ip_vs_core.c

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/*
 * 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 <[email protected]>
 *              Peter Kese <[email protected]>
 *              Julian Anastasov <[email protected]>
 *
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 *
 * 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 KMSG_COMPONENT "IPVS"
#define pr_fmt(fmt) KMSG_COMPONENT ": " 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/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>


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

int ip_vs_net_id __read_mostly;
#ifdef IP_VS_GENERIC_NETNS
EXPORT_SYMBOL(ip_vs_net_id);
#endif
/* 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_%d", 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 = net_ipvs(skb_net(skb));

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

        s = this_cpu_ptr(dest->stats.cpustats);
        s->ustats.inpkts++;
        u64_stats_update_begin(&s->syncp);
        s->ustats.inbytes += skb->len;
        u64_stats_update_end(&s->syncp);

        s = this_cpu_ptr(dest->svc->stats.cpustats);
        s->ustats.inpkts++;
        u64_stats_update_begin(&s->syncp);
        s->ustats.inbytes += skb->len;
        u64_stats_update_end(&s->syncp);

        s = this_cpu_ptr(ipvs->tot_stats.cpustats);
        s->ustats.inpkts++;
        u64_stats_update_begin(&s->syncp);
        s->ustats.inbytes += skb->len;
        u64_stats_update_end(&s->syncp);
    }
}


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 = net_ipvs(skb_net(skb));

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

        s = this_cpu_ptr(dest->stats.cpustats);
        s->ustats.outpkts++;
        u64_stats_update_begin(&s->syncp);
        s->ustats.outbytes += skb->len;
        u64_stats_update_end(&s->syncp);

        s = this_cpu_ptr(dest->svc->stats.cpustats);
        s->ustats.outpkts++;
        u64_stats_update_begin(&s->syncp);
        s->ustats.outbytes += skb->len;
        u64_stats_update_end(&s->syncp);

        s = this_cpu_ptr(ipvs->tot_stats.cpustats);
        s->ustats.outpkts++;
        u64_stats_update_begin(&s->syncp);
        s->ustats.outbytes += skb->len;
        u64_stats_update_end(&s->syncp);
    }
}


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

    s = this_cpu_ptr(cp->dest->stats.cpustats);
    s->ustats.conns++;

    s = this_cpu_ptr(svc->stats.cpustats);
    s->ustats.conns++;

    s = this_cpu_ptr(ipvs->tot_stats.cpustats);
    s->ustats.conns++;
}


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->net, svc->af, protocol, caddr, cport, vaddr,
                  vport, p);
    p->pe = 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_conn *cp = NULL;
    struct ip_vs_iphdr iph;
    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 */

    ip_vs_fill_iphdr(svc->af, skb_network_header(skb), &iph);

    /* Mask saddr with the netmask to adjust template granularity */
#ifdef CONFIG_IP_VS_IPV6
    if (svc->af == AF_INET6)
        ipv6_addr_prefix(&snet.in6, &iph.saddr.in6, svc->netmask);
    else
#endif
        snet.ip = iph.saddr.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, &iph.saddr), ntohs(src_port),
              IP_VS_DBG_ADDR(svc->af, &iph.daddr), 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 = &iph.daddr;
        __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)) {
        /*
         * No template found or the dest of the connection
         * template is not available.
         * return *ignored=0 i.e. ICMP and NF_DROP
         */
        dest = svc->scheduler->schedule(svc, skb);
        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->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->net, svc->af, iph.protocol, &iph.saddr,
                  src_port, &iph.daddr, dst_port, &param);

    cp = ip_vs_conn_new(&param, &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_protocol *pp = pd->pp;
    struct ip_vs_conn *cp = NULL;
    struct ip_vs_iphdr iph;
    struct ip_vs_dest *dest;
    __be16 _ports[2], *pptr;
    unsigned int flags;

    *ignored = 1;
    ip_vs_fill_iphdr(svc->af, skb_network_header(skb), &iph);
    pptr = skb_header_pointer(skb, iph.len, sizeof(_ports), _ports);
    if (pptr == NULL)
        return NULL;

    /*
     * 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 (pptr[0] == FTPDATA) {
        IP_VS_DBG_PKT(12, svc->af, pp, skb, 0,
                  "Not scheduling FTPDATA");
        return NULL;
    }

    /*
     *    Do not schedule replies from local real server.
     */
    if ((!skb->dev || skb->dev->flags & IFF_LOOPBACK) &&
        (cp = pp->conn_in_get(svc->af, skb, &iph, iph.len, 1))) {
        IP_VS_DBG_PKT(12, svc->af, pp, skb, 0,
                  "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, pptr[0], pptr[1], ignored);

    *ignored = 0;

    /*
     *    Non-persistent service
     */
    if (!svc->fwmark && pptr[1] != svc->port) {
        if (!svc->port)
            pr_err("Schedule: port zero only supported "
                   "in persistent services, "
                   "check your ipvs configuration\n");
        return NULL;
    }

    dest = svc->scheduler->schedule(svc, skb);
    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->net, svc->af, iph.protocol,
                      &iph.saddr, pptr[0], &iph.daddr, pptr[1],
                      &p);
        cp = ip_vs_conn_new(&p, &dest->addr,
                    dest->port ? dest->port : pptr[1],
                    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(svc->af, &cp->caddr), ntohs(cp->cport),
              IP_VS_DBG_ADDR(svc->af, &cp->vaddr), ntohs(cp->vport),
              IP_VS_DBG_ADDR(svc->af, &cp->daddr), ntohs(cp->dport),
              cp->flags, atomic_read(&cp->refcnt));

    ip_vs_conn_stats(cp, svc);
    return cp;
}


/*
 *  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)
{
    __be16 _ports[2], *pptr;
    struct ip_vs_iphdr iph;
#ifdef CONFIG_SYSCTL
    struct net *net;
    struct netns_ipvs *ipvs;
    int unicast;
#endif

    ip_vs_fill_iphdr(svc->af, skb_network_header(skb), &iph);

    pptr = skb_header_pointer(skb, iph.len, sizeof(_ports), _ports);
    if (pptr == NULL) {
        ip_vs_service_put(svc);
        return NF_DROP;
    }

#ifdef CONFIG_SYSCTL
    net = skb_net(skb);

#ifdef CONFIG_IP_VS_IPV6
    if (svc->af == AF_INET6)
        unicast = ipv6_addr_type(&iph.daddr.in6) & IPV6_ADDR_UNICAST;
    else
#endif
        unicast = (inet_addr_type(net, iph.daddr.ip) == RTN_UNICAST);

    /* 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 */
    ipvs = net_ipvs(net);
    if (ipvs->sysctl_cache_bypass && svc->fwmark && unicast) {
        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 } };

        ip_vs_service_put(svc);

        /* 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->net, svc->af, iph.protocol,
                          &iph.saddr, pptr[0],
                          &iph.daddr, pptr[1], &p);
            cp = ip_vs_conn_new(&p, &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);
        /* do not touch skb anymore */

        atomic_inc(&cp->in_pkts);
        ip_vs_conn_put(cp);
        return ret;
    }
#endif

    /*
     * 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) && (pptr[1] != FTPPORT)) {
        ip_vs_service_put(svc);
        return NF_ACCEPT;
    }

    ip_vs_service_put(svc);

    /*
     * 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) {
            struct net *net = dev_net(skb_dst(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 sk_buff *skb)
{
    struct netns_ipvs *ipvs = net_ipvs(skb_net(skb));
    return ipvs->sysctl_snat_reroute;
}

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

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

#else

static int sysctl_snat_reroute(struct sk_buff *skb) { return 0; }
static int sysctl_nat_icmp_send(struct net *net) { return 0; }
static int sysctl_expire_nodest_conn(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 sk_buff *skb, u_int32_t user)
{
    int err = ip_defrag(skb, user);

    if (!err)
        ip_send_check(ip_hdr(skb));

    return err;
}

#ifdef CONFIG_IP_VS_IPV6
static inline int ip_vs_gather_frags_v6(struct sk_buff *skb, u_int32_t user)
{
    /* TODO IPv6: Find out what to do here for IPv6 */
    return 0;
}
#endif

static int ip_vs_route_me_harder(int af, struct sk_buff *skb)
{
#ifdef CONFIG_IP_VS_IPV6
    if (af == AF_INET6) {
        if (sysctl_snat_reroute(skb) && ip6_route_me_harder(skb) != 0)
            return 1;
    } else
#endif
        if ((sysctl_snat_reroute(skb) ||
             skb_rtable(skb)->rt_flags & RTCF_LOCAL) &&
            ip_route_me_harder(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 = sizeof(struct ipv6hdr);
    struct icmp6hdr *icmph   = (struct icmp6hdr *)(skb_network_header(skb) +
                              icmp_offset);
    struct ipv6hdr *ciph     = (struct ipv6hdr *)(icmph + 1);

    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 (IPPROTO_TCP == ciph->nexthdr || IPPROTO_UDP == ciph->nexthdr ||
        IPPROTO_SCTP == ciph->nexthdr) {
        __be16 *ports = (void *)ciph + sizeof(struct ipv6hdr);

        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 verdict = NF_DROP;

    if (IP_VS_FWD_METHOD(cp) != 0) {
        pr_err("shouldn't reach here, because the box is on the "
               "half connection in the tun/dr module.\n");
    }

    /* 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_make_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(af, skb))
        goto out;

    /* 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 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(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");

    offset += cih->ihl * 4;

    ip_vs_fill_iphdr(AF_INET, cih, &ciph);
    /* The embedded headers contain source and dest in reverse order */
    cp = pp->conn_out_get(AF_INET, skb, &ciph, offset, 1);
    if (!cp)
        return NF_ACCEPT;

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

#ifdef CONFIG_IP_VS_IPV6
static int ip_vs_out_icmp_v6(struct sk_buff *skb, int *related,
                 unsigned int hooknum)
{
    struct ipv6hdr *iph;
    struct icmp6hdr _icmph, *ic;
    struct ipv6hdr  _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;
    union nf_inet_addr snet;

    *related = 1;

    /* reassemble IP fragments */
    if (ipv6_hdr(skb)->nexthdr == IPPROTO_FRAGMENT) {
        if (ip_vs_gather_frags_v6(skb, ip_vs_defrag_user(hooknum)))
            return NF_STOLEN;
    }

    iph = ipv6_hdr(skb);
    offset = sizeof(struct ipv6hdr);
    ic = skb_header_pointer(skb, offset, sizeof(_icmph), &_icmph);
    if (ic == NULL)
        return NF_DROP;

    IP_VS_DBG(12, "Outgoing ICMPv6 (%d,%d) %pI6->%pI6\n",
          ic->icmp6_type, ntohs(icmpv6_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->icmp6_type != ICMPV6_DEST_UNREACH) &&
        (ic->icmp6_type != ICMPV6_PKT_TOOBIG) &&
        (ic->icmp6_type != ICMPV6_TIME_EXCEED)) {
        *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->nexthdr);
    if (!pp)
        return NF_ACCEPT;

    /* Is the embedded protocol header present? */
    /* TODO: we don't support fragmentation at the moment anyways */
    if (unlikely(cih->nexthdr == IPPROTO_FRAGMENT && pp->dont_defrag))
        return NF_ACCEPT;

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

    offset += sizeof(struct ipv6hdr);

    ip_vs_fill_iphdr(AF_INET6, cih, &ciph);
    /* The embedded headers contain source and dest in reverse order */
    cp = pp->conn_out_get(AF_INET6, skb, &ciph, offset, 1);
    if (!cp)
        return NF_ACCEPT;

    snet.in6 = iph->saddr;
    return handle_response_icmp(AF_INET6, skb, &snet, cih->nexthdr, cp,
                    pp, offset, sizeof(struct ipv6hdr));
}
#endif

/*
 * Check if sctp chunc is ABORT chunk
 */
static inline int is_sctp_abort(const struct sk_buff *skb, int nh_len)
{
    sctp_chunkhdr_t *sch, schunk;
    sch = skb_header_pointer(skb, nh_len + sizeof(sctp_sctphdr_t),
            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;
}

/* 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, int ihl)
{
    struct ip_vs_protocol *pp = pd->pp;

    IP_VS_DBG_PKT(11, af, pp, skb, 0, "Outgoing packet");

    if (!skb_make_writable(skb, ihl))
        goto drop;

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

    IP_VS_DBG_PKT(10, af, pp, skb, 0, "After SNAT");

    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);

    LeaveFunction(11);
    return NF_ACCEPT;

drop:
    ip_vs_conn_put(cp);
    kfree_skb(skb);
    LeaveFunction(11);
    return NF_STOLEN;
}

/*
 *  Check if outgoing packet belongs to the established ip_vs_conn.
 */
static unsigned int
ip_vs_out(unsigned int hooknum, struct sk_buff *skb, int af)
{
    struct net *net = NULL;
    struct ip_vs_iphdr iph;
    struct ip_vs_protocol *pp;
    struct ip_vs_proto_data *pd;
    struct ip_vs_conn *cp;

    EnterFunction(11);

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

    /* Bad... Do not break raw sockets */
    if (unlikely(skb->sk != NULL && hooknum == NF_INET_LOCAL_OUT &&
             af == AF_INET)) {
        struct sock *sk = skb->sk;
        struct inet_sock *inet = inet_sk(skb->sk);

        if (inet && sk->sk_family == PF_INET && inet->nodefrag)
            return NF_ACCEPT;
    }

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

    net = skb_net(skb);
    if (!net_ipvs(net)->enable)
        return NF_ACCEPT;

    ip_vs_fill_iphdr(af, skb_network_header(skb), &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(skb, &related,
                            hooknum);

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

            if (related)
                return verdict;
            ip_vs_fill_iphdr(af, skb_network_header(skb), &iph);
        }

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

    /* reassemble IP fragments */
#ifdef CONFIG_IP_VS_IPV6
    if (af == AF_INET6) {
        if (ipv6_hdr(skb)->nexthdr == IPPROTO_FRAGMENT) {
            if (ip_vs_gather_frags_v6(skb,
                          ip_vs_defrag_user(hooknum)))
                return NF_STOLEN;
        }

        ip_vs_fill_iphdr(af, skb_network_header(skb), &iph);
    } else
#endif
        if (unlikely(ip_is_fragment(ip_hdr(skb)) && !pp->dont_defrag)) {
            if (ip_vs_gather_frags(skb,
                           ip_vs_defrag_user(hooknum)))
                return NF_STOLEN;

            ip_vs_fill_iphdr(af, skb_network_header(skb), &iph);
        }

    /*
     * Check if the packet belongs to an existing entry
     */
    cp = pp->conn_out_get(af, skb, &iph, iph.len, 0);

    if (likely(cp))
        return handle_response(af, skb, pd, cp, iph.len);
    if (sysctl_nat_icmp_send(net) &&
        (pp->protocol == IPPROTO_TCP ||
         pp->protocol == IPPROTO_UDP ||
         pp->protocol == IPPROTO_SCTP)) {
        __be16 _ports[2], *pptr;

        pptr = skb_header_pointer(skb, iph.len,
                      sizeof(_ports), _ports);
        if (pptr == NULL)
            return NF_ACCEPT;   /* Not for me */
        if (ip_vs_lookup_real_service(net, 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) {
                    struct net *net =
                        dev_net(skb_dst(skb)->dev);

                    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;
            }
        }
    }
    IP_VS_DBG_PKT(12, af, pp, skb, 0,
              "ip_vs_out: packet continues traversal as normal");
    return NF_ACCEPT;
}

/*
 *  It is hooked at the NF_INET_FORWARD and NF_INET_LOCAL_IN chain,
 *  used only for VS/NAT.
 *  Check if packet is reply for established ip_vs_conn.
 */
static unsigned int
ip_vs_reply4(unsigned int hooknum, struct sk_buff *skb,
         const struct net_device *in, const struct net_device *out,
         int (*okfn)(struct sk_buff *))
{
    return ip_vs_out(hooknum, skb, AF_INET);
}

/*
 *  It is hooked at the NF_INET_LOCAL_OUT chain, used only for VS/NAT.
 *  Check if packet is reply for established ip_vs_conn.
 */
static unsigned int
ip_vs_local_reply4(unsigned int hooknum, struct sk_buff *skb,
           const struct net_device *in, const struct net_device *out,
           int (*okfn)(struct sk_buff *))
{
    unsigned int verdict;

    /* Disable BH in LOCAL_OUT until all places are fixed */
    local_bh_disable();
    verdict = ip_vs_out(hooknum, skb, AF_INET);
    local_bh_enable();
    return verdict;
}

#ifdef CONFIG_IP_VS_IPV6

/*
 *  It is hooked at the NF_INET_FORWARD and NF_INET_LOCAL_IN chain,
 *  used only for VS/NAT.
 *  Check if packet is reply for established ip_vs_conn.
 */
static unsigned int
ip_vs_reply6(unsigned int hooknum, struct sk_buff *skb,
         const struct net_device *in, const struct net_device *out,
         int (*okfn)(struct sk_buff *))
{
    return ip_vs_out(hooknum, skb, AF_INET6);
}

/*
 *  It is hooked at the NF_INET_LOCAL_OUT chain, used only for VS/NAT.
 *  Check if packet is reply for established ip_vs_conn.
 */
static unsigned int
ip_vs_local_reply6(unsigned int hooknum, struct sk_buff *skb,
           const struct net_device *in, const struct net_device *out,
           int (*okfn)(struct sk_buff *))
{
    unsigned int verdict;

    /* Disable BH in LOCAL_OUT until all places are fixed */
    local_bh_disable();
    verdict = ip_vs_out(hooknum, skb, AF_INET6);
    local_bh_enable();
    return verdict;
}

#endif

/*
 *  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 sk_buff *skb, int *related, unsigned int hooknum)
{
    struct net *net = NULL;
    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 ipip;

    *related = 1;

    /* reassemble IP fragments */
    if (ip_is_fragment(ip_hdr(skb))) {
        if (ip_vs_gather_frags(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 */

    net = skb_net(skb);

    /* Special case for errors for IPIP packets */
    ipip = false;
    if (cih->protocol == IPPROTO_IPIP) {
        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;
        offset += cih->ihl * 4;
        cih = skb_header_pointer(skb, offset, sizeof(_ciph), &_ciph);
        if (cih == NULL)
            return NF_ACCEPT; /* The packet looks wrong, ignore */
        ipip = true;
    }

    pd = ip_vs_proto_data_get(net, 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;
    offset += cih->ihl * 4;

    ip_vs_fill_iphdr(AF_INET, cih, &ciph);
    /* The embedded headers contain source and dest in reverse order.
     * For IPIP this is error for request, not for reply.
     */
    cp = pp->conn_in_get(AF_INET, skb, &ciph, offset, ipip ? 0 : 1);
    if (!cp)
        return NF_ACCEPT;

    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 (ipip) {
        __be32 info = ic->un.gateway;

        /* 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);

            /* Strip outer IP and ICMP, go to IPIP header */
            __skb_pull(skb, ihl + sizeof(_icmph));
            offset2 -= ihl + sizeof(_icmph);
            skb_reset_network_header(skb);
            IP_VS_DBG(12, "ICMP for IPIP %pI4->%pI4: mtu=%u\n",
                &ip_hdr(skb)->saddr, &ip_hdr(skb)->daddr, mtu);
            rcu_read_lock();
            ipv4_update_pmtu(skb, dev_net(skb->dev),
                     mtu, 0, 0, 0, 0);
            rcu_read_unlock();
            /* Client uses PMTUD? */
            if (!(cih->frag_off & htons(IP_DF)))
                goto ignore_ipip;
            /* Prefer the resulting PMTU */
            if (dest) {
                spin_lock(&dest->dst_lock);
                if (dest->dst_cache)
                    mtu = dst_mtu(dest->dst_cache);
                spin_unlock(&dest->dst_lock);
            }
            if (mtu > 68 + sizeof(struct iphdr))
                mtu -= sizeof(struct iphdr);
            info = htonl(mtu);
        }
        /* Strip outer IP, ICMP and IPIP, go to IP header of
         * original request.
         */
        __skb_pull(skb, offset2);
        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,
            ic->type, ic->code, ntohl(info));
        icmp_send(skb, ic->type, ic->code, info);
        /* ICMP can be shorter but anyways, account it */
        ip_vs_out_stats(cp, skb);

ignore_ipip:
        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)
        offset += 2 * sizeof(__u16);
    verdict = ip_vs_icmp_xmit(skb, cp, pp, offset, hooknum);

out:
    __ip_vs_conn_put(cp);

    return verdict;
}

#ifdef CONFIG_IP_VS_IPV6
static int
ip_vs_in_icmp_v6(struct sk_buff *skb, int *related, unsigned int hooknum)
{
    struct net *net = NULL;
    struct ipv6hdr *iph;
    struct icmp6hdr _icmph, *ic;
    struct ipv6hdr  _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, verdict;

    *related = 1;

    /* reassemble IP fragments */
    if (ipv6_hdr(skb)->nexthdr == IPPROTO_FRAGMENT) {
        if (ip_vs_gather_frags_v6(skb, ip_vs_defrag_user(hooknum)))
            return NF_STOLEN;
    }

    iph = ipv6_hdr(skb);
    offset = sizeof(struct ipv6hdr);
    ic = skb_header_pointer(skb, offset, sizeof(_icmph), &_icmph);
    if (ic == NULL)
        return NF_DROP;

    IP_VS_DBG(12, "Incoming ICMPv6 (%d,%d) %pI6->%pI6\n",
          ic->icmp6_type, ntohs(icmpv6_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->icmp6_type != ICMPV6_DEST_UNREACH) &&
        (ic->icmp6_type != ICMPV6_PKT_TOOBIG) &&
        (ic->icmp6_type != ICMPV6_TIME_EXCEED)) {
        *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 */

    net = skb_net(skb);
    pd = ip_vs_proto_data_get(net, cih->nexthdr);
    if (!pd)
        return NF_ACCEPT;
    pp = pd->pp;

    /* Is the embedded protocol header present? */
    /* TODO: we don't support fragmentation at the moment anyways */
    if (unlikely(cih->nexthdr == IPPROTO_FRAGMENT && pp->dont_defrag))
        return NF_ACCEPT;

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

    offset += sizeof(struct ipv6hdr);

    ip_vs_fill_iphdr(AF_INET6, cih, &ciph);
    /* The embedded headers contain source and dest in reverse order */
    cp = pp->conn_in_get(AF_INET6, skb, &ciph, offset, 1);
    if (!cp)
        return NF_ACCEPT;

    /* do the statistics and put it back */
    ip_vs_in_stats(cp, skb);
    if (IPPROTO_TCP == cih->nexthdr || IPPROTO_UDP == cih->nexthdr ||
        IPPROTO_SCTP == cih->nexthdr)
        offset += 2 * sizeof(__u16);
    verdict = ip_vs_icmp_xmit_v6(skb, cp, pp, offset, hooknum);

    __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(unsigned int hooknum, struct sk_buff *skb, int af)
{
    struct net *net;
    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 netns_ipvs *ipvs;

    /* 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_iphdr(af, skb_network_header(skb), &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 ? */
    net = skb_net(skb);
    if (!net_ipvs(net)->enable)
        return NF_ACCEPT;

    ip_vs_fill_iphdr(af, skb_network_header(skb), &iph);

    /* Bad... Do not break raw sockets */
    if (unlikely(skb->sk != NULL && hooknum == NF_INET_LOCAL_OUT &&
             af == AF_INET)) {
        struct sock *sk = skb->sk;
        struct inet_sock *inet = inet_sk(skb->sk);

        if (inet && sk->sk_family == PF_INET && inet->nodefrag)
            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(skb, &related, hooknum);

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

            if (related)
                return verdict;
            ip_vs_fill_iphdr(af, skb_network_header(skb), &iph);
        }

    /* Protocol supported? */
    pd = ip_vs_proto_data_get(net, iph.protocol);
    if (unlikely(!pd))
        return NF_ACCEPT;
    pp = pd->pp;
    /*
     * Check if the packet belongs to an existing connection entry
     */
    cp = pp->conn_in_get(af, skb, &iph, iph.len, 0);

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

        if (!pp->conn_schedule(af, skb, pd, &v, &cp))
            return v;
    }

    if (unlikely(!cp)) {
        /* sorry, all this trouble for a no-hit :) */
        IP_VS_DBG_PKT(12, af, pp, skb, 0,
                  "ip_vs_in: packet continues traversal as normal");
        return NF_ACCEPT;
    }

    IP_VS_DBG_PKT(11, af, pp, skb, 0, "Incoming packet");
    ipvs = net_ipvs(net);
    /* Check the server status */
    if (cp->dest && !(cp->dest->flags & IP_VS_DEST_F_AVAILABLE)) {
        /* the destination server is not available */

        if (sysctl_expire_nodest_conn(ipvs)) {
            /* try to expire the connection immediately */
            ip_vs_conn_expire_now(cp);
        }
        /* don't restart its timer, and silently
           drop the packet. */
        __ip_vs_conn_put(cp);
        return NF_DROP;
    }

    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);
        /* 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_add_return(1, &cp->in_pkts);

    if (ipvs->sync_state & IP_VS_STATE_MASTER)
        ip_vs_sync_conn(net, cp, pkts);

    ip_vs_conn_put(cp);
    return ret;
}

/*
 *  AF_INET handler in NF_INET_LOCAL_IN chain
 *  Schedule and forward packets from remote clients
 */
static unsigned int
ip_vs_remote_request4(unsigned int hooknum, struct sk_buff *skb,
              const struct net_device *in,
              const struct net_device *out,
              int (*okfn)(struct sk_buff *))
{
    return ip_vs_in(hooknum, skb, AF_INET);
}

/*
 *  AF_INET handler in NF_INET_LOCAL_OUT chain
 *  Schedule and forward packets from local clients
 */
static unsigned int
ip_vs_local_request4(unsigned int hooknum, struct sk_buff *skb,
             const struct net_device *in, const struct net_device *out,
             int (*okfn)(struct sk_buff *))
{
    unsigned int verdict;

    /* Disable BH in LOCAL_OUT until all places are fixed */
    local_bh_disable();
    verdict = ip_vs_in(hooknum, skb, AF_INET);
    local_bh_enable();
    return verdict;
}

#ifdef CONFIG_IP_VS_IPV6

/*
 *  AF_INET6 handler in NF_INET_LOCAL_IN chain
 *  Schedule and forward packets from remote clients
 */
static unsigned int
ip_vs_remote_request6(unsigned int hooknum, struct sk_buff *skb,
              const struct net_device *in,
              const struct net_device *out,
              int (*okfn)(struct sk_buff *))
{
    return ip_vs_in(hooknum, skb, AF_INET6);
}

/*
 *  AF_INET6 handler in NF_INET_LOCAL_OUT chain
 *  Schedule and forward packets from local clients
 */
static unsigned int
ip_vs_local_request6(unsigned int hooknum, struct sk_buff *skb,
             const struct net_device *in, const struct net_device *out,
             int (*okfn)(struct sk_buff *))
{
    unsigned int verdict;

    /* Disable BH in LOCAL_OUT until all places are fixed */
    local_bh_disable();
    verdict = ip_vs_in(hooknum, skb, AF_INET6);
    local_bh_enable();
    return verdict;
}

#endif


/*
 *  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(unsigned int hooknum, struct sk_buff *skb,
           const struct net_device *in, const struct net_device *out,
           int (*okfn)(struct sk_buff *))
{
    int r;
    struct net *net;

    if (ip_hdr(skb)->protocol != IPPROTO_ICMP)
        return NF_ACCEPT;

    /* ipvs enabled in this netns ? */
    net = skb_net(skb);
    if (!net_ipvs(net)->enable)
        return NF_ACCEPT;

    return ip_vs_in_icmp(skb, &r, hooknum);
}

#ifdef CONFIG_IP_VS_IPV6
static unsigned int
ip_vs_forward_icmp_v6(unsigned int hooknum, struct sk_buff *skb,
              const struct net_device *in, const struct net_device *out,
              int (*okfn)(struct sk_buff *))
{
    int r;
    struct net *net;

    if (ipv6_hdr(skb)->nexthdr != IPPROTO_ICMPV6)
        return NF_ACCEPT;

    /* ipvs enabled in this netns ? */
    net = skb_net(skb);
    if (!net_ipvs(net)->enable)
        return NF_ACCEPT;

    return ip_vs_in_icmp_v6(skb, &r, hooknum);
}
#endif


static struct nf_hook_ops ip_vs_ops[] __read_mostly = {
    /* After packet filtering, change source only for VS/NAT */
    {
        .hook       = ip_vs_reply4,
        .owner      = THIS_MODULE,
        .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_remote_request4,
        .owner      = THIS_MODULE,
        .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_local_reply4,
        .owner      = THIS_MODULE,
        .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_local_request4,
        .owner      = THIS_MODULE,
        .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,
        .owner      = THIS_MODULE,
        .pf     = NFPROTO_IPV4,
        .hooknum    = NF_INET_FORWARD,
        .priority   = 99,
    },
    /* After packet filtering, change source only for VS/NAT */
    {
        .hook       = ip_vs_reply4,
        .owner      = THIS_MODULE,
        .pf     = NFPROTO_IPV4,
        .hooknum    = NF_INET_FORWARD,
        .priority   = 100,
    },
#ifdef CONFIG_IP_VS_IPV6
    /* After packet filtering, change source only for VS/NAT */
    {
        .hook       = ip_vs_reply6,
        .owner      = THIS_MODULE,
        .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_remote_request6,
        .owner      = THIS_MODULE,
        .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_local_reply6,
        .owner      = THIS_MODULE,
        .pf     = NFPROTO_IPV4,
        .hooknum    = NF_INET_LOCAL_OUT,
        .priority   = NF_IP6_PRI_NAT_DST + 1,
    },
    /* After mangle, schedule and forward local requests */
    {
        .hook       = ip_vs_local_request6,
        .owner      = THIS_MODULE,
        .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_v6,
        .owner      = THIS_MODULE,
        .pf     = NFPROTO_IPV6,
        .hooknum    = NF_INET_FORWARD,
        .priority   = 99,
    },
    /* After packet filtering, change source only for VS/NAT */
    {
        .hook       = ip_vs_reply6,
        .owner      = THIS_MODULE,
        .pf     = NFPROTO_IPV6,
        .hooknum    = NF_INET_FORWARD,
        .priority   = 100,
    },
#endif
};
/*
 *  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 registerd */
    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(net) < 0)
        goto estimator_fail;

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

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

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

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

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

    printk(KERN_INFO "IPVS: Creating netns size=%zu id=%d\n",
             sizeof(struct netns_ipvs), ipvs->gen);
    return 0;
/*
 * Error handling
 */

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

static void __net_exit __ip_vs_cleanup(struct net *net)
{
    ip_vs_service_net_cleanup(net); /* ip_vs_flush() with locks */
    ip_vs_conn_net_cleanup(net);
    ip_vs_app_net_cleanup(net);
    ip_vs_protocol_net_cleanup(net);
    ip_vs_control_net_cleanup(net);
    ip_vs_estimator_net_cleanup(net);
    IP_VS_DBG(2, "ipvs netns %d released\n", net_ipvs(net)->gen);
    net->ipvs = NULL;
}

static void __net_exit __ip_vs_dev_cleanup(struct net *net)
{
    EnterFunction(2);
    net_ipvs(net)->enable = 0;  /* Disable packet reception */
    smp_wmb();
    ip_vs_sync_net_cleanup(net);
    LeaveFunction(2);
}

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

static struct pernet_operations ipvs_core_dev_ops = {
    .exit = __ip_vs_dev_cleanup,
};

/*
 *  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 = nf_register_hooks(ip_vs_ops, ARRAY_SIZE(ip_vs_ops));
    if (ret < 0) {
        pr_err("can't register hooks.\n");
        goto cleanup_dev;
    }

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

    pr_info("ipvs loaded.\n");

    return ret;

cleanup_hooks:
    nf_unregister_hooks(ip_vs_ops, ARRAY_SIZE(ip_vs_ops));
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();
    nf_unregister_hooks(ip_vs_ops, ARRAY_SIZE(ip_vs_ops));
    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();
    pr_info("ipvs unloaded.\n");
}

module_init(ip_vs_init);
module_exit(ip_vs_cleanup);
MODULE_LICENSE("GPL");