inet_hashtables.h

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/*
 * INET     An implementation of the TCP/IP protocol suite for the LINUX
 *      operating system.  INET is implemented using the BSD Socket
 *      interface as the means of communication with the user level.
 *
 * Authors: Lotsa people, from code originally in tcp
 *
 *  This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 */

#ifndef _INET_HASHTABLES_H
#define _INET_HASHTABLES_H


#include <linux/interrupt.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/socket.h>
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/wait.h>
#include <linux/vmalloc.h>

#include <net/inet_connection_sock.h>
#include <net/inet_sock.h>
#include <net/sock.h>
#include <net/route.h>
#include <net/tcp_states.h>
#include <net/netns/hash.h>

#include <linux/atomic.h>
#include <asm/byteorder.h>

/* This is for all connections with a full identity, no wildcards.
 * One chain is dedicated to TIME_WAIT sockets.
 * I'll experiment with dynamic table growth later.
 */
struct inet_ehash_bucket {
    struct hlist_nulls_head chain;
    struct hlist_nulls_head twchain;
};

/* There are a few simple rules, which allow for local port reuse by
 * an application.  In essence:
 *
 *  1) Sockets bound to different interfaces may share a local port.
 *     Failing that, goto test 2.
 *  2) If all sockets have sk->sk_reuse set, and none of them are in
 *     TCP_LISTEN state, the port may be shared.
 *     Failing that, goto test 3.
 *  3) If all sockets are bound to a specific inet_sk(sk)->rcv_saddr local
 *     address, and none of them are the same, the port may be
 *     shared.
 *     Failing this, the port cannot be shared.
 *
 * The interesting point, is test #2.  This is what an FTP server does
 * all day.  To optimize this case we use a specific flag bit defined
 * below.  As we add sockets to a bind bucket list, we perform a
 * check of: (newsk->sk_reuse && (newsk->sk_state != TCP_LISTEN))
 * As long as all sockets added to a bind bucket pass this test,
 * the flag bit will be set.
 * The resulting situation is that tcp_v[46]_verify_bind() can just check
 * for this flag bit, if it is set and the socket trying to bind has
 * sk->sk_reuse set, we don't even have to walk the owners list at all,
 * we return that it is ok to bind this socket to the requested local port.
 *
 * Sounds like a lot of work, but it is worth it.  In a more naive
 * implementation (ie. current FreeBSD etc.) the entire list of ports
 * must be walked for each data port opened by an ftp server.  Needless
 * to say, this does not scale at all.  With a couple thousand FTP
 * users logged onto your box, isn't it nice to know that new data
 * ports are created in O(1) time?  I thought so. ;-)   -DaveM
 */
struct inet_bind_bucket {
#ifdef CONFIG_NET_NS
    struct net      *ib_net;
#endif
    unsigned short      port;
    signed short        fastreuse;
    int         num_owners;
    struct hlist_node   node;
    struct hlist_head   owners;
};

static inline struct net *ib_net(struct inet_bind_bucket *ib)
{
    return read_pnet(&ib->ib_net);
}

#define inet_bind_bucket_for_each(tb, pos, head) \
    hlist_for_each_entry(tb, pos, head, node)

struct inet_bind_hashbucket {
    spinlock_t      lock;
    struct hlist_head   chain;
};

/*
 * Sockets can be hashed in established or listening table
 * We must use different 'nulls' end-of-chain value for listening
 * hash table, or we might find a socket that was closed and
 * reallocated/inserted into established hash table
 */
#define LISTENING_NULLS_BASE (1U << 29)
struct inet_listen_hashbucket {
    spinlock_t      lock;
    struct hlist_nulls_head head;
};

/* This is for listening sockets, thus all sockets which possess wildcards. */
#define INET_LHTABLE_SIZE   32  /* Yes, really, this is all you need. */

struct inet_hashinfo {
    /* This is for sockets with full identity only.  Sockets here will
     * always be without wildcards and will have the following invariant:
     *
     *          TCP_ESTABLISHED <= sk->sk_state < TCP_CLOSE
     *
     * TIME_WAIT sockets use a separate chain (twchain).
     */
    struct inet_ehash_bucket    *ehash;
    spinlock_t          *ehash_locks;
    unsigned int            ehash_mask;
    unsigned int            ehash_locks_mask;

    /* Ok, let's try this, I give up, we do need a local binding
     * TCP hash as well as the others for fast bind/connect.
     */
    struct inet_bind_hashbucket *bhash;

    unsigned int            bhash_size;
    /* 4 bytes hole on 64 bit */

    struct kmem_cache       *bind_bucket_cachep;

    /* All the above members are written once at bootup and
     * never written again _or_ are predominantly read-access.
     *
     * Now align to a new cache line as all the following members
     * might be often dirty.
     */
    /* All sockets in TCP_LISTEN state will be in here.  This is the only
     * table where wildcard'd TCP sockets can exist.  Hash function here
     * is just local port number.
     */
    struct inet_listen_hashbucket   listening_hash[INET_LHTABLE_SIZE]
                    ____cacheline_aligned_in_smp;

    atomic_t            bsockets;
};

static inline struct inet_ehash_bucket *inet_ehash_bucket(
    struct inet_hashinfo *hashinfo,
    unsigned int hash)
{
    return &hashinfo->ehash[hash & hashinfo->ehash_mask];
}

static inline spinlock_t *inet_ehash_lockp(
    struct inet_hashinfo *hashinfo,
    unsigned int hash)
{
    return &hashinfo->ehash_locks[hash & hashinfo->ehash_locks_mask];
}

static inline int inet_ehash_locks_alloc(struct inet_hashinfo *hashinfo)
{
    unsigned int i, size = 256;
#if defined(CONFIG_PROVE_LOCKING)
    unsigned int nr_pcpus = 2;
#else
    unsigned int nr_pcpus = num_possible_cpus();
#endif
    if (nr_pcpus >= 4)
        size = 512;
    if (nr_pcpus >= 8)
        size = 1024;
    if (nr_pcpus >= 16)
        size = 2048;
    if (nr_pcpus >= 32)
        size = 4096;
    if (sizeof(spinlock_t) != 0) {
#ifdef CONFIG_NUMA
        if (size * sizeof(spinlock_t) > PAGE_SIZE)
            hashinfo->ehash_locks = vmalloc(size * sizeof(spinlock_t));
        else
#endif
        hashinfo->ehash_locks = kmalloc(size * sizeof(spinlock_t),
                        GFP_KERNEL);
        if (!hashinfo->ehash_locks)
            return ENOMEM;
        for (i = 0; i < size; i++)
            spin_lock_init(&hashinfo->ehash_locks[i]);
    }
    hashinfo->ehash_locks_mask = size - 1;
    return 0;
}

static inline void inet_ehash_locks_free(struct inet_hashinfo *hashinfo)
{
    if (hashinfo->ehash_locks) {
#ifdef CONFIG_NUMA
        unsigned int size = (hashinfo->ehash_locks_mask + 1) *
                            sizeof(spinlock_t);
        if (size > PAGE_SIZE)
            vfree(hashinfo->ehash_locks);
        else
#endif
        kfree(hashinfo->ehash_locks);
        hashinfo->ehash_locks = NULL;
    }
}

extern struct inet_bind_bucket *
            inet_bind_bucket_create(struct kmem_cache *cachep,
                        struct net *net,
                        struct inet_bind_hashbucket *head,
                        const unsigned short snum);
extern void inet_bind_bucket_destroy(struct kmem_cache *cachep,
                     struct inet_bind_bucket *tb);

static inline int inet_bhashfn(struct net *net,
        const __u16 lport, const int bhash_size)
{
    return (lport + net_hash_mix(net)) & (bhash_size - 1);
}

extern void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
               const unsigned short snum);

/* These can have wildcards, don't try too hard. */
static inline int inet_lhashfn(struct net *net, const unsigned short num)
{
    return (num + net_hash_mix(net)) & (INET_LHTABLE_SIZE - 1);
}

static inline int inet_sk_listen_hashfn(const struct sock *sk)
{
    return inet_lhashfn(sock_net(sk), inet_sk(sk)->inet_num);
}

/* Caller must disable local BH processing. */
extern int __inet_inherit_port(struct sock *sk, struct sock *child);

extern void inet_put_port(struct sock *sk);

void inet_hashinfo_init(struct inet_hashinfo *h);

extern int __inet_hash_nolisten(struct sock *sk, struct inet_timewait_sock *tw);
extern void inet_hash(struct sock *sk);
extern void inet_unhash(struct sock *sk);

extern struct sock *__inet_lookup_listener(struct net *net,
                       struct inet_hashinfo *hashinfo,
                       const __be32 daddr,
                       const unsigned short hnum,
                       const int dif);

static inline struct sock *inet_lookup_listener(struct net *net,
        struct inet_hashinfo *hashinfo,
        __be32 daddr, __be16 dport, int dif)
{
    return __inet_lookup_listener(net, hashinfo, daddr, ntohs(dport), dif);
}

/* Socket demux engine toys. */
/* What happens here is ugly; there's a pair of adjacent fields in
   struct inet_sock; __be16 dport followed by __u16 num.  We want to
   search by pair, so we combine the keys into a single 32bit value
   and compare with 32bit value read from &...->dport.  Let's at least
   make sure that it's not mixed with anything else...
   On 64bit targets we combine comparisons with pair of adjacent __be32
   fields in the same way.
*/
typedef __u32 __bitwise __portpair;
#ifdef __BIG_ENDIAN
#define INET_COMBINED_PORTS(__sport, __dport) \
    ((__force __portpair)(((__force __u32)(__be16)(__sport) << 16) | (__u32)(__dport)))
#else /* __LITTLE_ENDIAN */
#define INET_COMBINED_PORTS(__sport, __dport) \
    ((__force __portpair)(((__u32)(__dport) << 16) | (__force __u32)(__be16)(__sport)))
#endif

#if (BITS_PER_LONG == 64)
typedef __u64 __bitwise __addrpair;
#ifdef __BIG_ENDIAN
#define INET_ADDR_COOKIE(__name, __saddr, __daddr) \
    const __addrpair __name = (__force __addrpair) ( \
                   (((__force __u64)(__be32)(__saddr)) << 32) | \
                   ((__force __u64)(__be32)(__daddr)));
#else /* __LITTLE_ENDIAN */
#define INET_ADDR_COOKIE(__name, __saddr, __daddr) \
    const __addrpair __name = (__force __addrpair) ( \
                   (((__force __u64)(__be32)(__daddr)) << 32) | \
                   ((__force __u64)(__be32)(__saddr)));
#endif /* __BIG_ENDIAN */
#define INET_MATCH(__sk, __net, __hash, __cookie, __saddr, __daddr, __ports, __dif)\
    (((__sk)->sk_hash == (__hash)) && net_eq(sock_net(__sk), (__net)) &&    \
     ((*((__addrpair *)&(inet_sk(__sk)->inet_daddr))) == (__cookie))  &&    \
     ((*((__portpair *)&(inet_sk(__sk)->inet_dport))) == (__ports))   &&    \
     (!((__sk)->sk_bound_dev_if) || ((__sk)->sk_bound_dev_if == (__dif))))
#define INET_TW_MATCH(__sk, __net, __hash, __cookie, __saddr, __daddr, __ports, __dif)\
    (((__sk)->sk_hash == (__hash)) && net_eq(sock_net(__sk), (__net)) &&    \
     ((*((__addrpair *)&(inet_twsk(__sk)->tw_daddr))) == (__cookie)) && \
     ((*((__portpair *)&(inet_twsk(__sk)->tw_dport))) == (__ports)) &&  \
     (!((__sk)->sk_bound_dev_if) || ((__sk)->sk_bound_dev_if == (__dif))))
#else /* 32-bit arch */
#define INET_ADDR_COOKIE(__name, __saddr, __daddr)
#define INET_MATCH(__sk, __net, __hash, __cookie, __saddr, __daddr, __ports, __dif) \
    (((__sk)->sk_hash == (__hash)) && net_eq(sock_net(__sk), (__net))   &&  \
     (inet_sk(__sk)->inet_daddr == (__saddr))       &&  \
     (inet_sk(__sk)->inet_rcv_saddr == (__daddr))       &&  \
     ((*((__portpair *)&(inet_sk(__sk)->inet_dport))) == (__ports)) &&  \
     (!((__sk)->sk_bound_dev_if) || ((__sk)->sk_bound_dev_if == (__dif))))
#define INET_TW_MATCH(__sk, __net, __hash,__cookie, __saddr, __daddr, __ports, __dif)   \
    (((__sk)->sk_hash == (__hash)) && net_eq(sock_net(__sk), (__net))   &&  \
     (inet_twsk(__sk)->tw_daddr == (__saddr))       &&  \
     (inet_twsk(__sk)->tw_rcv_saddr == (__daddr))       &&  \
     ((*((__portpair *)&(inet_twsk(__sk)->tw_dport))) == (__ports)) &&  \
     (!((__sk)->sk_bound_dev_if) || ((__sk)->sk_bound_dev_if == (__dif))))
#endif /* 64-bit arch */

/*
 * Sockets in TCP_CLOSE state are _always_ taken out of the hash, so we need
 * not check it for lookups anymore, thanks Alexey. -DaveM
 *
 * Local BH must be disabled here.
 */
extern struct sock * __inet_lookup_established(struct net *net,
        struct inet_hashinfo *hashinfo,
        const __be32 saddr, const __be16 sport,
        const __be32 daddr, const u16 hnum, const int dif);

static inline struct sock *
    inet_lookup_established(struct net *net, struct inet_hashinfo *hashinfo,
                const __be32 saddr, const __be16 sport,
                const __be32 daddr, const __be16 dport,
                const int dif)
{
    return __inet_lookup_established(net, hashinfo, saddr, sport, daddr,
                     ntohs(dport), dif);
}

static inline struct sock *__inet_lookup(struct net *net,
                     struct inet_hashinfo *hashinfo,
                     const __be32 saddr, const __be16 sport,
                     const __be32 daddr, const __be16 dport,
                     const int dif)
{
    u16 hnum = ntohs(dport);
    struct sock *sk = __inet_lookup_established(net, hashinfo,
                saddr, sport, daddr, hnum, dif);

    return sk ? : __inet_lookup_listener(net, hashinfo, daddr, hnum, dif);
}

static inline struct sock *inet_lookup(struct net *net,
                       struct inet_hashinfo *hashinfo,
                       const __be32 saddr, const __be16 sport,
                       const __be32 daddr, const __be16 dport,
                       const int dif)
{
    struct sock *sk;

    local_bh_disable();
    sk = __inet_lookup(net, hashinfo, saddr, sport, daddr, dport, dif);
    local_bh_enable();

    return sk;
}

static inline struct sock *__inet_lookup_skb(struct inet_hashinfo *hashinfo,
                         struct sk_buff *skb,
                         const __be16 sport,
                         const __be16 dport)
{
    struct sock *sk = skb_steal_sock(skb);
    const struct iphdr *iph = ip_hdr(skb);

    if (sk)
        return sk;
    else
        return __inet_lookup(dev_net(skb_dst(skb)->dev), hashinfo,
                     iph->saddr, sport,
                     iph->daddr, dport, inet_iif(skb));
}

extern int __inet_hash_connect(struct inet_timewait_death_row *death_row,
        struct sock *sk,
        u32 port_offset,
        int (*check_established)(struct inet_timewait_death_row *,
            struct sock *, __u16, struct inet_timewait_sock **),
        int (*hash)(struct sock *sk, struct inet_timewait_sock *twp));

extern int inet_hash_connect(struct inet_timewait_death_row *death_row,
                 struct sock *sk);
#endif /* _INET_HASHTABLES_H */