From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Ahern <dsahern@gmail.com>
Subject: Re: [RFC bpf-next 8/9] bpf: Provide helper to do lookups in kernel
 FIB table
Date: Fri, 27 Apr 2018 10:49:35 -0600
Message-ID: <c5cf74c1-fae0-f8ff-4679-df0e6cf4d334@gmail.com>
References: <20180425183449.25134-1-dsahern@gmail.com>
 <20180425183449.25134-9-dsahern@gmail.com>
 <20180427164303.qxodjc63i6pf75q6@kafai-mbp>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Cc: netdev@vger.kernel.org, borkmann@iogearbox.net, ast@kernel.org,
        shm@cumulusnetworks.com, roopa@cumulusnetworks.com,
        brouer@redhat.com, toke@toke.dk, john.fastabend@gmail.com
To: Martin KaFai Lau <kafai@fb.com>
Return-path: <netdev-owner@vger.kernel.org>
Received: from mail-pf0-f195.google.com ([209.85.192.195]:43173 "EHLO
        mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1758554AbeD0Qti (ORCPT
        <rfc822;netdev@vger.kernel.org>); Fri, 27 Apr 2018 12:49:38 -0400
Received: by mail-pf0-f195.google.com with SMTP id j11so1881881pff.10
        for <netdev@vger.kernel.org>; Fri, 27 Apr 2018 09:49:38 -0700 (PDT)
In-Reply-To: <20180427164303.qxodjc63i6pf75q6@kafai-mbp>
Content-Language: en-US
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

On 4/27/18 10:43 AM, Martin KaFai Lau wrote:
>> +#if IS_ENABLED(CONFIG_IPV6)
>> +static int bpf_ipv6_fib_lookup(struct xdp_buff *ctx,
>> +			       struct bpf_fib_lookup *params, u32 flags)
>> +{
>> +	struct net *net = dev_net(ctx->rxq->dev);
>> +	struct neighbour *neigh;
>> +	struct net_device *dev;
>> +	struct fib6_info *f6i;
>> +	struct flowi6 fl6;
>> +	int strict = 0;
>> +	int oif;
>> +
>> +	/* link local addresses are never forwarded */
>> +	if (rt6_need_strict(&params->ipv6_dst) ||
>> +	    rt6_need_strict(&params->ipv6_src))
>> +		return 0;
>> +
>> +	dev = dev_get_by_index_rcu(net, params->ifindex);
>> +	if (unlikely(!dev))
>> +		return -ENODEV;
>> +
>> +	if (flags & BPF_FIB_LOOKUP_OUTPUT) {
>> +		fl6.flowi6_iif = 1;
> 1 is for LOOPBACK_IFINDEX?

yes. The intention is to mirror the flow struct created by full stack so
that routing in bpf == routing in IPv6 stack. ip6_route_output_flags
sets flowi6_iif to 1, so I repeated it here.

> 
>> +		oif = fl6.flowi6_oif = params->ifindex;
>> +	} else {
>> +		oif = fl6.flowi6_iif = params->ifindex;
>> +		fl6.flowi6_oif = 0;
>> +		strict = RT6_LOOKUP_F_HAS_SADDR;
>> +	}