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From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Jesper Dangaard Brouer <brouer@redhat.com>,
	Hangbin Liu <liuhangbin@gmail.com>
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
	Jiri Benc <jbenc@redhat.com>,
	Eelco Chaudron <echaudro@redhat.com>,
	ast@kernel.org, Daniel Borkmann <daniel@iogearbox.net>,
	Lorenzo Bianconi <lorenzo.bianconi@redhat.com>,
	brouer@redhat.com
Subject: Re: [PATCHv4 bpf-next 1/2] xdp: add a new helper for dev map multicast support
Date: Wed, 10 Jun 2020 12:29:35 +0200
Message-ID: <87d0678b8w.fsf@toke.dk> (raw)
In-Reply-To: <20200610122153.76d30e37@carbon>

Jesper Dangaard Brouer <brouer@redhat.com> writes:

> On Tue, 26 May 2020 22:05:38 +0800
> Hangbin Liu <liuhangbin@gmail.com> wrote:
>
>> diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
>> index a51d9fb7a359..ecc5c44a5bab 100644
>> --- a/kernel/bpf/devmap.c
>> +++ b/kernel/bpf/devmap.c
> [...]
>
>> +int dev_map_enqueue_multi(struct xdp_buff *xdp, struct net_device *dev_rx,
>> +			  struct bpf_map *map, struct bpf_map *ex_map,
>> +			  bool exclude_ingress)
>> +{
>> +	struct bpf_dtab_netdev *obj = NULL;
>> +	struct xdp_frame *xdpf, *nxdpf;
>> +	struct net_device *dev;
>> +	bool first = true;
>> +	u32 key, next_key;
>> +	int err;
>> +
>> +	devmap_get_next_key(map, NULL, &key);
>> +
>> +	xdpf = convert_to_xdp_frame(xdp);
>> +	if (unlikely(!xdpf))
>> +		return -EOVERFLOW;
>> +
>> +	for (;;) {
>> +		switch (map->map_type) {
>> +		case BPF_MAP_TYPE_DEVMAP:
>> +			obj = __dev_map_lookup_elem(map, key);
>> +			break;
>> +		case BPF_MAP_TYPE_DEVMAP_HASH:
>> +			obj = __dev_map_hash_lookup_elem(map, key);
>> +			break;
>> +		default:
>> +			break;
>> +		}
>> +
>> +		if (!obj || dev_in_exclude_map(obj, ex_map,
>> +					       exclude_ingress ? dev_rx->ifindex : 0))
>> +			goto find_next;
>> +
>> +		dev = obj->dev;
>> +
>> +		if (!dev->netdev_ops->ndo_xdp_xmit)
>> +			goto find_next;
>> +
>> +		err = xdp_ok_fwd_dev(dev, xdp->data_end - xdp->data);
>> +		if (unlikely(err))
>> +			goto find_next;
>> +
>> +		if (!first) {
>> +			nxdpf = xdpf_clone(xdpf);
>> +			if (unlikely(!nxdpf))
>> +				return -ENOMEM;
>> +
>> +			bq_enqueue(dev, nxdpf, dev_rx);
>> +		} else {
>> +			bq_enqueue(dev, xdpf, dev_rx);
>
> This looks racy.  You enqueue the original frame, and then later
> xdpf_clone it.  The original frame might have been freed at that
> point.

This was actually my suggestion; on the assumption that bq_enqueue()
just puts the frame on a list that won't be flushed until we exit the
NAPI loop.

But I guess now that you mention it that bq_enqueue() may flush the
queue, so you're right that this won't work. Sorry about that, Hangbin :/

Jesper, the reason I suggested this was to avoid an "extra" copy (i.e.,
if we have two destinations, ideally we should only clone once instead
of twice). Got any clever ideas for a safe way to achieve this? :)

-Toke


  reply index

Thread overview: 94+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-15  8:54 [RFC PATCH bpf-next 0/2] xdp: add " Hangbin Liu
2020-04-15  8:54 ` [RFC PATCH bpf-next 1/2] " Hangbin Liu
2020-04-20  9:52   ` Hangbin Liu
2020-04-15  8:54 ` [RFC PATCH bpf-next 2/2] sample/bpf: add xdp_redirect_map_multicast test Hangbin Liu
2020-04-24  8:56 ` [RFC PATCHv2 bpf-next 0/2] xdp: add dev map multicast support Hangbin Liu
2020-04-24  8:56   ` [RFC PATCHv2 bpf-next 1/2] xdp: add a new helper for " Hangbin Liu
2020-04-24 14:19     ` Lorenzo Bianconi
2020-04-28 11:09       ` Eelco Chaudron
2020-05-06  9:35       ` Hangbin Liu
2020-04-24 14:34     ` Toke Høiland-Jørgensen
2020-05-06  9:14       ` Hangbin Liu
2020-05-06 10:00         ` Toke Høiland-Jørgensen
2020-05-08  8:53           ` Hangbin Liu
2020-05-08 14:58             ` Toke Høiland-Jørgensen
2020-05-18  8:45       ` Hangbin Liu
2020-05-19 10:15         ` Jesper Dangaard Brouer
2020-05-20  1:24           ` Hangbin Liu
2020-04-24  8:56   ` [RFC PATCHv2 bpf-next 2/2] sample/bpf: add xdp_redirect_map_multicast test Hangbin Liu
2020-04-24 14:21     ` Lorenzo Bianconi
2020-05-23  6:05 ` [PATCHv3 bpf-next 0/2] xdp: add dev map multicast support Hangbin Liu
2020-05-23  6:05   ` [PATCHv3 bpf-next 1/2] xdp: add a new helper for " Hangbin Liu
2020-05-26  7:34     ` kbuild test robot
2020-05-23  6:05   ` [PATCHv3 bpf-next 2/2] sample/bpf: add xdp_redirect_map_multicast test Hangbin Liu
2020-05-26 14:05 ` [PATCHv4 bpf-next 0/2] xdp: add dev map multicast support Hangbin Liu
2020-05-26 14:05   ` [PATCHv4 bpf-next 1/2] xdp: add a new helper for " Hangbin Liu
2020-05-27 10:29     ` Toke Høiland-Jørgensen
2020-06-10 10:18     ` Jesper Dangaard Brouer
2020-06-12  8:54       ` Hangbin Liu
2020-06-16  8:55         ` Jesper Dangaard Brouer
2020-06-16 10:11           ` Hangbin Liu
2020-06-16 14:38             ` Jesper Dangaard Brouer
2020-06-10 10:21     ` Jesper Dangaard Brouer
2020-06-10 10:29       ` Toke Høiland-Jørgensen [this message]
2020-06-16  9:04         ` Jesper Dangaard Brouer
2020-05-26 14:05   ` [PATCHv4 bpf-next 2/2] sample/bpf: add xdp_redirect_map_multicast test Hangbin Liu
2020-05-27 10:21   ` [PATCHv4 bpf-next 0/2] xdp: add dev map multicast support Toke Høiland-Jørgensen
2020-05-27 10:32     ` Eelco Chaudron
2020-05-27 12:38     ` Hangbin Liu
2020-05-27 15:04       ` Toke Høiland-Jørgensen
2020-06-16  9:09         ` Jesper Dangaard Brouer
2020-06-16  9:47           ` Hangbin Liu
2020-06-03  2:40     ` Hangbin Liu
2020-06-03 11:05       ` Toke Høiland-Jørgensen
2020-06-04  4:09         ` Hangbin Liu
2020-06-04  9:44           ` Toke Høiland-Jørgensen
2020-06-04 12:12             ` Hangbin Liu
2020-06-04 12:37               ` Toke Høiland-Jørgensen
2020-06-04 14:41                 ` Hangbin Liu
2020-06-04 16:02                   ` Toke Høiland-Jørgensen
2020-06-05  6:26                     ` Hangbin Liu
2020-06-08 15:32                       ` Toke Høiland-Jørgensen
2020-06-09  3:03                         ` Hangbin Liu
2020-06-09 20:31                           ` Toke Høiland-Jørgensen
2020-06-10  2:35                             ` Hangbin Liu
2020-06-10 10:03                               ` Jesper Dangaard Brouer
2020-07-01  4:19   ` [PATCHv5 bpf-next 0/3] xdp: add a new helper for " Hangbin Liu
2020-07-01  4:19     ` [PATCHv5 bpf-next 1/3] " Hangbin Liu
2020-07-01  5:09       ` Andrii Nakryiko
2020-07-01  6:51         ` Hangbin Liu
2020-07-01 18:33       ` kernel test robot
2020-07-01  4:19     ` [PATCHv5 bpf-next 2/3] sample/bpf: add xdp_redirect_map_multicast test Hangbin Liu
2020-07-01  4:19     ` [PATCHv5 bpf-next 3/3] selftests/bpf: add xdp_redirect_multi test Hangbin Liu
2020-07-09  1:30     ` [PATCHv6 bpf-next 0/3] xdp: add a new helper for dev map multicast support Hangbin Liu
2020-07-09  1:30       ` [PATCHv6 bpf-next 1/3] " Hangbin Liu
2020-07-09 16:33         ` David Ahern
2020-07-10  6:55           ` Hangbin Liu
2020-07-10 13:46             ` David Ahern
2020-07-11  0:26               ` Hangbin Liu
2020-07-11 16:09                 ` David Ahern
2020-07-09  1:30       ` [PATCHv6 bpf-next 2/3] sample/bpf: add xdp_redirect_map_multicast test Hangbin Liu
2020-07-09 22:40         ` Daniel Borkmann
2020-07-10  6:41           ` Hangbin Liu
2020-07-10 14:32             ` Daniel Borkmann
2020-07-11  0:21               ` Hangbin Liu
2020-07-09  1:30       ` [PATCHv6 bpf-next 3/3] selftests/bpf: add xdp_redirect_multi test Hangbin Liu
2020-07-09 22:37       ` [PATCHv6 bpf-next 0/3] xdp: add a new helper for dev map multicast support Daniel Borkmann
2020-07-10  7:36         ` Hangbin Liu
2020-07-10 15:02           ` Daniel Borkmann
2020-07-10 16:52             ` David Ahern
2020-07-14  6:32       ` [PATCHv7 " Hangbin Liu
2020-07-14  6:32         ` [PATCHv7 bpf-next 1/3] " Hangbin Liu
2020-07-14 21:52           ` Toke Høiland-Jørgensen
2020-07-15 12:25             ` Hangbin Liu
2020-07-14  6:32         ` [PATCHv7 bpf-next 2/3] sample/bpf: add xdp_redirect_map_multicast test Hangbin Liu
2020-07-14  6:32         ` [PATCHv7 bpf-next 3/3] selftests/bpf: add xdp_redirect_multi test Hangbin Liu
2020-07-14 12:29         ` [PATCHv7 bpf-next 0/3] xdp: add a new helper for dev map multicast support Toke Høiland-Jørgensen
2020-07-14 17:12           ` David Ahern
2020-07-14 21:53             ` Toke Høiland-Jørgensen
2020-07-15 12:31               ` Hangbin Liu
2020-07-15  3:45             ` Hangbin Liu
2020-07-15 13:08         ` [PATCHv8 " Hangbin Liu
2020-07-15 13:08           ` [PATCHv8 bpf-next 1/3] " Hangbin Liu
2020-07-15 13:08           ` [PATCHv8 bpf-next 2/3] sample/bpf: add xdp_redirect_map_multicast test Hangbin Liu
2020-07-15 13:08           ` [PATCHv8 bpf-next 3/3] selftests/bpf: add xdp_redirect_multi test Hangbin Liu

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