struct ip_session {
    struct ip_session *next;
    __be32   addr;
    __be32   netmask;
};
#define HASH_SESSION_SIZE   256
#define HASH_SESSION(addr)  (ntohr(addr) & 0xFF)

static struct ip_session *ip_sessions[HASH_SESSION_SIZE] = {};
static inline struct ip_session **ip_session_bucket(__be32 addr)
{
    __be32   h0 = HASH_SESSION(addr);

    return (&(ip_sessions[h0]));
}

static int ip_session_add1(__be32 addr, __be32 netmask)
{
    struct ip_session *session, **ms;

    write_lock(&session_lock);

    if((session = (struct ip_session *)kzalloc(sizeof(struct ip_session), GFP_ATOMIC)) == NULL)
    {
        write_unlock(&session_lock);
        return -1;
    }

    session->addr = addr;
    session->netmask = netmask;

    ms = ip_session_bucket(addr);
    session->next = *ms;
    *ms = session;

    write_unlock(&session_lock);
    return 0;
}

static int ip_session_add2(__be32 addr, __be32 netmask)
{
    struct ip_session *session, **ms;
    struct ip_session s;

    write_lock(&session_lock);

    session = &s;

    session->addr = addr;
    session->netmask = netmask;

    ms = ip_session_bucket(addr);
    session->next = *ms;
    *ms = session;

    write_unlock(&session_lock);
    return 0;
}