ovs_be16 initial_tci, struct rule_dpif *rule,
uint8_t tcp_flags, const struct ofpbuf *packet)
{
+ ovs_be64 initial_tun_id = flow->tunnel.tun_id;
+
+ /* Flow initialization rules:
+ * - 'base_flow' must match the kernel's view of the packet at the
+ * time that action processing starts. 'flow' represents any
+ * transformations we wish to make through actions.
+ * - By default 'base_flow' and 'flow' are the same since the input
+ * packet matches the output before any actions are applied.
+ * - When using VLAN splinters, 'base_flow''s VLAN is set to the value
+ * of the received packet as seen by the kernel. If we later output
+ * to another device without any modifications this will cause us to
+ * insert a new tag since the original one was stripped off by the
+ * VLAN device.
+ * - Tunnel 'flow' is largely cleared when transitioning between
+ * the input and output stages since it does not make sense to output
+ * a packet with the exact headers that it was received with (i.e.
+ * the destination IP is us). The one exception is the tun_id, which
+ * is preserved to allow use in later resubmit lookups and loads into
+ * registers.
+ * - Tunnel 'base_flow' is completely cleared since that is what the
+ * kernel does. If we wish to maintain the original values an action
+ * needs to be generated. */
+
ctx->ofproto = ofproto;
ctx->flow = *flow;
memset(&ctx->flow.tunnel, 0, sizeof ctx->flow.tunnel);
ctx->base_flow = ctx->flow;
ctx->base_flow.vlan_tci = initial_tci;
+ ctx->flow.tunnel.tun_id = initial_tun_id;
ctx->rule = rule;
ctx->packet = packet;
ctx->may_learn = packet != NULL;