[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.

[Sagi Grimberg]

>>>> We already support this for IPv6, we can do that also for IPv4, but
>>>> this syntax may not be trivially expected for ipv4?
>>>
>>> I tried this for IPv6 and it doesn't work. Here's what I get:
>>> $ sudo nvme discover -g -G -t tcp -s 8009 -a fe80::800:27ff:fe00:0
>>> Failed to write to /dev/nvme-fabrics: Invalid argument $ sudo nvme
>>> discover -g -G -t tcp -s 8009 -a fe80::800:27ff:fe00:0%enp0s8 Failed
>>> to write to /dev/nvme-fabrics: Invalid argument $ sudo nvme discover
>>> -g -G -t tcp -s 8009 -a [fe80::800:27ff:fe00:0] failed to resolve host
>>> [fe80::800:27ff:fe00:0] info $ sudo nvme discover -g -G -t tcp -s 8009
>>> -a [fe80::800:27ff:fe00:0%enp0s8] failed to resolve host
>>> [fe80::800:27ff:fe00:0%enp0s8] info
>>
>> # nvme discover -t tcp -a fe80::5054:ff:fef1:9f3b -w
>> fe80::5054:ff:fe28:5edb%enp6s0
> 
> Thanks for clarifying the syntax. However, that doesn't work for me.
> 
> # nvme discover -t tcp -a fe80::800:27ff:fe00:0 -w fe80::9266:4855:6cf2:f7e9%enp0s8
> Failed to write to /dev/nvme-fabrics: Connection refused

Are you using the linux target? connection refused means that
you don't have a listener on it, it's not a resolution error.

did you have the target listen on fe80::800:27ff:fe00:0%<intf> ?

> 
> Note that the above syntax does not comply with RFC4007. The '%' delimiter is supposed to be appended to the Destination IP address and not the Source Address. In other words, to be RFC4007-compliant, the syntax should be (using your example):
> 
> # nvme discover -t tcp -a fe80::5054:ff:fef1:9f3b%enp6s0 -w fe80::5054:ff:fe28:5edb
> 
> This tells nvme-cli to connect to a controller at address fe80::5054:ff:fef1:9f3b using interface enp6s0 for the connection. And set the Source address to fe80::5054:ff:fe28:5edb.

This also seems to work, not sure that it does what we want though...
nvme discover -t tcp -a fe80::5054:ff:fef1:9f3b%enp6s0 -w 
fe80::5054:ff:fe28:5edb%enp6s0

Discovery Log Number of Records 1, Generation counter 5
=====Discovery Log Entry 0======
trtype:  tcp
adrfam:  ipv6
subtype: nvme subsystem
treq:    not specified, sq flow control disable supported
portid:  3
trsvcid: 8009
subnqn:  testnqn1
traddr:  fe80::5054:ff:fef1:9f3b%enp6s0
sectype: none


>> The '%' may be confusing when it comes to other transports as well (e.g.
>> rdma/fc would have to either reject or ignore it, but regardless of how we
>> add it that would be the case). Having host-traddr accept either ip or
>> interface seems the most desirable, however that won't work if there are 2
>> interfaces that share multiple ip addresses. So if this is a requirement we'll
>> probably need to add --host-iface as another option...
> 
> I don’t grok what you mean by "that won't work if there are 2 interfaces that share multiple ip addresses". Why not? If one specifies the interface by its name (e.g. enp0s8), there is no possible confusion even if multiple interfaces share the same IP addresses.
> 
> The following are some examples of how nvme-cli should work to comply with RFC4007 and be consistent to the way ping operates.
> Example 1 - IPv4, Specify Interface with -w and let Linux select Source address:
> nvme discover -t tcp -a 192.168.1.9 -w enp0s8
> 
> Example 2 - IPv4, Specify Interface and Source address with repeated -w:
> nvme discover -t tcp -a 192.168.1.9 -w enp0s8 -w 192.168.56.103

I meant without the repetitions, which you only need if you have 2
devices that share more than one address, which again, is not a clear
use-case to me, but without repetitions we won't support that.

> Example 3 - IPv6, Specify Interface with'%' delimiter and let Linux select Source address:
> nvme discover -t tcp -a fe80::800:27ff:fe00:0%enp0s8
> 
> Example 4 - IPv6, Specify Interface with -w and let Linux select Source address:
> nvme discover -t tcp -a fe80::800:27ff:fe00:0 -w enp0s8
> 
> Example 5 - IPv6, Specify Interface with'%' delimiter and Source address with -w:
> nvme discover -t tcp -a fe80::800:27ff:fe00:0%enp0s8 -w fe80::9266:4855:6cf2:f7e9
> 
> Example 6 - IPv6, Specify Interface and Source address with repeated -w:
> nvme discover -t tcp -a fe80::800:27ff:fe00:0 -w enp0s8 -w fe80::9266:4855:6cf2:f7e9
> 
> Martin
>