linux-kernel - [PATCH 2/4] RDMA/core: Resolve MAC of next-hop device without ARP support

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Message-ID: <20250907160833.56589-3-edwards@nvidia.com>
Date: Sun, 7 Sep 2025 19:08:31 +0300
From: Edward Srouji <edwards@...dia.com>
To: <jgg@...pe.ca>, <leon@...nel.org>
CC: <linux-rdma@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<parav@...dia.com>, <cratiu@...dia.com>, <vdumitrescu@...dia.com>,
	<edwards@...dia.com>, <kuba@...nel.org>, <tariqt@...dia.com>,
	<mbloch@...dia.com>, <gal@...dia.com>
Subject: [PATCH 2/4] RDMA/core: Resolve MAC of next-hop device without ARP support

From: Parav Pandit <parav@...dia.com>

Currently, if the next-hop netdevice does not support ARP resolution,
the destination MAC address is silently set to zero without reporting
an error. 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.

Fixes: 7025fcd36bd6 ("IB: address translation to map IP toIB addresses (GIDs)")
Signed-off-by: Parav Pandit <parav@...dia.com>
Reviewed-by: Vlad Dumitrescu <vdumitrescu@...dia.com>
Signed-off-by: Edward Srouji <edwards@...dia.com>
---
 drivers/infiniband/core/addr.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/infiniband/core/addr.c b/drivers/infiniband/core/addr.c
index 594e7ee335f7..ca86c482662f 100644
--- a/drivers/infiniband/core/addr.c
+++ b/drivers/infiniband/core/addr.c
@@ -454,14 +454,10 @@ static int addr_resolve_neigh(const struct dst_entry *dst,
 {
 	int ret = 0;
 
-	if (ndev_flags & IFF_LOOPBACK) {
+	if (ndev_flags & IFF_LOOPBACK)
 		memcpy(addr->dst_dev_addr, addr->src_dev_addr, MAX_ADDR_LEN);
-	} else {
-		if (!(ndev_flags & IFF_NOARP)) {
-			/* If the device doesn't do ARP internally */
-			ret = fetch_ha(dst, addr, dst_in, seq);
-		}
-	}
+	else
+		ret = fetch_ha(dst, addr, dst_in, seq);
 	return ret;
 }
 
-- 
2.21.3