/*
 *      DCCP over IPv6
 *      Linux INET6 implementation
 *
 *      Based on net/dccp6/ipv6.c
 *
 *      Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
 *
 *      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.
 */

#include <linux/module.h>
#include <linux/random.h>
#include <linux/slab.h>
#include <linux/xfrm.h>

#include <net/addrconf.h>
#include <net/inet_common.h>
#include <net/inet_hashtables.h>
#include <net/inet_sock.h>
#include <net/inet6_connection_sock.h>
#include <net/inet6_hashtables.h>
#include <net/ip6_route.h>
#include <net/ipv6.h>
#include <net/protocol.h>
#include <net/transp_v6.h>
#include <net/ip6_checksum.h>
#include <net/xfrm.h>

#include "dccp.h"
#include "ipv6.h"
#include "feat.h"

/* The per-net dccp.v6_ctl_sk is used for sending RSTs and ACKs */

static const struct inet_connection_sock_af_ops dccp_ipv6_mapped;
static const struct inet_connection_sock_af_ops dccp_ipv6_af_ops;

static void dccp_v6_hash(struct sock *sk)
{
        if (sk->sk_state != DCCP_CLOSED) {
                if (inet_csk(sk)->icsk_af_ops == &dccp_ipv6_mapped) {
                        inet_hash(sk);
                        return;
                }
                local_bh_disable();
                __inet6_hash(sk, NULL);
                local_bh_enable();
        }
}

/* add pseudo-header to DCCP checksum stored in skb->csum */
static inline __sum16 dccp_v6_csum_finish(struct sk_buff *skb,
                                      struct in6_addr *saddr,
                                      struct in6_addr *daddr)
{
        return csum_ipv6_magic(saddr, daddr, skb->len, IPPROTO_DCCP, skb->csum);
}

static inline void dccp_v6_send_check(struct sock *sk, struct sk_buff *skb)
{
        struct ipv6_pinfo *np = inet6_sk(sk);
        struct dccp_hdr *dh = dccp_hdr(skb);

        dccp_csum_outgoing(skb);
        dh->dccph_checksum = dccp_v6_csum_finish(skb, &np->saddr, &np->daddr);
}

static inline __u32 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr,
                                                  __be16 sport, __be16 dport   )
{
        return secure_tcpv6_sequence_number(saddr, daddr, sport, dport);
}

static inline __u32 dccp_v6_init_sequence(struct sk_buff *skb)
{
        return secure_dccpv6_sequence_number(ipv6_hdr(skb)->daddr.s6_addr32,
                                             ipv6_hdr(skb)->saddr.s6_addr32,
                                             dccp_hdr(skb)->dccph_dport,
                                             dccp_hdr(skb)->dccph_sport     );

}

static void dccp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
                        u8 type, u8 code, int offset, __be32 info)
{
        struct ipv6hdr *hdr = (struct ipv6hdr *)skb->data;
        const struct dccp_hdr *dh = (struct dccp_hdr *)(skb->data + offset);
        struct dccp_sock *dp;
        struct ipv6_pinfo *np;
        struct sock *sk;
        int err;
        __u64 seq;
        struct net *net = dev_net(skb->dev);

        if (skb->len < offset + sizeof(*dh) ||
            skb->len < offset + __dccp_basic_hdr_len(dh)) {
                ICMP6_INC_STATS_BH(net, __in6_dev_get(skb->dev),
                                   ICMP6_MIB_INERRORS);
                return;
        }

        sk = inet6_lookup(net, &dccp_hashinfo,
                        &hdr->daddr, dh->dccph_dport,
                        &hdr->saddr, dh->dccph_sport, inet6_iif(skb));

        if (sk == NULL) {
                ICMP6_INC_STATS_BH(net, __in6_dev_get(skb->dev),
                                   ICMP6_MIB_INERRORS);
                return;
        }

        if (sk->sk_state == DCCP_TIME_WAIT) {
                inet_twsk_put(inet_twsk(sk));
                return;
        }

        bh_lock_sock(sk);
        if (sock_owned_by_user(sk))
                NET_INC_STATS_BH(net, LINUX_MIB_LOCKDROPPEDICMPS);

        if (sk->sk_state == DCCP_CLOSED)
                goto out;

        dp = dccp_sk(sk);
        seq = dccp_hdr_seq(dh);
        if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_LISTEN) &&
            !between48(seq, dp->dccps_awl, dp->dccps_awh)) {
                NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
                goto out;
        }

        np = inet6_sk(sk);

        if (type == ICMPV6_PKT_TOOBIG) {
                struct dst_entry *dst = NULL;

                if (sock_owned_by_user(sk))
                        goto out;
                if ((1 << sk->sk_state) & (DCCPF_LISTEN | DCCPF_CLOSED))
                        goto out;

                /* icmp should have updated the destination cache entry */
                dst = __sk_dst_check(sk, np->dst_cookie);
                if (dst == NULL) {
                        struct inet_sock *inet = inet_sk(sk);
                        struct flowi fl;

                        /* BUGGG_FUTURE: Again, it is not clear how
                           to handle rthdr case. Ignore this complexity
                           for now.
                         */
                        memset(&fl, 0, sizeof(fl));
                        fl.proto = IPPROTO_DCCP;
                        ipv6_addr_copy(&fl.fl6_dst, &np->daddr);
                        ipv6_addr_copy(&fl.fl6_src, &np->saddr);
                        fl.oif = sk->sk_bound_dev_if;
                        fl.fl_ip_dport = inet->inet_dport;
                        fl.fl_ip_sport = inet->inet_sport;
                        security_sk_classify_flow(sk, &fl);

                        err = ip6_dst_lookup(sk, &dst, &fl);
                        if (err) {
                                sk->sk_err_soft = -err;
                                goto out;
                        }

                        err = xfrm_lookup(net, &dst, &fl, sk, 0);
                        if (err < 0) {
                                sk->sk_err_soft = -err;
                                goto out;
                        }
                } else
                        dst_hold(dst);

                if (inet_csk(sk)->icsk_pmtu_cookie > dst_mtu(dst)) {
                        dccp_sync_mss(sk, dst_mtu(dst));
                } /* else let the usual retransmit timer handle it */
                dst_release(dst);
                goto out;
        }

        icmpv6_err_convert(type, code, &err);

        /* Might be for an request_sock */
        switch (sk->sk_state) {
                struct request_sock *req, **prev;
        case DCCP_LISTEN:
                if (sock_owned_by_user(sk))
                        goto out;

                req = inet6_csk_search_req(sk, &prev, dh->dccph_dport,
                                           &hdr->daddr, &hdr->saddr,
                                           inet6_iif(skb));
                if (req == NULL)
                        goto out;

                /*
                 * ICMPs are not backlogged, hence we cannot get an established
                 * socket here.
                 */
                WARN_ON(req->sk != NULL);

                if (seq != dccp_rsk(req)->dreq_iss) {
                        NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
                        goto out;
                }

                inet_csk_reqsk_queue_drop(sk, req, prev);
                goto out;

        case DCCP_REQUESTING:
        case DCCP_RESPOND:  /* Cannot happen.
                               It can, it SYNs are crossed. --ANK */
                if (!sock_owned_by_user(sk)) {
                        DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
                        sk->sk_err = err;
                        /*
                         * Wake people up to see the error
                         * (see connect in sock.c)
                         */
                        sk->sk_error_report(sk);
                        dccp_done(sk);
                } else
                        sk->sk_err_soft = err;
                goto out;
        }

        if (!sock_owned_by_user(sk) && np->recverr) {
                sk->sk_err = err;
                sk->sk_error_report(sk);
        } else
                sk->sk_err_soft = err;

out:
        bh_unlock_sock(sk);
        sock_put(sk);
}


static int dccp_v6_send_response(struct sock *sk, struct request_sock *req,
                                 struct request_values *rv_unused)
{
        struct inet6_request_sock *ireq6 = inet6_rsk(req);
        struct ipv6_pinfo *np = inet6_sk(sk);
        struct sk_buff *skb;
        struct ipv6_txoptions *opt = NULL;
        struct in6_addr *final_p = NULL, final;
        struct flowi fl;
        int err = -1;
        struct dst_entry *dst;

        memset(&fl, 0, sizeof(fl));
        fl.proto = IPPROTO_DCCP;
        ipv6_addr_copy(&fl.fl6_dst, &ireq6->rmt_addr);
        ipv6_addr_copy(&fl.fl6_src, &ireq6->loc_addr);
        fl.fl6_flowlabel = 0;
        fl.oif = ireq6->iif;
        fl.fl_ip_dport = inet_rsk(req)->rmt_port;
        fl.fl_ip_sport = inet_rsk(req)->loc_port;
        security_req_classify_flow(req, &fl);

        opt = np->opt;

        if (opt != NULL && opt->srcrt != NULL) {
                const struct rt0_hdr *rt0 = (struct rt0_hdr *)opt->srcrt;

                ipv6_addr_copy(&final, &fl.fl6_dst);
                ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
                final_p = &final;
        }

        err = ip6_dst_lookup(sk, &dst, &fl);
        if (err)
                goto done;

        if (final_p)
                ipv6_addr_copy(&fl.fl6_dst, final_p);

        err = xfrm_lookup(sock_net(sk), &dst, &fl, sk, 0);
        if (err < 0)
                goto done;

        skb = dccp_make_response(sk, dst, req);
        if (skb != NULL) {
                struct dccp_hdr *dh = dccp_hdr(skb);

                dh->dccph_checksum = dccp_v6_csum_finish(skb,
                                                         &ireq6->loc_addr,
                                                         &ireq6->rmt_addr);
                ipv6_addr_copy(&fl.fl6_dst, &ireq6->rmt_addr);
                err = ip6_xmit(sk, skb, &fl, opt);
                err = net_xmit_eval(err);
        }

done:
        if (opt != NULL && opt != np->opt)
                sock_kfree_s(sk, opt, opt->tot_len);
        dst_release(dst);
        return err;
}

static void dccp_v6_reqsk_destructor(struct request_sock *req)
{
        dccp_feat_list_purge(&dccp_rsk(req)->dreq_featneg);
        if (inet6_rsk(req)->pktopts != NULL)
                kfree_skb(inet6_rsk(req)->pktopts);
}

static void dccp_v6_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb)
{
        struct ipv6hdr *rxip6h;
        struct sk_buff *skb;
        struct flowi fl;
        struct net *net = dev_net(skb_dst(rxskb)->dev);
        struct sock *ctl_sk = net->dccp.v6_ctl_sk;
        struct dst_entry *dst;

        if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
                return;

        if (!ipv6_unicast_destination(rxskb))
                return;

        skb = dccp_ctl_make_reset(ctl_sk, rxskb);
        if (skb == NULL)
                return;

        rxip6h = ipv6_hdr(rxskb);
        dccp_hdr(skb)->dccph_checksum = dccp_v6_csum_finish(skb, &rxip6h->saddr,
                                                            &rxip6h->daddr);

        memset(&fl, 0, sizeof(fl));
        ipv6_addr_copy(&fl.fl6_dst, &rxip6h->saddr);
        ipv6_addr_copy(&fl.fl6_src, &rxip6h->daddr);

        fl.proto = IPPROTO_DCCP;
        fl.oif = inet6_iif(rxskb);
        fl.fl_ip_dport = dccp_hdr(skb)->dccph_dport;
        fl.fl_ip_sport = dccp_hdr(skb)->dccph_sport;
        security_skb_classify_flow(rxskb, &fl);

        /* sk = NULL, but it is safe for now. RST socket required. */
        if (!ip6_dst_lookup(ctl_sk, &dst, &fl)) {
                if (xfrm_lookup(net, &dst, &fl, NULL, 0) >= 0) {
                        skb_dst_set(skb, dst);
                        ip6_xmit(ctl_sk, skb, &fl, NULL);
                        DCCP_INC_STATS_BH(DCCP_MIB_OUTSEGS);
                        DCCP_INC_STATS_BH(DCCP_MIB_OUTRSTS);
                        return;
                }
        }

        kfree_skb(skb);
}

static struct request_sock_ops dccp6_request_sock_ops = {
        .family         = AF_INET6,
        .obj_size       = sizeof(struct dccp6_request_sock),
        .rtx_syn_ack    = dccp_v6_send_response,
        .send_ack       = dccp_reqsk_send_ack,
        .destructor     = dccp_v6_reqsk_destructor,
        .send_reset     = dccp_v6_ctl_send_reset,
};

static struct sock *dccp_v6_hnd_req(struct sock *sk,struct sk_buff *skb)
{
        const struct dccp_hdr *dh = dccp_hdr(skb);
        const struct ipv6hdr *iph = ipv6_hdr(skb);
        struct sock *nsk;
        struct request_sock **prev;
        /* Find possible connection requests. */
        struct request_sock *req = inet6_csk_search_req(sk, &prev,
                                                        dh->dccph_sport,
                                                        &iph->saddr,
                                                        &iph->daddr,
                                                        inet6_iif(skb));
        if (req != NULL)
                return dccp_check_req(sk, skb, req, prev);

        nsk = __inet6_lookup_established(sock_net(sk), &dccp_hashinfo,
                                         &iph->saddr, dh->dccph_sport,
                                         &iph->daddr, ntohs(dh->dccph_dport),
                                         inet6_iif(skb));
        if (nsk != NULL) {
                if (nsk->sk_state != DCCP_TIME_WAIT) {
                        bh_lock_sock(nsk);
                        return nsk;
                }
                inet_twsk_put(inet_twsk(nsk));
                return NULL;
        }

        return sk;
}

static int dccp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
{
        struct request_sock *req;
        struct dccp_request_sock *dreq;
        struct inet6_request_sock *ireq6;
        struct ipv6_pinfo *np = inet6_sk(sk);
        const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
        struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);

        if (skb->protocol == htons(ETH_P_IP))
                return dccp_v4_conn_request(sk, skb);

        if (!ipv6_unicast_destination(skb))
                return 0;       /* discard, don't send a reset here */

        if (dccp_bad_service_code(sk, service)) {
                dcb->dccpd_reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
                goto drop;
        }
        /*
         * There are no SYN attacks on IPv6, yet...
         */
        dcb->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
        if (inet_csk_reqsk_queue_is_full(sk))
                goto drop;

        if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
                goto drop;

        req = inet6_reqsk_alloc(&dccp6_request_sock_ops);
        if (req == NULL)
                goto drop;

        if (dccp_reqsk_init(req, dccp_sk(sk), skb))
                goto drop_and_free;

        dreq = dccp_rsk(req);
        if (dccp_parse_options(sk, dreq, skb))
                goto drop_and_free;

        if (security_inet_conn_request(sk, skb, req))
                goto drop_and_free;

        ireq6 = inet6_rsk(req);
        ipv6_addr_copy(&ireq6->rmt_addr, &ipv6_hdr(skb)->saddr);
        ipv6_addr_copy(&ireq6->loc_addr, &ipv6_hdr(skb)->daddr);

        if (ipv6_opt_accepted(sk, skb) ||
            np->rxopt.bits.rxinfo || np->rxopt.bits.rxoinfo ||
            np->rxopt.bits.rxhlim || np->rxopt.bits.rxohlim) {
                atomic_inc(&skb->users);
                ireq6->pktopts = skb;
        }
        ireq6->iif = sk->sk_bound_dev_if;

        /* So that link locals have meaning */
        if (!sk->sk_bound_dev_if &&
            ipv6_addr_type(&ireq6->rmt_addr) & IPV6_ADDR_LINKLOCAL)
                ireq6->iif = inet6_iif(skb);

        /*
         * Step 3: Process LISTEN state
         *
         *   Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
         *
         *   In fact we defer setting S.GSR, S.SWL, S.SWH to
         *   dccp_create_openreq_child.
         */
        dreq->dreq_isr     = dcb->dccpd_seq;
        dreq->dreq_iss     = dccp_v6_init_sequence(skb);
        dreq->dreq_service = service;

        if (dccp_v6_send_response(sk, req, NULL))
                goto drop_and_free;

        inet6_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
        return 0;

drop_and_free:
        reqsk_free(req);
drop:
        DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
        return -1;
}

static struct sock *dccp_v6_request_recv_sock(struct sock *sk,
                                              struct sk_buff *skb,
                                              struct request_sock *req,
                                              struct dst_entry *dst)
{
        struct inet6_request_sock *ireq6 = inet6_rsk(req);
        struct ipv6_pinfo *newnp, *np = inet6_sk(sk);
        struct inet_sock *newinet;
        struct dccp_sock *newdp;
        struct dccp6_sock *newdp6;
        struct sock *newsk;
        struct ipv6_txoptions *opt;

        if (skb->protocol == htons(ETH_P_IP)) {
                /*
                 *      v6 mapped
                 */
                newsk = dccp_v4_request_recv_sock(sk, skb, req, dst);
                if (newsk == NULL)
                        return NULL;

                newdp6 = (struct dccp6_sock *)newsk;
                newdp = dccp_sk(newsk);
                newinet = inet_sk(newsk);
                newinet->pinet6 = &newdp6->inet6;
                newnp = inet6_sk(newsk);

                memcpy(newnp, np, sizeof(struct ipv6_pinfo));

                ipv6_addr_set_v4mapped(newinet->inet_daddr, &newnp->daddr);

                ipv6_addr_set_v4mapped(newinet->inet_saddr, &newnp->saddr);

                ipv6_addr_copy(&newnp->rcv_saddr, &newnp->saddr);

                inet_csk(newsk)->icsk_af_ops = &dccp_ipv6_mapped;
                newsk->sk_backlog_rcv = dccp_v4_do_rcv;
                newnp->pktoptions  = NULL;
                newnp->opt         = NULL;
                newnp->mcast_oif   = inet6_iif(skb);
                newnp->mcast_hops  = ipv6_hdr(skb)->hop_limit;

                /*
                 * No need to charge this sock to the relevant IPv6 refcnt debug socks count
                 * here, dccp_create_openreq_child now does this for us, see the comment in
                 * that function for the gory details. -acme
                 */

                /* It is tricky place. Until this moment IPv4 tcp
                   worked with IPv6 icsk.icsk_af_ops.
                   Sync it now.
                 */
                dccp_sync_mss(newsk, inet_csk(newsk)->icsk_pmtu_cookie);

                return newsk;
        }

        opt = np->opt;

        if (sk_acceptq_is_full(sk))
                goto out_overflow;

        if (dst == NULL) {
                struct in6_addr *final_p = NULL, final;
                struct flowi fl;

                memset(&fl, 0, sizeof(fl));
                fl.proto = IPPROTO_DCCP;
                ipv6_addr_copy(&fl.fl6_dst, &ireq6->rmt_addr);
                if (opt != NULL && opt->srcrt != NULL) {
                        const struct rt0_hdr *rt0 = (struct rt0_hdr *)opt->srcrt;

                        ipv6_addr_copy(&final, &fl.fl6_dst);
                        ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
                        final_p = &final;
                }
                ipv6_addr_copy(&fl.fl6_src, &ireq6->loc_addr);
                fl.oif = sk->sk_bound_dev_if;
                fl.fl_ip_dport = inet_rsk(req)->rmt_port;
                fl.fl_ip_sport = inet_rsk(req)->loc_port;
                security_sk_classify_flow(sk, &fl);

                if (ip6_dst_lookup(sk, &dst, &fl))
                        goto out;

                if (final_p)
                        ipv6_addr_copy(&fl.fl6_dst, final_p);

                if ((xfrm_lookup(sock_net(sk), &dst, &fl, sk, 0)) < 0)
                        goto out;
        }

        newsk = dccp_create_openreq_child(sk, req, skb);
        if (newsk == NULL)
                goto out;

        /*
         * No need to charge this sock to the relevant IPv6 refcnt debug socks
         * count here, dccp_create_openreq_child now does this for us, see the
         * comment in that function for the gory details. -acme
         */

        __ip6_dst_store(newsk, dst, NULL, NULL);
        newsk->sk_route_caps = dst->dev->features & ~(NETIF_F_IP_CSUM |
                                                      NETIF_F_TSO);
        newdp6 = (struct dccp6_sock *)newsk;
        newinet = inet_sk(newsk);
        newinet->pinet6 = &newdp6->inet6;
        newdp = dccp_sk(newsk);
        newnp = inet6_sk(newsk);

        memcpy(newnp, np, sizeof(struct ipv6_pinfo));

        ipv6_addr_copy(&newnp->daddr, &ireq6->rmt_addr);
        ipv6_addr_copy(&newnp->saddr, &ireq6->loc_addr);
        ipv6_addr_copy(&newnp->rcv_saddr, &ireq6->loc_addr);
        newsk->sk_bound_dev_if = ireq6->iif;

        /* Now IPv6 options...

           First: no IPv4 options.
         */
        newinet->opt = NULL;

        /* Clone RX bits */
        newnp->rxopt.all = np->rxopt.all;

        /* Clone pktoptions received with SYN */
        newnp->pktoptions = NULL;
        if (ireq6->pktopts != NULL) {
                newnp->pktoptions = skb_clone(ireq6->pktopts, GFP_ATOMIC);
                kfree_skb(ireq6->pktopts);
                ireq6->pktopts = NULL;
                if (newnp->pktoptions)
                        skb_set_owner_r(newnp->pktoptions, newsk);
        }
        newnp->opt        = NULL;
        newnp->mcast_oif  = inet6_iif(skb);
        newnp->mcast_hops = ipv6_hdr(skb)->hop_limit;

        /*
         * Clone native IPv6 options from listening socket (if any)
         *
         * Yes, keeping reference count would be much more clever, but we make
         * one more one thing there: reattach optmem to newsk.
         */
        if (opt != NULL) {
                newnp->opt = ipv6_dup_options(newsk, opt);
                if (opt != np->opt)
                        sock_kfree_s(sk, opt, opt->tot_len);
        }

        inet_csk(newsk)->icsk_ext_hdr_len = 0;
        if (newnp->opt != NULL)
                inet_csk(newsk)->icsk_ext_hdr_len = (newnp->opt->opt_nflen +
                                                     newnp->opt->opt_flen);

        dccp_sync_mss(newsk, dst_mtu(dst));

        newinet->inet_daddr = newinet->inet_saddr = LOOPBACK4_IPV6;
        newinet->inet_rcv_saddr = LOOPBACK4_IPV6;

        __inet6_hash(newsk, NULL);
        __inet_inherit_port(sk, newsk);

        return newsk;

out_overflow:
        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
out:
        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS);
        if (opt != NULL && opt != np->opt)
                sock_kfree_s(sk, opt, opt->tot_len);
        dst_release(dst);
        return NULL;
}

/* The socket must have it's spinlock held when we get
 * here.
 *
 * We have a potential double-lock case here, so even when
 * doing backlog processing we use the BH locking scheme.
 * This is because we cannot sleep with the original spinlock
 * held.
 */
static int dccp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
{
        struct ipv6_pinfo *np = inet6_sk(sk);
        struct sk_buff *opt_skb = NULL;

        /* Imagine: socket is IPv6. IPv4 packet arrives,
           goes to IPv4 receive handler and backlogged.
           From backlog it always goes here. Kerboom...
           Fortunately, dccp_rcv_established and rcv_established
           handle them correctly, but it is not case with
           dccp_v6_hnd_req and dccp_v6_ctl_send_reset().   --ANK
         */

        if (skb->protocol == htons(ETH_P_IP))
                return dccp_v4_do_rcv(sk, skb);

        if (sk_filter(sk, skb))
                goto discard;

        /*
         * socket locking is here for SMP purposes as backlog rcv is currently
         * called with bh processing disabled.
         */

        /* Do Stevens' IPV6_PKTOPTIONS.

           Yes, guys, it is the only place in our code, where we
           may make it not affecting IPv4.
           The rest of code is protocol independent,
           and I do not like idea to uglify IPv4.

           Actually, all the idea behind IPV6_PKTOPTIONS
           looks not very well thought. For now we latch
           options, received in the last packet, enqueued
           by tcp. Feel free to propose better solution.
                                               --ANK (980728)
         */
        if (np->rxopt.all)
        /*
         * FIXME: Add handling of IPV6_PKTOPTIONS skb. See the comments below
         *        (wrt ipv6_pktopions) and net/ipv6/tcp_ipv6.c for an example.
         */
                opt_skb = skb_clone(skb, GFP_ATOMIC);

        if (sk->sk_state == DCCP_OPEN) { /* Fast path */
                if (dccp_rcv_established(sk, skb, dccp_hdr(skb), skb->len))
                        goto reset;
                if (opt_skb) {
                        /* XXX This is where we would goto ipv6_pktoptions. */
                        __kfree_skb(opt_skb);
                }
                return 0;
        }

        /*
         *  Step 3: Process LISTEN state
         *     If S.state == LISTEN,
         *       If P.type == Request or P contains a valid Init Cookie option,
         *            (* Must scan the packet's options to check for Init
         *               Cookies.  Only Init Cookies are processed here,
         *               however; other options are processed in Step 8.  This
         *               scan need only be performed if the endpoint uses Init
         *               Cookies *)
         *            (* Generate a new socket and switch to that socket *)
         *            Set S := new socket for this port pair
         *            S.state = RESPOND
         *            Choose S.ISS (initial seqno) or set from Init Cookies
         *            Initialize S.GAR := S.ISS
         *            Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
         *            Continue with S.state == RESPOND
         *            (* A Response packet will be generated in Step 11 *)
         *       Otherwise,
         *            Generate Reset(No Connection) unless P.type == Reset
         *            Drop packet and return
         *
         * NOTE: the check for the packet types is done in
         *       dccp_rcv_state_process
         */
        if (sk->sk_state == DCCP_LISTEN) {
                struct sock *nsk = dccp_v6_hnd_req(sk, skb);

                if (nsk == NULL)
                        goto discard;
                /*
                 * Queue it on the new socket if the new socket is active,
                 * otherwise we just shortcircuit this and continue with
                 * the new socket..
                 */
                if (nsk != sk) {
                        if (dccp_child_process(sk, nsk, skb))
                                goto reset;
                        if (opt_skb != NULL)
                                __kfree_skb(opt_skb);
                        return 0;
                }
        }

        if (dccp_rcv_state_process(sk, skb, dccp_hdr(skb), skb->len))
                goto reset;
        if (opt_skb) {
                /* XXX This is where we would goto ipv6_pktoptions. */
                __kfree_skb(opt_skb);
        }
        return 0;

reset:
        dccp_v6_ctl_send_reset(sk, skb);
discard:
        if (opt_skb != NULL)
                __kfree_skb(opt_skb);
        kfree_skb(skb);
        return 0;
}

static int dccp_v6_rcv(struct sk_buff *skb)
{
        const struct dccp_hdr *dh;
        struct sock *sk;
        int min_cov;

        /* Step 1: Check header basics */

        if (dccp_invalid_packet(skb))
                goto discard_it;

        /* Step 1: If header checksum is incorrect, drop packet and return. */
        if (dccp_v6_csum_finish(skb, &ipv6_hdr(skb)->saddr,
                                     &ipv6_hdr(skb)->daddr)) {
                DCCP_WARN("dropped packet with invalid checksum\n");
                goto discard_it;
        }

        dh = dccp_hdr(skb);

        DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
        DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;

        if (dccp_packet_without_ack(skb))
                DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
        else
                DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);

        /* Step 2:
         *      Look up flow ID in table and get corresponding socket */
        sk = __inet6_lookup_skb(&dccp_hashinfo, skb,
                                dh->dccph_sport, dh->dccph_dport);
        /*
         * Step 2:
         *      If no socket ...
         */
        if (sk == NULL) {
                dccp_pr_debug("failed to look up flow ID in table and "
                              "get corresponding socket\n");
                goto no_dccp_socket;
        }

        /*
         * Step 2:
         *      ... or S.state == TIMEWAIT,
         *              Generate Reset(No Connection) unless P.type == Reset
         *              Drop packet and return
         */
        if (sk->sk_state == DCCP_TIME_WAIT) {
                dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
                inet_twsk_put(inet_twsk(sk));
                goto no_dccp_socket;
        }

        /*
         * RFC 4340, sec. 9.2.1: Minimum Checksum Coverage
         *      o if MinCsCov = 0, only packets with CsCov = 0 are accepted
         *      o if MinCsCov > 0, also accept packets with CsCov >= MinCsCov
         */
        min_cov = dccp_sk(sk)->dccps_pcrlen;
        if (dh->dccph_cscov  &&  (min_cov == 0 || dh->dccph_cscov < min_cov))  {
                dccp_pr_debug("Packet CsCov %d does not satisfy MinCsCov %d\n",
                              dh->dccph_cscov, min_cov);
                /* FIXME: send Data Dropped option (see also dccp_v4_rcv) */
                goto discard_and_relse;
        }

        if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
                goto discard_and_relse;

        return sk_receive_skb(sk, skb, 1) ? -1 : 0;

no_dccp_socket:
        if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
                goto discard_it;
        /*
         * Step 2:
         *      If no socket ...
         *              Generate Reset(No Connection) unless P.type == Reset
         *              Drop packet and return
         */
        if (dh->dccph_type != DCCP_PKT_RESET) {
                DCCP_SKB_CB(skb)->dccpd_reset_code =
                                        DCCP_RESET_CODE_NO_CONNECTION;
                dccp_v6_ctl_send_reset(sk, skb);
        }

discard_it:
        kfree_skb(skb);
        return 0;

discard_and_relse:
        sock_put(sk);
        goto discard_it;
}

static int dccp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
                           int addr_len)
{
        struct sockaddr_in6 *usin = (struct sockaddr_in6 *)uaddr;
        struct inet_connection_sock *icsk = inet_csk(sk);
        struct inet_sock *inet = inet_sk(sk);
        struct ipv6_pinfo *np = inet6_sk(sk);
        struct dccp_sock *dp = dccp_sk(sk);
        struct in6_addr *saddr = NULL, *final_p = NULL, final;
        struct flowi fl;
        struct dst_entry *dst;
        int addr_type;
        int err;

        dp->dccps_role = DCCP_ROLE_CLIENT;

        if (addr_len < SIN6_LEN_RFC2133)
                return -EINVAL;

        if (usin->sin6_family != AF_INET6)
                return -EAFNOSUPPORT;

        memset(&fl, 0, sizeof(fl));

        if (np->sndflow) {
                fl.fl6_flowlabel = usin->sin6_flowinfo & IPV6_FLOWINFO_MASK;
                IP6_ECN_flow_init(fl.fl6_flowlabel);
                if (fl.fl6_flowlabel & IPV6_FLOWLABEL_MASK) {
                        struct ip6_flowlabel *flowlabel;
                        flowlabel = fl6_sock_lookup(sk, fl.fl6_flowlabel);
                        if (flowlabel == NULL)
                                return -EINVAL;
                        ipv6_addr_copy(&usin->sin6_addr, &flowlabel->dst);
                        fl6_sock_release(flowlabel);
                }
        }
        /*
         * connect() to INADDR_ANY means loopback (BSD'ism).
         */
        if (ipv6_addr_any(&usin->sin6_addr))
                usin->sin6_addr.s6_addr[15] = 1;

        addr_type = ipv6_addr_type(&usin->sin6_addr);

        if (addr_type & IPV6_ADDR_MULTICAST)
                return -ENETUNREACH;

        if (addr_type & IPV6_ADDR_LINKLOCAL) {
                if (addr_len >= sizeof(struct sockaddr_in6) &&
                    usin->sin6_scope_id) {
                        /* If interface is set while binding, indices
                         * must coincide.
                         */
                        if (sk->sk_bound_dev_if &&
                            sk->sk_bound_dev_if != usin->sin6_scope_id)
                                return -EINVAL;

                        sk->sk_bound_dev_if = usin->sin6_scope_id;
                }

                /* Connect to link-local address requires an interface */
                if (!sk->sk_bound_dev_if)
                        return -EINVAL;
        }

        ipv6_addr_copy(&np->daddr, &usin->sin6_addr);
        np->flow_label = fl.fl6_flowlabel;

        /*
         * DCCP over IPv4
         */
        if (addr_type == IPV6_ADDR_MAPPED) {
                u32 exthdrlen = icsk->icsk_ext_hdr_len;
                struct sockaddr_in sin;

                SOCK_DEBUG(sk, "connect: ipv4 mapped\n");

                if (__ipv6_only_sock(sk))
                        return -ENETUNREACH;

                sin.sin_family = AF_INET;
                sin.sin_port = usin->sin6_port;
                sin.sin_addr.s_addr = usin->sin6_addr.s6_addr32[3];

                icsk->icsk_af_ops = &dccp_ipv6_mapped;
                sk->sk_backlog_rcv = dccp_v4_do_rcv;

                err = dccp_v4_connect(sk, (struct sockaddr *)&sin, sizeof(sin));
                if (err) {
                        icsk->icsk_ext_hdr_len = exthdrlen;
                        icsk->icsk_af_ops = &dccp_ipv6_af_ops;
                        sk->sk_backlog_rcv = dccp_v6_do_rcv;
                        goto failure;
                }
                ipv6_addr_set_v4mapped(inet->inet_saddr, &np->saddr);
                ipv6_addr_set_v4mapped(inet->inet_rcv_saddr, &np->rcv_saddr);

                return err;
        }

        if (!ipv6_addr_any(&np->rcv_saddr))
                saddr = &np->rcv_saddr;

        fl.proto = IPPROTO_DCCP;
        ipv6_addr_copy(&fl.fl6_dst, &np->daddr);
        ipv6_addr_copy(&fl.fl6_src, saddr ? saddr : &np->saddr);
        fl.oif = sk->sk_bound_dev_if;
        fl.fl_ip_dport = usin->sin6_port;
        fl.fl_ip_sport = inet->inet_sport;
        security_sk_classify_flow(sk, &fl);

        if (np->opt != NULL && np->opt->srcrt != NULL) {
                const struct rt0_hdr *rt0 = (struct rt0_hdr *)np->opt->srcrt;

                ipv6_addr_copy(&final, &fl.fl6_dst);
                ipv6_addr_copy(&fl.fl6_dst, rt0->addr);
                final_p = &final;
        }

        err = ip6_dst_lookup(sk, &dst, &fl);
        if (err)

                goto failure;

        if (final_p)
                ipv6_addr_copy(&fl.fl6_dst, final_p);

        err = __xfrm_lookup(sock_net(sk), &dst, &fl, sk, XFRM_LOOKUP_WAIT);
        if (err < 0) {
                if (err == -EREMOTE)
                        err = ip6_dst_blackhole(sk, &dst, &fl);
                if (err < 0)
                        goto failure;
        }

        if (saddr == NULL) {
                saddr = &fl.fl6_src;
                ipv6_addr_copy(&np->rcv_saddr, saddr);
        }

        /* set the source address */
        ipv6_addr_copy(&np->saddr, saddr);
        inet->inet_rcv_saddr = LOOPBACK4_IPV6;

        __ip6_dst_store(sk, dst, NULL, NULL);

        icsk->icsk_ext_hdr_len = 0;
        if (np->opt != NULL)
                icsk->icsk_ext_hdr_len = (np->opt->opt_flen +
                                          np->opt->opt_nflen);

        inet->inet_dport = usin->sin6_port;

        dccp_set_state(sk, DCCP_REQUESTING);
        err = inet6_hash_connect(&dccp_death_row, sk);
        if (err)
                goto late_failure;

        dp->dccps_iss = secure_dccpv6_sequence_number(np->saddr.s6_addr32,
                                                      np->daddr.s6_addr32,
                                                      inet->inet_sport,
                                                      inet->inet_dport);
        err = dccp_connect(sk);
        if (err)
                goto late_failure;

        return 0;

late_failure:
        dccp_set_state(sk, DCCP_CLOSED);
        __sk_dst_reset(sk);
failure:
        inet->inet_dport = 0;
        sk->sk_route_caps = 0;
        return err;
}

static const struct inet_connection_sock_af_ops dccp_ipv6_af_ops = {
        .queue_xmit        = inet6_csk_xmit,
        .send_check        = dccp_v6_send_check,
        .rebuild_header    = inet6_sk_rebuild_header,
        .conn_request      = dccp_v6_conn_request,
        .syn_recv_sock     = dccp_v6_request_recv_sock,
        .net_header_len    = sizeof(struct ipv6hdr),
        .setsockopt        = ipv6_setsockopt,
        .getsockopt        = ipv6_getsockopt,
        .addr2sockaddr     = inet6_csk_addr2sockaddr,
        .sockaddr_len      = sizeof(struct sockaddr_in6),
        .bind_conflict     = inet6_csk_bind_conflict,
#ifdef CONFIG_COMPAT
        .compat_setsockopt = compat_ipv6_setsockopt,
        .compat_getsockopt = compat_ipv6_getsockopt,
#endif
};

/*
 *      DCCP over IPv4 via INET6 API
 */
static const struct inet_connection_sock_af_ops dccp_ipv6_mapped = {
        .queue_xmit        = ip_queue_xmit,
        .send_check        = dccp_v4_send_check,
        .rebuild_header    = inet_sk_rebuild_header,
        .conn_request      = dccp_v6_conn_request,
        .syn_recv_sock     = dccp_v6_request_recv_sock,
        .net_header_len    = sizeof(struct iphdr),
        .setsockopt        = ipv6_setsockopt,
        .getsockopt        = ipv6_getsockopt,
        .addr2sockaddr     = inet6_csk_addr2sockaddr,
        .sockaddr_len      = sizeof(struct sockaddr_in6),
#ifdef CONFIG_COMPAT
        .compat_setsockopt = compat_ipv6_setsockopt,
        .compat_getsockopt = compat_ipv6_getsockopt,
#endif
};

/* NOTE: A lot of things set to zero explicitly by call to
 *       sk_alloc() so need not be done here.
 */
static int dccp_v6_init_sock(struct sock *sk)
{
        static __u8 dccp_v6_ctl_sock_initialized;
        int err = dccp_init_sock(sk, dccp_v6_ctl_sock_initialized);

        if (err == 0) {
                if (unlikely(!dccp_v6_ctl_sock_initialized))
                        dccp_v6_ctl_sock_initialized = 1;
                inet_csk(sk)->icsk_af_ops = &dccp_ipv6_af_ops;
        }

        return err;
}

static void dccp_v6_destroy_sock(struct sock *sk)
{
        dccp_destroy_sock(sk);
        inet6_destroy_sock(sk);
}

static struct timewait_sock_ops dccp6_timewait_sock_ops = {
        .twsk_obj_size  = sizeof(struct dccp6_timewait_sock),
};

static struct proto dccp_v6_prot = {
        .name              = "DCCPv6",
        .owner             = THIS_MODULE,
        .close             = dccp_close,
        .connect           = dccp_v6_connect,
        .disconnect        = dccp_disconnect,
        .ioctl             = dccp_ioctl,
        .init              = dccp_v6_init_sock,
        .setsockopt        = dccp_setsockopt,
        .getsockopt        = dccp_getsockopt,
        .sendmsg           = dccp_sendmsg,
        .recvmsg           = dccp_recvmsg,
        .backlog_rcv       = dccp_v6_do_rcv,
        .hash              = dccp_v6_hash,
        .unhash            = inet_unhash,
        .accept            = inet_csk_accept,
        .get_port          = inet_csk_get_port,
        .shutdown          = dccp_shutdown,
        .destroy           = dccp_v6_destroy_sock,
        .orphan_count      = &dccp_orphan_count,
        .max_header        = MAX_DCCP_HEADER,
        .obj_size          = sizeof(struct dccp6_sock),
        .slab_flags        = SLAB_DESTROY_BY_RCU,
        .rsk_prot          = &dccp6_request_sock_ops,
        .twsk_prot         = &dccp6_timewait_sock_ops,
        .h.hashinfo        = &dccp_hashinfo,
#ifdef CONFIG_COMPAT
        .compat_setsockopt = compat_dccp_setsockopt,
        .compat_getsockopt = compat_dccp_getsockopt,
#endif
};

static const struct inet6_protocol dccp_v6_protocol = {
        .handler        = dccp_v6_rcv,
        .err_handler    = dccp_v6_err,
        .flags          = INET6_PROTO_NOPOLICY | INET6_PROTO_FINAL,
};

static const struct proto_ops inet6_dccp_ops = {
        .family            = PF_INET6,
        .owner             = THIS_MODULE,
        .release           = inet6_release,
        .bind              = inet6_bind,
        .connect           = inet_stream_connect,
        .socketpair        = sock_no_socketpair,
        .accept            = inet_accept,
        .getname           = inet6_getname,
        .poll              = dccp_poll,
        .ioctl             = inet6_ioctl,
        .listen            = inet_dccp_listen,
        .shutdown          = inet_shutdown,
        .setsockopt        = sock_common_setsockopt,
        .getsockopt        = sock_common_getsockopt,
        .sendmsg           = inet_sendmsg,
        .recvmsg           = sock_common_recvmsg,
        .mmap              = sock_no_mmap,
        .sendpage          = sock_no_sendpage,
#ifdef CONFIG_COMPAT
        .compat_setsockopt = compat_sock_common_setsockopt,
        .compat_getsockopt = compat_sock_common_getsockopt,
#endif
};

static struct inet_protosw dccp_v6_protosw = {
        .type           = SOCK_DCCP,
        .protocol       = IPPROTO_DCCP,
        .prot           = &dccp_v6_prot,
        .ops            = &inet6_dccp_ops,
        .flags          = INET_PROTOSW_ICSK,
};

static int __net_init dccp_v6_init_net(struct net *net)
{
        if (dccp_hashinfo.bhash == NULL)
                return -ESOCKTNOSUPPORT;

        return inet_ctl_sock_create(&net->dccp.v6_ctl_sk, PF_INET6,
                                    SOCK_DCCP, IPPROTO_DCCP, net);
}

static void __net_exit dccp_v6_exit_net(struct net *net)
{
        inet_ctl_sock_destroy(net->dccp.v6_ctl_sk);
}

static struct pernet_operations dccp_v6_ops = {
        .init   = dccp_v6_init_net,
        .exit   = dccp_v6_exit_net,
};

static int __init dccp_v6_init(void)
{
        int err = proto_register(&dccp_v6_prot, 1);

        if (err != 0)
                goto out;

        err = inet6_add_protocol(&dccp_v6_protocol, IPPROTO_DCCP);
        if (err != 0)
                goto out_unregister_proto;

        inet6_register_protosw(&dccp_v6_protosw);

        err = register_pernet_subsys(&dccp_v6_ops);
        if (err != 0)
                goto out_destroy_ctl_sock;
out:
        return err;

out_destroy_ctl_sock:
        inet6_del_protocol(&dccp_v6_protocol, IPPROTO_DCCP);
        inet6_unregister_protosw(&dccp_v6_protosw);
out_unregister_proto:
        proto_unregister(&dccp_v6_prot);
        goto out;
}

static void __exit dccp_v6_exit(void)
{
        unregister_pernet_subsys(&dccp_v6_ops);
        inet6_del_protocol(&dccp_v6_protocol, IPPROTO_DCCP);
        inet6_unregister_protosw(&dccp_v6_protosw);
        proto_unregister(&dccp_v6_prot);
}

module_init(dccp_v6_init);
module_exit(dccp_v6_exit);

/*
 * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
 * values directly, Also cover the case where the protocol is not specified,
 * i.e. net-pf-PF_INET6-proto-0-type-SOCK_DCCP
 */
MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET6, 33, 6);
MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET6, 0, 6);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
MODULE_DESCRIPTION("DCCPv6 - Datagram Congestion Controlled Protocol");