linux-kernel - Re: [PATCH net-next v2 07/12] net: vxlan: add skb drop reasons to vxlan

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Message-ID: <CADxym3YkROBgjbd0-h6nk2nxKkzofjCdJ6k9PLE86BQzKoxKUA@mail.gmail.com>
Date: Sun, 1 Sep 2024 21:02:17 +0800
From: Menglong Dong <menglong8.dong@...il.com>
To: Alexander Lobakin <aleksander.lobakin@...el.com>
Cc: idosch@...dia.com, kuba@...nel.org, davem@...emloft.net, 
	edumazet@...gle.com, pabeni@...hat.com, dsahern@...nel.org, 
	dongml2@...natelecom.cn, amcohen@...dia.com, gnault@...hat.com, 
	bpoirier@...dia.com, b.galvani@...il.com, razor@...ckwall.org, 
	petrm@...dia.com, linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 07/12] net: vxlan: add skb drop reasons to vxlan_rcv()

On Fri, Aug 30, 2024 at 11:04 PM Alexander Lobakin
<aleksander.lobakin@...el.com> wrote:
>
> From: Menglong Dong <menglong8.dong@...il.com>
> Date: Fri, 30 Aug 2024 09:59:56 +0800
>
> > Introduce skb drop reasons to the function vxlan_rcv(). Following new
> > vxlan drop reasons are added:
> >
> >   VXLAN_DROP_INVALID_HDR
> >   VXLAN_DROP_VNI_NOT_FOUND
> >
> > And Following core skb drop reason is added:
>
> "the following", lowercase + "the".
>

Okay!

> >
> >   SKB_DROP_REASON_IP_TUNNEL_ECN
> >
> > Signed-off-by: Menglong Dong <dongml2@...natelecom.cn>
>
> [...]
>
> > @@ -23,6 +25,14 @@ enum vxlan_drop_reason {
> >        * one pointing to a nexthop
> >        */
> >       VXLAN_DROP_ENTRY_EXISTS,
> > +     /**
> > +      * @VXLAN_DROP_INVALID_HDR: the vxlan header is invalid, such as:
>
> Same as before, "VXLAN" in uppercase I'd say.
>
> > +      * 1) the reserved fields are not zero
> > +      * 2) the "I" flag is not set
> > +      */
> > +     VXLAN_DROP_INVALID_HDR,
> > +     /** @VXLAN_DROP_VNI_NOT_FOUND: no vxlan device found for the vni */
>
> ^
>
> > +     VXLAN_DROP_VNI_NOT_FOUND,
> >  };
>
> [...]
>
> >       if (!raw_proto) {
> > -             if (!vxlan_set_mac(vxlan, vs, skb, vni))
> > +             reason = vxlan_set_mac(vxlan, vs, skb, vni);
> > +             if (reason)
> >                       goto drop;
>
> This piece must go in the previous patch, see my comment there.
>

Yeah, I'll do it.

> [...]
>
> > @@ -1814,8 +1830,9 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
> >       return 0;
> >
> >  drop:
> > +     reason = reason ?: SKB_DROP_REASON_NOT_SPECIFIED;
>
> Is this possible that @reason will be 0 (NOT_DROPPED_YET) here? At the
> beginning of the function, it's not initialized, then each error path
> sets it to a specific value. In most paths, you check for it being != 0
> as a sign of error, so I doubt it can be 0 here.
>

It can be 0 here, as we don't set a reason for every "goto drop"
path. For example, in the line:

    if (!vs)
        goto drop;

we don't set a reason, and the "reason" is 0 when we "goto drop",
as I don't think that it is worth introducing a reason here.

Thanks!
Menglong Dong

> >       /* Consume bad packet */
> > -     kfree_skb(skb);
> > +     kfree_skb_reason(skb, reason);
> >       return 0;
> >  }
>
> Thanks,
> Olek