netdev - Re: [PATCH net-next v3 2/2] net: flow_dissector: Parse PTP L2 packet header

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Date:   Tue, 12 Jan 2021 05:49:41 -0800
From:   Richard Cochran <richardcochran@...il.com>
To:     Eran Ben Elisha <eranbe@...dia.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        Tariq Toukan <tariqt@...dia.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Jiri Pirko <jiri@...dia.com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Guillaume Nault <gnault@...hat.com>,
        Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH net-next v3 2/2] net: flow_dissector: Parse PTP L2 packet
 header

On Mon, Jan 11, 2021 at 08:17:48PM +0200, Eran Ben Elisha wrote:
> Add support for parsing PTP L2 packet header. Such packet consists
> of an L2 header (with ethertype of ETH_P_1588), PTP header, body
> and an optional suffix.
> 
> Signed-off-by: Eran Ben Elisha <eranbe@...dia.com>
> Reviewed-by: Tariq Toukan <tariqt@...dia.com>
> ---
>  net/core/flow_dissector.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
> index 6f1adba6695f..fcaa223c7cdc 100644
> --- a/net/core/flow_dissector.c
> +++ b/net/core/flow_dissector.c
> @@ -23,6 +23,7 @@
>  #include <linux/if_ether.h>
>  #include <linux/mpls.h>
>  #include <linux/tcp.h>
> +#include <linux/ptp_classify.h>
>  #include <net/flow_dissector.h>
>  #include <scsi/fc/fc_fcoe.h>
>  #include <uapi/linux/batadv_packet.h>
> @@ -1251,6 +1252,21 @@ bool __skb_flow_dissect(const struct net *net,
>  						  &proto, &nhoff, hlen, flags);
>  		break;
>  
> +	case htons(ETH_P_1588): {
> +		struct ptp_header *hdr, _hdr;
> +
> +		hdr = __skb_header_pointer(skb, nhoff, sizeof(_hdr), data,
> +					   hlen, &_hdr);
> +		if (!hdr || (hlen - nhoff) < sizeof(_hdr)) {

I'm not really familiar with the flow dissector, but why check (hlen - nhoff) here?
None of the other cases do that.  Doesn't skb_copy_bits() in
__skb_header_pointer() already handle that?

Thanks,
Richard


> +			fdret = FLOW_DISSECT_RET_OUT_BAD;
> +			break;
> +		}
> +
> +		nhoff += ntohs(hdr->message_length);
> +		fdret = FLOW_DISSECT_RET_OUT_GOOD;
> +		break;
> +	}
> +
>  	default:
>  		fdret = FLOW_DISSECT_RET_OUT_BAD;
>  		break;
> -- 
> 2.17.1
>