[Orchagent] Recursive nexthop group enhancement #3105

utpalkantpintoo · 2024-04-07T09:12:10Z

What I did

Implemented recursive nexthop group enhancement in Orchagent (NhgOrch). They have been proposed in:
sonic-net/SONiC#1636

Why I did it

These changes are required to handle a new field - "nexthop_group" in the App DB NEXT_HOP_GROUP_TABLE. Such nexthop groups are called recursive nexthop groups. This field contains the list of member (singleton) nexthop groups. Such recursive nexthop groups are represented by NEXT_HOP_GROUP objects.

How I verified it

Details if related

linux-foundation-easycla · 2024-04-07T09:12:15Z

The committers listed above are authorized under a signed CLA.

✅ login: utpalkantpintoo / name: Utpal (ff2112e, 3ae044a, 6776a5f, 0788fc1, fe7f488)

utpalkantpintoo · 2024-05-02T09:46:57Z

/azpw run Azure.sonic-swss

mssonicbld · 2024-05-02T09:47:00Z

/AzurePipelines run Azure.sonic-swss

azure-pipelines · 2024-05-02T09:47:08Z

Azure Pipelines successfully started running 1 pipeline(s).

Gokulnath-Raja · 2024-05-14T05:03:08Z

orchagent/nhgorch.cpp

+                }
+
+                /* Form nexthopgroup key with the nexthopgroup keys of available members */
+                nhgv = tokenize(nhgs, ',');


Can we use NHG_DELIMITER instead of ","

Gokulnath-Raja · 2024-05-14T05:03:14Z

orchagent/nhgorch.cpp

+                    if (nhgs.empty())
+                        nhgs = nhgm;
+                    else
+                        nhgs += ',' + nhgm;


Can we use NHG_DELIMITER instead of ","

Gokulnath-Raja · 2024-05-14T05:12:34Z

orchagent/nhgorch.cpp

@@ -687,6 +807,9 @@ bool NextHopGroup::syncMembers(const std::set<NextHopKey>& nh_keys)
 {
    SWSS_LOG_ENTER();

+    /* This method should not be called for single-membered non-recursive nexthop groups */
+    assert(isRecursive() || (m_members.size() > 1));


Instead of assert can we handle as exception?

This is in-line with similar error handling elsewhere in the code. We do not have a way to gracefully handle once we end up here for a non-recursive singleton nhg. There are necessary checks in caller fn.

Gokulnath-Raja · 2024-05-14T05:27:38Z

orchagent/nhgorch.cpp

-     */
-    if (m_is_temp)
+    /* If the group is non-recursive with single member, the group ID will be the only member's NH ID */
+    if (!isRecursive() && (m_members.size() == 1))


Do we need m_is_temp check?

That'll be redundant as the current check will be true for "temp" nhgs as well.

Gokulnath-Raja · 2024-05-14T05:32:01Z

orchagent/nhgorch.cpp

+    {
+        nh_id = gIntfsOrch->getRouterIntfsId(m_key.alias);
+
+        if ((nh_id == SAI_NULL_OBJECT_ID) &&


We don't consider loopback as nexthop and trap packet to CPU during route add https://github.com/sonic-net/sonic-swss/blob/master/orchagent/routeorch.cpp#L1789, so do we need to add this CPU port for NHG?

Will make the NhgOrch behavior in-line with RouteOrch handling.
But I see an issue where if we receive such a msg, we'll end up holding the msgs in the corres. m_toSync queue(s) till the route is withdrawn.

We install IP2ME for loopback IPs, right? I think, we can safely ignore the message with error log if we get a NHG with loopback interface.

If the NHG is not created, the route msg will be retained waiting for the NHG. This may require creating a dummy NHG with just the key so that route msg can also be ignored.
This should be addressed in both the NhgOrch and RouteOrch as a defect fix.

venkatmahalingam · 2024-05-14T06:43:33Z

orchagent/nhgorch.cpp

-            for (uint32_t i = 0; i < ipv.size(); i++)
+            /* Keeps track of any non-existing member of a recursive nexthop group */
+            bool non_existent_member = false;
+


Do we need to throw a warning if ipv.size() is non-zero when is_recursive is set?

venkatmahalingam · 2024-05-14T06:47:25Z

orchagent/nhgorch.cpp

                }
-                nhg_str += ipv[i] + NH_DELIMITER + alsv[i];
            }



Can we add a SWSS_LOG_DEBUG for nhg_str?

adyeung · 2024-05-16T16:17:32Z

@venkatmahalingam @Gokulnath-Raja pls signoff if you have no further comments

Implemented recursive nexthop group enhancement in Orchagent (NhgOrch). They have been proposed in: sonic-net/SONiC#1636 Why I did it: These changes are required to handle a new field - "nexthop_group" in the App DB NEXT_HOP_GROUP_TABLE. Such nexthop groups are called recursive nexthop groups. This field contains the list of member (singleton) nexthop groups. Such recursive nexthop groups are represented by NEXT_HOP_GROUP objects.

Gokulnath-Raja · 2024-05-17T04:49:20Z

orchagent/nhgorch.cpp

+            /* A NHG should not have both regular(ip/alias) and recursive fields */
+            if (is_recursive && (!ips.empty() || !aliases.empty()))
+            {
+                SWSS_LOG_ERROR("Nexthop group %s has both regular(ip/alias) and recursive fields", index.c_str());


Can we move this to info log ?

Since the nexthop-group is not created due to this check, it's better to log this as error.

goomadao · 2024-05-24T08:29:10Z

Besides, there might be two issues that:

If a route points to a singleton NEXTHOP_GROUP and it becomes non-singleton later, the route will still refer to the SAI ID of the NEXTHOP instead of the newly created NEXTHOP_GROUP
For recursive situations, how to update NEXTHOP_GROUP recursively? For example, NEXTHOP_GROUP_TABLE:ID1 points to ID2 & ID3, ID2 refers to NEXTHOP NHa & NHb. When ID2 is updated to refer to NHa, NHb & NHc, how can we add member NHc to NEXTHOP_GROUP_TABLE:ID1 simultaneously?

utpalkantpintoo · 2024-05-29T09:47:45Z

Hi @goomadao

Thanks for the comments. Please find below my response:

For any nexthop-group update which changes its SAI-ID, it is expected that the routing app update the associated routes as well. This is expected behavior with FRR.
Handling it in Orchagent (NhgOrch/RouteOrch) will require maintaining a nexthop-group to route entries data-structure.
With recursive nexthop-group scheme, it is expected that the routing app resolve the recursive nexthop-groups and provide a recursive nexthop-group with ultimate nexthop member(s) which are not recursive themselves. This is expected behavior with FRR.

goomadao · 2024-06-06T07:54:24Z

@utpalkantpintoo Thanks for your explanation. You're right, I missed that there is an upper application where the update could be triggered.

Could you please take a look at the pending review I raised before? I still can't figure out any situation to get into those two conditions.

utpalkantpintoo requested a review from prsunny as a code owner April 7, 2024 09:12

nkelapur mentioned this pull request Apr 10, 2024

Changes for handling recursive NHG entries sonic-net/SONiC#1636

Merged

utpalkantpintoo force-pushed the recursive_nhg branch from f5d145d to 69c204f Compare May 2, 2024 09:45

hasan-brcm approved these changes May 6, 2024

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adyeung mentioned this pull request May 7, 2024

NextHop Group Table Enhancement sonic-net/SONiC#1594

Closed

utpalkantpintoo force-pushed the recursive_nhg branch from d54cd50 to 11379cf Compare May 8, 2024 06:45

Gokulnath-Raja reviewed May 14, 2024

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venkatmahalingam reviewed May 14, 2024

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utpalkantpintoo force-pushed the recursive_nhg branch 2 times, most recently from 4f972b0 to 166785d Compare May 15, 2024 09:13

utpalkantpintoo added 5 commits May 17, 2024 09:21

Addressed review comments

0788fc1

utpalkantpintoo force-pushed the recursive_nhg branch from 166785d to 0788fc1 Compare May 17, 2024 03:51

Gokulnath-Raja reviewed May 17, 2024

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Gokulnath-Raja approved these changes May 17, 2024

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venkatmahalingam approved these changes May 17, 2024

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srj102 approved these changes May 18, 2024

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srj102 merged commit 536f43a into sonic-net:master May 18, 2024
17 checks passed

utpalkantpintoo deleted the recursive_nhg branch May 18, 2024 16:40

eddieruan-alibaba mentioned this pull request Sep 29, 2024

[fpmsyncd] Fpmsyncd Next Hop Table Enhancement #2919

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[Orchagent] Recursive nexthop group enhancement #3105

[Orchagent] Recursive nexthop group enhancement #3105

utpalkantpintoo commented Apr 7, 2024

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[Orchagent] Recursive nexthop group enhancement #3105

[Orchagent] Recursive nexthop group enhancement #3105

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