Hi Toke,
On Tue, May 22, 2018 at 03:57:38PM +0200, Toke Høiland-Jørgensen wrote:
> When CAKE is deployed on a gateway that also performs NAT (which is a
> common deployment mode), the host fairness mechanism cannot distinguish
> internal hosts from each other, and so fails to work correctly.
>
> To fix this, we add an optional NAT awareness mode, which will query the
> kernel conntrack mechanism to obtain the pre-NAT addresses for each packet
> and use that in the flow and host hashing.
>
> When the shaper is enabled and the host is already performing NAT, the cost
> of this lookup is negligible. However, in unlimited mode with no NAT being
> performed, there is a significant CPU cost at higher bandwidths. For this
> reason, the feature is turned off by default.
>
> Cc: netfilter-devel@xxxxxxxxxxxxxxx
> Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxx>
> ---
> net/sched/sch_cake.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 79 insertions(+)
>
> diff --git a/net/sched/sch_cake.c b/net/sched/sch_cake.c
> index 68ac908470f1..6f7cae705c84 100644
> --- a/net/sched/sch_cake.c
> +++ b/net/sched/sch_cake.c
> @@ -71,6 +71,12 @@
> #include <net/tcp.h>
> #include <net/flow_dissector.h>
>
> +#if IS_REACHABLE(CONFIG_NF_CONNTRACK)
> +#include <net/netfilter/nf_conntrack_core.h>
> +#include <net/netfilter/nf_conntrack_zones.h>
> +#include <net/netfilter/nf_conntrack.h>
> +#endif
> +
> #define CAKE_SET_WAYS (8)
> #define CAKE_MAX_TINS (8)
> #define CAKE_QUEUES (1024)
> @@ -516,6 +522,60 @@ static bool cobalt_should_drop(struct cobalt_vars *vars,
> return drop;
> }
>
> +#if IS_REACHABLE(CONFIG_NF_CONNTRACK)
> +
> +static void cake_update_flowkeys(struct flow_keys *keys,
> + const struct sk_buff *skb)
> +{
> + const struct nf_conntrack_tuple *tuple;
> + enum ip_conntrack_info ctinfo;
> + struct nf_conn *ct;
> + bool rev = false;
> +
> + if (tc_skb_protocol(skb) != htons(ETH_P_IP))
> + return;
> +
> + ct = nf_ct_get(skb, &ctinfo);
> + if (ct) {
> + tuple = nf_ct_tuple(ct, CTINFO2DIR(ctinfo));
> + } else {
> + const struct nf_conntrack_tuple_hash *hash;
> + struct nf_conntrack_tuple srctuple;
> +
> + if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
> + NFPROTO_IPV4, dev_net(skb->dev),
> + &srctuple))
> + return;
> +
> + hash = nf_conntrack_find_get(dev_net(skb->dev),
> + &nf_ct_zone_dflt,
> + &srctuple);
> + if (!hash)
> + return;
> +
> + rev = true;
> + ct = nf_ct_tuplehash_to_ctrack(hash);
> + tuple = nf_ct_tuple(ct, !hash->tuple.dst.dir);
> + }
> +
> + keys->addrs.v4addrs.src = rev ? tuple->dst.u3.ip : tuple->src.u3.ip;
> + keys->addrs.v4addrs.dst = rev ? tuple->src.u3.ip : tuple->dst.u3.ip;
> +
> + if (keys->ports.ports) {
> + keys->ports.src = rev ? tuple->dst.u.all : tuple->src.u.all;
> + keys->ports.dst = rev ? tuple->src.u.all : tuple->dst.u.all;
> + }
> + if (rev)
> + nf_ct_put(ct);
> +}
This is going to pull in the nf_conntrack module, even if you may not
want it, as soon as cake is in place.
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