SRv6 BGP SID reachability #14810

dmytroshytyi-6WIND · 2023-11-16T14:54:27Z

For BGP SRv6 updates, This PR considers "SRv6 SID reachability" and replaces the NH reachability with the
SRv6 SID reachability.

Today, only the NH reachability is checked, and when route is installed, if the SRv6 SID is not reachable
then the SRv6 segs route will fail to be installed.
This is what happens on kernel.

This PR:

avoids this use case, and does not install the BGP route.
ensures the SID is reachable, before installing the BGP route to zebra

Possible cases like the one below are not considered, and do not work anyway:

Router A and D are running BGP protocol. The route map, to set nexthop == C, is configured on
router D. Such that router C IPv6 address is verified to be reachable to flag the SRv6 reachable,
but if route on the router C that points to D router's SRv6 SID dissapears(broken link),
on node A SID is expected to be still reachable, because nexthop C is reachable.

BGP update with explicit nexthop(C) set via route-map and SRV6 SID
__________________________ 
|                         |
▽                         ^
(A-B-C--------------------D)
     
     ^                    ^
nexthop C                SRv6 SID
of BGP update

doc/user/bgp.rst

bgpd/bgp_nht.c

tests/topotests/bgp_srv6_sid_reachability/r1/bgpd.conf

tests/topotests/bgp_srv6_sid_reachability/r2/bgpd.conf

tests/topotests/bgp_srv6_sid_reachability/r3/bgpd.conf

ton31337 · 2023-11-19T18:54:38Z

Just a quick question: is this behavior something that other vendors have (SID reachability tracking)? I'm worried that we can't break anything if this is turned ON by default and can't be controlled. Maybe a knob would be handy?

riw777

looks good

bgpd/bgp_nht.c

eddieruan-alibaba · 2023-11-30T22:39:47Z

Would this raise any scale concerns?

VPN SID is similar to vpn label for MPLS VPN, which provides local information once packets reach to this PE. In the example you provide,

| |
▽ ^
(A-B-C--------------------D)

If we don't sue route-map to set nexthop, the nexthop is D. Do we really want to let A, B, C all aware the reachablity of your VPN SID, or just keep it as local context to D if some chip has scale concerns with v6 prefixes.

https://datatracker.ietf.org/doc/rfc8986/ section 3.3. "Routed and non-routed SRv6 SIDs are the SRv6 instantiation of
global and local segments, "

how do you plan to handle these local segment use cases?

pguibert6WIND · 2024-01-19T11:23:46Z

ci:rerun

cscarpitta

@dmytroshytyi-6WIND Thanks for the SRv6 contribution. Overall LGTM, I have only two nits.

tests/topotests/bgp_srv6_sid_reachability/test_bgp_srv6l3vpn_over_ipv6.py

pguibert6WIND · 2024-01-26T12:20:52Z

bgpd/bgp_nht.c

-
-		if (is_bgp_static) {
+		if (pi && pi->attr && pi->attr->srv6_l3vpn) {
+			IPV6_ADDR_COPY(&(p->u.prefix6),


no need to check for pi != NULL. it is alread done above.

Thanks fixed.

pguibert6WIND · 2024-01-26T12:22:00Z

bgpd/bgp_nht.c

@@ -660,6 +672,7 @@ static void bgp_process_nexthop_update(struct bgp_nexthop_cache *bnc,

 			if (BGP_DEBUG(nht, NHT)) {
 				char buf[NEXTHOP_STRLEN];
+
 				zlog_debug(


no need to add empty line

Thanks Fixed.

pguibert6WIND

2 minor issues.
also, the commit "bgpd: srv6 sid reachability information".
I would add this in the commit log:
Fixes 7f8c7d9 ("bgpd: ignore nexthop validation for srv6-vpn")

BGP IPv4 L3VPN with SRv6 SID reachability example provided in the documentation Signed-off-by: Dmytro Shytyi <dmytro.shytyi@6wind.com>

Enable the SRv6 SID prefix generation in make_prefix() function of bgp_nht.c. Signed-off-by: Dmytro Shytyi <dmytro.shytyi@6wind.com> fixup: bgpd: extend make_prefix to form srv6-based prefix

In the case of SRv6-VPN we track the reachability to the SID. We check that the SID is available in the BGP update and then we check the nexthop reachability. Fixes 7f8c7d9 ("bgpd: ignore nexthop validation for srv6-vpn") Signed-off-by: Dmytro Shytyi <dmytro.shytyi@6wind.com> Signed-off-by: Philippe Guibert <philippe.guibert@6wind.com>

Verify that SRv6 SID becomes unreachable and further the IPv4 route in L3VPN becomes invalid. Signed-off-by: Dmytro Shytyi <dmytro.shytyi@6wind.com>

dmytroshytyi-6WIND · 2024-01-30T16:51:38Z

ci:rerun

dmytroshytyi-6WIND · 2024-01-31T06:28:26Z

ci:rerun

riw777 · 2024-02-20T14:57:58Z

2 minor issues. also, the commit "bgpd: srv6 sid reachability information". I would add this in the commit log: Fixes 7f8c7d9 ("bgpd: ignore nexthop validation for srv6-vpn")

If this were in, I think we could merge this.

dmytroshytyi-6WIND · 2024-02-20T15:53:54Z

2 minor issues. also, the commit "bgpd: srv6 sid reachability information". I would add this in the commit log: Fixes 7f8c7d9 ("bgpd: ignore nexthop validation for srv6-vpn")

If this were in, I think we could merge this.

This commit log includes the "Fixes" tag:
b3ac502

And these two comments were addressed:
#14810 (comment)
#14810 (comment)

riw777

looks good

This commit brings PR FRRouting/frr#14810 from FRR mainline to SONiC SRv6 BGP SID reachability FRRouting/frr#14810 Signed-off-by: cscarpitta <cscarpit@cisco.com>

#### Why I did it Bring the below PRs from FRR mainline to SONiC in order to support SRv6 SID Manager in SONiC. #### New patches that were added | Patch | FRR Pull Request | | ------------- | ----------------- | | 0064-SRv6-BGP-SID-reachability.patch | FRRouting/frr#14810 | | 0065-zebra-display-srv6-encapsulation-source-address-when-configured.patch | FRRouting/frr#16151 | | 0066-lib-fix-srv6-locator-flags-propagated-to-isis.patch | FRRouting/frr#15673 | | 0067-Add-support-for-SRv6-SID-Manager.patch | FRRouting/frr#15604 | | 0068-bgpd-Extend-BGP-to-communicate-with-the-SRv6-SID-Manager-to-allocate-release-SRv6-SIDs.patch | FRRouting/frr#15676 |

This commit brings PR FRRouting/frr#14810 from FRR mainline to SONiC SRv6 BGP SID reachability FRRouting/frr#14810 Signed-off-by: cscarpitta <cscarpit@cisco.com>

New patches that were added: Patch FRR Pull request 0086-isisd-lib-add-some-codepoints-usually-shared-with-other-vendors.patch FRRouting/frr#17957 0087-staticd-Add-support-for-SRv6-uA-behavior.patch FRRouting/frr#18198 Removed patches: Patch FRR commit / Pull request 0025-bgp-community-memory-leak-fix.patch FRRouting/frr@e613e12 0028-zebra-fix-parse-attr-problems-for-encap.patch FRRouting/frr@ba5a353 FRRouting/frr@569f9e4 FRRouting/frr@bd4fca1 0030-zebra-backpressure-Zebra-push-back-on-Buffer-Stream-.patch FRRouting/frr@a8efa99 0031-bgpd-backpressure-Add-a-typesafe-list-for-Zebra-Anno.patch FRRouting/frr@705fed7 0033-bgpd-backpressure-cleanup-bgp_zebra_XX-func-args.patch FRRouting/frr@5f379be 0034-gpd-backpressure-Handle-BGP-Zebra-Install-evt-Creat.patch FRRouting/frr@ccfe452 0035-bgpd-backpressure-Handle-BGP-Zebra-EPVN-Install-evt-.patch FRRouting/frr@a07df6f 0036-zebra-backpressure-Fix-Null-ptr-access-Coverity-Issu.patch FRRouting/frr@ed7005d 0037-bgpd-Increase-install-uninstall-speed-of-evpn-vpn-vn.patch FRRouting/frr@9edf45b 0038-zebra-Actually-display-I-O-buffer-sizes.patch FRRouting/frr@8d8f12b 0039-zebra-Actually-display-I-O-buffer-sizes-part-2.patch FRRouting/frr@33dccbe 0040-bgpd-backpressure-Fix-to-withdraw-evpn-type-5-routes.patch FRRouting/frr@f4ba472 0041-bgpd-backpressure-Fix-to-avoid-CPU-hog.patch FRRouting/frr@920bf45 0042-zebra-Use-built-in-data-structure-counter.patch FRRouting/frr@a23a938 0043-zebra-Use-the-ctx-queue-counters.patch FRRouting/frr@34670c4 0044-zebra-Modify-dplane-loop-to-allow-backpressure-to-fi.patch FRRouting/frr@3af381b 0045-zebra-Limit-queue-depth-in-dplane_fpm_nl.patch FRRouting/frr@8926ac1 0046-zebra-Modify-show-zebra-dplane-providers-to-give-mor.patch FRRouting/frr@98b11de 0047-bgpd-backpressure-fix-evpn-route-sync-to-zebra.patch FRRouting/frr@b47a92e 0048-bgpd-backpressure-fix-to-properly-remove-dest-for-bg.patch FRRouting/frr@4395fcd 0049-bgpd-backpressure-Improve-debuggability.patch FRRouting/frr@186db96 0050-bgpd-backpressure-Avoid-use-after-free.patch FRRouting/frr@40965e5 0051-bgpd-backpressure-fix-ret-value-evpn_route_select_in.patch FRRouting/frr@c4bbb5b 0052-bgpd-backpressure-log-error-for-evpn-when-route-inst.patch FRRouting/frr@6cf5b79 0055-bgpd-lib-Include-SID-structure-in-seg6local-nexthop.patch FRRouting/frr@0402551 0059-Fix-BGP-reset-on-suppress-fib-pending-configuration.patch FRRouting/frr#17487 0060-bgpd-Validate-both-nexthop-information-NEXTHOP-and-N.patch FRRouting/frr@a0d2734 0061-dont-print-warning-if-not-a-daemon.patch FRRouting/frr@cecf571 0062-zebra-lib-use-internal-rbtree-per-ns.patch FRRouting/frr#17297 0064-SRv6-BGP-SID-reachability.patch FRRouting/frr#14810 0065-zebra-display-srv6-encapsulation-source-address-when-configured.patch FRRouting/frr@890b67d 0066-lib-fix-srv6-locator-flags-propagated-to-isis.patch FRRouting/frr@03d2ad0 0067-Add-support-for-SRv6-SID-Manager.patch FRRouting/frr#15604 0068-bgpd-Extend-BGP-to-communicate-with-the-SRv6-SID-Manager-to-allocate-release-SRv6-SIDs.patch FRRouting/frr#15676 0069-lib-nexthop-code-should-use-uint16_t-for-nexthop-cou.patch FRRouting/frr@0bc79f5 0070-Allow-16-bit-size-for-nexthops.patch FRRouting/frr@9f8968f 0071-zebra-Only-notify-dplane-work-pthread-when-needed.patch FRRouting/frr#17062 0072-Fix-up-improper-handling-of-nexthops-for-nexthop-tra.patch FRRouting/frr#17076 0073-remove-in6addr-cmp.patch FRRouting/frr#17312 0074-bgp-best-port-reordering.patch FRRouting/frr#15572 0075-bgp-mp-info-changes.patch FRRouting/frr#16961 0076-Optimizations-and-problem-fixing-for-large-scale-ecmp-from-bgp.patch FRRouting/frr#17229 0077-frr-vtysh-dependencies-for-srv6-static-patches.patch FRRouting/frr@fd8edc3 0078-vtysh-de-conditionalize-and-reorder-install-node.patch FRRouting/frr@e26c580 0079-staticd-add-support-for-srv6.patch FRRouting/frr#16894 0081-bgpd-Optimize-evaluate-paths-for-a-peer-going-down.patch FRRouting/frr@9f55368 Realigned patches: Patch 0001-Reduce-severity-of-Vty-connected-from-message.patch 0002-Allow-BGP-attr-NEXT_HOP-to-be-0.0.0.0-due-to-allevia.patch 0003-nexthops-compare-vrf-only-if-ip-type.patch 0004-frr-remove-frr-log-outchannel-to-var-log-frr.log.patch 0005-Add-support-of-bgp-l3vni-evpn.patch 0006-Link-local-scope-was-not-set-while-binding-socket-for-bgp-ipv6-link-local-neighbors.patch 0007-ignore-route-from-default-table.patch 0008-Use-vrf_id-for-vrf-not-tabled_id.patch 0010-bgpd-Change-log-level-for-graceful-restart-events.patch 0021-Disable-ipv6-src-address-test-in-pceplib.patch 0022-cross-compile-changes.patch 0054-build-dplane-fpm-sonic-module.patch 0056-zebra-do-not-send-local-routes-to-fpm.patch 0057-Adding-changes-to-write-ip-nht-resolve-via-default-c.patch 0058-When-the-file-is-config-replayed-we-cannot-handle-th.patch 0061-Set-multipath-to-514-and-disable-bgp-vnc-for-optimiz.patch 0063-Patch-to-send-tag-value-associated-with-route-via-ne.patch 0080-SRv6-vpn-route-and-sidlist-install.patch 0082-Revert-bgpd-upon-if-event-evaluate-bnc-with-matching.patch 0083-staticd-add-cli-to-support-steering-of-ipv4-traffic-over-srv6-sid-list.patch 0084-lib-Return-duplicate-prefix-list-entry-test.patch 0085-This-error-happens-when-we-try-to-write-to-a-socket.patch Signed-off-by: Carmine Scarpitta <cscarpit@cisco.com>

frrbot bot added bgp documentation tests Topotests, make check, etc labels Nov 16, 2023

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dmytroshytyi-6WIND force-pushed the srv6_bgp_sid_reachability branch 2 times, most recently from ebfc5be to 4086473 Compare January 25, 2024 15:00

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dmytroshytyi-6WIND added 4 commits January 30, 2024 16:13

doc: bgp ipv4 l3vpn sid reachability

f49fc76

BGP IPv4 L3VPN with SRv6 SID reachability example provided in the documentation Signed-off-by: Dmytro Shytyi <dmytro.shytyi@6wind.com>

bgpd: extend make_prefix to form srv6-based prefix

26c747e

Enable the SRv6 SID prefix generation in make_prefix() function of bgp_nht.c. Signed-off-by: Dmytro Shytyi <dmytro.shytyi@6wind.com> fixup: bgpd: extend make_prefix to form srv6-based prefix

tests: an srv6 sid reachability use-case

5101463

Verify that SRv6 SID becomes unreachable and further the IPv4 route in L3VPN becomes invalid. Signed-off-by: Dmytro Shytyi <dmytro.shytyi@6wind.com>

dmytroshytyi-6WIND force-pushed the srv6_bgp_sid_reachability branch from 4086473 to 5101463 Compare January 30, 2024 15:17

riw777 approved these changes Feb 27, 2024

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riw777 merged commit c4f9b87 into FRRouting:master Feb 27, 2024

cscarpitta mentioned this pull request Dec 16, 2024

[FRR]: Add support for SRv6 SID Manager sonic-net/sonic-buildimage#21185

Merged

mssonicbld mentioned this pull request Jan 7, 2025

[action] [PR:21185] [FRR]: Add support for SRv6 SID Manager Azure/sonic-buildimage-msft#497

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cscarpitta mentioned this pull request Apr 8, 2025

[FRR]: Upgrade FRR to version 10.3 sonic-net/sonic-buildimage#22267

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SRv6 BGP SID reachability #14810

SRv6 BGP SID reachability #14810

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