From: Jason Gunthorpe <jgg@ziepe.ca>
To: Parav Pandit <parav@nvidia.com>
Cc: Leon Romanovsky <leon@kernel.org>,
Edward Srouji <edwards@nvidia.com>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Cosmin Ratiu <cratiu@nvidia.com>,
Vlad Dumitrescu <vdumitrescu@nvidia.com>,
"kuba@kernel.org" <kuba@kernel.org>,
Tariq Toukan <tariqt@nvidia.com>, Mark Bloch <mbloch@nvidia.com>,
Gal Pressman <gal@nvidia.com>
Subject: Re: [PATCH 2/4] RDMA/core: Resolve MAC of next-hop device without ARP support
Date: Mon, 15 Sep 2025 13:30:02 -0300 [thread overview]
Message-ID: <20250915163002.GJ882933@ziepe.ca> (raw)
In-Reply-To: <CY8PR12MB71954BE7258390B4B7965E8FDC0EA@CY8PR12MB7195.namprd12.prod.outlook.com>
On Wed, Sep 10, 2025 at 10:55:36AM +0000, Parav Pandit wrote:
> > > This leads to incorrect behavior and may result in packet transmission
> > failures.
> > >
> > > Fix this by deferring MAC resolution to the IP stack via neighbour
> > > lookup, allowing proper resolution or error reporting as appropriate.
> >
> > What is the difference here? For IPv4, neighbour lookup is ARP, no?
> It is but it is not the only way. A device may not do ARP by itself but it relies on the rest of the stack like vrf or ip vlan mode to resolve.
> A user may also set manual entry without explicit ARP.
I think it was just a mistake to use NOARP this way in RDMA, I looked
in the git history and there was no justification. That or it was
right in the 2.x days and netdev moved on to the current schem.
I expect to just call the neighbor functions and if they can't work
for some reason they should fail?
Jason
next prev parent reply other threads:[~2025-09-15 16:30 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-07 16:08 [PATCH 0/4] Fix local destination address resolution with VRF Edward Srouji
2025-09-07 16:08 ` [PATCH 1/4] RDMA/core: Squash a single user static function Edward Srouji
2025-09-10 8:17 ` Leon Romanovsky
2025-09-10 10:51 ` Parav Pandit
2025-09-10 12:21 ` Leon Romanovsky
2025-09-07 16:08 ` [PATCH 2/4] RDMA/core: Resolve MAC of next-hop device without ARP support Edward Srouji
2025-09-10 8:32 ` Leon Romanovsky
2025-09-10 10:55 ` Parav Pandit
2025-09-15 16:30 ` Jason Gunthorpe [this message]
2025-09-15 17:16 ` Parav Pandit
2025-09-07 16:08 ` [PATCH 3/4] RDMA/core: Use route entry flag to decide on loopback traffic Edward Srouji
2025-09-07 16:08 ` [PATCH 4/4] IB/ipoib: Ignore L3 master device Edward Srouji
2025-09-16 11:10 ` [PATCH v1 0/4] Fix local destination address resolution with VRF Edward Srouji
2025-09-16 11:11 ` [PATCH v1 1/4] RDMA/core: Squash a single user static function Edward Srouji
2025-09-16 11:11 ` [PATCH v1 2/4] RDMA/core: Resolve MAC of next-hop device without ARP support Edward Srouji
2025-09-16 11:11 ` [PATCH v1 3/4] RDMA/core: Use route entry flag to decide on loopback traffic Edward Srouji
2025-09-16 11:11 ` [PATCH v1 4/4] IB/ipoib: Ignore L3 master device Edward Srouji
2025-09-18 9:24 ` [PATCH v1 0/4] Fix local destination address resolution with VRF Leon Romanovsky
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