netdev - Re: [PATCH net-next] ethtool: add tunable api to disable various firmware offloads

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Message-ID: <CANP3RGfarvhSFm8UhtJC2gzgigt2wUcBQAoVC+ZRP7zCXH=wtA@mail.gmail.com>
Date: Thu, 15 Aug 2024 17:55:26 -0700
From: Maciej Żenczykowski <maze@...gle.com>
To: "Nelson, Shannon" <shannon.nelson@....com>
Cc: Linux Network Development Mailing List <netdev@...r.kernel.org>, "David S . Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	"Kory Maincent (Dent Project)" <kory.maincent@...tlin.com>, Ahmed Zaki <ahmed.zaki@...el.com>, 
	Edward Cree <ecree.xilinx@...il.com>, Yuyang Huang <yuyanghuang@...gle.com>, 
	Lorenzo Colitti <lorenzo@...gle.com>
Subject: Re: [PATCH net-next] ethtool: add tunable api to disable various
 firmware offloads

On Thu, Aug 15, 2024 at 9:13 AM Nelson, Shannon <shannon.nelson@....com> wrote:
>
> On 8/13/2024 3:33 PM, Maciej Żenczykowski wrote:
> >
> > In order to save power (battery), most network hardware
> > designed for low power environments (ie. battery powered
> > devices) supports varying types of hardware/firmware offload
> > (filtering and/or generating replies) of incoming packets.
> >
> > The goal being to prevent device wakeups caused by ingress 'spam'.
> >
> > This is particularly true for wifi (especially phones/tablets),
> > but isn't actually wifi specific.  It can also be implemented
> > in wired nics (TV) or usb ethernet dongles.
> >
> > For examples TVs require this to keep power consumption
> > under (the EU mandated) 2 Watts while idle (display off),
> > while still being discoverable on the network.
> >
> > This may include things like: ARP/IPv6 ND, IGMP/MLD, ping, mdns,
> > but various other possibilities are also possible,
> > for example:
> >    ethertype filtering (discarding non-IP ethertypes),
> >    nat-t keepalive (discarding ingress, automating periodic egress),
> >    tcp keepalive (generation/processing/filtering),
> >    tethering (forwarding) offload
> >
> > In many ways, in its goals, it is somewhat similar to the
> > relatively standard destination mac filtering most wired nics
> > have supported for ages: reduce the amount of traffic the host
> > must handle.
> >
> > While working on Android we've discovered that there is
> > no device/driver agnostic way to disable these offloads.
> >
> > This patch is an attempt to rectify this.
> >
> > It does not add an API to configure these offloads, as usually
> > this isn't needed as the driver will just fetch the required
> > configuration information straight from the kernel.
> >
> > What it does do is add a simple API to allow disabling (masking)
> > them, either for debugging or for test purposes.
>
> I can see how this would be useful for test/debug, but it seems to me it
> is only half of a solution.  Wouldn't there also be a need to re-enable
> the offloads without having to reboot/restart the gizmo being tested?
> Or even query the current status?

Since it's a mask of things to disable, setting the mask to 0, or the
relevant bit of the mask to 0 would reenable (assuming there was
anything to enable).

>
> sln
>
> >
> > Cc: "Kory Maincent (Dent Project)" <kory.maincent@...tlin.com>
> > Cc: Ahmed Zaki <ahmed.zaki@...el.com>
> > Cc: Edward Cree <ecree.xilinx@...il.com>
> > Cc: "David S. Miller" <davem@...emloft.net>
> > Cc: Eric Dumazet <edumazet@...gle.com>
> > Cc: Jakub Kicinski <kuba@...nel.org>
> > Cc: Paolo Abeni <pabeni@...hat.com>
> > Cc: Yuyang Huang <yuyanghuang@...gle.com>
> > Cc: Lorenzo Colitti <lorenzo@...gle.com>
> > Signed-off-by: Maciej Żenczykowski <maze@...gle.com>
> > ---
> >   include/uapi/linux/ethtool.h | 15 +++++++++++++++
> >   net/ethtool/common.c         |  1 +
> >   net/ethtool/ioctl.c          |  5 +++++
> >   3 files changed, 21 insertions(+)
> >
> > diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h
> > index 4a0a6e703483..7b58860c3731 100644
> > --- a/include/uapi/linux/ethtool.h
> > +++ b/include/uapi/linux/ethtool.h
> > @@ -224,12 +224,27 @@ struct ethtool_value {
> >   #define PFC_STORM_PREVENTION_AUTO      0xffff
> >   #define PFC_STORM_PREVENTION_DISABLE   0
> >
> > +/* For power/wakeup (*not* performance) related offloads */
> > +enum tunable_fw_offload_disable {
> > +       ETHTOOL_TUNABLE_FW_OFFLOAD_DISABLE_ALL,
> > +       ETHTOOL_TUNABLE_FW_OFFLOAD_DISABLE_IPV4_ARP,
> > +       ETHTOOL_TUNABLE_FW_OFFLOAD_DISABLE_IPV6_ND,
> > +       ETHTOOL_TUNABLE_FW_OFFLOAD_DISABLE_IPV4_PING,
> > +       ETHTOOL_TUNABLE_FW_OFFLOAD_DISABLE_IPV6_PING,
> > +       ETHTOOL_TUNABLE_FW_OFFLOAD_DISABLE_IPV4_IGMP,
> > +       ETHTOOL_TUNABLE_FW_OFFLOAD_DISABLE_IPV6_MLD,
> > +       ETHTOOL_TUNABLE_FW_OFFLOAD_DISABLE_IPV4_MDNS,
> > +       ETHTOOL_TUNABLE_FW_OFFLOAD_DISABLE_IPV6_MDNS,
> > +       /* 55 bits remaining for future use */
> > +};
> > +
> >   enum tunable_id {
> >          ETHTOOL_ID_UNSPEC,
> >          ETHTOOL_RX_COPYBREAK,
> >          ETHTOOL_TX_COPYBREAK,
> >          ETHTOOL_PFC_PREVENTION_TOUT, /* timeout in msecs */
> >          ETHTOOL_TX_COPYBREAK_BUF_SIZE,
> > +       ETHTOOL_FW_OFFLOAD_DISABLE, /* u64 bits numbered from LSB per tunable_fw_offload_disable */
> >          /*
> >           * Add your fresh new tunable attribute above and remember to update
> >           * tunable_strings[] in net/ethtool/common.c
> > diff --git a/net/ethtool/common.c b/net/ethtool/common.c
> > index 7257ae272296..8dc0c084fce5 100644
> > --- a/net/ethtool/common.c
> > +++ b/net/ethtool/common.c
> > @@ -91,6 +91,7 @@ tunable_strings[__ETHTOOL_TUNABLE_COUNT][ETH_GSTRING_LEN] = {
> >          [ETHTOOL_TX_COPYBREAK]  = "tx-copybreak",
> >          [ETHTOOL_PFC_PREVENTION_TOUT] = "pfc-prevention-tout",
> >          [ETHTOOL_TX_COPYBREAK_BUF_SIZE] = "tx-copybreak-buf-size",
> > +       [ETHTOOL_FW_OFFLOAD_DISABLE] = "fw-offload-disable",
> >   };
> >
> >   const char
> > diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
> > index 18cf9fa32ae3..31318ded17a7 100644
> > --- a/net/ethtool/ioctl.c
> > +++ b/net/ethtool/ioctl.c
> > @@ -2733,6 +2733,11 @@ static int ethtool_get_module_eeprom(struct net_device *dev,
> >   static int ethtool_tunable_valid(const struct ethtool_tunable *tuna)
> >   {
> >          switch (tuna->id) {
> > +       case ETHTOOL_FW_OFFLOAD_DISABLE:
> > +               if (tuna->len != sizeof(u64) ||
> > +                   tuna->type_id != ETHTOOL_TUNABLE_U64)
> > +                       return -EINVAL;
> > +               break;
> >          case ETHTOOL_RX_COPYBREAK:
> >          case ETHTOOL_TX_COPYBREAK:
> >          case ETHTOOL_TX_COPYBREAK_BUF_SIZE:
> > --
> > 2.46.0.76.ge559c4bf1a-goog
> >
> >

--
Maciej Żenczykowski, Kernel Networking Developer @ Google