[Cake] [PATCH net-next v14 4/7] sch_cake: Add NAT awareness to packet classifier

[Toke Høiland-Jørgensen]

On 22 May 2018 01:34:06 CEST, Marcelo Ricardo Leitner <marcelo.leitner at gmail.com> wrote:
>[Cc'ing netfilter-devel@ for awareness]

Thanks! I'll add a Cc in the next version.

>On Mon, May 21, 2018 at 10:35:58PM +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.
>> 
>> Signed-off-by: Toke Høiland-Jørgensen <toke at toke.dk>
>> ---
>>  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 92623160d43e..04364993ce19 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);
>> +}
>> +#else
>> +static void cake_update_flowkeys(struct flow_keys *keys,
>> +				 const struct sk_buff *skb)
>> +{
>> +	/* There is nothing we can do here without CONNTRACK */
>> +}
>> +#endif
>> +
>>  /* Cake has several subtle multiple bit settings. In these cases you
>>   *  would be matching triple isolate mode as well.
>>   */
>> @@ -543,6 +603,9 @@ static u32 cake_hash(struct cake_tin_data *q,
>const struct sk_buff *skb,
>>  	skb_flow_dissect_flow_keys(skb, &keys,
>>  				   FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL);
>>  
>> +	if (flow_mode & CAKE_FLOW_NAT_FLAG)
>> +		cake_update_flowkeys(&keys, skb);
>> +
>>  	/* flow_hash_from_keys() sorts the addresses by value, so we have
>>  	 * to preserve their order in a separate data structure to treat
>>  	 * src and dst host addresses as independently selectable.
>> @@ -1894,6 +1957,18 @@ static int cake_change(struct Qdisc *sch,
>struct nlattr *opt,
>>  	if (err < 0)
>>  		return err;
>>  
>> +	if (tb[TCA_CAKE_NAT]) {
>> +#if IS_REACHABLE(CONFIG_NF_CONNTRACK)
>> +		q->flow_mode &= ~CAKE_FLOW_NAT_FLAG;
>> +		q->flow_mode |= CAKE_FLOW_NAT_FLAG *
>> +			!!nla_get_u32(tb[TCA_CAKE_NAT]);
>> +#else
>> +		NL_SET_ERR_MSG_ATTR(extack, "No conntrack support in kernel",
>> +				    tb[TCA_CAKE_NAT]);
>> +		return -EOPNOTSUPP;
>> +#endif
>> +	}
>> +
>>  	if (tb[TCA_CAKE_BASE_RATE64])
>>  		q->rate_bps = nla_get_u64(tb[TCA_CAKE_BASE_RATE64]);
>>  
>> @@ -2066,6 +2141,10 @@ static int cake_dump(struct Qdisc *sch, struct
>sk_buff *skb)
>>  	if (nla_put_u32(skb, TCA_CAKE_ACK_FILTER, q->ack_filter))
>>  		goto nla_put_failure;
>>  
>> +	if (nla_put_u32(skb, TCA_CAKE_NAT,
>> +			!!(q->flow_mode & CAKE_FLOW_NAT_FLAG)))
>> +		goto nla_put_failure;
>> +
>>  	return nla_nest_end(skb, opts);
>>  
>>  nla_put_failure:
>> 
>> _______________________________________________
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