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linux-stable/include/net/neighbour.h
Gustavo A. R. Silva 08ca27d027 neighbour: Replace zero-length array with flexible-array member 
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2020-02-29 21:52:20 -08:00

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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _NET_NEIGHBOUR_H
#define _NET_NEIGHBOUR_H
#include <linux/neighbour.h>
/*
* Generic neighbour manipulation
*
* Authors:
* Pedro Roque <roque@di.fc.ul.pt>
* Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
*
* Changes:
*
* Harald Welte: <laforge@gnumonks.org>
* - Add neighbour cache statistics like rtstat
*/
#include <linux/atomic.h>
#include <linux/refcount.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/rcupdate.h>
#include <linux/seq_file.h>
#include <linux/bitmap.h>
#include <linux/err.h>
#include <linux/sysctl.h>
#include <linux/workqueue.h>
#include <net/rtnetlink.h>
/*
* NUD stands for "neighbor unreachability detection"
*/
#define NUD_IN_TIMER (NUD_INCOMPLETE|NUD_REACHABLE|NUD_DELAY|NUD_PROBE)
#define NUD_VALID (NUD_PERMANENT|NUD_NOARP|NUD_REACHABLE|NUD_PROBE|NUD_STALE|NUD_DELAY)
#define NUD_CONNECTED (NUD_PERMANENT|NUD_NOARP|NUD_REACHABLE)
struct neighbour;
enum {
NEIGH_VAR_MCAST_PROBES,
NEIGH_VAR_UCAST_PROBES,
NEIGH_VAR_APP_PROBES,
NEIGH_VAR_MCAST_REPROBES,
NEIGH_VAR_RETRANS_TIME,
NEIGH_VAR_BASE_REACHABLE_TIME,
NEIGH_VAR_DELAY_PROBE_TIME,
NEIGH_VAR_GC_STALETIME,
NEIGH_VAR_QUEUE_LEN_BYTES,
NEIGH_VAR_PROXY_QLEN,
NEIGH_VAR_ANYCAST_DELAY,
NEIGH_VAR_PROXY_DELAY,
NEIGH_VAR_LOCKTIME,
#define NEIGH_VAR_DATA_MAX (NEIGH_VAR_LOCKTIME + 1)
/* Following are used as a second way to access one of the above */
NEIGH_VAR_QUEUE_LEN, /* same data as NEIGH_VAR_QUEUE_LEN_BYTES */
NEIGH_VAR_RETRANS_TIME_MS, /* same data as NEIGH_VAR_RETRANS_TIME */
NEIGH_VAR_BASE_REACHABLE_TIME_MS, /* same data as NEIGH_VAR_BASE_REACHABLE_TIME */
/* Following are used by "default" only */
NEIGH_VAR_GC_INTERVAL,
NEIGH_VAR_GC_THRESH1,
NEIGH_VAR_GC_THRESH2,
NEIGH_VAR_GC_THRESH3,
NEIGH_VAR_MAX
};
struct neigh_parms {
possible_net_t net;
struct net_device *dev;
struct list_head list;
int (*neigh_setup)(struct neighbour *);
struct neigh_table *tbl;
void *sysctl_table;
int dead;
refcount_t refcnt;
struct rcu_head rcu_head;
int reachable_time;
int data[NEIGH_VAR_DATA_MAX];
DECLARE_BITMAP(data_state, NEIGH_VAR_DATA_MAX);
};
static inline void neigh_var_set(struct neigh_parms *p, int index, int val)
{
set_bit(index, p->data_state);
p->data[index] = val;
}
#define NEIGH_VAR(p, attr) ((p)->data[NEIGH_VAR_ ## attr])
/* In ndo_neigh_setup, NEIGH_VAR_INIT should be used.
* In other cases, NEIGH_VAR_SET should be used.
*/
#define NEIGH_VAR_INIT(p, attr, val) (NEIGH_VAR(p, attr) = val)
#define NEIGH_VAR_SET(p, attr, val) neigh_var_set(p, NEIGH_VAR_ ## attr, val)
static inline void neigh_parms_data_state_setall(struct neigh_parms *p)
{
bitmap_fill(p->data_state, NEIGH_VAR_DATA_MAX);
}
static inline void neigh_parms_data_state_cleanall(struct neigh_parms *p)
{
bitmap_zero(p->data_state, NEIGH_VAR_DATA_MAX);
}
struct neigh_statistics {
unsigned long allocs; /* number of allocated neighs */
unsigned long destroys; /* number of destroyed neighs */
unsigned long hash_grows; /* number of hash resizes */
unsigned long res_failed; /* number of failed resolutions */
unsigned long lookups; /* number of lookups */
unsigned long hits; /* number of hits (among lookups) */
unsigned long rcv_probes_mcast; /* number of received mcast ipv6 */
unsigned long rcv_probes_ucast; /* number of received ucast ipv6 */
unsigned long periodic_gc_runs; /* number of periodic GC runs */
unsigned long forced_gc_runs; /* number of forced GC runs */
unsigned long unres_discards; /* number of unresolved drops */
unsigned long table_fulls; /* times even gc couldn't help */
};
#define NEIGH_CACHE_STAT_INC(tbl, field) this_cpu_inc((tbl)->stats->field)
struct neighbour {
struct neighbour __rcu *next;
struct neigh_table *tbl;
struct neigh_parms *parms;
unsigned long confirmed;
unsigned long updated;
rwlock_t lock;
refcount_t refcnt;
unsigned int arp_queue_len_bytes;
struct sk_buff_head arp_queue;
struct timer_list timer;
unsigned long used;
atomic_t probes;
__u8 flags;
__u8 nud_state;
__u8 type;
__u8 dead;
u8 protocol;
seqlock_t ha_lock;
unsigned char ha[ALIGN(MAX_ADDR_LEN, sizeof(unsigned long))] __aligned(8);
struct hh_cache hh;
int (*output)(struct neighbour *, struct sk_buff *);
const struct neigh_ops *ops;
struct list_head gc_list;
struct rcu_head rcu;
struct net_device *dev;
u8 primary_key[0];
} __randomize_layout;
struct neigh_ops {
int family;
void (*solicit)(struct neighbour *, struct sk_buff *);
void (*error_report)(struct neighbour *, struct sk_buff *);
int (*output)(struct neighbour *, struct sk_buff *);
int (*connected_output)(struct neighbour *, struct sk_buff *);
};
struct pneigh_entry {
struct pneigh_entry *next;
possible_net_t net;
struct net_device *dev;
u8 flags;
u8 protocol;
u8 key[];
};
/*
* neighbour table manipulation
*/
#define NEIGH_NUM_HASH_RND 4
struct neigh_hash_table {
struct neighbour __rcu **hash_buckets;
unsigned int hash_shift;
__u32 hash_rnd[NEIGH_NUM_HASH_RND];
struct rcu_head rcu;
};
struct neigh_table {
int family;
unsigned int entry_size;
unsigned int key_len;
__be16 protocol;
__u32 (*hash)(const void *pkey,
const struct net_device *dev,
__u32 *hash_rnd);
bool (*key_eq)(const struct neighbour *, const void *pkey);
int (*constructor)(struct neighbour *);
int (*pconstructor)(struct pneigh_entry *);
void (*pdestructor)(struct pneigh_entry *);
void (*proxy_redo)(struct sk_buff *skb);
bool (*allow_add)(const struct net_device *dev,
struct netlink_ext_ack *extack);
char *id;
struct neigh_parms parms;
struct list_head parms_list;
int gc_interval;
int gc_thresh1;
int gc_thresh2;
int gc_thresh3;
unsigned long last_flush;
struct delayed_work gc_work;
struct timer_list proxy_timer;
struct sk_buff_head proxy_queue;
atomic_t entries;
atomic_t gc_entries;
struct list_head gc_list;
rwlock_t lock;
unsigned long last_rand;
struct neigh_statistics __percpu *stats;
struct neigh_hash_table __rcu *nht;
struct pneigh_entry **phash_buckets;
};
enum {
NEIGH_ARP_TABLE = 0,
NEIGH_ND_TABLE = 1,
NEIGH_DN_TABLE = 2,
NEIGH_NR_TABLES,
NEIGH_LINK_TABLE = NEIGH_NR_TABLES /* Pseudo table for neigh_xmit */
};
static inline int neigh_parms_family(struct neigh_parms *p)
{
return p->tbl->family;
}
#define NEIGH_PRIV_ALIGN sizeof(long long)
#define NEIGH_ENTRY_SIZE(size) ALIGN((size), NEIGH_PRIV_ALIGN)
static inline void *neighbour_priv(const struct neighbour *n)
{
return (char *)n + n->tbl->entry_size;
}
/* flags for neigh_update() */
#define NEIGH_UPDATE_F_OVERRIDE 0x00000001
#define NEIGH_UPDATE_F_WEAK_OVERRIDE 0x00000002
#define NEIGH_UPDATE_F_OVERRIDE_ISROUTER 0x00000004
#define NEIGH_UPDATE_F_EXT_LEARNED 0x20000000
#define NEIGH_UPDATE_F_ISROUTER 0x40000000
#define NEIGH_UPDATE_F_ADMIN 0x80000000
extern const struct nla_policy nda_policy[];
static inline bool neigh_key_eq16(const struct neighbour *n, const void *pkey)
{
return *(const u16 *)n->primary_key == *(const u16 *)pkey;
}
static inline bool neigh_key_eq32(const struct neighbour *n, const void *pkey)
{
return *(const u32 *)n->primary_key == *(const u32 *)pkey;
}
static inline bool neigh_key_eq128(const struct neighbour *n, const void *pkey)
{
const u32 *n32 = (const u32 *)n->primary_key;
const u32 *p32 = pkey;
return ((n32[0] ^ p32[0]) | (n32[1] ^ p32[1]) |
(n32[2] ^ p32[2]) | (n32[3] ^ p32[3])) == 0;
}
static inline struct neighbour *___neigh_lookup_noref(
struct neigh_table *tbl,
bool (*key_eq)(const struct neighbour *n, const void *pkey),
__u32 (*hash)(const void *pkey,
const struct net_device *dev,
__u32 *hash_rnd),
const void *pkey,
struct net_device *dev)
{
struct neigh_hash_table *nht = rcu_dereference_bh(tbl->nht);
struct neighbour *n;
u32 hash_val;
hash_val = hash(pkey, dev, nht->hash_rnd) >> (32 - nht->hash_shift);
for (n = rcu_dereference_bh(nht->hash_buckets[hash_val]);
n != NULL;
n = rcu_dereference_bh(n->next)) {
if (n->dev == dev && key_eq(n, pkey))
return n;
}
return NULL;
}
static inline struct neighbour *__neigh_lookup_noref(struct neigh_table *tbl,
const void *pkey,
struct net_device *dev)
{
return ___neigh_lookup_noref(tbl, tbl->key_eq, tbl->hash, pkey, dev);
}
void neigh_table_init(int index, struct neigh_table *tbl);
int neigh_table_clear(int index, struct neigh_table *tbl);
struct neighbour *neigh_lookup(struct neigh_table *tbl, const void *pkey,
struct net_device *dev);
struct neighbour *neigh_lookup_nodev(struct neigh_table *tbl, struct net *net,
const void *pkey);
struct neighbour *__neigh_create(struct neigh_table *tbl, const void *pkey,
struct net_device *dev, bool want_ref);
static inline struct neighbour *neigh_create(struct neigh_table *tbl,
const void *pkey,
struct net_device *dev)
{
return __neigh_create(tbl, pkey, dev, true);
}
void neigh_destroy(struct neighbour *neigh);
int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb);
int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new, u32 flags,
u32 nlmsg_pid);
void __neigh_set_probe_once(struct neighbour *neigh);
bool neigh_remove_one(struct neighbour *ndel, struct neigh_table *tbl);
void neigh_changeaddr(struct neigh_table *tbl, struct net_device *dev);
int neigh_ifdown(struct neigh_table *tbl, struct net_device *dev);
int neigh_carrier_down(struct neigh_table *tbl, struct net_device *dev);
int neigh_resolve_output(struct neighbour *neigh, struct sk_buff *skb);
int neigh_connected_output(struct neighbour *neigh, struct sk_buff *skb);
int neigh_direct_output(struct neighbour *neigh, struct sk_buff *skb);
struct neighbour *neigh_event_ns(struct neigh_table *tbl,
u8 *lladdr, void *saddr,
struct net_device *dev);
struct neigh_parms *neigh_parms_alloc(struct net_device *dev,
struct neigh_table *tbl);
void neigh_parms_release(struct neigh_table *tbl, struct neigh_parms *parms);
static inline
struct net *neigh_parms_net(const struct neigh_parms *parms)
{
return read_pnet(&parms->net);
}
unsigned long neigh_rand_reach_time(unsigned long base);
void pneigh_enqueue(struct neigh_table *tbl, struct neigh_parms *p,
struct sk_buff *skb);
struct pneigh_entry *pneigh_lookup(struct neigh_table *tbl, struct net *net,
const void *key, struct net_device *dev,
int creat);
struct pneigh_entry *__pneigh_lookup(struct neigh_table *tbl, struct net *net,
const void *key, struct net_device *dev);
int pneigh_delete(struct neigh_table *tbl, struct net *net, const void *key,
struct net_device *dev);
static inline struct net *pneigh_net(const struct pneigh_entry *pneigh)
{
return read_pnet(&pneigh->net);
}
void neigh_app_ns(struct neighbour *n);
void neigh_for_each(struct neigh_table *tbl,
void (*cb)(struct neighbour *, void *), void *cookie);
void __neigh_for_each_release(struct neigh_table *tbl,
int (*cb)(struct neighbour *));
int neigh_xmit(int fam, struct net_device *, const void *, struct sk_buff *);
void pneigh_for_each(struct neigh_table *tbl,
void (*cb)(struct pneigh_entry *));
struct neigh_seq_state {
struct seq_net_private p;
struct neigh_table *tbl;
struct neigh_hash_table *nht;
void *(*neigh_sub_iter)(struct neigh_seq_state *state,
struct neighbour *n, loff_t *pos);
unsigned int bucket;
unsigned int flags;
#define NEIGH_SEQ_NEIGH_ONLY 0x00000001
#define NEIGH_SEQ_IS_PNEIGH 0x00000002
#define NEIGH_SEQ_SKIP_NOARP 0x00000004
};
void *neigh_seq_start(struct seq_file *, loff_t *, struct neigh_table *,
unsigned int);
void *neigh_seq_next(struct seq_file *, void *, loff_t *);
void neigh_seq_stop(struct seq_file *, void *);
int neigh_proc_dointvec(struct ctl_table *ctl, int write,
void __user *buffer, size_t *lenp, loff_t *ppos);
int neigh_proc_dointvec_jiffies(struct ctl_table *ctl, int write,
void __user *buffer,
size_t *lenp, loff_t *ppos);
int neigh_proc_dointvec_ms_jiffies(struct ctl_table *ctl, int write,
void __user *buffer,
size_t *lenp, loff_t *ppos);
int neigh_sysctl_register(struct net_device *dev, struct neigh_parms *p,
proc_handler *proc_handler);
void neigh_sysctl_unregister(struct neigh_parms *p);
static inline void __neigh_parms_put(struct neigh_parms *parms)
{
refcount_dec(&parms->refcnt);
}
static inline struct neigh_parms *neigh_parms_clone(struct neigh_parms *parms)
{
refcount_inc(&parms->refcnt);
return parms;
}
/*
* Neighbour references
*/
static inline void neigh_release(struct neighbour *neigh)
{
if (refcount_dec_and_test(&neigh->refcnt))
neigh_destroy(neigh);
}
static inline struct neighbour * neigh_clone(struct neighbour *neigh)
{
if (neigh)
refcount_inc(&neigh->refcnt);
return neigh;
}
#define neigh_hold(n) refcount_inc(&(n)->refcnt)
static inline int neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
{
unsigned long now = jiffies;
if (READ_ONCE(neigh->used) != now)
WRITE_ONCE(neigh->used, now);
if (!(neigh->nud_state&(NUD_CONNECTED|NUD_DELAY|NUD_PROBE)))
return __neigh_event_send(neigh, skb);
return 0;
}
#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
static inline int neigh_hh_bridge(struct hh_cache *hh, struct sk_buff *skb)
{
unsigned int seq, hh_alen;
do {
seq = read_seqbegin(&hh->hh_lock);
hh_alen = HH_DATA_ALIGN(ETH_HLEN);
memcpy(skb->data - hh_alen, hh->hh_data, ETH_ALEN + hh_alen - ETH_HLEN);
} while (read_seqretry(&hh->hh_lock, seq));
return 0;
}
#endif
static inline int neigh_hh_output(const struct hh_cache *hh, struct sk_buff *skb)
{
unsigned int hh_alen = 0;
unsigned int seq;
unsigned int hh_len;
do {
seq = read_seqbegin(&hh->hh_lock);
hh_len = READ_ONCE(hh->hh_len);
if (likely(hh_len <= HH_DATA_MOD)) {
hh_alen = HH_DATA_MOD;
/* skb_push() would proceed silently if we have room for
* the unaligned size but not for the aligned size:
* check headroom explicitly.
*/
if (likely(skb_headroom(skb) >= HH_DATA_MOD)) {
/* this is inlined by gcc */
memcpy(skb->data - HH_DATA_MOD, hh->hh_data,
HH_DATA_MOD);
}
} else {
hh_alen = HH_DATA_ALIGN(hh_len);
if (likely(skb_headroom(skb) >= hh_alen)) {
memcpy(skb->data - hh_alen, hh->hh_data,
hh_alen);
}
}
} while (read_seqretry(&hh->hh_lock, seq));
if (WARN_ON_ONCE(skb_headroom(skb) < hh_alen)) {
kfree_skb(skb);
return NET_XMIT_DROP;
}
__skb_push(skb, hh_len);
return dev_queue_xmit(skb);
}
static inline int neigh_output(struct neighbour *n, struct sk_buff *skb,
bool skip_cache)
{
const struct hh_cache *hh = &n->hh;
if ((n->nud_state & NUD_CONNECTED) && hh->hh_len && !skip_cache)
return neigh_hh_output(hh, skb);
else
return n->output(n, skb);
}
static inline struct neighbour *
__neigh_lookup(struct neigh_table *tbl, const void *pkey, struct net_device *dev, int creat)
{
struct neighbour *n = neigh_lookup(tbl, pkey, dev);
if (n || !creat)
return n;
n = neigh_create(tbl, pkey, dev);
return IS_ERR(n) ? NULL : n;
}
static inline struct neighbour *
__neigh_lookup_errno(struct neigh_table *tbl, const void *pkey,
struct net_device *dev)
{
struct neighbour *n = neigh_lookup(tbl, pkey, dev);
if (n)
return n;
return neigh_create(tbl, pkey, dev);
}
struct neighbour_cb {
unsigned long sched_next;
unsigned int flags;
};
#define LOCALLY_ENQUEUED 0x1
#define NEIGH_CB(skb) ((struct neighbour_cb *)(skb)->cb)
static inline void neigh_ha_snapshot(char *dst, const struct neighbour *n,
const struct net_device *dev)
{
unsigned int seq;
do {
seq = read_seqbegin(&n->ha_lock);
memcpy(dst, n->ha, dev->addr_len);
} while (read_seqretry(&n->ha_lock, seq));
}
static inline void neigh_update_is_router(struct neighbour *neigh, u32 flags,
int *notify)
{
u8 ndm_flags = 0;
ndm_flags |= (flags & NEIGH_UPDATE_F_ISROUTER) ? NTF_ROUTER : 0;
if ((neigh->flags ^ ndm_flags) & NTF_ROUTER) {
if (ndm_flags & NTF_ROUTER)
neigh->flags |= NTF_ROUTER;
else
neigh->flags &= ~NTF_ROUTER;
*notify = 1;
}
}
#endif
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