netdev - Re: [PATCH net-next v15] openvswitch: enable NSH support

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Date:   Tue, 7 Nov 2017 02:57:30 -0800
From:   Pravin Shelar <pshelar@....org>
To:     Jiri Benc <jbenc@...hat.com>
Cc:     Yi Yang <yi.y.yang@...el.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        ovs dev <dev@...nvswitch.org>, Eric Garver <e@...g.me>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH net-next v15] openvswitch: enable NSH support

On Mon, Nov 6, 2017 at 4:22 AM, Jiri Benc <jbenc@...hat.com> wrote:
> On Sat, 4 Nov 2017 07:29:46 -0700, Pravin Shelar wrote:
>> > +int nsh_push(struct sk_buff *skb, const struct nshhdr *pushed_nh)
>> > +{
>> > +       struct nshhdr *nh;
>> > +       size_t length = nsh_hdr_len(pushed_nh);
>> > +       u8 next_proto;
>> > +
>> > +       if (skb->mac_len) {
>> > +               next_proto = TUN_P_ETHERNET;
>> > +       } else {
>> > +               next_proto = tun_p_from_eth_p(skb->protocol);
>> > +               if (!next_proto)
>> > +                       return -EAFNOSUPPORT;
>> check for supported protocols can be moved to flow install validation
>> in __ovs_nla_copy_actions().
>
> You mean the check for !next_proto? It needs to be present for
> correctness of nsh_push. This function has to be self contained, it
> will be used by more callers than opevswitch, namely tc.
>
> It's actually not so much a check for "supported protocols", it's
> rather a check of return value of a function that converts ethertype to
> a 1 byte tunnel type. Blindly using a result of a function that may
> return error would be wrong. Openvswitch is free to perform additional
> checks but this needs to stay.
>
I am not disputing validity of the checks, but it could be done at
flow install phase.
For other use case we could refactor code. If it is too complex, I am
fine with duplicate code that check the protocol in flow install for
now.

>> > +int nsh_pop(struct sk_buff *skb)
>> > +{
>> > +       struct nshhdr *nh;
>> > +       size_t length;
>> > +       __be16 inner_proto;
>> > +
>> > +       if (!pskb_may_pull(skb, NSH_BASE_HDR_LEN))
>> > +               return -ENOMEM;
>> > +       nh = (struct nshhdr *)(skb->data);
>> > +       length = nsh_hdr_len(nh);
>> > +       inner_proto = tun_p_to_eth_p(nh->np);
>> same as above, this check can be moved to flow install __ovs_nla_copy_actions().
>
> There's no check here.
>
>> > +       if (!pskb_may_pull(skb, length))
>> > +               return -ENOMEM;
>> > +
>> > +       if (!inner_proto)
>> > +               return -EAFNOSUPPORT;
>
> Did you mean this one instead? Then see above, this has to stay.
>
>  Jiri