[ovs-dev] [PATCH v3 1/3] userspace datapath: Add OVS_HASH_L4_SYMMETRIC dp_hash algorithm

Jan Scheurich jan.scheurich at ericsson.com
Fri Apr 27 12:20:32 UTC 2018


This commit implements a new dp_hash algorithm OVS_HASH_L4_SYMMETRIC in
the netdev datapath. It will be used as default hash algorithm for the
dp_hash-based select groups in a subsequent commit to maintain
compatibility with the symmetry property of the current default hash
selection method.

A new dpif_backer_support field 'max_hash_alg' is introduced to reflect
the highest hash algorithm a datapath supports in the dp_hash action.

Signed-off-by: Jan Scheurich <jan.scheurich at ericsson.com>
Signed-off-by: Nitin Katiyar <nitin.katiyar at ericsson.com>
Co-authored-by: Nitin Katiyar <nitin.katiyar at ericsson.com>
---
 datapath/linux/compat/include/linux/openvswitch.h |  4 ++
 lib/flow.c                                        | 43 +++++++++++++++++++++-
 lib/flow.h                                        |  1 +
 lib/odp-execute.c                                 | 23 ++++++++++--
 ofproto/ofproto-dpif-xlate.c                      |  7 +++-
 ofproto/ofproto-dpif.c                            | 45 +++++++++++++++++++++++
 ofproto/ofproto-dpif.h                            |  5 ++-
 7 files changed, 121 insertions(+), 7 deletions(-)

diff --git a/datapath/linux/compat/include/linux/openvswitch.h b/datapath/linux/compat/include/linux/openvswitch.h
index 84ebcaf..2bb3cb2 100644
--- a/datapath/linux/compat/include/linux/openvswitch.h
+++ b/datapath/linux/compat/include/linux/openvswitch.h
@@ -720,6 +720,10 @@ struct ovs_action_push_vlan {
  */
 enum ovs_hash_alg {
 	OVS_HASH_ALG_L4,
+#ifndef __KERNEL__
+	OVS_HASH_ALG_SYM_L4,
+#endif
+	__OVS_HASH_MAX
 };
 
 /*
diff --git a/lib/flow.c b/lib/flow.c
index 09b66b8..c65b288 100644
--- a/lib/flow.c
+++ b/lib/flow.c
@@ -2108,6 +2108,45 @@ flow_hash_symmetric_l4(const struct flow *flow, uint32_t basis)
     return jhash_bytes(&fields, sizeof fields, basis);
 }
 
+/* Symmetrically Hashes non-IP 'flow' based on its L2 headers. */
+uint32_t
+flow_hash_symmetric_l2(const struct flow *flow, uint32_t basis)
+{
+    union {
+        struct {
+            ovs_be16 eth_type;
+            ovs_be16 vlan_tci;
+            struct eth_addr eth_addr;
+            ovs_be16 pad;
+        };
+        uint32_t word[3];
+    } fields;
+
+    uint32_t hash = basis;
+    int i;
+
+    if (flow->packet_type != htonl(PT_ETH)) {
+        /* Cannot hash non-Ethernet flows */
+        return 0;
+    }
+
+    for (i = 0; i < ARRAY_SIZE(fields.eth_addr.be16); i++) {
+        fields.eth_addr.be16[i] =
+                flow->dl_src.be16[i] ^ flow->dl_dst.be16[i];
+    }
+    fields.vlan_tci = 0;
+    for (i = 0; i < FLOW_MAX_VLAN_HEADERS; i++) {
+        fields.vlan_tci ^= flow->vlans[i].tci & htons(VLAN_VID_MASK);
+    }
+    fields.eth_type = flow->dl_type;
+    fields.pad = 0;
+
+    hash = hash_add(hash, fields.word[0]);
+    hash = hash_add(hash, fields.word[1]);
+    hash = hash_add(hash, fields.word[2]);
+    return hash_finish(hash, basis);
+}
+
 /* Hashes 'flow' based on its L3 through L4 protocol information */
 uint32_t
 flow_hash_symmetric_l3l4(const struct flow *flow, uint32_t basis,
@@ -2128,8 +2167,8 @@ flow_hash_symmetric_l3l4(const struct flow *flow, uint32_t basis,
             hash = hash_add64(hash, a[i] ^ b[i]);
         }
     } else {
-        /* Cannot hash non-IP flows */
-        return 0;
+        /* Revert to hashing L2 headers */
+        return flow_hash_symmetric_l2(flow, basis);
     }
 
     hash = hash_add(hash, flow->nw_proto);
diff --git a/lib/flow.h b/lib/flow.h
index af82931..900e8f8 100644
--- a/lib/flow.h
+++ b/lib/flow.h
@@ -236,6 +236,7 @@ hash_odp_port(odp_port_t odp_port)
 
 uint32_t flow_hash_5tuple(const struct flow *flow, uint32_t basis);
 uint32_t flow_hash_symmetric_l4(const struct flow *flow, uint32_t basis);
+uint32_t flow_hash_symmetric_l2(const struct flow *flow, uint32_t basis);
 uint32_t flow_hash_symmetric_l3l4(const struct flow *flow, uint32_t basis,
                          bool inc_udp_ports );
 
diff --git a/lib/odp-execute.c b/lib/odp-execute.c
index 1969f02..c716c41 100644
--- a/lib/odp-execute.c
+++ b/lib/odp-execute.c
@@ -726,14 +726,16 @@ odp_execute_actions(void *dp, struct dp_packet_batch *batch, bool steal,
         }
 
         switch ((enum ovs_action_attr) type) {
+
         case OVS_ACTION_ATTR_HASH: {
             const struct ovs_action_hash *hash_act = nl_attr_get(a);
 
-            /* Calculate a hash value directly.  This might not match the
+            /* Calculate a hash value directly. This might not match the
              * value computed by the datapath, but it is much less expensive,
              * and the current use case (bonding) does not require a strict
              * match to work properly. */
-            if (hash_act->hash_alg == OVS_HASH_ALG_L4) {
+            switch (hash_act->hash_alg) {
+            case OVS_HASH_ALG_L4: {
                 struct flow flow;
                 uint32_t hash;
 
@@ -749,7 +751,22 @@ odp_execute_actions(void *dp, struct dp_packet_batch *batch, bool steal,
                     }
                     packet->md.dp_hash = hash;
                 }
-            } else {
+                break;
+            }
+            case OVS_HASH_ALG_SYM_L4: {
+                struct flow flow;
+                uint32_t hash;
+
+                DP_PACKET_BATCH_FOR_EACH (i, packet, batch) {
+                    flow_extract(packet, &flow);
+                    hash = flow_hash_symmetric_l3l4(&flow,
+                                                    hash_act->hash_basis,
+                                                    false);
+                    packet->md.dp_hash = hash;
+                }
+                break;
+            }
+            default:
                 /* Assert on unknown hash algorithm.  */
                 OVS_NOT_REACHED();
             }
diff --git a/ofproto/ofproto-dpif-xlate.c b/ofproto/ofproto-dpif-xlate.c
index 94e3ddb..05db090 100644
--- a/ofproto/ofproto-dpif-xlate.c
+++ b/ofproto/ofproto-dpif-xlate.c
@@ -3968,10 +3968,15 @@ compose_output_action__(struct xlate_ctx *ctx, ofp_port_t ofp_port,
             struct ovs_action_hash *act_hash;
 
             /* Hash action. */
+            enum ovs_hash_alg hash_alg = xr->hash_alg;
+            if (hash_alg > ctx->xbridge->support.max_hash_alg) {
+                /* Algorithm supported by all datapaths. */
+                hash_alg = OVS_HASH_ALG_L4;
+            }
             act_hash = nl_msg_put_unspec_uninit(ctx->odp_actions,
                                                 OVS_ACTION_ATTR_HASH,
                                                 sizeof *act_hash);
-            act_hash->hash_alg = xr->hash_alg;
+            act_hash->hash_alg = hash_alg;
             act_hash->hash_basis = xr->hash_basis;
 
             /* Recirc action. */
diff --git a/ofproto/ofproto-dpif.c b/ofproto/ofproto-dpif.c
index 1ed82d0..7162811 100644
--- a/ofproto/ofproto-dpif.c
+++ b/ofproto/ofproto-dpif.c
@@ -1291,6 +1291,50 @@ check_ct_clear(struct dpif_backer *backer)
     return supported;
 }
 
+/* Probe the highest dp_hash algorithm supported by the datapath. */
+static size_t
+check_max_dp_hash_alg(struct dpif_backer *backer)
+{
+    struct odputil_keybuf keybuf;
+    struct ofpbuf key;
+    struct flow flow;
+    struct ovs_action_hash *hash;
+    int max_alg = 0;
+
+    struct odp_flow_key_parms odp_parms = {
+        .flow = &flow,
+        .probe = true,
+    };
+
+    memset(&flow, 0, sizeof flow);
+    ofpbuf_use_stack(&key, &keybuf, sizeof keybuf);
+    odp_flow_key_from_flow(&odp_parms, &key);
+
+    /* All datapaths support algortithm 0 (OVS_HASH_ALG_L4). */
+    for (int alg = 1; alg < __OVS_HASH_MAX; alg++) {
+        struct ofpbuf actions;
+        bool ok;
+
+        ofpbuf_init(&actions, 300);
+        hash = nl_msg_put_unspec_uninit(&actions,
+                                        OVS_ACTION_ATTR_HASH, sizeof *hash);
+        hash->hash_basis = 0;
+        hash->hash_alg = alg;
+        ok = dpif_probe_feature(backer->dpif, "Max dp_hash algorithm", &key,
+                                &actions, NULL);
+        ofpbuf_uninit(&actions);
+        if (ok) {
+            max_alg = alg;
+        } else {
+            break;
+        }
+    }
+
+    VLOG_INFO("%s: Max dp_hash algorithm probed to be %d",
+            dpif_name(backer->dpif), max_alg);
+    return max_alg;
+}
+
 #define CHECK_FEATURE__(NAME, SUPPORT, FIELD, VALUE, ETHTYPE)               \
 static bool                                                                 \
 check_##NAME(struct dpif_backer *backer)                                    \
@@ -1353,6 +1397,7 @@ check_support(struct dpif_backer *backer)
     backer->rt_support.sample_nesting = check_max_sample_nesting(backer);
     backer->rt_support.ct_eventmask = check_ct_eventmask(backer);
     backer->rt_support.ct_clear = check_ct_clear(backer);
+    backer->rt_support.max_hash_alg = check_max_dp_hash_alg(backer);
 
     /* Flow fields. */
     backer->rt_support.odp.ct_state = check_ct_state(backer);
diff --git a/ofproto/ofproto-dpif.h b/ofproto/ofproto-dpif.h
index 47bf7f9..d654947 100644
--- a/ofproto/ofproto-dpif.h
+++ b/ofproto/ofproto-dpif.h
@@ -175,7 +175,10 @@ struct group_dpif *group_dpif_lookup(struct ofproto_dpif *,
     DPIF_SUPPORT_FIELD(bool, ct_eventmask, "Conntrack eventmask")           \
                                                                             \
     /* True if the datapath supports OVS_ACTION_ATTR_CT_CLEAR action. */    \
-    DPIF_SUPPORT_FIELD(bool, ct_clear, "Conntrack clear")
+    DPIF_SUPPORT_FIELD(bool, ct_clear, "Conntrack clear")                   \
+                                                                            \
+    /* Highest supported dp_hash algorithm. */                              \
+    DPIF_SUPPORT_FIELD(size_t, max_hash_alg, "Max dp_hash algorithm")
 
 /* Stores the various features which the corresponding backer supports. */
 struct dpif_backer_support {
-- 
1.9.1



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