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From: Jason Gunthorpe <>
To: Olga Kornievskaia <>
Cc: linux-rdma <>
Subject: Re: Help understand use of MAC address resolution in RDMA
Date: Thu, 5 Aug 2021 22:44:36 -0300	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Thu, Aug 05, 2021 at 10:38:42AM -0400, Olga Kornievskaia wrote:
> Hi folks,
> Can somebody help me understand how RoCE (this is probably RDMA core
> and not specific to RoCE but I'm not sure) manages destination MAC
> addresses for its connection?
> Specifically the problem being observed is a server initiates an RDMA
> CM disconnect (client replies), client tries to reconnect. Server
> sends an ARP advertising a different MAC for the IP that the RDMA
> connection was using. RDMA code keeps sending the RDMA CM connect
> message to the old MAC for a certains period of time (90-100sec) then
> it finally sends it to the new MAC address.
> Question: how does the core RDMA layer manage the MAC address for the
> connection. Why does it seem like it ignores the ARP updates?

RDMA objects acquire a MAC adress when they are created and do not
synchronize with the neighbor cache after.

What you are seeing is that the CM_ID object holds the bad mac until
it is destoroyed and likely a new CM_ID object gets created that holds
the updated MAC


  reply	other threads:[~2021-08-06  1:44 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-05 14:38 Help understand use of MAC address resolution in RDMA Olga Kornievskaia
2021-08-06  1:44 ` Jason Gunthorpe [this message]
2021-08-06  2:05   ` Olga Kornievskaia

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