Bug 1833373

Summary:	[OVN SCALE] Improve Load Balancer Hairpin detection/scalability
Product:	Red Hat Enterprise Linux Fast Datapath	Reporter:	Dumitru Ceara <dceara>
Component:	OVN	Assignee:	Numan Siddique <nusiddiq>
Status:	CLOSED ERRATA	QA Contact:	ying xu <yinxu>
Severity:	low	Docs Contact:
Priority:	low
Version:	FDP 20.C	CC:	ctrautma, dcbw, mark.d.gray, nusiddiq, trozet
Target Milestone:	---
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Hardware:	Unspecified
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Fixed In Version:	ovn2.13-20.09.0-14	Doc Type:	If docs needed, set a value
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Last Closed:	2021-03-25 19:06:08 UTC	Type:	Bug
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
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Embargoed:
Bug Depends On:
Bug Blocks:	1859924

Description Dumitru Ceara 2020-05-08 14:26:44 UTC

Description of problem:
In order to detect that the backend selected for load balanced traffic is actually the source of the traffic (i.e., hairpin) OVN currently creates 2 logical flows per VIP in table LS_IN_PRE_HAIRPIN. The flow match field looks like:

Initiator traffic:
(ip.src == backend-ip1 && ip.dst == backend-ip2) || .. || (ip.src == backend-ipn && ip.dst == backend-ipn)

Reply traffic:
((ip.src == backend-ip1) || .. || (ip.src == backend-ipn)) && ip.dst = VIP

This gets processed by ovn-controller and translated into 2 * N openflow entries.

A better approach would be to create a new SB DB table, e.g., Hairpin_Endpoints with columns
- datapath
- dest_ip (VIP)
- dest_port (VIP-port)
- proto
- sources (list of backend IPs & ports)

ovn-northd would populate this table for all Load_Balancer VIPs (currently hairpin is supported only for logical switches but could be extended to logical routers too) and ovn-controller would generate the required openflow entries that perform hairpin detection.

Comment 2 Dan Williams 2021-03-25 19:06:08 UTC

Shipped in FDP 20.I