[ovs-dev] [bond megaflow v2 4/5] dpif-netdev: user space datapath recirculation
Andy Zhou
azhou at nicira.com
Tue Mar 11 23:56:20 UTC 2014
Add basic recirculation infrastructure and user space
data path support for it. The following bond mega flow patch will
make use of this infrastructure.
Signed-off-by: Andy Zhou <azhou at nicira.com>
---
v1->v2: Rewritten based on having post recirculation rules stored
in table 254.
---
include/linux/openvswitch.h | 35 ++++++++++++++++-
lib/dpif-netdev.c | 35 ++++++++++++++++-
lib/dpif.c | 3 +-
lib/odp-execute.c | 9 +++++
lib/odp-execute.h | 2 +-
lib/odp-util.c | 91 ++++++++++++++++++++++++++++++++++++++++++-
lib/packets.c | 16 +++++---
lib/packets.h | 16 +++++---
ofproto/ofproto-dpif.c | 2 +-
ofproto/ofproto-dpif.h | 63 ++++++++++++++++++++++++++++--
10 files changed, 251 insertions(+), 21 deletions(-)
diff --git a/include/linux/openvswitch.h b/include/linux/openvswitch.h
index d1ff5ec..af951f5 100644
--- a/include/linux/openvswitch.h
+++ b/include/linux/openvswitch.h
@@ -307,7 +307,8 @@ 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_RECIRC_ID, /* u32 recirc id */
#ifdef __KERNEL__
OVS_KEY_ATTR_IPV4_TUNNEL, /* struct ovs_key_ipv4_tunnel */
#endif
@@ -530,6 +531,36 @@ struct ovs_action_push_vlan {
__be16 vlan_tci; /* 802.1Q TCI (VLAN ID and priority). */
};
+/* Recirculation ID needs to be unique per back-end.
+ * It can be any value except zero. Use the following
+ * defines to restrict the range further.
+ */
+#define RECIRC_ID_BASE 300
+#define RECIRC_ID_SIZE 65535
+
+/* Data path hash algorithm for computing Datapath hash.
+ *
+ * The Algorithm type only specifies the fields in a flow
+ * will be used as part of the hash. Each datapath is free
+ * to use its own hash algorithm. The hash value will be
+ * opaque to the user space daemon.
+ */
+enum ovs_recirc_hash_alg {
+ OVS_RECIRC_HASH_ALG_NONE,
+ OVS_RECIRC_HASH_ALG_L4,
+};
+/*
+ * struct ovs_action_recirc - %OVS_ACTION_ATTR_RECIRC action argument.
+ * @recirc_id: The Recirculation label, Zero is invalid.
+ * @hash_alg: Algorithm used to compute hash prior to recirculation.
+ * @hash_bias: bias used for computing hash. used to compute hash prior to recirculation.
+ */
+struct ovs_action_recirc {
+ uint8_t hash_alg; /* One of ovs_dp_hash_alg */
+ __be32 hash_bias;
+ __be32 recirc_id; /* Recirculation label. */
+};
+
/**
* enum ovs_action_attr - Action types.
*
@@ -553,6 +584,7 @@ struct ovs_action_push_vlan {
* indicate the new packet contents. This could potentially still be
* %ETH_P_MPLS if the resulting MPLS label stack is not empty. If there
* is no MPLS label stack, as determined by ethertype, no action is taken.
+ * @OVS_ACTION_RECIRC: Recirculate within the data path.
*
* Only a single header can be set with a single %OVS_ACTION_ATTR_SET. Not all
* fields within a header are modifiable, e.g. the IPv4 protocol and fragment
@@ -569,6 +601,7 @@ enum ovs_action_attr {
OVS_ACTION_ATTR_SAMPLE, /* Nested OVS_SAMPLE_ATTR_*. */
OVS_ACTION_ATTR_PUSH_MPLS, /* struct ovs_action_push_mpls. */
OVS_ACTION_ATTR_POP_MPLS, /* __be16 ethertype. */
+ OVS_ACTION_ATTR_RECIRC, /* struct ovs_action_recirc. */
__OVS_ACTION_ATTR_MAX
};
diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index 5897f8b..58bcfc1 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -1157,6 +1157,19 @@ dpif_netdev_flow_get(const struct dpif *dpif,
return error;
}
+/* To support recirculation, user space datapath requires all rules
+ * have exact match to the metadata field, which will store the
+ * recirculation ID. */
+static void
+dp_netdev_match_init(struct match *match, const struct flow *flow,
+ const struct flow_wildcards *wc)
+{
+ struct flow_wildcards netdev_wc = *wc;
+
+ netdev_wc.masks.metadata = UINT64_MAX;
+ match_init(match, flow, &netdev_wc);
+}
+
static int
dp_netdev_flow_add(struct dp_netdev *dp, const struct flow *flow,
const struct flow_wildcards *wc,
@@ -1176,7 +1189,7 @@ dp_netdev_flow_add(struct dp_netdev *dp, const struct flow *flow,
netdev_flow->actions = dp_netdev_actions_create(actions, actions_len);
- match_init(&match, flow, wc);
+ dp_netdev_match_init(&match, flow, wc);
cls_rule_init(CONST_CAST(struct cls_rule *, &netdev_flow->cr),
&match, NETDEV_RULE_PRIORITY);
fat_rwlock_wrlock(&dp->cls.rwlock);
@@ -1808,7 +1821,7 @@ struct dp_netdev_execute_aux {
static void
dp_execute_cb(void *aux_, struct ofpbuf *packet,
- const struct pkt_metadata *md OVS_UNUSED,
+ struct pkt_metadata *md,
const struct nlattr *a, bool may_steal)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
@@ -1840,6 +1853,24 @@ dp_execute_cb(void *aux_, struct ofpbuf *packet,
}
break;
}
+
+ case OVS_ACTION_ATTR_RECIRC: {
+ const struct ovs_action_recirc *act;
+ act = nl_attr_get(a);
+ md->recirc_id = ntohl(act->recirc_id);
+ md->dp_hash = 0;
+
+ if (act->hash_alg == OVS_RECIRC_HASH_ALG_L4) {
+ struct flow flow;
+
+ flow_extract(packet, md, &flow);
+ md->dp_hash = flow_hash_symmetric_l4(&flow, ntohl(act->hash_bias));
+ }
+
+ dp_netdev_port_input(aux->dp, packet, md);
+ break;
+ }
+
case OVS_ACTION_ATTR_PUSH_VLAN:
case OVS_ACTION_ATTR_POP_VLAN:
case OVS_ACTION_ATTR_PUSH_MPLS:
diff --git a/lib/dpif.c b/lib/dpif.c
index 8cb2145..a56c612 100644
--- a/lib/dpif.c
+++ b/lib/dpif.c
@@ -1099,7 +1099,7 @@ struct dpif_execute_helper_aux {
* meaningful. */
static void
dpif_execute_helper_cb(void *aux_, struct ofpbuf *packet,
- const struct pkt_metadata *md,
+ struct pkt_metadata *md,
const struct nlattr *action, bool may_steal OVS_UNUSED)
{
struct dpif_execute_helper_aux *aux = aux_;
@@ -1124,6 +1124,7 @@ dpif_execute_helper_cb(void *aux_, struct ofpbuf *packet,
case OVS_ACTION_ATTR_SET:
case OVS_ACTION_ATTR_SAMPLE:
case OVS_ACTION_ATTR_UNSPEC:
+ case OVS_ACTION_ATTR_RECIRC:
case __OVS_ACTION_ATTR_MAX:
OVS_NOT_REACHED();
}
diff --git a/lib/odp-execute.c b/lib/odp-execute.c
index 096c113..cde5bf4 100644
--- a/lib/odp-execute.c
+++ b/lib/odp-execute.c
@@ -125,6 +125,14 @@ odp_execute_set_action(struct ofpbuf *packet, const struct nlattr *a,
set_arp(packet, nl_attr_get_unspec(a, sizeof(struct ovs_key_arp)));
break;
+ case OVS_KEY_ATTR_DP_HASH:
+ md->dp_hash = nl_attr_get_u32(a);
+ break;
+
+ case OVS_KEY_ATTR_RECIRC_ID:
+ md->recirc_id = nl_attr_get_u32(a);
+ break;
+
case OVS_KEY_ATTR_UNSPEC:
case OVS_KEY_ATTR_ENCAP:
case OVS_KEY_ATTR_ETHERTYPE:
@@ -195,6 +203,7 @@ odp_execute_actions__(void *dp, struct ofpbuf *packet, struct pkt_metadata *md,
/* These only make sense in the context of a datapath. */
case OVS_ACTION_ATTR_OUTPUT:
case OVS_ACTION_ATTR_USERSPACE:
+ case OVS_ACTION_ATTR_RECIRC:
if (dp_execute_action) {
/* Allow 'dp_execute_action' to steal the packet data if we do
* not need it any more. */
diff --git a/lib/odp-execute.h b/lib/odp-execute.h
index 670e8ea..18f50c3 100644
--- a/lib/odp-execute.h
+++ b/lib/odp-execute.h
@@ -28,7 +28,7 @@ struct ofpbuf;
struct pkt_metadata;
typedef void (*odp_execute_cb)(void *dp, struct ofpbuf *packet,
- const struct pkt_metadata *,
+ struct pkt_metadata *,
const struct nlattr *action, bool may_steal);
/* Actions that need to be executed in the context of a datapath are handed
diff --git a/lib/odp-util.c b/lib/odp-util.c
index 463f008..6e46dff 100644
--- a/lib/odp-util.c
+++ b/lib/odp-util.c
@@ -79,6 +79,7 @@ odp_action_len(uint16_t type)
case OVS_ACTION_ATTR_POP_VLAN: return 0;
case OVS_ACTION_ATTR_PUSH_MPLS: return sizeof(struct ovs_action_push_mpls);
case OVS_ACTION_ATTR_POP_MPLS: return sizeof(ovs_be16);
+ case OVS_ACTION_ATTR_RECIRC: return sizeof(struct ovs_action_recirc);
case OVS_ACTION_ATTR_SET: return -2;
case OVS_ACTION_ATTR_SAMPLE: return -2;
@@ -118,6 +119,8 @@ ovs_key_attr_to_string(enum ovs_key_attr attr, char *namebuf, size_t bufsize)
case OVS_KEY_ATTR_ARP: return "arp";
case OVS_KEY_ATTR_ND: return "nd";
case OVS_KEY_ATTR_MPLS: return "mpls";
+ case OVS_KEY_ATTR_DP_HASH: return "dp_hash";
+ case OVS_KEY_ATTR_RECIRC_ID: return "recirc_id";
case __OVS_KEY_ATTR_MAX:
default:
@@ -385,6 +388,27 @@ format_mpls(struct ds *ds, const struct ovs_key_mpls *mpls_key,
}
static void
+format_odp_recirc_action(struct ds *ds,
+ const struct ovs_action_recirc *act)
+{
+ const char *hash_str = NULL;
+
+ switch (act->hash_alg) {
+ case OVS_RECIRC_HASH_ALG_L4:
+ hash_str = "hash_l4";
+ break;
+ case OVS_RECIRC_HASH_ALG_NONE:
+ default:
+ break;
+ }
+
+ hash_str
+ ? ds_put_format(ds, "recirc(%s(%"PRIu32"), %"PRIu32")",
+ hash_str, ntohl(act->hash_bias), ntohl(act->recirc_id))
+ : ds_put_format(ds, "recirc(%"PRIu32")", ntohl(act->recirc_id));
+}
+
+static void
format_odp_action(struct ds *ds, const struct nlattr *a)
{
int expected_len;
@@ -406,6 +430,9 @@ format_odp_action(struct ds *ds, const struct nlattr *a)
case OVS_ACTION_ATTR_USERSPACE:
format_odp_userspace_action(ds, a);
break;
+ case OVS_ACTION_ATTR_RECIRC:
+ format_odp_recirc_action(ds, nl_attr_get(a));
+ break;
case OVS_ACTION_ATTR_SET:
ds_put_cstr(ds, "set(");
format_odp_key_attr(nl_attr_get(a), NULL, NULL, ds, true);
@@ -731,6 +758,8 @@ odp_flow_key_attr_len(uint16_t type)
case OVS_KEY_ATTR_ENCAP: return -2;
case OVS_KEY_ATTR_PRIORITY: return 4;
case OVS_KEY_ATTR_SKB_MARK: return 4;
+ case OVS_KEY_ATTR_DP_HASH: return 4;
+ case OVS_KEY_ATTR_RECIRC_ID: return 4;
case OVS_KEY_ATTR_TUNNEL: return -2;
case OVS_KEY_ATTR_IN_PORT: return 4;
case OVS_KEY_ATTR_ETHERNET: return sizeof(struct ovs_key_ethernet);
@@ -1026,6 +1055,8 @@ format_odp_key_attr(const struct nlattr *a, const struct nlattr *ma,
case OVS_KEY_ATTR_PRIORITY:
case OVS_KEY_ATTR_SKB_MARK:
+ case OVS_KEY_ATTR_DP_HASH:
+ case OVS_KEY_ATTR_RECIRC_ID:
ds_put_format(ds, "%#"PRIx32, nl_attr_get_u32(a));
if (!is_exact) {
ds_put_format(ds, "/%#"PRIx32, nl_attr_get_u32(ma));
@@ -1387,7 +1418,6 @@ format_odp_key_attr(const struct nlattr *a, const struct nlattr *ma,
}
break;
}
-
case OVS_KEY_ATTR_UNSPEC:
case __OVS_KEY_ATTR_MAX:
default:
@@ -1620,6 +1650,36 @@ parse_odp_key_mask_attr(const char *s, const struct simap *port_names,
}
{
+ uint32_t recirc_id;
+ int n = -1;
+
+ if (ovs_scan(s, "recirc_id(%"SCNi32")%n", &recirc_id, &n)) {
+ nl_msg_put_u32(key, OVS_KEY_ATTR_RECIRC_ID, recirc_id);
+ nl_msg_put_u32(mask, OVS_KEY_ATTR_RECIRC_ID, UINT32_MAX);
+ return n;
+ }
+ }
+
+ {
+ uint32_t dp_hash;
+ uint32_t dp_hash_mask;
+ int n = -1;
+
+ if (mask && ovs_scan(s, "dp_hash(%"SCNi32"/%"SCNi32")%n", &dp_hash,
+ &dp_hash_mask, &n)) {
+ nl_msg_put_u32(key, OVS_KEY_ATTR_DP_HASH, dp_hash);
+ nl_msg_put_u32(mask, OVS_KEY_ATTR_DP_HASH, dp_hash_mask);
+ return n;
+ } else if (ovs_scan(s, "dp_hash(%"SCNi32")%n", &dp_hash, &n)) {
+ nl_msg_put_u32(key, OVS_KEY_ATTR_DP_HASH, dp_hash);
+ if (mask) {
+ nl_msg_put_u32(mask, OVS_KEY_ATTR_DP_HASH, UINT32_MAX);
+ }
+ return n;
+ }
+ }
+
+ {
uint64_t tun_id, tun_id_mask;
struct flow_tnl tun_key, tun_key_mask;
int n = -1;
@@ -2439,6 +2499,14 @@ odp_flow_key_from_flow__(struct ofpbuf *buf, const struct flow *data,
nl_msg_put_u32(buf, OVS_KEY_ATTR_SKB_MARK, data->pkt_mark);
+ if (!is_mask && data->recirc_id) {
+ nl_msg_put_u32(buf, OVS_KEY_ATTR_RECIRC_ID, data->recirc_id);
+ }
+
+ if (data->dp_hash != 0) {
+ nl_msg_put_u32(buf, OVS_KEY_ATTR_DP_HASH, data->dp_hash);
+ }
+
/* Add an ingress port attribute if this is a mask or 'odp_in_port'
* is not the magical value "ODPP_NONE". */
if (is_mask || odp_in_port != ODPP_NONE) {
@@ -2674,6 +2742,14 @@ odp_key_to_pkt_metadata(const struct nlattr *key, size_t key_len,
continue;
}
+ if (type == OVS_KEY_ATTR_RECIRC_ID) {
+ md->recirc_id = nl_attr_get_u32(nla);
+ wanted_attrs &= ~(1u << OVS_KEY_ATTR_RECIRC_ID);
+ }
+ if (type == OVS_KEY_ATTR_DP_HASH) {
+ md->dp_hash = nl_attr_get_u32(nla);
+ wanted_attrs &= ~(1u << OVS_KEY_ATTR_DP_HASH);
+ }
if (type == OVS_KEY_ATTR_PRIORITY) {
md->skb_priority = nl_attr_get_u32(nla);
wanted_attrs &= ~(1u << OVS_KEY_ATTR_PRIORITY);
@@ -3231,6 +3307,19 @@ odp_flow_key_to_flow__(const struct nlattr *key, size_t key_len,
expected_attrs = 0;
/* Metadata. */
+ if (present_attrs & (UINT64_C(1) << OVS_KEY_ATTR_RECIRC_ID)) {
+ flow->recirc_id = nl_attr_get_u32(attrs[OVS_KEY_ATTR_RECIRC_ID]);
+ expected_attrs |= UINT64_C(1) << OVS_KEY_ATTR_RECIRC_ID;
+ }
+ /* Always exact match RECIRC_ID. */
+ if (is_mask) {
+ flow->recirc_id = UINT32_MAX;
+ }
+
+ if (present_attrs & (UINT64_C(1) << OVS_KEY_ATTR_DP_HASH)) {
+ flow->dp_hash = nl_attr_get_u32(attrs[OVS_KEY_ATTR_DP_HASH]);
+ expected_attrs |= UINT64_C(1) << OVS_KEY_ATTR_DP_HASH;
+ }
if (present_attrs & (UINT64_C(1) << OVS_KEY_ATTR_PRIORITY)) {
flow->skb_priority = nl_attr_get_u32(attrs[OVS_KEY_ATTR_PRIORITY]);
expected_attrs |= UINT64_C(1) << OVS_KEY_ATTR_PRIORITY;
diff --git a/lib/packets.c b/lib/packets.c
index 3f7d6eb..9f8feea 100644
--- a/lib/packets.c
+++ b/lib/packets.c
@@ -993,15 +993,18 @@ packet_format_tcp_flags(struct ds *s, uint16_t tcp_flags)
}
}
-void pkt_metadata_init(struct pkt_metadata *md, const struct flow_tnl *tnl,
- const uint32_t skb_priority,
- const uint32_t pkt_mark,
- const union flow_in_port *in_port)
+void pkt_metadata_init(struct pkt_metadata *md,
+ const uint32_t recirc_id, const uint32_t dp_hash,
+ const struct flow_tnl *tnl, const uint32_t skb_priority,
+ const uint32_t pkt_mark,
+ const union flow_in_port *in_port)
{
tnl ? memcpy(&md->tunnel, tnl, sizeof(md->tunnel))
: memset(&md->tunnel, 0, sizeof(md->tunnel));
+ md->recirc_id = recirc_id;
+ md->dp_hash = dp_hash;
md->skb_priority = skb_priority;
md->pkt_mark = pkt_mark;
md->in_port.odp_port = in_port ? in_port->odp_port : ODPP_NONE;
@@ -1009,6 +1012,7 @@ void pkt_metadata_init(struct pkt_metadata *md, const struct flow_tnl *tnl,
void pkt_metadata_from_flow(struct pkt_metadata *md, const struct flow *flow)
{
- pkt_metadata_init(md, &flow->tunnel, flow->skb_priority,
- flow->pkt_mark, &flow->in_port);
+ pkt_metadata_init(md, flow->recirc_id, flow->dp_hash,
+ &flow->tunnel, flow->skb_priority,
+ flow->pkt_mark, &flow->in_port);
}
diff --git a/lib/packets.h b/lib/packets.h
index e6b3303..f538218 100644
--- a/lib/packets.h
+++ b/lib/packets.h
@@ -33,6 +33,11 @@ struct ds;
/* Datapath packet metadata */
struct pkt_metadata {
+ uint32_t recirc_id; /* Recirculation id carried with the
+ recirculating packets. 0 for packets
+ received from the wire. */
+ uint32_t dp_hash; /* hash value computed by the recirculation
+ action. */
struct flow_tnl tunnel; /* Encapsulating tunnel parameters. */
uint32_t skb_priority; /* Packet priority for QoS. */
uint32_t pkt_mark; /* Packet mark. */
@@ -40,12 +45,13 @@ struct pkt_metadata {
};
#define PKT_METADATA_INITIALIZER(PORT) \
- (struct pkt_metadata){ { 0, 0, 0, 0, 0, 0}, 0, 0, {(PORT)} }
+ (struct pkt_metadata){ 0, 0, { 0, 0, 0, 0, 0, 0}, 0, 0, {(PORT)} }
-void pkt_metadata_init(struct pkt_metadata *md, const struct flow_tnl *tnl,
- const uint32_t skb_priority,
- const uint32_t pkt_mark,
- const union flow_in_port *in_port);
+void pkt_metadata_init(struct pkt_metadata *md,
+ const uint32_t recirc_id, const uint32_t dp_hash,
+ const struct flow_tnl *tnl, const uint32_t skb_priority,
+ const uint32_t pkt_mark,
+ const union flow_in_port *in_port);
void pkt_metadata_from_flow(struct pkt_metadata *md, const struct flow *flow);
bool dpid_from_string(const char *s, uint64_t *dpidp);
diff --git a/ofproto/ofproto-dpif.c b/ofproto/ofproto-dpif.c
index 252e6b4..4018129 100644
--- a/ofproto/ofproto-dpif.c
+++ b/ofproto/ofproto-dpif.c
@@ -3818,7 +3818,7 @@ parse_flow_and_packet(int argc, const char *argv[],
/* Use the metadata from the flow and the packet argument
* to reconstruct the flow. */
- pkt_metadata_init(&md, NULL, flow->skb_priority,
+ pkt_metadata_init(&md, 0, 0, NULL, flow->skb_priority,
flow->pkt_mark, &in_port);
flow_extract(packet, &md, flow);
diff --git a/ofproto/ofproto-dpif.h b/ofproto/ofproto-dpif.h
index d57bf21..f020c7d 100644
--- a/ofproto/ofproto-dpif.h
+++ b/ofproto/ofproto-dpif.h
@@ -120,9 +120,66 @@ void ofproto_dpif_send_packet_in(struct ofproto_dpif *,
int ofproto_dpif_send_packet(const struct ofport_dpif *, struct ofpbuf *);
void ofproto_dpif_flow_mod(struct ofproto_dpif *, struct ofputil_flow_mod *);
-uint32_t ofproto_dpif_alloc_recirc_id(struct ofproto *ofproto_);
-void ofproto_dpif_free_recirc_id(struct ofproto *ofproto_, uint32_t recirc_id);
-
struct ofport_dpif *odp_port_to_ofport(const struct dpif_backer *, odp_port_t);
+/*
+Recirculation
+=============
+
+Recirculation is a technique to allow a frame to re-enter the packet processing
+path for one or multiple times to achieve more flexible packet processing in the
+data path. MPLS handling and selecting bond slave port of a bond ports.
+
+Data path and user space interface
+-----------------------------------
+Two new fields, recirc_id and dp_hash, are added to the current flow data structure.
+They are both both of type uint32_t. In addition, a new action, RECIRC, are added.
+
+The value recirc_id is used to distinguish a packet from multiple iterations of
+recirculation. A packet initially received is considered of having recirc_id of 0.
+Recirc_id is managed by the user space, opaque to the data path.
+
+On the other hand, dp_hash can only be computed by the data path, opaque to
+the user space. In fact, user space may not able to recompute the hash value.
+The dp_hash value should be wildcarded when for a newly received packet.
+RECIRC action specifies whether the hash is computed. If computed, how many
+fields to be included in the hash computation. The computed hash value is
+stored into the dp_hash field prior to recirculation.
+
+The RECIRC action computes and set the dp_hash field, set the recirc_id field
+and then reprocess the packet as if it was received on the same input port.
+RECIRC action works like a function call; actions listed behind the RECIRC
+action will be executed after its execution. RECIRC action can be nested,
+data path implementation limits the number of recirculation executed
+to prevent unreasonable nesting depth or infinite loop.
+
+Both flow fields and the RECIRC action are exposed as open flow fields via
+Nicira extensions.
+
+Post recirculation flow
+------------------------
+At the open flow level, post recirculation rules are always hidden from the
+controller. They are installed in table 254 which is set up as a hidden table
+during boot time. Those rules are managed by the local user space program only.
+
+To speed up the classifier look up process, recirc_id is always reflected into
+the metadata field, since recirc_id is required to be exactly matched.
+
+Classifier look up always starts with table 254. A post recirculation flow
+lookup should find its hidden rule within this table. On the other hand, A
+newly received packet should miss all post recirculation rules because its
+recirc_id is zero, then hit a pre-installed lower priority rule to redirect
+classifier to look up starting from table 0:
+
+ * , actions=resubmit(,0)
+
+Post recirculation data path flows are managed like other data path flows.
+They are created on demand. Miss handling, stats collection and revalidation
+work the same way as regular flows.
+*/
+
+uint32_t ofproto_dpif_alloc_recirc_id(struct ofproto *ofproto);
+void ofproto_dpif_free_recirc_id(struct ofproto *ofproto, uint32_t recirc_id);
+
+
#endif /* ofproto-dpif.h */
--
1.7.9.5
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