From 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 21 Feb 2023 18:24:12 -0800 Subject: Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next Pull networking updates from Jakub Kicinski: "Core: - Add dedicated kmem_cache for typical/small skb->head, avoid having to access struct page at kfree time, and improve memory use. - Introduce sysctl to set default RPS configuration for new netdevs. - Define Netlink protocol specification format which can be used to describe messages used by each family and auto-generate parsers. Add tools for generating kernel data structures and uAPI headers. - Expose all net/core sysctls inside netns. - Remove 4s sleep in netpoll if carrier is instantly detected on boot. - Add configurable limit of MDB entries per port, and port-vlan. - Continue populating drop reasons throughout the stack. - Retire a handful of legacy Qdiscs and classifiers. Protocols: - Support IPv4 big TCP (TSO frames larger than 64kB). - Add IP_LOCAL_PORT_RANGE socket option, to control local port range on socket by socket basis. - Track and report in procfs number of MPTCP sockets used. - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path manager. - IPv6: don't check net.ipv6.route.max_size and rely on garbage collection to free memory (similarly to IPv4). - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986). - ICMP: add per-rate limit counters. - Add support for user scanning requests in ieee802154. - Remove static WEP support. - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate reporting. - WiFi 7 EHT channel puncturing support (client & AP). BPF: - Add a rbtree data structure following the "next-gen data structure" precedent set by recently added linked list, that is, by using kfunc + kptr instead of adding a new BPF map type. - Expose XDP hints via kfuncs with initial support for RX hash and timestamp metadata. - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to better support decap on GRE tunnel devices not operating in collect metadata. - Improve x86 JIT's codegen for PROBE_MEM runtime error checks. - Remove the need for trace_printk_lock for bpf_trace_printk and bpf_trace_vprintk helpers. - Extend libbpf's bpf_tracing.h support for tracing arguments of kprobes/uprobes and syscall as a special case. - Significantly reduce the search time for module symbols by livepatch and BPF. - Enable cpumasks to be used as kptrs, which is useful for tracing programs tracking which tasks end up running on which CPUs in different time intervals. - Add support for BPF trampoline on s390x and riscv64. - Add capability to export the XDP features supported by the NIC. - Add __bpf_kfunc tag for marking kernel functions as kfuncs. - Add cgroup.memory=nobpf kernel parameter option to disable BPF memory accounting for container environments. Netfilter: - Remove the CLUSTERIP target. It has been marked as obsolete for years, and we still have WARN splats wrt races of the out-of-band /proc interface installed by this target. - Add 'destroy' commands to nf_tables. They are identical to the existing 'delete' commands, but do not return an error if the referenced object (set, chain, rule...) did not exist. Driver API: - Improve cpumask_local_spread() locality to help NICs set the right IRQ affinity on AMD platforms. - Separate C22 and C45 MDIO bus transactions more clearly. - Introduce new DCB table to control DSCP rewrite on egress. - Support configuration of Physical Layer Collision Avoidance (PLCA) Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of shared medium Ethernet. - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing preemption of low priority frames by high priority frames. - Add support for controlling MACSec offload using netlink SET. - Rework devlink instance refcounts to allow registration and de-registration under the instance lock. Split the code into multiple files, drop some of the unnecessarily granular locks and factor out common parts of netlink operation handling. - Add TX frame aggregation parameters (for USB drivers). - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning messages with notifications for debug. - Allow offloading of UDP NEW connections via act_ct. - Add support for per action HW stats in TC. - Support hardware miss to TC action (continue processing in SW from a specific point in the action chain). - Warn if old Wireless Extension user space interface is used with modern cfg80211/mac80211 drivers. Do not support Wireless Extensions for Wi-Fi 7 devices at all. Everyone should switch to using nl80211 interface instead. - Improve the CAN bit timing configuration. Use extack to return error messages directly to user space, update the SJW handling, including the definition of a new default value that will benefit CAN-FD controllers, by increasing their oscillator tolerance. New hardware / drivers: - Ethernet: - nVidia BlueField-3 support (control traffic driver) - Ethernet support for imx93 SoCs - Motorcomm yt8531 gigabit Ethernet PHY - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA) - Microchip LAN8841 PHY (incl. cable diagnostics and PTP) - Amlogic gxl MDIO mux - WiFi: - RealTek RTL8188EU (rtl8xxxu) - Qualcomm Wi-Fi 7 devices (ath12k) - CAN: - Renesas R-Car V4H Drivers: - Bluetooth: - Set Per Platform Antenna Gain (PPAG) for Intel controllers. - Ethernet NICs: - Intel (1G, igc): - support TSN / Qbv / packet scheduling features of i226 model - Intel (100G, ice): - use GNSS subsystem instead of TTY - multi-buffer XDP support - extend support for GPIO pins to E823 devices - nVidia/Mellanox: - update the shared buffer configuration on PFC commands - implement PTP adjphase function for HW offset control - TC support for Geneve and GRE with VF tunnel offload - more efficient crypto key management method - multi-port eswitch support - Netronome/Corigine: - add DCB IEEE support - support IPsec offloading for NFP3800 - Freescale/NXP (enetc): - support XDP_REDIRECT for XDP non-linear buffers - improve reconfig, avoid link flap and waiting for idle - support MAC Merge layer - Other NICs: - sfc/ef100: add basic devlink support for ef100 - ionic: rx_push mode operation (writing descriptors via MMIO) - bnxt: use the auxiliary bus abstraction for RDMA - r8169: disable ASPM and reset bus in case of tx timeout - cpsw: support QSGMII mode for J721e CPSW9G - cpts: support pulse-per-second output - ngbe: add an mdio bus driver - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing - r8152: handle devices with FW with NCM support - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation - virtio-net: support multi buffer XDP - virtio/vsock: replace virtio_vsock_pkt with sk_buff - tsnep: XDP support - Ethernet high-speed switches: - nVidia/Mellanox (mlxsw): - add support for latency TLV (in FW control messages) - Microchip (sparx5): - separate explicit and implicit traffic forwarding rules, make the implicit rules always active - add support for egress DSCP rewrite - IS0 VCAP support (Ingress Classification) - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS etc.) - ES2 VCAP support (Egress Access Control) - support for Per-Stream Filtering and Policing (802.1Q, 8.6.5.1) - Ethernet embedded switches: - Marvell (mv88e6xxx): - add MAB (port auth) offload support - enable PTP receive for mv88e6390 - NXP (ocelot): - support MAC Merge layer - support for the the vsc7512 internal copper phys - Microchip: - lan9303: convert to PHYLINK - lan966x: support TC flower filter statistics - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x - lan937x: support Credit Based Shaper configuration - ksz9477: support Energy Efficient Ethernet - other: - qca8k: convert to regmap read/write API, use bulk operations - rswitch: Improve TX timestamp accuracy - Intel WiFi (iwlwifi): - EHT (Wi-Fi 7) rate reporting - STEP equalizer support: transfer some STEP (connection to radio on platforms with integrated wifi) related parameters from the BIOS to the firmware. - Qualcomm 802.11ax WiFi (ath11k): - IPQ5018 support - Fine Timing Measurement (FTM) responder role support - channel 177 support - MediaTek WiFi (mt76): - per-PHY LED support - mt7996: EHT (Wi-Fi 7) support - Wireless Ethernet Dispatch (WED) reset support - switch to using page pool allocator - RealTek WiFi (rtw89): - support new version of Bluetooth co-existance - Mobile: - rmnet: support TX aggregation" * tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits) page_pool: add a comment explaining the fragment counter usage net: ethtool: fix __ethtool_dev_mm_supported() implementation ethtool: pse-pd: Fix double word in comments xsk: add linux/vmalloc.h to xsk.c sefltests: netdevsim: wait for devlink instance after netns removal selftest: fib_tests: Always cleanup before exit net/mlx5e: Align IPsec ASO result memory to be as required by hardware net/mlx5e: TC, Set CT miss to the specific ct action instance net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG net/mlx5: Refactor tc miss handling to a single function net/mlx5: Kconfig: Make tc offload depend on tc skb extension net/sched: flower: Support hardware miss to tc action net/sched: flower: Move filter handle initialization earlier net/sched: cls_api: Support hardware miss to tc action net/sched: Rename user cookie and act cookie sfc: fix builds without CONFIG_RTC_LIB sfc: clean up some inconsistent indentings net/mlx4_en: Introduce flexible array to silence overflow warning net: lan966x: Fix possible deadlock inside PTP net/ulp: Remove redundant ->clone() test in inet_clone_ulp(). ... --- include/net/net_namespace.h | 544 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 544 insertions(+) create mode 100644 include/net/net_namespace.h (limited to 'include/net/net_namespace.h') diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h new file mode 100644 index 000000000..78beaa765 --- /dev/null +++ b/include/net/net_namespace.h @@ -0,0 +1,544 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Operations on the network namespace + */ +#ifndef __NET_NET_NAMESPACE_H +#define __NET_NET_NAMESPACE_H + +#include +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE) +#include +#endif +#if IS_ENABLED(CONFIG_NF_FLOW_TABLE) +#include +#endif +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +struct user_namespace; +struct proc_dir_entry; +struct net_device; +struct sock; +struct ctl_table_header; +struct net_generic; +struct uevent_sock; +struct netns_ipvs; +struct bpf_prog; + + +#define NETDEV_HASHBITS 8 +#define NETDEV_HASHENTRIES (1 << NETDEV_HASHBITS) + +struct net { + /* First cache line can be often dirtied. + * Do not place here read-mostly fields. + */ + refcount_t passive; /* To decide when the network + * namespace should be freed. + */ + spinlock_t rules_mod_lock; + + atomic_t dev_unreg_count; + + unsigned int dev_base_seq; /* protected by rtnl_mutex */ + int ifindex; + + spinlock_t nsid_lock; + atomic_t fnhe_genid; + + struct list_head list; /* list of network namespaces */ + struct list_head exit_list; /* To linked to call pernet exit + * methods on dead net ( + * pernet_ops_rwsem read locked), + * or to unregister pernet ops + * (pernet_ops_rwsem write locked). + */ + struct llist_node cleanup_list; /* namespaces on death row */ + +#ifdef CONFIG_KEYS + struct key_tag *key_domain; /* Key domain of operation tag */ +#endif + struct user_namespace *user_ns; /* Owning user namespace */ + struct ucounts *ucounts; + struct idr netns_ids; + + struct ns_common ns; + struct ref_tracker_dir refcnt_tracker; + struct ref_tracker_dir notrefcnt_tracker; /* tracker for objects not + * refcounted against netns + */ + struct list_head dev_base_head; + struct proc_dir_entry *proc_net; + struct proc_dir_entry *proc_net_stat; + +#ifdef CONFIG_SYSCTL + struct ctl_table_set sysctls; +#endif + + struct sock *rtnl; /* rtnetlink socket */ + struct sock *genl_sock; + + struct uevent_sock *uevent_sock; /* uevent socket */ + + struct hlist_head *dev_name_head; + struct hlist_head *dev_index_head; + struct raw_notifier_head netdev_chain; + + /* Note that @hash_mix can be read millions times per second, + * it is critical that it is on a read_mostly cache line. + */ + u32 hash_mix; + + struct net_device *loopback_dev; /* The loopback */ + + /* core fib_rules */ + struct list_head rules_ops; + + struct netns_core core; + struct netns_mib mib; + struct netns_packet packet; +#if IS_ENABLED(CONFIG_UNIX) + struct netns_unix unx; +#endif + struct netns_nexthop nexthop; + struct netns_ipv4 ipv4; +#if IS_ENABLED(CONFIG_IPV6) + struct netns_ipv6 ipv6; +#endif +#if IS_ENABLED(CONFIG_IEEE802154_6LOWPAN) + struct netns_ieee802154_lowpan ieee802154_lowpan; +#endif +#if defined(CONFIG_IP_SCTP) || defined(CONFIG_IP_SCTP_MODULE) + struct netns_sctp sctp; +#endif +#ifdef CONFIG_NETFILTER + struct netns_nf nf; +#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE) + struct netns_ct ct; +#endif +#if defined(CONFIG_NF_TABLES) || defined(CONFIG_NF_TABLES_MODULE) + struct netns_nftables nft; +#endif +#if IS_ENABLED(CONFIG_NF_FLOW_TABLE) + struct netns_ft ft; +#endif +#endif +#ifdef CONFIG_WEXT_CORE + struct sk_buff_head wext_nlevents; +#endif + struct net_generic __rcu *gen; + + /* Used to store attached BPF programs */ + struct netns_bpf bpf; + + /* Note : following structs are cache line aligned */ +#ifdef CONFIG_XFRM + struct netns_xfrm xfrm; +#endif + + u64 net_cookie; /* written once */ + +#if IS_ENABLED(CONFIG_IP_VS) + struct netns_ipvs *ipvs; +#endif +#if IS_ENABLED(CONFIG_MPLS) + struct netns_mpls mpls; +#endif +#if IS_ENABLED(CONFIG_CAN) + struct netns_can can; +#endif +#ifdef CONFIG_XDP_SOCKETS + struct netns_xdp xdp; +#endif +#if IS_ENABLED(CONFIG_MCTP) + struct netns_mctp mctp; +#endif +#if IS_ENABLED(CONFIG_CRYPTO_USER) + struct sock *crypto_nlsk; +#endif + struct sock *diag_nlsk; +#if IS_ENABLED(CONFIG_SMC) + struct netns_smc smc; +#endif +} __randomize_layout; + +#include + +/* Init's network namespace */ +extern struct net init_net; + +#ifdef CONFIG_NET_NS +struct net *copy_net_ns(unsigned long flags, struct user_namespace *user_ns, + struct net *old_net); + +void net_ns_get_ownership(const struct net *net, kuid_t *uid, kgid_t *gid); + +void net_ns_barrier(void); + +struct ns_common *get_net_ns(struct ns_common *ns); +struct net *get_net_ns_by_fd(int fd); +#else /* CONFIG_NET_NS */ +#include +#include +static inline struct net *copy_net_ns(unsigned long flags, + struct user_namespace *user_ns, struct net *old_net) +{ + if (flags & CLONE_NEWNET) + return ERR_PTR(-EINVAL); + return old_net; +} + +static inline void net_ns_get_ownership(const struct net *net, + kuid_t *uid, kgid_t *gid) +{ + *uid = GLOBAL_ROOT_UID; + *gid = GLOBAL_ROOT_GID; +} + +static inline void net_ns_barrier(void) {} + +static inline struct ns_common *get_net_ns(struct ns_common *ns) +{ + return ERR_PTR(-EINVAL); +} + +static inline struct net *get_net_ns_by_fd(int fd) +{ + return ERR_PTR(-EINVAL); +} +#endif /* CONFIG_NET_NS */ + + +extern struct list_head net_namespace_list; + +struct net *get_net_ns_by_pid(pid_t pid); + +#ifdef CONFIG_SYSCTL +void ipx_register_sysctl(void); +void ipx_unregister_sysctl(void); +#else +#define ipx_register_sysctl() +#define ipx_unregister_sysctl() +#endif + +#ifdef CONFIG_NET_NS +void __put_net(struct net *net); + +/* Try using get_net_track() instead */ +static inline struct net *get_net(struct net *net) +{ + refcount_inc(&net->ns.count); + return net; +} + +static inline struct net *maybe_get_net(struct net *net) +{ + /* Used when we know struct net exists but we + * aren't guaranteed a previous reference count + * exists. If the reference count is zero this + * function fails and returns NULL. + */ + if (!refcount_inc_not_zero(&net->ns.count)) + net = NULL; + return net; +} + +/* Try using put_net_track() instead */ +static inline void put_net(struct net *net) +{ + if (refcount_dec_and_test(&net->ns.count)) + __put_net(net); +} + +static inline +int net_eq(const struct net *net1, const struct net *net2) +{ + return net1 == net2; +} + +static inline int check_net(const struct net *net) +{ + return refcount_read(&net->ns.count) != 0; +} + +void net_drop_ns(void *); + +#else + +static inline struct net *get_net(struct net *net) +{ + return net; +} + +static inline void put_net(struct net *net) +{ +} + +static inline struct net *maybe_get_net(struct net *net) +{ + return net; +} + +static inline +int net_eq(const struct net *net1, const struct net *net2) +{ + return 1; +} + +static inline int check_net(const struct net *net) +{ + return 1; +} + +#define net_drop_ns NULL +#endif + + +static inline void __netns_tracker_alloc(struct net *net, + netns_tracker *tracker, + bool refcounted, + gfp_t gfp) +{ +#ifdef CONFIG_NET_NS_REFCNT_TRACKER + ref_tracker_alloc(refcounted ? &net->refcnt_tracker : + &net->notrefcnt_tracker, + tracker, gfp); +#endif +} + +static inline void netns_tracker_alloc(struct net *net, netns_tracker *tracker, + gfp_t gfp) +{ + __netns_tracker_alloc(net, tracker, true, gfp); +} + +static inline void __netns_tracker_free(struct net *net, + netns_tracker *tracker, + bool refcounted) +{ +#ifdef CONFIG_NET_NS_REFCNT_TRACKER + ref_tracker_free(refcounted ? &net->refcnt_tracker : + &net->notrefcnt_tracker, tracker); +#endif +} + +static inline struct net *get_net_track(struct net *net, + netns_tracker *tracker, gfp_t gfp) +{ + get_net(net); + netns_tracker_alloc(net, tracker, gfp); + return net; +} + +static inline void put_net_track(struct net *net, netns_tracker *tracker) +{ + __netns_tracker_free(net, tracker, true); + put_net(net); +} + +typedef struct { +#ifdef CONFIG_NET_NS + struct net *net; +#endif +} possible_net_t; + +static inline void write_pnet(possible_net_t *pnet, struct net *net) +{ +#ifdef CONFIG_NET_NS + pnet->net = net; +#endif +} + +static inline struct net *read_pnet(const possible_net_t *pnet) +{ +#ifdef CONFIG_NET_NS + return pnet->net; +#else + return &init_net; +#endif +} + +/* Protected by net_rwsem */ +#define for_each_net(VAR) \ + list_for_each_entry(VAR, &net_namespace_list, list) +#define for_each_net_continue_reverse(VAR) \ + list_for_each_entry_continue_reverse(VAR, &net_namespace_list, list) +#define for_each_net_rcu(VAR) \ + list_for_each_entry_rcu(VAR, &net_namespace_list, list) + +#ifdef CONFIG_NET_NS +#define __net_init +#define __net_exit +#define __net_initdata +#define __net_initconst +#else +#define __net_init __init +#define __net_exit __ref +#define __net_initdata __initdata +#define __net_initconst __initconst +#endif + +int peernet2id_alloc(struct net *net, struct net *peer, gfp_t gfp); +int peernet2id(const struct net *net, struct net *peer); +bool peernet_has_id(const struct net *net, struct net *peer); +struct net *get_net_ns_by_id(const struct net *net, int id); + +struct pernet_operations { + struct list_head list; + /* + * Below methods are called without any exclusive locks. + * More than one net may be constructed and destructed + * in parallel on several cpus. Every pernet_operations + * have to keep in mind all other pernet_operations and + * to introduce a locking, if they share common resources. + * + * The only time they are called with exclusive lock is + * from register_pernet_subsys(), unregister_pernet_subsys() + * register_pernet_device() and unregister_pernet_device(). + * + * Exit methods using blocking RCU primitives, such as + * synchronize_rcu(), should be implemented via exit_batch. + * Then, destruction of a group of net requires single + * synchronize_rcu() related to these pernet_operations, + * instead of separate synchronize_rcu() for every net. + * Please, avoid synchronize_rcu() at all, where it's possible. + * + * Note that a combination of pre_exit() and exit() can + * be used, since a synchronize_rcu() is guaranteed between + * the calls. + */ + int (*init)(struct net *net); + void (*pre_exit)(struct net *net); + void (*exit)(struct net *net); + void (*exit_batch)(struct list_head *net_exit_list); + unsigned int *id; + size_t size; +}; + +/* + * Use these carefully. If you implement a network device and it + * needs per network namespace operations use device pernet operations, + * otherwise use pernet subsys operations. + * + * Network interfaces need to be removed from a dying netns _before_ + * subsys notifiers can be called, as most of the network code cleanup + * (which is done from subsys notifiers) runs with the assumption that + * dev_remove_pack has been called so no new packets will arrive during + * and after the cleanup functions have been called. dev_remove_pack + * is not per namespace so instead the guarantee of no more packets + * arriving in a network namespace is provided by ensuring that all + * network devices and all sockets have left the network namespace + * before the cleanup methods are called. + * + * For the longest time the ipv4 icmp code was registered as a pernet + * device which caused kernel oops, and panics during network + * namespace cleanup. So please don't get this wrong. + */ +int register_pernet_subsys(struct pernet_operations *); +void unregister_pernet_subsys(struct pernet_operations *); +int register_pernet_device(struct pernet_operations *); +void unregister_pernet_device(struct pernet_operations *); + +struct ctl_table; + +#ifdef CONFIG_SYSCTL +int net_sysctl_init(void); +struct ctl_table_header *register_net_sysctl(struct net *net, const char *path, + struct ctl_table *table); +void unregister_net_sysctl_table(struct ctl_table_header *header); +#else +static inline int net_sysctl_init(void) { return 0; } +static inline struct ctl_table_header *register_net_sysctl(struct net *net, + const char *path, struct ctl_table *table) +{ + return NULL; +} +static inline void unregister_net_sysctl_table(struct ctl_table_header *header) +{ +} +#endif + +static inline int rt_genid_ipv4(const struct net *net) +{ + return atomic_read(&net->ipv4.rt_genid); +} + +#if IS_ENABLED(CONFIG_IPV6) +static inline int rt_genid_ipv6(const struct net *net) +{ + return atomic_read(&net->ipv6.fib6_sernum); +} +#endif + +static inline void rt_genid_bump_ipv4(struct net *net) +{ + atomic_inc(&net->ipv4.rt_genid); +} + +extern void (*__fib6_flush_trees)(struct net *net); +static inline void rt_genid_bump_ipv6(struct net *net) +{ + if (__fib6_flush_trees) + __fib6_flush_trees(net); +} + +#if IS_ENABLED(CONFIG_IEEE802154_6LOWPAN) +static inline struct netns_ieee802154_lowpan * +net_ieee802154_lowpan(struct net *net) +{ + return &net->ieee802154_lowpan; +} +#endif + +/* For callers who don't really care about whether it's IPv4 or IPv6 */ +static inline void rt_genid_bump_all(struct net *net) +{ + rt_genid_bump_ipv4(net); + rt_genid_bump_ipv6(net); +} + +static inline int fnhe_genid(const struct net *net) +{ + return atomic_read(&net->fnhe_genid); +} + +static inline void fnhe_genid_bump(struct net *net) +{ + atomic_inc(&net->fnhe_genid); +} + +#ifdef CONFIG_NET +void net_ns_init(void); +#else +static inline void net_ns_init(void) {} +#endif + +#endif /* __NET_NET_NAMESPACE_H */ -- cgit v1.2.3