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root/net/netfilter/ipvs/ip_vs_proto_tcp.c

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DEFINITIONS

This source file includes following definitions.
  1. tcp_conn_in_get
  2. tcp_conn_out_get
  3. tcp_conn_schedule
  4. tcp_fast_csum_update
  5. tcp_partial_csum_update
  6. tcp_snat_handler
  7. tcp_dnat_handler
  8. tcp_csum_check
  9. tcp_state_name
  10. tcp_timeout_change
  11. tcp_set_state_timeout
  12. tcp_state_idx
  13. set_tcp_state
  14. tcp_state_transition
  15. tcp_app_hashkey
  16. tcp_register_app
  17. tcp_unregister_app
  18. tcp_app_conn_bind
  19. ip_vs_tcp_conn_listen
  20. ip_vs_tcp_init
  21. ip_vs_tcp_exit

/*
 * ip_vs_proto_tcp.c:   TCP load balancing support 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:
 *
 */

#include <linux/kernel.h>
#include <linux/ip.h>
#include <linux/tcp.h>                  /* for tcphdr */
#include <net/ip.h>
#include <net/tcp.h>                    /* for csum_tcpudp_magic */
#include <net/ip6_checksum.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>

#include <net/ip_vs.h>


static struct ip_vs_conn *
tcp_conn_in_get(int af, const struct sk_buff *skb, struct ip_vs_protocol *pp,
                const struct ip_vs_iphdr *iph, unsigned int proto_off,
                int inverse)
{
        __be16 _ports[2], *pptr;

        pptr = skb_header_pointer(skb, proto_off, sizeof(_ports), _ports);
        if (pptr == NULL)
                return NULL;

        if (likely(!inverse)) {
                return ip_vs_conn_in_get(af, iph->protocol,
                                         &iph->saddr, pptr[0],
                                         &iph->daddr, pptr[1]);
        } else {
                return ip_vs_conn_in_get(af, iph->protocol,
                                         &iph->daddr, pptr[1],
                                         &iph->saddr, pptr[0]);
        }
}

static struct ip_vs_conn *
tcp_conn_out_get(int af, const struct sk_buff *skb, struct ip_vs_protocol *pp,
                 const struct ip_vs_iphdr *iph, unsigned int proto_off,
                 int inverse)
{
        __be16 _ports[2], *pptr;

        pptr = skb_header_pointer(skb, proto_off, sizeof(_ports), _ports);
        if (pptr == NULL)
                return NULL;

        if (likely(!inverse)) {
                return ip_vs_conn_out_get(af, iph->protocol,
                                          &iph->saddr, pptr[0],
                                          &iph->daddr, pptr[1]);
        } else {
                return ip_vs_conn_out_get(af, iph->protocol,
                                          &iph->daddr, pptr[1],
                                          &iph->saddr, pptr[0]);
        }
}


static int
tcp_conn_schedule(int af, struct sk_buff *skb, struct ip_vs_protocol *pp,
                  int *verdict, struct ip_vs_conn **cpp)
{
        struct ip_vs_service *svc;
        struct tcphdr _tcph, *th;
        struct ip_vs_iphdr iph;

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

        th = skb_header_pointer(skb, iph.len, sizeof(_tcph), &_tcph);
        if (th == NULL) {
                *verdict = NF_DROP;
                return 0;
        }

        if (th->syn &&
            (svc = ip_vs_service_get(af, skb->mark, iph.protocol, &iph.daddr,
                                     th->dest))) {
                if (ip_vs_todrop()) {
                        /*
                         * It seems that we are very loaded.
                         * We have to drop this packet :(
                         */
                        ip_vs_service_put(svc);
                        *verdict = NF_DROP;
                        return 0;
                }

                /*
                 * Let the virtual server select a real server for the
                 * incoming connection, and create a connection entry.
                 */
                *cpp = ip_vs_schedule(svc, skb);
                if (!*cpp) {
                        *verdict = ip_vs_leave(svc, skb, pp);
                        return 0;
                }
                ip_vs_service_put(svc);
        }
        return 1;
}


static inline void
tcp_fast_csum_update(int af, struct tcphdr *tcph,
                     const union nf_inet_addr *oldip,
                     const union nf_inet_addr *newip,
                     __be16 oldport, __be16 newport)
{
#ifdef CONFIG_IP_VS_IPV6
        if (af == AF_INET6)
                tcph->check =
                        csum_fold(ip_vs_check_diff16(oldip->ip6, newip->ip6,
                                         ip_vs_check_diff2(oldport, newport,
                                                ~csum_unfold(tcph->check))));
        else
#endif
        tcph->check =
                csum_fold(ip_vs_check_diff4(oldip->ip, newip->ip,
                                 ip_vs_check_diff2(oldport, newport,
                                                ~csum_unfold(tcph->check))));
}


static inline void
tcp_partial_csum_update(int af, struct tcphdr *tcph,
                     const union nf_inet_addr *oldip,
                     const union nf_inet_addr *newip,
                     __be16 oldlen, __be16 newlen)
{
#ifdef CONFIG_IP_VS_IPV6
        if (af == AF_INET6)
                tcph->check =
                        csum_fold(ip_vs_check_diff16(oldip->ip6, newip->ip6,
                                         ip_vs_check_diff2(oldlen, newlen,
                                                ~csum_unfold(tcph->check))));
        else
#endif
        tcph->check =
                csum_fold(ip_vs_check_diff4(oldip->ip, newip->ip,
                                ip_vs_check_diff2(oldlen, newlen,
                                                ~csum_unfold(tcph->check))));
}


static int
tcp_snat_handler(struct sk_buff *skb,
                 struct ip_vs_protocol *pp, struct ip_vs_conn *cp)
{
        struct tcphdr *tcph;
        unsigned int tcphoff;
        int oldlen;

#ifdef CONFIG_IP_VS_IPV6
        if (cp->af == AF_INET6)
                tcphoff = sizeof(struct ipv6hdr);
        else
#endif
                tcphoff = ip_hdrlen(skb);
        oldlen = skb->len - tcphoff;

        /* csum_check requires unshared skb */
        if (!skb_make_writable(skb, tcphoff+sizeof(*tcph)))
                return 0;

        if (unlikely(cp->app != NULL)) {
                /* Some checks before mangling */
                if (pp->csum_check && !pp->csum_check(cp->af, skb, pp))
                        return 0;

                /* Call application helper if needed */
                if (!ip_vs_app_pkt_out(cp, skb))
                        return 0;
        }

        tcph = (void *)skb_network_header(skb) + tcphoff;
        tcph->source = cp->vport;

        /* Adjust TCP checksums */
        if (skb->ip_summed == CHECKSUM_PARTIAL) {
                tcp_partial_csum_update(cp->af, tcph, &cp->daddr, &cp->vaddr,
                                        htonl(oldlen),
                                        htonl(skb->len - tcphoff));
        } else if (!cp->app) {
                /* Only port and addr are changed, do fast csum update */
                tcp_fast_csum_update(cp->af, tcph, &cp->daddr, &cp->vaddr,
                                     cp->dport, cp->vport);
                if (skb->ip_summed == CHECKSUM_COMPLETE)
                        skb->ip_summed = CHECKSUM_NONE;
        } else {
                /* full checksum calculation */
                tcph->check = 0;
                skb->csum = skb_checksum(skb, tcphoff, skb->len - tcphoff, 0);
#ifdef CONFIG_IP_VS_IPV6
                if (cp->af == AF_INET6)
                        tcph->check = csum_ipv6_magic(&cp->vaddr.in6,
                                                      &cp->caddr.in6,
                                                      skb->len - tcphoff,
                                                      cp->protocol, skb->csum);
                else
#endif
                        tcph->check = csum_tcpudp_magic(cp->vaddr.ip,
                                                        cp->caddr.ip,
                                                        skb->len - tcphoff,
                                                        cp->protocol,
                                                        skb->csum);

                IP_VS_DBG(11, "O-pkt: %s O-csum=%d (+%zd)\n",
                          pp->name, tcph->check,
                          (char*)&(tcph->check) - (char*)tcph);
        }
        return 1;
}


static int
tcp_dnat_handler(struct sk_buff *skb,
                 struct ip_vs_protocol *pp, struct ip_vs_conn *cp)
{
        struct tcphdr *tcph;
        unsigned int tcphoff;
        int oldlen;

#ifdef CONFIG_IP_VS_IPV6
        if (cp->af == AF_INET6)
                tcphoff = sizeof(struct ipv6hdr);
        else
#endif
                tcphoff = ip_hdrlen(skb);
        oldlen = skb->len - tcphoff;

        /* csum_check requires unshared skb */
        if (!skb_make_writable(skb, tcphoff+sizeof(*tcph)))
                return 0;

        if (unlikely(cp->app != NULL)) {
                /* Some checks before mangling */
                if (pp->csum_check && !pp->csum_check(cp->af, skb, pp))
                        return 0;

                /*
                 *      Attempt ip_vs_app call.
                 *      It will fix ip_vs_conn and iph ack_seq stuff
                 */
                if (!ip_vs_app_pkt_in(cp, skb))
                        return 0;
        }

        tcph = (void *)skb_network_header(skb) + tcphoff;
        tcph->dest = cp->dport;

        /*
         *      Adjust TCP checksums
         */
        if (skb->ip_summed == CHECKSUM_PARTIAL) {
                tcp_partial_csum_update(cp->af, tcph, &cp->daddr, &cp->vaddr,
                                        htonl(oldlen),
                                        htonl(skb->len - tcphoff));
        } else if (!cp->app) {
                /* Only port and addr are changed, do fast csum update */
                tcp_fast_csum_update(cp->af, tcph, &cp->vaddr, &cp->daddr,
                                     cp->vport, cp->dport);
                if (skb->ip_summed == CHECKSUM_COMPLETE)
                        skb->ip_summed = CHECKSUM_NONE;
        } else {
                /* full checksum calculation */
                tcph->check = 0;
                skb->csum = skb_checksum(skb, tcphoff, skb->len - tcphoff, 0);
#ifdef CONFIG_IP_VS_IPV6
                if (cp->af == AF_INET6)
                        tcph->check = csum_ipv6_magic(&cp->caddr.in6,
                                                      &cp->daddr.in6,
                                                      skb->len - tcphoff,
                                                      cp->protocol, skb->csum);
                else
#endif
                        tcph->check = csum_tcpudp_magic(cp->caddr.ip,
                                                        cp->daddr.ip,
                                                        skb->len - tcphoff,
                                                        cp->protocol,
                                                        skb->csum);
                skb->ip_summed = CHECKSUM_UNNECESSARY;
        }
        return 1;
}


static int
tcp_csum_check(int af, struct sk_buff *skb, struct ip_vs_protocol *pp)
{
        unsigned int tcphoff;

#ifdef CONFIG_IP_VS_IPV6
        if (af == AF_INET6)
                tcphoff = sizeof(struct ipv6hdr);
        else
#endif
                tcphoff = ip_hdrlen(skb);

        switch (skb->ip_summed) {
        case CHECKSUM_NONE:
                skb->csum = skb_checksum(skb, tcphoff, skb->len - tcphoff, 0);
        case CHECKSUM_COMPLETE:
#ifdef CONFIG_IP_VS_IPV6
                if (af == AF_INET6) {
                        if (csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
                                            &ipv6_hdr(skb)->daddr,
                                            skb->len - tcphoff,
                                            ipv6_hdr(skb)->nexthdr,
                                            skb->csum)) {
                                IP_VS_DBG_RL_PKT(0, pp, skb, 0,
                                                 "Failed checksum for");
                                return 0;
                        }
                } else
#endif
                        if (csum_tcpudp_magic(ip_hdr(skb)->saddr,
                                              ip_hdr(skb)->daddr,
                                              skb->len - tcphoff,
                                              ip_hdr(skb)->protocol,
                                              skb->csum)) {
                                IP_VS_DBG_RL_PKT(0, pp, skb, 0,
                                                 "Failed checksum for");
                                return 0;
                        }
                break;
        default:
                /* No need to checksum. */
                break;
        }

        return 1;
}


#define TCP_DIR_INPUT           0
#define TCP_DIR_OUTPUT          4
#define TCP_DIR_INPUT_ONLY      8

static const int tcp_state_off[IP_VS_DIR_LAST] = {
        [IP_VS_DIR_INPUT]               =       TCP_DIR_INPUT,
        [IP_VS_DIR_OUTPUT]              =       TCP_DIR_OUTPUT,
        [IP_VS_DIR_INPUT_ONLY]          =       TCP_DIR_INPUT_ONLY,
};

/*
 *      Timeout table[state]
 */
static int tcp_timeouts[IP_VS_TCP_S_LAST+1] = {
        [IP_VS_TCP_S_NONE]              =       2*HZ,
        [IP_VS_TCP_S_ESTABLISHED]       =       15*60*HZ,
        [IP_VS_TCP_S_SYN_SENT]          =       2*60*HZ,
        [IP_VS_TCP_S_SYN_RECV]          =       1*60*HZ,
        [IP_VS_TCP_S_FIN_WAIT]          =       2*60*HZ,
        [IP_VS_TCP_S_TIME_WAIT]         =       2*60*HZ,
        [IP_VS_TCP_S_CLOSE]             =       10*HZ,
        [IP_VS_TCP_S_CLOSE_WAIT]        =       60*HZ,
        [IP_VS_TCP_S_LAST_ACK]          =       30*HZ,
        [IP_VS_TCP_S_LISTEN]            =       2*60*HZ,
        [IP_VS_TCP_S_SYNACK]            =       120*HZ,
        [IP_VS_TCP_S_LAST]              =       2*HZ,
};

static char * tcp_state_name_table[IP_VS_TCP_S_LAST+1] = {
        [IP_VS_TCP_S_NONE]              =       "NONE",
        [IP_VS_TCP_S_ESTABLISHED]       =       "ESTABLISHED",
        [IP_VS_TCP_S_SYN_SENT]          =       "SYN_SENT",
        [IP_VS_TCP_S_SYN_RECV]          =       "SYN_RECV",
        [IP_VS_TCP_S_FIN_WAIT]          =       "FIN_WAIT",
        [IP_VS_TCP_S_TIME_WAIT]         =       "TIME_WAIT",
        [IP_VS_TCP_S_CLOSE]             =       "CLOSE",
        [IP_VS_TCP_S_CLOSE_WAIT]        =       "CLOSE_WAIT",
        [IP_VS_TCP_S_LAST_ACK]          =       "LAST_ACK",
        [IP_VS_TCP_S_LISTEN]            =       "LISTEN",
        [IP_VS_TCP_S_SYNACK]            =       "SYNACK",
        [IP_VS_TCP_S_LAST]              =       "BUG!",
};

#define sNO IP_VS_TCP_S_NONE
#define sES IP_VS_TCP_S_ESTABLISHED
#define sSS IP_VS_TCP_S_SYN_SENT
#define sSR IP_VS_TCP_S_SYN_RECV
#define sFW IP_VS_TCP_S_FIN_WAIT
#define sTW IP_VS_TCP_S_TIME_WAIT
#define sCL IP_VS_TCP_S_CLOSE
#define sCW IP_VS_TCP_S_CLOSE_WAIT
#define sLA IP_VS_TCP_S_LAST_ACK
#define sLI IP_VS_TCP_S_LISTEN
#define sSA IP_VS_TCP_S_SYNACK

struct tcp_states_t {
        int next_state[IP_VS_TCP_S_LAST];
};

static const char * tcp_state_name(int state)
{
        if (state >= IP_VS_TCP_S_LAST)
                return "ERR!";
        return tcp_state_name_table[state] ? tcp_state_name_table[state] : "?";
}

static struct tcp_states_t tcp_states [] = {
/*      INPUT */
/*        sNO, sES, sSS, sSR, sFW, sTW, sCL, sCW, sLA, sLI, sSA */
/*syn*/ {{sSR, sES, sES, sSR, sSR, sSR, sSR, sSR, sSR, sSR, sSR }},
/*fin*/ {{sCL, sCW, sSS, sTW, sTW, sTW, sCL, sCW, sLA, sLI, sTW }},
/*ack*/ {{sCL, sES, sSS, sES, sFW, sTW, sCL, sCW, sCL, sLI, sES }},
/*rst*/ {{sCL, sCL, sCL, sSR, sCL, sCL, sCL, sCL, sLA, sLI, sSR }},

/*      OUTPUT */
/*        sNO, sES, sSS, sSR, sFW, sTW, sCL, sCW, sLA, sLI, sSA */
/*syn*/ {{sSS, sES, sSS, sSR, sSS, sSS, sSS, sSS, sSS, sLI, sSR }},
/*fin*/ {{sTW, sFW, sSS, sTW, sFW, sTW, sCL, sTW, sLA, sLI, sTW }},
/*ack*/ {{sES, sES, sSS, sES, sFW, sTW, sCL, sCW, sLA, sES, sES }},
/*rst*/ {{sCL, sCL, sSS, sCL, sCL, sTW, sCL, sCL, sCL, sCL, sCL }},

/*      INPUT-ONLY */
/*        sNO, sES, sSS, sSR, sFW, sTW, sCL, sCW, sLA, sLI, sSA */
/*syn*/ {{sSR, sES, sES, sSR, sSR, sSR, sSR, sSR, sSR, sSR, sSR }},
/*fin*/ {{sCL, sFW, sSS, sTW, sFW, sTW, sCL, sCW, sLA, sLI, sTW }},
/*ack*/ {{sCL, sES, sSS, sES, sFW, sTW, sCL, sCW, sCL, sLI, sES }},
/*rst*/ {{sCL, sCL, sCL, sSR, sCL, sCL, sCL, sCL, sLA, sLI, sCL }},
};

static struct tcp_states_t tcp_states_dos [] = {
/*      INPUT */
/*        sNO, sES, sSS, sSR, sFW, sTW, sCL, sCW, sLA, sLI, sSA */
/*syn*/ {{sSR, sES, sES, sSR, sSR, sSR, sSR, sSR, sSR, sSR, sSA }},
/*fin*/ {{sCL, sCW, sSS, sTW, sTW, sTW, sCL, sCW, sLA, sLI, sSA }},
/*ack*/ {{sCL, sES, sSS, sSR, sFW, sTW, sCL, sCW, sCL, sLI, sSA }},
/*rst*/ {{sCL, sCL, sCL, sSR, sCL, sCL, sCL, sCL, sLA, sLI, sCL }},

/*      OUTPUT */
/*        sNO, sES, sSS, sSR, sFW, sTW, sCL, sCW, sLA, sLI, sSA */
/*syn*/ {{sSS, sES, sSS, sSA, sSS, sSS, sSS, sSS, sSS, sLI, sSA }},
/*fin*/ {{sTW, sFW, sSS, sTW, sFW, sTW, sCL, sTW, sLA, sLI, sTW }},
/*ack*/ {{sES, sES, sSS, sES, sFW, sTW, sCL, sCW, sLA, sES, sES }},
/*rst*/ {{sCL, sCL, sSS, sCL, sCL, sTW, sCL, sCL, sCL, sCL, sCL }},

/*      INPUT-ONLY */
/*        sNO, sES, sSS, sSR, sFW, sTW, sCL, sCW, sLA, sLI, sSA */
/*syn*/ {{sSA, sES, sES, sSR, sSA, sSA, sSA, sSA, sSA, sSA, sSA }},
/*fin*/ {{sCL, sFW, sSS, sTW, sFW, sTW, sCL, sCW, sLA, sLI, sTW }},
/*ack*/ {{sCL, sES, sSS, sES, sFW, sTW, sCL, sCW, sCL, sLI, sES }},
/*rst*/ {{sCL, sCL, sCL, sSR, sCL, sCL, sCL, sCL, sLA, sLI, sCL }},
};

static struct tcp_states_t *tcp_state_table = tcp_states;


static void tcp_timeout_change(struct ip_vs_protocol *pp, int flags)
{
        int on = (flags & 1);           /* secure_tcp */

        /*
        ** FIXME: change secure_tcp to independent sysctl var
        ** or make it per-service or per-app because it is valid
        ** for most if not for all of the applications. Something
        ** like "capabilities" (flags) for each object.
        */
        tcp_state_table = (on? tcp_states_dos : tcp_states);
}

static int
tcp_set_state_timeout(struct ip_vs_protocol *pp, char *sname, int to)
{
        return ip_vs_set_state_timeout(pp->timeout_table, IP_VS_TCP_S_LAST,
                                       tcp_state_name_table, sname, to);
}

static inline int tcp_state_idx(struct tcphdr *th)
{
        if (th->rst)
                return 3;
        if (th->syn)
                return 0;
        if (th->fin)
                return 1;
        if (th->ack)
                return 2;
        return -1;
}

static inline void
set_tcp_state(struct ip_vs_protocol *pp, struct ip_vs_conn *cp,
              int direction, struct tcphdr *th)
{
        int state_idx;
        int new_state = IP_VS_TCP_S_CLOSE;
        int state_off = tcp_state_off[direction];

        /*
         *    Update state offset to INPUT_ONLY if necessary
         *    or delete NO_OUTPUT flag if output packet detected
         */
        if (cp->flags & IP_VS_CONN_F_NOOUTPUT) {
                if (state_off == TCP_DIR_OUTPUT)
                        cp->flags &= ~IP_VS_CONN_F_NOOUTPUT;
                else
                        state_off = TCP_DIR_INPUT_ONLY;
        }

        if ((state_idx = tcp_state_idx(th)) < 0) {
                IP_VS_DBG(8, "tcp_state_idx=%d!!!\n", state_idx);
                goto tcp_state_out;
        }

        new_state = tcp_state_table[state_off+state_idx].next_state[cp->state];

  tcp_state_out:
        if (new_state != cp->state) {
                struct ip_vs_dest *dest = cp->dest;

                IP_VS_DBG_BUF(8, "%s %s [%c%c%c%c] %s:%d->"
                              "%s:%d state: %s->%s conn->refcnt:%d\n",
                              pp->name,
                              ((state_off == TCP_DIR_OUTPUT) ?
                               "output " : "input "),
                              th->syn ? 'S' : '.',
                              th->fin ? 'F' : '.',
                              th->ack ? 'A' : '.',
                              th->rst ? 'R' : '.',
                              IP_VS_DBG_ADDR(cp->af, &cp->daddr),
                              ntohs(cp->dport),
                              IP_VS_DBG_ADDR(cp->af, &cp->caddr),
                              ntohs(cp->cport),
                              tcp_state_name(cp->state),
                              tcp_state_name(new_state),
                              atomic_read(&cp->refcnt));

                if (dest) {
                        if (!(cp->flags & IP_VS_CONN_F_INACTIVE) &&
                            (new_state != IP_VS_TCP_S_ESTABLISHED)) {
                                atomic_dec(&dest->activeconns);
                                atomic_inc(&dest->inactconns);
                                cp->flags |= IP_VS_CONN_F_INACTIVE;
                        } else if ((cp->flags & IP_VS_CONN_F_INACTIVE) &&
                                   (new_state == IP_VS_TCP_S_ESTABLISHED)) {
                                atomic_inc(&dest->activeconns);
                                atomic_dec(&dest->inactconns);
                                cp->flags &= ~IP_VS_CONN_F_INACTIVE;
                        }
                }
        }

        cp->timeout = pp->timeout_table[cp->state = new_state];
}


/*
 *      Handle state transitions
 */
static int
tcp_state_transition(struct ip_vs_conn *cp, int direction,
                     const struct sk_buff *skb,
                     struct ip_vs_protocol *pp)
{
        struct tcphdr _tcph, *th;

#ifdef CONFIG_IP_VS_IPV6
        int ihl = cp->af == AF_INET ? ip_hdrlen(skb) : sizeof(struct ipv6hdr);
#else
        int ihl = ip_hdrlen(skb);
#endif

        th = skb_header_pointer(skb, ihl, sizeof(_tcph), &_tcph);
        if (th == NULL)
                return 0;

        spin_lock(&cp->lock);
        set_tcp_state(pp, cp, direction, th);
        spin_unlock(&cp->lock);

        return 1;
}


/*
 *      Hash table for TCP application incarnations
 */
#define TCP_APP_TAB_BITS        4
#define TCP_APP_TAB_SIZE        (1 << TCP_APP_TAB_BITS)
#define TCP_APP_TAB_MASK        (TCP_APP_TAB_SIZE - 1)

static struct list_head tcp_apps[TCP_APP_TAB_SIZE];
static DEFINE_SPINLOCK(tcp_app_lock);

static inline __u16 tcp_app_hashkey(__be16 port)
{
        return (((__force u16)port >> TCP_APP_TAB_BITS) ^ (__force u16)port)
                & TCP_APP_TAB_MASK;
}


static int tcp_register_app(struct ip_vs_app *inc)
{
        struct ip_vs_app *i;
        __u16 hash;
        __be16 port = inc->port;
        int ret = 0;

        hash = tcp_app_hashkey(port);

        spin_lock_bh(&tcp_app_lock);
        list_for_each_entry(i, &tcp_apps[hash], p_list) {
                if (i->port == port) {
                        ret = -EEXIST;
                        goto out;
                }
        }
        list_add(&inc->p_list, &tcp_apps[hash]);
        atomic_inc(&ip_vs_protocol_tcp.appcnt);

  out:
        spin_unlock_bh(&tcp_app_lock);
        return ret;
}


static void
tcp_unregister_app(struct ip_vs_app *inc)
{
        spin_lock_bh(&tcp_app_lock);
        atomic_dec(&ip_vs_protocol_tcp.appcnt);
        list_del(&inc->p_list);
        spin_unlock_bh(&tcp_app_lock);
}


static int
tcp_app_conn_bind(struct ip_vs_conn *cp)
{
        int hash;
        struct ip_vs_app *inc;
        int result = 0;

        /* Default binding: bind app only for NAT */
        if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ)
                return 0;

        /* Lookup application incarnations and bind the right one */
        hash = tcp_app_hashkey(cp->vport);

        spin_lock(&tcp_app_lock);
        list_for_each_entry(inc, &tcp_apps[hash], p_list) {
                if (inc->port == cp->vport) {
                        if (unlikely(!ip_vs_app_inc_get(inc)))
                                break;
                        spin_unlock(&tcp_app_lock);

                        IP_VS_DBG_BUF(9, "%s: Binding conn %s:%u->"
                                      "%s:%u to app %s on port %u\n",
                                      __func__,
                                      IP_VS_DBG_ADDR(cp->af, &cp->caddr),
                                      ntohs(cp->cport),
                                      IP_VS_DBG_ADDR(cp->af, &cp->vaddr),
                                      ntohs(cp->vport),
                                      inc->name, ntohs(inc->port));

                        cp->app = inc;
                        if (inc->init_conn)
                                result = inc->init_conn(inc, cp);
                        goto out;
                }
        }
        spin_unlock(&tcp_app_lock);

  out:
        return result;
}


/*
 *      Set LISTEN timeout. (ip_vs_conn_put will setup timer)
 */
void ip_vs_tcp_conn_listen(struct ip_vs_conn *cp)
{
        spin_lock(&cp->lock);
        cp->state = IP_VS_TCP_S_LISTEN;
        cp->timeout = ip_vs_protocol_tcp.timeout_table[IP_VS_TCP_S_LISTEN];
        spin_unlock(&cp->lock);
}


static void ip_vs_tcp_init(struct ip_vs_protocol *pp)
{
        IP_VS_INIT_HASH_TABLE(tcp_apps);
        pp->timeout_table = tcp_timeouts;
}


static void ip_vs_tcp_exit(struct ip_vs_protocol *pp)
{
}


struct ip_vs_protocol ip_vs_protocol_tcp = {
        .name =                 "TCP",
        .protocol =             IPPROTO_TCP,
        .num_states =           IP_VS_TCP_S_LAST,
        .dont_defrag =          0,
        .appcnt =               ATOMIC_INIT(0),
        .init =                 ip_vs_tcp_init,
        .exit =                 ip_vs_tcp_exit,
        .register_app =         tcp_register_app,
        .unregister_app =       tcp_unregister_app,
        .conn_schedule =        tcp_conn_schedule,
        .conn_in_get =          tcp_conn_in_get,
        .conn_out_get =         tcp_conn_out_get,
        .snat_handler =         tcp_snat_handler,
        .dnat_handler =         tcp_dnat_handler,
        .csum_check =           tcp_csum_check,
        .state_name =           tcp_state_name,
        .state_transition =     tcp_state_transition,
        .app_conn_bind =        tcp_app_conn_bind,
        .debug_packet =         ip_vs_tcpudp_debug_packet,
        .timeout_change =       tcp_timeout_change,
        .set_state_timeout =    tcp_set_state_timeout,
};

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