linux-kernel - Re: [PATCH net-next v2 06/12] net: vxlan: make vxlan_set

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Message-ID: <CADxym3b6h6wKTsW3U8pLm+hy0BksggRwG4s9A0qLszRYg1Ze-g@mail.gmail.com>
Date: Sun, 1 Sep 2024 20:56:08 +0800
From: Menglong Dong <menglong8.dong@...il.com>
To: Alexander Lobakin <aleksander.lobakin@...el.com>
Cc: kuba@...nel.org, idosch@...dia.com, 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 06/12] net: vxlan: make vxlan_set_mac() return
 drop reasons

On Fri, Aug 30, 2024 at 10:58 PM Alexander Lobakin
<aleksander.lobakin@...el.com> wrote:
>
> From: Menglong Dong <menglong8.dong@...il.com>
> Date: Fri, 30 Aug 2024 09:59:55 +0800
>
> > Change the return type of vxlan_set_mac() from bool to enum
> > skb_drop_reason. In this commit, two drop reasons are introduced:
> >
> >   VXLAN_DROP_INVALID_SMAC
> >   VXLAN_DROP_ENTRY_EXISTS
> >
> > To make it easier to document the reasons in drivers/net/vxlan/drop.h,
> > we don't define the enum vxlan_drop_reason with the macro
> > VXLAN_DROP_REASONS(), but hand by hand.
> >
> > Signed-off-by: Menglong Dong <dongml2@...natelecom.cn>
> > ---
> >  drivers/net/vxlan/drop.h       |  9 +++++++++
> >  drivers/net/vxlan/vxlan_core.c | 12 ++++++------
> >  2 files changed, 15 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/net/vxlan/drop.h b/drivers/net/vxlan/drop.h
> > index 6bcc6894fbbd..876b4a9de92f 100644
> > --- a/drivers/net/vxlan/drop.h
> > +++ b/drivers/net/vxlan/drop.h
> > @@ -9,11 +9,20 @@
> >  #include <net/dropreason.h>
> >
> >  #define VXLAN_DROP_REASONS(R)                        \
> > +     R(VXLAN_DROP_INVALID_SMAC)              \
> > +     R(VXLAN_DROP_ENTRY_EXISTS)              \
>
> To Jakub:
>
> In our recent conversation, you said you dislike templates much. What
> about this one? :>
>
> >       /* deliberate comment for trailing \ */
> >
> >  enum vxlan_drop_reason {
> >       __VXLAN_DROP_REASON = SKB_DROP_REASON_SUBSYS_VXLAN <<
> >                               SKB_DROP_REASON_SUBSYS_SHIFT,
> > +     /** @VXLAN_DROP_INVALID_SMAC: source mac is invalid */
> > +     VXLAN_DROP_INVALID_SMAC,
> > +     /**
> > +      * @VXLAN_DROP_ENTRY_EXISTS: trying to migrate a static entry or
> > +      * one pointing to a nexthop
> > +      */
>
> Maybe you'd do a proper kdoc for this enum at the top?
>

Do you mean the enum vxlan_drop_reason? Yeah, that makes
sense, and I'll doc it.

> > +     VXLAN_DROP_ENTRY_EXISTS,
> >  };
> >
> >  static inline void
> > diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
> > index 76b217d166ef..58c175432a15 100644
> > --- a/drivers/net/vxlan/vxlan_core.c
> > +++ b/drivers/net/vxlan/vxlan_core.c
> > @@ -1607,9 +1607,9 @@ static void vxlan_parse_gbp_hdr(struct vxlanhdr *unparsed,
> >       unparsed->vx_flags &= ~VXLAN_GBP_USED_BITS;
> >  }
> >
> > -static bool vxlan_set_mac(struct vxlan_dev *vxlan,
> > -                       struct vxlan_sock *vs,
> > -                       struct sk_buff *skb, __be32 vni)
> > +static enum skb_drop_reason vxlan_set_mac(struct vxlan_dev *vxlan,
> > +                                       struct vxlan_sock *vs,
> > +                                       struct sk_buff *skb, __be32 vni)
> >  {
> >       union vxlan_addr saddr;
> >       u32 ifindex = skb->dev->ifindex;
> > @@ -1620,7 +1620,7 @@ static bool vxlan_set_mac(struct vxlan_dev *vxlan,
> >
> >       /* Ignore packet loops (and multicast echo) */
> >       if (ether_addr_equal(eth_hdr(skb)->h_source, vxlan->dev->dev_addr))
> > -             return false;
> > +             return (u32)VXLAN_DROP_INVALID_SMAC;
> >
> >       /* Get address from the outer IP header */
> >       if (vxlan_get_sk_family(vs) == AF_INET) {
> > @@ -1635,9 +1635,9 @@ static bool vxlan_set_mac(struct vxlan_dev *vxlan,
> >
> >       if ((vxlan->cfg.flags & VXLAN_F_LEARN) &&
> >           vxlan_snoop(skb->dev, &saddr, eth_hdr(skb)->h_source, ifindex, vni))
> > -             return false;
> > +             return (u32)VXLAN_DROP_ENTRY_EXISTS;
> >
> > -     return true;
> > +     return (u32)SKB_NOT_DROPPED_YET;
>
> Redundant cast.
>

Oops, I'll remove it.

> >  }
>
> Don't you need to adjust the call site accordingly? Previously, this
> function returned false in case of error and true otherwise, now it
> returns a non-zero in case of error and 0 (NOT_DROPPED_YET == 0) if
> everything went fine.
> IOW the call site now needs to check whether the return value !=
> NOT_DROPPED_YET instead of checking whether it returned false. You
> inverted the return code logic, but didn't touch the call site.
>

Yeah, you are right. I need to change the call of this function
in this patch too, rather than the next patch. Thanks for reminding
me of this point!

> >
> >  static bool vxlan_ecn_decapsulate(struct vxlan_sock *vs, void *oiph,
>
> Thanks,
> Olek