// SPDX-License-Identifier: GPL-2.0-only
/*
 *  net/dccp/proto.c
 *
 *  An implementation of the DCCP protocol
 *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
 */

#include <linux/dccp.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/in.h>
#include <linux/if_arp.h>
#include <linux/init.h>
#include <linux/random.h>
#include <linux/slab.h>
#include <net/checksum.h>

#include <net/inet_sock.h>
#include <net/inet_common.h>
#include <net/sock.h>
#include <net/xfrm.h>

#include <asm/ioctls.h>
#include <linux/spinlock.h>
#include <linux/timer.h>
#include <linux/delay.h>
#include <linux/poll.h>

#include "ccid.h"
#include "dccp.h"
#include "feat.h"

#define CREATE_TRACE_POINTS
#include "trace.h"

DEFINE_SNMP_STAT(struct dccp_mib, dccp_statistics) __read_mostly;

EXPORT_SYMBOL_GPL(dccp_statistics);

struct percpu_counter dccp_orphan_count;
EXPORT_SYMBOL_GPL(dccp_orphan_count);

struct inet_hashinfo dccp_hashinfo;
EXPORT_SYMBOL_GPL(dccp_hashinfo);

/* the maximum queue length for tx in packets. 0 is no limit */
int sysctl_dccp_tx_qlen __read_mostly = 5;

#ifdef CONFIG_IP_DCCP_DEBUG
static const char *dccp_state_name(const int state)
{
        static const char *const dccp_state_names[] = {
        [DCCP_OPEN]             = "OPEN",
        [DCCP_REQUESTING]       = "REQUESTING",
        [DCCP_PARTOPEN]         = "PARTOPEN",
        [DCCP_LISTEN]           = "LISTEN",
        [DCCP_RESPOND]          = "RESPOND",
        [DCCP_CLOSING]          = "CLOSING",
        [DCCP_ACTIVE_CLOSEREQ]  = "CLOSEREQ",
        [DCCP_PASSIVE_CLOSE]    = "PASSIVE_CLOSE",
        [DCCP_PASSIVE_CLOSEREQ] = "PASSIVE_CLOSEREQ",
        [DCCP_TIME_WAIT]        = "TIME_WAIT",
        [DCCP_CLOSED]           = "CLOSED",
        };

        if (state >= DCCP_MAX_STATES)
                return "INVALID STATE!";
        else
                return dccp_state_names[state];
}
#endif

void dccp_set_state(struct sock *sk, const int state)
{
        const int oldstate = sk->sk_state;

        dccp_pr_debug("%s(%p)  %s  -->  %s\n", dccp_role(sk), sk,
                      dccp_state_name(oldstate), dccp_state_name(state));
        WARN_ON(state == oldstate);

        switch (state) {
        case DCCP_OPEN:
                if (oldstate != DCCP_OPEN)
                        DCCP_INC_STATS(DCCP_MIB_CURRESTAB);
                /* Client retransmits all Confirm options until entering OPEN */
                if (oldstate == DCCP_PARTOPEN)
                        dccp_feat_list_purge(&dccp_sk(sk)->dccps_featneg);
                break;

        case DCCP_CLOSED:
                if (oldstate == DCCP_OPEN || oldstate == DCCP_ACTIVE_CLOSEREQ ||
                    oldstate == DCCP_CLOSING)
                        DCCP_INC_STATS(DCCP_MIB_ESTABRESETS);

                sk->sk_prot->unhash(sk);
                if (inet_csk(sk)->icsk_bind_hash != NULL &&
                    !(sk->sk_userlocks & SOCK_BINDPORT_LOCK))
                        inet_put_port(sk);
                /* fall through */
        default:
                if (oldstate == DCCP_OPEN)
                        DCCP_DEC_STATS(DCCP_MIB_CURRESTAB);
        }

        /* Change state AFTER socket is unhashed to avoid closed
         * socket sitting in hash tables.
         */
        inet_sk_set_state(sk, state);
}

EXPORT_SYMBOL_GPL(dccp_set_state);

static void dccp_finish_passive_close(struct sock *sk)
{
        switch (sk->sk_state) {
        case DCCP_PASSIVE_CLOSE:
                /* Node (client or server) has received Close packet. */
                dccp_send_reset(sk, DCCP_RESET_CODE_CLOSED);
                dccp_set_state(sk, DCCP_CLOSED);
                break;
        case DCCP_PASSIVE_CLOSEREQ:
                /*
                 * Client received CloseReq. We set the `active' flag so that
                 * dccp_send_close() retransmits the Close as per RFC 4340, 8.3.
                 */
                dccp_send_close(sk, 1);
                dccp_set_state(sk, DCCP_CLOSING);
        }
}

void dccp_done(struct sock *sk)
{
        dccp_set_state(sk, DCCP_CLOSED);
        dccp_clear_xmit_timers(sk);

        sk->sk_shutdown = SHUTDOWN_MASK;

        if (!sock_flag(sk, SOCK_DEAD))
                sk->sk_state_change(sk);
        else
                inet_csk_destroy_sock(sk);
}

EXPORT_SYMBOL_GPL(dccp_done);

const char *dccp_packet_name(const int type)
{
        static const char *const dccp_packet_names[] = {
                [DCCP_PKT_REQUEST]  = "REQUEST",
                [DCCP_PKT_RESPONSE] = "RESPONSE",
                [DCCP_PKT_DATA]     = "DATA",
                [DCCP_PKT_ACK]      = "ACK",
                [DCCP_PKT_DATAACK]  = "DATAACK",
                [DCCP_PKT_CLOSEREQ] = "CLOSEREQ",
                [DCCP_PKT_CLOSE]    = "CLOSE",
                [DCCP_PKT_RESET]    = "RESET",
                [DCCP_PKT_SYNC]     = "SYNC",
                [DCCP_PKT_SYNCACK]  = "SYNCACK",
        };

        if (type >= DCCP_NR_PKT_TYPES)
                return "INVALID";
        else
                return dccp_packet_names[type];
}

EXPORT_SYMBOL_GPL(dccp_packet_name);

static void dccp_sk_destruct(struct sock *sk)
{
        struct dccp_sock *dp = dccp_sk(sk);

        ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
        dp->dccps_hc_tx_ccid = NULL;
        inet_sock_destruct(sk);
}

int dccp_init_sock(struct sock *sk, const __u8 ctl_sock_initialized)
{
        struct dccp_sock *dp = dccp_sk(sk);
        struct inet_connection_sock *icsk = inet_csk(sk);

        icsk->icsk_rto          = DCCP_TIMEOUT_INIT;
        icsk->icsk_syn_retries  = sysctl_dccp_request_retries;
        sk->sk_state            = DCCP_CLOSED;
        sk->sk_write_space      = dccp_write_space;
        sk->sk_destruct         = dccp_sk_destruct;
        icsk->icsk_sync_mss     = dccp_sync_mss;
        dp->dccps_mss_cache     = 536;
        dp->dccps_rate_last     = jiffies;
        dp->dccps_role          = DCCP_ROLE_UNDEFINED;
        dp->dccps_service       = DCCP_SERVICE_CODE_IS_ABSENT;
        dp->dccps_tx_qlen       = sysctl_dccp_tx_qlen;

        dccp_init_xmit_timers(sk);

        INIT_LIST_HEAD(&dp->dccps_featneg);
        /* control socket doesn't need feat nego */
        if (likely(ctl_sock_initialized))
                return dccp_feat_init(sk);
        return 0;
}

EXPORT_SYMBOL_GPL(dccp_init_sock);

void dccp_destroy_sock(struct sock *sk)
{
        struct dccp_sock *dp = dccp_sk(sk);

        __skb_queue_purge(&sk->sk_write_queue);
        if (sk->sk_send_head != NULL) {
                kfree_skb(sk->sk_send_head);
                sk->sk_send_head = NULL;
        }

        /* Clean up a referenced DCCP bind bucket. */
        if (inet_csk(sk)->icsk_bind_hash != NULL)
                inet_put_port(sk);

        kfree(dp->dccps_service_list);
        dp->dccps_service_list = NULL;

        if (dp->dccps_hc_rx_ackvec != NULL) {
                dccp_ackvec_free(dp->dccps_hc_rx_ackvec);
                dp->dccps_hc_rx_ackvec = NULL;
        }
        ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk);
        dp->dccps_hc_rx_ccid = NULL;

        /* clean up feature negotiation state */
        dccp_feat_list_purge(&dp->dccps_featneg);
}

EXPORT_SYMBOL_GPL(dccp_destroy_sock);

static inline int dccp_listen_start(struct sock *sk, int backlog)
{
        struct dccp_sock *dp = dccp_sk(sk);

        dp->dccps_role = DCCP_ROLE_LISTEN;
        /* do not start to listen if feature negotiation setup fails */
        if (dccp_feat_finalise_settings(dp))
                return -EPROTO;
        return inet_csk_listen_start(sk, backlog);
}

static inline int dccp_need_reset(int state)
{
        return state != DCCP_CLOSED && state != DCCP_LISTEN &&
               state != DCCP_REQUESTING;
}

int dccp_disconnect(struct sock *sk, int flags)
{
        struct inet_connection_sock *icsk = inet_csk(sk);
        struct inet_sock *inet = inet_sk(sk);
        struct dccp_sock *dp = dccp_sk(sk);
        const int old_state = sk->sk_state;

        if (old_state != DCCP_CLOSED)
                dccp_set_state(sk, DCCP_CLOSED);

        /*
         * This corresponds to the ABORT function of RFC793, sec. 3.8
         * TCP uses a RST segment, DCCP a Reset packet with Code 2, "Aborted".
         */
        if (old_state == DCCP_LISTEN) {
                inet_csk_listen_stop(sk);
        } else if (dccp_need_reset(old_state)) {
                dccp_send_reset(sk, DCCP_RESET_CODE_ABORTED);
                sk->sk_err = ECONNRESET;
        } else if (old_state == DCCP_REQUESTING)
                sk->sk_err = ECONNRESET;

        dccp_clear_xmit_timers(sk);
        ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk);
        dp->dccps_hc_rx_ccid = NULL;

        __skb_queue_purge(&sk->sk_receive_queue);
        __skb_queue_purge(&sk->sk_write_queue);
        if (sk->sk_send_head != NULL) {
                __kfree_skb(sk->sk_send_head);
                sk->sk_send_head = NULL;
        }

        inet->inet_dport = 0;

        if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK))
                inet_reset_saddr(sk);

        sk->sk_shutdown = 0;
        sock_reset_flag(sk, SOCK_DONE);

        icsk->icsk_backoff = 0;
        inet_csk_delack_init(sk);
        __sk_dst_reset(sk);

        WARN_ON(inet->inet_num && !icsk->icsk_bind_hash);

        sk->sk_error_report(sk);
        return 0;
}

EXPORT_SYMBOL_GPL(dccp_disconnect);

/*
 *      Wait for a DCCP event.
 *
 *      Note that we don't need to lock the socket, as the upper poll layers
 *      take care of normal races (between the test and the event) and we don't
 *      go look at any of the socket buffers directly.
 */
__poll_t dccp_poll(struct file *file, struct socket *sock,
                       poll_table *wait)
{
        __poll_t mask;
        struct sock *sk = sock->sk;

        sock_poll_wait(file, sock, wait);
        if (sk->sk_state == DCCP_LISTEN)
                return inet_csk_listen_poll(sk);

        /* Socket is not locked. We are protected from async events
           by poll logic and correct handling of state changes
           made by another threads is impossible in any case.
         */

        mask = 0;
        if (sk->sk_err)
                mask = EPOLLERR;

        if (sk->sk_shutdown == SHUTDOWN_MASK || sk->sk_state == DCCP_CLOSED)
                mask |= EPOLLHUP;
        if (sk->sk_shutdown & RCV_SHUTDOWN)
                mask |= EPOLLIN | EPOLLRDNORM | EPOLLRDHUP;

        /* Connected? */
        if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_RESPOND)) {
                if (atomic_read(&sk->sk_rmem_alloc) > 0)
                        mask |= EPOLLIN | EPOLLRDNORM;

                if (!(sk->sk_shutdown & SEND_SHUTDOWN)) {
                        if (sk_stream_is_writeable(sk)) {
                                mask |= EPOLLOUT | EPOLLWRNORM;
                        } else {  /* send SIGIO later */
                                sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
                                set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);

                                /* Race breaker. If space is freed after
                                 * wspace test but before the flags are set,
                                 * IO signal will be lost.
                                 */
                                if (sk_stream_is_writeable(sk))
                                        mask |= EPOLLOUT | EPOLLWRNORM;
                        }
                }
        }
        return mask;
}

EXPORT_SYMBOL_GPL(dccp_poll);

int dccp_ioctl(struct sock *sk, int cmd, unsigned long arg)
{
        int rc = -ENOTCONN;

        lock_sock(sk);

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

        switch (cmd) {
        case SIOCINQ: {
                struct sk_buff *skb;
                unsigned long amount = 0;

                skb = skb_peek(&sk->sk_receive_queue);
                if (skb != NULL) {
                        /*
                         * We will only return the amount of this packet since
                         * that is all that will be read.
                         */
                        amount = skb->len;
                }
                rc = put_user(amount, (int __user *)arg);
        }
                break;
        default:
                rc = -ENOIOCTLCMD;
                break;
        }
out:
        release_sock(sk);
        return rc;
}

EXPORT_SYMBOL_GPL(dccp_ioctl);

static int dccp_setsockopt_service(struct sock *sk, const __be32 service,
                                   char __user *optval, unsigned int optlen)
{
        struct dccp_sock *dp = dccp_sk(sk);
        struct dccp_service_list *sl = NULL;

        if (service == DCCP_SERVICE_INVALID_VALUE ||
            optlen > DCCP_SERVICE_LIST_MAX_LEN * sizeof(u32))
                return -EINVAL;

        if (optlen > sizeof(service)) {
                sl = kmalloc(optlen, GFP_KERNEL);
                if (sl == NULL)
                        return -ENOMEM;

                sl->dccpsl_nr = optlen / sizeof(u32) - 1;
                if (copy_from_user(sl->dccpsl_list,
                                   optval + sizeof(service),
                                   optlen - sizeof(service)) ||
                    dccp_list_has_service(sl, DCCP_SERVICE_INVALID_VALUE)) {
                        kfree(sl);
                        return -EFAULT;
                }
        }

        lock_sock(sk);
        dp->dccps_service = service;

        kfree(dp->dccps_service_list);

        dp->dccps_service_list = sl;
        release_sock(sk);
        return 0;
}

static int dccp_setsockopt_cscov(struct sock *sk, int cscov, bool rx)
{
        u8 *list, len;
        int i, rc;

        if (cscov < 0 || cscov > 15)
                return -EINVAL;
        /*
         * Populate a list of permissible values, in the range cscov...15. This
         * is necessary since feature negotiation of single values only works if
         * both sides incidentally choose the same value. Since the list starts
         * lowest-value first, negotiation will pick the smallest shared value.
         */
        if (cscov == 0)
                return 0;
        len = 16 - cscov;

        list = kmalloc(len, GFP_KERNEL);
        if (list == NULL)
                return -ENOBUFS;

        for (i = 0; i < len; i++)
                list[i] = cscov++;

        rc = dccp_feat_register_sp(sk, DCCPF_MIN_CSUM_COVER, rx, list, len);

        if (rc == 0) {
                if (rx)
                        dccp_sk(sk)->dccps_pcrlen = cscov;
                else
                        dccp_sk(sk)->dccps_pcslen = cscov;
        }
        kfree(list);
        return rc;
}

static int dccp_setsockopt_ccid(struct sock *sk, int type,
                                char __user *optval, unsigned int optlen)
{
        u8 *val;
        int rc = 0;

        if (optlen < 1 || optlen > DCCP_FEAT_MAX_SP_VALS)
                return -EINVAL;

        val = memdup_user(optval, optlen);
        if (IS_ERR(val))
                return PTR_ERR(val);

        lock_sock(sk);
        if (type == DCCP_SOCKOPT_TX_CCID || type == DCCP_SOCKOPT_CCID)
                rc = dccp_feat_register_sp(sk, DCCPF_CCID, 1, val, optlen);

        if (!rc && (type == DCCP_SOCKOPT_RX_CCID || type == DCCP_SOCKOPT_CCID))
                rc = dccp_feat_register_sp(sk, DCCPF_CCID, 0, val, optlen);
        release_sock(sk);

        kfree(val);
        return rc;
}

static int do_dccp_setsockopt(struct sock *sk, int level, int optname,
                char __user *optval, unsigned int optlen)
{
        struct dccp_sock *dp = dccp_sk(sk);
        int val, err = 0;

        switch (optname) {
        case DCCP_SOCKOPT_PACKET_SIZE:
                DCCP_WARN("sockopt(PACKET_SIZE) is deprecated: fix your app\n");
                return 0;
        case DCCP_SOCKOPT_CHANGE_L:
        case DCCP_SOCKOPT_CHANGE_R:
                DCCP_WARN("sockopt(CHANGE_L/R) is deprecated: fix your app\n");
                return 0;
        case DCCP_SOCKOPT_CCID:
        case DCCP_SOCKOPT_RX_CCID:
        case DCCP_SOCKOPT_TX_CCID:
                return dccp_setsockopt_ccid(sk, optname, optval, optlen);
        }

        if (optlen < (int)sizeof(int))
                return -EINVAL;

        if (get_user(val, (int __user *)optval))
                return -EFAULT;

        if (optname == DCCP_SOCKOPT_SERVICE)
                return dccp_setsockopt_service(sk, val, optval, optlen);

        lock_sock(sk);
        switch (optname) {
        case DCCP_SOCKOPT_SERVER_TIMEWAIT:
                if (dp->dccps_role != DCCP_ROLE_SERVER)
                        err = -EOPNOTSUPP;
                else
                        dp->dccps_server_timewait = (val != 0);
                break;
        case DCCP_SOCKOPT_SEND_CSCOV:
                err = dccp_setsockopt_cscov(sk, val, false);
                break;
        case DCCP_SOCKOPT_RECV_CSCOV:
                err = dccp_setsockopt_cscov(sk, val, true);
                break;
        case DCCP_SOCKOPT_QPOLICY_ID:
                if (sk->sk_state != DCCP_CLOSED)
                        err = -EISCONN;
                else if (val < 0 || val >= DCCPQ_POLICY_MAX)
                        err = -EINVAL;
                else
                        dp->dccps_qpolicy = val;
                break;
        case DCCP_SOCKOPT_QPOLICY_TXQLEN:
                if (val < 0)
                        err = -EINVAL;
                else
                        dp->dccps_tx_qlen = val;
                break;
        default:
                err = -ENOPROTOOPT;
                break;
        }
        release_sock(sk);

        return err;
}

int dccp_setsockopt(struct sock *sk, int level, int optname,
                    char __user *optval, unsigned int optlen)
{
        if (level != SOL_DCCP)
                return inet_csk(sk)->icsk_af_ops->setsockopt(sk, level,
                                                             optname, optval,
                                                             optlen);
        return do_dccp_setsockopt(sk, level, optname, optval, optlen);
}

EXPORT_SYMBOL_GPL(dccp_setsockopt);

#ifdef CONFIG_COMPAT
int compat_dccp_setsockopt(struct sock *sk, int level, int optname,
                           char __user *optval, unsigned int optlen)
{
        if (level != SOL_DCCP)
                return inet_csk_compat_setsockopt(sk, level, optname,
                                                  optval, optlen);
        return do_dccp_setsockopt(sk, level, optname, optval, optlen);
}

EXPORT_SYMBOL_GPL(compat_dccp_setsockopt);
#endif

static int dccp_getsockopt_service(struct sock *sk, int len,
                                   __be32 __user *optval,
                                   int __user *optlen)
{
        const struct dccp_sock *dp = dccp_sk(sk);
        const struct dccp_service_list *sl;
        int err = -ENOENT, slen = 0, total_len = sizeof(u32);

        lock_sock(sk);
        if ((sl = dp->dccps_service_list) != NULL) {
                slen = sl->dccpsl_nr * sizeof(u32);
                total_len += slen;
        }

        err = -EINVAL;
        if (total_len > len)
                goto out;

        err = 0;
        if (put_user(total_len, optlen) ||
            put_user(dp->dccps_service, optval) ||
            (sl != NULL && copy_to_user(optval + 1, sl->dccpsl_list, slen)))
                err = -EFAULT;
out:
        release_sock(sk);
        return err;
}

static int do_dccp_getsockopt(struct sock *sk, int level, int optname,
                    char __user *optval, int __user *optlen)
{
        struct dccp_sock *dp;
        int val, len;

        if (get_user(len, optlen))
                return -EFAULT;

        if (len < (int)sizeof(int))
                return -EINVAL;

        dp = dccp_sk(sk);

        switch (optname) {
        case DCCP_SOCKOPT_PACKET_SIZE:
                DCCP_WARN("sockopt(PACKET_SIZE) is deprecated: fix your app\n");
                return 0;
        case DCCP_SOCKOPT_SERVICE:
                return dccp_getsockopt_service(sk, len,
                                               (__be32 __user *)optval, optlen);
        case DCCP_SOCKOPT_GET_CUR_MPS:
                val = dp->dccps_mss_cache;
                break;
        case DCCP_SOCKOPT_AVAILABLE_CCIDS:
                return ccid_getsockopt_builtin_ccids(sk, len, optval, optlen);
        case DCCP_SOCKOPT_TX_CCID:
                val = ccid_get_current_tx_ccid(dp);
                if (val < 0)
                        return -ENOPROTOOPT;
                break;
        case DCCP_SOCKOPT_RX_CCID:
                val = ccid_get_current_rx_ccid(dp);
                if (val < 0)
                        return -ENOPROTOOPT;
                break;
        case DCCP_SOCKOPT_SERVER_TIMEWAIT:
                val = dp->dccps_server_timewait;
                break;
        case DCCP_SOCKOPT_SEND_CSCOV:
                val = dp->dccps_pcslen;
                break;
        case DCCP_SOCKOPT_RECV_CSCOV:
                val = dp->dccps_pcrlen;
                break;
        case DCCP_SOCKOPT_QPOLICY_ID:
                val = dp->dccps_qpolicy;
                break;
        case DCCP_SOCKOPT_QPOLICY_TXQLEN:
                val = dp->dccps_tx_qlen;
                break;
        case 128 ... 191:
                return ccid_hc_rx_getsockopt(dp->dccps_hc_rx_ccid, sk, optname,
                                             len, (u32 __user *)optval, optlen);
        case 192 ... 255:
                return ccid_hc_tx_getsockopt(dp->dccps_hc_tx_ccid, sk, optname,
                                             len, (u32 __user *)optval, optlen);
        default:
                return -ENOPROTOOPT;
        }

        len = sizeof(val);
        if (put_user(len, optlen) || copy_to_user(optval, &val, len))
                return -EFAULT;

        return 0;
}

int dccp_getsockopt(struct sock *sk, int level, int optname,
                    char __user *optval, int __user *optlen)
{
        if (level != SOL_DCCP)
                return inet_csk(sk)->icsk_af_ops->getsockopt(sk, level,
                                                             optname, optval,
                                                             optlen);
        return do_dccp_getsockopt(sk, level, optname, optval, optlen);
}

EXPORT_SYMBOL_GPL(dccp_getsockopt);

#ifdef CONFIG_COMPAT
int compat_dccp_getsockopt(struct sock *sk, int level, int optname,
                           char __user *optval, int __user *optlen)
{
        if (level != SOL_DCCP)
                return inet_csk_compat_getsockopt(sk, level, optname,
                                                  optval, optlen);
        return do_dccp_getsockopt(sk, level, optname, optval, optlen);
}

EXPORT_SYMBOL_GPL(compat_dccp_getsockopt);
#endif

static int dccp_msghdr_parse(struct msghdr *msg, struct sk_buff *skb)
{
        struct cmsghdr *cmsg;

        /*
         * Assign an (opaque) qpolicy priority value to skb->priority.
         *
         * We are overloading this skb field for use with the qpolicy subystem.
         * The skb->priority is normally used for the SO_PRIORITY option, which
         * is initialised from sk_priority. Since the assignment of sk_priority
         * to skb->priority happens later (on layer 3), we overload this field
         * for use with queueing priorities as long as the skb is on layer 4.
         * The default priority value (if nothing is set) is 0.
         */
        skb->priority = 0;

        for_each_cmsghdr(cmsg, msg) {
                if (!CMSG_OK(msg, cmsg))
                        return -EINVAL;

                if (cmsg->cmsg_level != SOL_DCCP)
                        continue;

                if (cmsg->cmsg_type <= DCCP_SCM_QPOLICY_MAX &&
                    !dccp_qpolicy_param_ok(skb->sk, cmsg->cmsg_type))
                        return -EINVAL;

                switch (cmsg->cmsg_type) {
                case DCCP_SCM_PRIORITY:
                        if (cmsg->cmsg_len != CMSG_LEN(sizeof(__u32)))
                                return -EINVAL;
                        skb->priority = *(__u32 *)CMSG_DATA(cmsg);
                        break;
                default:
                        return -EINVAL;
                }
        }
        return 0;
}

int dccp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
{
        const struct dccp_sock *dp = dccp_sk(sk);
        const int flags = msg->msg_flags;
        const int noblock = flags & MSG_DONTWAIT;
        struct sk_buff *skb;
        int rc, size;
        long timeo;

        trace_dccp_probe(sk, len);

        if (len > dp->dccps_mss_cache)
                return -EMSGSIZE;

        lock_sock(sk);

        if (dccp_qpolicy_full(sk)) {
                rc = -EAGAIN;
                goto out_release;
        }

        timeo = sock_sndtimeo(sk, noblock);

        /*
         * We have to use sk_stream_wait_connect here to set sk_write_pending,
         * so that the trick in dccp_rcv_request_sent_state_process.
         */
        /* Wait for a connection to finish. */
        if ((1 << sk->sk_state) & ~(DCCPF_OPEN | DCCPF_PARTOPEN))
                if ((rc = sk_stream_wait_connect(sk, &timeo)) != 0)
                        goto out_release;

        size = sk->sk_prot->max_header + len;
        release_sock(sk);
        skb = sock_alloc_send_skb(sk, size, noblock, &rc);
        lock_sock(sk);
        if (skb == NULL)
                goto out_release;

        if (sk->sk_state == DCCP_CLOSED) {
                rc = -ENOTCONN;
                goto out_discard;
        }

        skb_reserve(skb, sk->sk_prot->max_header);
        rc = memcpy_from_msg(skb_put(skb, len), msg, len);
        if (rc != 0)
                goto out_discard;

        rc = dccp_msghdr_parse(msg, skb);
        if (rc != 0)
                goto out_discard;

        dccp_qpolicy_push(sk, skb);
        /*
         * The xmit_timer is set if the TX CCID is rate-based and will expire
         * when congestion control permits to release further packets into the
         * network. Window-based CCIDs do not use this timer.
         */
        if (!timer_pending(&dp->dccps_xmit_timer))
                dccp_write_xmit(sk);
out_release:
        release_sock(sk);
        return rc ? : len;
out_discard:
        kfree_skb(skb);
        goto out_release;
}

EXPORT_SYMBOL_GPL(dccp_sendmsg);

int dccp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
                 int flags, int *addr_len)
{
        const struct dccp_hdr *dh;
        long timeo;

        lock_sock(sk);

        if (sk->sk_state == DCCP_LISTEN) {
                len = -ENOTCONN;
                goto out;
        }

        timeo = sock_rcvtimeo(sk, nonblock);

        do {
                struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);

                if (skb == NULL)
                        goto verify_sock_status;

                dh = dccp_hdr(skb);

                switch (dh->dccph_type) {
                case DCCP_PKT_DATA:
                case DCCP_PKT_DATAACK:
                        goto found_ok_skb;

                case DCCP_PKT_CLOSE:
                case DCCP_PKT_CLOSEREQ:
                        if (!(flags & MSG_PEEK))
                                dccp_finish_passive_close(sk);
                        /* fall through */
                case DCCP_PKT_RESET:
                        dccp_pr_debug("found fin (%s) ok!\n",
                                      dccp_packet_name(dh->dccph_type));
                        len = 0;
                        goto found_fin_ok;
                default:
                        dccp_pr_debug("packet_type=%s\n",
                                      dccp_packet_name(dh->dccph_type));
                        sk_eat_skb(sk, skb);
                }
verify_sock_status:
                if (sock_flag(sk, SOCK_DONE)) {
                        len = 0;
                        break;
                }

                if (sk->sk_err) {
                        len = sock_error(sk);
                        break;
                }

                if (sk->sk_shutdown & RCV_SHUTDOWN) {
                        len = 0;
                        break;
                }

                if (sk->sk_state == DCCP_CLOSED) {
                        if (!sock_flag(sk, SOCK_DONE)) {
                                /* This occurs when user tries to read
                                 * from never connected socket.
                                 */
                                len = -ENOTCONN;
                                break;
                        }
                        len = 0;
                        break;
                }

                if (!timeo) {
                        len = -EAGAIN;
                        break;
                }

                if (signal_pending(current)) {
                        len = sock_intr_errno(timeo);
                        break;
                }

                sk_wait_data(sk, &timeo, NULL);
                continue;
        found_ok_skb:
                if (len > skb->len)
                        len = skb->len;
                else if (len < skb->len)
                        msg->msg_flags |= MSG_TRUNC;

                if (skb_copy_datagram_msg(skb, 0, msg, len)) {
                        /* Exception. Bailout! */
                        len = -EFAULT;
                        break;
                }
                if (flags & MSG_TRUNC)
                        len = skb->len;
        found_fin_ok:
                if (!(flags & MSG_PEEK))
                        sk_eat_skb(sk, skb);
                break;
        } while (1);
out:
        release_sock(sk);
        return len;
}

EXPORT_SYMBOL_GPL(dccp_recvmsg);

int inet_dccp_listen(struct socket *sock, int backlog)
{
        struct sock *sk = sock->sk;
        unsigned char old_state;
        int err;

        lock_sock(sk);

        err = -EINVAL;
        if (sock->state != SS_UNCONNECTED || sock->type != SOCK_DCCP)
                goto out;

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

        sk->sk_max_ack_backlog = backlog;
        /* Really, if the socket is already in listen state
         * we can only allow the backlog to be adjusted.
         */
        if (old_state != DCCP_LISTEN) {
                /*
                 * FIXME: here it probably should be sk->sk_prot->listen_start
                 * see tcp_listen_start
                 */
                err = dccp_listen_start(sk, backlog);
                if (err)
                        goto out;
        }
        err = 0;

out:
        release_sock(sk);
        return err;
}

EXPORT_SYMBOL_GPL(inet_dccp_listen);

static void dccp_terminate_connection(struct sock *sk)
{
        u8 next_state = DCCP_CLOSED;

        switch (sk->sk_state) {
        case DCCP_PASSIVE_CLOSE:
        case DCCP_PASSIVE_CLOSEREQ:
                dccp_finish_passive_close(sk);
                break;
        case DCCP_PARTOPEN:
                dccp_pr_debug("Stop PARTOPEN timer (%p)\n", sk);
                inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
                /* fall through */
        case DCCP_OPEN:
                dccp_send_close(sk, 1);

                if (dccp_sk(sk)->dccps_role == DCCP_ROLE_SERVER &&
                    !dccp_sk(sk)->dccps_server_timewait)
                        next_state = DCCP_ACTIVE_CLOSEREQ;
                else
                        next_state = DCCP_CLOSING;
                /* fall through */
        default:
                dccp_set_state(sk, next_state);
        }
}

void dccp_close(struct sock *sk, long timeout)
{
        struct dccp_sock *dp = dccp_sk(sk);
        struct sk_buff *skb;
        u32 data_was_unread = 0;

        int state;

        lock_sock(sk);

        sk->sk_shutdown = SHUTDOWN_MASK;

        if (sk->sk_state == DCCP_LISTEN) {
                dccp_set_state(sk, DCCP_CLOSED);

                /* Special case. */
                inet_csk_listen_stop(sk);

                goto adjudge_to_death;
        }

        sk_stop_timer(sk, &dp->dccps_xmit_timer);

        /*
         * We need to flush the recv. buffs.  We do this only on the
         * descriptor close, not protocol-sourced closes, because the
          *reader process may not have drained the data yet!
         */
        while ((skb = __skb_dequeue(&sk->sk_receive_queue)) != NULL) {
                data_was_unread += skb->len;
                __kfree_skb(skb);
        }

        /* If socket has been already reset kill it. */
        if (sk->sk_state == DCCP_CLOSED)
                goto adjudge_to_death;

        if (data_was_unread) {
                /* Unread data was tossed, send an appropriate Reset Code */
                DCCP_WARN("ABORT with %u bytes unread\n", data_was_unread);
                dccp_send_reset(sk, DCCP_RESET_CODE_ABORTED);
                dccp_set_state(sk, DCCP_CLOSED);
        } else if (sock_flag(sk, SOCK_LINGER) && !sk->sk_lingertime) {
                /* Check zero linger _after_ checking for unread data. */
                sk->sk_prot->disconnect(sk, 0);
        } else if (sk->sk_state != DCCP_CLOSED) {
                /*
                 * Normal connection termination. May need to wait if there are
                 * still packets in the TX queue that are delayed by the CCID.
                 */
                dccp_flush_write_queue(sk, &timeout);
                dccp_terminate_connection(sk);
        }

        /*
         * Flush write queue. This may be necessary in several cases:
         * - we have been closed by the peer but still have application data;
         * - abortive termination (unread data or zero linger time),
         * - normal termination but queue could not be flushed within time limit
         */
        __skb_queue_purge(&sk->sk_write_queue);

        sk_stream_wait_close(sk, timeout);

adjudge_to_death:
        state = sk->sk_state;
        sock_hold(sk);
        sock_orphan(sk);

        /*
         * It is the last release_sock in its life. It will remove backlog.
         */
        release_sock(sk);
        /*
         * Now socket is owned by kernel and we acquire BH lock
         * to finish close. No need to check for user refs.
         */
        local_bh_disable();
        bh_lock_sock(sk);
        WARN_ON(sock_owned_by_user(sk));

        percpu_counter_inc(sk->sk_prot->orphan_count);

        /* Have we already been destroyed by a softirq or backlog? */
        if (state != DCCP_CLOSED && sk->sk_state == DCCP_CLOSED)
                goto out;

        if (sk->sk_state == DCCP_CLOSED)
                inet_csk_destroy_sock(sk);

        /* Otherwise, socket is reprieved until protocol close. */

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

EXPORT_SYMBOL_GPL(dccp_close);

void dccp_shutdown(struct sock *sk, int how)
{
        dccp_pr_debug("called shutdown(%x)\n", how);
}

EXPORT_SYMBOL_GPL(dccp_shutdown);

static inline int __init dccp_mib_init(void)
{
        dccp_statistics = alloc_percpu(struct dccp_mib);
        if (!dccp_statistics)
                return -ENOMEM;
        return 0;
}

static inline void dccp_mib_exit(void)
{
        free_percpu(dccp_statistics);
}

static int thash_entries;
module_param(thash_entries, int, 0444);
MODULE_PARM_DESC(thash_entries, "Number of ehash buckets");

#ifdef CONFIG_IP_DCCP_DEBUG
bool dccp_debug;
module_param(dccp_debug, bool, 0644);
MODULE_PARM_DESC(dccp_debug, "Enable debug messages");

EXPORT_SYMBOL_GPL(dccp_debug);
#endif

static int __init dccp_init(void)
{
        unsigned long goal;
        unsigned long nr_pages = totalram_pages();
        int ehash_order, bhash_order, i;
        int rc;

        BUILD_BUG_ON(sizeof(struct dccp_skb_cb) >
                     FIELD_SIZEOF(struct sk_buff, cb));
        rc = percpu_counter_init(&dccp_orphan_count, 0, GFP_KERNEL);
        if (rc)
                goto out_fail;
        inet_hashinfo_init(&dccp_hashinfo);
        rc = inet_hashinfo2_init_mod(&dccp_hashinfo);
        if (rc)
                goto out_fail;
        rc = -ENOBUFS;
        dccp_hashinfo.bind_bucket_cachep =
                kmem_cache_create("dccp_bind_bucket",
                                  sizeof(struct inet_bind_bucket), 0,
                                  SLAB_HWCACHE_ALIGN, NULL);
        if (!dccp_hashinfo.bind_bucket_cachep)
                goto out_free_percpu;

        /*
         * Size and allocate the main established and bind bucket
         * hash tables.
         *
         * The methodology is similar to that of the buffer cache.
         */
        if (nr_pages >= (128 * 1024))
                goal = nr_pages >> (21 - PAGE_SHIFT);
        else
                goal = nr_pages >> (23 - PAGE_SHIFT);

        if (thash_entries)
                goal = (thash_entries *
                        sizeof(struct inet_ehash_bucket)) >> PAGE_SHIFT;
        for (ehash_order = 0; (1UL << ehash_order) < goal; ehash_order++)
                ;
        do {
                unsigned long hash_size = (1UL << ehash_order) * PAGE_SIZE /
                                        sizeof(struct inet_ehash_bucket);

                while (hash_size & (hash_size - 1))
                        hash_size--;
                dccp_hashinfo.ehash_mask = hash_size - 1;
                dccp_hashinfo.ehash = (struct inet_ehash_bucket *)
                        __get_free_pages(GFP_ATOMIC|__GFP_NOWARN, ehash_order);
        } while (!dccp_hashinfo.ehash && --ehash_order > 0);

        if (!dccp_hashinfo.ehash) {
                DCCP_CRIT("Failed to allocate DCCP established hash table");
                goto out_free_bind_bucket_cachep;
        }

        for (i = 0; i <= dccp_hashinfo.ehash_mask; i++)
                INIT_HLIST_NULLS_HEAD(&dccp_hashinfo.ehash[i].chain, i);

        if (inet_ehash_locks_alloc(&dccp_hashinfo))
                        goto out_free_dccp_ehash;

        bhash_order = ehash_order;

        do {
                dccp_hashinfo.bhash_size = (1UL << bhash_order) * PAGE_SIZE /
                                        sizeof(struct inet_bind_hashbucket);
                if ((dccp_hashinfo.bhash_size > (64 * 1024)) &&
                    bhash_order > 0)
                        continue;
                dccp_hashinfo.bhash = (struct inet_bind_hashbucket *)
                        __get_free_pages(GFP_ATOMIC|__GFP_NOWARN, bhash_order);
        } while (!dccp_hashinfo.bhash && --bhash_order >= 0);

        if (!dccp_hashinfo.bhash) {
                DCCP_CRIT("Failed to allocate DCCP bind hash table");
                goto out_free_dccp_locks;
        }

        for (i = 0; i < dccp_hashinfo.bhash_size; i++) {
                spin_lock_init(&dccp_hashinfo.bhash[i].lock);
                INIT_HLIST_HEAD(&dccp_hashinfo.bhash[i].chain);
        }

        rc = dccp_mib_init();
        if (rc)
                goto out_free_dccp_bhash;

        rc = dccp_ackvec_init();
        if (rc)
                goto out_free_dccp_mib;

        rc = dccp_sysctl_init();
        if (rc)
                goto out_ackvec_exit;

        rc = ccid_initialize_builtins();
        if (rc)
                goto out_sysctl_exit;

        dccp_timestamping_init();

        return 0;

out_sysctl_exit:
        dccp_sysctl_exit();
out_ackvec_exit:
        dccp_ackvec_exit();
out_free_dccp_mib:
        dccp_mib_exit();
out_free_dccp_bhash:
        free_pages((unsigned long)dccp_hashinfo.bhash, bhash_order);
out_free_dccp_locks:
        inet_ehash_locks_free(&dccp_hashinfo);
out_free_dccp_ehash:
        free_pages((unsigned long)dccp_hashinfo.ehash, ehash_order);
out_free_bind_bucket_cachep:
        kmem_cache_destroy(dccp_hashinfo.bind_bucket_cachep);
out_free_percpu:
        percpu_counter_destroy(&dccp_orphan_count);
out_fail:
        dccp_hashinfo.bhash = NULL;
        dccp_hashinfo.ehash = NULL;
        dccp_hashinfo.bind_bucket_cachep = NULL;
        return rc;
}

static void __exit dccp_fini(void)
{
        ccid_cleanup_builtins();
        dccp_mib_exit();
        free_pages((unsigned long)dccp_hashinfo.bhash,
                   get_order(dccp_hashinfo.bhash_size *
                             sizeof(struct inet_bind_hashbucket)));
        free_pages((unsigned long)dccp_hashinfo.ehash,
                   get_order((dccp_hashinfo.ehash_mask + 1) *
                             sizeof(struct inet_ehash_bucket)));
        inet_ehash_locks_free(&dccp_hashinfo);
        kmem_cache_destroy(dccp_hashinfo.bind_bucket_cachep);
        dccp_ackvec_exit();
        dccp_sysctl_exit();
        percpu_counter_destroy(&dccp_orphan_count);
}

module_init(dccp_init);
module_exit(dccp_fini);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@conectiva.com.br>");
MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");