[ovs-dev] [PATCH 1/2] datapath: add hash action

[Andy Zhou]

Signed-off-by: Andy Zhou <azhou at nicira.com>

----
V4->V5:
       * Make sure OVS_CB(Skb)->input_port is always set.
       * always export recirc_id.

V3->v4:
       * Rehash the hash with hash_basis
       * always accept dp_hash mask
       * add mask to ovs_nla_put_flow() API

V2->V3:
       * rename dp_hash to ovs_flow_hash
       * Simplify netlink message error checking logic
       * other cleanups
---
 datapath/actions.c          | 19 +++++++++++++++++++
 datapath/flow.h             |  1 +
 datapath/flow_netlink.c     | 27 ++++++++++++++++++++++++++-
 include/linux/openvswitch.h |  3 ++-
 4 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/datapath/actions.c b/datapath/actions.c
index 82cfd2d..c4b4605 100644
--- a/datapath/actions.c
+++ b/datapath/actions.c
@@ -460,6 +460,21 @@ static int sample(struct datapath *dp, struct sk_buff *skb,
 				  nla_len(acts_list), true);
 }
 
+static void execute_hash(struct sk_buff *skb, const struct nlattr *attr)
+{
+	struct sw_flow_key *key = OVS_CB(skb)->pkt_key;
+	struct ovs_action_hash *hash_act = nla_data(attr);
+	u32 hash = 0;
+
+	/* OVS_HASH_ALG_L4 is the only possible hash algorithm.  */
+	hash = skb_get_rxhash(skb);
+	hash = jhash_1word(hash, hash_act->hash_basis);
+	if (!hash)
+		hash = 0x1;
+
+	key->ovs_flow_hash = hash;
+}
+
 static int execute_set_action(struct sk_buff *skb,
 				 const struct nlattr *nested_attr)
 {
@@ -536,6 +551,10 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
 			output_userspace(dp, skb, a);
 			break;
 
+		case OVS_ACTION_ATTR_HASH:
+			execute_hash(skb, a);
+			break;
+
 		case OVS_ACTION_ATTR_PUSH_VLAN:
 			err = push_vlan(skb, nla_data(a));
 			if (unlikely(err)) /* skb already freed. */
diff --git a/datapath/flow.h b/datapath/flow.h
index 1bb6ce0..a4cb57e 100644
--- a/datapath/flow.h
+++ b/datapath/flow.h
@@ -74,6 +74,7 @@ struct sw_flow_key {
 		u32	skb_mark;	/* SKB mark. */
 		u16	in_port;	/* Input switch port (or DP_MAX_PORTS). */
 	} __packed phy; /* Safe when right after 'tun_key'. */
+	u32 ovs_flow_hash;		/* Datapath computed hash value.  */
 	struct {
 		u8     src[ETH_ALEN];	/* Ethernet source address. */
 		u8     dst[ETH_ALEN];	/* Ethernet destination address. */
diff --git a/datapath/flow_netlink.c b/datapath/flow_netlink.c
index 5c32cd0..7db14de 100644
--- a/datapath/flow_netlink.c
+++ b/datapath/flow_netlink.c
@@ -252,6 +252,7 @@ static const int ovs_key_lens[OVS_KEY_ATTR_MAX + 1] = {
 	[OVS_KEY_ATTR_ICMPV6] = sizeof(struct ovs_key_icmpv6),
 	[OVS_KEY_ATTR_ARP] = sizeof(struct ovs_key_arp),
 	[OVS_KEY_ATTR_ND] = sizeof(struct ovs_key_nd),
+	[OVS_KEY_ATTR_DP_HASH] = sizeof(u32),
 	[OVS_KEY_ATTR_TUNNEL] = -1,
 };
 
@@ -455,6 +456,13 @@ static int ipv4_tun_to_nlattr(struct sk_buff *skb,
 static int metadata_from_nlattrs(struct sw_flow_match *match,  u64 *attrs,
 				 const struct nlattr **a, bool is_mask)
 {
+	if (*attrs & (1ULL << OVS_KEY_ATTR_DP_HASH)) {
+		u32 hash_val = nla_get_u32(a[OVS_KEY_ATTR_DP_HASH]);
+
+		SW_FLOW_KEY_PUT(match, ovs_flow_hash, hash_val, is_mask);
+		*attrs &= ~(1ULL << OVS_KEY_ATTR_DP_HASH);
+	}
+
 	if (*attrs & (1ULL << OVS_KEY_ATTR_PRIORITY)) {
 		SW_FLOW_KEY_PUT(match, phy.priority,
 			  nla_get_u32(a[OVS_KEY_ATTR_PRIORITY]), is_mask);
@@ -859,6 +867,7 @@ int ovs_nla_get_flow_metadata(struct sw_flow *flow,
 	flow->key.phy.in_port = DP_MAX_PORTS;
 	flow->key.phy.priority = 0;
 	flow->key.phy.skb_mark = 0;
+	flow->key.ovs_flow_hash = 0;
 	memset(tun_key, 0, sizeof(flow->key.tun_key));
 
 	err = parse_flow_nlattrs(attr, a, &attrs);
@@ -882,6 +891,9 @@ int ovs_nla_put_flow(const struct sw_flow_key *swkey,
 	struct nlattr *nla, *encap;
 	bool is_mask = (swkey != output);
 
+	if (nla_put_u32(skb, OVS_KEY_ATTR_DP_HASH, output->ovs_flow_hash))
+		goto nla_put_failure;
+
 	if (nla_put_u32(skb, OVS_KEY_ATTR_PRIORITY, output->phy.priority))
 		goto nla_put_failure;
 
@@ -1422,7 +1434,8 @@ int ovs_nla_copy_actions(const struct nlattr *attr,
 			[OVS_ACTION_ATTR_PUSH_VLAN] = sizeof(struct ovs_action_push_vlan),
 			[OVS_ACTION_ATTR_POP_VLAN] = 0,
 			[OVS_ACTION_ATTR_SET] = (u32)-1,
-			[OVS_ACTION_ATTR_SAMPLE] = (u32)-1
+			[OVS_ACTION_ATTR_SAMPLE] = (u32)-1,
+			[OVS_ACTION_ATTR_HASH] = sizeof(struct ovs_action_hash)
 		};
 		const struct ovs_action_push_vlan *vlan;
 		int type = nla_type(a);
@@ -1449,6 +1462,18 @@ int ovs_nla_copy_actions(const struct nlattr *attr,
 				return -EINVAL;
 			break;
 
+		case OVS_ACTION_ATTR_HASH: {
+			const struct ovs_action_hash *act_hash = nla_data(a);
+
+			switch (act_hash->hash_alg) {
+			case OVS_HASH_ALG_L4:
+				break;
+			default:
+				return  -EINVAL;
+			}
+
+			break;
+		}
 
 		case OVS_ACTION_ATTR_POP_VLAN:
 			break;
diff --git a/include/linux/openvswitch.h b/include/linux/openvswitch.h
index 1aa9158..dd2cceb 100644
--- a/include/linux/openvswitch.h
+++ b/include/linux/openvswitch.h
@@ -312,7 +312,8 @@ enum ovs_key_attr {
 	OVS_KEY_ATTR_TUNNEL,	/* Nested set of ovs_tunnel attributes */
 	OVS_KEY_ATTR_SCTP,      /* struct ovs_key_sctp */
 	OVS_KEY_ATTR_TCP_FLAGS,	/* be16 TCP flags. */
-	OVS_KEY_ATTR_DP_HASH,	/* u32 hash value */
+	OVS_KEY_ATTR_DP_HASH,	/* u32 hash value. Value 0 indicates the hash
+				   is not computed by the datpath. */
 	OVS_KEY_ATTR_RECIRC_ID, /* u32 recirc id */
 #ifdef __KERNEL__
 	/* Only used within kernel data path. */
-- 
1.9.1