netdev - Re: [PATCH net-next v2 08/12] selftests: ncdevmem: Use YNL to enable TCP header split

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Message-ID: <CAHS8izMm8kibMU912thkhB9WC=z6SrkfqAkvXeW6Tj9UsGrQSg@mail.gmail.com>
Date: Thu, 3 Oct 2024 00:22:05 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: Stanislav Fomichev <sdf@...ichev.me>
Cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com
Subject: Re: [PATCH net-next v2 08/12] selftests: ncdevmem: Use YNL to enable
 TCP header split

On Mon, Sep 30, 2024 at 10:18 AM Stanislav Fomichev <sdf@...ichev.me> wrote:
>
> In the next patch the hard-coded queue numbers are gonna be removed.
> So introduce some initial support for ethtool YNL and use
> it to enable header split.
>
> Also, tcp-data-split requires latest ethtool which is unlikely
> to be present in the distros right now.
>
> (ideally, we should not shell out to ethtool at all).
>
> Cc: Mina Almasry <almasrymina@...gle.com>
> Signed-off-by: Stanislav Fomichev <sdf@...ichev.me>
> ---
>  tools/testing/selftests/net/Makefile   |  2 +-
>  tools/testing/selftests/net/ncdevmem.c | 43 ++++++++++++++++++++++++--
>  2 files changed, 42 insertions(+), 3 deletions(-)
>
> diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
> index 649f1fe0dc46..9c970e96ed33 100644
> --- a/tools/testing/selftests/net/Makefile
> +++ b/tools/testing/selftests/net/Makefile
> @@ -112,7 +112,7 @@ TEST_INCLUDES := forwarding/lib.sh
>  include ../lib.mk
>
>  # YNL build
> -YNL_GENS := netdev
> +YNL_GENS := ethtool netdev
>  include ynl.mk
>
>  $(OUTPUT)/epoll_busy_poll: LDLIBS += -lcap
> diff --git a/tools/testing/selftests/net/ncdevmem.c b/tools/testing/selftests/net/ncdevmem.c
> index 48cbf057fde7..a1fa818c8229 100644
> --- a/tools/testing/selftests/net/ncdevmem.c
> +++ b/tools/testing/selftests/net/ncdevmem.c
> @@ -28,10 +28,12 @@
>  #include <linux/netlink.h>
>  #include <linux/genetlink.h>
>  #include <linux/netdev.h>
> +#include <linux/ethtool_netlink.h>
>  #include <time.h>
>  #include <net/if.h>
>
>  #include "netdev-user.h"
> +#include "ethtool-user.h"
>  #include <ynl.h>
>
>  #define PAGE_SHIFT 12
> @@ -217,8 +219,42 @@ static int reset_flow_steering(void)
>
>  static int configure_headersplit(bool on)
>  {
> -       return run_command("sudo ethtool -G %s tcp-data-split %s >&2", ifname,
> -                          on ? "on" : "off");
> +       struct ethtool_rings_set_req *req;
> +       struct ynl_error yerr;
> +       struct ynl_sock *ys;
> +       int ret;
> +
> +       ys = ynl_sock_create(&ynl_ethtool_family, &yerr);
> +       if (!ys) {
> +               fprintf(stderr, "YNL: %s\n", yerr.msg);
> +               return -1;
> +       }
> +
> +       req = ethtool_rings_set_req_alloc();
> +       ethtool_rings_set_req_set_header_dev_index(req, ifindex);
> +       ethtool_rings_set_req_set_tcp_data_split(req, on ? 2 : 0);

I'm guessing 2 is explicit on? 1 being auto probably? A comment would
be nice, but that's just a nit.

> +       ret = ethtool_rings_set(ys, req);
> +       if (ret < 0)
> +               fprintf(stderr, "YNL failed: %s\n", ys->err.msg);

Don't you wanna return ret; here on error?

> +       ethtool_rings_set_req_free(req);
> +
> +       {
> +               struct ethtool_rings_get_req *req;
> +               struct ethtool_rings_get_rsp *rsp;
> +

I'm guessing you're creating a new scope to re-declare req/rsp? To be
honest it's a bit weird style I haven't seen anywhere else. I would
prefer get_req and get_rsp instead, but this is a nit.

> +               req = ethtool_rings_get_req_alloc();
> +               ethtool_rings_get_req_set_header_dev_index(req, ifindex);
> +               rsp = ethtool_rings_get(ys, req);
> +               ethtool_rings_get_req_free(req);
> +               if (rsp)
> +                       fprintf(stderr, "TCP header split: %d\n",
> +                               rsp->tcp_data_split);

I would prefer to cehck that rsp->tcp_data_split == 2 for 'on' and ==
0 for 'off' instead of just printing and relying on the user to notice
the mismatch in the logs.

Consider addressing the feedback, but mostly nits/improvements that
can be done later, so:

Reviewed-by: Mina Almasry <almasrymina@...gle.com>

-- 
Thanks,
Mina