ip_vs_nfct.c

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/*
 * ip_vs_nfct.c:    Netfilter connection tracking support for IPVS
 *
 * Portions Copyright (C) 2001-2002
 * Antefacto Ltd, 181 Parnell St, Dublin 1, Ireland.
 *
 * Portions Copyright (C) 2003-2010
 * Julian Anastasov
 *
 *
 * This code 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *
 * Authors:
 * Ben North <[email protected]>
 * Julian Anastasov <[email protected]>     Reorganize and sync with latest kernels
 * Hannes Eder <[email protected]>   Extend NFCT support for FTP, ipvs match
 *
 *
 * Current status:
 *
 * - provide conntrack confirmation for new and related connections, by
 * this way we can see their proper conntrack state in all hooks
 * - support for all forwarding methods, not only NAT
 * - FTP support (NAT), ability to support other NAT apps with expectations
 * - to correctly create expectations for related NAT connections the proper
 * NF conntrack support must be already installed, eg. ip_vs_ftp requires
 * nf_conntrack_ftp ... iptables_nat for the same ports (but no iptables
 * NAT rules are needed)
 * - alter reply for NAT when forwarding packet in original direction:
 * conntrack from client in NEW or RELATED (Passive FTP DATA) state or
 * when RELATED conntrack is created from real server (Active FTP DATA)
 * - if iptables_nat is not loaded the Passive FTP will not work (the
 * PASV response can not be NAT-ed) but Active FTP should work
 *
 */

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

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/compiler.h>
#include <linux/vmalloc.h>
#include <linux/skbuff.h>
#include <net/ip.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <net/ip_vs.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_zones.h>


#define FMT_TUPLE   "%pI4:%u->%pI4:%u/%u"
#define ARG_TUPLE(T)    &(T)->src.u3.ip, ntohs((T)->src.u.all), \
            &(T)->dst.u3.ip, ntohs((T)->dst.u.all), \
            (T)->dst.protonum

#define FMT_CONN    "%pI4:%u->%pI4:%u->%pI4:%u/%u:%u"
#define ARG_CONN(C) &((C)->caddr.ip), ntohs((C)->cport), \
            &((C)->vaddr.ip), ntohs((C)->vport), \
            &((C)->daddr.ip), ntohs((C)->dport), \
            (C)->protocol, (C)->state

void
ip_vs_update_conntrack(struct sk_buff *skb, struct ip_vs_conn *cp, int outin)
{
    enum ip_conntrack_info ctinfo;
    struct nf_conn *ct = ct = nf_ct_get(skb, &ctinfo);
    struct nf_conntrack_tuple new_tuple;

    if (ct == NULL || nf_ct_is_confirmed(ct) || nf_ct_is_untracked(ct) ||
        nf_ct_is_dying(ct))
        return;

    /* Never alter conntrack for non-NAT conns */
    if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ)
        return;

    /* Alter reply only in original direction */
    if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
        return;

    /*
     * The connection is not yet in the hashtable, so we update it.
     * CIP->VIP will remain the same, so leave the tuple in
     * IP_CT_DIR_ORIGINAL untouched.  When the reply comes back from the
     * real-server we will see RIP->DIP.
     */
    new_tuple = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
    /*
     * This will also take care of UDP and other protocols.
     */
    if (outin) {
        new_tuple.src.u3 = cp->daddr;
        if (new_tuple.dst.protonum != IPPROTO_ICMP &&
            new_tuple.dst.protonum != IPPROTO_ICMPV6)
            new_tuple.src.u.tcp.port = cp->dport;
    } else {
        new_tuple.dst.u3 = cp->vaddr;
        if (new_tuple.dst.protonum != IPPROTO_ICMP &&
            new_tuple.dst.protonum != IPPROTO_ICMPV6)
            new_tuple.dst.u.tcp.port = cp->vport;
    }
    IP_VS_DBG(7, "%s: Updating conntrack ct=%p, status=0x%lX, "
          "ctinfo=%d, old reply=" FMT_TUPLE
          ", new reply=" FMT_TUPLE ", cp=" FMT_CONN "\n",
          __func__, ct, ct->status, ctinfo,
          ARG_TUPLE(&ct->tuplehash[IP_CT_DIR_REPLY].tuple),
          ARG_TUPLE(&new_tuple), ARG_CONN(cp));
    nf_conntrack_alter_reply(ct, &new_tuple);
}

int ip_vs_confirm_conntrack(struct sk_buff *skb)
{
    return nf_conntrack_confirm(skb);
}

/*
 * Called from init_conntrack() as expectfn handler.
 */
static void ip_vs_nfct_expect_callback(struct nf_conn *ct,
    struct nf_conntrack_expect *exp)
{
    struct nf_conntrack_tuple *orig, new_reply;
    struct ip_vs_conn *cp;
    struct ip_vs_conn_param p;
    struct net *net = nf_ct_net(ct);

    if (exp->tuple.src.l3num != PF_INET)
        return;

    /*
     * We assume that no NF locks are held before this callback.
     * ip_vs_conn_out_get and ip_vs_conn_in_get should match their
     * expectations even if they use wildcard values, now we provide the
     * actual values from the newly created original conntrack direction.
     * The conntrack is confirmed when packet reaches IPVS hooks.
     */

    /* RS->CLIENT */
    orig = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
    ip_vs_conn_fill_param(net, exp->tuple.src.l3num, orig->dst.protonum,
                  &orig->src.u3, orig->src.u.tcp.port,
                  &orig->dst.u3, orig->dst.u.tcp.port, &p);
    cp = ip_vs_conn_out_get(&p);
    if (cp) {
        /* Change reply CLIENT->RS to CLIENT->VS */
        new_reply = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
        IP_VS_DBG(7, "%s: ct=%p, status=0x%lX, tuples=" FMT_TUPLE ", "
              FMT_TUPLE ", found inout cp=" FMT_CONN "\n",
              __func__, ct, ct->status,
              ARG_TUPLE(orig), ARG_TUPLE(&new_reply),
              ARG_CONN(cp));
        new_reply.dst.u3 = cp->vaddr;
        new_reply.dst.u.tcp.port = cp->vport;
        IP_VS_DBG(7, "%s: ct=%p, new tuples=" FMT_TUPLE ", " FMT_TUPLE
              ", inout cp=" FMT_CONN "\n",
              __func__, ct,
              ARG_TUPLE(orig), ARG_TUPLE(&new_reply),
              ARG_CONN(cp));
        goto alter;
    }

    /* CLIENT->VS */
    cp = ip_vs_conn_in_get(&p);
    if (cp) {
        /* Change reply VS->CLIENT to RS->CLIENT */
        new_reply = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
        IP_VS_DBG(7, "%s: ct=%p, status=0x%lX, tuples=" FMT_TUPLE ", "
              FMT_TUPLE ", found outin cp=" FMT_CONN "\n",
              __func__, ct, ct->status,
              ARG_TUPLE(orig), ARG_TUPLE(&new_reply),
              ARG_CONN(cp));
        new_reply.src.u3 = cp->daddr;
        new_reply.src.u.tcp.port = cp->dport;
        IP_VS_DBG(7, "%s: ct=%p, new tuples=" FMT_TUPLE ", "
              FMT_TUPLE ", outin cp=" FMT_CONN "\n",
              __func__, ct,
              ARG_TUPLE(orig), ARG_TUPLE(&new_reply),
              ARG_CONN(cp));
        goto alter;
    }

    IP_VS_DBG(7, "%s: ct=%p, status=0x%lX, tuple=" FMT_TUPLE
          " - unknown expect\n",
          __func__, ct, ct->status, ARG_TUPLE(orig));
    return;

alter:
    /* Never alter conntrack for non-NAT conns */
    if (IP_VS_FWD_METHOD(cp) == IP_VS_CONN_F_MASQ)
        nf_conntrack_alter_reply(ct, &new_reply);
    ip_vs_conn_put(cp);
    return;
}

/*
 * Create NF conntrack expectation with wildcard (optional) source port.
 * Then the default callback function will alter the reply and will confirm
 * the conntrack entry when the first packet comes.
 * Use port 0 to expect connection from any port.
 */
void ip_vs_nfct_expect_related(struct sk_buff *skb, struct nf_conn *ct,
                   struct ip_vs_conn *cp, u_int8_t proto,
                   const __be16 port, int from_rs)
{
    struct nf_conntrack_expect *exp;

    if (ct == NULL || nf_ct_is_untracked(ct))
        return;

    exp = nf_ct_expect_alloc(ct);
    if (!exp)
        return;

    nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, nf_ct_l3num(ct),
            from_rs ? &cp->daddr : &cp->caddr,
            from_rs ? &cp->caddr : &cp->vaddr,
            proto, port ? &port : NULL,
            from_rs ? &cp->cport : &cp->vport);

    exp->expectfn = ip_vs_nfct_expect_callback;

    IP_VS_DBG(7, "%s: ct=%p, expect tuple=" FMT_TUPLE "\n",
        __func__, ct, ARG_TUPLE(&exp->tuple));
    nf_ct_expect_related(exp);
    nf_ct_expect_put(exp);
}
EXPORT_SYMBOL(ip_vs_nfct_expect_related);

/*
 * Our connection was terminated, try to drop the conntrack immediately
 */
void ip_vs_conn_drop_conntrack(struct ip_vs_conn *cp)
{
    struct nf_conntrack_tuple_hash *h;
    struct nf_conn *ct;
    struct nf_conntrack_tuple tuple;

    if (!cp->cport)
        return;

    tuple = (struct nf_conntrack_tuple) {
        .dst = { .protonum = cp->protocol, .dir = IP_CT_DIR_ORIGINAL } };
    tuple.src.u3 = cp->caddr;
    tuple.src.u.all = cp->cport;
    tuple.src.l3num = cp->af;
    tuple.dst.u3 = cp->vaddr;
    tuple.dst.u.all = cp->vport;

    IP_VS_DBG(7, "%s: dropping conntrack with tuple=" FMT_TUPLE
        " for conn " FMT_CONN "\n",
        __func__, ARG_TUPLE(&tuple), ARG_CONN(cp));

    h = nf_conntrack_find_get(ip_vs_conn_net(cp), NF_CT_DEFAULT_ZONE,
                  &tuple);
    if (h) {
        ct = nf_ct_tuplehash_to_ctrack(h);
        /* Show what happens instead of calling nf_ct_kill() */
        if (del_timer(&ct->timeout)) {
            IP_VS_DBG(7, "%s: ct=%p, deleted conntrack timer for tuple="
                FMT_TUPLE "\n",
                __func__, ct, ARG_TUPLE(&tuple));
            if (ct->timeout.function)
                ct->timeout.function(ct->timeout.data);
        } else {
            IP_VS_DBG(7, "%s: ct=%p, no conntrack timer for tuple="
                FMT_TUPLE "\n",
                __func__, ct, ARG_TUPLE(&tuple));
        }
        nf_ct_put(ct);
    } else {
        IP_VS_DBG(7, "%s: no conntrack for tuple=" FMT_TUPLE "\n",
            __func__, ARG_TUPLE(&tuple));
    }
}