2 * Linux ethernet bridge
5 * Lennert Buytenhek <buytenh@gnu.org>
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; either version
10 * 2 of the License, or (at your option) any later version.
16 #include <linux/netdevice.h>
17 #include <linux/if_bridge.h>
18 #include <linux/netpoll.h>
19 #include <linux/u64_stats_sync.h>
20 #include <net/route.h>
21 #include <linux/if_vlan.h>
23 #define BR_HASH_BITS 8
24 #define BR_HASH_SIZE (1 << BR_HASH_BITS)
26 #define BR_HOLD_TIME (1*HZ)
28 #define BR_PORT_BITS 10
29 #define BR_MAX_PORTS (1<<BR_PORT_BITS)
30 #define BR_VLAN_BITMAP_LEN BITS_TO_LONGS(VLAN_N_VID)
32 #define BR_VERSION "2.3"
34 /* Control of forwarding link local multicast */
35 #define BR_GROUPFWD_DEFAULT 0
36 /* Don't allow forwarding control protocols like STP and LLDP */
37 #define BR_GROUPFWD_RESTRICTED 0x4007u
39 /* Path to usermode spanning tree program */
40 #define BR_STP_PROG "/sbin/bridge-stp"
42 typedef struct bridge_id bridge_id;
43 typedef struct mac_addr mac_addr;
44 typedef __u16 port_id;
48 unsigned char prio[2];
49 unsigned char addr[ETH_ALEN];
54 unsigned char addr[ETH_ALEN];
61 #if IS_ENABLED(CONFIG_IPV6)
69 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
71 struct bridge_mcast_query {
72 struct timer_list timer;
77 struct bridge_mcast_querier {
78 struct timer_list timer;
79 unsigned long delay_time;
83 struct net_port_vlans {
87 struct net_bridge_port *port;
88 struct net_bridge *br;
91 unsigned long vlan_bitmap[BR_VLAN_BITMAP_LEN];
92 unsigned long untagged_bitmap[BR_VLAN_BITMAP_LEN];
96 struct net_bridge_fdb_entry
98 struct hlist_node hlist;
99 struct net_bridge_port *dst;
102 unsigned long updated;
105 unsigned char is_local;
106 unsigned char is_static;
107 unsigned char added_by_user;
111 struct net_bridge_port_group {
112 struct net_bridge_port *port;
113 struct net_bridge_port_group __rcu *next;
114 struct hlist_node mglist;
116 struct timer_list timer;
121 struct net_bridge_mdb_entry
123 struct hlist_node hlist[2];
124 struct net_bridge *br;
125 struct net_bridge_port_group __rcu *ports;
127 struct timer_list timer;
132 struct net_bridge_mdb_htable
134 struct hlist_head *mhash;
136 struct net_bridge_mdb_htable *old;
143 struct net_bridge_port
145 struct net_bridge *br;
146 struct net_device *dev;
147 struct list_head list;
153 unsigned char topology_change_ack;
154 unsigned char config_pending;
156 port_id designated_port;
157 bridge_id designated_root;
158 bridge_id designated_bridge;
161 unsigned long designated_age;
163 struct timer_list forward_delay_timer;
164 struct timer_list hold_timer;
165 struct timer_list message_age_timer;
170 #define BR_HAIRPIN_MODE 0x00000001
171 #define BR_BPDU_GUARD 0x00000002
172 #define BR_ROOT_BLOCK 0x00000004
173 #define BR_MULTICAST_FAST_LEAVE 0x00000008
174 #define BR_ADMIN_COST 0x00000010
175 #define BR_LEARNING 0x00000020
176 #define BR_FLOOD 0x00000040
177 #define BR_AUTO_MASK (BR_FLOOD | BR_LEARNING)
178 #define BR_PROMISC 0x00000080
180 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
181 struct bridge_mcast_query ip4_query;
182 #if IS_ENABLED(CONFIG_IPV6)
183 struct bridge_mcast_query ip6_query;
184 #endif /* IS_ENABLED(CONFIG_IPV6) */
185 unsigned char multicast_router;
186 struct timer_list multicast_router_timer;
187 struct hlist_head mglist;
188 struct hlist_node rlist;
192 char sysfs_name[IFNAMSIZ];
195 #ifdef CONFIG_NET_POLL_CONTROLLER
198 #ifdef CONFIG_BRIDGE_VLAN_FILTERING
199 struct net_port_vlans __rcu *vlan_info;
203 #define br_auto_port(p) ((p)->flags & BR_AUTO_MASK)
204 #define br_promisc_port(p) ((p)->flags & BR_PROMISC)
206 #define br_port_exists(dev) (dev->priv_flags & IFF_BRIDGE_PORT)
208 static inline struct net_bridge_port *br_port_get_rcu(const struct net_device *dev)
210 return rcu_dereference(dev->rx_handler_data);
213 static inline struct net_bridge_port *br_port_get_rtnl(const struct net_device *dev)
215 return br_port_exists(dev) ?
216 rtnl_dereference(dev->rx_handler_data) : NULL;
222 struct list_head port_list;
223 struct net_device *dev;
225 struct pcpu_sw_netstats __percpu *stats;
226 spinlock_t hash_lock;
227 struct hlist_head hash[BR_HASH_SIZE];
228 #ifdef CONFIG_BRIDGE_NETFILTER
229 struct rtable fake_rtable;
230 bool nf_call_iptables;
231 bool nf_call_ip6tables;
232 bool nf_call_arptables;
237 bridge_id designated_root;
240 unsigned long max_age;
241 unsigned long hello_time;
242 unsigned long forward_delay;
243 unsigned long bridge_max_age;
244 unsigned long ageing_time;
245 unsigned long bridge_hello_time;
246 unsigned long bridge_forward_delay;
248 u8 group_addr[ETH_ALEN];
252 BR_NO_STP, /* no spanning tree */
253 BR_KERNEL_STP, /* old STP in kernel */
254 BR_USER_STP, /* new RSTP in userspace */
257 unsigned char topology_change;
258 unsigned char topology_change_detected;
260 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
261 unsigned char multicast_router;
263 u8 multicast_disabled:1;
264 u8 multicast_querier:1;
265 u8 multicast_query_use_ifaddr:1;
270 u32 multicast_last_member_count;
271 u32 multicast_startup_query_count;
273 unsigned long multicast_last_member_interval;
274 unsigned long multicast_membership_interval;
275 unsigned long multicast_querier_interval;
276 unsigned long multicast_query_interval;
277 unsigned long multicast_query_response_interval;
278 unsigned long multicast_startup_query_interval;
280 spinlock_t multicast_lock;
281 struct net_bridge_mdb_htable __rcu *mdb;
282 struct hlist_head router_list;
284 struct timer_list multicast_router_timer;
285 struct bridge_mcast_querier ip4_querier;
286 struct bridge_mcast_query ip4_query;
287 #if IS_ENABLED(CONFIG_IPV6)
288 struct bridge_mcast_querier ip6_querier;
289 struct bridge_mcast_query ip6_query;
290 #endif /* IS_ENABLED(CONFIG_IPV6) */
293 struct timer_list hello_timer;
294 struct timer_list tcn_timer;
295 struct timer_list topology_change_timer;
296 struct timer_list gc_timer;
297 struct kobject *ifobj;
299 #ifdef CONFIG_BRIDGE_VLAN_FILTERING
301 struct net_port_vlans __rcu *vlan_info;
305 struct br_input_skb_cb {
306 struct net_device *brdev;
307 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
313 #define BR_INPUT_SKB_CB(__skb) ((struct br_input_skb_cb *)(__skb)->cb)
315 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
316 # define BR_INPUT_SKB_CB_MROUTERS_ONLY(__skb) (BR_INPUT_SKB_CB(__skb)->mrouters_only)
318 # define BR_INPUT_SKB_CB_MROUTERS_ONLY(__skb) (0)
321 #define br_printk(level, br, format, args...) \
322 printk(level "%s: " format, (br)->dev->name, ##args)
324 #define br_err(__br, format, args...) \
325 br_printk(KERN_ERR, __br, format, ##args)
326 #define br_warn(__br, format, args...) \
327 br_printk(KERN_WARNING, __br, format, ##args)
328 #define br_notice(__br, format, args...) \
329 br_printk(KERN_NOTICE, __br, format, ##args)
330 #define br_info(__br, format, args...) \
331 br_printk(KERN_INFO, __br, format, ##args)
333 #define br_debug(br, format, args...) \
334 pr_debug("%s: " format, (br)->dev->name, ##args)
336 extern struct notifier_block br_device_notifier;
338 /* called under bridge lock */
339 static inline int br_is_root_bridge(const struct net_bridge *br)
341 return !memcmp(&br->bridge_id, &br->designated_root, 8);
345 void br_dev_setup(struct net_device *dev);
346 void br_dev_delete(struct net_device *dev, struct list_head *list);
347 netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev);
348 #ifdef CONFIG_NET_POLL_CONTROLLER
349 static inline void br_netpoll_send_skb(const struct net_bridge_port *p,
352 struct netpoll *np = p->np;
355 netpoll_send_skb(np, skb);
358 int br_netpoll_enable(struct net_bridge_port *p);
359 void br_netpoll_disable(struct net_bridge_port *p);
361 static inline void br_netpoll_send_skb(const struct net_bridge_port *p,
366 static inline int br_netpoll_enable(struct net_bridge_port *p)
371 static inline void br_netpoll_disable(struct net_bridge_port *p)
377 int br_fdb_init(void);
378 void br_fdb_fini(void);
379 void br_fdb_flush(struct net_bridge *br);
380 void br_fdb_find_delete_local(struct net_bridge *br,
381 const struct net_bridge_port *p,
382 const unsigned char *addr, u16 vid);
383 void br_fdb_changeaddr(struct net_bridge_port *p, const unsigned char *newaddr);
384 void br_fdb_change_mac_address(struct net_bridge *br, const u8 *newaddr);
385 void br_fdb_cleanup(unsigned long arg);
386 void br_fdb_delete_by_port(struct net_bridge *br,
387 const struct net_bridge_port *p, int do_all);
388 struct net_bridge_fdb_entry *__br_fdb_get(struct net_bridge *br,
389 const unsigned char *addr, __u16 vid);
390 int br_fdb_test_addr(struct net_device *dev, unsigned char *addr);
391 int br_fdb_fillbuf(struct net_bridge *br, void *buf, unsigned long count,
393 int br_fdb_insert(struct net_bridge *br, struct net_bridge_port *source,
394 const unsigned char *addr, u16 vid);
395 void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source,
396 const unsigned char *addr, u16 vid, bool added_by_user);
398 int br_fdb_delete(struct ndmsg *ndm, struct nlattr *tb[],
399 struct net_device *dev, const unsigned char *addr);
400 int br_fdb_add(struct ndmsg *nlh, struct nlattr *tb[], struct net_device *dev,
401 const unsigned char *addr, u16 nlh_flags);
402 int br_fdb_dump(struct sk_buff *skb, struct netlink_callback *cb,
403 struct net_device *dev, int idx);
404 int br_fdb_sync_static(struct net_bridge *br, struct net_bridge_port *p);
405 void br_fdb_unsync_static(struct net_bridge *br, struct net_bridge_port *p);
408 void br_deliver(const struct net_bridge_port *to, struct sk_buff *skb);
409 int br_dev_queue_push_xmit(struct sk_buff *skb);
410 void br_forward(const struct net_bridge_port *to,
411 struct sk_buff *skb, struct sk_buff *skb0);
412 int br_forward_finish(struct sk_buff *skb);
413 void br_flood_deliver(struct net_bridge *br, struct sk_buff *skb, bool unicast);
414 void br_flood_forward(struct net_bridge *br, struct sk_buff *skb,
415 struct sk_buff *skb2, bool unicast);
418 void br_port_carrier_check(struct net_bridge_port *p);
419 int br_add_bridge(struct net *net, const char *name);
420 int br_del_bridge(struct net *net, const char *name);
421 int br_add_if(struct net_bridge *br, struct net_device *dev);
422 int br_del_if(struct net_bridge *br, struct net_device *dev);
423 int br_min_mtu(const struct net_bridge *br);
424 netdev_features_t br_features_recompute(struct net_bridge *br,
425 netdev_features_t features);
426 void br_port_flags_change(struct net_bridge_port *port, unsigned long mask);
427 void br_manage_promisc(struct net_bridge *br);
430 int br_handle_frame_finish(struct sk_buff *skb);
431 rx_handler_result_t br_handle_frame(struct sk_buff **pskb);
433 static inline bool br_rx_handler_check_rcu(const struct net_device *dev)
435 return rcu_dereference(dev->rx_handler) == br_handle_frame;
438 static inline struct net_bridge_port *br_port_get_check_rcu(const struct net_device *dev)
440 return br_rx_handler_check_rcu(dev) ? br_port_get_rcu(dev) : NULL;
444 int br_dev_ioctl(struct net_device *dev, struct ifreq *rq, int cmd);
445 int br_ioctl_deviceless_stub(struct net *net, unsigned int cmd,
449 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
450 extern unsigned int br_mdb_rehash_seq;
451 int br_multicast_rcv(struct net_bridge *br, struct net_bridge_port *port,
452 struct sk_buff *skb, u16 vid);
453 struct net_bridge_mdb_entry *br_mdb_get(struct net_bridge *br,
454 struct sk_buff *skb, u16 vid);
455 void br_multicast_add_port(struct net_bridge_port *port);
456 void br_multicast_del_port(struct net_bridge_port *port);
457 void br_multicast_enable_port(struct net_bridge_port *port);
458 void br_multicast_disable_port(struct net_bridge_port *port);
459 void br_multicast_init(struct net_bridge *br);
460 void br_multicast_open(struct net_bridge *br);
461 void br_multicast_stop(struct net_bridge *br);
462 void br_multicast_deliver(struct net_bridge_mdb_entry *mdst,
463 struct sk_buff *skb);
464 void br_multicast_forward(struct net_bridge_mdb_entry *mdst,
465 struct sk_buff *skb, struct sk_buff *skb2);
466 int br_multicast_set_router(struct net_bridge *br, unsigned long val);
467 int br_multicast_set_port_router(struct net_bridge_port *p, unsigned long val);
468 int br_multicast_toggle(struct net_bridge *br, unsigned long val);
469 int br_multicast_set_querier(struct net_bridge *br, unsigned long val);
470 int br_multicast_set_hash_max(struct net_bridge *br, unsigned long val);
471 struct net_bridge_mdb_entry *
472 br_mdb_ip_get(struct net_bridge_mdb_htable *mdb, struct br_ip *dst);
473 struct net_bridge_mdb_entry *
474 br_multicast_new_group(struct net_bridge *br, struct net_bridge_port *port,
475 struct br_ip *group);
476 void br_multicast_free_pg(struct rcu_head *head);
477 struct net_bridge_port_group *
478 br_multicast_new_port_group(struct net_bridge_port *port, struct br_ip *group,
479 struct net_bridge_port_group __rcu *next,
480 unsigned char state);
481 void br_mdb_init(void);
482 void br_mdb_uninit(void);
483 void br_mdb_notify(struct net_device *dev, struct net_bridge_port *port,
484 struct br_ip *group, int type);
486 #define mlock_dereference(X, br) \
487 rcu_dereference_protected(X, lockdep_is_held(&br->multicast_lock))
489 static inline bool br_multicast_is_router(struct net_bridge *br)
491 return br->multicast_router == 2 ||
492 (br->multicast_router == 1 &&
493 timer_pending(&br->multicast_router_timer));
497 __br_multicast_querier_exists(struct net_bridge *br,
498 struct bridge_mcast_querier *querier)
500 return time_is_before_jiffies(querier->delay_time) &&
501 (br->multicast_querier || timer_pending(&querier->timer));
504 static inline bool br_multicast_querier_exists(struct net_bridge *br,
507 switch (eth->h_proto) {
508 case (htons(ETH_P_IP)):
509 return __br_multicast_querier_exists(br, &br->ip4_querier);
510 #if IS_ENABLED(CONFIG_IPV6)
511 case (htons(ETH_P_IPV6)):
512 return __br_multicast_querier_exists(br, &br->ip6_querier);
519 static inline int br_multicast_rcv(struct net_bridge *br,
520 struct net_bridge_port *port,
527 static inline struct net_bridge_mdb_entry *br_mdb_get(struct net_bridge *br,
528 struct sk_buff *skb, u16 vid)
533 static inline void br_multicast_add_port(struct net_bridge_port *port)
537 static inline void br_multicast_del_port(struct net_bridge_port *port)
541 static inline void br_multicast_enable_port(struct net_bridge_port *port)
545 static inline void br_multicast_disable_port(struct net_bridge_port *port)
549 static inline void br_multicast_init(struct net_bridge *br)
553 static inline void br_multicast_open(struct net_bridge *br)
557 static inline void br_multicast_stop(struct net_bridge *br)
561 static inline void br_multicast_deliver(struct net_bridge_mdb_entry *mdst,
566 static inline void br_multicast_forward(struct net_bridge_mdb_entry *mdst,
568 struct sk_buff *skb2)
571 static inline bool br_multicast_is_router(struct net_bridge *br)
575 static inline bool br_multicast_querier_exists(struct net_bridge *br,
580 static inline void br_mdb_init(void)
583 static inline void br_mdb_uninit(void)
589 #ifdef CONFIG_BRIDGE_VLAN_FILTERING
590 bool br_allowed_ingress(struct net_bridge *br, struct net_port_vlans *v,
591 struct sk_buff *skb, u16 *vid);
592 bool br_allowed_egress(struct net_bridge *br, const struct net_port_vlans *v,
593 const struct sk_buff *skb);
594 struct sk_buff *br_handle_vlan(struct net_bridge *br,
595 const struct net_port_vlans *v,
596 struct sk_buff *skb);
597 int br_vlan_add(struct net_bridge *br, u16 vid, u16 flags);
598 int br_vlan_delete(struct net_bridge *br, u16 vid);
599 void br_vlan_flush(struct net_bridge *br);
600 bool br_vlan_find(struct net_bridge *br, u16 vid);
601 int br_vlan_filter_toggle(struct net_bridge *br, unsigned long val);
602 int nbp_vlan_add(struct net_bridge_port *port, u16 vid, u16 flags);
603 int nbp_vlan_delete(struct net_bridge_port *port, u16 vid);
604 void nbp_vlan_flush(struct net_bridge_port *port);
605 bool nbp_vlan_find(struct net_bridge_port *port, u16 vid);
607 static inline struct net_port_vlans *br_get_vlan_info(
608 const struct net_bridge *br)
610 return rcu_dereference_rtnl(br->vlan_info);
613 static inline struct net_port_vlans *nbp_get_vlan_info(
614 const struct net_bridge_port *p)
616 return rcu_dereference_rtnl(p->vlan_info);
619 /* Since bridge now depends on 8021Q module, but the time bridge sees the
620 * skb, the vlan tag will always be present if the frame was tagged.
622 static inline int br_vlan_get_tag(const struct sk_buff *skb, u16 *vid)
626 if (vlan_tx_tag_present(skb))
627 *vid = vlan_tx_tag_get(skb) & VLAN_VID_MASK;
636 static inline u16 br_get_pvid(const struct net_port_vlans *v)
638 /* Return just the VID if it is set, or VLAN_N_VID (invalid vid) if
642 return v->pvid ?: VLAN_N_VID;
645 static inline int br_vlan_enabled(struct net_bridge *br)
647 return br->vlan_enabled;
650 static inline bool br_allowed_ingress(struct net_bridge *br,
651 struct net_port_vlans *v,
658 static inline bool br_allowed_egress(struct net_bridge *br,
659 const struct net_port_vlans *v,
660 const struct sk_buff *skb)
665 static inline struct sk_buff *br_handle_vlan(struct net_bridge *br,
666 const struct net_port_vlans *v,
672 static inline int br_vlan_add(struct net_bridge *br, u16 vid, u16 flags)
677 static inline int br_vlan_delete(struct net_bridge *br, u16 vid)
682 static inline void br_vlan_flush(struct net_bridge *br)
686 static inline bool br_vlan_find(struct net_bridge *br, u16 vid)
691 static inline int nbp_vlan_add(struct net_bridge_port *port, u16 vid, u16 flags)
696 static inline int nbp_vlan_delete(struct net_bridge_port *port, u16 vid)
701 static inline void nbp_vlan_flush(struct net_bridge_port *port)
705 static inline struct net_port_vlans *br_get_vlan_info(
706 const struct net_bridge *br)
710 static inline struct net_port_vlans *nbp_get_vlan_info(
711 const struct net_bridge_port *p)
716 static inline bool nbp_vlan_find(struct net_bridge_port *port, u16 vid)
721 static inline u16 br_vlan_get_tag(const struct sk_buff *skb, u16 *tag)
725 static inline u16 br_get_pvid(const struct net_port_vlans *v)
727 return VLAN_N_VID; /* Returns invalid vid */
730 static inline int br_vlan_enabled(struct net_bridge *br);
737 #ifdef CONFIG_BRIDGE_NETFILTER
738 int br_netfilter_init(void);
739 void br_netfilter_fini(void);
740 void br_netfilter_rtable_init(struct net_bridge *);
742 #define br_netfilter_init() (0)
743 #define br_netfilter_fini() do { } while (0)
744 #define br_netfilter_rtable_init(x)
748 void br_log_state(const struct net_bridge_port *p);
749 struct net_bridge_port *br_get_port(struct net_bridge *br, u16 port_no);
750 void br_init_port(struct net_bridge_port *p);
751 void br_become_designated_port(struct net_bridge_port *p);
753 void __br_set_forward_delay(struct net_bridge *br, unsigned long t);
754 int br_set_forward_delay(struct net_bridge *br, unsigned long x);
755 int br_set_hello_time(struct net_bridge *br, unsigned long x);
756 int br_set_max_age(struct net_bridge *br, unsigned long x);
760 void br_stp_enable_bridge(struct net_bridge *br);
761 void br_stp_disable_bridge(struct net_bridge *br);
762 void br_stp_set_enabled(struct net_bridge *br, unsigned long val);
763 void br_stp_enable_port(struct net_bridge_port *p);
764 void br_stp_disable_port(struct net_bridge_port *p);
765 bool br_stp_recalculate_bridge_id(struct net_bridge *br);
766 void br_stp_change_bridge_id(struct net_bridge *br, const unsigned char *a);
767 void br_stp_set_bridge_priority(struct net_bridge *br, u16 newprio);
768 int br_stp_set_port_priority(struct net_bridge_port *p, unsigned long newprio);
769 int br_stp_set_path_cost(struct net_bridge_port *p, unsigned long path_cost);
770 ssize_t br_show_bridge_id(char *buf, const struct bridge_id *id);
774 void br_stp_rcv(const struct stp_proto *proto, struct sk_buff *skb,
775 struct net_device *dev);
778 void br_stp_timer_init(struct net_bridge *br);
779 void br_stp_port_timer_init(struct net_bridge_port *p);
780 unsigned long br_timer_value(const struct timer_list *timer);
783 #if IS_ENABLED(CONFIG_ATM_LANE)
784 extern int (*br_fdb_test_addr_hook)(struct net_device *dev, unsigned char *addr);
788 extern struct rtnl_link_ops br_link_ops;
789 int br_netlink_init(void);
790 void br_netlink_fini(void);
791 void br_ifinfo_notify(int event, struct net_bridge_port *port);
792 int br_setlink(struct net_device *dev, struct nlmsghdr *nlmsg);
793 int br_dellink(struct net_device *dev, struct nlmsghdr *nlmsg);
794 int br_getlink(struct sk_buff *skb, u32 pid, u32 seq, struct net_device *dev,
799 extern const struct sysfs_ops brport_sysfs_ops;
800 int br_sysfs_addif(struct net_bridge_port *p);
801 int br_sysfs_renameif(struct net_bridge_port *p);
804 int br_sysfs_addbr(struct net_device *dev);
805 void br_sysfs_delbr(struct net_device *dev);
809 static inline int br_sysfs_addif(struct net_bridge_port *p) { return 0; }
810 static inline int br_sysfs_renameif(struct net_bridge_port *p) { return 0; }
811 static inline int br_sysfs_addbr(struct net_device *dev) { return 0; }
812 static inline void br_sysfs_delbr(struct net_device *dev) { return; }
813 #endif /* CONFIG_SYSFS */