/*
 * DCCP connection tracking protocol helper
 *
 * Copyright (c) 2005, 2006, 2008 Patrick McHardy <kaber@trash.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sysctl.h>
#include <linux/spinlock.h>
#include <linux/skbuff.h>
#include <linux/dccp.h>
#include <linux/slab.h>

#include <net/net_namespace.h>
#include <net/netns/generic.h>

#include <linux/netfilter/nfnetlink_conntrack.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_l4proto.h>
#include <net/netfilter/nf_conntrack_ecache.h>
#include <net/netfilter/nf_log.h>

/* Timeouts are based on values from RFC4340:
 *
 * - REQUEST:
 *
 *   8.1.2. Client Request
 *
 *   A client MAY give up on its DCCP-Requests after some time
 *   (3 minutes, for example).
 *
 * - RESPOND:
 *
 *   8.1.3. Server Response
 *
 *   It MAY also leave the RESPOND state for CLOSED after a timeout of
 *   not less than 4MSL (8 minutes);
 *
 * - PARTOPEN:
 *
 *   8.1.5. Handshake Completion
 *
 *   If the client remains in PARTOPEN for more than 4MSL (8 minutes),
 *   it SHOULD reset the connection with Reset Code 2, "Aborted".
 *
 * - OPEN:
 *
 *   The DCCP timestamp overflows after 11.9 hours. If the connection
 *   stays idle this long the sequence number won't be recognized
 *   as valid anymore.
 *
 * - CLOSEREQ/CLOSING:
 *
 *   8.3. Termination
 *
 *   The retransmission timer should initially be set to go off in two
 *   round-trip times and should back off to not less than once every
 *   64 seconds ...
 *
 * - TIMEWAIT:
 *
 *   4.3. States
 *
 *   A server or client socket remains in this state for 2MSL (4 minutes)
 *   after the connection has been town down, ...
 */

#define DCCP_MSL (2 * 60 * HZ)

static const char * const dccp_state_names[] = {
        [CT_DCCP_NONE]          = "NONE",
        [CT_DCCP_REQUEST]       = "REQUEST",
        [CT_DCCP_RESPOND]       = "RESPOND",
        [CT_DCCP_PARTOPEN]      = "PARTOPEN",
        [CT_DCCP_OPEN]          = "OPEN",
        [CT_DCCP_CLOSEREQ]      = "CLOSEREQ",
        [CT_DCCP_CLOSING]       = "CLOSING",
        [CT_DCCP_TIMEWAIT]      = "TIMEWAIT",
        [CT_DCCP_IGNORE]        = "IGNORE",
        [CT_DCCP_INVALID]       = "INVALID",
};

#define sNO     CT_DCCP_NONE
#define sRQ     CT_DCCP_REQUEST
#define sRS     CT_DCCP_RESPOND
#define sPO     CT_DCCP_PARTOPEN
#define sOP     CT_DCCP_OPEN
#define sCR     CT_DCCP_CLOSEREQ
#define sCG     CT_DCCP_CLOSING
#define sTW     CT_DCCP_TIMEWAIT
#define sIG     CT_DCCP_IGNORE
#define sIV     CT_DCCP_INVALID

/*
 * DCCP state transition table
 *
 * The assumption is the same as for TCP tracking:
 *
 * We are the man in the middle. All the packets go through us but might
 * get lost in transit to the destination. It is assumed that the destination
 * can't receive segments we haven't seen.
 *
 * The following states exist:
 *
 * NONE:        Initial state, expecting Request
 * REQUEST:     Request seen, waiting for Response from server
 * RESPOND:     Response from server seen, waiting for Ack from client
 * PARTOPEN:    Ack after Response seen, waiting for packet other than Response,
 *              Reset or Sync from server
 * OPEN:        Packet other than Response, Reset or Sync seen
 * CLOSEREQ:    CloseReq from server seen, expecting Close from client
 * CLOSING:     Close seen, expecting Reset
 * TIMEWAIT:    Reset seen
 * IGNORE:      Not determinable whether packet is valid
 *
 * Some states exist only on one side of the connection: REQUEST, RESPOND,
 * PARTOPEN, CLOSEREQ. For the other side these states are equivalent to
 * the one it was in before.
 *
 * Packets are marked as ignored (sIG) if we don't know if they're valid
 * (for example a reincarnation of a connection we didn't notice is dead
 * already) and the server may send back a connection closing Reset or a
 * Response. They're also used for Sync/SyncAck packets, which we don't
 * care about.
 */
static const u_int8_t
dccp_state_table[CT_DCCP_ROLE_MAX + 1][DCCP_PKT_SYNCACK + 1][CT_DCCP_MAX + 1] = {
        [CT_DCCP_ROLE_CLIENT] = {
                [DCCP_PKT_REQUEST] = {
                /*
                 * sNO -> sRQ           Regular Request
                 * sRQ -> sRQ           Retransmitted Request or reincarnation
                 * sRS -> sRS           Retransmitted Request (apparently Response
                 *                      got lost after we saw it) or reincarnation
                 * sPO -> sIG           Ignore, conntrack might be out of sync
                 * sOP -> sIG           Ignore, conntrack might be out of sync
                 * sCR -> sIG           Ignore, conntrack might be out of sync
                 * sCG -> sIG           Ignore, conntrack might be out of sync
                 * sTW -> sRQ           Reincarnation
                 *
                 *      sNO, sRQ, sRS, sPO. sOP, sCR, sCG, sTW, */
                        sRQ, sRQ, sRS, sIG, sIG, sIG, sIG, sRQ,
                },
                [DCCP_PKT_RESPONSE] = {
                /*
                 * sNO -> sIV           Invalid
                 * sRQ -> sIG           Ignore, might be response to ignored Request
                 * sRS -> sIG           Ignore, might be response to ignored Request
                 * sPO -> sIG           Ignore, might be response to ignored Request
                 * sOP -> sIG           Ignore, might be response to ignored Request
                 * sCR -> sIG           Ignore, might be response to ignored Request
                 * sCG -> sIG           Ignore, might be response to ignored Request
                 * sTW -> sIV           Invalid, reincarnation in reverse direction
                 *                      goes through sRQ
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIV, sIG, sIG, sIG, sIG, sIG, sIG, sIV,
                },
                [DCCP_PKT_ACK] = {
                /*
                 * sNO -> sIV           No connection
                 * sRQ -> sIV           No connection
                 * sRS -> sPO           Ack for Response, move to PARTOPEN (8.1.5.)
                 * sPO -> sPO           Retransmitted Ack for Response, remain in PARTOPEN
                 * sOP -> sOP           Regular ACK, remain in OPEN
                 * sCR -> sCR           Ack in CLOSEREQ MAY be processed (8.3.)
                 * sCG -> sCG           Ack in CLOSING MAY be processed (8.3.)
                 * sTW -> sIV
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIV, sIV, sPO, sPO, sOP, sCR, sCG, sIV
                },
                [DCCP_PKT_DATA] = {
                /*
                 * sNO -> sIV           No connection
                 * sRQ -> sIV           No connection
                 * sRS -> sIV           No connection
                 * sPO -> sIV           MUST use DataAck in PARTOPEN state (8.1.5.)
                 * sOP -> sOP           Regular Data packet
                 * sCR -> sCR           Data in CLOSEREQ MAY be processed (8.3.)
                 * sCG -> sCG           Data in CLOSING MAY be processed (8.3.)
                 * sTW -> sIV
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIV, sIV, sIV, sIV, sOP, sCR, sCG, sIV,
                },
                [DCCP_PKT_DATAACK] = {
                /*
                 * sNO -> sIV           No connection
                 * sRQ -> sIV           No connection
                 * sRS -> sPO           Ack for Response, move to PARTOPEN (8.1.5.)
                 * sPO -> sPO           Remain in PARTOPEN state
                 * sOP -> sOP           Regular DataAck packet in OPEN state
                 * sCR -> sCR           DataAck in CLOSEREQ MAY be processed (8.3.)
                 * sCG -> sCG           DataAck in CLOSING MAY be processed (8.3.)
                 * sTW -> sIV
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIV, sIV, sPO, sPO, sOP, sCR, sCG, sIV
                },
                [DCCP_PKT_CLOSEREQ] = {
                /*
                 * CLOSEREQ may only be sent by the server.
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV
                },
                [DCCP_PKT_CLOSE] = {
                /*
                 * sNO -> sIV           No connection
                 * sRQ -> sIV           No connection
                 * sRS -> sIV           No connection
                 * sPO -> sCG           Client-initiated close
                 * sOP -> sCG           Client-initiated close
                 * sCR -> sCG           Close in response to CloseReq (8.3.)
                 * sCG -> sCG           Retransmit
                 * sTW -> sIV           Late retransmit, already in TIME_WAIT
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIV, sIV, sIV, sCG, sCG, sCG, sIV, sIV
                },
                [DCCP_PKT_RESET] = {
                /*
                 * sNO -> sIV           No connection
                 * sRQ -> sTW           Sync received or timeout, SHOULD send Reset (8.1.1.)
                 * sRS -> sTW           Response received without Request
                 * sPO -> sTW           Timeout, SHOULD send Reset (8.1.5.)
                 * sOP -> sTW           Connection reset
                 * sCR -> sTW           Connection reset
                 * sCG -> sTW           Connection reset
                 * sTW -> sIG           Ignore (don't refresh timer)
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIV, sTW, sTW, sTW, sTW, sTW, sTW, sIG
                },
                [DCCP_PKT_SYNC] = {
                /*
                 * We currently ignore Sync packets
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIG, sIG, sIG, sIG, sIG, sIG, sIG, sIG,
                },
                [DCCP_PKT_SYNCACK] = {
                /*
                 * We currently ignore SyncAck packets
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIG, sIG, sIG, sIG, sIG, sIG, sIG, sIG,
                },
        },
        [CT_DCCP_ROLE_SERVER] = {
                [DCCP_PKT_REQUEST] = {
                /*
                 * sNO -> sIV           Invalid
                 * sRQ -> sIG           Ignore, conntrack might be out of sync
                 * sRS -> sIG           Ignore, conntrack might be out of sync
                 * sPO -> sIG           Ignore, conntrack might be out of sync
                 * sOP -> sIG           Ignore, conntrack might be out of sync
                 * sCR -> sIG           Ignore, conntrack might be out of sync
                 * sCG -> sIG           Ignore, conntrack might be out of sync
                 * sTW -> sRQ           Reincarnation, must reverse roles
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIV, sIG, sIG, sIG, sIG, sIG, sIG, sRQ
                },
                [DCCP_PKT_RESPONSE] = {
                /*
                 * sNO -> sIV           Response without Request
                 * sRQ -> sRS           Response to clients Request
                 * sRS -> sRS           Retransmitted Response (8.1.3. SHOULD NOT)
                 * sPO -> sIG           Response to an ignored Request or late retransmit
                 * sOP -> sIG           Ignore, might be response to ignored Request
                 * sCR -> sIG           Ignore, might be response to ignored Request
                 * sCG -> sIG           Ignore, might be response to ignored Request
                 * sTW -> sIV           Invalid, Request from client in sTW moves to sRQ
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIV, sRS, sRS, sIG, sIG, sIG, sIG, sIV
                },
                [DCCP_PKT_ACK] = {
                /*
                 * sNO -> sIV           No connection
                 * sRQ -> sIV           No connection
                 * sRS -> sIV           No connection
                 * sPO -> sOP           Enter OPEN state (8.1.5.)
                 * sOP -> sOP           Regular Ack in OPEN state
                 * sCR -> sIV           Waiting for Close from client
                 * sCG -> sCG           Ack in CLOSING MAY be processed (8.3.)
                 * sTW -> sIV
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIV, sIV, sIV, sOP, sOP, sIV, sCG, sIV
                },
                [DCCP_PKT_DATA] = {
                /*
                 * sNO -> sIV           No connection
                 * sRQ -> sIV           No connection
                 * sRS -> sIV           No connection
                 * sPO -> sOP           Enter OPEN state (8.1.5.)
                 * sOP -> sOP           Regular Data packet in OPEN state
                 * sCR -> sIV           Waiting for Close from client
                 * sCG -> sCG           Data in CLOSING MAY be processed (8.3.)
                 * sTW -> sIV
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIV, sIV, sIV, sOP, sOP, sIV, sCG, sIV
                },
                [DCCP_PKT_DATAACK] = {
                /*
                 * sNO -> sIV           No connection
                 * sRQ -> sIV           No connection
                 * sRS -> sIV           No connection
                 * sPO -> sOP           Enter OPEN state (8.1.5.)
                 * sOP -> sOP           Regular DataAck in OPEN state
                 * sCR -> sIV           Waiting for Close from client
                 * sCG -> sCG           Data in CLOSING MAY be processed (8.3.)
                 * sTW -> sIV
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIV, sIV, sIV, sOP, sOP, sIV, sCG, sIV
                },
                [DCCP_PKT_CLOSEREQ] = {
                /*
                 * sNO -> sIV           No connection
                 * sRQ -> sIV           No connection
                 * sRS -> sIV           No connection
                 * sPO -> sOP -> sCR    Move directly to CLOSEREQ (8.1.5.)
                 * sOP -> sCR           CloseReq in OPEN state
                 * sCR -> sCR           Retransmit
                 * sCG -> sCR           Simultaneous close, client sends another Close
                 * sTW -> sIV           Already closed
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIV, sIV, sIV, sCR, sCR, sCR, sCR, sIV
                },
                [DCCP_PKT_CLOSE] = {
                /*
                 * sNO -> sIV           No connection
                 * sRQ -> sIV           No connection
                 * sRS -> sIV           No connection
                 * sPO -> sOP -> sCG    Move direcly to CLOSING
                 * sOP -> sCG           Move to CLOSING
                 * sCR -> sIV           Close after CloseReq is invalid
                 * sCG -> sCG           Retransmit
                 * sTW -> sIV           Already closed
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIV, sIV, sIV, sCG, sCG, sIV, sCG, sIV
                },
                [DCCP_PKT_RESET] = {
                /*
                 * sNO -> sIV           No connection
                 * sRQ -> sTW           Reset in response to Request
                 * sRS -> sTW           Timeout, SHOULD send Reset (8.1.3.)
                 * sPO -> sTW           Timeout, SHOULD send Reset (8.1.3.)
                 * sOP -> sTW
                 * sCR -> sTW
                 * sCG -> sTW
                 * sTW -> sIG           Ignore (don't refresh timer)
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW, sTW */
                        sIV, sTW, sTW, sTW, sTW, sTW, sTW, sTW, sIG
                },
                [DCCP_PKT_SYNC] = {
                /*
                 * We currently ignore Sync packets
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIG, sIG, sIG, sIG, sIG, sIG, sIG, sIG,
                },
                [DCCP_PKT_SYNCACK] = {
                /*
                 * We currently ignore SyncAck packets
                 *
                 *      sNO, sRQ, sRS, sPO, sOP, sCR, sCG, sTW */
                        sIG, sIG, sIG, sIG, sIG, sIG, sIG, sIG,
                },
        },
};

/* this module per-net specifics */
static int dccp_net_id __read_mostly;
struct dccp_net {
        struct nf_proto_net pn;
        int dccp_loose;
        unsigned int dccp_timeout[CT_DCCP_MAX + 1];
};

static inline struct dccp_net *dccp_pernet(struct net *net)
{
        return net_generic(net, dccp_net_id);
}

static bool dccp_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
                              struct nf_conntrack_tuple *tuple)
{
        struct dccp_hdr _hdr, *dh;

        dh = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
        if (dh == NULL)
                return false;

        tuple->src.u.dccp.port = dh->dccph_sport;
        tuple->dst.u.dccp.port = dh->dccph_dport;
        return true;
}

static bool dccp_invert_tuple(struct nf_conntrack_tuple *inv,
                              const struct nf_conntrack_tuple *tuple)
{
        inv->src.u.dccp.port = tuple->dst.u.dccp.port;
        inv->dst.u.dccp.port = tuple->src.u.dccp.port;
        return true;
}

static bool dccp_new(struct nf_conn *ct, const struct sk_buff *skb,
                     unsigned int dataoff, unsigned int *timeouts)
{
        struct net *net = nf_ct_net(ct);
        struct dccp_net *dn;
        struct dccp_hdr _dh, *dh;
        const char *msg;
        u_int8_t state;

        dh = skb_header_pointer(skb, dataoff, sizeof(_dh), &dh);
        BUG_ON(dh == NULL);

        state = dccp_state_table[CT_DCCP_ROLE_CLIENT][dh->dccph_type][CT_DCCP_NONE];
        switch (state) {
        default:
                dn = dccp_pernet(net);
                if (dn->dccp_loose == 0) {
                        msg = "nf_ct_dccp: not picking up existing connection ";
                        goto out_invalid;
                }
        case CT_DCCP_REQUEST:
                break;
        case CT_DCCP_INVALID:
                msg = "nf_ct_dccp: invalid state transition ";
                goto out_invalid;
        }

        ct->proto.dccp.role[IP_CT_DIR_ORIGINAL] = CT_DCCP_ROLE_CLIENT;
        ct->proto.dccp.role[IP_CT_DIR_REPLY] = CT_DCCP_ROLE_SERVER;
        ct->proto.dccp.state = CT_DCCP_NONE;
        ct->proto.dccp.last_pkt = DCCP_PKT_REQUEST;
        ct->proto.dccp.last_dir = IP_CT_DIR_ORIGINAL;
        ct->proto.dccp.handshake_seq = 0;
        return true;

out_invalid:
        if (LOG_INVALID(net, IPPROTO_DCCP))
                nf_log_packet(net, nf_ct_l3num(ct), 0, skb, NULL, NULL,
                              NULL, msg);
        return false;
}

static u64 dccp_ack_seq(const struct dccp_hdr *dh)
{
        const struct dccp_hdr_ack_bits *dhack;

        dhack = (void *)dh + __dccp_basic_hdr_len(dh);
        return ((u64)ntohs(dhack->dccph_ack_nr_high) << 32) +
                     ntohl(dhack->dccph_ack_nr_low);
}

static unsigned int *dccp_get_timeouts(struct net *net)
{
        return dccp_pernet(net)->dccp_timeout;
}

static int dccp_packet(struct nf_conn *ct, const struct sk_buff *skb,
                       unsigned int dataoff, enum ip_conntrack_info ctinfo,
                       u_int8_t pf, unsigned int hooknum,
                       unsigned int *timeouts)
{
        struct net *net = nf_ct_net(ct);
        enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
        struct dccp_hdr _dh, *dh;
        u_int8_t type, old_state, new_state;
        enum ct_dccp_roles role;

        dh = skb_header_pointer(skb, dataoff, sizeof(_dh), &dh);
        BUG_ON(dh == NULL);
        type = dh->dccph_type;

        if (type == DCCP_PKT_RESET &&
            !test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
                /* Tear down connection immediately if only reply is a RESET */
                nf_ct_kill_acct(ct, ctinfo, skb);
                return NF_ACCEPT;
        }

        spin_lock_bh(&ct->lock);

        role = ct->proto.dccp.role[dir];
        old_state = ct->proto.dccp.state;
        new_state = dccp_state_table[role][type][old_state];

        switch (new_state) {
        case CT_DCCP_REQUEST:
                if (old_state == CT_DCCP_TIMEWAIT &&
                    role == CT_DCCP_ROLE_SERVER) {
                        /* Reincarnation in the reverse direction: reopen and
                         * reverse client/server roles. */
                        ct->proto.dccp.role[dir] = CT_DCCP_ROLE_CLIENT;
                        ct->proto.dccp.role[!dir] = CT_DCCP_ROLE_SERVER;
                }
                break;
        case CT_DCCP_RESPOND:
                if (old_state == CT_DCCP_REQUEST)
                        ct->proto.dccp.handshake_seq = dccp_hdr_seq(dh);
                break;
        case CT_DCCP_PARTOPEN:
                if (old_state == CT_DCCP_RESPOND &&
                    type == DCCP_PKT_ACK &&
                    dccp_ack_seq(dh) == ct->proto.dccp.handshake_seq)
                        set_bit(IPS_ASSURED_BIT, &ct->status);
                break;
        case CT_DCCP_IGNORE:
                /*
                 * Connection tracking might be out of sync, so we ignore
                 * packets that might establish a new connection and resync
                 * if the server responds with a valid Response.
                 */
                if (ct->proto.dccp.last_dir == !dir &&
                    ct->proto.dccp.last_pkt == DCCP_PKT_REQUEST &&
                    type == DCCP_PKT_RESPONSE) {
                        ct->proto.dccp.role[!dir] = CT_DCCP_ROLE_CLIENT;
                        ct->proto.dccp.role[dir] = CT_DCCP_ROLE_SERVER;
                        ct->proto.dccp.handshake_seq = dccp_hdr_seq(dh);
                        new_state = CT_DCCP_RESPOND;
                        break;
                }
                ct->proto.dccp.last_dir = dir;
                ct->proto.dccp.last_pkt = type;

                spin_unlock_bh(&ct->lock);
                if (LOG_INVALID(net, IPPROTO_DCCP))
                        nf_log_packet(net, pf, 0, skb, NULL, NULL, NULL,
                                      "nf_ct_dccp: invalid packet ignored ");
                return NF_ACCEPT;
        case CT_DCCP_INVALID:
                spin_unlock_bh(&ct->lock);
                if (LOG_INVALID(net, IPPROTO_DCCP))
                        nf_log_packet(net, pf, 0, skb, NULL, NULL, NULL,
                                      "nf_ct_dccp: invalid state transition ");
                return -NF_ACCEPT;
        }

        ct->proto.dccp.last_dir = dir;
        ct->proto.dccp.last_pkt = type;
        ct->proto.dccp.state = new_state;
        spin_unlock_bh(&ct->lock);

        if (new_state != old_state)
                nf_conntrack_event_cache(IPCT_PROTOINFO, ct);

        nf_ct_refresh_acct(ct, ctinfo, skb, timeouts[new_state]);

        return NF_ACCEPT;
}

static int dccp_error(struct net *net, struct nf_conn *tmpl,
                      struct sk_buff *skb, unsigned int dataoff,
                      enum ip_conntrack_info *ctinfo,
                      u_int8_t pf, unsigned int hooknum)
{
        struct dccp_hdr _dh, *dh;
        unsigned int dccp_len = skb->len - dataoff;
        unsigned int cscov;
        const char *msg;

        dh = skb_header_pointer(skb, dataoff, sizeof(_dh), &dh);
        if (dh == NULL) {
                msg = "nf_ct_dccp: short packet ";
                goto out_invalid;
        }

        if (dh->dccph_doff * 4 < sizeof(struct dccp_hdr) ||
            dh->dccph_doff * 4 > dccp_len) {
                msg = "nf_ct_dccp: truncated/malformed packet ";
                goto out_invalid;
        }

        cscov = dccp_len;
        if (dh->dccph_cscov) {
                cscov = (dh->dccph_cscov - 1) * 4;
                if (cscov > dccp_len) {
                        msg = "nf_ct_dccp: bad checksum coverage ";
                        goto out_invalid;
                }
        }

        if (net->ct.sysctl_checksum && hooknum == NF_INET_PRE_ROUTING &&
            nf_checksum_partial(skb, hooknum, dataoff, cscov, IPPROTO_DCCP,
                                pf)) {
                msg = "nf_ct_dccp: bad checksum ";
                goto out_invalid;
        }

        if (dh->dccph_type >= DCCP_PKT_INVALID) {
                msg = "nf_ct_dccp: reserved packet type ";
                goto out_invalid;
        }

        return NF_ACCEPT;

out_invalid:
        if (LOG_INVALID(net, IPPROTO_DCCP))
                nf_log_packet(net, pf, 0, skb, NULL, NULL, NULL, msg);
        return -NF_ACCEPT;
}

static int dccp_print_tuple(struct seq_file *s,
                            const struct nf_conntrack_tuple *tuple)
{
        return seq_printf(s, "sport=%hu dport=%hu ",
                          ntohs(tuple->src.u.dccp.port),
                          ntohs(tuple->dst.u.dccp.port));
}

static int dccp_print_conntrack(struct seq_file *s, struct nf_conn *ct)
{
        return seq_printf(s, "%s ", dccp_state_names[ct->proto.dccp.state]);
}

#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
static int dccp_to_nlattr(struct sk_buff *skb, struct nlattr *nla,
                          struct nf_conn *ct)
{
        struct nlattr *nest_parms;

        spin_lock_bh(&ct->lock);
        nest_parms = nla_nest_start(skb, CTA_PROTOINFO_DCCP | NLA_F_NESTED);
        if (!nest_parms)
                goto nla_put_failure;
        if (nla_put_u8(skb, CTA_PROTOINFO_DCCP_STATE, ct->proto.dccp.state) ||
            nla_put_u8(skb, CTA_PROTOINFO_DCCP_ROLE,
                       ct->proto.dccp.role[IP_CT_DIR_ORIGINAL]) ||
            nla_put_be64(skb, CTA_PROTOINFO_DCCP_HANDSHAKE_SEQ,
                         cpu_to_be64(ct->proto.dccp.handshake_seq)))
                goto nla_put_failure;
        nla_nest_end(skb, nest_parms);
        spin_unlock_bh(&ct->lock);
        return 0;

nla_put_failure:
        spin_unlock_bh(&ct->lock);
        return -1;
}

static const struct nla_policy dccp_nla_policy[CTA_PROTOINFO_DCCP_MAX + 1] = {
        [CTA_PROTOINFO_DCCP_STATE]      = { .type = NLA_U8 },
        [CTA_PROTOINFO_DCCP_ROLE]       = { .type = NLA_U8 },
        [CTA_PROTOINFO_DCCP_HANDSHAKE_SEQ] = { .type = NLA_U64 },
};

static int nlattr_to_dccp(struct nlattr *cda[], struct nf_conn *ct)
{
        struct nlattr *attr = cda[CTA_PROTOINFO_DCCP];
        struct nlattr *tb[CTA_PROTOINFO_DCCP_MAX + 1];
        int err;

        if (!attr)
                return 0;

        err = nla_parse_nested(tb, CTA_PROTOINFO_DCCP_MAX, attr,
                               dccp_nla_policy);
        if (err < 0)
                return err;

        if (!tb[CTA_PROTOINFO_DCCP_STATE] ||
            !tb[CTA_PROTOINFO_DCCP_ROLE] ||
            nla_get_u8(tb[CTA_PROTOINFO_DCCP_ROLE]) > CT_DCCP_ROLE_MAX ||
            nla_get_u8(tb[CTA_PROTOINFO_DCCP_STATE]) >= CT_DCCP_IGNORE) {
                return -EINVAL;
        }

        spin_lock_bh(&ct->lock);
        ct->proto.dccp.state = nla_get_u8(tb[CTA_PROTOINFO_DCCP_STATE]);
        if (nla_get_u8(tb[CTA_PROTOINFO_DCCP_ROLE]) == CT_DCCP_ROLE_CLIENT) {
                ct->proto.dccp.role[IP_CT_DIR_ORIGINAL] = CT_DCCP_ROLE_CLIENT;
                ct->proto.dccp.role[IP_CT_DIR_REPLY] = CT_DCCP_ROLE_SERVER;
        } else {
                ct->proto.dccp.role[IP_CT_DIR_ORIGINAL] = CT_DCCP_ROLE_SERVER;
                ct->proto.dccp.role[IP_CT_DIR_REPLY] = CT_DCCP_ROLE_CLIENT;
        }
        if (tb[CTA_PROTOINFO_DCCP_HANDSHAKE_SEQ]) {
                ct->proto.dccp.handshake_seq =
                be64_to_cpu(nla_get_be64(tb[CTA_PROTOINFO_DCCP_HANDSHAKE_SEQ]));
        }
        spin_unlock_bh(&ct->lock);
        return 0;
}

static int dccp_nlattr_size(void)
{
        return nla_total_size(0)        /* CTA_PROTOINFO_DCCP */
                + nla_policy_len(dccp_nla_policy, CTA_PROTOINFO_DCCP_MAX + 1);
}

#endif

#if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)

#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_cttimeout.h>

static int dccp_timeout_nlattr_to_obj(struct nlattr *tb[],
                                      struct net *net, void *data)
{
        struct dccp_net *dn = dccp_pernet(net);
        unsigned int *timeouts = data;
        int i;

        /* set default DCCP timeouts. */
        for (i=0; i<CT_DCCP_MAX; i++)
                timeouts[i] = dn->dccp_timeout[i];

        /* there's a 1:1 mapping between attributes and protocol states. */
        for (i=CTA_TIMEOUT_DCCP_UNSPEC+1; i<CTA_TIMEOUT_DCCP_MAX+1; i++) {
                if (tb[i]) {
                        timeouts[i] = ntohl(nla_get_be32(tb[i])) * HZ;
                }
        }
        return 0;
}

static int
dccp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
{
        const unsigned int *timeouts = data;
        int i;

        for (i=CTA_TIMEOUT_DCCP_UNSPEC+1; i<CTA_TIMEOUT_DCCP_MAX+1; i++) {
                if (nla_put_be32(skb, i, htonl(timeouts[i] / HZ)))
                        goto nla_put_failure;
        }
        return 0;

nla_put_failure:
        return -ENOSPC;
}

static const struct nla_policy
dccp_timeout_nla_policy[CTA_TIMEOUT_DCCP_MAX+1] = {
        [CTA_TIMEOUT_DCCP_REQUEST]      = { .type = NLA_U32 },
        [CTA_TIMEOUT_DCCP_RESPOND]      = { .type = NLA_U32 },
        [CTA_TIMEOUT_DCCP_PARTOPEN]     = { .type = NLA_U32 },
        [CTA_TIMEOUT_DCCP_OPEN]         = { .type = NLA_U32 },
        [CTA_TIMEOUT_DCCP_CLOSEREQ]     = { .type = NLA_U32 },
        [CTA_TIMEOUT_DCCP_CLOSING]      = { .type = NLA_U32 },
        [CTA_TIMEOUT_DCCP_TIMEWAIT]     = { .type = NLA_U32 },
};
#endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */

#ifdef CONFIG_SYSCTL
/* template, data assigned later */
static struct ctl_table dccp_sysctl_table[] = {
        {
                .procname       = "nf_conntrack_dccp_timeout_request",
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_jiffies,
        },
        {
                .procname       = "nf_conntrack_dccp_timeout_respond",
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_jiffies,
        },
        {
                .procname       = "nf_conntrack_dccp_timeout_partopen",
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_jiffies,
        },
        {
                .procname       = "nf_conntrack_dccp_timeout_open",
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_jiffies,
        },
        {
                .procname       = "nf_conntrack_dccp_timeout_closereq",
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_jiffies,
        },
        {
                .procname       = "nf_conntrack_dccp_timeout_closing",
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_jiffies,
        },
        {
                .procname       = "nf_conntrack_dccp_timeout_timewait",
                .maxlen         = sizeof(unsigned int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_jiffies,
        },
        {
                .procname       = "nf_conntrack_dccp_loose",
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec,
        },
        { }
};
#endif /* CONFIG_SYSCTL */

static int dccp_kmemdup_sysctl_table(struct net *net, struct nf_proto_net *pn,
                                     struct dccp_net *dn)
{
#ifdef CONFIG_SYSCTL
        if (pn->ctl_table)
                return 0;

        pn->ctl_table = kmemdup(dccp_sysctl_table,
                                sizeof(dccp_sysctl_table),
                                GFP_KERNEL);
        if (!pn->ctl_table)
                return -ENOMEM;

        pn->ctl_table[0].data = &dn->dccp_timeout[CT_DCCP_REQUEST];
        pn->ctl_table[1].data = &dn->dccp_timeout[CT_DCCP_RESPOND];
        pn->ctl_table[2].data = &dn->dccp_timeout[CT_DCCP_PARTOPEN];
        pn->ctl_table[3].data = &dn->dccp_timeout[CT_DCCP_OPEN];
        pn->ctl_table[4].data = &dn->dccp_timeout[CT_DCCP_CLOSEREQ];
        pn->ctl_table[5].data = &dn->dccp_timeout[CT_DCCP_CLOSING];
        pn->ctl_table[6].data = &dn->dccp_timeout[CT_DCCP_TIMEWAIT];
        pn->ctl_table[7].data = &dn->dccp_loose;

        /* Don't export sysctls to unprivileged users */
        if (net->user_ns != &init_user_ns)
                pn->ctl_table[0].procname = NULL;
#endif
        return 0;
}

static int dccp_init_net(struct net *net, u_int16_t proto)
{
        struct dccp_net *dn = dccp_pernet(net);
        struct nf_proto_net *pn = &dn->pn;

        if (!pn->users) {
                /* default values */
                dn->dccp_loose = 1;
                dn->dccp_timeout[CT_DCCP_REQUEST]       = 2 * DCCP_MSL;
                dn->dccp_timeout[CT_DCCP_RESPOND]       = 4 * DCCP_MSL;
                dn->dccp_timeout[CT_DCCP_PARTOPEN]      = 4 * DCCP_MSL;
                dn->dccp_timeout[CT_DCCP_OPEN]          = 12 * 3600 * HZ;
                dn->dccp_timeout[CT_DCCP_CLOSEREQ]      = 64 * HZ;
                dn->dccp_timeout[CT_DCCP_CLOSING]       = 64 * HZ;
                dn->dccp_timeout[CT_DCCP_TIMEWAIT]      = 2 * DCCP_MSL;
        }

        return dccp_kmemdup_sysctl_table(net, pn, dn);
}

static struct nf_conntrack_l4proto dccp_proto4 __read_mostly = {
        .l3proto                = AF_INET,
        .l4proto                = IPPROTO_DCCP,
        .name                   = "dccp",
        .pkt_to_tuple           = dccp_pkt_to_tuple,
        .invert_tuple           = dccp_invert_tuple,
        .new                    = dccp_new,
        .packet                 = dccp_packet,
        .get_timeouts           = dccp_get_timeouts,
        .error                  = dccp_error,
        .print_tuple            = dccp_print_tuple,
        .print_conntrack        = dccp_print_conntrack,
#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
        .to_nlattr              = dccp_to_nlattr,
        .nlattr_size            = dccp_nlattr_size,
        .from_nlattr            = nlattr_to_dccp,
        .tuple_to_nlattr        = nf_ct_port_tuple_to_nlattr,
        .nlattr_tuple_size      = nf_ct_port_nlattr_tuple_size,
        .nlattr_to_tuple        = nf_ct_port_nlattr_to_tuple,
        .nla_policy             = nf_ct_port_nla_policy,
#endif
#if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
        .ctnl_timeout           = {
                .nlattr_to_obj  = dccp_timeout_nlattr_to_obj,
                .obj_to_nlattr  = dccp_timeout_obj_to_nlattr,
                .nlattr_max     = CTA_TIMEOUT_DCCP_MAX,
                .obj_size       = sizeof(unsigned int) * CT_DCCP_MAX,
                .nla_policy     = dccp_timeout_nla_policy,
        },
#endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
        .net_id                 = &dccp_net_id,
        .init_net               = dccp_init_net,
};

static struct nf_conntrack_l4proto dccp_proto6 __read_mostly = {
        .l3proto                = AF_INET6,
        .l4proto                = IPPROTO_DCCP,
        .name                   = "dccp",
        .pkt_to_tuple           = dccp_pkt_to_tuple,
        .invert_tuple           = dccp_invert_tuple,
        .new                    = dccp_new,
        .packet                 = dccp_packet,
        .get_timeouts           = dccp_get_timeouts,
        .error                  = dccp_error,
        .print_tuple            = dccp_print_tuple,
        .print_conntrack        = dccp_print_conntrack,
#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
        .to_nlattr              = dccp_to_nlattr,
        .nlattr_size            = dccp_nlattr_size,
        .from_nlattr            = nlattr_to_dccp,
        .tuple_to_nlattr        = nf_ct_port_tuple_to_nlattr,
        .nlattr_tuple_size      = nf_ct_port_nlattr_tuple_size,
        .nlattr_to_tuple        = nf_ct_port_nlattr_to_tuple,
        .nla_policy             = nf_ct_port_nla_policy,
#endif
#if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
        .ctnl_timeout           = {
                .nlattr_to_obj  = dccp_timeout_nlattr_to_obj,
                .obj_to_nlattr  = dccp_timeout_obj_to_nlattr,
                .nlattr_max     = CTA_TIMEOUT_DCCP_MAX,
                .obj_size       = sizeof(unsigned int) * CT_DCCP_MAX,
                .nla_policy     = dccp_timeout_nla_policy,
        },
#endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
        .net_id                 = &dccp_net_id,
        .init_net               = dccp_init_net,
};

static __net_init int dccp_net_init(struct net *net)
{
        int ret = 0;
        ret = nf_ct_l4proto_pernet_register(net, &dccp_proto4);
        if (ret < 0) {
                pr_err("nf_conntrack_dccp4: pernet registration failed.\n");
                goto out;
        }
        ret = nf_ct_l4proto_pernet_register(net, &dccp_proto6);
        if (ret < 0) {
                pr_err("nf_conntrack_dccp6: pernet registration failed.\n");
                goto cleanup_dccp4;
        }
        return 0;
cleanup_dccp4:
        nf_ct_l4proto_pernet_unregister(net, &dccp_proto4);
out:
        return ret;
}

static __net_exit void dccp_net_exit(struct net *net)
{
        nf_ct_l4proto_pernet_unregister(net, &dccp_proto6);
        nf_ct_l4proto_pernet_unregister(net, &dccp_proto4);
}

static struct pernet_operations dccp_net_ops = {
        .init = dccp_net_init,
        .exit = dccp_net_exit,
        .id   = &dccp_net_id,
        .size = sizeof(struct dccp_net),
};

static int __init nf_conntrack_proto_dccp_init(void)
{
        int ret;

        ret = register_pernet_subsys(&dccp_net_ops);
        if (ret < 0)
                goto out_pernet;

        ret = nf_ct_l4proto_register(&dccp_proto4);
        if (ret < 0)
                goto out_dccp4;

        ret = nf_ct_l4proto_register(&dccp_proto6);
        if (ret < 0)
                goto out_dccp6;

        return 0;
out_dccp6:
        nf_ct_l4proto_unregister(&dccp_proto4);
out_dccp4:
        unregister_pernet_subsys(&dccp_net_ops);
out_pernet:
        return ret;
}

static void __exit nf_conntrack_proto_dccp_fini(void)
{
        nf_ct_l4proto_unregister(&dccp_proto6);
        nf_ct_l4proto_unregister(&dccp_proto4);
        unregister_pernet_subsys(&dccp_net_ops);
}

module_init(nf_conntrack_proto_dccp_init);
module_exit(nf_conntrack_proto_dccp_fini);

MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
MODULE_DESCRIPTION("DCCP connection tracking protocol helper");
MODULE_LICENSE("GPL");