root/include/net/inet_frag.h

INCLUDED FROM

DEFINITIONS

1. inet_frag_put
2. frag_mem_limit
3. sub_frag_mem_limit
4. add_frag_mem_limit
5. init_frag_mem_limit
6. sum_frag_mem_limit

#ifndef __NET_FRAG_H__
#define __NET_FRAG_H__

#include <linux/percpu_counter.h>

struct netns_frags {
        /* The percpu_counter "mem" need to be cacheline aligned.
         *  mem.count must not share cacheline with other writers
         */
        struct percpu_counter   mem ____cacheline_aligned_in_smp;

        /* sysctls */
        int                     timeout;
        int                     high_thresh;
        int                     low_thresh;
};

/**
 * fragment queue flags
 *
 * @INET_FRAG_FIRST_IN: first fragment has arrived
 * @INET_FRAG_LAST_IN: final fragment has arrived
 * @INET_FRAG_COMPLETE: frag queue has been processed and is due for destruction
 * @INET_FRAG_EVICTED: frag queue is being evicted
 */
enum {
        INET_FRAG_FIRST_IN      = BIT(0),
        INET_FRAG_LAST_IN       = BIT(1),
        INET_FRAG_COMPLETE      = BIT(2),
        INET_FRAG_EVICTED       = BIT(3)
};

/**
 * struct inet_frag_queue - fragment queue
 *
 * @lock: spinlock protecting the queue
 * @timer: queue expiration timer
 * @list: hash bucket list
 * @refcnt: reference count of the queue
 * @fragments: received fragments head
 * @fragments_tail: received fragments tail
 * @stamp: timestamp of the last received fragment
 * @len: total length of the original datagram
 * @meat: length of received fragments so far
 * @flags: fragment queue flags
 * @max_size: (ipv4 only) maximum received fragment size with IP_DF set
 * @net: namespace that this frag belongs to
 */
struct inet_frag_queue {
        spinlock_t              lock;
        struct timer_list       timer;
        struct hlist_node       list;
        atomic_t                refcnt;
        struct sk_buff          *fragments;
        struct sk_buff          *fragments_tail;
        ktime_t                 stamp;
        int                     len;
        int                     meat;
        __u8                    flags;
        u16                     max_size;
        struct netns_frags      *net;
};

#define INETFRAGS_HASHSZ        1024

/* averaged:
 * max_depth = default ipfrag_high_thresh / INETFRAGS_HASHSZ /
 *             rounded up (SKB_TRUELEN(0) + sizeof(struct ipq or
 *             struct frag_queue))
 */
#define INETFRAGS_MAXDEPTH      128

struct inet_frag_bucket {
        struct hlist_head       chain;
        spinlock_t              chain_lock;
};

struct inet_frags {
        struct inet_frag_bucket hash[INETFRAGS_HASHSZ];

        struct work_struct      frags_work;
        unsigned int next_bucket;
        unsigned long last_rebuild_jiffies;
        bool rebuild;

        /* The first call to hashfn is responsible to initialize
         * rnd. This is best done with net_get_random_once.
         *
         * rnd_seqlock is used to let hash insertion detect
         * when it needs to re-lookup the hash chain to use.
         */
        u32                     rnd;
        seqlock_t               rnd_seqlock;
        int                     qsize;

        unsigned int            (*hashfn)(const struct inet_frag_queue *);
        bool                    (*match)(const struct inet_frag_queue *q,
                                         const void *arg);
        void                    (*constructor)(struct inet_frag_queue *q,
                                               const void *arg);
        void                    (*destructor)(struct inet_frag_queue *);
        void                    (*skb_free)(struct sk_buff *);
        void                    (*frag_expire)(unsigned long data);
        struct kmem_cache       *frags_cachep;
        const char              *frags_cache_name;
};

int inet_frags_init(struct inet_frags *);
void inet_frags_fini(struct inet_frags *);

void inet_frags_init_net(struct netns_frags *nf);
void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f);

void inet_frag_kill(struct inet_frag_queue *q, struct inet_frags *f);
void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f);
struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
                struct inet_frags *f, void *key, unsigned int hash);

void inet_frag_maybe_warn_overflow(struct inet_frag_queue *q,
                                   const char *prefix);

static inline void inet_frag_put(struct inet_frag_queue *q, struct inet_frags *f)
{
        if (atomic_dec_and_test(&q->refcnt))
                inet_frag_destroy(q, f);
}

/* Memory Tracking Functions. */

/* The default percpu_counter batch size is not big enough to scale to
 * fragmentation mem acct sizes.
 * The mem size of a 64K fragment is approx:
 *  (44 fragments * 2944 truesize) + frag_queue struct(200) = 129736 bytes
 */
static unsigned int frag_percpu_counter_batch = 130000;

static inline int frag_mem_limit(struct netns_frags *nf)
{
        return percpu_counter_read(&nf->mem);
}

static inline void sub_frag_mem_limit(struct inet_frag_queue *q, int i)
{
        __percpu_counter_add(&q->net->mem, -i, frag_percpu_counter_batch);
}

static inline void add_frag_mem_limit(struct inet_frag_queue *q, int i)
{
        __percpu_counter_add(&q->net->mem, i, frag_percpu_counter_batch);
}

static inline void init_frag_mem_limit(struct netns_frags *nf)
{
        percpu_counter_init(&nf->mem, 0, GFP_KERNEL);
}

static inline unsigned int sum_frag_mem_limit(struct netns_frags *nf)
{
        unsigned int res;

        local_bh_disable();
        res = percpu_counter_sum_positive(&nf->mem);
        local_bh_enable();

        return res;
}

/* RFC 3168 support :
 * We want to check ECN values of all fragments, do detect invalid combinations.
 * In ipq->ecn, we store the OR value of each ip4_frag_ecn() fragment value.
 */
#define IPFRAG_ECN_NOT_ECT      0x01 /* one frag had ECN_NOT_ECT */
#define IPFRAG_ECN_ECT_1        0x02 /* one frag had ECN_ECT_1 */
#define IPFRAG_ECN_ECT_0        0x04 /* one frag had ECN_ECT_0 */
#define IPFRAG_ECN_CE           0x08 /* one frag had ECN_CE */

extern const u8 ip_frag_ecn_table[16];

#endif