/*
- * Copyright (c) 2008, 2009, 2010, 2011, 2012 Nicira Networks.
+ * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* limitations under the License.
*/
-
+/*
+ * dpif, the DataPath InterFace.
+ *
+ * In Open vSwitch terminology, a "datapath" is a flow-based software switch.
+ * A datapath has no intelligence of its own. Rather, it relies entirely on
+ * its client to set up flows. The datapath layer is core to the Open vSwitch
+ * software switch: one could say, without much exaggeration, that everything
+ * in ovs-vswitchd above dpif exists only to make the correct decisions
+ * interacting with dpif.
+ *
+ * Typically, the client of a datapath is the software switch module in
+ * "ovs-vswitchd", but other clients can be written. The "ovs-dpctl" utility
+ * is also a (simple) client.
+ *
+ *
+ * Overview
+ * ========
+ *
+ * The terms written in quotes below are defined in later sections.
+ *
+ * When a datapath "port" receives a packet, it extracts the headers (the
+ * "flow"). If the datapath's "flow table" contains a "flow entry" whose flow
+ * is the same as the packet's, then it executes the "actions" in the flow
+ * entry and increments the flow's statistics. If there is no matching flow
+ * entry, the datapath instead appends the packet to an "upcall" queue.
+ *
+ *
+ * Ports
+ * =====
+ *
+ * A datapath has a set of ports that are analogous to the ports on an Ethernet
+ * switch. At the datapath level, each port has the following information
+ * associated with it:
+ *
+ * - A name, a short string that must be unique within the host. This is
+ * typically a name that would be familiar to the system administrator,
+ * e.g. "eth0" or "vif1.1", but it is otherwise arbitrary.
+ *
+ * - A 32-bit port number that must be unique within the datapath but is
+ * otherwise arbitrary. The port number is the most important identifier
+ * for a port in the datapath interface.
+ *
+ * - A type, a short string that identifies the kind of port. On a Linux
+ * host, typical types are "system" (for a network device such as eth0),
+ * "internal" (for a simulated port used to connect to the TCP/IP stack),
+ * and "gre" (for a GRE tunnel).
+ *
+ * - A Netlink PID (see "Upcall Queuing and Ordering" below).
+ *
+ * The dpif interface has functions for adding and deleting ports. When a
+ * datapath implements these (e.g. as the Linux and netdev datapaths do), then
+ * Open vSwitch's ovs-vswitchd daemon can directly control what ports are used
+ * for switching. Some datapaths might not implement them, or implement them
+ * with restrictions on the types of ports that can be added or removed
+ * (e.g. on ESX), on systems where port membership can only be changed by some
+ * external entity.
+ *
+ * Each datapath must have a port, sometimes called the "local port", whose
+ * name is the same as the datapath itself, with port number 0. The local port
+ * cannot be deleted.
+ *
+ * Ports are available as "struct netdev"s. To obtain a "struct netdev *" for
+ * a port named 'name' with type 'port_type', in a datapath of type
+ * 'datapath_type', call netdev_open(name, dpif_port_open_type(datapath_type,
+ * port_type). The netdev can be used to get and set important data related to
+ * the port, such as:
+ *
+ * - MTU (netdev_get_mtu(), netdev_set_mtu()).
+ *
+ * - Ethernet address (netdev_get_etheraddr(), netdev_set_etheraddr()).
+ *
+ * - Statistics such as the number of packets and bytes transmitted and
+ * received (netdev_get_stats()).
+ *
+ * - Carrier status (netdev_get_carrier()).
+ *
+ * - Speed (netdev_get_features()).
+ *
+ * - QoS queue configuration (netdev_get_queue(), netdev_set_queue() and
+ * related functions.)
+ *
+ * - Arbitrary port-specific configuration parameters (netdev_get_config(),
+ * netdev_set_config()). An example of such a parameter is the IP
+ * endpoint for a GRE tunnel.
+ *
+ *
+ * Flow Table
+ * ==========
+ *
+ * The flow table is a hash table of "flow entries". Each flow entry contains:
+ *
+ * - A "flow", that is, a summary of the headers in an Ethernet packet. The
+ * flow is the hash key and thus must be unique within the flow table.
+ * Flows are fine-grained entities that include L2, L3, and L4 headers. A
+ * single TCP connection consists of two flows, one in each direction.
+ *
+ * In Open vSwitch userspace, "struct flow" is the typical way to describe
+ * a flow, but the datapath interface uses a different data format to
+ * allow ABI forward- and backward-compatibility. datapath/README
+ * describes the rationale and design. Refer to OVS_KEY_ATTR_* and
+ * "struct ovs_key_*" in include/linux/openvswitch.h for details.
+ * lib/odp-util.h defines several functions for working with these flows.
+ *
+ * (In case you are familiar with OpenFlow, datapath flows are analogous
+ * to OpenFlow flow matches. The most important difference is that
+ * OpenFlow allows fields to be wildcarded and prioritized, whereas a
+ * datapath's flow table is a hash table so every flow must be
+ * exact-match, thus without priorities.)
+ *
+ * - A list of "actions" that tell the datapath what to do with packets
+ * within a flow. Some examples of actions are OVS_ACTION_ATTR_OUTPUT,
+ * which transmits the packet out a port, and OVS_ACTION_ATTR_SET, which
+ * modifies packet headers. Refer to OVS_ACTION_ATTR_* and "struct
+ * ovs_action_*" in include/linux/openvswitch.h for details.
+ * lib/odp-util.h defines several functions for working with datapath
+ * actions.
+ *
+ * The actions list may be empty. This indicates that nothing should be
+ * done to matching packets, that is, they should be dropped.
+ *
+ * (In case you are familiar with OpenFlow, datapath actions are analogous
+ * to OpenFlow actions.)
+ *
+ * - Statistics: the number of packets and bytes that the flow has
+ * processed, the last time that the flow processed a packet, and the
+ * union of all the TCP flags in packets processed by the flow. (The
+ * latter is 0 if the flow is not a TCP flow.)
+ *
+ * The datapath's client manages the flow table, primarily in reaction to
+ * "upcalls" (see below).
+ *
+ *
+ * Upcalls
+ * =======
+ *
+ * A datapath sometimes needs to notify its client that a packet was received.
+ * The datapath mechanism to do this is called an "upcall".
+ *
+ * Upcalls are used in two situations:
+ *
+ * - When a packet is received, but there is no matching flow entry in its
+ * flow table (a flow table "miss"), this causes an upcall of type
+ * DPIF_UC_MISS. These are called "miss" upcalls.
+ *
+ * - A datapath action of type OVS_ACTION_ATTR_USERSPACE causes an upcall of
+ * type DPIF_UC_ACTION. These are called "action" upcalls.
+ *
+ * An upcall contains an entire packet. There is no attempt to, e.g., copy
+ * only as much of the packet as normally needed to make a forwarding decision.
+ * Such an optimization is doable, but experimental prototypes showed it to be
+ * of little benefit because an upcall typically contains the first packet of a
+ * flow, which is usually short (e.g. a TCP SYN). Also, the entire packet can
+ * sometimes really be needed.
+ *
+ * After a client reads a given upcall, the datapath is finished with it, that
+ * is, the datapath doesn't maintain any lingering state past that point.
+ *
+ * The latency from the time that a packet arrives at a port to the time that
+ * it is received from dpif_recv() is critical in some benchmarks. For
+ * example, if this latency is 1 ms, then a netperf TCP_CRR test, which opens
+ * and closes TCP connections one at a time as quickly as it can, cannot
+ * possibly achieve more than 500 transactions per second, since every
+ * connection consists of two flows with 1-ms latency to set up each one.
+ *
+ * To receive upcalls, a client has to enable them with dpif_recv_set(). A
+ * datapath should generally support multiple clients at once (e.g. so that one
+ * may run "ovs-dpctl show" or "ovs-dpctl dump-flows" while "ovs-vswitchd" is
+ * also running) but need not support multiple clients enabling upcalls at
+ * once.
+ *
+ *
+ * Upcall Queuing and Ordering
+ * ---------------------------
+ *
+ * The datapath's client reads upcalls one at a time by calling dpif_recv().
+ * When more than one upcall is pending, the order in which the datapath
+ * presents upcalls to its client is important. The datapath's client does not
+ * directly control this order, so the datapath implementer must take care
+ * during design.
+ *
+ * The minimal behavior, suitable for initial testing of a datapath
+ * implementation, is that all upcalls are appended to a single queue, which is
+ * delivered to the client in order.
+ *
+ * The datapath should ensure that a high rate of upcalls from one particular
+ * port cannot cause upcalls from other sources to be dropped or unreasonably
+ * delayed. Otherwise, one port conducting a port scan or otherwise initiating
+ * high-rate traffic spanning many flows could suppress other traffic.
+ * Ideally, the datapath should present upcalls from each port in a "round
+ * robin" manner, to ensure fairness.
+ *
+ * The client has no control over "miss" upcalls and no insight into the
+ * datapath's implementation, so the datapath is entirely responsible for
+ * queuing and delivering them. On the other hand, the datapath has
+ * considerable freedom of implementation. One good approach is to maintain a
+ * separate queue for each port, to prevent any given port's upcalls from
+ * interfering with other ports' upcalls. If this is impractical, then another
+ * reasonable choice is to maintain some fixed number of queues and assign each
+ * port to one of them. Ports assigned to the same queue can then interfere
+ * with each other, but not with ports assigned to different queues. Other
+ * approaches are also possible.
+ *
+ * The client has some control over "action" upcalls: it can specify a 32-bit
+ * "Netlink PID" as part of the action. This terminology comes from the Linux
+ * datapath implementation, which uses a protocol called Netlink in which a PID
+ * designates a particular socket and the upcall data is delivered to the
+ * socket's receive queue. Generically, though, a Netlink PID identifies a
+ * queue for upcalls. The basic requirements on the datapath are:
+ *
+ * - The datapath must provide a Netlink PID associated with each port. The
+ * client can retrieve the PID with dpif_port_get_pid().
+ *
+ * - The datapath must provide a "special" Netlink PID not associated with
+ * any port. dpif_port_get_pid() also provides this PID. (ovs-vswitchd
+ * uses this PID to queue special packets that must not be lost even if a
+ * port is otherwise busy, such as packets used for tunnel monitoring.)
+ *
+ * The minimal behavior of dpif_port_get_pid() and the treatment of the Netlink
+ * PID in "action" upcalls is that dpif_port_get_pid() returns a constant value
+ * and all upcalls are appended to a single queue.
+ *
+ * The ideal behavior is:
+ *
+ * - Each port has a PID that identifies the queue used for "miss" upcalls
+ * on that port. (Thus, if each port has its own queue for "miss"
+ * upcalls, then each port has a different Netlink PID.)
+ *
+ * - "miss" upcalls for a given port and "action" upcalls that specify that
+ * port's Netlink PID add their upcalls to the same queue. The upcalls
+ * are delivered to the datapath's client in the order that the packets
+ * were received, regardless of whether the upcalls are "miss" or "action"
+ * upcalls.
+ *
+ * - Upcalls that specify the "special" Netlink PID are queued separately.
+ *
+ *
+ * Packet Format
+ * =============
+ *
+ * The datapath interface works with packets in a particular form. This is the
+ * form taken by packets received via upcalls (i.e. by dpif_recv()). Packets
+ * supplied to the datapath for processing (i.e. to dpif_execute()) also take
+ * this form.
+ *
+ * A VLAN tag is represented by an 802.1Q header. If the layer below the
+ * datapath interface uses another representation, then the datapath interface
+ * must perform conversion.
+ *
+ * The datapath interface requires all packets to fit within the MTU. Some
+ * operating systems internally process packets larger than MTU, with features
+ * such as TSO and UFO. When such a packet passes through the datapath
+ * interface, it must be broken into multiple MTU or smaller sized packets for
+ * presentation as upcalls. (This does not happen often, because an upcall
+ * typically contains the first packet of a flow, which is usually short.)
+ *
+ * Some operating system TCP/IP stacks maintain packets in an unchecksummed or
+ * partially checksummed state until transmission. The datapath interface
+ * requires all host-generated packets to be fully checksummed (e.g. IP and TCP
+ * checksums must be correct). On such an OS, the datapath interface must fill
+ * in these checksums.
+ *
+ * Packets passed through the datapath interface must be at least 14 bytes
+ * long, that is, they must have a complete Ethernet header. They are not
+ * required to be padded to the minimum Ethernet length.
+ *
+ *
+ * Typical Usage
+ * =============
+ *
+ * Typically, the client of a datapath begins by configuring the datapath with
+ * a set of ports. Afterward, the client runs in a loop polling for upcalls to
+ * arrive.
+ *
+ * For each upcall received, the client examines the enclosed packet and
+ * figures out what should be done with it. For example, if the client
+ * implements a MAC-learning switch, then it searches the forwarding database
+ * for the packet's destination MAC and VLAN and determines the set of ports to
+ * which it should be sent. In any case, the client composes a set of datapath
+ * actions to properly dispatch the packet and then directs the datapath to
+ * execute those actions on the packet (e.g. with dpif_execute()).
+ *
+ * Most of the time, the actions that the client executed on the packet apply
+ * to every packet with the same flow. For example, the flow includes both
+ * destination MAC and VLAN ID (and much more), so this is true for the
+ * MAC-learning switch example above. In such a case, the client can also
+ * direct the datapath to treat any further packets in the flow in the same
+ * way, using dpif_flow_put() to add a new flow entry.
+ *
+ * Other tasks the client might need to perform, in addition to reacting to
+ * upcalls, include:
+ *
+ * - Periodically polling flow statistics, perhaps to supply to its own
+ * clients.
+ *
+ * - Deleting flow entries from the datapath that haven't been used
+ * recently, to save memory.
+ *
+ * - Updating flow entries whose actions should change. For example, if a
+ * MAC learning switch learns that a MAC has moved, then it must update
+ * the actions of flow entries that sent packets to the MAC at its old
+ * location.
+ *
+ * - Adding and removing ports to achieve a new configuration.
+ *
+ *
+ * Thread-safety
+ * =============
+ *
+ * Most of the dpif functions are fully thread-safe: they may be called from
+ * any number of threads on the same or different dpif objects. The exceptions
+ * are:
+ *
+ * - dpif_port_poll() and dpif_port_poll_wait() are conditionally
+ * thread-safe: they may be called from different threads only on
+ * different dpif objects.
+ *
+ * - Functions that operate on struct dpif_port_dump or struct
+ * dpif_flow_dump are conditionally thread-safe with respect to those
+ * objects. That is, one may dump ports or flows from any number of
+ * threads at once, but each thread must use its own struct dpif_port_dump
+ * or dpif_flow_dump.
+ */
#ifndef DPIF_H
#define DPIF_H 1
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
-#include <linux/openvswitch.h>
#include "openflow/openflow.h"
#include "netdev.h"
#include "util.h"
const char *dpif_name(const struct dpif *);
const char *dpif_base_name(const struct dpif *);
+const char *dpif_type(const struct dpif *);
int dpif_delete(struct dpif *);
-/* Statisticss for a dpif as a whole. */
+/* Statistics for a dpif as a whole. */
struct dpif_dp_stats {
uint64_t n_hit; /* Number of flow table matches. */
uint64_t n_missed; /* Number of flow table misses. */
\f
/* Port operations. */
-int dpif_port_add(struct dpif *, struct netdev *, uint16_t *port_nop);
-int dpif_port_del(struct dpif *, uint16_t port_no);
+const char *dpif_port_open_type(const char *datapath_type,
+ const char *port_type);
+int dpif_port_add(struct dpif *, struct netdev *, odp_port_t *port_nop);
+int dpif_port_del(struct dpif *, odp_port_t port_no);
/* A port within a datapath.
*
struct dpif_port {
char *name; /* Network device name, e.g. "eth0". */
char *type; /* Network device type, e.g. "system". */
- uint32_t port_no; /* Port number within datapath. */
+ odp_port_t port_no; /* Port number within datapath. */
};
void dpif_port_clone(struct dpif_port *, const struct dpif_port *);
void dpif_port_destroy(struct dpif_port *);
-int dpif_port_query_by_number(const struct dpif *, uint16_t port_no,
+bool dpif_port_exists(const struct dpif *dpif, const char *devname);
+int dpif_port_query_by_number(const struct dpif *, odp_port_t port_no,
struct dpif_port *);
int dpif_port_query_by_name(const struct dpif *, const char *devname,
struct dpif_port *);
-int dpif_port_get_name(struct dpif *, uint16_t port_no,
+int dpif_port_get_name(struct dpif *, odp_port_t port_no,
char *name, size_t name_size);
-int dpif_get_max_ports(const struct dpif *);
-uint32_t dpif_port_get_pid(const struct dpif *, uint16_t port_no);
+uint32_t dpif_get_max_ports(const struct dpif *);
+uint32_t dpif_port_get_pid(const struct dpif *, odp_port_t port_no);
struct dpif_port_dump {
const struct dpif *dpif;
};
void dpif_flow_stats_extract(const struct flow *, const struct ofpbuf *packet,
- struct dpif_flow_stats *);
+ long long int used, struct dpif_flow_stats *);
void dpif_flow_stats_format(const struct dpif_flow_stats *, struct ds *);
enum dpif_flow_put_flags {
int dpif_flow_flush(struct dpif *);
int dpif_flow_put(struct dpif *, enum dpif_flow_put_flags,
const struct nlattr *key, size_t key_len,
+ const struct nlattr *mask, size_t mask_len,
const struct nlattr *actions, size_t actions_len,
struct dpif_flow_stats *);
int dpif_flow_del(struct dpif *,
void dpif_flow_dump_start(struct dpif_flow_dump *, const struct dpif *);
bool dpif_flow_dump_next(struct dpif_flow_dump *,
const struct nlattr **key, size_t *key_len,
+ const struct nlattr **mask, size_t *mask_len,
const struct nlattr **actions, size_t *actions_len,
const struct dpif_flow_stats **);
int dpif_flow_dump_done(struct dpif_flow_dump *);
int dpif_execute(struct dpif *,
const struct nlattr *key, size_t key_len,
const struct nlattr *actions, size_t actions_len,
- const struct ofpbuf *);
+ const struct ofpbuf *,
+ bool needs_help);
\f
/* Operation batching interface.
*
enum dpif_flow_put_flags flags; /* DPIF_FP_*. */
const struct nlattr *key; /* Flow to put. */
size_t key_len; /* Length of 'key' in bytes. */
+ const struct nlattr *mask; /* Mask to put. */
+ size_t mask_len; /* Length of 'mask' in bytes. */
const struct nlattr *actions; /* Actions to perform on flow. */
size_t actions_len; /* Length of 'actions' in bytes. */
};
struct dpif_execute {
+ /* Raw support for execute passed along to the provider. */
const struct nlattr *key; /* Partial flow key (only for metadata). */
size_t key_len; /* Length of 'key' in bytes. */
const struct nlattr *actions; /* Actions to execute on packet. */
size_t actions_len; /* Length of 'actions' in bytes. */
const struct ofpbuf *packet; /* Packet to execute. */
+
+ /* Some dpif providers do not implement every action. The Linux kernel
+ * datapath, in particular, does not implement ARP field modification.
+ *
+ * If this member is set to true, the dpif layer executes in userspace all
+ * of the actions that it can, and for OVS_ACTION_ATTR_OUTPUT and
+ * OVS_ACTION_ATTR_USERSPACE actions it passes the packet through to the
+ * dpif implementation. */
+ bool needs_help;
};
struct dpif_op {
/* A packet passed up from the datapath to userspace.
*
- * If 'key' or 'actions' is nonnull, then it points into data owned by
- * 'packet', so their memory cannot be freed separately. (This is hardly a
- * great way to do things but it works out OK for the dpif providers and
- * clients that exist so far.)
+ * If 'key', 'actions', or 'userdata' is nonnull, then it points into data
+ * owned by 'packet', so their memory cannot be freed separately. (This is
+ * hardly a great way to do things but it works out OK for the dpif providers
+ * and clients that exist so far.)
*/
struct dpif_upcall {
/* All types. */
size_t key_len; /* Length of 'key' in bytes. */
/* DPIF_UC_ACTION only. */
- uint64_t userdata; /* Argument to OVS_ACTION_ATTR_USERSPACE. */
+ struct nlattr *userdata; /* Argument to OVS_ACTION_ATTR_USERSPACE. */
};
int dpif_recv_set(struct dpif *, bool enable);