netdev - RE: [RFC PATCH net-next] net: Modify CSUM capability check for USO

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Message-ID:
 <SA1PR12MB81631C34BCAAA27CB25E271E9DD02@SA1PR12MB8163.namprd12.prod.outlook.com>
Date: Wed, 12 Mar 2025 16:59:03 +0000
From: "Radharapu, Rakesh" <Rakesh.Radharapu@....com>
To: Paolo Abeni <pabeni@...hat.com>, "git (AMD-Xilinx)" <git@....com>,
	"davem@...emloft.net" <davem@...emloft.net>, "edumazet@...gle.com"
	<edumazet@...gle.com>, "kuba@...nel.org" <kuba@...nel.org>,
	"horms@...nel.org" <horms@...nel.org>, "kuniyu@...zon.com"
	<kuniyu@...zon.com>, "bigeasy@...utronix.de" <bigeasy@...utronix.de>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Katakam,
 Harini" <harini.katakam@....com>, "Pandey, Radhey Shyam"
	<radhey.shyam.pandey@....com>, "Simek, Michal" <michal.simek@....com>
Subject: RE: [RFC PATCH net-next] net: Modify CSUM capability check for USO

[AMD Official Use Only - AMD Internal Distribution Only]

> -----Original Message-----
> From: Paolo Abeni <pabeni@...hat.com>
> Sent: Wednesday, March 12, 2025 9:44 PM
> To: Radharapu, Rakesh <Rakesh.Radharapu@....com>; git (AMD-Xilinx)
> <git@....com>; davem@...emloft.net; edumazet@...gle.com;
> kuba@...nel.org; horms@...nel.org; kuniyu@...zon.com;
> bigeasy@...utronix.de
> Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org; Katakam, Harini
> <harini.katakam@....com>; Pandey, Radhey Shyam
> <radhey.shyam.pandey@....com>; Simek, Michal
> <michal.simek@....com>
> Subject: Re: [RFC PATCH net-next] net: Modify CSUM capability check for USO
>
> Caution: This message originated from an External Source. Use proper
> caution when opening attachments, clicking links, or responding.
>
>
> On 3/12/25 12:54 PM, Radharapu Rakesh wrote:
> >  net/core/dev.c | 8 +++++---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/net/core/dev.c b/net/core/dev.c index
> > 1cb134ff7327..a22f8f6e2ed1 100644
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -10465,11 +10465,13 @@ static void
> > netdev_sync_lower_features(struct net_device *upper,
> >
> >  static bool netdev_has_ip_or_hw_csum(netdev_features_t features)  {
> > -     netdev_features_t ip_csum_mask = NETIF_F_IP_CSUM |
> NETIF_F_IPV6_CSUM;
> > -     bool ip_csum = (features & ip_csum_mask) == ip_csum_mask;
> > +     netdev_features_t ipv4_csum_mask = NETIF_F_IP_CSUM;
> > +     netdev_features_t ipv6_csum_mask = NETIF_F_IPV6_CSUM;
> > +     bool ipv4_csum = (features & ipv4_csum_mask) == ipv4_csum_mask;
> > +     bool ipv6_csum = (features & ipv6_csum_mask) == ipv6_csum_mask;
> >       bool hw_csum = features & NETIF_F_HW_CSUM;
> >
> > -     return ip_csum || hw_csum;
> > +     return ipv4_csum || ipv6_csum || hw_csum;
> >  }
>
> The above will additionally affect TLS offload, and will likely break i.e. USO
> over IPv6 traffic landing on devices supporting only USO over IPv4, unless
> such devices additionally implement a suitable ndo_features_check().
>
> Such situation will be quite bug prone, I'm unsure we want this kind of change
> - even without looking at the TLS side of it.
>
> /P
Thanks for your review. I understand that this will lead to an issue.
We have a device that supports only IPv4 CSUM and are unable to enable the
USO feature because of this check. Can you please let me know if splitting
GSO feature for IPv4 and IPv6 would be helpful? That way corresponding
CSUM offloads can be checked. But this would be a major change.
Will appreciate any other suggestions.

Regards,
Rakesh