Re: [PATCH RFC] RDMA/core: Handle ARPHRD_NONE devices

[Tom Talpey <tom@talpey.com>]

On 6/2/2023 3:24 PM, Chuck Lever wrote:
> From: Chuck Lever <chuck.lever@oracle.com>
> 
> We would like to enable the use of siw on top of a VPN that is
> constructed and managed via a tun device. That hasn't worked up
> until now because ARPHRD_NONE devices (such as tun devices) have
> no GID for the RDMA/core to look up.
> 
> But it turns out that the egress device has already been picked for
> us. addr_handler() just has to do the right thing with it.
> 
> Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
>   drivers/infiniband/core/cma.c |    4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
> index 56e568fcd32b..3351dc5afa17 100644
> --- a/drivers/infiniband/core/cma.c
> +++ b/drivers/infiniband/core/cma.c
> @@ -704,11 +704,15 @@ cma_validate_port(struct ib_device *device, u32 port,
>   		ndev = dev_get_by_index(dev_addr->net, bound_if_index);
>   		if (!ndev)
>   			return ERR_PTR(-ENODEV);
> +	} else if (dev_type == ARPHRD_NONE) {
> +		sgid_attr = rdma_get_gid_attr(device, port, 0);
> +		goto out;
>   	} else {
>   		gid_type = IB_GID_TYPE_IB;
>   	}
>   
>   	sgid_attr = rdma_find_gid_by_port(device, gid, gid_type, port, ndev);
> +out:
>   	dev_put(ndev);
>   	return sgid_attr;
>   }

I like it, but doesn't this test in siw_main.c also need to change?

static struct siw_device *siw_device_create(struct net_device *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);
	}


Tom.