[PATCH net-next v4 0/2] TC datapath hash api

[PATCH net-next v4 0/2] TC datapath hash api

[Ariel Levkovich]

Hash based packet classification allows user to set up rules that
provide load balancing of traffic across multiple vports and
for ECMP path selection while keeping the number of rule at minimum.

Instead of matching on exact flow spec, which requires a rule per
flow, user can define rules based on a their hash value and distribute
the flows to different buckets. The number of rules
in this case will be constant and equal to the number of buckets.

The series introduces an extention to the cls flower classifier
and allows user to add rules that match on the hash value that
is stored in skb->hash while assuming the value was set prior to
the classification.

Setting the skb->hash can be done in various ways and is not defined
in this series - for example:
1. By the device driver upon processing an rx packet.
2. Using tc action bpf with a program which computes and sets the
skb->hash value.

$ tc filter add dev ens1f0_0 ingress \
prio 1 chain 2 proto ip \
flower hash 0x0/0xf  \
action mirred egress redirect dev ens1f0_1

$ tc filter add dev ens1f0_0 ingress \
prio 1 chain 2 proto ip \
flower hash 0x1/0xf  \
action mirred egress redirect dev ens1f0_2

v3 -> v4:
 *Drop hash setting code leaving only the classidication parts.
  Setting the hash will be possible via existing tc action bpf.

v2 -> v3:
 *Split hash algorithm option into 2 different actions.
  Asym_l4 available via act_skbedit and bpf via new act_hash.

Ariel Levkovich (2):
  net/flow_dissector: add packet hash dissection
  net/sched: cls_flower: Add hash info to flow classification

 include/linux/skbuff.h       |  4 ++++
 include/net/flow_dissector.h |  9 +++++++++
 include/uapi/linux/pkt_cls.h |  3 +++
 net/core/flow_dissector.c    | 17 +++++++++++++++++
 net/sched/cls_flower.c       | 16 ++++++++++++++++
 5 files changed, 49 insertions(+)

-- 
2.25.2

[PATCH net-next v4 1/2] net/flow_dissector: add packet hash dissection

[Ariel Levkovich]

Retreive a hash value from the SKB and store it
in the dissector key for future matching.

Signed-off-by: Ariel Levkovich <lariel@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
---
 include/linux/skbuff.h       |  4 ++++
 include/net/flow_dissector.h |  9 +++++++++
 net/core/flow_dissector.c    | 17 +++++++++++++++++
 3 files changed, 30 insertions(+)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 0c0377fc00c2..beb7fe2c7809 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1342,6 +1342,10 @@ skb_flow_dissect_tunnel_info(const struct sk_buff *skb,
 			     struct flow_dissector *flow_dissector,
 			     void *target_container);
 
+void skb_flow_dissect_hash(const struct sk_buff *skb,
+			   struct flow_dissector *flow_dissector,
+			   void *target_container);
+
 static inline __u32 skb_get_hash(struct sk_buff *skb)
 {
 	if (!skb->l4_hash && !skb->sw_hash)
diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
index a7eba43fe4e4..5cc0540ce3f7 100644
--- a/include/net/flow_dissector.h
+++ b/include/net/flow_dissector.h
@@ -243,6 +243,14 @@ struct flow_dissector_key_ct {
 	u32	ct_labels[4];
 };
 
+/**
+ * struct flow_dissector_key_hash:
+ * @hash: hash value
+ */
+struct flow_dissector_key_hash {
+	u32 hash;
+};
+
 enum flow_dissector_key_id {
 	FLOW_DISSECTOR_KEY_CONTROL, /* struct flow_dissector_key_control */
 	FLOW_DISSECTOR_KEY_BASIC, /* struct flow_dissector_key_basic */
@@ -271,6 +279,7 @@ enum flow_dissector_key_id {
 	FLOW_DISSECTOR_KEY_ENC_OPTS, /* struct flow_dissector_key_enc_opts */
 	FLOW_DISSECTOR_KEY_META, /* struct flow_dissector_key_meta */
 	FLOW_DISSECTOR_KEY_CT, /* struct flow_dissector_key_ct */
+	FLOW_DISSECTOR_KEY_HASH, /* struct flow_dissector_key_hash */
 
 	FLOW_DISSECTOR_KEY_MAX,
 };
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index d02df0b6d0d9..c114f0e3ef4f 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -392,6 +392,23 @@ skb_flow_dissect_tunnel_info(const struct sk_buff *skb,
 }
 EXPORT_SYMBOL(skb_flow_dissect_tunnel_info);
 
+void skb_flow_dissect_hash(const struct sk_buff *skb,
+			   struct flow_dissector *flow_dissector,
+			   void *target_container)
+{
+	struct flow_dissector_key_hash *key;
+
+	if (!dissector_uses_key(flow_dissector, FLOW_DISSECTOR_KEY_HASH))
+		return;
+
+	key = skb_flow_dissector_target(flow_dissector,
+					FLOW_DISSECTOR_KEY_HASH,
+					target_container);
+
+	key->hash = skb_get_hash_raw(skb);
+}
+EXPORT_SYMBOL(skb_flow_dissect_hash);
+
 static enum flow_dissect_ret
 __skb_flow_dissect_mpls(const struct sk_buff *skb,
 			struct flow_dissector *flow_dissector,
-- 
2.25.2

[PATCH net-next v4 2/2] net/sched: cls_flower: Add hash info to flow classification

[Ariel Levkovich]

Adding new cls flower keys for hash value and hash
mask and dissect the hash info from the skb into
the flow key towards flow classication.

Signed-off-by: Ariel Levkovich <lariel@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
---
 include/uapi/linux/pkt_cls.h |  3 +++
 net/sched/cls_flower.c       | 16 ++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h
index 2fd93389d091..ef145320ee99 100644
--- a/include/uapi/linux/pkt_cls.h
+++ b/include/uapi/linux/pkt_cls.h
@@ -579,6 +579,9 @@ enum {
 
 	TCA_FLOWER_KEY_MPLS_OPTS,
 
+	TCA_FLOWER_KEY_HASH,		/* u32 */
+	TCA_FLOWER_KEY_HASH_MASK,	/* u32 */
+
 	__TCA_FLOWER_MAX,
 };
 
diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
index b2da37286082..ff739e0d86fc 100644
--- a/net/sched/cls_flower.c
+++ b/net/sched/cls_flower.c
@@ -64,6 +64,7 @@ struct fl_flow_key {
 		};
 	} tp_range;
 	struct flow_dissector_key_ct ct;
+	struct flow_dissector_key_hash hash;
 } __aligned(BITS_PER_LONG / 8); /* Ensure that we can do comparisons as longs. */
 
 struct fl_flow_mask_range {
@@ -318,6 +319,7 @@ static int fl_classify(struct sk_buff *skb, const struct tcf_proto *tp,
 		skb_flow_dissect_ct(skb, &mask->dissector, &skb_key,
 				    fl_ct_info_to_flower_map,
 				    ARRAY_SIZE(fl_ct_info_to_flower_map));
+		skb_flow_dissect_hash(skb, &mask->dissector, &skb_key);
 		skb_flow_dissect(skb, &mask->dissector, &skb_key, 0);
 
 		f = fl_mask_lookup(mask, &skb_key);
@@ -694,6 +696,9 @@ static const struct nla_policy fl_policy[TCA_FLOWER_MAX + 1] = {
 	[TCA_FLOWER_KEY_CT_LABELS_MASK]	= { .type = NLA_BINARY,
 					    .len = 128 / BITS_PER_BYTE },
 	[TCA_FLOWER_FLAGS]		= { .type = NLA_U32 },
+	[TCA_FLOWER_KEY_HASH]		= { .type = NLA_U32 },
+	[TCA_FLOWER_KEY_HASH_MASK]	= { .type = NLA_U32 },
+
 };
 
 static const struct nla_policy
@@ -1625,6 +1630,10 @@ static int fl_set_key(struct net *net, struct nlattr **tb,
 
 	fl_set_key_ip(tb, true, &key->enc_ip, &mask->enc_ip);
 
+	fl_set_key_val(tb, &key->hash.hash, TCA_FLOWER_KEY_HASH,
+		       &mask->hash.hash, TCA_FLOWER_KEY_HASH_MASK,
+		       sizeof(key->hash.hash));
+
 	if (tb[TCA_FLOWER_KEY_ENC_OPTS]) {
 		ret = fl_set_enc_opt(tb, key, mask, extack);
 		if (ret)
@@ -1739,6 +1748,8 @@ static void fl_init_dissector(struct flow_dissector *dissector,
 			     FLOW_DISSECTOR_KEY_ENC_OPTS, enc_opts);
 	FL_KEY_SET_IF_MASKED(mask, keys, cnt,
 			     FLOW_DISSECTOR_KEY_CT, ct);
+	FL_KEY_SET_IF_MASKED(mask, keys, cnt,
+			     FLOW_DISSECTOR_KEY_HASH, hash);
 
 	skb_flow_dissector_init(dissector, keys, cnt);
 }
@@ -2959,6 +2970,11 @@ static int fl_dump_key(struct sk_buff *skb, struct net *net,
 	if (fl_dump_key_flags(skb, key->control.flags, mask->control.flags))
 		goto nla_put_failure;
 
+	if (fl_dump_key_val(skb, &key->hash.hash, TCA_FLOWER_KEY_HASH,
+			     &mask->hash.hash, TCA_FLOWER_KEY_HASH_MASK,
+			     sizeof(key->hash.hash)))
+		goto nla_put_failure;
+
 	return 0;
 
 nla_put_failure:
-- 
2.25.2

Re: [PATCH net-next v4 0/2] TC datapath hash api

[David Miller]

From: Ariel Levkovich <lariel@mellanox.com>
Date: Thu, 23 Jul 2020 01:02:59 +0300

> Hash based packet classification allows user to set up rules that
> provide load balancing of traffic across multiple vports and
> for ECMP path selection while keeping the number of rule at minimum.
> 
> Instead of matching on exact flow spec, which requires a rule per
> flow, user can define rules based on a their hash value and distribute
> the flows to different buckets. The number of rules
> in this case will be constant and equal to the number of buckets.
> 
> The series introduces an extention to the cls flower classifier
> and allows user to add rules that match on the hash value that
> is stored in skb->hash while assuming the value was set prior to
> the classification.
> 
> Setting the skb->hash can be done in various ways and is not defined
> in this series - for example:
> 1. By the device driver upon processing an rx packet.
> 2. Using tc action bpf with a program which computes and sets the
> skb->hash value.
> 
> $ tc filter add dev ens1f0_0 ingress \
> prio 1 chain 2 proto ip \
> flower hash 0x0/0xf  \
> action mirred egress redirect dev ens1f0_1
> 
> $ tc filter add dev ens1f0_0 ingress \
> prio 1 chain 2 proto ip \
> flower hash 0x1/0xf  \
> action mirred egress redirect dev ens1f0_2
> 
> v3 -> v4:
>  *Drop hash setting code leaving only the classidication parts.
>   Setting the hash will be possible via existing tc action bpf.
> 
> v2 -> v3:
>  *Split hash algorithm option into 2 different actions.
>   Asym_l4 available via act_skbedit and bpf via new act_hash.

Series applied, thank you.