// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * 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
 *
 * Authors:
 * Ben North <ben@redfrontdoor.org>
 * Julian Anastasov <ja@ssi.bg>         Reorganize and sync with latest kernels
 * Hannes Eder <heder@google.com>       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 pr_fmt(fmt) "IPVS: " 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_seqadj.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_zones.h>


#define FMT_TUPLE       "%s:%u->%s:%u/%u"
#define ARG_TUPLE(T)    IP_VS_DBG_ADDR((T)->src.l3num, &(T)->src.u3),   \
                        ntohs((T)->src.u.all),                          \
                        IP_VS_DBG_ADDR((T)->src.l3num, &(T)->dst.u3),   \
                        ntohs((T)->dst.u.all),                          \
                        (T)->dst.protonum

#define FMT_CONN        "%s:%u->%s:%u->%s:%u/%u:%u"
#define ARG_CONN(C)     IP_VS_DBG_ADDR((C)->af, &((C)->caddr)),         \
                        ntohs((C)->cport),                              \
                        IP_VS_DBG_ADDR((C)->af, &((C)->vaddr)),         \
                        ntohs((C)->vport),                              \
                        IP_VS_DBG_ADDR((C)->daf, &((C)->daddr)),        \
                        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 = nf_ct_get(skb, &ctinfo);
        struct nf_conntrack_tuple new_tuple;

        if (ct == NULL || nf_ct_is_confirmed(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;

        /* Never alter conntrack for OPS conns (no reply is expected) */
        if (cp->flags & IP_VS_CONN_F_ONE_PACKET)
                return;

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

        /* Applications may adjust TCP seqs */
        if (cp->app && nf_ct_protonum(ct) == IPPROTO_TCP &&
            !nfct_seqadj(ct) && !nfct_seqadj_ext_add(ct))
                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_BUF(7, "%s: Updating conntrack ct=%p, status=0x%lX, "
                      "ctinfo=%d, old reply=" FMT_TUPLE "\n",
                      __func__, ct, ct->status, ctinfo,
                      ARG_TUPLE(&ct->tuplehash[IP_CT_DIR_REPLY].tuple));
        IP_VS_DBG_BUF(7, "%s: Updating conntrack ct=%p, status=0x%lX, "
                      "ctinfo=%d, new reply=" FMT_TUPLE "\n",
                      __func__, ct, ct->status, ctinfo,
                      ARG_TUPLE(&new_tuple));
        nf_conntrack_alter_reply(ct, &new_tuple);
        IP_VS_DBG_BUF(7, "%s: Updated conntrack ct=%p for cp=" FMT_CONN "\n",
                      __func__, ct, ARG_CONN(cp));
}

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);

        /*
         * 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_ipvs(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 */
                IP_VS_DBG_BUF(7, "%s: for ct=%p, status=0x%lX found inout cp="
                              FMT_CONN "\n",
                              __func__, ct, ct->status, ARG_CONN(cp));
                new_reply = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
                IP_VS_DBG_BUF(7, "%s: ct=%p before alter: reply tuple="
                              FMT_TUPLE "\n",
                              __func__, ct, ARG_TUPLE(&new_reply));
                new_reply.dst.u3 = cp->vaddr;
                new_reply.dst.u.tcp.port = cp->vport;
                goto alter;
        }

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

        IP_VS_DBG_BUF(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)
                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_BUF(7, "%s: ct=%p, expect tuple=" FMT_TUPLE "\n",
                      __func__, ct, ARG_TUPLE(&exp->tuple));
        nf_ct_expect_related(exp, 0);
        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_BUF(7, "%s: dropping conntrack for conn " FMT_CONN "\n",
                      __func__, ARG_CONN(cp));

        h = nf_conntrack_find_get(cp->ipvs->net, &nf_ct_zone_dflt, &tuple);
        if (h) {
                ct = nf_ct_tuplehash_to_ctrack(h);
                if (nf_ct_kill(ct)) {
                        IP_VS_DBG_BUF(7, "%s: ct=%p deleted for tuple="
                                      FMT_TUPLE "\n",
                                      __func__, ct, ARG_TUPLE(&tuple));
                } else {
                        IP_VS_DBG_BUF(7, "%s: ct=%p, no conntrack for tuple="
                                      FMT_TUPLE "\n",
                                      __func__, ct, ARG_TUPLE(&tuple));
                }
                nf_ct_put(ct);
        } else {
                IP_VS_DBG_BUF(7, "%s: no conntrack for tuple=" FMT_TUPLE "\n",
                              __func__, ARG_TUPLE(&tuple));
        }
}