// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      DCCP over IPv6
 *      Linux INET6 implementation
 *
 *      Based on net/dccp6/ipv6.c
 *
 *      Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
 */

#include <linux/module.h>
#include <linux/random.h>
#include <linux/slab.h>
#include <linux/xfrm.h>
#include <linux/string.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 <net/secure_seq.h>
#include <net/netns/generic.h>
#include <net/sock.h>

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

struct dccp_v6_pernet {
        struct sock *v6_ctl_sk;
};

static unsigned int dccp_v6_pernet_id __read_mostly;

/* The per-net 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;

/* add pseudo-header to DCCP checksum stored in skb->csum */
static inline __sum16 dccp_v6_csum_finish(struct sk_buff *skb,
                                      const struct in6_addr *saddr,
                                      const 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, &sk->sk_v6_daddr);
}

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

        /* Only need dccph_dport & dccph_sport which are the first
         * 4 bytes in dccp header.
         * Our caller (icmpv6_notify()) already pulled 8 bytes for us.
         */
        BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_sport) > 8);
        BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_dport) > 8);
        dh = (struct dccp_hdr *)(skb->data + offset);

        sk = __inet6_lookup_established(net, &dccp_hashinfo,
                                        &hdr->daddr, dh->dccph_dport,
                                        &hdr->saddr, ntohs(dh->dccph_sport),
                                        inet6_iif(skb), 0);

        if (!sk) {
                __ICMP6_INC_STATS(net, __in6_dev_get(skb->dev),
                                  ICMP6_MIB_INERRORS);
                return -ENOENT;
        }

        if (sk->sk_state == DCCP_TIME_WAIT) {
                inet_twsk_put(inet_twsk(sk));
                return 0;
        }
        seq = dccp_hdr_seq(dh);
        if (sk->sk_state == DCCP_NEW_SYN_RECV) {
                dccp_req_err(sk, seq);
                return 0;
        }

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

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

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

        np = inet6_sk(sk);

        if (type == NDISC_REDIRECT) {
                if (!sock_owned_by_user(sk)) {
                        struct dst_entry *dst = __sk_dst_check(sk, np->dst_cookie);

                        if (dst)
                                dst->ops->redirect(dst, sk, skb);
                }
                goto out;
        }

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

                if (!ip6_sk_accept_pmtu(sk))
                        goto out;

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

                dst = inet6_csk_update_pmtu(sk, ntohl(info));
                if (!dst)
                        goto out;

                if (inet_csk(sk)->icsk_pmtu_cookie > dst_mtu(dst))
                        dccp_sync_mss(sk, dst_mtu(dst));
                goto out;
        }

        icmpv6_err_convert(type, code, &err);

        /* Might be for an request_sock */
        switch (sk->sk_state) {
        case DCCP_REQUESTING:
        case DCCP_RESPOND:  /* Cannot happen.
                               It can, it SYNs are crossed. --ANK */
                if (!sock_owned_by_user(sk)) {
                        __DCCP_INC_STATS(DCCP_MIB_ATTEMPTFAILS);
                        sk->sk_err = err;
                        /*
                         * Wake people up to see the error
                         * (see connect in sock.c)
                         */
                        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_error_report(sk);
        } else
                sk->sk_err_soft = err;

out:
        bh_unlock_sock(sk);
        sock_put(sk);
        return 0;
}


static int dccp_v6_send_response(const struct sock *sk, struct request_sock *req)
{
        struct inet_request_sock *ireq = inet_rsk(req);
        struct ipv6_pinfo *np = inet6_sk(sk);
        struct sk_buff *skb;
        struct in6_addr *final_p, final;
        struct flowi6 fl6;
        int err = -1;
        struct dst_entry *dst;

        memset(&fl6, 0, sizeof(fl6));
        fl6.flowi6_proto = IPPROTO_DCCP;
        fl6.daddr = ireq->ir_v6_rmt_addr;
        fl6.saddr = ireq->ir_v6_loc_addr;
        fl6.flowlabel = 0;
        fl6.flowi6_oif = ireq->ir_iif;
        fl6.fl6_dport = ireq->ir_rmt_port;
        fl6.fl6_sport = htons(ireq->ir_num);
        security_req_classify_flow(req, flowi6_to_flowi_common(&fl6));


        rcu_read_lock();
        final_p = fl6_update_dst(&fl6, rcu_dereference(np->opt), &final);
        rcu_read_unlock();

        dst = ip6_dst_lookup_flow(sock_net(sk), sk, &fl6, final_p);
        if (IS_ERR(dst)) {
                err = PTR_ERR(dst);
                dst = NULL;
                goto done;
        }

        skb = dccp_make_response(sk, dst, req);
        if (skb != NULL) {
                struct dccp_hdr *dh = dccp_hdr(skb);
                struct ipv6_txoptions *opt;

                dh->dccph_checksum = dccp_v6_csum_finish(skb,
                                                         &ireq->ir_v6_loc_addr,
                                                         &ireq->ir_v6_rmt_addr);
                fl6.daddr = ireq->ir_v6_rmt_addr;
                rcu_read_lock();
                opt = ireq->ipv6_opt;
                if (!opt)
                        opt = rcu_dereference(np->opt);
                err = ip6_xmit(sk, skb, &fl6, sk->sk_mark, opt, np->tclass,
                               sk->sk_priority);
                rcu_read_unlock();
                err = net_xmit_eval(err);
        }

done:
        dst_release(dst);
        return err;
}

static void dccp_v6_reqsk_destructor(struct request_sock *req)
{
        dccp_feat_list_purge(&dccp_rsk(req)->dreq_featneg);
        kfree(inet_rsk(req)->ipv6_opt);
        kfree_skb(inet_rsk(req)->pktopts);
}

static void dccp_v6_ctl_send_reset(const struct sock *sk, struct sk_buff *rxskb)
{
        const struct ipv6hdr *rxip6h;
        struct sk_buff *skb;
        struct flowi6 fl6;
        struct net *net = dev_net(skb_dst(rxskb)->dev);
        struct dccp_v6_pernet *pn;
        struct sock *ctl_sk;
        struct dst_entry *dst;

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

        if (!ipv6_unicast_destination(rxskb))
                return;

        pn = net_generic(net, dccp_v6_pernet_id);
        ctl_sk = pn->v6_ctl_sk;
        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(&fl6, 0, sizeof(fl6));
        fl6.daddr = rxip6h->saddr;
        fl6.saddr = rxip6h->daddr;

        fl6.flowi6_proto = IPPROTO_DCCP;
        fl6.flowi6_oif = inet6_iif(rxskb);
        fl6.fl6_dport = dccp_hdr(skb)->dccph_dport;
        fl6.fl6_sport = dccp_hdr(skb)->dccph_sport;
        security_skb_classify_flow(rxskb, flowi6_to_flowi_common(&fl6));

        /* sk = NULL, but it is safe for now. RST socket required. */
        dst = ip6_dst_lookup_flow(sock_net(ctl_sk), ctl_sk, &fl6, NULL);
        if (!IS_ERR(dst)) {
                skb_dst_set(skb, dst);
                ip6_xmit(ctl_sk, skb, &fl6, 0, NULL, 0, 0);
                DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
                DCCP_INC_STATS(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,
        .syn_ack_timeout = dccp_syn_ack_timeout,
};

static int dccp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
{
        struct request_sock *req;
        struct dccp_request_sock *dreq;
        struct inet_request_sock *ireq;
        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 (ipv6_addr_v4mapped(&ipv6_hdr(skb)->saddr)) {
                __IP6_INC_STATS(sock_net(sk), NULL, IPSTATS_MIB_INHDRERRORS);
                return 0;
        }

        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))
                goto drop;

        req = inet_reqsk_alloc(&dccp6_request_sock_ops, sk, true);
        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;

        ireq = inet_rsk(req);
        ireq->ir_v6_rmt_addr = ipv6_hdr(skb)->saddr;
        ireq->ir_v6_loc_addr = ipv6_hdr(skb)->daddr;
        ireq->ireq_family = AF_INET6;
        ireq->ir_mark = inet_request_mark(sk, skb);

        if (ipv6_opt_accepted(sk, skb, IP6CB(skb)) ||
            np->rxopt.bits.rxinfo || np->rxopt.bits.rxoinfo ||
            np->rxopt.bits.rxhlim || np->rxopt.bits.rxohlim) {
                refcount_inc(&skb->users);
                ireq->pktopts = skb;
        }
        ireq->ir_iif = sk->sk_bound_dev_if;

        /* So that link locals have meaning */
        if (!sk->sk_bound_dev_if &&
            ipv6_addr_type(&ireq->ir_v6_rmt_addr) & IPV6_ADDR_LINKLOCAL)
                ireq->ir_iif = inet6_iif(skb);

        /*
         * Step 3: Process LISTEN state
         *
         *   Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
         *
         * Setting S.SWL/S.SWH to is deferred to dccp_create_openreq_child().
         */
        dreq->dreq_isr     = dcb->dccpd_seq;
        dreq->dreq_gsr     = dreq->dreq_isr;
        dreq->dreq_iss     = dccp_v6_init_sequence(skb);
        dreq->dreq_gss     = dreq->dreq_iss;
        dreq->dreq_service = service;

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

        inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
        reqsk_put(req);
        return 0;

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

static struct sock *dccp_v6_request_recv_sock(const struct sock *sk,
                                              struct sk_buff *skb,
                                              struct request_sock *req,
                                              struct dst_entry *dst,
                                              struct request_sock *req_unhash,
                                              bool *own_req)
{
        struct inet_request_sock *ireq = inet_rsk(req);
        struct ipv6_pinfo *newnp;
        const struct ipv6_pinfo *np = inet6_sk(sk);
        struct ipv6_txoptions *opt;
        struct inet_sock *newinet;
        struct dccp6_sock *newdp6;
        struct sock *newsk;

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

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

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

                newnp->saddr = newsk->sk_v6_rcv_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->ipv6_mc_list = NULL;
                newnp->ipv6_ac_list = NULL;
                newnp->ipv6_fl_list = NULL;
                newnp->mcast_oif   = inet_iif(skb);
                newnp->mcast_hops  = ip_hdr(skb)->ttl;

                /*
                 * 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;
        }


        if (sk_acceptq_is_full(sk))
                goto out_overflow;

        if (!dst) {
                struct flowi6 fl6;

                dst = inet6_csk_route_req(sk, &fl6, req, IPPROTO_DCCP);
                if (!dst)
                        goto out;
        }

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

        /*
         * 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;
        newnp = inet6_sk(newsk);

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

        newsk->sk_v6_daddr      = ireq->ir_v6_rmt_addr;
        newnp->saddr            = ireq->ir_v6_loc_addr;
        newsk->sk_v6_rcv_saddr  = ireq->ir_v6_loc_addr;
        newsk->sk_bound_dev_if  = ireq->ir_iif;

        /* Now IPv6 options...

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

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

        newnp->ipv6_mc_list = NULL;
        newnp->ipv6_ac_list = NULL;
        newnp->ipv6_fl_list = NULL;
        newnp->pktoptions = NULL;
        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.
         */
        opt = ireq->ipv6_opt;
        if (!opt)
                opt = rcu_dereference(np->opt);
        if (opt) {
                opt = ipv6_dup_options(newsk, opt);
                RCU_INIT_POINTER(newnp->opt, opt);
        }
        inet_csk(newsk)->icsk_ext_hdr_len = 0;
        if (opt)
                inet_csk(newsk)->icsk_ext_hdr_len = opt->opt_nflen +
                                                    opt->opt_flen;

        dccp_sync_mss(newsk, dst_mtu(dst));

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

        if (__inet_inherit_port(sk, newsk) < 0) {
                inet_csk_prepare_forced_close(newsk);
                dccp_done(newsk);
                goto out;
        }
        *own_req = inet_ehash_nolisten(newsk, req_to_sk(req_unhash), NULL);
        /* Clone pktoptions received with SYN, if we own the req */
        if (*own_req && ireq->pktopts) {
                newnp->pktoptions = skb_clone(ireq->pktopts, GFP_ATOMIC);
                consume_skb(ireq->pktopts);
                ireq->pktopts = NULL;
                if (newnp->pktoptions)
                        skb_set_owner_r(newnp->pktoptions, newsk);
        }

        return newsk;

out_overflow:
        __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
out_nonewsk:
        dst_release(dst);
out:
        __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENDROPS);
        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)
                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)
                        goto ipv6_pktoptions;
                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 (dccp_rcv_state_process(sk, skb, dccp_hdr(skb), skb->len))
                goto reset;
        if (opt_skb)
                goto ipv6_pktoptions;
        return 0;

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

/* Handling IPV6_PKTOPTIONS skb the similar
 * way it's done for net/ipv6/tcp_ipv6.c
 */
ipv6_pktoptions:
        if (!((1 << sk->sk_state) & (DCCPF_CLOSED | DCCPF_LISTEN))) {
                if (np->rxopt.bits.rxinfo || np->rxopt.bits.rxoinfo)
                        np->mcast_oif = inet6_iif(opt_skb);
                if (np->rxopt.bits.rxhlim || np->rxopt.bits.rxohlim)
                        np->mcast_hops = ipv6_hdr(opt_skb)->hop_limit;
                if (np->rxopt.bits.rxflow || np->rxopt.bits.rxtclass)
                        np->rcv_flowinfo = ip6_flowinfo(ipv6_hdr(opt_skb));
                if (np->repflow)
                        np->flow_label = ip6_flowlabel(ipv6_hdr(opt_skb));
                if (ipv6_opt_accepted(sk, opt_skb,
                                      &DCCP_SKB_CB(opt_skb)->header.h6)) {
                        skb_set_owner_r(opt_skb, sk);
                        memmove(IP6CB(opt_skb),
                                &DCCP_SKB_CB(opt_skb)->header.h6,
                                sizeof(struct inet6_skb_parm));
                        opt_skb = xchg(&np->pktoptions, opt_skb);
                } else {
                        __kfree_skb(opt_skb);
                        opt_skb = xchg(&np->pktoptions, NULL);
                }
        }

        kfree_skb(opt_skb);
        return 0;
}

static int dccp_v6_rcv(struct sk_buff *skb)
{
        const struct dccp_hdr *dh;
        bool refcounted;
        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);

lookup:
        sk = __inet6_lookup_skb(&dccp_hashinfo, skb, __dccp_hdr_len(dh),
                                dh->dccph_sport, dh->dccph_dport,
                                inet6_iif(skb), 0, &refcounted);
        if (!sk) {
                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;
        }

        if (sk->sk_state == DCCP_NEW_SYN_RECV) {
                struct request_sock *req = inet_reqsk(sk);
                struct sock *nsk;

                sk = req->rsk_listener;
                if (unlikely(sk->sk_state != DCCP_LISTEN)) {
                        inet_csk_reqsk_queue_drop_and_put(sk, req);
                        goto lookup;
                }
                sock_hold(sk);
                refcounted = true;
                nsk = dccp_check_req(sk, skb, req);
                if (!nsk) {
                        reqsk_put(req);
                        goto discard_and_relse;
                }
                if (nsk == sk) {
                        reqsk_put(req);
                } else if (dccp_child_process(sk, nsk, skb)) {
                        dccp_v6_ctl_send_reset(sk, skb);
                        goto discard_and_relse;
                } else {
                        sock_put(sk);
                        return 0;
                }
        }
        /*
         * 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, dh->dccph_doff * 4,
                                refcounted) ? -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:
        if (refcounted)
                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, final;
        struct ipv6_txoptions *opt;
        struct flowi6 fl6;
        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(&fl6, 0, sizeof(fl6));

        if (np->sndflow) {
                fl6.flowlabel = usin->sin6_flowinfo & IPV6_FLOWINFO_MASK;
                IP6_ECN_flow_init(fl6.flowlabel);
                if (fl6.flowlabel & IPV6_FLOWLABEL_MASK) {
                        struct ip6_flowlabel *flowlabel;
                        flowlabel = fl6_sock_lookup(sk, fl6.flowlabel);
                        if (IS_ERR(flowlabel))
                                return -EINVAL;
                        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;
        }

        sk->sk_v6_daddr = usin->sin6_addr;
        np->flow_label = 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;
                }
                np->saddr = sk->sk_v6_rcv_saddr;
                return err;
        }

        if (!ipv6_addr_any(&sk->sk_v6_rcv_saddr))
                saddr = &sk->sk_v6_rcv_saddr;

        fl6.flowi6_proto = IPPROTO_DCCP;
        fl6.daddr = sk->sk_v6_daddr;
        fl6.saddr = saddr ? *saddr : np->saddr;
        fl6.flowi6_oif = sk->sk_bound_dev_if;
        fl6.fl6_dport = usin->sin6_port;
        fl6.fl6_sport = inet->inet_sport;
        security_sk_classify_flow(sk, flowi6_to_flowi_common(&fl6));

        opt = rcu_dereference_protected(np->opt, lockdep_sock_is_held(sk));
        final_p = fl6_update_dst(&fl6, opt, &final);

        dst = ip6_dst_lookup_flow(sock_net(sk), sk, &fl6, final_p);
        if (IS_ERR(dst)) {
                err = PTR_ERR(dst);
                goto failure;
        }

        if (saddr == NULL) {
                saddr = &fl6.saddr;
                sk->sk_v6_rcv_saddr = *saddr;
        }

        /* set the source address */
        np->saddr = *saddr;
        inet->inet_rcv_saddr = LOOPBACK4_IPV6;

        ip6_dst_store(sk, dst, NULL, NULL);

        icsk->icsk_ext_hdr_len = 0;
        if (opt)
                icsk->icsk_ext_hdr_len = opt->opt_flen + 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,
                                                      sk->sk_v6_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),
};

/*
 *      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),
};

/* 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              = inet6_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_TYPESAFE_BY_RCU,
        .rsk_prot          = &dccp6_request_sock_ops,
        .twsk_prot         = &dccp6_timewait_sock_ops,
        .h.hashinfo        = &dccp_hashinfo,
};

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,
        .gettstamp         = sock_gettstamp,
        .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_ioctl      = inet6_compat_ioctl,
#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)
{
        struct dccp_v6_pernet *pn = net_generic(net, dccp_v6_pernet_id);

        if (dccp_hashinfo.bhash == NULL)
                return -ESOCKTNOSUPPORT;

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

static void __net_exit dccp_v6_exit_net(struct net *net)
{
        struct dccp_v6_pernet *pn = net_generic(net, dccp_v6_pernet_id);

        inet_ctl_sock_destroy(pn->v6_ctl_sk);
}

static void __net_exit dccp_v6_exit_batch(struct list_head *net_exit_list)
{
        inet_twsk_purge(&dccp_hashinfo, AF_INET6);
}

static struct pernet_operations dccp_v6_ops = {
        .init   = dccp_v6_init_net,
        .exit   = dccp_v6_exit_net,
        .exit_batch = dccp_v6_exit_batch,
        .id     = &dccp_v6_pernet_id,
        .size   = sizeof(struct dccp_v6_pernet),
};

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

        if (err)
                goto out;

        inet6_register_protosw(&dccp_v6_protosw);

        err = register_pernet_subsys(&dccp_v6_ops);
        if (err)
                goto out_destroy_ctl_sock;

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

out:
        return err;
out_unregister_proto:
        unregister_pernet_subsys(&dccp_v6_ops);
out_destroy_ctl_sock:
        inet6_unregister_protosw(&dccp_v6_protosw);
        proto_unregister(&dccp_v6_prot);
        goto out;
}

static void __exit dccp_v6_exit(void)
{
        inet6_del_protocol(&dccp_v6_protocol, IPPROTO_DCCP);
        unregister_pernet_subsys(&dccp_v6_ops);
        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");