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Date:   Tue, 28 Mar 2023 19:14:56 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     Ganesh Babu <ganesh.babu@ekinops.com>
Cc:     "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] net: mroute6.h: change type of mif6c_pifi to __u32
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On Tue, 28 Mar 2023 07:13:03 +0000 Ganesh Babu wrote:
> From a91f11fe060729d0009a3271e3a92cead88e2656 Mon Sep 17 00:00:00 2001
> From: "Ganesh Babu" <ganesh.babu@ekinops.com>
> Date: Wed, 15 Mar 2023 15:01:39 +0530
> Subject: [PATCH] net: mroute6.h: change type of mif6c_pifi to __u32
>=20
> Increase mif6c_pifi field in mif6ctl struct
> from 16 to 32 bits to support 32-bit ifindices.
> The field stores the physical interface (ifindex) for a multicast group.
> Passing a 32-bit ifindex via MRT6_ADD_MIF socket option
> from user space can cause unpredictable behavior in PIM6.
> Changing mif6c_pifi to __u32 allows kernel to handle
> 32-bit ifindex values without issues.

The patch is not formatted correctly.
Maybe try git send-email next time?

> diff --git a/include/uapi/linux/mroute6.h b/include/uapi/linux/mroute6.h
> index 1d90c21a6251..90e6e771beab 100644
> --- a/include/uapi/linux/mroute6.h
> +++ b/include/uapi/linux/mroute6.h
> @@ -75,7 +75,7 @@ struct mif6ctl {
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 mifi_t =C2=A0mif6c_mifi; =C2=A0 =C2=A0 =C2=A0=
 =C2=A0 =C2=A0 =C2=A0 /* Index of MIF */
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 unsigned char mif6c_flags; =C2=A0 =C2=A0 =C2=
=A0/* MIFF_ flags */
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 unsigned char vifc_threshold; =C2=A0 /* ttl l=
imit */
> - =C2=A0 =C2=A0 =C2=A0 __u16 =C2=A0 =C2=A0mif6c_pifi; =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0/* the index of the physical IF */
> + =C2=A0 =C2=A0 =C2=A0 __u32 =C2=A0 =C2=A0mif6c_pifi; =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0/* the index of the physical IF */

Unfortunately we can't do this. The structure is part of uAPI,
we can't change it's geometry. The kernel must maintain binary
backward compatibility.=20

> =C2=A0 =C2=A0 =C2=A0 =C2=A0 unsigned int vifc_rate_limit; =C2=A0 /* Rate =
limiter values (NI) */
> =C2=A0};
>=20
> --
> 2.11.0
>=20
> Signed-off-by: Ganesh Babu <ganesh.babu@ekinops.com>
> ---