead to facilitate the tests.

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
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    louis-6wind committed Oct 7, 2024
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  10. tests: ipv6 global removal in bgp_nexthop_mp_ipv4_6 

    Test ipv6 global removal in bgp_nexthop_mp_ipv4_6

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
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    louis-6wind committed Oct 7, 2024
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  11. bgpd: set ipv4-mapped ipv6 for ipv4 with ipv6 nexthop 

    The code was expected that no IPv6 global address was present but the
previous commit was replacing nexthop.v6global by the link-local address
instead of un-setting it in case of removal of the IPv6 global.

Set also ipv4-mapped ipv6 address as nexthop when a link-local is found
and it is an ipv4 prefix over ipv6 nexthop.

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
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    louis-6wind committed Oct 7, 2024
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  12. bgpd: prefer link-local to a ipv4-mapped ipv6 global 

    When a peer sends an IPv4-mapped IPv6 global and a IPv6 link-local
nexthop, prefer the link-local unless a route-map tells to use the
global.

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
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    louis-6wind committed Oct 7, 2024
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  13. topotests: update bgp_vrf_leaking_5549_routes 

    Before the patch-set, ce1 was sending an IPv6 Link-local as global and
link-local nexthop to pe1.

Set bgp_vrf_leaking_5549_routes in accordance with the previous fixes.

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
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    louis-6wind committed Oct 7, 2024
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  14. bgpd: fix ipv4-mapped ipv6 for ipv6 over ipv4 peer 

    When IPv6 prefixes are sent over an IPv4 session, the UPDATE is sent
with a link-local nexthop as global nexthop instead of a IPv4-mapped
IPv6 address. If the peer interface has no IPv6 address, routes are
not installed.

Seen with bgp_nexthop_mp_ipv4_6 topotests on step2:

> root@r2:/# vtysh -c 'show bgp ipv6 fd00:100::/64 json' | jq .
> {
>   "prefix": "fd00:100::/64",
>   "paths": [
>     {
>       "nexthops": [
>         {
>           "ip": "fe80::449a:f8ff:fe67:1f93",
>           "hostname": "r1",
>           "afi": "ipv6",
>           "scope": "global",
>           "metric": 0,
>           "accessible": true
>         },
>         {
>           "ip": "fe80::449a:f8ff:fe67:1f93",
>           "hostname": "r1",
>           "afi": "ipv6",
>           "scope": "link-local",
>           "accessible": true,
>           "used": true
>         }
>       ],
>     }
>   ]
> }

Now:

> root@r2:/# vtysh -c 'show bgp ipv6 fd00:100::/64 json' | jq .
> {
>   "prefix": "fd00:100::/64",
>   "paths": [
>       "nexthops": [
>         {
>           "ip": "::ffff:172.16.0.1",
>           "hostname": "r1",
>           "afi": "ipv6",
>           "scope": "global",
>           "metric": 0,
>           "accessible": true
>         },
>         {
>           "ip": "fe80::3842:28ff:fe90:f815",
>           "hostname": "r1",
>           "afi": "ipv6",
>           "scope": "link-local",
>           "accessible": true,
>           "used": true
>         }
>       ],
>     }
>   ]
> }

Note that the link-local is still preferred over the global address.

Fixes: 25995695f5 ("bgpd: set ipv4-mapped ipv6 for ipv4 with ipv6 nexthop")
Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
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    louis-6wind committed Oct 7, 2024
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  15. bgpd: fix nexthop resolution of ipv4-mapped ipv6 

    Fix nexthop resolution of ipv4-mapped ipv6 nexthop addresses.

Fixes: 5dd731a ("bgpd: prefer link-local to a ipv4-mapped ipv6 global")
Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
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    louis-6wind committed Oct 7, 2024
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  16. bgpd: replace ipv4-mapped ipv6 at update forwarding 

    Replace IPv4-mapped IPv6 at update forwarding because the peer may not
be able to create a route with the IPv4-mapped IPv6.

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
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  17. topotests: bgp_nexthop_mp_ipv4_6, test ipv4-mapped 

    Test that a IPv4-mapped IPv6 is sent from a peer that has no global IPv6
address.

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
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  18. bgpd: Do not use mapped IPv4/IPv6 addresses for unnumbered peering 

    Before:

```
router bgp 4283023031
 bgp router-id 100.83.23.31
 neighbor leafs peer-group
 neighbor leafs remote-as external
 neighbor eth1 interface peer-group leafs
 !
 address-family ipv4 unicast
  network 100.83.23.31/32
 exit-address-family
 !
exit
```

```
leaf2# show ip bgp 100.83.23.31/32
…
  4283023031
    ::ffff:6453:171f (inaccessible) from node31-h23-osl3(swp32) (100.83.23.31)
    (fe80::a6bf:1ff:fe2d:689a) (used)
      Origin IGP, metric 0, invalid, external
      Last update: Tue Aug 13 08:36:46 2024
```

Fixes: fc5a738 ("bgpd: set ipv4-mapped ipv6 for ipv4 with ipv6 nexthop")

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>
    @ton31337 @louis-6wind
    ton31337 authored and louis-6wind committed Oct 7, 2024
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