net/dccp/dccp.h

   1 #ifndef _DCCP_H
   2 #define _DCCP_H
   3 /*
   4  *  net/dccp/dccp.h
   5  *
   6  *  An implementation of the DCCP protocol
   7  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   8  *  Copyright (c) 2005-6 Ian McDonald <ian.mcdonald@jandi.co.nz>
   9  *
  10  *      This program is free software; you can redistribute it and/or modify it
  11  *      under the terms of the GNU General Public License version 2 as
  12  *      published by the Free Software Foundation.
  13  */
  14
  15 #include <linux/dccp.h>
  16 #include <linux/ktime.h>
  17 #include <net/snmp.h>
  18 #include <net/sock.h>
  19 #include <net/tcp.h>
  20 #include "ackvec.h"
  21
  22 /*
  23  *      DCCP - specific warning and debugging macros.
  24  */
  25 #define DCCP_WARN(fmt, a...) LIMIT_NETDEBUG(KERN_WARNING "%s: " fmt,       \
  26                                                         __func__, ##a)
  27 #define DCCP_CRIT(fmt, a...) printk(KERN_CRIT fmt " at %s:%d/%s()\n", ##a, \
  28                                          __FILE__, __LINE__, __func__)
  29 #define DCCP_BUG(a...)       do { DCCP_CRIT("BUG: " a); dump_stack(); } while(0)
  30 #define DCCP_BUG_ON(cond)    do { if (unlikely((cond) != 0))               \
  31                                      DCCP_BUG("\"%s\" holds (exception!)", \
  32                                               __stringify(cond));          \
  33                              } while (0)
  34
  35 #define DCCP_PRINTK(enable, fmt, args...)       do { if (enable)             \
  36                                                         printk(fmt, ##args); \
  37                                                 } while(0)
  38 #define DCCP_PR_DEBUG(enable, fmt, a...)        DCCP_PRINTK(enable, KERN_DEBUG \
  39                                                   "%s: " fmt, __func__, ##a)
  40
  41 #ifdef CONFIG_IP_DCCP_DEBUG
  42 extern int dccp_debug;
  43 #define dccp_pr_debug(format, a...)       DCCP_PR_DEBUG(dccp_debug, format, ##a)
  44 #define dccp_pr_debug_cat(format, a...)   DCCP_PRINTK(dccp_debug, format, ##a)
  45 #define dccp_debug(fmt, a...)             dccp_pr_debug_cat(KERN_DEBUG fmt, ##a)
  46 #else
  47 #define dccp_pr_debug(format, a...)
  48 #define dccp_pr_debug_cat(format, a...)
  49 #define dccp_debug(format, a...)
  50 #endif
  51
  52 extern struct inet_hashinfo dccp_hashinfo;
  53
  54 extern struct percpu_counter dccp_orphan_count;
  55
  56 extern void dccp_time_wait(struct sock *sk, int state, int timeo);
  57
  58 /*
  59  *  Set safe upper bounds for header and option length. Since Data Offset is 8
  60  *  bits (RFC 4340, sec. 5.1), the total header length can never be more than
  61  *  4 * 255 = 1020 bytes. The largest possible header length is 28 bytes (X=1):
  62  *    - DCCP-Response with ACK Subheader and 4 bytes of Service code      OR
  63  *    - DCCP-Reset    with ACK Subheader and 4 bytes of Reset Code fields
  64  *  Hence a safe upper bound for the maximum option length is 1020-28 = 992
  65  */
  66 #define MAX_DCCP_SPECIFIC_HEADER (255 * sizeof(uint32_t))
  67 #define DCCP_MAX_PACKET_HDR 28
  68 #define DCCP_MAX_OPT_LEN (MAX_DCCP_SPECIFIC_HEADER - DCCP_MAX_PACKET_HDR)
  69 #define MAX_DCCP_HEADER (MAX_DCCP_SPECIFIC_HEADER + MAX_HEADER)
  70
  71 /* Upper bound for initial feature-negotiation overhead (padded to 32 bits) */
  72 #define DCCP_FEATNEG_OVERHEAD    (32 * sizeof(uint32_t))
  73
  74 #define DCCP_TIMEWAIT_LEN (60 * HZ) /* how long to wait to destroy TIME-WAIT
  75                                      * state, about 60 seconds */
  76
  77 /* RFC 1122, 4.2.3.1 initial RTO value */
  78 #define DCCP_TIMEOUT_INIT ((unsigned)(3 * HZ))
  79
  80 /*
  81  * The maximum back-off value for retransmissions. This is needed for
  82  *  - retransmitting client-Requests (sec. 8.1.1),
  83  *  - retransmitting Close/CloseReq when closing (sec. 8.3),
  84  *  - feature-negotiation retransmission (sec. 6.6.3),
  85  *  - Acks in client-PARTOPEN state (sec. 8.1.5).
  86  */
  87 #define DCCP_RTO_MAX ((unsigned)(64 * HZ))
  88
  89 /*
  90  * RTT sampling: sanity bounds and fallback RTT value from RFC 4340, section 3.4
  91  */
  92 #define DCCP_SANE_RTT_MIN       100
  93 #define DCCP_FALLBACK_RTT       (USEC_PER_SEC / 5)
  94 #define DCCP_SANE_RTT_MAX       (3 * USEC_PER_SEC)
  95
  96 /* Maximal interval between probes for local resources.  */
  97 #define DCCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ / 2U))
  98
  99 /* sysctl variables for DCCP */
 100 extern int  sysctl_dccp_request_retries;
 101 extern int  sysctl_dccp_retries1;
 102 extern int  sysctl_dccp_retries2;
 103 extern int  sysctl_dccp_tx_qlen;
 104 extern int  sysctl_dccp_sync_ratelimit;
 105
 106 /*
 107  *      48-bit sequence number arithmetic (signed and unsigned)
 108  */
 109 #define INT48_MIN         0x800000000000LL              /* 2^47     */
 110 #define UINT48_MAX        0xFFFFFFFFFFFFLL              /* 2^48 - 1 */
 111 #define COMPLEMENT48(x)  (0x1000000000000LL - (x))      /* 2^48 - x */
 112 #define TO_SIGNED48(x)   (((x) < INT48_MIN)? (x) : -COMPLEMENT48( (x)))
 113 #define TO_UNSIGNED48(x) (((x) >= 0)?        (x) :  COMPLEMENT48(-(x)))
 114 #define ADD48(a, b)      (((a) + (b)) & UINT48_MAX)
 115 #define SUB48(a, b)      ADD48((a), COMPLEMENT48(b))
 116
 117 static inline void dccp_set_seqno(u64 *seqno, u64 value)
 118 {
 119         *seqno = value & UINT48_MAX;
 120 }
 121
 122 static inline void dccp_inc_seqno(u64 *seqno)
 123 {
 124         *seqno = ADD48(*seqno, 1);
 125 }
 126
 127 /* signed mod-2^48 distance: pos. if seqno1 < seqno2, neg. if seqno1 > seqno2 */
 128 static inline s64 dccp_delta_seqno(const u64 seqno1, const u64 seqno2)
 129 {
 130         u64 delta = SUB48(seqno2, seqno1);
 131
 132         return TO_SIGNED48(delta);
 133 }
 134
 135 /* is seq1 < seq2 ? */
 136 static inline int before48(const u64 seq1, const u64 seq2)
 137 {
 138         return (s64)((seq2 << 16) - (seq1 << 16)) > 0;
 139 }
 140
 141 /* is seq1 > seq2 ? */
 142 #define after48(seq1, seq2)     before48(seq2, seq1)
 143
 144 /* is seq2 <= seq1 <= seq3 ? */
 145 static inline int between48(const u64 seq1, const u64 seq2, const u64 seq3)
 146 {
 147         return (seq3 << 16) - (seq2 << 16) >= (seq1 << 16) - (seq2 << 16);
 148 }
 149
 150 static inline u64 max48(const u64 seq1, const u64 seq2)
 151 {
 152         return after48(seq1, seq2) ? seq1 : seq2;
 153 }
 154
 155 /**
 156  * dccp_loss_count - Approximate the number of lost data packets in a burst loss
 157  * @s1:  last known sequence number before the loss ('hole')
 158  * @s2:  first sequence number seen after the 'hole'
 159  * @ndp: NDP count on packet with sequence number @s2
 160  */
 161 static inline u64 dccp_loss_count(const u64 s1, const u64 s2, const u64 ndp)
 162 {
 163         s64 delta = dccp_delta_seqno(s1, s2);
 164
 165         WARN_ON(delta < 0);
 166         delta -= ndp + 1;
 167
 168         return delta > 0 ? delta : 0;
 169 }
 170
 171 /**
 172  * dccp_loss_free - Evaluate condition for data loss from RFC 4340, 7.7.1
 173  */
 174 static inline bool dccp_loss_free(const u64 s1, const u64 s2, const u64 ndp)
 175 {
 176         return dccp_loss_count(s1, s2, ndp) == 0;
 177 }
 178
 179 enum {
 180         DCCP_MIB_NUM = 0,
 181         DCCP_MIB_ACTIVEOPENS,                   /* ActiveOpens */
 182         DCCP_MIB_ESTABRESETS,                   /* EstabResets */
 183         DCCP_MIB_CURRESTAB,                     /* CurrEstab */
 184         DCCP_MIB_OUTSEGS,                       /* OutSegs */
 185         DCCP_MIB_OUTRSTS,
 186         DCCP_MIB_ABORTONTIMEOUT,
 187         DCCP_MIB_TIMEOUTS,
 188         DCCP_MIB_ABORTFAILED,
 189         DCCP_MIB_PASSIVEOPENS,
 190         DCCP_MIB_ATTEMPTFAILS,
 191         DCCP_MIB_OUTDATAGRAMS,
 192         DCCP_MIB_INERRS,
 193         DCCP_MIB_OPTMANDATORYERROR,
 194         DCCP_MIB_INVALIDOPT,
 195         __DCCP_MIB_MAX
 196 };
 197
 198 #define DCCP_MIB_MAX    __DCCP_MIB_MAX
 199 struct dccp_mib {
 200         unsigned long   mibs[DCCP_MIB_MAX];
 201 };
 202
 203 DECLARE_SNMP_STAT(struct dccp_mib, dccp_statistics);
 204 #define DCCP_INC_STATS(field)       SNMP_INC_STATS(dccp_statistics, field)
 205 #define DCCP_INC_STATS_BH(field)    SNMP_INC_STATS_BH(dccp_statistics, field)
 206 #define DCCP_INC_STATS_USER(field)  SNMP_INC_STATS_USER(dccp_statistics, field)
 207 #define DCCP_DEC_STATS(field)       SNMP_DEC_STATS(dccp_statistics, field)
 208 #define DCCP_ADD_STATS_BH(field, val) \
 209                         SNMP_ADD_STATS_BH(dccp_statistics, field, val)
 210 #define DCCP_ADD_STATS_USER(field, val) \
 211                         SNMP_ADD_STATS_USER(dccp_statistics, field, val)
 212
 213 /*
 214  *      Checksumming routines
 215  */
 216 static inline unsigned int dccp_csum_coverage(const struct sk_buff *skb)
 217 {
 218         const struct dccp_hdr* dh = dccp_hdr(skb);
 219
 220         if (dh->dccph_cscov == 0)
 221                 return skb->len;
 222         return (dh->dccph_doff + dh->dccph_cscov - 1) * sizeof(u32);
 223 }
 224
 225 static inline void dccp_csum_outgoing(struct sk_buff *skb)
 226 {
 227         unsigned int cov = dccp_csum_coverage(skb);
 228
 229         if (cov >= skb->len)
 230                 dccp_hdr(skb)->dccph_cscov = 0;
 231
 232         skb->csum = skb_checksum(skb, 0, (cov > skb->len)? skb->len : cov, 0);
 233 }
 234
 235 extern void dccp_v4_send_check(struct sock *sk, struct sk_buff *skb);
 236
 237 extern int  dccp_retransmit_skb(struct sock *sk);
 238
 239 extern void dccp_send_ack(struct sock *sk);
 240 extern void dccp_reqsk_send_ack(struct sock *sk, struct sk_buff *skb,
 241                                 struct request_sock *rsk);
 242
 243 extern void dccp_send_sync(struct sock *sk, const u64 seq,
 244                            const enum dccp_pkt_type pkt_type);
 245
 246 /*
 247  * TX Packet Dequeueing Interface
 248  */
 249 extern void             dccp_qpolicy_push(struct sock *sk, struct sk_buff *skb);
 250 extern bool             dccp_qpolicy_full(struct sock *sk);
 251 extern void             dccp_qpolicy_drop(struct sock *sk, struct sk_buff *skb);
 252 extern struct sk_buff   *dccp_qpolicy_top(struct sock *sk);
 253 extern struct sk_buff   *dccp_qpolicy_pop(struct sock *sk);
 254 extern bool             dccp_qpolicy_param_ok(struct sock *sk, __be32 param);
 255
 256 /*
 257  * TX Packet Output and TX Timers
 258  */
 259 extern void   dccp_write_xmit(struct sock *sk);
 260 extern void   dccp_write_space(struct sock *sk);
 261 extern void   dccp_flush_write_queue(struct sock *sk, long *time_budget);
 262
 263 extern void dccp_init_xmit_timers(struct sock *sk);
 264 static inline void dccp_clear_xmit_timers(struct sock *sk)
 265 {
 266         inet_csk_clear_xmit_timers(sk);
 267 }
 268
 269 extern unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu);
 270
 271 extern const char *dccp_packet_name(const int type);
 272
 273 extern void dccp_set_state(struct sock *sk, const int state);
 274 extern void dccp_done(struct sock *sk);
 275
 276 extern int  dccp_reqsk_init(struct request_sock *rq, struct dccp_sock const *dp,
 277                             struct sk_buff const *skb);
 278
 279 extern int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
 280
 281 extern struct sock *dccp_create_openreq_child(struct sock *sk,
 282                                               const struct request_sock *req,
 283                                               const struct sk_buff *skb);
 284
 285 extern int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
 286
 287 extern struct sock *dccp_v4_request_recv_sock(struct sock *sk,
 288                                               struct sk_buff *skb,
 289                                               struct request_sock *req,
 290                                               struct dst_entry *dst);
 291 extern struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
 292                                    struct request_sock *req,
 293                                    struct request_sock **prev);
 294
 295 extern int dccp_child_process(struct sock *parent, struct sock *child,
 296                               struct sk_buff *skb);
 297 extern int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 298                                   struct dccp_hdr *dh, unsigned len);
 299 extern int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 300                                 const struct dccp_hdr *dh, const unsigned len);
 301
 302 extern int dccp_init_sock(struct sock *sk, const __u8 ctl_sock_initialized);
 303 extern void dccp_destroy_sock(struct sock *sk);
 304
 305 extern void             dccp_close(struct sock *sk, long timeout);
 306 extern struct sk_buff   *dccp_make_response(struct sock *sk,
 307                                             struct dst_entry *dst,
 308                                             struct request_sock *req);
 309
 310 extern int         dccp_connect(struct sock *sk);
 311 extern int         dccp_disconnect(struct sock *sk, int flags);
 312 extern int         dccp_getsockopt(struct sock *sk, int level, int optname,
 313                                    char __user *optval, int __user *optlen);
 314 extern int         dccp_setsockopt(struct sock *sk, int level, int optname,
 315                                    char __user *optval, unsigned int optlen);
 316 #ifdef CONFIG_COMPAT
 317 extern int         compat_dccp_getsockopt(struct sock *sk,
 318                                 int level, int optname,
 319                                 char __user *optval, int __user *optlen);
 320 extern int         compat_dccp_setsockopt(struct sock *sk,
 321                                 int level, int optname,
 322                                 char __user *optval, unsigned int optlen);
 323 #endif
 324 extern int         dccp_ioctl(struct sock *sk, int cmd, unsigned long arg);
 325 extern int         dccp_sendmsg(struct kiocb *iocb, struct sock *sk,
 326                                 struct msghdr *msg, size_t size);
 327 extern int         dccp_recvmsg(struct kiocb *iocb, struct sock *sk,
 328                                 struct msghdr *msg, size_t len, int nonblock,
 329                                 int flags, int *addr_len);
 330 extern void        dccp_shutdown(struct sock *sk, int how);
 331 extern int         inet_dccp_listen(struct socket *sock, int backlog);
 332 extern unsigned int dccp_poll(struct file *file, struct socket *sock,
 333                              poll_table *wait);
 334 extern int         dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr,
 335                                    int addr_len);
 336
 337 extern struct sk_buff *dccp_ctl_make_reset(struct sock *sk,
 338                                            struct sk_buff *skb);
 339 extern int         dccp_send_reset(struct sock *sk, enum dccp_reset_codes code);
 340 extern void        dccp_send_close(struct sock *sk, const int active);
 341 extern int         dccp_invalid_packet(struct sk_buff *skb);
 342 extern u32         dccp_sample_rtt(struct sock *sk, long delta);
 343
 344 static inline int dccp_bad_service_code(const struct sock *sk,
 345                                         const __be32 service)
 346 {
 347         const struct dccp_sock *dp = dccp_sk(sk);
 348
 349         if (dp->dccps_service == service)
 350                 return 0;
 351         return !dccp_list_has_service(dp->dccps_service_list, service);
 352 }
 353
 354 /**
 355  * dccp_skb_cb  -  DCCP per-packet control information
 356  * @dccpd_type: one of %dccp_pkt_type (or unknown)
 357  * @dccpd_ccval: CCVal field (5.1), see e.g. RFC 4342, 8.1
 358  * @dccpd_reset_code: one of %dccp_reset_codes
 359  * @dccpd_reset_data: Data1..3 fields (depend on @dccpd_reset_code)
 360  * @dccpd_opt_len: total length of all options (5.8) in the packet
 361  * @dccpd_seq: sequence number
 362  * @dccpd_ack_seq: acknowledgment number subheader field value
 363  * This is used for transmission as well as for reception.
 364  */
 365 struct dccp_skb_cb {
 366         union {
 367                 struct inet_skb_parm    h4;
 368 #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
 369                 struct inet6_skb_parm   h6;
 370 #endif
 371         } header;
 372         __u8  dccpd_type:4;
 373         __u8  dccpd_ccval:4;
 374         __u8  dccpd_reset_code,
 375               dccpd_reset_data[3];
 376         __u16 dccpd_opt_len;
 377         __u64 dccpd_seq;
 378         __u64 dccpd_ack_seq;
 379 };
 380
 381 #define DCCP_SKB_CB(__skb) ((struct dccp_skb_cb *)&((__skb)->cb[0]))
 382
 383 /* RFC 4340, sec. 7.7 */
 384 static inline int dccp_non_data_packet(const struct sk_buff *skb)
 385 {
 386         const __u8 type = DCCP_SKB_CB(skb)->dccpd_type;
 387
 388         return type == DCCP_PKT_ACK      ||
 389                type == DCCP_PKT_CLOSE    ||
 390                type == DCCP_PKT_CLOSEREQ ||
 391                type == DCCP_PKT_RESET    ||
 392                type == DCCP_PKT_SYNC     ||
 393                type == DCCP_PKT_SYNCACK;
 394 }
 395
 396 /* RFC 4340, sec. 7.7 */
 397 static inline int dccp_data_packet(const struct sk_buff *skb)
 398 {
 399         const __u8 type = DCCP_SKB_CB(skb)->dccpd_type;
 400
 401         return type == DCCP_PKT_DATA     ||
 402                type == DCCP_PKT_DATAACK  ||
 403                type == DCCP_PKT_REQUEST  ||
 404                type == DCCP_PKT_RESPONSE;
 405 }
 406
 407 static inline int dccp_packet_without_ack(const struct sk_buff *skb)
 408 {
 409         const __u8 type = DCCP_SKB_CB(skb)->dccpd_type;
 410
 411         return type == DCCP_PKT_DATA || type == DCCP_PKT_REQUEST;
 412 }
 413
 414 #define DCCP_PKT_WITHOUT_ACK_SEQ (UINT48_MAX << 2)
 415
 416 static inline void dccp_hdr_set_seq(struct dccp_hdr *dh, const u64 gss)
 417 {
 418         struct dccp_hdr_ext *dhx = (struct dccp_hdr_ext *)((void *)dh +
 419                                                            sizeof(*dh));
 420         dh->dccph_seq2 = 0;
 421         dh->dccph_seq = htons((gss >> 32) & 0xfffff);
 422         dhx->dccph_seq_low = htonl(gss & 0xffffffff);
 423 }
 424
 425 static inline void dccp_hdr_set_ack(struct dccp_hdr_ack_bits *dhack,
 426                                     const u64 gsr)
 427 {
 428         dhack->dccph_reserved1 = 0;
 429         dhack->dccph_ack_nr_high = htons(gsr >> 32);
 430         dhack->dccph_ack_nr_low  = htonl(gsr & 0xffffffff);
 431 }
 432
 433 static inline void dccp_update_gsr(struct sock *sk, u64 seq)
 434 {
 435         struct dccp_sock *dp = dccp_sk(sk);
 436
 437         dp->dccps_gsr = seq;
 438         /* Sequence validity window depends on remote Sequence Window (7.5.1) */
 439         dp->dccps_swl = SUB48(ADD48(dp->dccps_gsr, 1), dp->dccps_r_seq_win / 4);
 440         /*
 441          * Adjust SWL so that it is not below ISR. In contrast to RFC 4340,
 442          * 7.5.1 we perform this check beyond the initial handshake: W/W' are
 443          * always > 32, so for the first W/W' packets in the lifetime of a
 444          * connection we always have to adjust SWL.
 445          * A second reason why we are doing this is that the window depends on
 446          * the feature-remote value of Sequence Window: nothing stops the peer
 447          * from updating this value while we are busy adjusting SWL for the
 448          * first W packets (we would have to count from scratch again then).
 449          * Therefore it is safer to always make sure that the Sequence Window
 450          * is not artificially extended by a peer who grows SWL downwards by
 451          * continually updating the feature-remote Sequence-Window.
 452          * If sequence numbers wrap it is bad luck. But that will take a while
 453          * (48 bit), and this measure prevents Sequence-number attacks.
 454          */
 455         if (before48(dp->dccps_swl, dp->dccps_isr))
 456                 dp->dccps_swl = dp->dccps_isr;
 457         dp->dccps_swh = ADD48(dp->dccps_gsr, (3 * dp->dccps_r_seq_win) / 4);
 458 }
 459
 460 static inline void dccp_update_gss(struct sock *sk, u64 seq)
 461 {
 462         struct dccp_sock *dp = dccp_sk(sk);
 463
 464         dp->dccps_gss = seq;
 465         /* Ack validity window depends on local Sequence Window value (7.5.1) */
 466         dp->dccps_awl = SUB48(ADD48(dp->dccps_gss, 1), dp->dccps_l_seq_win);
 467         /* Adjust AWL so that it is not below ISS - see comment above for SWL */
 468         if (before48(dp->dccps_awl, dp->dccps_iss))
 469                 dp->dccps_awl = dp->dccps_iss;
 470         dp->dccps_awh = dp->dccps_gss;
 471 }
 472
 473 static inline int dccp_ackvec_pending(const struct sock *sk)
 474 {
 475         return dccp_sk(sk)->dccps_hc_rx_ackvec != NULL &&
 476                !dccp_ackvec_is_empty(dccp_sk(sk)->dccps_hc_rx_ackvec);
 477 }
 478
 479 static inline int dccp_ack_pending(const struct sock *sk)
 480 {
 481         return dccp_ackvec_pending(sk) || inet_csk_ack_scheduled(sk);
 482 }
 483
 484 extern int  dccp_feat_finalise_settings(struct dccp_sock *dp);
 485 extern int  dccp_feat_server_ccid_dependencies(struct dccp_request_sock *dreq);
 486 extern int  dccp_feat_insert_opts(struct dccp_sock*, struct dccp_request_sock*,
 487                                   struct sk_buff *skb);
 488 extern int  dccp_feat_activate_values(struct sock *sk, struct list_head *fn);
 489 extern void dccp_feat_list_purge(struct list_head *fn_list);
 490
 491 extern int dccp_insert_options(struct sock *sk, struct sk_buff *skb);
 492 extern int dccp_insert_options_rsk(struct dccp_request_sock*, struct sk_buff*);
 493 extern int dccp_insert_option_elapsed_time(struct sk_buff *skb, u32 elapsed);
 494 extern u32 dccp_timestamp(void);
 495 extern void dccp_timestamping_init(void);
 496 extern int dccp_insert_option(struct sk_buff *skb, unsigned char option,
 497                               const void *value, unsigned char len);
 498
 499 #ifdef CONFIG_SYSCTL
 500 extern int dccp_sysctl_init(void);
 501 extern void dccp_sysctl_exit(void);
 502 #else
 503 static inline int dccp_sysctl_init(void)
 504 {
 505         return 0;
 506 }
 507
 508 static inline void dccp_sysctl_exit(void)
 509 {
 510 }
 511 #endif
 512
 513 #endif /* _DCCP_H */