/*
 * ip_vs_xmit.c: various packet transmitters for IPVS
 *
 * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
 *              Julian Anastasov <ja@ssi.bg>
 *
 *              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.
 *
 * Changes:
 *
 * Description of forwarding methods:
 * - all transmitters are called from LOCAL_IN (remote clients) and
 * LOCAL_OUT (local clients) but for ICMP can be called from FORWARD
 * - not all connections have destination server, for example,
 * connections in backup server when fwmark is used
 * - bypass connections use daddr from packet
 * LOCAL_OUT rules:
 * - skb->dev is NULL, skb->protocol is not set (both are set in POST_ROUTING)
 * - skb->pkt_type is not set yet
 * - the only place where we can see skb->sk != NULL
 */

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

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/tcp.h>                  /* for tcphdr */
#include <net/ip.h>
#include <net/tcp.h>                    /* for csum_tcpudp_magic */
#include <net/udp.h>
#include <net/icmp.h>                   /* for icmp_send */
#include <net/route.h>                  /* for ip_route_output */
#include <net/ipv6.h>
#include <net/ip6_route.h>
#include <net/addrconf.h>
#include <linux/icmpv6.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>

#include <net/ip_vs.h>


/*
 *      Destination cache to speed up outgoing route lookup
 */
static inline void
__ip_vs_dst_set(struct ip_vs_dest *dest, u32 rtos, struct dst_entry *dst,
                u32 dst_cookie)
{
        struct dst_entry *old_dst;

        old_dst = dest->dst_cache;
        dest->dst_cache = dst;
        dest->dst_rtos = rtos;
        dest->dst_cookie = dst_cookie;
        dst_release(old_dst);
}

static inline struct dst_entry *
__ip_vs_dst_check(struct ip_vs_dest *dest, u32 rtos)
{
        struct dst_entry *dst = dest->dst_cache;

        if (!dst)
                return NULL;
        if ((dst->obsolete || rtos != dest->dst_rtos) &&
            dst->ops->check(dst, dest->dst_cookie) == NULL) {
                dest->dst_cache = NULL;
                dst_release(dst);
                return NULL;
        }
        dst_hold(dst);
        return dst;
}

/*
 * Get route to destination or remote server
 * rt_mode: flags, &1=Allow local dest, &2=Allow non-local dest,
 *          &4=Allow redirect from remote daddr to local
 */
static struct rtable *
__ip_vs_get_out_rt(struct sk_buff *skb, struct ip_vs_dest *dest,
                   __be32 daddr, u32 rtos, int rt_mode)
{
        struct net *net = dev_net(skb_dst(skb)->dev);
        struct rtable *rt;                      /* Route to the other host */
        struct rtable *ort;                     /* Original route */
        int local;

        if (dest) {
                spin_lock(&dest->dst_lock);
                if (!(rt = (struct rtable *)
                      __ip_vs_dst_check(dest, rtos))) {
                        struct flowi fl = {
                                .fl4_dst = dest->addr.ip,
                                .fl4_tos = rtos,
                        };

                        if (ip_route_output_key(net, &rt, &fl)) {
                                spin_unlock(&dest->dst_lock);
                                IP_VS_DBG_RL("ip_route_output error, dest: %pI4\n",
                                             &dest->addr.ip);
                                return NULL;
                        }
                        __ip_vs_dst_set(dest, rtos, dst_clone(&rt->dst), 0);
                        IP_VS_DBG(10, "new dst %pI4, refcnt=%d, rtos=%X\n",
                                  &dest->addr.ip,
                                  atomic_read(&rt->dst.__refcnt), rtos);
                }
                spin_unlock(&dest->dst_lock);
        } else {
                struct flowi fl = {
                        .fl4_dst = daddr,
                        .fl4_tos = rtos,
                };

                if (ip_route_output_key(net, &rt, &fl)) {
                        IP_VS_DBG_RL("ip_route_output error, dest: %pI4\n",
                                     &daddr);
                        return NULL;
                }
        }

        local = rt->rt_flags & RTCF_LOCAL;
        if (!((local ? 1 : 2) & rt_mode)) {
                IP_VS_DBG_RL("Stopping traffic to %s address, dest: %pI4\n",
                             (rt->rt_flags & RTCF_LOCAL) ?
                             "local":"non-local", &rt->rt_dst);
                ip_rt_put(rt);
                return NULL;
        }
        if (local && !(rt_mode & 4) && !((ort = skb_rtable(skb)) &&
                                         ort->rt_flags & RTCF_LOCAL)) {
                IP_VS_DBG_RL("Redirect from non-local address %pI4 to local "
                             "requires NAT method, dest: %pI4\n",
                             &ip_hdr(skb)->daddr, &rt->rt_dst);
                ip_rt_put(rt);
                return NULL;
        }
        if (unlikely(!local && ipv4_is_loopback(ip_hdr(skb)->saddr))) {
                IP_VS_DBG_RL("Stopping traffic from loopback address %pI4 "
                             "to non-local address, dest: %pI4\n",
                             &ip_hdr(skb)->saddr, &rt->rt_dst);
                ip_rt_put(rt);
                return NULL;
        }

        return rt;
}

/* Reroute packet to local IPv4 stack after DNAT */
static int
__ip_vs_reroute_locally(struct sk_buff *skb)
{
        struct rtable *rt = skb_rtable(skb);
        struct net_device *dev = rt->dst.dev;
        struct net *net = dev_net(dev);
        struct iphdr *iph = ip_hdr(skb);

        if (rt_is_input_route(rt)) {
                unsigned long orefdst = skb->_skb_refdst;

                if (ip_route_input(skb, iph->daddr, iph->saddr,
                                   iph->tos, skb->dev))
                        return 0;
                refdst_drop(orefdst);
        } else {
                struct flowi fl = {
                        .fl4_dst = iph->daddr,
                        .fl4_src = iph->saddr,
                        .fl4_tos = RT_TOS(iph->tos),
                        .mark = skb->mark,
                };
                struct rtable *rt;

                if (ip_route_output_key(net, &rt, &fl))
                        return 0;
                if (!(rt->rt_flags & RTCF_LOCAL)) {
                        ip_rt_put(rt);
                        return 0;
                }
                /* Drop old route. */
                skb_dst_drop(skb);
                skb_dst_set(skb, &rt->dst);
        }
        return 1;
}

#ifdef CONFIG_IP_VS_IPV6

static inline int __ip_vs_is_local_route6(struct rt6_info *rt)
{
        return rt->rt6i_dev && rt->rt6i_dev->flags & IFF_LOOPBACK;
}

static struct dst_entry *
__ip_vs_route_output_v6(struct net *net, struct in6_addr *daddr,
                        struct in6_addr *ret_saddr, int do_xfrm)
{
        struct dst_entry *dst;
        struct flowi fl = {
                .fl6_dst = *daddr,
        };

        dst = ip6_route_output(net, NULL, &fl);
        if (dst->error)
                goto out_err;
        if (!ret_saddr)
                return dst;
        if (ipv6_addr_any(&fl.fl6_src) &&
            ipv6_dev_get_saddr(net, ip6_dst_idev(dst)->dev,
                               &fl.fl6_dst, 0, &fl.fl6_src) < 0)
                goto out_err;
        if (do_xfrm && xfrm_lookup(net, &dst, &fl, NULL, 0) < 0)
                goto out_err;
        ipv6_addr_copy(ret_saddr, &fl.fl6_src);
        return dst;

out_err:
        dst_release(dst);
        IP_VS_DBG_RL("ip6_route_output error, dest: %pI6\n", daddr);
        return NULL;
}

/*
 * Get route to destination or remote server
 * rt_mode: flags, &1=Allow local dest, &2=Allow non-local dest,
 *          &4=Allow redirect from remote daddr to local
 */
static struct rt6_info *
__ip_vs_get_out_rt_v6(struct sk_buff *skb, struct ip_vs_dest *dest,
                      struct in6_addr *daddr, struct in6_addr *ret_saddr,
                      int do_xfrm, int rt_mode)
{
        struct net *net = dev_net(skb_dst(skb)->dev);
        struct rt6_info *rt;                    /* Route to the other host */
        struct rt6_info *ort;                   /* Original route */
        struct dst_entry *dst;
        int local;

        if (dest) {
                spin_lock(&dest->dst_lock);
                rt = (struct rt6_info *)__ip_vs_dst_check(dest, 0);
                if (!rt) {
                        u32 cookie;

                        dst = __ip_vs_route_output_v6(net, &dest->addr.in6,
                                                      &dest->dst_saddr,
                                                      do_xfrm);
                        if (!dst) {
                                spin_unlock(&dest->dst_lock);
                                return NULL;
                        }
                        rt = (struct rt6_info *) dst;
                        cookie = rt->rt6i_node ? rt->rt6i_node->fn_sernum : 0;
                        __ip_vs_dst_set(dest, 0, dst_clone(&rt->dst), cookie);
                        IP_VS_DBG(10, "new dst %pI6, src %pI6, refcnt=%d\n",
                                  &dest->addr.in6, &dest->dst_saddr,
                                  atomic_read(&rt->dst.__refcnt));
                }
                if (ret_saddr)
                        ipv6_addr_copy(ret_saddr, &dest->dst_saddr);
                spin_unlock(&dest->dst_lock);
        } else {
                dst = __ip_vs_route_output_v6(net, daddr, ret_saddr, do_xfrm);
                if (!dst)
                        return NULL;
                rt = (struct rt6_info *) dst;
        }

        local = __ip_vs_is_local_route6(rt);
        if (!((local ? 1 : 2) & rt_mode)) {
                IP_VS_DBG_RL("Stopping traffic to %s address, dest: %pI6\n",
                             local ? "local":"non-local", daddr);
                dst_release(&rt->dst);
                return NULL;
        }
        if (local && !(rt_mode & 4) &&
            !((ort = (struct rt6_info *) skb_dst(skb)) &&
              __ip_vs_is_local_route6(ort))) {
                IP_VS_DBG_RL("Redirect from non-local address %pI6 to local "
                             "requires NAT method, dest: %pI6\n",
                             &ipv6_hdr(skb)->daddr, daddr);
                dst_release(&rt->dst);
                return NULL;
        }
        if (unlikely(!local && (!skb->dev || skb->dev->flags & IFF_LOOPBACK) &&
                     ipv6_addr_type(&ipv6_hdr(skb)->saddr) &
                                    IPV6_ADDR_LOOPBACK)) {
                IP_VS_DBG_RL("Stopping traffic from loopback address %pI6 "
                             "to non-local address, dest: %pI6\n",
                             &ipv6_hdr(skb)->saddr, daddr);
                dst_release(&rt->dst);
                return NULL;
        }

        return rt;
}
#endif


/*
 *      Release dest->dst_cache before a dest is removed
 */
void
ip_vs_dst_reset(struct ip_vs_dest *dest)
{
        struct dst_entry *old_dst;

        old_dst = dest->dst_cache;
        dest->dst_cache = NULL;
        dst_release(old_dst);
}

#define IP_VS_XMIT_TUNNEL(skb, cp)                              \
({                                                              \
        int __ret = NF_ACCEPT;                                  \
                                                                \
        (skb)->ipvs_property = 1;                               \
        if (unlikely((cp)->flags & IP_VS_CONN_F_NFCT))          \
                __ret = ip_vs_confirm_conntrack(skb, cp);       \
        if (__ret == NF_ACCEPT) {                               \
                nf_reset(skb);                                  \
                skb_forward_csum(skb);                          \
        }                                                       \
        __ret;                                                  \
})

#define IP_VS_XMIT_NAT(pf, skb, cp, local)              \
do {                                                    \
        (skb)->ipvs_property = 1;                       \
        if (likely(!((cp)->flags & IP_VS_CONN_F_NFCT))) \
                ip_vs_notrack(skb);                     \
        else                                            \
                ip_vs_update_conntrack(skb, cp, 1);     \
        if (local)                                      \
                return NF_ACCEPT;                       \
        skb_forward_csum(skb);                          \
        NF_HOOK(pf, NF_INET_LOCAL_OUT, (skb), NULL,     \
                skb_dst(skb)->dev, dst_output);         \
} while (0)

#define IP_VS_XMIT(pf, skb, cp, local)                  \
do {                                                    \
        (skb)->ipvs_property = 1;                       \
        if (likely(!((cp)->flags & IP_VS_CONN_F_NFCT))) \
                ip_vs_notrack(skb);                     \
        if (local)                                      \
                return NF_ACCEPT;                       \
        skb_forward_csum(skb);                          \
        NF_HOOK(pf, NF_INET_LOCAL_OUT, (skb), NULL,     \
                skb_dst(skb)->dev, dst_output);         \
} while (0)


/*
 *      NULL transmitter (do nothing except return NF_ACCEPT)
 */
int
ip_vs_null_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
                struct ip_vs_protocol *pp)
{
        /* we do not touch skb and do not need pskb ptr */
        IP_VS_XMIT(NFPROTO_IPV4, skb, cp, 1);
}


/*
 *      Bypass transmitter
 *      Let packets bypass the destination when the destination is not
 *      available, it may be only used in transparent cache cluster.
 */
int
ip_vs_bypass_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
                  struct ip_vs_protocol *pp)
{
        struct rtable *rt;                      /* Route to the other host */
        struct iphdr  *iph = ip_hdr(skb);
        int    mtu;

        EnterFunction(10);

        if (!(rt = __ip_vs_get_out_rt(skb, NULL, iph->daddr,
                                      RT_TOS(iph->tos), 2)))
                goto tx_error_icmp;

        /* MTU checking */
        mtu = dst_mtu(&rt->dst);
        if ((skb->len > mtu) && (iph->frag_off & htons(IP_DF))) {
                ip_rt_put(rt);
                icmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));
                IP_VS_DBG_RL("%s(): frag needed\n", __func__);
                goto tx_error;
        }

        /*
         * Call ip_send_check because we are not sure it is called
         * after ip_defrag. Is copy-on-write needed?
         */
        if (unlikely((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)) {
                ip_rt_put(rt);
                return NF_STOLEN;
        }
        ip_send_check(ip_hdr(skb));

        /* drop old route */
        skb_dst_drop(skb);
        skb_dst_set(skb, &rt->dst);

        /* Another hack: avoid icmp_send in ip_fragment */
        skb->local_df = 1;

        IP_VS_XMIT(NFPROTO_IPV4, skb, cp, 0);

        LeaveFunction(10);
        return NF_STOLEN;

 tx_error_icmp:
        dst_link_failure(skb);
 tx_error:
        kfree_skb(skb);
        LeaveFunction(10);
        return NF_STOLEN;
}

#ifdef CONFIG_IP_VS_IPV6
int
ip_vs_bypass_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
                     struct ip_vs_protocol *pp)
{
        struct rt6_info *rt;                    /* Route to the other host */
        struct ipv6hdr  *iph = ipv6_hdr(skb);
        int    mtu;

        EnterFunction(10);

        if (!(rt = __ip_vs_get_out_rt_v6(skb, NULL, &iph->daddr, NULL, 0, 2)))
                goto tx_error_icmp;

        /* MTU checking */
        mtu = dst_mtu(&rt->dst);
        if (skb->len > mtu) {
                if (!skb->dev) {
                        struct net *net = dev_net(skb_dst(skb)->dev);

                        skb->dev = net->loopback_dev;
                }
                icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
                dst_release(&rt->dst);
                IP_VS_DBG_RL("%s(): frag needed\n", __func__);
                goto tx_error;
        }

        /*
         * Call ip_send_check because we are not sure it is called
         * after ip_defrag. Is copy-on-write needed?
         */
        skb = skb_share_check(skb, GFP_ATOMIC);
        if (unlikely(skb == NULL)) {
                dst_release(&rt->dst);
                return NF_STOLEN;
        }

        /* drop old route */
        skb_dst_drop(skb);
        skb_dst_set(skb, &rt->dst);

        /* Another hack: avoid icmp_send in ip_fragment */
        skb->local_df = 1;

        IP_VS_XMIT(NFPROTO_IPV6, skb, cp, 0);

        LeaveFunction(10);
        return NF_STOLEN;

 tx_error_icmp:
        dst_link_failure(skb);
 tx_error:
        kfree_skb(skb);
        LeaveFunction(10);
        return NF_STOLEN;
}
#endif

/*
 *      NAT transmitter (only for outside-to-inside nat forwarding)
 *      Not used for related ICMP
 */
int
ip_vs_nat_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
               struct ip_vs_protocol *pp)
{
        struct rtable *rt;              /* Route to the other host */
        int mtu;
        struct iphdr *iph = ip_hdr(skb);
        int local;

        EnterFunction(10);

        /* check if it is a connection of no-client-port */
        if (unlikely(cp->flags & IP_VS_CONN_F_NO_CPORT)) {
                __be16 _pt, *p;
                p = skb_header_pointer(skb, iph->ihl*4, sizeof(_pt), &_pt);
                if (p == NULL)
                        goto tx_error;
                ip_vs_conn_fill_cport(cp, *p);
                IP_VS_DBG(10, "filled cport=%d\n", ntohs(*p));
        }

        if (!(rt = __ip_vs_get_out_rt(skb, cp->dest, cp->daddr.ip,
                                      RT_TOS(iph->tos), 1|2|4)))
                goto tx_error_icmp;
        local = rt->rt_flags & RTCF_LOCAL;
        /*
         * Avoid duplicate tuple in reply direction for NAT traffic
         * to local address when connection is sync-ed
         */
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
        if (cp->flags & IP_VS_CONN_F_SYNC && local) {
                enum ip_conntrack_info ctinfo;
                struct nf_conn *ct = ct = nf_ct_get(skb, &ctinfo);

                if (ct && !nf_ct_is_untracked(ct)) {
                        IP_VS_DBG_RL_PKT(10, AF_INET, pp, skb, 0,
                                         "ip_vs_nat_xmit(): "
                                         "stopping DNAT to local address");
                        goto tx_error_put;
                }
        }
#endif

        /* From world but DNAT to loopback address? */
        if (local && ipv4_is_loopback(rt->rt_dst) &&
            rt_is_input_route(skb_rtable(skb))) {
                IP_VS_DBG_RL_PKT(1, AF_INET, pp, skb, 0, "ip_vs_nat_xmit(): "
                                 "stopping DNAT to loopback address");
                goto tx_error_put;
        }

        /* MTU checking */
        mtu = dst_mtu(&rt->dst);
        if ((skb->len > mtu) && (iph->frag_off & htons(IP_DF))) {
                icmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));
                IP_VS_DBG_RL_PKT(0, AF_INET, pp, skb, 0,
                                 "ip_vs_nat_xmit(): frag needed for");
                goto tx_error_put;
        }

        /* copy-on-write the packet before mangling it */
        if (!skb_make_writable(skb, sizeof(struct iphdr)))
                goto tx_error_put;

        if (skb_cow(skb, rt->dst.dev->hard_header_len))
                goto tx_error_put;

        /* mangle the packet */
        if (pp->dnat_handler && !pp->dnat_handler(skb, pp, cp))
                goto tx_error_put;
        ip_hdr(skb)->daddr = cp->daddr.ip;
        ip_send_check(ip_hdr(skb));

        if (!local) {
                /* drop old route */
                skb_dst_drop(skb);
                skb_dst_set(skb, &rt->dst);
        } else {
                ip_rt_put(rt);
                /*
                 * Some IPv4 replies get local address from routes,
                 * not from iph, so while we DNAT after routing
                 * we need this second input/output route.
                 */
                if (!__ip_vs_reroute_locally(skb))
                        goto tx_error;
        }

        IP_VS_DBG_PKT(10, AF_INET, pp, skb, 0, "After DNAT");

        /* FIXME: when application helper enlarges the packet and the length
           is larger than the MTU of outgoing device, there will be still
           MTU problem. */

        /* Another hack: avoid icmp_send in ip_fragment */
        skb->local_df = 1;

        IP_VS_XMIT_NAT(NFPROTO_IPV4, skb, cp, local);

        LeaveFunction(10);
        return NF_STOLEN;

  tx_error_icmp:
        dst_link_failure(skb);
  tx_error:
        kfree_skb(skb);
        LeaveFunction(10);
        return NF_STOLEN;
  tx_error_put:
        ip_rt_put(rt);
        goto tx_error;
}

#ifdef CONFIG_IP_VS_IPV6
int
ip_vs_nat_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
                  struct ip_vs_protocol *pp)
{
        struct rt6_info *rt;            /* Route to the other host */
        int mtu;
        int local;

        EnterFunction(10);

        /* check if it is a connection of no-client-port */
        if (unlikely(cp->flags & IP_VS_CONN_F_NO_CPORT)) {
                __be16 _pt, *p;
                p = skb_header_pointer(skb, sizeof(struct ipv6hdr),
                                       sizeof(_pt), &_pt);
                if (p == NULL)
                        goto tx_error;
                ip_vs_conn_fill_cport(cp, *p);
                IP_VS_DBG(10, "filled cport=%d\n", ntohs(*p));
        }

        if (!(rt = __ip_vs_get_out_rt_v6(skb, cp->dest, &cp->daddr.in6, NULL,
                                         0, 1|2|4)))
                goto tx_error_icmp;
        local = __ip_vs_is_local_route6(rt);
        /*
         * Avoid duplicate tuple in reply direction for NAT traffic
         * to local address when connection is sync-ed
         */
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
        if (cp->flags & IP_VS_CONN_F_SYNC && local) {
                enum ip_conntrack_info ctinfo;
                struct nf_conn *ct = ct = nf_ct_get(skb, &ctinfo);

                if (ct && !nf_ct_is_untracked(ct)) {
                        IP_VS_DBG_RL_PKT(10, AF_INET6, pp, skb, 0,
                                         "ip_vs_nat_xmit_v6(): "
                                         "stopping DNAT to local address");
                        goto tx_error_put;
                }
        }
#endif

        /* From world but DNAT to loopback address? */
        if (local && skb->dev && !(skb->dev->flags & IFF_LOOPBACK) &&
            ipv6_addr_type(&rt->rt6i_dst.addr) & IPV6_ADDR_LOOPBACK) {
                IP_VS_DBG_RL_PKT(1, AF_INET6, pp, skb, 0,
                                 "ip_vs_nat_xmit_v6(): "
                                 "stopping DNAT to loopback address");
                goto tx_error_put;
        }

        /* MTU checking */
        mtu = dst_mtu(&rt->dst);
        if (skb->len > mtu) {
                if (!skb->dev) {
                        struct net *net = dev_net(skb_dst(skb)->dev);

                        skb->dev = net->loopback_dev;
                }
                icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
                IP_VS_DBG_RL_PKT(0, AF_INET6, pp, skb, 0,
                                 "ip_vs_nat_xmit_v6(): frag needed for");
                goto tx_error_put;
        }

        /* copy-on-write the packet before mangling it */
        if (!skb_make_writable(skb, sizeof(struct ipv6hdr)))
                goto tx_error_put;

        if (skb_cow(skb, rt->dst.dev->hard_header_len))
                goto tx_error_put;

        /* mangle the packet */
        if (pp->dnat_handler && !pp->dnat_handler(skb, pp, cp))
                goto tx_error;
        ipv6_addr_copy(&ipv6_hdr(skb)->daddr, &cp->daddr.in6);

        if (!local || !skb->dev) {
                /* drop the old route when skb is not shared */
                skb_dst_drop(skb);
                skb_dst_set(skb, &rt->dst);
        } else {
                /* destined to loopback, do we need to change route? */
                dst_release(&rt->dst);
        }

        IP_VS_DBG_PKT(10, AF_INET6, pp, skb, 0, "After DNAT");

        /* FIXME: when application helper enlarges the packet and the length
           is larger than the MTU of outgoing device, there will be still
           MTU problem. */

        /* Another hack: avoid icmp_send in ip_fragment */
        skb->local_df = 1;

        IP_VS_XMIT_NAT(NFPROTO_IPV6, skb, cp, local);

        LeaveFunction(10);
        return NF_STOLEN;

tx_error_icmp:
        dst_link_failure(skb);
tx_error:
        LeaveFunction(10);
        kfree_skb(skb);
        return NF_STOLEN;
tx_error_put:
        dst_release(&rt->dst);
        goto tx_error;
}
#endif


/*
 *   IP Tunneling transmitter
 *
 *   This function encapsulates the packet in a new IP packet, its
 *   destination will be set to cp->daddr. Most code of this function
 *   is taken from ipip.c.
 *
 *   It is used in VS/TUN cluster. The load balancer selects a real
 *   server from a cluster based on a scheduling algorithm,
 *   encapsulates the request packet and forwards it to the selected
 *   server. For example, all real servers are configured with
 *   "ifconfig tunl0 <Virtual IP Address> up". When the server receives
 *   the encapsulated packet, it will decapsulate the packet, processe
 *   the request and return the response packets directly to the client
 *   without passing the load balancer. This can greatly increase the
 *   scalability of virtual server.
 *
 *   Used for ANY protocol
 */
int
ip_vs_tunnel_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
                  struct ip_vs_protocol *pp)
{
        struct rtable *rt;                      /* Route to the other host */
        struct net_device *tdev;                /* Device to other host */
        struct iphdr  *old_iph = ip_hdr(skb);
        u8     tos = old_iph->tos;
        __be16 df = old_iph->frag_off;
        struct iphdr  *iph;                     /* Our new IP header */
        unsigned int max_headroom;              /* The extra header space needed */
        int    mtu;
        int ret;

        EnterFunction(10);

        if (!(rt = __ip_vs_get_out_rt(skb, cp->dest, cp->daddr.ip,
                                      RT_TOS(tos), 1|2)))
                goto tx_error_icmp;
        if (rt->rt_flags & RTCF_LOCAL) {
                ip_rt_put(rt);
                IP_VS_XMIT(NFPROTO_IPV4, skb, cp, 1);
        }

        tdev = rt->dst.dev;

        mtu = dst_mtu(&rt->dst) - sizeof(struct iphdr);
        if (mtu < 68) {
                IP_VS_DBG_RL("%s(): mtu less than 68\n", __func__);
                goto tx_error_put;
        }
        if (skb_dst(skb))
                skb_dst(skb)->ops->update_pmtu(skb_dst(skb), mtu);

        df |= (old_iph->frag_off & htons(IP_DF));

        if ((old_iph->frag_off & htons(IP_DF))
            && mtu < ntohs(old_iph->tot_len)) {
                icmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));
                IP_VS_DBG_RL("%s(): frag needed\n", __func__);
                goto tx_error_put;
        }

        /*
         * Okay, now see if we can stuff it in the buffer as-is.
         */
        max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(struct iphdr);

        if (skb_headroom(skb) < max_headroom
            || skb_cloned(skb) || skb_shared(skb)) {
                struct sk_buff *new_skb =
                        skb_realloc_headroom(skb, max_headroom);
                if (!new_skb) {
                        ip_rt_put(rt);
                        kfree_skb(skb);
                        IP_VS_ERR_RL("%s(): no memory\n", __func__);
                        return NF_STOLEN;
                }
                kfree_skb(skb);
                skb = new_skb;
                old_iph = ip_hdr(skb);
        }

        skb->transport_header = skb->network_header;

        /* fix old IP header checksum */
        ip_send_check(old_iph);

        skb_push(skb, sizeof(struct iphdr));
        skb_reset_network_header(skb);
        memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));

        /* drop old route */
        skb_dst_drop(skb);
        skb_dst_set(skb, &rt->dst);

        /*
         *      Push down and install the IPIP header.
         */
        iph                     =       ip_hdr(skb);
        iph->version            =       4;
        iph->ihl                =       sizeof(struct iphdr)>>2;
        iph->frag_off           =       df;
        iph->protocol           =       IPPROTO_IPIP;
        iph->tos                =       tos;
        iph->daddr              =       rt->rt_dst;
        iph->saddr              =       rt->rt_src;
        iph->ttl                =       old_iph->ttl;
        ip_select_ident(iph, &rt->dst, NULL);

        /* Another hack: avoid icmp_send in ip_fragment */
        skb->local_df = 1;

        ret = IP_VS_XMIT_TUNNEL(skb, cp);
        if (ret == NF_ACCEPT)
                ip_local_out(skb);
        else if (ret == NF_DROP)
                kfree_skb(skb);

        LeaveFunction(10);

        return NF_STOLEN;

  tx_error_icmp:
        dst_link_failure(skb);
  tx_error:
        kfree_skb(skb);
        LeaveFunction(10);
        return NF_STOLEN;
tx_error_put:
        ip_rt_put(rt);
        goto tx_error;
}

#ifdef CONFIG_IP_VS_IPV6
int
ip_vs_tunnel_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
                     struct ip_vs_protocol *pp)
{
        struct rt6_info *rt;            /* Route to the other host */
        struct in6_addr saddr;          /* Source for tunnel */
        struct net_device *tdev;        /* Device to other host */
        struct ipv6hdr  *old_iph = ipv6_hdr(skb);
        struct ipv6hdr  *iph;           /* Our new IP header */
        unsigned int max_headroom;      /* The extra header space needed */
        int    mtu;
        int ret;

        EnterFunction(10);

        if (!(rt = __ip_vs_get_out_rt_v6(skb, cp->dest, &cp->daddr.in6,
                                         &saddr, 1, 1|2)))
                goto tx_error_icmp;
        if (__ip_vs_is_local_route6(rt)) {
                dst_release(&rt->dst);
                IP_VS_XMIT(NFPROTO_IPV6, skb, cp, 1);
        }

        tdev = rt->dst.dev;

        mtu = dst_mtu(&rt->dst) - sizeof(struct ipv6hdr);
        if (mtu < IPV6_MIN_MTU) {
                IP_VS_DBG_RL("%s(): mtu less than %d\n", __func__,
                             IPV6_MIN_MTU);
                goto tx_error_put;
        }
        if (skb_dst(skb))
                skb_dst(skb)->ops->update_pmtu(skb_dst(skb), mtu);

        if (mtu < ntohs(old_iph->payload_len) + sizeof(struct ipv6hdr)) {
                if (!skb->dev) {
                        struct net *net = dev_net(skb_dst(skb)->dev);

                        skb->dev = net->loopback_dev;
                }
                icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
                IP_VS_DBG_RL("%s(): frag needed\n", __func__);
                goto tx_error_put;
        }

        /*
         * Okay, now see if we can stuff it in the buffer as-is.
         */
        max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(struct ipv6hdr);

        if (skb_headroom(skb) < max_headroom
            || skb_cloned(skb) || skb_shared(skb)) {
                struct sk_buff *new_skb =
                        skb_realloc_headroom(skb, max_headroom);
                if (!new_skb) {
                        dst_release(&rt->dst);
                        kfree_skb(skb);
                        IP_VS_ERR_RL("%s(): no memory\n", __func__);
                        return NF_STOLEN;
                }
                kfree_skb(skb);
                skb = new_skb;
                old_iph = ipv6_hdr(skb);
        }

        skb->transport_header = skb->network_header;

        skb_push(skb, sizeof(struct ipv6hdr));
        skb_reset_network_header(skb);
        memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));

        /* drop old route */
        skb_dst_drop(skb);
        skb_dst_set(skb, &rt->dst);

        /*
         *      Push down and install the IPIP header.
         */
        iph                     =       ipv6_hdr(skb);
        iph->version            =       6;
        iph->nexthdr            =       IPPROTO_IPV6;
        iph->payload_len        =       old_iph->payload_len;
        be16_add_cpu(&iph->payload_len, sizeof(*old_iph));
        iph->priority           =       old_iph->priority;
        memset(&iph->flow_lbl, 0, sizeof(iph->flow_lbl));
        ipv6_addr_copy(&iph->daddr, &cp->daddr.in6);
        ipv6_addr_copy(&iph->saddr, &saddr);
        iph->hop_limit          =       old_iph->hop_limit;

        /* Another hack: avoid icmp_send in ip_fragment */
        skb->local_df = 1;

        ret = IP_VS_XMIT_TUNNEL(skb, cp);
        if (ret == NF_ACCEPT)
                ip6_local_out(skb);
        else if (ret == NF_DROP)
                kfree_skb(skb);

        LeaveFunction(10);

        return NF_STOLEN;

tx_error_icmp:
        dst_link_failure(skb);
tx_error:
        kfree_skb(skb);
        LeaveFunction(10);
        return NF_STOLEN;
tx_error_put:
        dst_release(&rt->dst);
        goto tx_error;
}
#endif


/*
 *      Direct Routing transmitter
 *      Used for ANY protocol
 */
int
ip_vs_dr_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
              struct ip_vs_protocol *pp)
{
        struct rtable *rt;                      /* Route to the other host */
        struct iphdr  *iph = ip_hdr(skb);
        int    mtu;

        EnterFunction(10);

        if (!(rt = __ip_vs_get_out_rt(skb, cp->dest, cp->daddr.ip,
                                      RT_TOS(iph->tos), 1|2)))
                goto tx_error_icmp;
        if (rt->rt_flags & RTCF_LOCAL) {
                ip_rt_put(rt);
                IP_VS_XMIT(NFPROTO_IPV4, skb, cp, 1);
        }

        /* MTU checking */
        mtu = dst_mtu(&rt->dst);
        if ((iph->frag_off & htons(IP_DF)) && skb->len > mtu) {
                icmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));
                ip_rt_put(rt);
                IP_VS_DBG_RL("%s(): frag needed\n", __func__);
                goto tx_error;
        }

        /*
         * Call ip_send_check because we are not sure it is called
         * after ip_defrag. Is copy-on-write needed?
         */
        if (unlikely((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)) {
                ip_rt_put(rt);
                return NF_STOLEN;
        }
        ip_send_check(ip_hdr(skb));

        /* drop old route */
        skb_dst_drop(skb);
        skb_dst_set(skb, &rt->dst);

        /* Another hack: avoid icmp_send in ip_fragment */
        skb->local_df = 1;

        IP_VS_XMIT(NFPROTO_IPV4, skb, cp, 0);

        LeaveFunction(10);
        return NF_STOLEN;

  tx_error_icmp:
        dst_link_failure(skb);
  tx_error:
        kfree_skb(skb);
        LeaveFunction(10);
        return NF_STOLEN;
}

#ifdef CONFIG_IP_VS_IPV6
int
ip_vs_dr_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
                 struct ip_vs_protocol *pp)
{
        struct rt6_info *rt;                    /* Route to the other host */
        int    mtu;

        EnterFunction(10);

        if (!(rt = __ip_vs_get_out_rt_v6(skb, cp->dest, &cp->daddr.in6, NULL,
                                         0, 1|2)))
                goto tx_error_icmp;
        if (__ip_vs_is_local_route6(rt)) {
                dst_release(&rt->dst);
                IP_VS_XMIT(NFPROTO_IPV6, skb, cp, 1);
        }

        /* MTU checking */
        mtu = dst_mtu(&rt->dst);
        if (skb->len > mtu) {
                if (!skb->dev) {
                        struct net *net = dev_net(skb_dst(skb)->dev);

                        skb->dev = net->loopback_dev;
                }
                icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
                dst_release(&rt->dst);
                IP_VS_DBG_RL("%s(): frag needed\n", __func__);
                goto tx_error;
        }

        /*
         * Call ip_send_check because we are not sure it is called
         * after ip_defrag. Is copy-on-write needed?
         */
        skb = skb_share_check(skb, GFP_ATOMIC);
        if (unlikely(skb == NULL)) {
                dst_release(&rt->dst);
                return NF_STOLEN;
        }

        /* drop old route */
        skb_dst_drop(skb);
        skb_dst_set(skb, &rt->dst);

        /* Another hack: avoid icmp_send in ip_fragment */
        skb->local_df = 1;

        IP_VS_XMIT(NFPROTO_IPV6, skb, cp, 0);

        LeaveFunction(10);
        return NF_STOLEN;

tx_error_icmp:
        dst_link_failure(skb);
tx_error:
        kfree_skb(skb);
        LeaveFunction(10);
        return NF_STOLEN;
}
#endif


/*
 *      ICMP packet transmitter
 *      called by the ip_vs_in_icmp
 */
int
ip_vs_icmp_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
                struct ip_vs_protocol *pp, int offset)
{
        struct rtable   *rt;    /* Route to the other host */
        int mtu;
        int rc;
        int local;

        EnterFunction(10);

        /* The ICMP packet for VS/TUN, VS/DR and LOCALNODE will be
           forwarded directly here, because there is no need to
           translate address/port back */
        if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ) {
                if (cp->packet_xmit)
                        rc = cp->packet_xmit(skb, cp, pp);
                else
                        rc = NF_ACCEPT;
                /* do not touch skb anymore */
                atomic_inc(&cp->in_pkts);
                goto out;
        }

        /*
         * mangle and send the packet here (only for VS/NAT)
         */

        if (!(rt = __ip_vs_get_out_rt(skb, cp->dest, cp->daddr.ip,
                                      RT_TOS(ip_hdr(skb)->tos), 1|2|4)))
                goto tx_error_icmp;
        local = rt->rt_flags & RTCF_LOCAL;

        /*
         * Avoid duplicate tuple in reply direction for NAT traffic
         * to local address when connection is sync-ed
         */
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
        if (cp->flags & IP_VS_CONN_F_SYNC && local) {
                enum ip_conntrack_info ctinfo;
                struct nf_conn *ct = ct = nf_ct_get(skb, &ctinfo);

                if (ct && !nf_ct_is_untracked(ct)) {
                        IP_VS_DBG(10, "%s(): "
                                  "stopping DNAT to local address %pI4\n",
                                  __func__, &cp->daddr.ip);
                        goto tx_error_put;
                }
        }
#endif

        /* From world but DNAT to loopback address? */
        if (local && ipv4_is_loopback(rt->rt_dst) &&
            rt_is_input_route(skb_rtable(skb))) {
                IP_VS_DBG(1, "%s(): "
                          "stopping DNAT to loopback %pI4\n",
                          __func__, &cp->daddr.ip);
                goto tx_error_put;
        }

        /* MTU checking */
        mtu = dst_mtu(&rt->dst);
        if ((skb->len > mtu) && (ip_hdr(skb)->frag_off & htons(IP_DF))) {
                icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
                IP_VS_DBG_RL("%s(): frag needed\n", __func__);
                goto tx_error_put;
        }

        /* copy-on-write the packet before mangling it */
        if (!skb_make_writable(skb, offset))
                goto tx_error_put;

        if (skb_cow(skb, rt->dst.dev->hard_header_len))
                goto tx_error_put;

        ip_vs_nat_icmp(skb, pp, cp, 0);

        if (!local) {
                /* drop the old route when skb is not shared */
                skb_dst_drop(skb);
                skb_dst_set(skb, &rt->dst);
        } else {
                ip_rt_put(rt);
                /*
                 * Some IPv4 replies get local address from routes,
                 * not from iph, so while we DNAT after routing
                 * we need this second input/output route.
                 */
                if (!__ip_vs_reroute_locally(skb))
                        goto tx_error;
        }

        /* Another hack: avoid icmp_send in ip_fragment */
        skb->local_df = 1;

        IP_VS_XMIT_NAT(NFPROTO_IPV4, skb, cp, local);

        rc = NF_STOLEN;
        goto out;

  tx_error_icmp:
        dst_link_failure(skb);
  tx_error:
        dev_kfree_skb(skb);
        rc = NF_STOLEN;
  out:
        LeaveFunction(10);
        return rc;
  tx_error_put:
        ip_rt_put(rt);
        goto tx_error;
}

#ifdef CONFIG_IP_VS_IPV6
int
ip_vs_icmp_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
                struct ip_vs_protocol *pp, int offset)
{
        struct rt6_info *rt;    /* Route to the other host */
        int mtu;
        int rc;
        int local;

        EnterFunction(10);

        /* The ICMP packet for VS/TUN, VS/DR and LOCALNODE will be
           forwarded directly here, because there is no need to
           translate address/port back */
        if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ) {
                if (cp->packet_xmit)
                        rc = cp->packet_xmit(skb, cp, pp);
                else
                        rc = NF_ACCEPT;
                /* do not touch skb anymore */
                atomic_inc(&cp->in_pkts);
                goto out;
        }

        /*
         * mangle and send the packet here (only for VS/NAT)
         */

        if (!(rt = __ip_vs_get_out_rt_v6(skb, cp->dest, &cp->daddr.in6, NULL,
                                         0, 1|2|4)))
                goto tx_error_icmp;

        local = __ip_vs_is_local_route6(rt);
        /*
         * Avoid duplicate tuple in reply direction for NAT traffic
         * to local address when connection is sync-ed
         */
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
        if (cp->flags & IP_VS_CONN_F_SYNC && local) {
                enum ip_conntrack_info ctinfo;
                struct nf_conn *ct = ct = nf_ct_get(skb, &ctinfo);

                if (ct && !nf_ct_is_untracked(ct)) {
                        IP_VS_DBG(10, "%s(): "
                                  "stopping DNAT to local address %pI6\n",
                                  __func__, &cp->daddr.in6);
                        goto tx_error_put;
                }
        }
#endif

        /* From world but DNAT to loopback address? */
        if (local && skb->dev && !(skb->dev->flags & IFF_LOOPBACK) &&
            ipv6_addr_type(&rt->rt6i_dst.addr) & IPV6_ADDR_LOOPBACK) {
                IP_VS_DBG(1, "%s(): "
                          "stopping DNAT to loopback %pI6\n",
                          __func__, &cp->daddr.in6);
                goto tx_error_put;
        }

        /* MTU checking */
        mtu = dst_mtu(&rt->dst);
        if (skb->len > mtu) {
                if (!skb->dev) {
                        struct net *net = dev_net(skb_dst(skb)->dev);

                        skb->dev = net->loopback_dev;
                }
                icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
                IP_VS_DBG_RL("%s(): frag needed\n", __func__);
                goto tx_error_put;
        }

        /* copy-on-write the packet before mangling it */
        if (!skb_make_writable(skb, offset))
                goto tx_error_put;

        if (skb_cow(skb, rt->dst.dev->hard_header_len))
                goto tx_error_put;

        ip_vs_nat_icmp_v6(skb, pp, cp, 0);

        if (!local || !skb->dev) {
                /* drop the old route when skb is not shared */
                skb_dst_drop(skb);
                skb_dst_set(skb, &rt->dst);
        } else {
                /* destined to loopback, do we need to change route? */
                dst_release(&rt->dst);
        }

        /* Another hack: avoid icmp_send in ip_fragment */
        skb->local_df = 1;

        IP_VS_XMIT_NAT(NFPROTO_IPV6, skb, cp, local);

        rc = NF_STOLEN;
        goto out;

tx_error_icmp:
        dst_link_failure(skb);
tx_error:
        dev_kfree_skb(skb);
        rc = NF_STOLEN;
out:
        LeaveFunction(10);
        return rc;
tx_error_put:
        dst_release(&rt->dst);
        goto tx_error;
}
#endif