// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * IPVS         An implementation of the IP virtual server support for the
 *              LINUX operating system.  IPVS is now implemented as a module
 *              over the Netfilter framework. IPVS can be used to build a
 *              high-performance and highly available server based on a
 *              cluster of servers.
 *
 * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
 *              Peter Kese <peter.kese@ijs.si>
 *              Julian Anastasov <ja@ssi.bg>
 *
 * The IPVS code for kernel 2.2 was done by Wensong Zhang and Peter Kese,
 * with changes/fixes from Julian Anastasov, Lars Marowsky-Bree, Horms
 * and others.
 *
 * Changes:
 *      Paul `Rusty' Russell            properly handle non-linear skbs
 *      Harald Welte                    don't use nfcache
 */

#define pr_fmt(fmt) "IPVS: " fmt

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/sctp.h>
#include <linux/icmp.h>
#include <linux/slab.h>

#include <net/ip.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/icmp.h>                   /* for icmp_send */
#include <net/gue.h>
#include <net/gre.h>
#include <net/route.h>
#include <net/ip6_checksum.h>
#include <net/netns/generic.h>          /* net_generic() */

#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>

#ifdef CONFIG_IP_VS_IPV6
#include <net/ipv6.h>
#include <linux/netfilter_ipv6.h>
#include <net/ip6_route.h>
#endif

#include <net/ip_vs.h>
#include <linux/indirect_call_wrapper.h>


EXPORT_SYMBOL(register_ip_vs_scheduler);
EXPORT_SYMBOL(unregister_ip_vs_scheduler);
EXPORT_SYMBOL(ip_vs_proto_name);
EXPORT_SYMBOL(ip_vs_conn_new);
EXPORT_SYMBOL(ip_vs_conn_in_get);
EXPORT_SYMBOL(ip_vs_conn_out_get);
#ifdef CONFIG_IP_VS_PROTO_TCP
EXPORT_SYMBOL(ip_vs_tcp_conn_listen);
#endif
EXPORT_SYMBOL(ip_vs_conn_put);
#ifdef CONFIG_IP_VS_DEBUG
EXPORT_SYMBOL(ip_vs_get_debug_level);
#endif
EXPORT_SYMBOL(ip_vs_new_conn_out);

#if defined(CONFIG_IP_VS_PROTO_TCP) && defined(CONFIG_IP_VS_PROTO_UDP)
#define SNAT_CALL(f, ...) \
        INDIRECT_CALL_2(f, tcp_snat_handler, udp_snat_handler, __VA_ARGS__)
#elif defined(CONFIG_IP_VS_PROTO_TCP)
#define SNAT_CALL(f, ...) INDIRECT_CALL_1(f, tcp_snat_handler, __VA_ARGS__)
#elif defined(CONFIG_IP_VS_PROTO_UDP)
#define SNAT_CALL(f, ...) INDIRECT_CALL_1(f, udp_snat_handler, __VA_ARGS__)
#else
#define SNAT_CALL(f, ...) f(__VA_ARGS__)
#endif

static unsigned int ip_vs_net_id __read_mostly;
/* netns cnt used for uniqueness */
static atomic_t ipvs_netns_cnt = ATOMIC_INIT(0);

/* ID used in ICMP lookups */
#define icmp_id(icmph)          (((icmph)->un).echo.id)
#define icmpv6_id(icmph)        (icmph->icmp6_dataun.u_echo.identifier)

const char *ip_vs_proto_name(unsigned int proto)
{
        static char buf[20];

        switch (proto) {
        case IPPROTO_IP:
                return "IP";
        case IPPROTO_UDP:
                return "UDP";
        case IPPROTO_TCP:
                return "TCP";
        case IPPROTO_SCTP:
                return "SCTP";
        case IPPROTO_ICMP:
                return "ICMP";
#ifdef CONFIG_IP_VS_IPV6
        case IPPROTO_ICMPV6:
                return "ICMPv6";
#endif
        default:
                sprintf(buf, "IP_%u", proto);
                return buf;
        }
}

void ip_vs_init_hash_table(struct list_head *table, int rows)
{
        while (--rows >= 0)
                INIT_LIST_HEAD(&table[rows]);
}

static inline void
ip_vs_in_stats(struct ip_vs_conn *cp, struct sk_buff *skb)
{
        struct ip_vs_dest *dest = cp->dest;
        struct netns_ipvs *ipvs = cp->ipvs;

        if (dest && (dest->flags & IP_VS_DEST_F_AVAILABLE)) {
                struct ip_vs_cpu_stats *s;
                struct ip_vs_service *svc;

                local_bh_disable();

                s = this_cpu_ptr(dest->stats.cpustats);
                u64_stats_update_begin(&s->syncp);
                u64_stats_inc(&s->cnt.inpkts);
                u64_stats_add(&s->cnt.inbytes, skb->len);
                u64_stats_update_end(&s->syncp);

                svc = rcu_dereference(dest->svc);
                s = this_cpu_ptr(svc->stats.cpustats);
                u64_stats_update_begin(&s->syncp);
                u64_stats_inc(&s->cnt.inpkts);
                u64_stats_add(&s->cnt.inbytes, skb->len);
                u64_stats_update_end(&s->syncp);

                s = this_cpu_ptr(ipvs->tot_stats->s.cpustats);
                u64_stats_update_begin(&s->syncp);
                u64_stats_inc(&s->cnt.inpkts);
                u64_stats_add(&s->cnt.inbytes, skb->len);
                u64_stats_update_end(&s->syncp);

                local_bh_enable();
        }
}


static inline void
ip_vs_out_stats(struct ip_vs_conn *cp, struct sk_buff *skb)
{
        struct ip_vs_dest *dest = cp->dest;
        struct netns_ipvs *ipvs = cp->ipvs;

        if (dest && (dest->flags & IP_VS_DEST_F_AVAILABLE)) {
                struct ip_vs_cpu_stats *s;
                struct ip_vs_service *svc;

                local_bh_disable();

                s = this_cpu_ptr(dest->stats.cpustats);
                u64_stats_update_begin(&s->syncp);
                u64_stats_inc(&s->cnt.outpkts);
                u64_stats_add(&s->cnt.outbytes, skb->len);
                u64_stats_update_end(&s->syncp);

                svc = rcu_dereference(dest->svc);
                s = this_cpu_ptr(svc->stats.cpustats);
                u64_stats_update_begin(&s->syncp);
                u64_stats_inc(&s->cnt.outpkts);
                u64_stats_add(&s->cnt.outbytes, skb->len);
                u64_stats_update_end(&s->syncp);

                s = this_cpu_ptr(ipvs->tot_stats->s.cpustats);
                u64_stats_update_begin(&s->syncp);
                u64_stats_inc(&s->cnt.outpkts);
                u64_stats_add(&s->cnt.outbytes, skb->len);
                u64_stats_update_end(&s->syncp);

                local_bh_enable();
        }
}


static inline void
ip_vs_conn_stats(struct ip_vs_conn *cp, struct ip_vs_service *svc)
{
        struct netns_ipvs *ipvs = svc->ipvs;
        struct ip_vs_cpu_stats *s;

        local_bh_disable();

        s = this_cpu_ptr(cp->dest->stats.cpustats);
        u64_stats_update_begin(&s->syncp);
        u64_stats_inc(&s->cnt.conns);
        u64_stats_update_end(&s->syncp);

        s = this_cpu_ptr(svc->stats.cpustats);
        u64_stats_update_begin(&s->syncp);
        u64_stats_inc(&s->cnt.conns);
        u64_stats_update_end(&s->syncp);

        s = this_cpu_ptr(ipvs->tot_stats->s.cpustats);
        u64_stats_update_begin(&s->syncp);
        u64_stats_inc(&s->cnt.conns);
        u64_stats_update_end(&s->syncp);

        local_bh_enable();
}


static inline void
ip_vs_set_state(struct ip_vs_conn *cp, int direction,
                const struct sk_buff *skb,
                struct ip_vs_proto_data *pd)
{
        if (likely(pd->pp->state_transition))
                pd->pp->state_transition(cp, direction, skb, pd);
}

static inline int
ip_vs_conn_fill_param_persist(const struct ip_vs_service *svc,
                              struct sk_buff *skb, int protocol,
                              const union nf_inet_addr *caddr, __be16 cport,
                              const union nf_inet_addr *vaddr, __be16 vport,
                              struct ip_vs_conn_param *p)
{
        ip_vs_conn_fill_param(svc->ipvs, svc->af, protocol, caddr, cport, vaddr,
                              vport, p);
        p->pe = rcu_dereference(svc->pe);
        if (p->pe && p->pe->fill_param)
                return p->pe->fill_param(p, skb);

        return 0;
}

/*
 *  IPVS persistent scheduling function
 *  It creates a connection entry according to its template if exists,
 *  or selects a server and creates a connection entry plus a template.
 *  Locking: we are svc user (svc->refcnt), so we hold all dests too
 *  Protocols supported: TCP, UDP
 */
static struct ip_vs_conn *
ip_vs_sched_persist(struct ip_vs_service *svc,
                    struct sk_buff *skb, __be16 src_port, __be16 dst_port,
                    int *ignored, struct ip_vs_iphdr *iph)
{
        struct ip_vs_conn *cp = NULL;
        struct ip_vs_dest *dest;
        struct ip_vs_conn *ct;
        __be16 dport = 0;               /* destination port to forward */
        unsigned int flags;
        struct ip_vs_conn_param param;
        const union nf_inet_addr fwmark = { .ip = htonl(svc->fwmark) };
        union nf_inet_addr snet;        /* source network of the client,
                                           after masking */
        const union nf_inet_addr *src_addr, *dst_addr;

        if (likely(!ip_vs_iph_inverse(iph))) {
                src_addr = &iph->saddr;
                dst_addr = &iph->daddr;
        } else {
                src_addr = &iph->daddr;
                dst_addr = &iph->saddr;
        }


        /* Mask saddr with the netmask to adjust template granularity */
#ifdef CONFIG_IP_VS_IPV6
        if (svc->af == AF_INET6)
                ipv6_addr_prefix(&snet.in6, &src_addr->in6,
                                 (__force __u32) svc->netmask);
        else
#endif
                snet.ip = src_addr->ip & svc->netmask;

        IP_VS_DBG_BUF(6, "p-schedule: src %s:%u dest %s:%u "
                      "mnet %s\n",
                      IP_VS_DBG_ADDR(svc->af, src_addr), ntohs(src_port),
                      IP_VS_DBG_ADDR(svc->af, dst_addr), ntohs(dst_port),
                      IP_VS_DBG_ADDR(svc->af, &snet));

        /*
         * As far as we know, FTP is a very complicated network protocol, and
         * it uses control connection and data connections. For active FTP,
         * FTP server initialize data connection to the client, its source port
         * is often 20. For passive FTP, FTP server tells the clients the port
         * that it passively listens to,  and the client issues the data
         * connection. In the tunneling or direct routing mode, the load
         * balancer is on the client-to-server half of connection, the port
         * number is unknown to the load balancer. So, a conn template like
         * <caddr, 0, vaddr, 0, daddr, 0> is created for persistent FTP
         * service, and a template like <caddr, 0, vaddr, vport, daddr, dport>
         * is created for other persistent services.
         */
        {
                int protocol = iph->protocol;
                const union nf_inet_addr *vaddr = dst_addr;
                __be16 vport = 0;

                if (dst_port == svc->port) {
                        /* non-FTP template:
                         * <protocol, caddr, 0, vaddr, vport, daddr, dport>
                         * FTP template:
                         * <protocol, caddr, 0, vaddr, 0, daddr, 0>
                         */
                        if (svc->port != FTPPORT)
                                vport = dst_port;
                } else {
                        /* Note: persistent fwmark-based services and
                         * persistent port zero service are handled here.
                         * fwmark template:
                         * <IPPROTO_IP,caddr,0,fwmark,0,daddr,0>
                         * port zero template:
                         * <protocol,caddr,0,vaddr,0,daddr,0>
                         */
                        if (svc->fwmark) {
                                protocol = IPPROTO_IP;
                                vaddr = &fwmark;
                        }
                }
                /* return *ignored = -1 so NF_DROP can be used */
                if (ip_vs_conn_fill_param_persist(svc, skb, protocol, &snet, 0,
                                                  vaddr, vport, &param) < 0) {
                        *ignored = -1;
                        return NULL;
                }
        }

        /* Check if a template already exists */
        ct = ip_vs_ct_in_get(&param);
        if (!ct || !ip_vs_check_template(ct, NULL)) {
                struct ip_vs_scheduler *sched;

                /*
                 * No template found or the dest of the connection
                 * template is not available.
                 * return *ignored=0 i.e. ICMP and NF_DROP
                 */
                sched = rcu_dereference(svc->scheduler);
                if (sched) {
                        /* read svc->sched_data after svc->scheduler */
                        smp_rmb();
                        dest = sched->schedule(svc, skb, iph);
                } else {
                        dest = NULL;
                }
                if (!dest) {
                        IP_VS_DBG(1, "p-schedule: no dest found.\n");
                        kfree(param.pe_data);
                        *ignored = 0;
                        return NULL;
                }

                if (dst_port == svc->port && svc->port != FTPPORT)
                        dport = dest->port;

                /* Create a template
                 * This adds param.pe_data to the template,
                 * and thus param.pe_data will be destroyed
                 * when the template expires */
                ct = ip_vs_conn_new(&param, dest->af, &dest->addr, dport,
                                    IP_VS_CONN_F_TEMPLATE, dest, skb->mark);
                if (ct == NULL) {
                        kfree(param.pe_data);
                        *ignored = -1;
                        return NULL;
                }

                ct->timeout = svc->timeout;
        } else {
                /* set destination with the found template */
                dest = ct->dest;
                kfree(param.pe_data);
        }

        dport = dst_port;
        if (dport == svc->port && dest->port)
                dport = dest->port;

        flags = (svc->flags & IP_VS_SVC_F_ONEPACKET
                 && iph->protocol == IPPROTO_UDP) ?
                IP_VS_CONN_F_ONE_PACKET : 0;

        /*
         *    Create a new connection according to the template
         */
        ip_vs_conn_fill_param(svc->ipvs, svc->af, iph->protocol, src_addr,
                              src_port, dst_addr, dst_port, &param);

        cp = ip_vs_conn_new(&param, dest->af, &dest->addr, dport, flags, dest,
                            skb->mark);
        if (cp == NULL) {
                ip_vs_conn_put(ct);
                *ignored = -1;
                return NULL;
        }

        /*
         *    Add its control
         */
        ip_vs_control_add(cp, ct);
        ip_vs_conn_put(ct);

        ip_vs_conn_stats(cp, svc);
        return cp;
}


/*
 *  IPVS main scheduling function
 *  It selects a server according to the virtual service, and
 *  creates a connection entry.
 *  Protocols supported: TCP, UDP
 *
 *  Usage of *ignored
 *
 * 1 :   protocol tried to schedule (eg. on SYN), found svc but the
 *       svc/scheduler decides that this packet should be accepted with
 *       NF_ACCEPT because it must not be scheduled.
 *
 * 0 :   scheduler can not find destination, so try bypass or
 *       return ICMP and then NF_DROP (ip_vs_leave).
 *
 * -1 :  scheduler tried to schedule but fatal error occurred, eg.
 *       ip_vs_conn_new failure (ENOMEM) or ip_vs_sip_fill_param
 *       failure such as missing Call-ID, ENOMEM on skb_linearize
 *       or pe_data. In this case we should return NF_DROP without
 *       any attempts to send ICMP with ip_vs_leave.
 */
struct ip_vs_conn *
ip_vs_schedule(struct ip_vs_service *svc, struct sk_buff *skb,
               struct ip_vs_proto_data *pd, int *ignored,
               struct ip_vs_iphdr *iph)
{
        struct ip_vs_protocol *pp = pd->pp;
        struct ip_vs_conn *cp = NULL;
        struct ip_vs_scheduler *sched;
        struct ip_vs_dest *dest;
        __be16 _ports[2], *pptr, cport, vport;
        const void *caddr, *vaddr;
        unsigned int flags;

        *ignored = 1;
        /*
         * IPv6 frags, only the first hit here.
         */
        pptr = frag_safe_skb_hp(skb, iph->len, sizeof(_ports), _ports);
        if (pptr == NULL)
                return NULL;

        if (likely(!ip_vs_iph_inverse(iph))) {
                cport = pptr[0];
                caddr = &iph->saddr;
                vport = pptr[1];
                vaddr = &iph->daddr;
        } else {
                cport = pptr[1];
                caddr = &iph->daddr;
                vport = pptr[0];
                vaddr = &iph->saddr;
        }

        /*
         * FTPDATA needs this check when using local real server.
         * Never schedule Active FTPDATA connections from real server.
         * For LVS-NAT they must be already created. For other methods
         * with persistence the connection is created on SYN+ACK.
         */
        if (cport == FTPDATA) {
                IP_VS_DBG_PKT(12, svc->af, pp, skb, iph->off,
                              "Not scheduling FTPDATA");
                return NULL;
        }

        /*
         *    Do not schedule replies from local real server.
         */
        if ((!skb->dev || skb->dev->flags & IFF_LOOPBACK)) {
                iph->hdr_flags ^= IP_VS_HDR_INVERSE;
                cp = INDIRECT_CALL_1(pp->conn_in_get,
                                     ip_vs_conn_in_get_proto, svc->ipvs,
                                     svc->af, skb, iph);
                iph->hdr_flags ^= IP_VS_HDR_INVERSE;

                if (cp) {
                        IP_VS_DBG_PKT(12, svc->af, pp, skb, iph->off,
                                      "Not scheduling reply for existing"
                                      " connection");
                        __ip_vs_conn_put(cp);
                        return NULL;
                }
        }

        /*
         *    Persistent service
         */
        if (svc->flags & IP_VS_SVC_F_PERSISTENT)
                return ip_vs_sched_persist(svc, skb, cport, vport, ignored,
                                           iph);

        *ignored = 0;

        /*
         *    Non-persistent service
         */
        if (!svc->fwmark && vport != svc->port) {
                if (!svc->port)
                        pr_err("Schedule: port zero only supported "
                               "in persistent services, "
                               "check your ipvs configuration\n");
                return NULL;
        }

        sched = rcu_dereference(svc->scheduler);
        if (sched) {
                /* read svc->sched_data after svc->scheduler */
                smp_rmb();
                dest = sched->schedule(svc, skb, iph);
        } else {
                dest = NULL;
        }
        if (dest == NULL) {
                IP_VS_DBG(1, "Schedule: no dest found.\n");
                return NULL;
        }

        flags = (svc->flags & IP_VS_SVC_F_ONEPACKET
                 && iph->protocol == IPPROTO_UDP) ?
                IP_VS_CONN_F_ONE_PACKET : 0;

        /*
         *    Create a connection entry.
         */
        {
                struct ip_vs_conn_param p;

                ip_vs_conn_fill_param(svc->ipvs, svc->af, iph->protocol,
                                      caddr, cport, vaddr, vport, &p);
                cp = ip_vs_conn_new(&p, dest->af, &dest->addr,
                                    dest->port ? dest->port : vport,
                                    flags, dest, skb->mark);
                if (!cp) {
                        *ignored = -1;
                        return NULL;
                }
        }

        IP_VS_DBG_BUF(6, "Schedule fwd:%c c:%s:%u v:%s:%u "
                      "d:%s:%u conn->flags:%X conn->refcnt:%d\n",
                      ip_vs_fwd_tag(cp),
                      IP_VS_DBG_ADDR(cp->af, &cp->caddr), ntohs(cp->cport),
                      IP_VS_DBG_ADDR(cp->af, &cp->vaddr), ntohs(cp->vport),
                      IP_VS_DBG_ADDR(cp->daf, &cp->daddr), ntohs(cp->dport),
                      cp->flags, refcount_read(&cp->refcnt));

        ip_vs_conn_stats(cp, svc);
        return cp;
}

static inline int ip_vs_addr_is_unicast(struct net *net, int af,
                                        union nf_inet_addr *addr)
{
#ifdef CONFIG_IP_VS_IPV6
        if (af == AF_INET6)
                return ipv6_addr_type(&addr->in6) & IPV6_ADDR_UNICAST;
#endif
        return (inet_addr_type(net, addr->ip) == RTN_UNICAST);
}

/*
 *  Pass or drop the packet.
 *  Called by ip_vs_in, when the virtual service is available but
 *  no destination is available for a new connection.
 */
int ip_vs_leave(struct ip_vs_service *svc, struct sk_buff *skb,
                struct ip_vs_proto_data *pd, struct ip_vs_iphdr *iph)
{
        __be16 _ports[2], *pptr, dport;
        struct netns_ipvs *ipvs = svc->ipvs;
        struct net *net = ipvs->net;

        pptr = frag_safe_skb_hp(skb, iph->len, sizeof(_ports), _ports);
        if (!pptr)
                return NF_DROP;
        dport = likely(!ip_vs_iph_inverse(iph)) ? pptr[1] : pptr[0];

        /* if it is fwmark-based service, the cache_bypass sysctl is up
           and the destination is a non-local unicast, then create
           a cache_bypass connection entry */
        if (sysctl_cache_bypass(ipvs) && svc->fwmark &&
            !(iph->hdr_flags & (IP_VS_HDR_INVERSE | IP_VS_HDR_ICMP)) &&
            ip_vs_addr_is_unicast(net, svc->af, &iph->daddr)) {
                int ret;
                struct ip_vs_conn *cp;
                unsigned int flags = (svc->flags & IP_VS_SVC_F_ONEPACKET &&
                                      iph->protocol == IPPROTO_UDP) ?
                                      IP_VS_CONN_F_ONE_PACKET : 0;
                union nf_inet_addr daddr = { .all = { 0, 0, 0, 0 } };

                /* create a new connection entry */
                IP_VS_DBG(6, "%s(): create a cache_bypass entry\n", __func__);
                {
                        struct ip_vs_conn_param p;
                        ip_vs_conn_fill_param(svc->ipvs, svc->af, iph->protocol,
                                              &iph->saddr, pptr[0],
                                              &iph->daddr, pptr[1], &p);
                        cp = ip_vs_conn_new(&p, svc->af, &daddr, 0,
                                            IP_VS_CONN_F_BYPASS | flags,
                                            NULL, skb->mark);
                        if (!cp)
                                return NF_DROP;
                }

                /* statistics */
                ip_vs_in_stats(cp, skb);

                /* set state */
                ip_vs_set_state(cp, IP_VS_DIR_INPUT, skb, pd);

                /* transmit the first SYN packet */
                ret = cp->packet_xmit(skb, cp, pd->pp, iph);
                /* do not touch skb anymore */

                if ((cp->flags & IP_VS_CONN_F_ONE_PACKET) && cp->control)
                        atomic_inc(&cp->control->in_pkts);
                else
                        atomic_inc(&cp->in_pkts);
                ip_vs_conn_put(cp);
                return ret;
        }

        /*
         * When the virtual ftp service is presented, packets destined
         * for other services on the VIP may get here (except services
         * listed in the ipvs table), pass the packets, because it is
         * not ipvs job to decide to drop the packets.
         */
        if (svc->port == FTPPORT && dport != FTPPORT)
                return NF_ACCEPT;

        if (unlikely(ip_vs_iph_icmp(iph)))
                return NF_DROP;

        /*
         * Notify the client that the destination is unreachable, and
         * release the socket buffer.
         * Since it is in IP layer, the TCP socket is not actually
         * created, the TCP RST packet cannot be sent, instead that
         * ICMP_PORT_UNREACH is sent here no matter it is TCP/UDP. --WZ
         */
#ifdef CONFIG_IP_VS_IPV6
        if (svc->af == AF_INET6) {
                if (!skb->dev)
                        skb->dev = net->loopback_dev;
                icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_PORT_UNREACH, 0);
        } else
#endif
                icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);

        return NF_DROP;
}

#ifdef CONFIG_SYSCTL

static int sysctl_snat_reroute(struct netns_ipvs *ipvs)
{
        return ipvs->sysctl_snat_reroute;
}

static int sysctl_nat_icmp_send(struct netns_ipvs *ipvs)
{
        return ipvs->sysctl_nat_icmp_send;
}

#else

static int sysctl_snat_reroute(struct netns_ipvs *ipvs) { return 0; }
static int sysctl_nat_icmp_send(struct netns_ipvs *ipvs) { return 0; }

#endif

__sum16 ip_vs_checksum_complete(struct sk_buff *skb, int offset)
{
        return csum_fold(skb_checksum(skb, offset, skb->len - offset, 0));
}

static inline enum ip_defrag_users ip_vs_defrag_user(unsigned int hooknum)
{
        if (NF_INET_LOCAL_IN == hooknum)
                return IP_DEFRAG_VS_IN;
        if (NF_INET_FORWARD == hooknum)
                return IP_DEFRAG_VS_FWD;
        return IP_DEFRAG_VS_OUT;
}

static inline int ip_vs_gather_frags(struct netns_ipvs *ipvs,
                                     struct sk_buff *skb, u_int32_t user)
{
        int err;

        local_bh_disable();
        err = ip_defrag(ipvs->net, skb, user);
        local_bh_enable();
        if (!err)
                ip_send_check(ip_hdr(skb));

        return err;
}

static int ip_vs_route_me_harder(struct netns_ipvs *ipvs, int af,
                                 struct sk_buff *skb, unsigned int hooknum)
{
        if (!sysctl_snat_reroute(ipvs))
                return 0;
        /* Reroute replies only to remote clients (FORWARD and LOCAL_OUT) */
        if (NF_INET_LOCAL_IN == hooknum)
                return 0;
#ifdef CONFIG_IP_VS_IPV6
        if (af == AF_INET6) {
                struct dst_entry *dst = skb_dst(skb);

                if (dst->dev && !(dst->dev->flags & IFF_LOOPBACK) &&
                    ip6_route_me_harder(ipvs->net, skb->sk, skb) != 0)
                        return 1;
        } else
#endif
                if (!(skb_rtable(skb)->rt_flags & RTCF_LOCAL) &&
                    ip_route_me_harder(ipvs->net, skb->sk, skb, RTN_LOCAL) != 0)
                        return 1;

        return 0;
}

/*
 * Packet has been made sufficiently writable in caller
 * - inout: 1=in->out, 0=out->in
 */
void ip_vs_nat_icmp(struct sk_buff *skb, struct ip_vs_protocol *pp,
                    struct ip_vs_conn *cp, int inout)
{
        struct iphdr *iph        = ip_hdr(skb);
        unsigned int icmp_offset = iph->ihl*4;
        struct icmphdr *icmph    = (struct icmphdr *)(skb_network_header(skb) +
                                                      icmp_offset);
        struct iphdr *ciph       = (struct iphdr *)(icmph + 1);

        if (inout) {
                iph->saddr = cp->vaddr.ip;
                ip_send_check(iph);
                ciph->daddr = cp->vaddr.ip;
                ip_send_check(ciph);
        } else {
                iph->daddr = cp->daddr.ip;
                ip_send_check(iph);
                ciph->saddr = cp->daddr.ip;
                ip_send_check(ciph);
        }

        /* the TCP/UDP/SCTP port */
        if (IPPROTO_TCP == ciph->protocol || IPPROTO_UDP == ciph->protocol ||
            IPPROTO_SCTP == ciph->protocol) {
                __be16 *ports = (void *)ciph + ciph->ihl*4;

                if (inout)
                        ports[1] = cp->vport;
                else
                        ports[0] = cp->dport;
        }

        /* And finally the ICMP checksum */
        icmph->checksum = 0;
        icmph->checksum = ip_vs_checksum_complete(skb, icmp_offset);
        skb->ip_summed = CHECKSUM_UNNECESSARY;

        if (inout)
                IP_VS_DBG_PKT(11, AF_INET, pp, skb, (void *)ciph - (void *)iph,
                        "Forwarding altered outgoing ICMP");
        else
                IP_VS_DBG_PKT(11, AF_INET, pp, skb, (void *)ciph - (void *)iph,
                        "Forwarding altered incoming ICMP");
}

#ifdef CONFIG_IP_VS_IPV6
void ip_vs_nat_icmp_v6(struct sk_buff *skb, struct ip_vs_protocol *pp,
                    struct ip_vs_conn *cp, int inout)
{
        struct ipv6hdr *iph      = ipv6_hdr(skb);
        unsigned int icmp_offset = 0;
        unsigned int offs        = 0; /* header offset*/
        int protocol;
        struct icmp6hdr *icmph;
        struct ipv6hdr *ciph;
        unsigned short fragoffs;

        ipv6_find_hdr(skb, &icmp_offset, IPPROTO_ICMPV6, &fragoffs, NULL);
        icmph = (struct icmp6hdr *)(skb_network_header(skb) + icmp_offset);
        offs = icmp_offset + sizeof(struct icmp6hdr);
        ciph = (struct ipv6hdr *)(skb_network_header(skb) + offs);

        protocol = ipv6_find_hdr(skb, &offs, -1, &fragoffs, NULL);

        if (inout) {
                iph->saddr = cp->vaddr.in6;
                ciph->daddr = cp->vaddr.in6;
        } else {
                iph->daddr = cp->daddr.in6;
                ciph->saddr = cp->daddr.in6;
        }

        /* the TCP/UDP/SCTP port */
        if (!fragoffs && (IPPROTO_TCP == protocol || IPPROTO_UDP == protocol ||
                          IPPROTO_SCTP == protocol)) {
                __be16 *ports = (void *)(skb_network_header(skb) + offs);

                IP_VS_DBG(11, "%s() changed port %d to %d\n", __func__,
                              ntohs(inout ? ports[1] : ports[0]),
                              ntohs(inout ? cp->vport : cp->dport));
                if (inout)
                        ports[1] = cp->vport;
                else
                        ports[0] = cp->dport;
        }

        /* And finally the ICMP checksum */
        icmph->icmp6_cksum = ~csum_ipv6_magic(&iph->saddr, &iph->daddr,
                                              skb->len - icmp_offset,
                                              IPPROTO_ICMPV6, 0);
        skb->csum_start = skb_network_header(skb) - skb->head + icmp_offset;
        skb->csum_offset = offsetof(struct icmp6hdr, icmp6_cksum);
        skb->ip_summed = CHECKSUM_PARTIAL;

        if (inout)
                IP_VS_DBG_PKT(11, AF_INET6, pp, skb,
                              (void *)ciph - (void *)iph,
                              "Forwarding altered outgoing ICMPv6");
        else
                IP_VS_DBG_PKT(11, AF_INET6, pp, skb,
                              (void *)ciph - (void *)iph,
                              "Forwarding altered incoming ICMPv6");
}
#endif

/* Handle relevant response ICMP messages - forward to the right
 * destination host.
 */
static int handle_response_icmp(int af, struct sk_buff *skb,
                                union nf_inet_addr *snet,
                                __u8 protocol, struct ip_vs_conn *cp,
                                struct ip_vs_protocol *pp,
                                unsigned int offset, unsigned int ihl,
                                unsigned int hooknum)
{
        unsigned int verdict = NF_DROP;

        if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ)
                goto after_nat;

        /* Ensure the checksum is correct */
        if (!skb_csum_unnecessary(skb) && ip_vs_checksum_complete(skb, ihl)) {
                /* Failed checksum! */
                IP_VS_DBG_BUF(1, "Forward ICMP: failed checksum from %s!\n",
                              IP_VS_DBG_ADDR(af, snet));
                goto out;
        }

        if (IPPROTO_TCP == protocol || IPPROTO_UDP == protocol ||
            IPPROTO_SCTP == protocol)
                offset += 2 * sizeof(__u16);
        if (skb_ensure_writable(skb, offset))
                goto out;

#ifdef CONFIG_IP_VS_IPV6
        if (af == AF_INET6)
                ip_vs_nat_icmp_v6(skb, pp, cp, 1);
        else
#endif
                ip_vs_nat_icmp(skb, pp, cp, 1);

        if (ip_vs_route_me_harder(cp->ipvs, af, skb, hooknum))
                goto out;

after_nat:
        /* do the statistics and put it back */
        ip_vs_out_stats(cp, skb);

        skb->ipvs_property = 1;
        if (!(cp->flags & IP_VS_CONN_F_NFCT))
                ip_vs_notrack(skb);
        else
                ip_vs_update_conntrack(skb, cp, 0);
        verdict = NF_ACCEPT;

out:
        __ip_vs_conn_put(cp);

        return verdict;
}

/*
 *      Handle ICMP messages in the inside-to-outside direction (outgoing).
 *      Find any that might be relevant, check against existing connections.
 *      Currently handles error types - unreachable, quench, ttl exceeded.
 */
static int ip_vs_out_icmp(struct netns_ipvs *ipvs, struct sk_buff *skb,
                          int *related, unsigned int hooknum)
{
        struct iphdr *iph;
        struct icmphdr  _icmph, *ic;
        struct iphdr    _ciph, *cih;    /* The ip header contained within the ICMP */
        struct ip_vs_iphdr ciph;
        struct ip_vs_conn *cp;
        struct ip_vs_protocol *pp;
        unsigned int offset, ihl;
        union nf_inet_addr snet;

        *related = 1;

        /* reassemble IP fragments */
        if (ip_is_fragment(ip_hdr(skb))) {
                if (ip_vs_gather_frags(ipvs, skb, ip_vs_defrag_user(hooknum)))
                        return NF_STOLEN;
        }

        iph = ip_hdr(skb);
        offset = ihl = iph->ihl * 4;
        ic = skb_header_pointer(skb, offset, sizeof(_icmph), &_icmph);
        if (ic == NULL)
                return NF_DROP;

        IP_VS_DBG(12, "Outgoing ICMP (%d,%d) %pI4->%pI4\n",
                  ic->type, ntohs(icmp_id(ic)),
                  &iph->saddr, &iph->daddr);

        /*
         * Work through seeing if this is for us.
         * These checks are supposed to be in an order that means easy
         * things are checked first to speed up processing.... however
         * this means that some packets will manage to get a long way
         * down this stack and then be rejected, but that's life.
         */
        if ((ic->type != ICMP_DEST_UNREACH) &&
            (ic->type != ICMP_SOURCE_QUENCH) &&
            (ic->type != ICMP_TIME_EXCEEDED)) {
                *related = 0;
                return NF_ACCEPT;
        }

        /* Now find the contained IP header */
        offset += sizeof(_icmph);
        cih = skb_header_pointer(skb, offset, sizeof(_ciph), &_ciph);
        if (cih == NULL)
                return NF_ACCEPT; /* The packet looks wrong, ignore */

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

        /* Is the embedded protocol header present? */
        if (unlikely(cih->frag_off & htons(IP_OFFSET) &&
                     pp->dont_defrag))
                return NF_ACCEPT;

        IP_VS_DBG_PKT(11, AF_INET, pp, skb, offset,
                      "Checking outgoing ICMP for");

        ip_vs_fill_iph_skb_icmp(AF_INET, skb, offset, true, &ciph);

        /* The embedded headers contain source and dest in reverse order */
        cp = INDIRECT_CALL_1(pp->conn_out_get, ip_vs_conn_out_get_proto,
                             ipvs, AF_INET, skb, &ciph);
        if (!cp)
                return NF_ACCEPT;

        snet.ip = iph->saddr;
        return handle_response_icmp(AF_INET, skb, &snet, cih->protocol, cp,
                                    pp, ciph.len, ihl, hooknum);
}

#ifdef CONFIG_IP_VS_IPV6
static int ip_vs_out_icmp_v6(struct netns_ipvs *ipvs, struct sk_buff *skb,
                             int *related,  unsigned int hooknum,
                             struct ip_vs_iphdr *ipvsh)
{
        struct icmp6hdr _icmph, *ic;
        struct ip_vs_iphdr ciph = {.flags = 0, .fragoffs = 0};/*Contained IP */
        struct ip_vs_conn *cp;
        struct ip_vs_protocol *pp;
        union nf_inet_addr snet;
        unsigned int offset;

        *related = 1;
        ic = frag_safe_skb_hp(skb, ipvsh->len, sizeof(_icmph), &_icmph);
        if (ic == NULL)
                return NF_DROP;

        /*
         * Work through seeing if this is for us.
         * These checks are supposed to be in an order that means easy
         * things are checked first to speed up processing.... however
         * this means that some packets will manage to get a long way
         * down this stack and then be rejected, but that's life.
         */
        if (ic->icmp6_type & ICMPV6_INFOMSG_MASK) {
                *related = 0;
                return NF_ACCEPT;
        }
        /* Fragment header that is before ICMP header tells us that:
         * it's not an error message since they can't be fragmented.
         */
        if (ipvsh->flags & IP6_FH_F_FRAG)
                return NF_DROP;

        IP_VS_DBG(8, "Outgoing ICMPv6 (%d,%d) %pI6c->%pI6c\n",
                  ic->icmp6_type, ntohs(icmpv6_id(ic)),
                  &ipvsh->saddr, &ipvsh->daddr);

        if (!ip_vs_fill_iph_skb_icmp(AF_INET6, skb, ipvsh->len + sizeof(_icmph),
                                     true, &ciph))
                return NF_ACCEPT; /* The packet looks wrong, ignore */

        pp = ip_vs_proto_get(ciph.protocol);
        if (!pp)
                return NF_ACCEPT;

        /* The embedded headers contain source and dest in reverse order */
        cp = INDIRECT_CALL_1(pp->conn_out_get, ip_vs_conn_out_get_proto,
                             ipvs, AF_INET6, skb, &ciph);
        if (!cp)
                return NF_ACCEPT;

        snet.in6 = ciph.saddr.in6;
        offset = ciph.len;
        return handle_response_icmp(AF_INET6, skb, &snet, ciph.protocol, cp,
                                    pp, offset, sizeof(struct ipv6hdr),
                                    hooknum);
}
#endif

/*
 * Check if sctp chunc is ABORT chunk
 */
static inline int is_sctp_abort(const struct sk_buff *skb, int nh_len)
{
        struct sctp_chunkhdr *sch, schunk;
        sch = skb_header_pointer(skb, nh_len + sizeof(struct sctphdr),
                                 sizeof(schunk), &schunk);
        if (sch == NULL)
                return 0;
        if (sch->type == SCTP_CID_ABORT)
                return 1;
        return 0;
}

static inline int is_tcp_reset(const struct sk_buff *skb, int nh_len)
{
        struct tcphdr _tcph, *th;

        th = skb_header_pointer(skb, nh_len, sizeof(_tcph), &_tcph);
        if (th == NULL)
                return 0;
        return th->rst;
}

static inline bool is_new_conn(const struct sk_buff *skb,
                               struct ip_vs_iphdr *iph)
{
        switch (iph->protocol) {
        case IPPROTO_TCP: {
                struct tcphdr _tcph, *th;

                th = skb_header_pointer(skb, iph->len, sizeof(_tcph), &_tcph);
                if (th == NULL)
                        return false;
                return th->syn;
        }
        case IPPROTO_SCTP: {
                struct sctp_chunkhdr *sch, schunk;

                sch = skb_header_pointer(skb, iph->len + sizeof(struct sctphdr),
                                         sizeof(schunk), &schunk);
                if (sch == NULL)
                        return false;
                return sch->type == SCTP_CID_INIT;
        }
        default:
                return false;
        }
}

static inline bool is_new_conn_expected(const struct ip_vs_conn *cp,
                                        int conn_reuse_mode)
{
        /* Controlled (FTP DATA or persistence)? */
        if (cp->control)
                return false;

        switch (cp->protocol) {
        case IPPROTO_TCP:
                return (cp->state == IP_VS_TCP_S_TIME_WAIT) ||
                       (cp->state == IP_VS_TCP_S_CLOSE) ||
                        ((conn_reuse_mode & 2) &&
                         (cp->state == IP_VS_TCP_S_FIN_WAIT) &&
                         (cp->flags & IP_VS_CONN_F_NOOUTPUT));
        case IPPROTO_SCTP:
                return cp->state == IP_VS_SCTP_S_CLOSED;
        default:
                return false;
        }
}

/* Generic function to create new connections for outgoing RS packets
 *
 * Pre-requisites for successful connection creation:
 * 1) Virtual Service is NOT fwmark based:
 *    In fwmark-VS actual vaddr and vport are unknown to IPVS
 * 2) Real Server and Virtual Service were NOT configured without port:
 *    This is to allow match of different VS to the same RS ip-addr
 */
struct ip_vs_conn *ip_vs_new_conn_out(struct ip_vs_service *svc,
                                      struct ip_vs_dest *dest,
                                      struct sk_buff *skb,
                                      const struct ip_vs_iphdr *iph,
                                      __be16 dport,
                                      __be16 cport)
{
        struct ip_vs_conn_param param;
        struct ip_vs_conn *ct = NULL, *cp = NULL;
        const union nf_inet_addr *vaddr, *daddr, *caddr;
        union nf_inet_addr snet;
        __be16 vport;
        unsigned int flags;

        vaddr = &svc->addr;
        vport = svc->port;
        daddr = &iph->saddr;
        caddr = &iph->daddr;

        /* check pre-requisites are satisfied */
        if (svc->fwmark)
                return NULL;
        if (!vport || !dport)
                return NULL;

        /* for persistent service first create connection template */
        if (svc->flags & IP_VS_SVC_F_PERSISTENT) {
                /* apply netmask the same way ingress-side does */
#ifdef CONFIG_IP_VS_IPV6
                if (svc->af == AF_INET6)
                        ipv6_addr_prefix(&snet.in6, &caddr->in6,
                                         (__force __u32)svc->netmask);
                else
#endif
                        snet.ip = caddr->ip & svc->netmask;
                /* fill params and create template if not existent */
                if (ip_vs_conn_fill_param_persist(svc, skb, iph->protocol,
                                                  &snet, 0, vaddr,
                                                  vport, &param) < 0)
                        return NULL;
                ct = ip_vs_ct_in_get(&param);
                /* check if template exists and points to the same dest */
                if (!ct || !ip_vs_check_template(ct, dest)) {
                        ct = ip_vs_conn_new(&param, dest->af, daddr, dport,
                                            IP_VS_CONN_F_TEMPLATE, dest, 0);
                        if (!ct) {
                                kfree(param.pe_data);
                                return NULL;
                        }
                        ct->timeout = svc->timeout;
                } else {
                        kfree(param.pe_data);
                }
        }

        /* connection flags */
        flags = ((svc->flags & IP_VS_SVC_F_ONEPACKET) &&
                 iph->protocol == IPPROTO_UDP) ? IP_VS_CONN_F_ONE_PACKET : 0;
        /* create connection */
        ip_vs_conn_fill_param(svc->ipvs, svc->af, iph->protocol,
                              caddr, cport, vaddr, vport, &param);
        cp = ip_vs_conn_new(&param, dest->af, daddr, dport, flags, dest, 0);
        if (!cp) {
                if (ct)
                        ip_vs_conn_put(ct);
                return NULL;
        }
        if (ct) {
                ip_vs_control_add(cp, ct);
                ip_vs_conn_put(ct);
        }
        ip_vs_conn_stats(cp, svc);

        /* return connection (will be used to handle outgoing packet) */
        IP_VS_DBG_BUF(6, "New connection RS-initiated:%c c:%s:%u v:%s:%u "
                      "d:%s:%u conn->flags:%X conn->refcnt:%d\n",
                      ip_vs_fwd_tag(cp),
                      IP_VS_DBG_ADDR(cp->af, &cp->caddr), ntohs(cp->cport),
                      IP_VS_DBG_ADDR(cp->af, &cp->vaddr), ntohs(cp->vport),
                      IP_VS_DBG_ADDR(cp->af, &cp->daddr), ntohs(cp->dport),
                      cp->flags, refcount_read(&cp->refcnt));
        return cp;
}

/* Handle outgoing packets which are considered requests initiated by
 * real servers, so that subsequent responses from external client can be
 * routed to the right real server.
 * Used also for outgoing responses in OPS mode.
 *
 * Connection management is handled by persistent-engine specific callback.
 */
static struct ip_vs_conn *__ip_vs_rs_conn_out(unsigned int hooknum,
                                              struct netns_ipvs *ipvs,
                                              int af, struct sk_buff *skb,
                                              const struct ip_vs_iphdr *iph)
{
        struct ip_vs_dest *dest;
        struct ip_vs_conn *cp = NULL;
        __be16 _ports[2], *pptr;

        if (hooknum == NF_INET_LOCAL_IN)
                return NULL;

        pptr = frag_safe_skb_hp(skb, iph->len,
                                sizeof(_ports), _ports);
        if (!pptr)
                return NULL;

        dest = ip_vs_find_real_service(ipvs, af, iph->protocol,
                                       &iph->saddr, pptr[0]);
        if (dest) {
                struct ip_vs_service *svc;
                struct ip_vs_pe *pe;

                svc = rcu_dereference(dest->svc);
                if (svc) {
                        pe = rcu_dereference(svc->pe);
                        if (pe && pe->conn_out)
                                cp = pe->conn_out(svc, dest, skb, iph,
                                                  pptr[0], pptr[1]);
                }
        }

        return cp;
}

/* Handle response packets: rewrite addresses and send away...
 */
static unsigned int
handle_response(int af, struct sk_buff *skb, struct ip_vs_proto_data *pd,
                struct ip_vs_conn *cp, struct ip_vs_iphdr *iph,
                unsigned int hooknum)
{
        struct ip_vs_protocol *pp = pd->pp;

        if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ)
                goto after_nat;

        IP_VS_DBG_PKT(11, af, pp, skb, iph->off, "Outgoing packet");

        if (skb_ensure_writable(skb, iph->len))
                goto drop;

        /* mangle the packet */
        if (pp->snat_handler &&
            !SNAT_CALL(pp->snat_handler, skb, pp, cp, iph))
                goto drop;

#ifdef CONFIG_IP_VS_IPV6
        if (af == AF_INET6)
                ipv6_hdr(skb)->saddr = cp->vaddr.in6;
        else
#endif
        {
                ip_hdr(skb)->saddr = cp->vaddr.ip;
                ip_send_check(ip_hdr(skb));
        }

        /*
         * nf_iterate does not expect change in the skb->dst->dev.
         * It looks like it is not fatal to enable this code for hooks
         * where our handlers are at the end of the chain list and
         * when all next handlers use skb->dst->dev and not outdev.
         * It will definitely route properly the inout NAT traffic
         * when multiple paths are used.
         */

        /* For policy routing, packets originating from this
         * machine itself may be routed differently to packets
         * passing through.  We want this packet to be routed as
         * if it came from this machine itself.  So re-compute
         * the routing information.
         */
        if (ip_vs_route_me_harder(cp->ipvs, af, skb, hooknum))
                goto drop;

        IP_VS_DBG_PKT(10, af, pp, skb, iph->off, "After SNAT");

after_nat:
        ip_vs_out_stats(cp, skb);
        ip_vs_set_state(cp, IP_VS_DIR_OUTPUT, skb, pd);
        skb->ipvs_property = 1;
        if (!(cp->flags & IP_VS_CONN_F_NFCT))
                ip_vs_notrack(skb);
        else
                ip_vs_update_conntrack(skb, cp, 0);
        ip_vs_conn_put(cp);

        return NF_ACCEPT;

drop:
        ip_vs_conn_put(cp);
        kfree_skb(skb);
        return NF_STOLEN;
}

/*
 *      Check if outgoing packet belongs to the established ip_vs_conn.
 */
static unsigned int
ip_vs_out_hook(void *priv, struct sk_buff *skb, const struct nf_hook_state *state)
{
        struct netns_ipvs *ipvs = net_ipvs(state->net);
        unsigned int hooknum = state->hook;
        struct ip_vs_iphdr iph;
        struct ip_vs_protocol *pp;
        struct ip_vs_proto_data *pd;
        struct ip_vs_conn *cp;
        int af = state->pf;
        struct sock *sk;

        /* Already marked as IPVS request or reply? */
        if (skb->ipvs_property)
                return NF_ACCEPT;

        sk = skb_to_full_sk(skb);
        /* Bad... Do not break raw sockets */
        if (unlikely(sk && hooknum == NF_INET_LOCAL_OUT &&
                     af == AF_INET)) {

                if (sk->sk_family == PF_INET && inet_test_bit(NODEFRAG, sk))
                        return NF_ACCEPT;
        }

        if (unlikely(!skb_dst(skb)))
                return NF_ACCEPT;

        ip_vs_fill_iph_skb(af, skb, false, &iph);
#ifdef CONFIG_IP_VS_IPV6
        if (af == AF_INET6) {
                if (unlikely(iph.protocol == IPPROTO_ICMPV6)) {
                        int related;
                        int verdict = ip_vs_out_icmp_v6(ipvs, skb, &related,
                                                        hooknum, &iph);

                        if (related)
                                return verdict;
                }
        } else
#endif
                if (unlikely(iph.protocol == IPPROTO_ICMP)) {
                        int related;
                        int verdict = ip_vs_out_icmp(ipvs, skb, &related, hooknum);

                        if (related)
                                return verdict;
                }

        pd = ip_vs_proto_data_get(ipvs, iph.protocol);
        if (unlikely(!pd))
                return NF_ACCEPT;
        pp = pd->pp;

        /* reassemble IP fragments */
#ifdef CONFIG_IP_VS_IPV6
        if (af == AF_INET)
#endif
                if (unlikely(ip_is_fragment(ip_hdr(skb)) && !pp->dont_defrag)) {
                        if (ip_vs_gather_frags(ipvs, skb,
                                               ip_vs_defrag_user(hooknum)))
                                return NF_STOLEN;

                        ip_vs_fill_iph_skb(AF_INET, skb, false, &iph);
                }

        /*
         * Check if the packet belongs to an existing entry
         */
        cp = INDIRECT_CALL_1(pp->conn_out_get, ip_vs_conn_out_get_proto,
                             ipvs, af, skb, &iph);

        if (likely(cp))
                return handle_response(af, skb, pd, cp, &iph, hooknum);

        /* Check for real-server-started requests */
        if (atomic_read(&ipvs->conn_out_counter)) {
                /* Currently only for UDP:
                 * connection oriented protocols typically use
                 * ephemeral ports for outgoing connections, so
                 * related incoming responses would not match any VS
                 */
                if (pp->protocol == IPPROTO_UDP) {
                        cp = __ip_vs_rs_conn_out(hooknum, ipvs, af, skb, &iph);
                        if (likely(cp))
                                return handle_response(af, skb, pd, cp, &iph,
                                                       hooknum);
                }
        }

        if (sysctl_nat_icmp_send(ipvs) &&
            (pp->protocol == IPPROTO_TCP ||
             pp->protocol == IPPROTO_UDP ||
             pp->protocol == IPPROTO_SCTP)) {
                __be16 _ports[2], *pptr;

                pptr = frag_safe_skb_hp(skb, iph.len,
                                         sizeof(_ports), _ports);
                if (pptr == NULL)
                        return NF_ACCEPT;       /* Not for me */
                if (ip_vs_has_real_service(ipvs, af, iph.protocol, &iph.saddr,
                                           pptr[0])) {
                        /*
                         * Notify the real server: there is no
                         * existing entry if it is not RST
                         * packet or not TCP packet.
                         */
                        if ((iph.protocol != IPPROTO_TCP &&
                             iph.protocol != IPPROTO_SCTP)
                             || ((iph.protocol == IPPROTO_TCP
                                  && !is_tcp_reset(skb, iph.len))
                                 || (iph.protocol == IPPROTO_SCTP
                                        && !is_sctp_abort(skb,
                                                iph.len)))) {
#ifdef CONFIG_IP_VS_IPV6
                                if (af == AF_INET6) {
                                        if (!skb->dev)
                                                skb->dev = ipvs->net->loopback_dev;
                                        icmpv6_send(skb,
                                                    ICMPV6_DEST_UNREACH,
                                                    ICMPV6_PORT_UNREACH,
                                                    0);
                                } else
#endif
                                        icmp_send(skb,
                                                  ICMP_DEST_UNREACH,
                                                  ICMP_PORT_UNREACH, 0);
                                return NF_DROP;
                        }
                }
        }

        IP_VS_DBG_PKT(12, af, pp, skb, iph.off,
                      "ip_vs_out: packet continues traversal as normal");
        return NF_ACCEPT;
}

static unsigned int
ip_vs_try_to_schedule(struct netns_ipvs *ipvs, int af, struct sk_buff *skb,
                      struct ip_vs_proto_data *pd,
                      int *verdict, struct ip_vs_conn **cpp,
                      struct ip_vs_iphdr *iph)
{
        struct ip_vs_protocol *pp = pd->pp;

        if (!iph->fragoffs) {
                /* No (second) fragments need to enter here, as nf_defrag_ipv6
                 * replayed fragment zero will already have created the cp
                 */

                /* Schedule and create new connection entry into cpp */
                if (!pp->conn_schedule(ipvs, af, skb, pd, verdict, cpp, iph))
                        return 0;
        }

        if (unlikely(!*cpp)) {
                /* sorry, all this trouble for a no-hit :) */
                IP_VS_DBG_PKT(12, af, pp, skb, iph->off,
                              "ip_vs_in: packet continues traversal as normal");

                /* Fragment couldn't be mapped to a conn entry */
                if (iph->fragoffs)
                        IP_VS_DBG_PKT(7, af, pp, skb, iph->off,
                                      "unhandled fragment");

                *verdict = NF_ACCEPT;
                return 0;
        }

        return 1;
}

/* Check the UDP tunnel and return its header length */
static int ipvs_udp_decap(struct netns_ipvs *ipvs, struct sk_buff *skb,
                          unsigned int offset, __u16 af,
                          const union nf_inet_addr *daddr, __u8 *proto)
{
        struct udphdr _udph, *udph;
        struct ip_vs_dest *dest;

        udph = skb_header_pointer(skb, offset, sizeof(_udph), &_udph);
        if (!udph)
                goto unk;
        offset += sizeof(struct udphdr);
        dest = ip_vs_find_tunnel(ipvs, af, daddr, udph->dest);
        if (!dest)
                goto unk;
        if (dest->tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GUE) {
                struct guehdr _gueh, *gueh;

                gueh = skb_header_pointer(skb, offset, sizeof(_gueh), &_gueh);
                if (!gueh)
                        goto unk;
                if (gueh->control != 0 || gueh->version != 0)
                        goto unk;
                /* Later we can support also IPPROTO_IPV6 */
                if (gueh->proto_ctype != IPPROTO_IPIP)
                        goto unk;
                *proto = gueh->proto_ctype;
                return sizeof(struct udphdr) + sizeof(struct guehdr) +
                       (gueh->hlen << 2);
        }

unk:
        return 0;
}

/* Check the GRE tunnel and return its header length */
static int ipvs_gre_decap(struct netns_ipvs *ipvs, struct sk_buff *skb,
                          unsigned int offset, __u16 af,
                          const union nf_inet_addr *daddr, __u8 *proto)
{
        struct gre_base_hdr _greh, *greh;
        struct ip_vs_dest *dest;

        greh = skb_header_pointer(skb, offset, sizeof(_greh), &_greh);
        if (!greh)
                goto unk;
        dest = ip_vs_find_tunnel(ipvs, af, daddr, 0);
        if (!dest)
                goto unk;
        if (dest->tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
                IP_TUNNEL_DECLARE_FLAGS(flags);
                __be16 type;

                /* Only support version 0 and C (csum) */
                if ((greh->flags & ~GRE_CSUM) != 0)
                        goto unk;
                type = greh->protocol;
                /* Later we can support also IPPROTO_IPV6 */
                if (type != htons(ETH_P_IP))
                        goto unk;
                *proto = IPPROTO_IPIP;

                gre_flags_to_tnl_flags(flags, greh->flags);

                return gre_calc_hlen(flags);
        }

unk:
        return 0;
}

/*
 *      Handle ICMP messages in the outside-to-inside direction (incoming).
 *      Find any that might be relevant, check against existing connections,
 *      forward to the right destination host if relevant.
 *      Currently handles error types - unreachable, quench, ttl exceeded.
 */
static int
ip_vs_in_icmp(struct netns_ipvs *ipvs, struct sk_buff *skb, int *related,
              unsigned int hooknum)
{
        struct iphdr *iph;
        struct icmphdr  _icmph, *ic;
        struct iphdr    _ciph, *cih;    /* The ip header contained within the ICMP */
        struct ip_vs_iphdr ciph;
        struct ip_vs_conn *cp;
        struct ip_vs_protocol *pp;
        struct ip_vs_proto_data *pd;
        unsigned int offset, offset2, ihl, verdict;
        bool tunnel, new_cp = false;
        union nf_inet_addr *raddr;
        char *outer_proto = "IPIP";

        *related = 1;

        /* reassemble IP fragments */
        if (ip_is_fragment(ip_hdr(skb))) {
                if (ip_vs_gather_frags(ipvs, skb, ip_vs_defrag_user(hooknum)))
                        return NF_STOLEN;
        }

        iph = ip_hdr(skb);
        offset = ihl = iph->ihl * 4;
        ic = skb_header_pointer(skb, offset, sizeof(_icmph), &_icmph);
        if (ic == NULL)
                return NF_DROP;

        IP_VS_DBG(12, "Incoming ICMP (%d,%d) %pI4->%pI4\n",
                  ic->type, ntohs(icmp_id(ic)),
                  &iph->saddr, &iph->daddr);

        /*
         * Work through seeing if this is for us.
         * These checks are supposed to be in an order that means easy
         * things are checked first to speed up processing.... however
         * this means that some packets will manage to get a long way
         * down this stack and then be rejected, but that's life.
         */
        if ((ic->type != ICMP_DEST_UNREACH) &&
            (ic->type != ICMP_SOURCE_QUENCH) &&
            (ic->type != ICMP_TIME_EXCEEDED)) {
                *related = 0;
                return NF_ACCEPT;
        }

        /* Now find the contained IP header */
        offset += sizeof(_icmph);
        cih = skb_header_pointer(skb, offset, sizeof(_ciph), &_ciph);
        if (cih == NULL)
                return NF_ACCEPT; /* The packet looks wrong, ignore */
        raddr = (union nf_inet_addr *)&cih->daddr;

        /* Special case for errors for IPIP/UDP/GRE tunnel packets */
        tunnel = false;
        if (cih->protocol == IPPROTO_IPIP) {
                struct ip_vs_dest *dest;

                if (unlikely(cih->frag_off & htons(IP_OFFSET)))
                        return NF_ACCEPT;
                /* Error for our IPIP must arrive at LOCAL_IN */
                if (!(skb_rtable(skb)->rt_flags & RTCF_LOCAL))
                        return NF_ACCEPT;
                dest = ip_vs_find_tunnel(ipvs, AF_INET, raddr, 0);
                /* Only for known tunnel */
                if (!dest || dest->tun_type != IP_VS_CONN_F_TUNNEL_TYPE_IPIP)
                        return NF_ACCEPT;
                offset += cih->ihl * 4;
                cih = skb_header_pointer(skb, offset, sizeof(_ciph), &_ciph);
                if (cih == NULL)
                        return NF_ACCEPT; /* The packet looks wrong, ignore */
                tunnel = true;
        } else if ((cih->protocol == IPPROTO_UDP ||     /* Can be UDP encap */
                    cih->protocol == IPPROTO_GRE) &&    /* Can be GRE encap */
                   /* Error for our tunnel must arrive at LOCAL_IN */
                   (skb_rtable(skb)->rt_flags & RTCF_LOCAL)) {
                __u8 iproto;
                int ulen;

                /* Non-first fragment has no UDP/GRE header */
                if (unlikely(cih->frag_off & htons(IP_OFFSET)))
                        return NF_ACCEPT;
                offset2 = offset + cih->ihl * 4;
                if (cih->protocol == IPPROTO_UDP) {
                        ulen = ipvs_udp_decap(ipvs, skb, offset2, AF_INET,
                                              raddr, &iproto);
                        outer_proto = "UDP";
                } else {
                        ulen = ipvs_gre_decap(ipvs, skb, offset2, AF_INET,
                                              raddr, &iproto);
                        outer_proto = "GRE";
                }
                if (ulen > 0) {
                        /* Skip IP and UDP/GRE tunnel headers */
                        offset = offset2 + ulen;
                        /* Now we should be at the original IP header */
                        cih = skb_header_pointer(skb, offset, sizeof(_ciph),
                                                 &_ciph);
                        if (cih && cih->version == 4 && cih->ihl >= 5 &&
                            iproto == IPPROTO_IPIP)
                                tunnel = true;
                        else
                                return NF_ACCEPT;
                }
        }

        pd = ip_vs_proto_data_get(ipvs, cih->protocol);
        if (!pd)
                return NF_ACCEPT;
        pp = pd->pp;

        /* Is the embedded protocol header present? */
        if (unlikely(cih->frag_off & htons(IP_OFFSET) &&
                     pp->dont_defrag))
                return NF_ACCEPT;

        IP_VS_DBG_PKT(11, AF_INET, pp, skb, offset,
                      "Checking incoming ICMP for");

        offset2 = offset;
        ip_vs_fill_iph_skb_icmp(AF_INET, skb, offset, !tunnel, &ciph);
        offset = ciph.len;

        /* The embedded headers contain source and dest in reverse order.
         * For IPIP/UDP/GRE tunnel this is error for request, not for reply.
         */
        cp = INDIRECT_CALL_1(pp->conn_in_get, ip_vs_conn_in_get_proto,
                             ipvs, AF_INET, skb, &ciph);

        if (!cp) {
                int v;

                if (tunnel || !sysctl_schedule_icmp(ipvs))
                        return NF_ACCEPT;

                if (!ip_vs_try_to_schedule(ipvs, AF_INET, skb, pd, &v, &cp, &ciph))
                        return v;
                new_cp = true;
        }

        verdict = NF_DROP;

        /* Ensure the checksum is correct */
        if (!skb_csum_unnecessary(skb) && ip_vs_checksum_complete(skb, ihl)) {
                /* Failed checksum! */
                IP_VS_DBG(1, "Incoming ICMP: failed checksum from %pI4!\n",
                          &iph->saddr);
                goto out;
        }

        if (tunnel) {
                __be32 info = ic->un.gateway;
                __u8 type = ic->type;
                __u8 code = ic->code;

                /* Update the MTU */
                if (ic->type == ICMP_DEST_UNREACH &&
                    ic->code == ICMP_FRAG_NEEDED) {
                        struct ip_vs_dest *dest = cp->dest;
                        u32 mtu = ntohs(ic->un.frag.mtu);
                        __be16 frag_off = cih->frag_off;

                        /* Strip outer IP and ICMP, go to IPIP/UDP/GRE header */
                        if (pskb_pull(skb, ihl + sizeof(_icmph)) == NULL)
                                goto ignore_tunnel;
                        offset2 -= ihl + sizeof(_icmph);
                        skb_reset_network_header(skb);
                        IP_VS_DBG(12, "ICMP for %s %pI4->%pI4: mtu=%u\n",
                                  outer_proto, &ip_hdr(skb)->saddr,
                                  &ip_hdr(skb)->daddr, mtu);
                        ipv4_update_pmtu(skb, ipvs->net, mtu, 0, 0);
                        /* Client uses PMTUD? */
                        if (!(frag_off & htons(IP_DF)))
                                goto ignore_tunnel;
                        /* Prefer the resulting PMTU */
                        if (dest) {
                                struct ip_vs_dest_dst *dest_dst;

                                dest_dst = rcu_dereference(dest->dest_dst);
                                if (dest_dst)
                                        mtu = dst_mtu(dest_dst->dst_cache);
                        }
                        if (mtu > 68 + sizeof(struct iphdr))
                                mtu -= sizeof(struct iphdr);
                        info = htonl(mtu);
                }
                /* Strip outer IP, ICMP and IPIP/UDP/GRE, go to IP header of
                 * original request.
                 */
                if (pskb_pull(skb, offset2) == NULL)
                        goto ignore_tunnel;
                skb_reset_network_header(skb);
                IP_VS_DBG(12, "Sending ICMP for %pI4->%pI4: t=%u, c=%u, i=%u\n",
                        &ip_hdr(skb)->saddr, &ip_hdr(skb)->daddr,
                        type, code, ntohl(info));
                icmp_send(skb, type, code, info);
                /* ICMP can be shorter but anyways, account it */
                ip_vs_out_stats(cp, skb);

ignore_tunnel:
                consume_skb(skb);
                verdict = NF_STOLEN;
                goto out;
        }

        /* do the statistics and put it back */
        ip_vs_in_stats(cp, skb);
        if (IPPROTO_TCP == cih->protocol || IPPROTO_UDP == cih->protocol ||
            IPPROTO_SCTP == cih->protocol)
                offset += 2 * sizeof(__u16);
        verdict = ip_vs_icmp_xmit(skb, cp, pp, offset, hooknum, &ciph);

out:
        if (likely(!new_cp))
                __ip_vs_conn_put(cp);
        else
                ip_vs_conn_put(cp);

        return verdict;
}

#ifdef CONFIG_IP_VS_IPV6
static int ip_vs_in_icmp_v6(struct netns_ipvs *ipvs, struct sk_buff *skb,
                            int *related, unsigned int hooknum,
                            struct ip_vs_iphdr *iph)
{
        struct icmp6hdr _icmph, *ic;
        struct ip_vs_iphdr ciph = {.flags = 0, .fragoffs = 0};/*Contained IP */
        struct ip_vs_conn *cp;
        struct ip_vs_protocol *pp;
        struct ip_vs_proto_data *pd;
        unsigned int offset, verdict;
        bool new_cp = false;

        *related = 1;

        ic = frag_safe_skb_hp(skb, iph->len, sizeof(_icmph), &_icmph);
        if (ic == NULL)
                return NF_DROP;

        /*
         * Work through seeing if this is for us.
         * These checks are supposed to be in an order that means easy
         * things are checked first to speed up processing.... however
         * this means that some packets will manage to get a long way
         * down this stack and then be rejected, but that's life.
         */
        if (ic->icmp6_type & ICMPV6_INFOMSG_MASK) {
                *related = 0;
                return NF_ACCEPT;
        }
        /* Fragment header that is before ICMP header tells us that:
         * it's not an error message since they can't be fragmented.
         */
        if (iph->flags & IP6_FH_F_FRAG)
                return NF_DROP;

        IP_VS_DBG(8, "Incoming ICMPv6 (%d,%d) %pI6c->%pI6c\n",
                  ic->icmp6_type, ntohs(icmpv6_id(ic)),
                  &iph->saddr, &iph->daddr);

        offset = iph->len + sizeof(_icmph);
        if (!ip_vs_fill_iph_skb_icmp(AF_INET6, skb, offset, true, &ciph))
                return NF_ACCEPT;

        pd = ip_vs_proto_data_get(ipvs, ciph.protocol);
        if (!pd)
                return NF_ACCEPT;
        pp = pd->pp;

        /* Cannot handle fragmented embedded protocol */
        if (ciph.fragoffs)
                return NF_ACCEPT;

        IP_VS_DBG_PKT(11, AF_INET6, pp, skb, offset,
                      "Checking incoming ICMPv6 for");

        /* The embedded headers contain source and dest in reverse order
         * if not from localhost
         */
        cp = INDIRECT_CALL_1(pp->conn_in_get, ip_vs_conn_in_get_proto,
                             ipvs, AF_INET6, skb, &ciph);

        if (!cp) {
                int v;

                if (!sysctl_schedule_icmp(ipvs))
                        return NF_ACCEPT;

                if (!ip_vs_try_to_schedule(ipvs, AF_INET6, skb, pd, &v, &cp, &ciph))
                        return v;

                new_cp = true;
        }

        /* VS/TUN, VS/DR and LOCALNODE just let it go */
        if ((hooknum == NF_INET_LOCAL_OUT) &&
            (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ)) {
                verdict = NF_ACCEPT;
                goto out;
        }

        /* do the statistics and put it back */
        ip_vs_in_stats(cp, skb);

        /* Need to mangle contained IPv6 header in ICMPv6 packet */
        offset = ciph.len;
        if (IPPROTO_TCP == ciph.protocol || IPPROTO_UDP == ciph.protocol ||
            IPPROTO_SCTP == ciph.protocol)
                offset += 2 * sizeof(__u16); /* Also mangle ports */

        verdict = ip_vs_icmp_xmit_v6(skb, cp, pp, offset, hooknum, &ciph);

out:
        if (likely(!new_cp))
                __ip_vs_conn_put(cp);
        else
                ip_vs_conn_put(cp);

        return verdict;
}
#endif


/*
 *      Check if it's for virtual services, look it up,
 *      and send it on its way...
 */
static unsigned int
ip_vs_in_hook(void *priv, struct sk_buff *skb, const struct nf_hook_state *state)
{
        struct netns_ipvs *ipvs = net_ipvs(state->net);
        unsigned int hooknum = state->hook;
        struct ip_vs_iphdr iph;
        struct ip_vs_protocol *pp;
        struct ip_vs_proto_data *pd;
        struct ip_vs_conn *cp;
        int ret, pkts;
        struct sock *sk;
        int af = state->pf;

        /* Already marked as IPVS request or reply? */
        if (skb->ipvs_property)
                return NF_ACCEPT;

        /*
         *      Big tappo:
         *      - remote client: only PACKET_HOST
         *      - route: used for struct net when skb->dev is unset
         */
        if (unlikely((skb->pkt_type != PACKET_HOST &&
                      hooknum != NF_INET_LOCAL_OUT) ||
                     !skb_dst(skb))) {
                ip_vs_fill_iph_skb(af, skb, false, &iph);
                IP_VS_DBG_BUF(12, "packet type=%d proto=%d daddr=%s"
                              " ignored in hook %u\n",
                              skb->pkt_type, iph.protocol,
                              IP_VS_DBG_ADDR(af, &iph.daddr), hooknum);
                return NF_ACCEPT;
        }
        /* ipvs enabled in this netns ? */
        if (unlikely(sysctl_backup_only(ipvs)))
                return NF_ACCEPT;

        ip_vs_fill_iph_skb(af, skb, false, &iph);

        /* Bad... Do not break raw sockets */
        sk = skb_to_full_sk(skb);
        if (unlikely(sk && hooknum == NF_INET_LOCAL_OUT &&
                     af == AF_INET)) {

                if (sk->sk_family == PF_INET && inet_test_bit(NODEFRAG, sk))
                        return NF_ACCEPT;
        }

#ifdef CONFIG_IP_VS_IPV6
        if (af == AF_INET6) {
                if (unlikely(iph.protocol == IPPROTO_ICMPV6)) {
                        int related;
                        int verdict = ip_vs_in_icmp_v6(ipvs, skb, &related,
                                                       hooknum, &iph);

                        if (related)
                                return verdict;
                }
        } else
#endif
                if (unlikely(iph.protocol == IPPROTO_ICMP)) {
                        int related;
                        int verdict = ip_vs_in_icmp(ipvs, skb, &related,
                                                    hooknum);

                        if (related)
                                return verdict;
                }

        /* Protocol supported? */
        pd = ip_vs_proto_data_get(ipvs, iph.protocol);
        if (unlikely(!pd)) {
                /* The only way we'll see this packet again is if it's
                 * encapsulated, so mark it with ipvs_property=1 so we
                 * skip it if we're ignoring tunneled packets
                 */
                if (sysctl_ignore_tunneled(ipvs))
                        skb->ipvs_property = 1;

                return NF_ACCEPT;
        }
        pp = pd->pp;
        /*
         * Check if the packet belongs to an existing connection entry
         */
        cp = INDIRECT_CALL_1(pp->conn_in_get, ip_vs_conn_in_get_proto,
                             ipvs, af, skb, &iph);

        if (!iph.fragoffs && is_new_conn(skb, &iph) && cp) {
                int conn_reuse_mode = sysctl_conn_reuse_mode(ipvs);
                bool old_ct = false, resched = false;

                if (unlikely(sysctl_expire_nodest_conn(ipvs)) && cp->dest &&
                    unlikely(!atomic_read(&cp->dest->weight))) {
                        resched = true;
                        old_ct = ip_vs_conn_uses_old_conntrack(cp, skb);
                } else if (conn_reuse_mode &&
                           is_new_conn_expected(cp, conn_reuse_mode)) {
                        old_ct = ip_vs_conn_uses_old_conntrack(cp, skb);
                        if (!atomic_read(&cp->n_control)) {
                                resched = true;
                        } else {
                                /* Do not reschedule controlling connection
                                 * that uses conntrack while it is still
                                 * referenced by controlled connection(s).
                                 */
                                resched = !old_ct;
                        }
                }

                if (resched) {
                        if (!old_ct)
                                cp->flags &= ~IP_VS_CONN_F_NFCT;
                        if (!atomic_read(&cp->n_control))
                                ip_vs_conn_expire_now(cp);
                        __ip_vs_conn_put(cp);
                        if (old_ct)
                                return NF_DROP;
                        cp = NULL;
                }
        }

        /* Check the server status */
        if (cp && cp->dest && !(cp->dest->flags & IP_VS_DEST_F_AVAILABLE)) {
                /* the destination server is not available */
                if (sysctl_expire_nodest_conn(ipvs)) {
                        bool old_ct = ip_vs_conn_uses_old_conntrack(cp, skb);

                        if (!old_ct)
                                cp->flags &= ~IP_VS_CONN_F_NFCT;

                        ip_vs_conn_expire_now(cp);
                        __ip_vs_conn_put(cp);
                        if (old_ct)
                                return NF_DROP;
                        cp = NULL;
                } else {
                        __ip_vs_conn_put(cp);
                        return NF_DROP;
                }
        }

        if (unlikely(!cp)) {
                int v;

                if (!ip_vs_try_to_schedule(ipvs, af, skb, pd, &v, &cp, &iph))
                        return v;
        }

        IP_VS_DBG_PKT(11, af, pp, skb, iph.off, "Incoming packet");

        ip_vs_in_stats(cp, skb);
        ip_vs_set_state(cp, IP_VS_DIR_INPUT, skb, pd);
        if (cp->packet_xmit)
                ret = cp->packet_xmit(skb, cp, pp, &iph);
                /* do not touch skb anymore */
        else {
                IP_VS_DBG_RL("warning: packet_xmit is null");
                ret = NF_ACCEPT;
        }

        /* Increase its packet counter and check if it is needed
         * to be synchronized
         *
         * Sync connection if it is about to close to
         * encorage the standby servers to update the connections timeout
         *
         * For ONE_PKT let ip_vs_sync_conn() do the filter work.
         */

        if (cp->flags & IP_VS_CONN_F_ONE_PACKET)
                pkts = sysctl_sync_threshold(ipvs);
        else
                pkts = atomic_inc_return(&cp->in_pkts);

        if (ipvs->sync_state & IP_VS_STATE_MASTER)
                ip_vs_sync_conn(ipvs, cp, pkts);
        else if ((cp->flags & IP_VS_CONN_F_ONE_PACKET) && cp->control)
                /* increment is done inside ip_vs_sync_conn too */
                atomic_inc(&cp->control->in_pkts);

        ip_vs_conn_put(cp);
        return ret;
}

/*
 *      It is hooked at the NF_INET_FORWARD chain, in order to catch ICMP
 *      related packets destined for 0.0.0.0/0.
 *      When fwmark-based virtual service is used, such as transparent
 *      cache cluster, TCP packets can be marked and routed to ip_vs_in,
 *      but ICMP destined for 0.0.0.0/0 cannot not be easily marked and
 *      sent to ip_vs_in_icmp. So, catch them at the NF_INET_FORWARD chain
 *      and send them to ip_vs_in_icmp.
 */
static unsigned int
ip_vs_forward_icmp(void *priv, struct sk_buff *skb,
                   const struct nf_hook_state *state)
{
        struct netns_ipvs *ipvs = net_ipvs(state->net);
        int r;

        /* ipvs enabled in this netns ? */
        if (unlikely(sysctl_backup_only(ipvs)))
                return NF_ACCEPT;

        if (state->pf == NFPROTO_IPV4) {
                if (ip_hdr(skb)->protocol != IPPROTO_ICMP)
                        return NF_ACCEPT;
#ifdef CONFIG_IP_VS_IPV6
        } else {
                struct ip_vs_iphdr iphdr;

                ip_vs_fill_iph_skb(AF_INET6, skb, false, &iphdr);

                if (iphdr.protocol != IPPROTO_ICMPV6)
                        return NF_ACCEPT;

                return ip_vs_in_icmp_v6(ipvs, skb, &r, state->hook, &iphdr);
#endif
        }

        return ip_vs_in_icmp(ipvs, skb, &r, state->hook);
}

static const struct nf_hook_ops ip_vs_ops4[] = {
        /* After packet filtering, change source only for VS/NAT */
        {
                .hook           = ip_vs_out_hook,
                .pf             = NFPROTO_IPV4,
                .hooknum        = NF_INET_LOCAL_IN,
                .priority       = NF_IP_PRI_NAT_SRC - 2,
        },
        /* After packet filtering, forward packet through VS/DR, VS/TUN,
         * or VS/NAT(change destination), so that filtering rules can be
         * applied to IPVS. */
        {
                .hook           = ip_vs_in_hook,
                .pf             = NFPROTO_IPV4,
                .hooknum        = NF_INET_LOCAL_IN,
                .priority       = NF_IP_PRI_NAT_SRC - 1,
        },
        /* Before ip_vs_in, change source only for VS/NAT */
        {
                .hook           = ip_vs_out_hook,
                .pf             = NFPROTO_IPV4,
                .hooknum        = NF_INET_LOCAL_OUT,
                .priority       = NF_IP_PRI_NAT_DST + 1,
        },
        /* After mangle, schedule and forward local requests */
        {
                .hook           = ip_vs_in_hook,
                .pf             = NFPROTO_IPV4,
                .hooknum        = NF_INET_LOCAL_OUT,
                .priority       = NF_IP_PRI_NAT_DST + 2,
        },
        /* After packet filtering (but before ip_vs_out_icmp), catch icmp
         * destined for 0.0.0.0/0, which is for incoming IPVS connections */
        {
                .hook           = ip_vs_forward_icmp,
                .pf             = NFPROTO_IPV4,
                .hooknum        = NF_INET_FORWARD,
                .priority       = 99,
        },
        /* After packet filtering, change source only for VS/NAT */
        {
                .hook           = ip_vs_out_hook,
                .pf             = NFPROTO_IPV4,
                .hooknum        = NF_INET_FORWARD,
                .priority       = 100,
        },
};

#ifdef CONFIG_IP_VS_IPV6
static const struct nf_hook_ops ip_vs_ops6[] = {
        /* After packet filtering, change source only for VS/NAT */
        {
                .hook           = ip_vs_out_hook,
                .pf             = NFPROTO_IPV6,
                .hooknum        = NF_INET_LOCAL_IN,
                .priority       = NF_IP6_PRI_NAT_SRC - 2,
        },
        /* After packet filtering, forward packet through VS/DR, VS/TUN,
         * or VS/NAT(change destination), so that filtering rules can be
         * applied to IPVS. */
        {
                .hook           = ip_vs_in_hook,
                .pf             = NFPROTO_IPV6,
                .hooknum        = NF_INET_LOCAL_IN,
                .priority       = NF_IP6_PRI_NAT_SRC - 1,
        },
        /* Before ip_vs_in, change source only for VS/NAT */
        {
                .hook           = ip_vs_out_hook,
                .pf             = NFPROTO_IPV6,
                .hooknum        = NF_INET_LOCAL_OUT,
                .priority       = NF_IP6_PRI_NAT_DST + 1,
        },
        /* After mangle, schedule and forward local requests */
        {
                .hook           = ip_vs_in_hook,
                .pf             = NFPROTO_IPV6,
                .hooknum        = NF_INET_LOCAL_OUT,
                .priority       = NF_IP6_PRI_NAT_DST + 2,
        },
        /* After packet filtering (but before ip_vs_out_icmp), catch icmp
         * destined for 0.0.0.0/0, which is for incoming IPVS connections */
        {
                .hook           = ip_vs_forward_icmp,
                .pf             = NFPROTO_IPV6,
                .hooknum        = NF_INET_FORWARD,
                .priority       = 99,
        },
        /* After packet filtering, change source only for VS/NAT */
        {
                .hook           = ip_vs_out_hook,
                .pf             = NFPROTO_IPV6,
                .hooknum        = NF_INET_FORWARD,
                .priority       = 100,
        },
};
#endif

int ip_vs_register_hooks(struct netns_ipvs *ipvs, unsigned int af)
{
        const struct nf_hook_ops *ops;
        unsigned int count;
        unsigned int afmask;
        int ret = 0;

        if (af == AF_INET6) {
#ifdef CONFIG_IP_VS_IPV6
                ops = ip_vs_ops6;
                count = ARRAY_SIZE(ip_vs_ops6);
                afmask = 2;
#else
                return -EINVAL;
#endif
        } else {
                ops = ip_vs_ops4;
                count = ARRAY_SIZE(ip_vs_ops4);
                afmask = 1;
        }

        if (!(ipvs->hooks_afmask & afmask)) {
                ret = nf_register_net_hooks(ipvs->net, ops, count);
                if (ret >= 0)
                        ipvs->hooks_afmask |= afmask;
        }
        return ret;
}

void ip_vs_unregister_hooks(struct netns_ipvs *ipvs, unsigned int af)
{
        const struct nf_hook_ops *ops;
        unsigned int count;
        unsigned int afmask;

        if (af == AF_INET6) {
#ifdef CONFIG_IP_VS_IPV6
                ops = ip_vs_ops6;
                count = ARRAY_SIZE(ip_vs_ops6);
                afmask = 2;
#else
                return;
#endif
        } else {
                ops = ip_vs_ops4;
                count = ARRAY_SIZE(ip_vs_ops4);
                afmask = 1;
        }

        if (ipvs->hooks_afmask & afmask) {
                nf_unregister_net_hooks(ipvs->net, ops, count);
                ipvs->hooks_afmask &= ~afmask;
        }
}

/*
 *      Initialize IP Virtual Server netns mem.
 */
static int __net_init __ip_vs_init(struct net *net)
{
        struct netns_ipvs *ipvs;

        ipvs = net_generic(net, ip_vs_net_id);
        if (ipvs == NULL)
                return -ENOMEM;

        /* Hold the beast until a service is registered */
        WRITE_ONCE(ipvs->enable, 0);
        ipvs->net = net;
        /* Counters used for creating unique names */
        ipvs->gen = atomic_read(&ipvs_netns_cnt);
        atomic_inc(&ipvs_netns_cnt);
        net->ipvs = ipvs;

        if (ip_vs_estimator_net_init(ipvs) < 0)
                goto estimator_fail;

        if (ip_vs_control_net_init(ipvs) < 0)
                goto control_fail;

        if (ip_vs_protocol_net_init(ipvs) < 0)
                goto protocol_fail;

        if (ip_vs_app_net_init(ipvs) < 0)
                goto app_fail;

        if (ip_vs_conn_net_init(ipvs) < 0)
                goto conn_fail;

        if (ip_vs_sync_net_init(ipvs) < 0)
                goto sync_fail;

        return 0;
/*
 * Error handling
 */

sync_fail:
        ip_vs_conn_net_cleanup(ipvs);
conn_fail:
        ip_vs_app_net_cleanup(ipvs);
app_fail:
        ip_vs_protocol_net_cleanup(ipvs);
protocol_fail:
        ip_vs_control_net_cleanup(ipvs);
control_fail:
        ip_vs_estimator_net_cleanup(ipvs);
estimator_fail:
        net->ipvs = NULL;
        return -ENOMEM;
}

static void __net_exit __ip_vs_cleanup_batch(struct list_head *net_list)
{
        struct netns_ipvs *ipvs;
        struct net *net;

        ip_vs_service_nets_cleanup(net_list);   /* ip_vs_flush() with locks */
        list_for_each_entry(net, net_list, exit_list) {
                ipvs = net_ipvs(net);
                ip_vs_conn_net_cleanup(ipvs);
                ip_vs_app_net_cleanup(ipvs);
                ip_vs_protocol_net_cleanup(ipvs);
                ip_vs_control_net_cleanup(ipvs);
                ip_vs_estimator_net_cleanup(ipvs);
                IP_VS_DBG(2, "ipvs netns %d released\n", ipvs->gen);
                net->ipvs = NULL;
        }
}

static void __net_exit __ip_vs_dev_cleanup_batch(struct list_head *net_list)
{
        struct netns_ipvs *ipvs;
        struct net *net;

        list_for_each_entry(net, net_list, exit_list) {
                ipvs = net_ipvs(net);
                ip_vs_unregister_hooks(ipvs, AF_INET);
                ip_vs_unregister_hooks(ipvs, AF_INET6);
                WRITE_ONCE(ipvs->enable, 0);    /* Disable packet reception */
                smp_wmb();
                ip_vs_sync_net_cleanup(ipvs);
        }
}

static struct pernet_operations ipvs_core_ops = {
        .init = __ip_vs_init,
        .exit_batch = __ip_vs_cleanup_batch,
        .id   = &ip_vs_net_id,
        .size = sizeof(struct netns_ipvs),
};

static struct pernet_operations ipvs_core_dev_ops = {
        .exit_batch = __ip_vs_dev_cleanup_batch,
};

/*
 *      Initialize IP Virtual Server
 */
static int __init ip_vs_init(void)
{
        int ret;

        ret = ip_vs_control_init();
        if (ret < 0) {
                pr_err("can't setup control.\n");
                goto exit;
        }

        ip_vs_protocol_init();

        ret = ip_vs_conn_init();
        if (ret < 0) {
                pr_err("can't setup connection table.\n");
                goto cleanup_protocol;
        }

        ret = register_pernet_subsys(&ipvs_core_ops);   /* Alloc ip_vs struct */
        if (ret < 0)
                goto cleanup_conn;

        ret = register_pernet_device(&ipvs_core_dev_ops);
        if (ret < 0)
                goto cleanup_sub;

        ret = ip_vs_register_nl_ioctl();
        if (ret < 0) {
                pr_err("can't register netlink/ioctl.\n");
                goto cleanup_dev;
        }

        pr_info("ipvs loaded.\n");

        return ret;

cleanup_dev:
        unregister_pernet_device(&ipvs_core_dev_ops);
cleanup_sub:
        unregister_pernet_subsys(&ipvs_core_ops);
cleanup_conn:
        ip_vs_conn_cleanup();
cleanup_protocol:
        ip_vs_protocol_cleanup();
        ip_vs_control_cleanup();
exit:
        return ret;
}

static void __exit ip_vs_cleanup(void)
{
        ip_vs_unregister_nl_ioctl();
        unregister_pernet_device(&ipvs_core_dev_ops);
        unregister_pernet_subsys(&ipvs_core_ops);       /* free ip_vs struct */
        ip_vs_conn_cleanup();
        ip_vs_protocol_cleanup();
        ip_vs_control_cleanup();
        /* common rcu_barrier() used by:
         * - ip_vs_control_cleanup()
         */
        rcu_barrier();
        pr_info("ipvs unloaded.\n");
}

module_init(ip_vs_init);
module_exit(ip_vs_cleanup);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("IP Virtual Server");