bgpd: fix MPLS labels in adj-RIB-in and adj-RIB-out #15205
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Isn't this the second time this has been attempted to be upstreamed? What was the original PR? |
The original one is from Philippe's account. I am refreshing it but I cannot work from his account. I am refreshing it when it is ready, it will be pushed to the original one |
Move the BGP_MAX_LABEL value in the bgp_label.h header. Signed-off-by: Philippe Guibert <philippe.guibert@6wind.com> Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
After modifying the "label vpn export value", the vpn label information
of the VRF is not updated to the peers.
The below configuration example illustrates the 192.168.0.0/24 BGP
update sent to the 192.0.2.2 peer, with the 222 label value.
> router bgp 65500
> [..]
> neighbor 192.0.2.2 remote-as 65501
> address-family ipv4-vpn
> neighbor 192.0.2.2 activate
> exit-address-family
> exit
> router bgp 65500 vrf vrf2
> bgp router-id 192.0.1.1
> address-family ipv4 unicast
> network 192.168.0.0/24
> label vpn export 222
> rd vpn export 444:444
> rt vpn both 53:100
> export vpn
> import vpn
> exit-address-family
Changing the value of "label vpn export" in a "router bgp AS vrf VRF"
context has no effect if the session is established unless the session
is reset.
Each label value modification is stored in the 'bgp_path_info_extra'
structure of each BGP update. But the change is not detected in the code
that handles the ADJ-RIB-OUT changes for each peer. The
'bgp_path_info_extra' is never parsed, and there is no previously stored
label value in another place.
To solve this issue, duplicate the label value from the
'bgp_path_info_extra' structure to the 'bgp_adj_out' structure that is
parsed when the value is changed.
Note: an alternate solution consisted in moving the label information
from the 'bgp_path_info_extra' structure to the 'attr' structure.
Doing this resulted in performing many changes in the BGP code, which was
too risky for maintenance versions.
Signed-off-by: Philippe Guibert <philippe.guibert@6wind.com>
Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
In a BGP L3VPN context using ADJ-RIB-IN (ie. enabled with 'soft-reconfiguration inbound'), after applying a deny route-map and then removing it, the remote MPLS label information is lost. As a consequence, BGP is unable to re-install the related routes in the RIB. The below configuration example illustrates a VPN setup with 'soft-reconfiguration' enabled > router bgp 65500 > [..] > neighbor 192.0.2.2 remote-as 65501 > address-family ipv4 vpn > neighbor 192.0.2.2 activate > neighbor 192.0.2.2 soft-reconfiguration inbound > exit-address-family > exit The 192.168.0.0/24 prefix has a remote label value of 102 in the BGP RIB. > # show bgp ipv4 vpn 192.168.0.0/24 > BGP routing table entry for 444:1:192.168.0.0/24, version 2 > [..] > 192.168.0.0 from 192.0.2.2 > Origin incomplete, metric 0, valid, external, best (First path received) > Extended Community: RT:52:100 > Remote label: 102 > Last update: Mon Mar 13 16:36:38 2023 A route-map is configured to filter incoming BGP updates from the `192.0.2.2` peer. > router bgp 65500 > address-family ipv4 vpn > neighbor 192.0.2.2 route-map rmap in > exit-address-family > exit > access-list 1 permit any > route-map rmap deny 1 > match ip address 1 The prefix is now filtered: > # show bgp ipv4 vpn 192.168.0.0/24 > # Then, the route-map is detached: because the ADJ-RIB-IN is present, a soft reconfiguration is performed. > router bgp 65500 > address-family ipv4 vpn > no neighbor 192.168.0.1 route-map rmap in The BGP RIB entry is present but the observed label value is lost: > # show bgp ipv4 vpn 192.168.0.0/24 > BGP routing table entry for 444:1:192.168.0.0/24, version 2 > [..] > 192.168.0.0 from 192.0.2.2 > Origin incomplete, metric 0, valid, external, best (First path received) > Extended Community: RT:52:100 > Last update: Mon Mar 13 16:36:38 2023 When the ADJ-RIB-IN is enabled for a given peer, and there is no filtering, incoming prefixes are present on both the RIB and the ADJ-RIB-IN database. Most of the attribute values are stored in the 'attr' structure: it is referenced by the ADJ-RIB-IN in the 'bgp_adj_in' structure, and referenced by the RIB in the 'bgp_path_info' structure. The label information is stored in the 'bgp_path_info_extra' structure, and is only referenced in the 'bgp_path_info' structure. When a BGP update is filtered, the 'bgp_path_info' structure of the given prefix of the BGP update is flushed, and the 'bgp_path_info_extra' structure is removed. When detaching the route-map, the soft reconfiguration attempts to get the label information from the 'bgp_path_info' structure if available. In our case, the structure is not available: the soft reconfiguration fails to find the label information. To solve this issue, duplicate the label value from the extra structure to the 'bgp_adj_in' structure that is parsed when a re-read is done. Note: an alternate solution consisted in moving the label information from the 'bgp_path_info_extra' structure to the 'attr' structure. Doing this resulted in performing many changes in the BGP code, which was too risky for maintenance versions. Signed-off-by: Philippe Guibert <philippe.guibert@6wind.com> Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
Clarify bgp_vpnv4_ebgp Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
This test ensures that when r1 changes the label value, then the new value is automatically propagated to remote peer. This demonstrates that the ADJ-RIB-OUT to r2 has been correctly updated. Signed-off-by: Philippe Guibert <philippe.guibert@6wind.com> Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
The test is done on r2. A BGP update is received on r2, and is filtered on r2. The RIB of r2 does not have the BGP update stored, but the ADJ-RIB-IN is yet present. To demonstrate this, if the inbound route-map is removed, then the BGP update should be copied from the the ADJ-RIB-IN and added to the RIB with the label value. Signed-off-by: Philippe Guibert <philippe.guibert@6wind.com> Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
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This version was duplicating the labels into adj-rib-in and adj-rib-out. Replaced by #15434 |
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in order to solve: