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linux/net/openvswitch/datapath.h
Mark Gray b83d23a2a3 openvswitch: Introduce per-cpu upcall dispatch
The Open vSwitch kernel module uses the upcall mechanism to send
packets from kernel space to user space when it misses in the kernel
space flow table. The upcall sends packets via a Netlink socket.
Currently, a Netlink socket is created for every vport. In this way,
there is a 1:1 mapping between a vport and a Netlink socket.
When a packet is received by a vport, if it needs to be sent to
user space, it is sent via the corresponding Netlink socket.

This mechanism, with various iterations of the corresponding user
space code, has seen some limitations and issues:

* On systems with a large number of vports, there is a correspondingly
large number of Netlink sockets which can limit scaling.
(https://bugzilla.redhat.com/show_bug.cgi?id=1526306)
* Packet reordering on upcalls.
(https://bugzilla.redhat.com/show_bug.cgi?id=1844576)
* A thundering herd issue.
(https://bugzilla.redhat.com/show_bug.cgi?id=1834444)

This patch introduces an alternative, feature-negotiated, upcall
mode using a per-cpu dispatch rather than a per-vport dispatch.

In this mode, the Netlink socket to be used for the upcall is
selected based on the CPU of the thread that is executing the upcall.
In this way, it resolves the issues above as:

a) The number of Netlink sockets scales with the number of CPUs
rather than the number of vports.
b) Ordering per-flow is maintained as packets are distributed to
CPUs based on mechanisms such as RSS and flows are distributed
to a single user space thread.
c) Packets from a flow can only wake up one user space thread.

The corresponding user space code can be found at:
https://mail.openvswitch.org/pipermail/ovs-dev/2021-July/385139.html

Bugzilla: https://bugzilla.redhat.com/1844576
Signed-off-by: Mark Gray <mark.d.gray@redhat.com>
Acked-by: Flavio Leitner <fbl@sysclose.org>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2021-07-16 11:06:33 -07:00

288 lines
8.1 KiB
C

/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Copyright (c) 2007-2014 Nicira, Inc.
*/
#ifndef DATAPATH_H
#define DATAPATH_H 1
#include <asm/page.h>
#include <linux/kernel.h>
#include <linux/mutex.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/u64_stats_sync.h>
#include <net/ip_tunnels.h>
#include "conntrack.h"
#include "flow.h"
#include "flow_table.h"
#include "meter.h"
#include "vport-internal_dev.h"
#define DP_MAX_PORTS USHRT_MAX
#define DP_VPORT_HASH_BUCKETS 1024
#define DP_MASKS_REBALANCE_INTERVAL 4000
/**
* struct dp_stats_percpu - per-cpu packet processing statistics for a given
* datapath.
* @n_hit: Number of received packets for which a matching flow was found in
* the flow table.
* @n_miss: Number of received packets that had no matching flow in the flow
* table. The sum of @n_hit and @n_miss is the number of packets that have
* been received by the datapath.
* @n_lost: Number of received packets that had no matching flow in the flow
* table that could not be sent to userspace (normally due to an overflow in
* one of the datapath's queues).
* @n_mask_hit: Number of masks looked up for flow match.
* @n_mask_hit / (@n_hit + @n_missed) will be the average masks looked
* up per packet.
* @n_cache_hit: The number of received packets that had their mask found using
* the mask cache.
*/
struct dp_stats_percpu {
u64 n_hit;
u64 n_missed;
u64 n_lost;
u64 n_mask_hit;
u64 n_cache_hit;
struct u64_stats_sync syncp;
};
/**
* struct dp_nlsk_pids - array of netlink portids of for a datapath.
* This is used when OVS_DP_F_DISPATCH_UPCALL_PER_CPU
* is enabled and must be protected by rcu.
* @rcu: RCU callback head for deferred destruction.
* @n_pids: Size of @pids array.
* @pids: Array storing the Netlink socket PIDs indexed by CPU ID for packets
* that miss the flow table.
*/
struct dp_nlsk_pids {
struct rcu_head rcu;
u32 n_pids;
u32 pids[];
};
/**
* struct datapath - datapath for flow-based packet switching
* @rcu: RCU callback head for deferred destruction.
* @list_node: Element in global 'dps' list.
* @table: flow table.
* @ports: Hash table for ports. %OVSP_LOCAL port always exists. Protected by
* ovs_mutex and RCU.
* @stats_percpu: Per-CPU datapath statistics.
* @net: Reference to net namespace.
* @max_headroom: the maximum headroom of all vports in this datapath; it will
* be used by all the internal vports in this dp.
* @upcall_portids: RCU protected 'struct dp_nlsk_pids'.
*
* Context: See the comment on locking at the top of datapath.c for additional
* locking information.
*/
struct datapath {
struct rcu_head rcu;
struct list_head list_node;
/* Flow table. */
struct flow_table table;
/* Switch ports. */
struct hlist_head *ports;
/* Stats. */
struct dp_stats_percpu __percpu *stats_percpu;
/* Network namespace ref. */
possible_net_t net;
u32 user_features;
u32 max_headroom;
/* Switch meters. */
struct dp_meter_table meter_tbl;
struct dp_nlsk_pids __rcu *upcall_portids;
};
/**
* struct ovs_skb_cb - OVS data in skb CB
* @input_vport: The original vport packet came in on. This value is cached
* when a packet is received by OVS.
* @mru: The maximum received fragement size; 0 if the packet is not
* fragmented.
* @acts_origlen: The netlink size of the flow actions applied to this skb.
* @cutlen: The number of bytes from the packet end to be removed.
*/
struct ovs_skb_cb {
struct vport *input_vport;
u16 mru;
u16 acts_origlen;
u32 cutlen;
};
#define OVS_CB(skb) ((struct ovs_skb_cb *)(skb)->cb)
/**
* struct dp_upcall - metadata to include with a packet to send to userspace
* @cmd: One of %OVS_PACKET_CMD_*.
* @userdata: If nonnull, its variable-length value is passed to userspace as
* %OVS_PACKET_ATTR_USERDATA.
* @portid: Netlink portid to which packet should be sent. If @portid is 0
* then no packet is sent and the packet is accounted in the datapath's @n_lost
* counter.
* @egress_tun_info: If nonnull, becomes %OVS_PACKET_ATTR_EGRESS_TUN_KEY.
* @mru: If not zero, Maximum received IP fragment size.
*/
struct dp_upcall_info {
struct ip_tunnel_info *egress_tun_info;
const struct nlattr *userdata;
const struct nlattr *actions;
int actions_len;
u32 portid;
u8 cmd;
u16 mru;
};
/**
* struct ovs_net - Per net-namespace data for ovs.
* @dps: List of datapaths to enable dumping them all out.
* Protected by genl_mutex.
*/
struct ovs_net {
struct list_head dps;
struct work_struct dp_notify_work;
struct delayed_work masks_rebalance;
#if IS_ENABLED(CONFIG_NETFILTER_CONNCOUNT)
struct ovs_ct_limit_info *ct_limit_info;
#endif
/* Module reference for configuring conntrack. */
bool xt_label;
};
/**
* enum ovs_pkt_hash_types - hash info to include with a packet
* to send to userspace.
* @OVS_PACKET_HASH_SW_BIT: indicates hash was computed in software stack.
* @OVS_PACKET_HASH_L4_BIT: indicates hash is a canonical 4-tuple hash
* over transport ports.
*/
enum ovs_pkt_hash_types {
OVS_PACKET_HASH_SW_BIT = (1ULL << 32),
OVS_PACKET_HASH_L4_BIT = (1ULL << 33),
};
extern unsigned int ovs_net_id;
void ovs_lock(void);
void ovs_unlock(void);
#ifdef CONFIG_LOCKDEP
int lockdep_ovsl_is_held(void);
#else
#define lockdep_ovsl_is_held() 1
#endif
#define ASSERT_OVSL() WARN_ON(!lockdep_ovsl_is_held())
#define ovsl_dereference(p) \
rcu_dereference_protected(p, lockdep_ovsl_is_held())
#define rcu_dereference_ovsl(p) \
rcu_dereference_check(p, lockdep_ovsl_is_held())
static inline struct net *ovs_dp_get_net(const struct datapath *dp)
{
return read_pnet(&dp->net);
}
static inline void ovs_dp_set_net(struct datapath *dp, struct net *net)
{
write_pnet(&dp->net, net);
}
struct vport *ovs_lookup_vport(const struct datapath *dp, u16 port_no);
static inline struct vport *ovs_vport_rcu(const struct datapath *dp, int port_no)
{
WARN_ON_ONCE(!rcu_read_lock_held());
return ovs_lookup_vport(dp, port_no);
}
static inline struct vport *ovs_vport_ovsl_rcu(const struct datapath *dp, int port_no)
{
WARN_ON_ONCE(!rcu_read_lock_held() && !lockdep_ovsl_is_held());
return ovs_lookup_vport(dp, port_no);
}
static inline struct vport *ovs_vport_ovsl(const struct datapath *dp, int port_no)
{
ASSERT_OVSL();
return ovs_lookup_vport(dp, port_no);
}
/* Must be called with rcu_read_lock. */
static inline struct datapath *get_dp_rcu(struct net *net, int dp_ifindex)
{
struct net_device *dev = dev_get_by_index_rcu(net, dp_ifindex);
if (dev) {
struct vport *vport = ovs_internal_dev_get_vport(dev);
if (vport)
return vport->dp;
}
return NULL;
}
/* The caller must hold either ovs_mutex or rcu_read_lock to keep the
* returned dp pointer valid.
*/
static inline struct datapath *get_dp(struct net *net, int dp_ifindex)
{
struct datapath *dp;
WARN_ON_ONCE(!rcu_read_lock_held() && !lockdep_ovsl_is_held());
rcu_read_lock();
dp = get_dp_rcu(net, dp_ifindex);
rcu_read_unlock();
return dp;
}
extern struct notifier_block ovs_dp_device_notifier;
extern struct genl_family dp_vport_genl_family;
DECLARE_STATIC_KEY_FALSE(tc_recirc_sharing_support);
void ovs_dp_process_packet(struct sk_buff *skb, struct sw_flow_key *key);
void ovs_dp_detach_port(struct vport *);
int ovs_dp_upcall(struct datapath *, struct sk_buff *,
const struct sw_flow_key *, const struct dp_upcall_info *,
uint32_t cutlen);
u32 ovs_dp_get_upcall_portid(const struct datapath *dp, uint32_t cpu_id);
const char *ovs_dp_name(const struct datapath *dp);
struct sk_buff *ovs_vport_cmd_build_info(struct vport *vport, struct net *net,
u32 portid, u32 seq, u8 cmd);
int ovs_execute_actions(struct datapath *dp, struct sk_buff *skb,
const struct sw_flow_actions *, struct sw_flow_key *);
void ovs_dp_notify_wq(struct work_struct *work);
int action_fifos_init(void);
void action_fifos_exit(void);
/* 'KEY' must not have any bits set outside of the 'MASK' */
#define OVS_MASKED(OLD, KEY, MASK) ((KEY) | ((OLD) & ~(MASK)))
#define OVS_SET_MASKED(OLD, KEY, MASK) ((OLD) = OVS_MASKED(OLD, KEY, MASK))
#define OVS_NLERR(logging_allowed, fmt, ...) \
do { \
if (logging_allowed && net_ratelimit()) \
pr_info("netlink: " fmt "\n", ##__VA_ARGS__); \
} while (0)
#endif /* datapath.h */