Feature request: Cisco IOS BGP as-path replace command support

[kefins]

Hi, I got some warning while parsing Cisco IOS snapshot, here is the detail warning.

>>> bfq.initIssues().answer().frame()
status: TRYINGTOASSIGN
.... no task information
status: TERMINATEDNORMALLY
.... 2022-02-16 16:04:29.108000+08:00 Begin job.
  Nodes                                                                                         Source_Lines           Type                                  Details                           Line_Text                                                                                       Parser_Context
0  None                                                                   [configs/100.127.131.94.cfg:[550]]  Parse warning              This syntax is unrecognized           set as-path replace 65031                                [set_rm_stanza rm_stanza route_map_stanza stanza cisco_configuration]
1  None                                                                   [configs/100.127.131.95.cfg:[556]]  Parse warning              This syntax is unrecognized           set as-path replace 65032                                [set_rm_stanza rm_stanza route_map_stanza stanza cisco_configuration]
2  None  [configs/11.240.108.181.cfg:[1020, 1025, 1030, 1035, 1042, 1047], configs/11.240.107.51.cfg:[102...  Parse warning              This syntax is unrecognized           set as-path replace 65010                                [set_rm_stanza rm_stanza route_map_stanza stanza cisco_configuration]
3  None                                [configs/11.240.108.181.cfg:[1147], configs/11.240.107.51.cfg:[1147]]  Parse warning              This syntax is unrecognized   maximum-paths eibgp as-path-relax  [dec maximum_paths_bgp_tail bgp_tail address_family_inner address_family_rb_stanza router_bgp_st...
4  None  [configs/11.240.108.181.cfg:[1167, 1168, 1169, 1170, 1171, 1172, 1173, 1174, 1175, 1176, 1177, 1...  Parse warning  This feature is not currently supported  advertise-map RP_DENY_IBGP_PEER_IP  [agg_advertise_map aggregate_address_rb_stanza address_family_inner address_family_rb_stanza rou...
5  None              [configs/11.240.108.181.cfg:[954, 959, 964], configs/11.240.107.51.cfg:[954, 959, 964]]  Parse warning              This syntax is unrecognized           set as-path replace 65313                                [set_rm_stanza rm_stanza route_map_stanza stanza cisco_configuration]

And the unrecognized commands are set as-path replace 65031 and maximum-paths eibgp as-path-relax, the feature is not currently supported command is aggregate-address 11.20.144.0 255.255.240.0 summary-only advertise-map RP_DENY_IBGP_PEER_IP attribute-map RP_DR_OPEN_SET_COMM.

After talking about these commands with @arifogel , who said some of them had been support on FRR. I wonder if they can be migrated to Cisco IOS.

• set as-path replace

  

• maximum-paths eibgp as-path-relax

  

• aggregate-address 11.20.144.0 255.255.240.0 summary-only

  

[arifogel]

@kefins Thanks for this.

• set as-path replace sounds like something we should be able to implement without much difficulty. IOS's version of this command is similar enough to FRR's that I think it should be a relatively simple change.
• I believe the magic hidden IOS command you are looking for is bgp bestpath as-path multipath-relax at the router bgp level. It appears we support this. Regarding the slack thread about maximum-paths support: We simply treats the numerical argument as either 1 or infinity, i.e. single path or multipath.
• aggregate-address 11.20.144.0 255.255.240.0 summary-only advertise-map RP_DENY_IBGP_PEER_IP attribute-map RP_DR_OPEN_SET_COMM
  • this command is mostly supported, but we don't support advertise-map at this time. More generally, Batfish currently doesn't support setting properties of aggregate routes based on a combination of properties of contributors. Supporting this feature will require significant changes to Batfish's aggregate generation pipeline. Adding this support is not on the horizon at this time.

[kefins]

@arifogel Thank you for your replying. It's really a good news, set as-path replace is necessary for my snapshot, from which should verify a network loop. But now batfish gives no loop. So if there is a patch, please let me know as soon as possible. Thank you again.

[kefins]

Hi, @arifogel May I ask when will this patch be released? I need to verify a loop which was produced by bgp as-path replace.

[arifogel]

Turns out it was nothing like the FRR construct, but I was able to churn out support anyhow. May take some time for review, but should be in soon.

[kefins]

OK, thank you so much.