net/netfilter/ipvs/ip_vs_proto_tcp.c

root/net/netfilter/ipvs/ip_vs_proto_tcp.c
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * ip_vs_proto_tcp.c:   TCP load balancing support for IPVS
 *
 * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
 *              Julian Anastasov <ja@ssi.bg>
 *
 * Changes:     Hans Schillstrom <hans.schillstrom@ericsson.com>
 *
 *              Network name space (netns) aware.
 *              Global data moved to netns i.e struct netns_ipvs
 *              tcp_timeouts table has copy per netns in a hash table per
 *              protocol ip_vs_proto_data and is handled by netns
 */

#define pr_fmt(fmt) "IPVS: " fmt

#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 <linux/indirect_call_wrapper.h>

#include <net/ip_vs.h>

static int
tcp_csum_check(int af, struct sk_buff *skb, struct ip_vs_protocol *pp,
               struct ip_vs_iphdr *iph);

static int
tcp_conn_schedule(struct netns_ipvs *ipvs, int af, struct sk_buff *skb,
                  struct ip_vs_proto_data *pd,
                  int *verdict, struct ip_vs_conn **cpp,
                  struct ip_vs_iphdr *iph)
{
        struct ip_vs_service *svc;
        struct tcphdr _tcph, *th;
        __be16 _ports[2], *ports = NULL;

        /* In the event of icmp, we're only guaranteed to have the first 8
         * bytes of the transport header, so we only check the rest of the
         * TCP packet for non-ICMP packets
         */
        if (likely(!ip_vs_iph_icmp(iph))) {
                th = skb_header_pointer(skb, iph->len, sizeof(_tcph), &_tcph);
                if (th) {
                        if (th->rst || !(sysctl_sloppy_tcp(ipvs) || th->syn))
                                return 1;
                        ports = &th->source;
                }
        } else {
                ports = skb_header_pointer(
                        skb, iph->len, sizeof(_ports), &_ports);
        }

        if (!ports) {
                *verdict = NF_DROP;
                return 0;
        }

        /* No !th->ack check to allow scheduling on SYN+ACK for Active FTP */

        if (likely(!ip_vs_iph_inverse(iph)))
                svc = ip_vs_service_find(ipvs, af, skb->mark, iph->protocol,
                                         &iph->daddr, ports[1]);
        else
                svc = ip_vs_service_find(ipvs, af, skb->mark, iph->protocol,
                                         &iph->saddr, ports[0]);

        if (svc) {
                int ignored;

                if (ip_vs_todrop(ipvs)) {
                        /*
                         * It seems that we are very loaded.
                         * We have to drop this packet :(
                         */
                        *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, pd, &ignored, iph);
                if (!*cpp && ignored <= 0) {
                        if (!ignored)
                                *verdict = ip_vs_leave(svc, skb, pd, iph);
                        else
                                *verdict = NF_DROP;
                        return 0;
                }
        }
        /* NF_ACCEPT */
        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))));
}


INDIRECT_CALLABLE_SCOPE int
tcp_snat_handler(struct sk_buff *skb, struct ip_vs_protocol *pp,
                 struct ip_vs_conn *cp, struct ip_vs_iphdr *iph)
{
        struct tcphdr *tcph;
        unsigned int tcphoff = iph->len;
        bool payload_csum = false;
        int oldlen;

#ifdef CONFIG_IP_VS_IPV6
        if (cp->af == AF_INET6 && iph->fragoffs)
                return 1;
#endif
        oldlen = skb->len - tcphoff;

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

        if (unlikely(cp->app != NULL)) {
                int ret;

                /* Some checks before mangling */
                if (!tcp_csum_check(cp->af, skb, pp, iph))
                        return 0;

                /* Call application helper if needed */
                if (!(ret = ip_vs_app_pkt_out(cp, skb, iph)))
                        return 0;
                /* ret=2: csum update is needed after payload mangling */
                if (ret == 1)
                        oldlen = skb->len - tcphoff;
                else
                        payload_csum = true;
        }

        tcph = (void *)skb->data + 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,
                                        htons(oldlen),
                                        htons(skb->len - tcphoff));
        } else if (!payload_csum) {
                /* 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 = cp->app ?
                                         CHECKSUM_UNNECESSARY : 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);
                skb->ip_summed = CHECKSUM_UNNECESSARY;

                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 ip_vs_iphdr *iph)
{
        struct tcphdr *tcph;
        unsigned int tcphoff = iph->len;
        bool payload_csum = false;
        int oldlen;

#ifdef CONFIG_IP_VS_IPV6
        if (cp->af == AF_INET6 && iph->fragoffs)
                return 1;
#endif
        oldlen = skb->len - tcphoff;

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

        if (unlikely(cp->app != NULL)) {
                int ret;

                /* Some checks before mangling */
                if (!tcp_csum_check(cp->af, skb, pp, iph))
                        return 0;

                /*
                 *      Attempt ip_vs_app call.
                 *      It will fix ip_vs_conn and iph ack_seq stuff
                 */
                if (!(ret = ip_vs_app_pkt_in(cp, skb, iph)))
                        return 0;
                /* ret=2: csum update is needed after payload mangling */
                if (ret == 1)
                        oldlen = skb->len - tcphoff;
                else
                        payload_csum = true;
        }

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

        /*
         *      Adjust TCP checksums
         */
        if (skb->ip_summed == CHECKSUM_PARTIAL) {
                tcp_partial_csum_update(cp->af, tcph, &cp->vaddr, &cp->daddr,
                                        htons(oldlen),
                                        htons(skb->len - tcphoff));
        } else if (!payload_csum) {
                /* 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 = cp->app ?
                                         CHECKSUM_UNNECESSARY : 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,
               struct ip_vs_iphdr *iph)
{
        if (!ip_vs_checksum_common_check(skb, iph->len, IPPROTO_TCP, af)) {
                IP_VS_DBG_RL_PKT(0, af, pp, skb, iph->off,
                                 "Failed checksum for");
                return 0;
        }
        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 const 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 const char *const 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!",
};

static const bool tcp_state_active_table[IP_VS_TCP_S_LAST] = {
        [IP_VS_TCP_S_NONE]              =       false,
        [IP_VS_TCP_S_ESTABLISHED]       =       true,
        [IP_VS_TCP_S_SYN_SENT]          =       true,
        [IP_VS_TCP_S_SYN_RECV]          =       true,
        [IP_VS_TCP_S_FIN_WAIT]          =       false,
        [IP_VS_TCP_S_TIME_WAIT]         =       false,
        [IP_VS_TCP_S_CLOSE]             =       false,
        [IP_VS_TCP_S_CLOSE_WAIT]        =       false,
        [IP_VS_TCP_S_LAST_ACK]          =       false,
        [IP_VS_TCP_S_LISTEN]            =       false,
        [IP_VS_TCP_S_SYNACK]            =       true,
};

#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 bool tcp_state_active(int state)
{
        if (state >= IP_VS_TCP_S_LAST)
                return false;
        return tcp_state_active_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*/ {{sES, 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*/ {{sES, 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*/ {{sES, 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*/ {{sES, sES, sSS, sES, sFW, sTW, sCL, sCW, sCL, sLI, sES }},
/*rst*/ {{sCL, sCL, sCL, sSR, sCL, sCL, sCL, sCL, sLA, sLI, sCL }},
};

static void tcp_timeout_change(struct ip_vs_proto_data *pd, 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.
        */
        pd->tcp_state_table = (on ? tcp_states_dos : tcp_states);
}

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_proto_data *pd, 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 =
                pd->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] c:%s:%d v:%s:%d "
                              "d:%s:%d state: %s->%s conn->refcnt:%d\n",
                              pd->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->caddr),
                              ntohs(cp->cport),
                              IP_VS_DBG_ADDR(cp->af, &cp->vaddr),
                              ntohs(cp->vport),
                              IP_VS_DBG_ADDR(cp->daf, &cp->daddr),
                              ntohs(cp->dport),
                              tcp_state_name(cp->state),
                              tcp_state_name(new_state),
                              refcount_read(&cp->refcnt));

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

        if (likely(pd))
                cp->timeout = pd->timeout_table[cp->state = new_state];
        else    /* What to do ? */
                cp->timeout = tcp_timeouts[cp->state = new_state];
}

/*
 *      Handle state transitions
 */
static void
tcp_state_transition(struct ip_vs_conn *cp, int direction,
                     const struct sk_buff *skb,
                     struct ip_vs_proto_data *pd,
                     unsigned int iph_len)
{
        struct tcphdr _tcph, *th;

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

        spin_lock_bh(&cp->lock);
        set_tcp_state(pd, cp, direction, th);
        spin_unlock_bh(&cp->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 netns_ipvs *ipvs, struct ip_vs_app *inc)
{
        struct ip_vs_app *i;
        __u16 hash;
        __be16 port = inc->port;
        int ret = 0;
        struct ip_vs_proto_data *pd = ip_vs_proto_data_get(ipvs, IPPROTO_TCP);

        hash = tcp_app_hashkey(port);

        list_for_each_entry(i, &ipvs->tcp_apps[hash], p_list) {
                if (i->port == port) {
                        ret = -EEXIST;
                        goto out;
                }
        }
        list_add_rcu(&inc->p_list, &ipvs->tcp_apps[hash]);
        atomic_inc(&pd->appcnt);

  out:
        return ret;
}


static void
tcp_unregister_app(struct netns_ipvs *ipvs, struct ip_vs_app *inc)
{
        struct ip_vs_proto_data *pd = ip_vs_proto_data_get(ipvs, IPPROTO_TCP);

        atomic_dec(&pd->appcnt);
        list_del_rcu(&inc->p_list);
}


static int
tcp_app_conn_bind(struct ip_vs_conn *cp)
{
        struct netns_ipvs *ipvs = cp->ipvs;
        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);

        list_for_each_entry_rcu(inc, &ipvs->tcp_apps[hash], p_list) {
                if (inc->port == cp->vport) {
                        if (unlikely(!ip_vs_app_inc_get(inc)))
                                break;

                        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);
                        break;
                }
        }

        return result;
}


/*
 *      Set LISTEN timeout. (ip_vs_conn_put will setup timer)
 */
void ip_vs_tcp_conn_listen(struct ip_vs_conn *cp)
{
        struct ip_vs_proto_data *pd = ip_vs_proto_data_get(cp->ipvs, IPPROTO_TCP);

        spin_lock_bh(&cp->lock);
        cp->state = IP_VS_TCP_S_LISTEN;
        cp->timeout = (pd ? pd->timeout_table[IP_VS_TCP_S_LISTEN]
                           : tcp_timeouts[IP_VS_TCP_S_LISTEN]);
        spin_unlock_bh(&cp->lock);
}

/* ---------------------------------------------
 *   timeouts is netns related now.
 * ---------------------------------------------
 */
static int __ip_vs_tcp_init(struct netns_ipvs *ipvs, struct ip_vs_proto_data *pd)
{
        ip_vs_init_hash_table(ipvs->tcp_apps, TCP_APP_TAB_SIZE);
        pd->timeout_table = ip_vs_create_timeout_table((int *)tcp_timeouts,
                                                        sizeof(tcp_timeouts));
        if (!pd->timeout_table)
                return -ENOMEM;
        pd->tcp_state_table = tcp_states;
        return 0;
}

static void __ip_vs_tcp_exit(struct netns_ipvs *ipvs, struct ip_vs_proto_data *pd)
{
        kfree(pd->timeout_table);
}


struct ip_vs_protocol ip_vs_protocol_tcp = {
        .name =                 "TCP",
        .protocol =             IPPROTO_TCP,
        .num_states =           IP_VS_TCP_S_LAST,
        .dont_defrag =          0,
        .init =                 NULL,
        .exit =                 NULL,
        .init_netns =           __ip_vs_tcp_init,
        .exit_netns =           __ip_vs_tcp_exit,
        .register_app =         tcp_register_app,
        .unregister_app =       tcp_unregister_app,
        .conn_schedule =        tcp_conn_schedule,
        .conn_in_get =          ip_vs_conn_in_get_proto,
        .conn_out_get =         ip_vs_conn_out_get_proto,
        .snat_handler =         tcp_snat_handler,
        .dnat_handler =         tcp_dnat_handler,
        .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,
};
Linux
