ofproto-dpif: Simplify commit logic.

Before executing an output action, ofproto-dpif must commit the
changes it's made to the flow so they are reflected in the
packet.  This code has been unnecessarily complex.  This patch
attempts to simplify the code in the following ways.

- Commit in fewer places.
In an attempt to provide some optimization, the ofproto-dpif code
separated the commit and output composition steps so things like
flood actions could avoid redundant commits.  This is a case of
premature optimization that makes the code significantly more
difficult to reason about.  With this patch, commits happen only
when really necessary.

- Only perform full commits.
In an attempt to provide some optimization, the ofproto-dpif code
would allow callers to only commit the part of the flow that they
had modified by directly calling the relevant subroutine.  This
practice made the code difficult to reason about and is thus
discontinued.

- Perform all output logic in one function.
All of the logic surrounding the datapath output action has been
placed in the compose_output_action__() function.  Most callers
will use the compose_output_action() function which simply passes
reasonable defaults through to compose_output_action__().

1 files changed, 33 insertions, 41 deletions

diff --git a/ofproto/ofproto-dpif.c b/ofproto/ofproto-dpif.c
index 68a87d59..ead708a8 100644
--- a/ofproto/ofproto-dpif.c
+++ b/ofproto/ofproto-dpif.c
@@ -3654,27 +3654,26 @@ commit_set_ether_addr_action(const struct flow *flow, struct flow *base,
 }
 
 static void
-commit_vlan_action(struct action_xlate_ctx *ctx, ovs_be16 new_tci)
+commit_vlan_action(const struct flow *flow, struct flow *base,
+                   struct ofpbuf *odp_actions)
 {
-    struct flow *base = &ctx->base_flow;
-
-    if (base->vlan_tci == new_tci) {
+    if (base->vlan_tci == flow->vlan_tci) {
         return;
     }
 
     if (base->vlan_tci & htons(VLAN_CFI)) {
-        nl_msg_put_flag(ctx->odp_actions, OVS_ACTION_ATTR_POP_VLAN);
+        nl_msg_put_flag(odp_actions, OVS_ACTION_ATTR_POP_VLAN);
     }
 
-    if (new_tci & htons(VLAN_CFI)) {
+    if (flow->vlan_tci & htons(VLAN_CFI)) {
         struct ovs_action_push_vlan vlan;
 
         vlan.vlan_tpid = htons(ETH_TYPE_VLAN);
-        vlan.vlan_tci = new_tci;
-        nl_msg_put_unspec(ctx->odp_actions, OVS_ACTION_ATTR_PUSH_VLAN,
+        vlan.vlan_tci = flow->vlan_tci;
+        nl_msg_put_unspec(odp_actions, OVS_ACTION_ATTR_PUSH_VLAN,
                           &vlan, sizeof vlan);
     }
-    base->vlan_tci = new_tci;
+    base->vlan_tci = flow->vlan_tci;
 }
 
 static void
@@ -3764,49 +3763,41 @@ commit_odp_actions(struct action_xlate_ctx *ctx)
 
     commit_set_tun_id_action(flow, base, odp_actions);
     commit_set_ether_addr_action(flow, base, odp_actions);
-    commit_vlan_action(ctx, flow->vlan_tci);
+    commit_vlan_action(flow, base, odp_actions);
     commit_set_nw_action(flow, base, odp_actions);
     commit_set_port_action(flow, base, odp_actions);
     commit_set_priority_action(flow, base, odp_actions);
 }
 
 static void
-force_compose_output_action(struct action_xlate_ctx *ctx, uint16_t ofp_port)
+compose_output_action__(struct action_xlate_ctx *ctx, uint16_t ofp_port,
+                        bool check_stp)
 {
     const struct ofport_dpif *ofport = get_ofp_port(ctx->ofproto, ofp_port);
     uint16_t odp_port = ofp_port_to_odp_port(ofp_port);
 
-    if (ofport && ofport->up.opp.config & htonl(OFPPC_NO_FWD)) {
-        return;
+    if (ofport) {
+        if (ofport->up.opp.config & htonl(OFPPC_NO_FWD)
+            || (check_stp && !stp_forward_in_state(ofport->stp_state))) {
+            return;
+        }
+    } else {
+        /* We may not have an ofport record for this port, but it doesn't hurt
+         * to allow forwarding to it anyhow.  Maybe such a port will appear
+         * later and we're pre-populating the flow table.  */
     }
 
+    commit_odp_actions(ctx);
     nl_msg_put_u32(ctx->odp_actions, OVS_ACTION_ATTR_OUTPUT, odp_port);
     ctx->sflow_odp_port = odp_port;
     ctx->sflow_n_outputs++;
+    ctx->nf_output_iface = ofp_port;
 }
 
 static void
 compose_output_action(struct action_xlate_ctx *ctx, uint16_t ofp_port)
 {
-    struct ofport_dpif *ofport = get_ofp_port(ctx->ofproto, ofp_port);
-
-    if (ofport && !stp_forward_in_state(ofport->stp_state)) {
-        /* Forwarding disabled on port. */
-        return;
-    }
-
-    /* We may not have an ofport record for this port, but it doesn't hurt to
-     * allow forwarding to it anyhow.  Maybe such a port will appear later and
-     * we're pre-populating the flow table.  */
-    force_compose_output_action(ctx, ofp_port);
-}
-
-static void
-commit_output_action(struct action_xlate_ctx *ctx, uint16_t ofp_port)
-{
-    commit_odp_actions(ctx);
-    compose_output_action(ctx, ofp_port);
-    ctx->nf_output_iface = ofp_port;
+    compose_output_action__(ctx, ofp_port, true);
 }
 
 static void
@@ -3891,7 +3882,7 @@ flood_packets(struct action_xlate_ctx *ctx, bool all)
         }
 
         if (all) {
-            force_compose_output_action(ctx, ofp_port);
+            compose_output_action__(ctx, ofp_port, false);
         } else if (!(ofport->up.opp.config & htonl(OFPPC_NO_FLOOD))) {
             compose_output_action(ctx, ofp_port);
         }
@@ -3905,6 +3896,7 @@ compose_controller_action(struct action_xlate_ctx *ctx, int len)
 {
     struct user_action_cookie cookie;
 
+    commit_odp_actions(ctx);
     cookie.type = USER_ACTION_COOKIE_CONTROLLER;
     cookie.data = len;
     cookie.n_output = 0;
@@ -3922,7 +3914,7 @@ xlate_output_action__(struct action_xlate_ctx *ctx,
 
     switch (port) {
     case OFPP_IN_PORT:
-        commit_output_action(ctx, ctx->flow.in_port);
+        compose_output_action(ctx, ctx->flow.in_port);
         break;
     case OFPP_TABLE:
         xlate_table_action(ctx, ctx->flow.in_port, ctx->table_id);
@@ -3937,17 +3929,16 @@ xlate_output_action__(struct action_xlate_ctx *ctx,
         flood_packets(ctx, true);
         break;
     case OFPP_CONTROLLER:
-        commit_odp_actions(ctx);
         compose_controller_action(ctx, max_len);
         break;
     case OFPP_LOCAL:
-        commit_output_action(ctx, OFPP_LOCAL);
+        compose_output_action(ctx, OFPP_LOCAL);
         break;
     case OFPP_NONE:
         break;
     default:
         if (port != ctx->flow.in_port) {
-            commit_output_action(ctx, port);
+            compose_output_action(ctx, port);
         }
         break;
     }
@@ -4009,7 +4000,7 @@ xlate_enqueue_action(struct action_xlate_ctx *ctx,
     /* Add datapath actions. */
     flow_priority = ctx->flow.priority;
     ctx->flow.priority = priority;
-    commit_output_action(ctx, ofp_port);
+    compose_output_action(ctx, ofp_port);
     ctx->flow.priority = flow_priority;
 
     /* Update NetFlow output port. */
@@ -4495,7 +4486,7 @@ output_normal(struct action_xlate_ctx *ctx, const struct ofbundle *out_bundle,
 {
     struct ofport_dpif *port;
     uint16_t vid;
-    ovs_be16 tci;
+    ovs_be16 tci, old_tci;
 
     vid = output_vlan_to_vid(out_bundle, vlan);
     if (!out_bundle->bond) {
@@ -4509,6 +4500,7 @@ output_normal(struct action_xlate_ctx *ctx, const struct ofbundle *out_bundle,
         }
     }
 
+    old_tci = ctx->flow.vlan_tci;
     tci = htons(vid);
     if (tci || out_bundle->use_priority_tags) {
         tci |= ctx->flow.vlan_tci & htons(VLAN_PCP_MASK);
@@ -4516,10 +4508,10 @@ output_normal(struct action_xlate_ctx *ctx, const struct ofbundle *out_bundle,
             tci |= htons(VLAN_CFI);
         }
     }
-    commit_vlan_action(ctx, tci);
+    ctx->flow.vlan_tci = tci;
 
     compose_output_action(ctx, port->up.ofp_port);
-    ctx->nf_output_iface = port->up.ofp_port;
+    ctx->flow.vlan_tci = old_tci;
 }
 
 static int