From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@kernel.org>,
netdev@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [PATCH RFC bpf-next 1/2] bpf_redirect_neigh: Support supplying the nexthop as a helper parameter
Date: Mon, 19 Oct 2020 16:56:36 +0200 [thread overview]
Message-ID: <87tuuqe02j.fsf@toke.dk> (raw)
In-Reply-To: <3d90f3aa-fc09-983f-0e5d-81e889d03b54@iogearbox.net>
Daniel Borkmann <daniel@iogearbox.net> writes:
> On 10/15/20 5:46 PM, Toke Høiland-Jørgensen wrote:
>> From: Toke Høiland-Jørgensen <toke@redhat.com>
>>
>> Based on the discussion in [0], update the bpf_redirect_neigh() helper to
>> accept an optional parameter specifying the nexthop information. This makes
>> it possible to combine bpf_fib_lookup() and bpf_redirect_neigh() without
>> incurring a duplicate FIB lookup - since the FIB lookup helper will return
>> the nexthop information even if no neighbour is present, this can simply be
>> passed on to bpf_redirect_neigh() if bpf_fib_lookup() returns
>> BPF_FIB_LKUP_RET_NO_NEIGH.
>>
>> [0] https://lore.kernel.org/bpf/393e17fc-d187-3a8d-2f0d-a627c7c63fca@iogearbox.net/
>>
>> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
>
> Overall looks good from what I can tell, just small nits below on top of
> David's feedback:
>
> [...]
>> -static int __bpf_redirect_neigh_v4(struct sk_buff *skb, struct net_device *dev)
>> +static int __bpf_redirect_neigh_v4(struct sk_buff *skb, struct net_device *dev,
>> + struct bpf_nh_params *nh)
>> {
>> const struct iphdr *ip4h = ip_hdr(skb);
>> struct net *net = dev_net(dev);
>> int err, ret = NET_XMIT_DROP;
>> - struct rtable *rt;
>> - struct flowi4 fl4 = {
>> - .flowi4_flags = FLOWI_FLAG_ANYSRC,
>> - .flowi4_mark = skb->mark,
>> - .flowi4_tos = RT_TOS(ip4h->tos),
>> - .flowi4_oif = dev->ifindex,
>> - .flowi4_proto = ip4h->protocol,
>> - .daddr = ip4h->daddr,
>> - .saddr = ip4h->saddr,
>> - };
>>
>> - rt = ip_route_output_flow(net, &fl4, NULL);
>> - if (IS_ERR(rt))
>> - goto out_drop;
>> - if (rt->rt_type != RTN_UNICAST && rt->rt_type != RTN_LOCAL) {
>> - ip_rt_put(rt);
>> - goto out_drop;
>> - }
>> + if (!nh->nh_family) {
>> + struct rtable *rt;
>> + struct flowi4 fl4 = {
>> + .flowi4_flags = FLOWI_FLAG_ANYSRC,
>> + .flowi4_mark = skb->mark,
>> + .flowi4_tos = RT_TOS(ip4h->tos),
>> + .flowi4_oif = dev->ifindex,
>> + .flowi4_proto = ip4h->protocol,
>> + .daddr = ip4h->daddr,
>> + .saddr = ip4h->saddr,
>> + };
>> +
>> + rt = ip_route_output_flow(net, &fl4, NULL);
>> + if (IS_ERR(rt))
>> + goto out_drop;
>> + if (rt->rt_type != RTN_UNICAST && rt->rt_type != RTN_LOCAL) {
>> + ip_rt_put(rt);
>> + goto out_drop;
>> + }
>>
>> - skb_dst_set(skb, &rt->dst);
>> + skb_dst_set(skb, &rt->dst);
>> + nh = NULL;
>> + }
>>
>> - err = bpf_out_neigh_v4(net, skb);
>> + err = bpf_out_neigh_v4(net, skb, dev, nh);
>> if (unlikely(net_xmit_eval(err)))
>> dev->stats.tx_errors++;
>> else
>> @@ -2355,7 +2383,8 @@ static int __bpf_redirect_neigh_v4(struct sk_buff *skb, struct net_device *dev)
>> }
>> #endif /* CONFIG_INET */
>>
>> -static int __bpf_redirect_neigh(struct sk_buff *skb, struct net_device *dev)
>> +static int __bpf_redirect_neigh(struct sk_buff *skb, struct net_device *dev,
>> + struct bpf_nh_params *nh)
>> {
>> struct ethhdr *ethh = eth_hdr(skb);
>>
>> @@ -2370,9 +2399,9 @@ static int __bpf_redirect_neigh(struct sk_buff *skb, struct net_device *dev)
>> skb_reset_network_header(skb);
>>
>> if (skb->protocol == htons(ETH_P_IP))
>> - return __bpf_redirect_neigh_v4(skb, dev);
>> + return __bpf_redirect_neigh_v4(skb, dev, nh);
>> else if (skb->protocol == htons(ETH_P_IPV6))
>> - return __bpf_redirect_neigh_v6(skb, dev);
>> + return __bpf_redirect_neigh_v6(skb, dev, nh);
>> out:
>> kfree_skb(skb);
>> return -ENOTSUPP;
>> @@ -2455,8 +2484,8 @@ int skb_do_redirect(struct sk_buff *skb)
>> return -EAGAIN;
>> }
>> return flags & BPF_F_NEIGH ?
>> - __bpf_redirect_neigh(skb, dev) :
>> - __bpf_redirect(skb, dev, flags);
>> + __bpf_redirect_neigh(skb, dev, &ri->nh) :
>> + __bpf_redirect(skb, dev, flags);
>> out_drop:
>> kfree_skb(skb);
>> return -EINVAL;
>> @@ -2504,16 +2533,23 @@ static const struct bpf_func_proto bpf_redirect_peer_proto = {
>> .arg2_type = ARG_ANYTHING,
>> };
>>
>> -BPF_CALL_2(bpf_redirect_neigh, u32, ifindex, u64, flags)
>> +BPF_CALL_4(bpf_redirect_neigh, u32, ifindex, struct bpf_redir_neigh *, params,
>> + int, plen, u64, flags)
>> {
>> struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
>>
>> - if (unlikely(flags))
>> + if (unlikely((plen && plen < sizeof(*params)) || flags))
>> return TC_ACT_SHOT;
>>
>> ri->flags = BPF_F_NEIGH;
>> ri->tgt_index = ifindex;
>>
>> + BUILD_BUG_ON(sizeof(struct bpf_redir_neigh) != sizeof(struct bpf_nh_params));
>> + if (plen)
>> + memcpy(&ri->nh, params, sizeof(ri->nh));
>> + else
>> + ri->nh.nh_family = 0; /* clear previous value */
>
> I'd probably just add an internal flag and do ...
>
> ri->flags = BPF_F_NEIGH | (plen ? BPF_F_NEXTHOP : 0);
>
> ... instead of above clearing, and skb_do_redirect() then becomes:
>
> __bpf_redirect_neigh(skb, dev, flags & BPF_F_NEXTHOP ? &ri->nh : NULL)
>
> ... which would then also avoid this !nh->nh_family check where you later on
> set nh = NULL to pass it onwards.
Ah yes, excellent idea! Will fix :)
-Toke
next prev parent reply other threads:[~2020-10-19 14:56 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-15 15:46 [PATCH RFC bpf-next 0/2] bpf: Rework bpf_redirect_neigh() to allow supplying nexthop from caller Toke Høiland-Jørgensen
2020-10-15 15:46 ` [PATCH RFC bpf-next 1/2] bpf_redirect_neigh: Support supplying the nexthop as a helper parameter Toke Høiland-Jørgensen
2020-10-15 16:27 ` David Ahern
2020-10-15 19:34 ` Toke Høiland-Jørgensen
2020-10-19 13:09 ` Daniel Borkmann
2020-10-19 13:28 ` Toke Høiland-Jørgensen
2020-10-19 14:48 ` Daniel Borkmann
2020-10-19 14:56 ` Toke Høiland-Jørgensen [this message]
2020-10-19 15:01 ` Daniel Borkmann
2020-10-15 15:46 ` [PATCH RFC bpf-next 2/2] selftests: Update test_tc_neigh to use the modified bpf_redirect_neigh() Toke Høiland-Jørgensen
2020-10-19 14:40 ` Daniel Borkmann
2020-10-19 14:48 ` Toke Høiland-Jørgensen
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