Re: [PATCH v3 1/4] RDMA/siw: Fabricate a GID on tun and loopback devices

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On 6/14/2023 10:00 AM, Chuck Lever wrote:
From: Chuck Lever <chuck.lever@xxxxxxxxxx>

LOOPBACK and NONE (tunnel) devices have all-zero MAC addresses.
Currently, siw_device_create() falls back to copying the IB device's
name in those cases, because an all-zero MAC address breaks the RDMA
core address resolution mechanism.

However, at the point when siw_device_create() constructs a GID, the
ib_device::name field is uninitialized, leaving the MAC address to
remain in an all-zero state.

Fabricate a random artificial GID for such devices, and ensure that
artificial GID is returned for all device query operations.

Just one wording suggestion on the above:

"Fabricate a random artificial GID for such devices, and ensure that
 the same artificial GID is returned for all device query operations."

Reviewed-by: Tom Talpey <tom@xxxxxxxxxx>


Reported-by: Tom Talpey <tom@xxxxxxxxxx>
Link: https://lore.kernel.org/linux-rdma/SA0PR15MB391986C07C4D41E107E79659994FA@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/T/#t
Fixes: a2d36b02c15d ("RDMA/siw: Enable siw on tunnel devices")
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
  drivers/infiniband/sw/siw/siw.h       |    1 +
  drivers/infiniband/sw/siw/siw_main.c  |   22 ++++++++--------------
  drivers/infiniband/sw/siw/siw_verbs.c |    4 ++--
  3 files changed, 11 insertions(+), 16 deletions(-)

diff --git a/drivers/infiniband/sw/siw/siw.h b/drivers/infiniband/sw/siw/siw.h
index 2f3a9cda3850..8b4a710b82bc 100644
--- a/drivers/infiniband/sw/siw/siw.h
+++ b/drivers/infiniband/sw/siw/siw.h
@@ -74,6 +74,7 @@ struct siw_device {
u32 vendor_part_id;
  	int numa_node;
+	char raw_gid[ETH_ALEN];
/* physical port state (only one port per device) */
  	enum ib_port_state state;
diff --git a/drivers/infiniband/sw/siw/siw_main.c b/drivers/infiniband/sw/siw/siw_main.c
index 65b5cda5457b..f45600d169ae 100644
--- a/drivers/infiniband/sw/siw/siw_main.c
+++ b/drivers/infiniband/sw/siw/siw_main.c
@@ -75,8 +75,7 @@ static int siw_device_register(struct siw_device *sdev, const char *name)
  		return rv;
  	}
- siw_dbg(base_dev, "HWaddr=%pM\n", sdev->netdev->dev_addr);
-
+	siw_dbg(base_dev, "HWaddr=%pM\n", sdev->raw_gid);
  	return 0;
  }
@@ -313,24 +312,19 @@ static struct siw_device *siw_device_create(struct net_device *netdev)
  		return NULL;
base_dev = &sdev->base_dev;
-
  	sdev->netdev = netdev;
- if (netdev->type != ARPHRD_LOOPBACK && netdev->type != ARPHRD_NONE) {
-		addrconf_addr_eui48((unsigned char *)&base_dev->node_guid,
-				    netdev->dev_addr);
+	if (netdev->addr_len) {
+		memcpy(sdev->raw_gid, netdev->dev_addr,
+		       min_t(unsigned int, netdev->addr_len, ETH_ALEN));
  	} else {
  		/*
-		 * This device does not have a HW address,
-		 * but connection mangagement lib expects gid != 0
+		 * This device does not have a HW address, but
+		 * connection mangagement requires a unique gid.
  		 */
-		size_t len = min_t(size_t, strlen(base_dev->name), 6);
-		char addr[6] = { };
-
-		memcpy(addr, base_dev->name, len);
-		addrconf_addr_eui48((unsigned char *)&base_dev->node_guid,
-				    addr);
+		eth_random_addr(sdev->raw_gid);
  	}
+	addrconf_addr_eui48((u8 *)&base_dev->node_guid, sdev->raw_gid);
base_dev->uverbs_cmd_mask |= BIT_ULL(IB_USER_VERBS_CMD_POST_SEND); diff --git a/drivers/infiniband/sw/siw/siw_verbs.c b/drivers/infiniband/sw/siw/siw_verbs.c
index 398ec13db624..32b0befd25e2 100644
--- a/drivers/infiniband/sw/siw/siw_verbs.c
+++ b/drivers/infiniband/sw/siw/siw_verbs.c
@@ -157,7 +157,7 @@ int siw_query_device(struct ib_device *base_dev, struct ib_device_attr *attr,
  	attr->vendor_part_id = sdev->vendor_part_id;
addrconf_addr_eui48((u8 *)&attr->sys_image_guid,
-			    sdev->netdev->dev_addr);
+			    sdev->raw_gid);
return 0;
  }
@@ -218,7 +218,7 @@ int siw_query_gid(struct ib_device *base_dev, u32 port, int idx,
/* subnet_prefix == interface_id == 0; */
  	memset(gid, 0, sizeof(*gid));
-	memcpy(&gid->raw[0], sdev->netdev->dev_addr, 6);
+	memcpy(gid->raw, sdev->raw_gid, ETH_ALEN);
return 0;
  }






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