Re: [PATCH v2 2/3] nvme-tcp: support IPv6 traffic class

[Geliang Tang <geliang@kernel.org>]

Hi Stanislav,

On Mon, 2026-08-10 at 17:32 -0700, Stanislav Fomichev wrote:
> On 08/08, Geliang Tang wrote:
> > From: Geliang Tang <tanggeliang@kylinos.cn>
> > 
> > The NVMe/TCP transport needs to configure the IPv6 traffic class on
> > its
> > queue sockets, but the fabrics option parser currently has no
> > corresponding
> > option.
> > 
> > Add the tclass option to the fabrics parser and store the validated
> > value
> > in struct nvmf_ctrl_options. Negative values are rejected, while
> > values
> > greater than 255 are clamped to 255, matching the valid range of
> > the IPv6
> > traffic class field.
> > 
> > Keep -1 as the default value to let the transport use its default
> > traffic
> > class.
> > 
> > The fabrics layer now supports parsing the tclass option, but the
> > NVMe/TCP
> > transport does not currently advertise or apply it.
> > 
> > Allow NVMe/TCP to use NVMF_OPT_TCLASS and set IPV6_TCLASS on each
> > queue
> > socket via ip6_sock_set_tclass() when a traffic class is specified,
> > keeping
> > the existing IPv4 TOS handling unchanged.
> > 
> > Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
> > ---
> >  drivers/nvme/host/fabrics.c | 18 ++++++++++++++++++
> >  drivers/nvme/host/fabrics.h |  3 +++
> >  drivers/nvme/host/tcp.c     |  8 +++++++-
> >  3 files changed, 28 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/nvme/host/fabrics.c
> > b/drivers/nvme/host/fabrics.c
> > index ac3d4f400601..643c03dc7bcb 100644
> > --- a/drivers/nvme/host/fabrics.c
> > +++ b/drivers/nvme/host/fabrics.c
> > @@ -695,6 +695,7 @@ static const match_table_t opt_tokens = {
> >  	{ NVMF_OPT_NR_WRITE_QUEUES,	"nr_write_queues=%d"	},
> >  	{ NVMF_OPT_NR_POLL_QUEUES,	"nr_poll_queues=%d"	},
> >  	{
> > NVMF_OPT_TOS,			"tos=%d"		},
> > +	{ NVMF_OPT_TCLASS,		"tclass=%d"		},
> 
> Do you really need new UAPI for v6? Any reason not to apply existing
> NVMF_OPT_TOS to ipv6 sockets?

Thanks for the feedback. I've given this careful consideration, and
you're absolutely right - there's no strong reason to introduce new
UAPI specifically for IPv6 when the existing NVMF_OPT_TOS can be
reused. I'll reuse it for IPv6 in v3 and drop this new "tclass" option.

Thanks,
-Geliang