ip_vs_app.c

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/*
 * ip_vs_app.c: Application module support for IPVS
 *
 * Authors:     Wensong Zhang <[email protected]>
 *
 *              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.
 *
 * Most code here is taken from ip_masq_app.c in kernel 2.2. The difference
 * is that ip_vs_app module handles the reverse direction (incoming requests
 * and outgoing responses).
 *
 *      IP_MASQ_APP application masquerading module
 *
 * Author:  Juan Jose Ciarlante, <[email protected]>
 *
 */

#define KMSG_COMPONENT "IPVS"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/netfilter.h>
#include <linux/slab.h>
#include <net/net_namespace.h>
#include <net/protocol.h>
#include <net/tcp.h>
#include <linux/stat.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/mutex.h>

#include <net/ip_vs.h>

EXPORT_SYMBOL(register_ip_vs_app);
EXPORT_SYMBOL(unregister_ip_vs_app);
EXPORT_SYMBOL(register_ip_vs_app_inc);

static DEFINE_MUTEX(__ip_vs_app_mutex);

/*
 *  Get an ip_vs_app object
 */
static inline int ip_vs_app_get(struct ip_vs_app *app)
{
    return try_module_get(app->module);
}


static inline void ip_vs_app_put(struct ip_vs_app *app)
{
    module_put(app->module);
}


/*
 *  Allocate/initialize app incarnation and register it in proto apps.
 */
static int
ip_vs_app_inc_new(struct net *net, struct ip_vs_app *app, __u16 proto,
          __u16 port)
{
    struct ip_vs_protocol *pp;
    struct ip_vs_app *inc;
    int ret;

    if (!(pp = ip_vs_proto_get(proto)))
        return -EPROTONOSUPPORT;

    if (!pp->unregister_app)
        return -EOPNOTSUPP;

    inc = kmemdup(app, sizeof(*inc), GFP_KERNEL);
    if (!inc)
        return -ENOMEM;
    INIT_LIST_HEAD(&inc->p_list);
    INIT_LIST_HEAD(&inc->incs_list);
    inc->app = app;
    inc->port = htons(port);
    atomic_set(&inc->usecnt, 0);

    if (app->timeouts) {
        inc->timeout_table =
            ip_vs_create_timeout_table(app->timeouts,
                           app->timeouts_size);
        if (!inc->timeout_table) {
            ret = -ENOMEM;
            goto out;
        }
    }

    ret = pp->register_app(net, inc);
    if (ret)
        goto out;

    list_add(&inc->a_list, &app->incs_list);
    IP_VS_DBG(9, "%s App %s:%u registered\n",
          pp->name, inc->name, ntohs(inc->port));

    return 0;

  out:
    kfree(inc->timeout_table);
    kfree(inc);
    return ret;
}


/*
 *  Release app incarnation
 */
static void
ip_vs_app_inc_release(struct net *net, struct ip_vs_app *inc)
{
    struct ip_vs_protocol *pp;

    if (!(pp = ip_vs_proto_get(inc->protocol)))
        return;

    if (pp->unregister_app)
        pp->unregister_app(net, inc);

    IP_VS_DBG(9, "%s App %s:%u unregistered\n",
          pp->name, inc->name, ntohs(inc->port));

    list_del(&inc->a_list);

    kfree(inc->timeout_table);
    kfree(inc);
}


/*
 *  Get reference to app inc (only called from softirq)
 *
 */
int ip_vs_app_inc_get(struct ip_vs_app *inc)
{
    int result;

    atomic_inc(&inc->usecnt);
    if (unlikely((result = ip_vs_app_get(inc->app)) != 1))
        atomic_dec(&inc->usecnt);
    return result;
}


/*
 *  Put the app inc (only called from timer or net softirq)
 */
void ip_vs_app_inc_put(struct ip_vs_app *inc)
{
    ip_vs_app_put(inc->app);
    atomic_dec(&inc->usecnt);
}


/*
 *  Register an application incarnation in protocol applications
 */
int
register_ip_vs_app_inc(struct net *net, struct ip_vs_app *app, __u16 proto,
               __u16 port)
{
    int result;

    mutex_lock(&__ip_vs_app_mutex);

    result = ip_vs_app_inc_new(net, app, proto, port);

    mutex_unlock(&__ip_vs_app_mutex);

    return result;
}


/* Register application for netns */
struct ip_vs_app *register_ip_vs_app(struct net *net, struct ip_vs_app *app)
{
    struct netns_ipvs *ipvs = net_ipvs(net);
    struct ip_vs_app *a;
    int err = 0;

    if (!ipvs)
        return ERR_PTR(-ENOENT);

    mutex_lock(&__ip_vs_app_mutex);

    list_for_each_entry(a, &ipvs->app_list, a_list) {
        if (!strcmp(app->name, a->name)) {
            err = -EEXIST;
            goto out_unlock;
        }
    }
    a = kmemdup(app, sizeof(*app), GFP_KERNEL);
    if (!a) {
        err = -ENOMEM;
        goto out_unlock;
    }
    INIT_LIST_HEAD(&a->incs_list);
    list_add(&a->a_list, &ipvs->app_list);
    /* increase the module use count */
    ip_vs_use_count_inc();

out_unlock:
    mutex_unlock(&__ip_vs_app_mutex);

    return err ? ERR_PTR(err) : a;
}


/*
 *  ip_vs_app unregistration routine
 *  We are sure there are no app incarnations attached to services
 */
void unregister_ip_vs_app(struct net *net, struct ip_vs_app *app)
{
    struct netns_ipvs *ipvs = net_ipvs(net);
    struct ip_vs_app *a, *anxt, *inc, *nxt;

    if (!ipvs)
        return;

    mutex_lock(&__ip_vs_app_mutex);

    list_for_each_entry_safe(a, anxt, &ipvs->app_list, a_list) {
        if (app && strcmp(app->name, a->name))
            continue;
        list_for_each_entry_safe(inc, nxt, &a->incs_list, a_list) {
            ip_vs_app_inc_release(net, inc);
        }

        list_del(&a->a_list);
        kfree(a);

        /* decrease the module use count */
        ip_vs_use_count_dec();
    }

    mutex_unlock(&__ip_vs_app_mutex);
}


/*
 *  Bind ip_vs_conn to its ip_vs_app (called by cp constructor)
 */
int ip_vs_bind_app(struct ip_vs_conn *cp,
           struct ip_vs_protocol *pp)
{
    return pp->app_conn_bind(cp);
}


/*
 *  Unbind cp from application incarnation (called by cp destructor)
 */
void ip_vs_unbind_app(struct ip_vs_conn *cp)
{
    struct ip_vs_app *inc = cp->app;

    if (!inc)
        return;

    if (inc->unbind_conn)
        inc->unbind_conn(inc, cp);
    if (inc->done_conn)
        inc->done_conn(inc, cp);
    ip_vs_app_inc_put(inc);
    cp->app = NULL;
}


/*
 *  Fixes th->seq based on ip_vs_seq info.
 */
static inline void vs_fix_seq(const struct ip_vs_seq *vseq, struct tcphdr *th)
{
    __u32 seq = ntohl(th->seq);

    /*
     *  Adjust seq with delta-offset for all packets after
     *  the most recent resized pkt seq and with previous_delta offset
     *  for all packets before most recent resized pkt seq.
     */
    if (vseq->delta || vseq->previous_delta) {
        if(after(seq, vseq->init_seq)) {
            th->seq = htonl(seq + vseq->delta);
            IP_VS_DBG(9, "%s(): added delta (%d) to seq\n",
                  __func__, vseq->delta);
        } else {
            th->seq = htonl(seq + vseq->previous_delta);
            IP_VS_DBG(9, "%s(): added previous_delta (%d) to seq\n",
                  __func__, vseq->previous_delta);
        }
    }
}


/*
 *  Fixes th->ack_seq based on ip_vs_seq info.
 */
static inline void
vs_fix_ack_seq(const struct ip_vs_seq *vseq, struct tcphdr *th)
{
    __u32 ack_seq = ntohl(th->ack_seq);

    /*
     * Adjust ack_seq with delta-offset for
     * the packets AFTER most recent resized pkt has caused a shift
     * for packets before most recent resized pkt, use previous_delta
     */
    if (vseq->delta || vseq->previous_delta) {
        /* since ack_seq is the number of octet that is expected
           to receive next, so compare it with init_seq+delta */
        if(after(ack_seq, vseq->init_seq+vseq->delta)) {
            th->ack_seq = htonl(ack_seq - vseq->delta);
            IP_VS_DBG(9, "%s(): subtracted delta "
                  "(%d) from ack_seq\n", __func__, vseq->delta);

        } else {
            th->ack_seq = htonl(ack_seq - vseq->previous_delta);
            IP_VS_DBG(9, "%s(): subtracted "
                  "previous_delta (%d) from ack_seq\n",
                  __func__, vseq->previous_delta);
        }
    }
}


/*
 *  Updates ip_vs_seq if pkt has been resized
 *  Assumes already checked proto==IPPROTO_TCP and diff!=0.
 */
static inline void vs_seq_update(struct ip_vs_conn *cp, struct ip_vs_seq *vseq,
                 unsigned int flag, __u32 seq, int diff)
{
    /* spinlock is to keep updating cp->flags atomic */
    spin_lock(&cp->lock);
    if (!(cp->flags & flag) || after(seq, vseq->init_seq)) {
        vseq->previous_delta = vseq->delta;
        vseq->delta += diff;
        vseq->init_seq = seq;
        cp->flags |= flag;
    }
    spin_unlock(&cp->lock);
}

static inline int app_tcp_pkt_out(struct ip_vs_conn *cp, struct sk_buff *skb,
                  struct ip_vs_app *app)
{
    int diff;
    const unsigned int tcp_offset = ip_hdrlen(skb);
    struct tcphdr *th;
    __u32 seq;

    if (!skb_make_writable(skb, tcp_offset + sizeof(*th)))
        return 0;

    th = (struct tcphdr *)(skb_network_header(skb) + tcp_offset);

    /*
     *  Remember seq number in case this pkt gets resized
     */
    seq = ntohl(th->seq);

    /*
     *  Fix seq stuff if flagged as so.
     */
    if (cp->flags & IP_VS_CONN_F_OUT_SEQ)
        vs_fix_seq(&cp->out_seq, th);
    if (cp->flags & IP_VS_CONN_F_IN_SEQ)
        vs_fix_ack_seq(&cp->in_seq, th);

    /*
     *  Call private output hook function
     */
    if (app->pkt_out == NULL)
        return 1;

    if (!app->pkt_out(app, cp, skb, &diff))
        return 0;

    /*
     *  Update ip_vs seq stuff if len has changed.
     */
    if (diff != 0)
        vs_seq_update(cp, &cp->out_seq,
                  IP_VS_CONN_F_OUT_SEQ, seq, diff);

    return 1;
}

/*
 *  Output pkt hook. Will call bound ip_vs_app specific function
 *  called by ipvs packet handler, assumes previously checked cp!=NULL
 *  returns false if it can't handle packet (oom)
 */
int ip_vs_app_pkt_out(struct ip_vs_conn *cp, struct sk_buff *skb)
{
    struct ip_vs_app *app;

    /*
     *  check if application module is bound to
     *  this ip_vs_conn.
     */
    if ((app = cp->app) == NULL)
        return 1;

    /* TCP is complicated */
    if (cp->protocol == IPPROTO_TCP)
        return app_tcp_pkt_out(cp, skb, app);

    /*
     *  Call private output hook function
     */
    if (app->pkt_out == NULL)
        return 1;

    return app->pkt_out(app, cp, skb, NULL);
}


static inline int app_tcp_pkt_in(struct ip_vs_conn *cp, struct sk_buff *skb,
                 struct ip_vs_app *app)
{
    int diff;
    const unsigned int tcp_offset = ip_hdrlen(skb);
    struct tcphdr *th;
    __u32 seq;

    if (!skb_make_writable(skb, tcp_offset + sizeof(*th)))
        return 0;

    th = (struct tcphdr *)(skb_network_header(skb) + tcp_offset);

    /*
     *  Remember seq number in case this pkt gets resized
     */
    seq = ntohl(th->seq);

    /*
     *  Fix seq stuff if flagged as so.
     */
    if (cp->flags & IP_VS_CONN_F_IN_SEQ)
        vs_fix_seq(&cp->in_seq, th);
    if (cp->flags & IP_VS_CONN_F_OUT_SEQ)
        vs_fix_ack_seq(&cp->out_seq, th);

    /*
     *  Call private input hook function
     */
    if (app->pkt_in == NULL)
        return 1;

    if (!app->pkt_in(app, cp, skb, &diff))
        return 0;

    /*
     *  Update ip_vs seq stuff if len has changed.
     */
    if (diff != 0)
        vs_seq_update(cp, &cp->in_seq,
                  IP_VS_CONN_F_IN_SEQ, seq, diff);

    return 1;
}

/*
 *  Input pkt hook. Will call bound ip_vs_app specific function
 *  called by ipvs packet handler, assumes previously checked cp!=NULL.
 *  returns false if can't handle packet (oom).
 */
int ip_vs_app_pkt_in(struct ip_vs_conn *cp, struct sk_buff *skb)
{
    struct ip_vs_app *app;

    /*
     *  check if application module is bound to
     *  this ip_vs_conn.
     */
    if ((app = cp->app) == NULL)
        return 1;

    /* TCP is complicated */
    if (cp->protocol == IPPROTO_TCP)
        return app_tcp_pkt_in(cp, skb, app);

    /*
     *  Call private input hook function
     */
    if (app->pkt_in == NULL)
        return 1;

    return app->pkt_in(app, cp, skb, NULL);
}


#ifdef CONFIG_PROC_FS
/*
 *  /proc/net/ip_vs_app entry function
 */

static struct ip_vs_app *ip_vs_app_idx(struct netns_ipvs *ipvs, loff_t pos)
{
    struct ip_vs_app *app, *inc;

    list_for_each_entry(app, &ipvs->app_list, a_list) {
        list_for_each_entry(inc, &app->incs_list, a_list) {
            if (pos-- == 0)
                return inc;
        }
    }
    return NULL;

}

static void *ip_vs_app_seq_start(struct seq_file *seq, loff_t *pos)
{
    struct net *net = seq_file_net(seq);
    struct netns_ipvs *ipvs = net_ipvs(net);

    mutex_lock(&__ip_vs_app_mutex);

    return *pos ? ip_vs_app_idx(ipvs, *pos - 1) : SEQ_START_TOKEN;
}

static void *ip_vs_app_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
    struct ip_vs_app *inc, *app;
    struct list_head *e;
    struct net *net = seq_file_net(seq);
    struct netns_ipvs *ipvs = net_ipvs(net);

    ++*pos;
    if (v == SEQ_START_TOKEN)
        return ip_vs_app_idx(ipvs, 0);

    inc = v;
    app = inc->app;

    if ((e = inc->a_list.next) != &app->incs_list)
        return list_entry(e, struct ip_vs_app, a_list);

    /* go on to next application */
    for (e = app->a_list.next; e != &ipvs->app_list; e = e->next) {
        app = list_entry(e, struct ip_vs_app, a_list);
        list_for_each_entry(inc, &app->incs_list, a_list) {
            return inc;
        }
    }
    return NULL;
}

static void ip_vs_app_seq_stop(struct seq_file *seq, void *v)
{
    mutex_unlock(&__ip_vs_app_mutex);
}

static int ip_vs_app_seq_show(struct seq_file *seq, void *v)
{
    if (v == SEQ_START_TOKEN)
        seq_puts(seq, "prot port    usecnt name\n");
    else {
        const struct ip_vs_app *inc = v;

        seq_printf(seq, "%-3s  %-7u %-6d %-17s\n",
               ip_vs_proto_name(inc->protocol),
               ntohs(inc->port),
               atomic_read(&inc->usecnt),
               inc->name);
    }
    return 0;
}

static const struct seq_operations ip_vs_app_seq_ops = {
    .start = ip_vs_app_seq_start,
    .next  = ip_vs_app_seq_next,
    .stop  = ip_vs_app_seq_stop,
    .show  = ip_vs_app_seq_show,
};

static int ip_vs_app_open(struct inode *inode, struct file *file)
{
    return seq_open_net(inode, file, &ip_vs_app_seq_ops,
                sizeof(struct seq_net_private));
}

static const struct file_operations ip_vs_app_fops = {
    .owner   = THIS_MODULE,
    .open    = ip_vs_app_open,
    .read    = seq_read,
    .llseek  = seq_lseek,
    .release = seq_release_net,
};
#endif

int __net_init ip_vs_app_net_init(struct net *net)
{
    struct netns_ipvs *ipvs = net_ipvs(net);

    INIT_LIST_HEAD(&ipvs->app_list);
    proc_net_fops_create(net, "ip_vs_app", 0, &ip_vs_app_fops);
    return 0;
}

void __net_exit ip_vs_app_net_cleanup(struct net *net)
{
    unregister_ip_vs_app(net, NULL /* all */);
    proc_net_remove(net, "ip_vs_app");
}