netdev - Re: [PATCH bpf-next 1/2] bpf: add BPF_LWT_ENCAP_IP option to bpf_lwt_push

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Date:   Wed, 28 Nov 2018 17:34:10 -0800
From:   Peter Oskolkov <posk@...gle.com>
To:     David Ahern <dsahern@...il.com>
Cc:     ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        posk.devel@...il.com
Subject: Re: [PATCH bpf-next 1/2] bpf: add BPF_LWT_ENCAP_IP option to bpf_lwt_push_encap

On Wed, Nov 28, 2018 at 4:47 PM David Ahern <dsahern@...il.com> wrote:
>
> On 11/28/18 5:22 PM, Peter Oskolkov wrote:
> > diff --git a/net/core/filter.c b/net/core/filter.c
> > index bd0df75dc7b6..17f3c37218e5 100644
> > --- a/net/core/filter.c
> > +++ b/net/core/filter.c
> > @@ -4793,6 +4793,60 @@ static int bpf_push_seg6_encap(struct sk_buff *skb, u32 type, void *hdr, u32 len
> >  }
> >  #endif /* CONFIG_IPV6_SEG6_BPF */
> >
> > +static int bpf_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len)
> > +{
> > +     struct dst_entry *dst;
> > +     struct rtable *rt;
> > +     struct iphdr *iph;
> > +     struct net *net;
> > +     int err;
> > +
> > +     if (skb->protocol != htons(ETH_P_IP))
> > +             return -EINVAL;  /* ETH_P_IPV6 not yet supported */
> > +
> > +     iph = (struct iphdr *)hdr;
> > +
> > +     if (unlikely(len < sizeof(struct iphdr) || len > LWTUNNEL_MAX_ENCAP_HSIZE))
> > +             return -EINVAL;
> > +     if (unlikely(iph->version != 4 || iph->ihl * 4 > len))
> > +             return -EINVAL;
> > +
> > +     if (skb->sk)
> > +             net = sock_net(skb->sk);
> > +     else {
> > +             net = dev_net(skb_dst(skb)->dev);
> > +     }
> > +     rt = ip_route_output(net, iph->daddr, 0, 0, 0);
>
> That is a very limited use case. e.g., oif = 0 means you are not
> considering any kind of policy routing (e.g., VRF).

Hi David! Could you be a bit more specific re: what you would like to
see here? Thanks!