[PATCH 1/1] Add 'Transport Interface' (triface) option. This can be used to specify the IP interface to use for the connection. The driver uses that to set SO_BINDTODEVICE on the socket before connecting.

[Hannes Reinecke]

On 5/3/21 6:59 PM, Belanger, Martin wrote:
> Hi Hannes,
> 
> I just noticed there were in-line comments. to answer you questions:
> 

This is the recommended style when working with linux patches; please do 
not top-post.

> Q1) Why not simply 'host_iface' ? 'triface' is a bit awkward.
> A1) I used TRIFACE to keep consistency with all other transport options: traddr, trsvcid, host_traddr.
> I will rename to host_iface at your suggestion.
> 
> Q2) Is this valid for all transports? I guess it would only work for 'tcp', and maybe 'rdma' if one
> would be running ROCE. Shouldn't we error out on other transports like 'fc' or 'loop'?
> A2) This is only for TCP, and we do check that this option is only allowed for TCP by specifying it
> in the "allowed_opts" as follows (see file tcp.c):
> 
> static struct nvmf_transport_ops nvme_tcp_transport = {
>          .name           = "tcp",
>          .module         = THIS_MODULE,
>          .required_opts  = NVMF_OPT_TRADDR,
>          .allowed_opts   = NVMF_OPT_TRSVCID | NVMF_OPT_RECONNECT_DELAY |
>                            NVMF_OPT_HOST_TRADDR | NVMF_OPT_CTRL_LOSS_TMO |
>                            NVMF_OPT_HDR_DIGEST | NVMF_OPT_DATA_DIGEST |
>                            NVMF_OPT_NR_WRITE_QUEUES | NVMF_OPT_NR_POLL_QUEUES |
>                            NVMF_OPT_TOS | NVMF_OPT_HOST_TRIFACE,
>          .create_ctrl    = nvme_tcp_create_ctrl,
> };
>
Right, okay.

> Q3) Normally the options are just parts of the 'address' string; why didn't
> you use that approach here?
> A3) I don't understand what you mean?
> 
The 'address' string contains all transport arguments (without the 
transport type), concatenated by a ','.
So the 'host_iface' value should just be added to the address string 
itself, and not added as separate argument to the sysfs printf() call.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
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