linux-kernel - Re: [PATCH net-next v2] net/packet: Add getsockopt support for PACKET_COPY

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Date: Fri, 8 Mar 2024 13:56:11 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Juntong Deng <juntong.deng@...look.com>
Cc: willemdebruijn.kernel@...il.com, davem@...emloft.net, kuba@...nel.org, 
	pabeni@...hat.com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2] net/packet: Add getsockopt support for PACKET_COPY_THRESH

On Fri, Mar 8, 2024 at 1:43 PM Juntong Deng <juntong.deng@...look.com> wrote:
>
> Currently getsockopt does not support PACKET_COPY_THRESH,
> and we are unable to get the value of PACKET_COPY_THRESH
> socket option through getsockopt.
>
> This patch adds getsockopt support for PACKET_COPY_THRESH.
>
> In addition, this patch converts access to copy_thresh to
> READ_ONCE/WRITE_ONCE.
>
> Signed-off-by: Juntong Deng <juntong.deng@...look.com>
> ---
> V1 -> V2: Use READ_ONCE/WRITE_ONCE.
>
>  net/packet/af_packet.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> index 0db31ca4982d..61270826b9ac 100644
> --- a/net/packet/af_packet.c
> +++ b/net/packet/af_packet.c
> @@ -2318,7 +2318,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
>         }
>         if (po->tp_version <= TPACKET_V2) {
>                 if (macoff + snaplen > po->rx_ring.frame_size) {
> -                       if (po->copy_thresh &&
> +                       if (READ_ONCE(po->copy_thresh) &&
>                             atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf) {
>                                 if (skb_shared(skb)) {
>                                         copy_skb = skb_clone(skb, GFP_ATOMIC);
> @@ -3836,7 +3836,7 @@ packet_setsockopt(struct socket *sock, int level, int optname, sockptr_t optval,
>                 if (copy_from_sockptr(&val, optval, sizeof(val)))
>                         return -EFAULT;
>
> -               pkt_sk(sk)->copy_thresh = val;
> +               WRITE_ONCE(pkt_sk(sk)->copy_thresh, val);
>                 return 0;
>         }
>         case PACKET_VERSION:
> @@ -4090,6 +4090,9 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
>         case PACKET_VNET_HDR_SZ:
>                 val = READ_ONCE(po->vnet_hdr_sz);
>                 break;
> +       case PACKET_COPY_THRESH:
> +               val = READ_ONCE(pkt_sk(sk)->copy_thresh);
> +               break;
>         case PACKET_VERSION:
>                 val = po->tp_version;
>                 break;
> --
> 2.39.2
>

I think you forgot to change net/packet/diag.c pdiag_put_info()