[PATCH RFC 3/3] RDMA/siw: Require non-zero 6-byte MACs for soft iWARP

[Chuck Lever <cel@kernel.org>]

From: Chuck Lever <chuck.lever@oracle.com>

In the past, LOOPBACK and NONE (tunnel) devices had all-zero MAC
addresses. siw_device_create() would fall back to copying the
device's name in those cases, because an all-zero MAC address breaks
the RDMA core IP-to-device lookup mechanism.

However, in some cases, the net_device::name field is also empty.
So we're back at square one.

Rather than checking the device type, look at the
net_device::addr_len field. If it's got the right number of octets
and it is not all zeroes, use that.

Then, to enable siw support for that device/address type, change
the device driver to ensure such devices have a valid 6-octet MAC
address. For virtual devices, using eth_hw_addr_random() is
sufficient.

Fixes: a2d36b02c15d ("RDMA/siw: Enable siw on tunnel devices")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 drivers/infiniband/sw/siw/siw_main.c |   22 +++++++---------------
 1 file changed, 7 insertions(+), 15 deletions(-)

diff --git a/drivers/infiniband/sw/siw/siw_main.c b/drivers/infiniband/sw/siw/siw_main.c
index 65b5cda5457b..2c31bf397993 100644
--- a/drivers/infiniband/sw/siw/siw_main.c
+++ b/drivers/infiniband/sw/siw/siw_main.c
@@ -304,10 +304,15 @@ static const struct ib_device_ops siw_device_ops = {
 
 static struct siw_device *siw_device_create(struct net_device *netdev)
 {
+	static const u8 zeromac[ETH_ALEN] = { 0 };
 	struct siw_device *sdev = NULL;
 	struct ib_device *base_dev;
 	int rv;
 
+	if ((netdev->addr_len != ETH_ALEN) ||
+	    (memcmp(netdev->dev_addr, zeromac, ETH_ALEN) == 0))
+		return NULL;
+
 	sdev = ib_alloc_device(siw_device, base_dev);
 	if (!sdev)
 		return NULL;
@@ -316,21 +321,8 @@ static struct siw_device *siw_device_create(struct net_device *netdev)
 
 	sdev->netdev = netdev;
 
-	if (netdev->type != ARPHRD_LOOPBACK && netdev->type != ARPHRD_NONE) {
-		addrconf_addr_eui48((unsigned char *)&base_dev->node_guid,
-				    netdev->dev_addr);
-	} else {
-		/*
-		 * This device does not have a HW address,
-		 * but connection mangagement lib expects gid != 0
-		 */
-		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);
-	}
+	addrconf_addr_eui48((unsigned char *)&base_dev->node_guid,
+			    netdev->dev_addr);
 
 	base_dev->uverbs_cmd_mask |= BIT_ULL(IB_USER_VERBS_CMD_POST_SEND);