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#ifndef _DCCP_H
#define _DCCP_H
* net/dccp/dccp.h
* An implementation of the DCCP protocol
* Copyright (c) 2005 Arnaldo Carvalho de Melo <>
* Copyright (c) 2005-6 Ian McDonald <>
* 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/dccp.h>
#include <linux/ktime.h>
#include <net/snmp.h>
#include <net/sock.h>
#include <net/tcp.h>
#include "ackvec.h"
* DCCP - specific warning and debugging macros.
#define DCCP_WARN(fmt, a...) LIMIT_NETDEBUG(KERN_WARNING "%s: " fmt, \
__func__, ##a)
#define DCCP_CRIT(fmt, a...) printk(KERN_CRIT fmt " at %s:%d/%s()\n", ##a, \
__FILE__, __LINE__, __func__)
#define DCCP_BUG(a...) do { DCCP_CRIT("BUG: " a); dump_stack(); } while(0)
#define DCCP_BUG_ON(cond) do { if (unlikely((cond) != 0)) \
DCCP_BUG("\"%s\" holds (exception!)", \
__stringify(cond)); \
} while (0)
#define DCCP_PRINTK(enable, fmt, args...) do { if (enable) \
printk(fmt, ##args); \
} while(0)
#define DCCP_PR_DEBUG(enable, fmt, a...) DCCP_PRINTK(enable, KERN_DEBUG \
"%s: " fmt, __func__, ##a)
extern int dccp_debug;
#define dccp_pr_debug(format, a...) DCCP_PR_DEBUG(dccp_debug, format, ##a)
#define dccp_pr_debug_cat(format, a...) DCCP_PRINTK(dccp_debug, format, ##a)
#define dccp_debug(fmt, a...) dccp_pr_debug_cat(KERN_DEBUG fmt, ##a)
#define dccp_pr_debug(format, a...)
#define dccp_pr_debug_cat(format, a...)
#define dccp_debug(format, a...)
extern struct inet_hashinfo dccp_hashinfo;
extern struct percpu_counter dccp_orphan_count;
extern void dccp_time_wait(struct sock *sk, int state, int timeo);
* Set safe upper bounds for header and option length. Since Data Offset is 8
* bits (RFC 4340, sec. 5.1), the total header length can never be more than
* 4 * 255 = 1020 bytes. The largest possible header length is 28 bytes (X=1):
* - DCCP-Response with ACK Subheader and 4 bytes of Service code OR
* - DCCP-Reset with ACK Subheader and 4 bytes of Reset Code fields
* Hence a safe upper bound for the maximum option length is 1020-28 = 992
#define MAX_DCCP_SPECIFIC_HEADER (255 * sizeof(uint32_t))
/* Upper bound for initial feature-negotiation overhead (padded to 32 bits) */
#define DCCP_FEATNEG_OVERHEAD (32 * sizeof(uint32_t))
#define DCCP_TIMEWAIT_LEN (60 * HZ) /* how long to wait to destroy TIME-WAIT
* state, about 60 seconds */
/* RFC 1122, initial RTO value */
#define DCCP_TIMEOUT_INIT ((unsigned)(3 * HZ))
* The maximum back-off value for retransmissions. This is needed for
* - retransmitting client-Requests (sec. 8.1.1),
* - retransmitting Close/CloseReq when closing (sec. 8.3),
* - feature-negotiation retransmission (sec. 6.6.3),
* - Acks in client-PARTOPEN state (sec. 8.1.5).
#define DCCP_RTO_MAX ((unsigned)(64 * HZ))
* RTT sampling: sanity bounds and fallback RTT value from RFC 4340, section 3.4
#define DCCP_SANE_RTT_MIN 100
/* sysctl variables for DCCP */
extern int sysctl_dccp_request_retries;
extern int sysctl_dccp_retries1;
extern int sysctl_dccp_retries2;
extern int sysctl_dccp_tx_qlen;
extern int sysctl_dccp_sync_ratelimit;
* 48-bit sequence number arithmetic (signed and unsigned)
#define INT48_MIN 0x800000000000LL /* 2^47 */
#define UINT48_MAX 0xFFFFFFFFFFFFLL /* 2^48 - 1 */
#define COMPLEMENT48(x) (0x1000000000000LL - (x)) /* 2^48 - x */
#define TO_SIGNED48(x) (((x) < INT48_MIN)? (x) : -COMPLEMENT48( (x)))
#define TO_UNSIGNED48(x) (((x) >= 0)? (x) : COMPLEMENT48(-(x)))
#define ADD48(a, b) (((a) + (b)) & UINT48_MAX)
#define SUB48(a, b) ADD48((a), COMPLEMENT48(b))
static inline void dccp_set_seqno(u64 *seqno, u64 value)
*seqno = value & UINT48_MAX;
static inline void dccp_inc_seqno(u64 *seqno)
*seqno = ADD48(*seqno, 1);
/* signed mod-2^48 distance: pos. if seqno1 < seqno2, neg. if seqno1 > seqno2 */
static inline s64 dccp_delta_seqno(const u64 seqno1, const u64 seqno2)
u64 delta = SUB48(seqno2, seqno1);
return TO_SIGNED48(delta);
/* is seq1 < seq2 ? */
static inline int before48(const u64 seq1, const u64 seq2)
return (s64)((seq2 << 16) - (seq1 << 16)) > 0;
/* is seq1 > seq2 ? */
#define after48(seq1, seq2) before48(seq2, seq1)
/* is seq2 <= seq1 <= seq3 ? */
static inline int between48(const u64 seq1, const u64 seq2, const u64 seq3)
return (seq3 << 16) - (seq2 << 16) >= (seq1 << 16) - (seq2 << 16);
static inline u64 max48(const u64 seq1, const u64 seq2)
return after48(seq1, seq2) ? seq1 : seq2;
* dccp_loss_count - Approximate the number of lost data packets in a burst loss
* @s1: last known sequence number before the loss ('hole')
* @s2: first sequence number seen after the 'hole'
* @ndp: NDP count on packet with sequence number @s2
static inline u64 dccp_loss_count(const u64 s1, const u64 s2, const u64 ndp)
s64 delta = dccp_delta_seqno(s1, s2);
WARN_ON(delta < 0);
delta -= ndp + 1;
return delta > 0 ? delta : 0;
* dccp_loss_free - Evaluate condition for data loss from RFC 4340, 7.7.1
static inline bool dccp_loss_free(const u64 s1, const u64 s2, const u64 ndp)
return dccp_loss_count(s1, s2, ndp) == 0;
enum {
struct dccp_mib {
unsigned long mibs[DCCP_MIB_MAX];
DECLARE_SNMP_STAT(struct dccp_mib, dccp_statistics);
#define DCCP_INC_STATS(field) SNMP_INC_STATS(dccp_statistics, field)
#define DCCP_INC_STATS_BH(field) SNMP_INC_STATS_BH(dccp_statistics, field)
#define DCCP_DEC_STATS(field) SNMP_DEC_STATS(dccp_statistics, field)
* Checksumming routines
static inline unsigned int dccp_csum_coverage(const struct sk_buff *skb)
const struct dccp_hdr* dh = dccp_hdr(skb);
if (dh->dccph_cscov == 0)
return skb->len;
return (dh->dccph_doff + dh->dccph_cscov - 1) * sizeof(u32);
static inline void dccp_csum_outgoing(struct sk_buff *skb)
unsigned int cov = dccp_csum_coverage(skb);
if (cov >= skb->len)
dccp_hdr(skb)->dccph_cscov = 0;
skb->csum = skb_checksum(skb, 0, (cov > skb->len)? skb->len : cov, 0);
extern void dccp_v4_send_check(struct sock *sk, struct sk_buff *skb);
extern int dccp_retransmit_skb(struct sock *sk);
extern void dccp_send_ack(struct sock *sk);
extern void dccp_reqsk_send_ack(struct sock *sk, struct sk_buff *skb,
struct request_sock *rsk);
extern void dccp_send_sync(struct sock *sk, const u64 seq,
const enum dccp_pkt_type pkt_type);
* TX Packet Dequeueing Interface
extern void dccp_qpolicy_push(struct sock *sk, struct sk_buff *skb);
extern bool dccp_qpolicy_full(struct sock *sk);
extern void dccp_qpolicy_drop(struct sock *sk, struct sk_buff *skb);
extern struct sk_buff *dccp_qpolicy_top(struct sock *sk);
extern struct sk_buff *dccp_qpolicy_pop(struct sock *sk);
extern bool dccp_qpolicy_param_ok(struct sock *sk, __be32 param);
* TX Packet Output and TX Timers
extern void dccp_write_xmit(struct sock *sk);
extern void dccp_write_space(struct sock *sk);
extern void dccp_flush_write_queue(struct sock *sk, long *time_budget);
extern void dccp_init_xmit_timers(struct sock *sk);
static inline void dccp_clear_xmit_timers(struct sock *sk)
extern unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu);
extern const char *dccp_packet_name(const int type);
extern void dccp_set_state(struct sock *sk, const int state);
extern void dccp_done(struct sock *sk);
extern int dccp_reqsk_init(struct request_sock *rq, struct dccp_sock const *dp,
struct sk_buff const *skb);
extern int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
extern struct sock *dccp_create_openreq_child(struct sock *sk,
const struct request_sock *req,
const struct sk_buff *skb);
extern int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
extern struct sock *dccp_v4_request_recv_sock(struct sock *sk,
struct sk_buff *skb,
struct request_sock *req,
struct dst_entry *dst);
extern struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
struct request_sock *req,
struct request_sock **prev);
extern int dccp_child_process(struct sock *parent, struct sock *child,
struct sk_buff *skb);
extern int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
struct dccp_hdr *dh, unsigned len);
extern int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
const struct dccp_hdr *dh, const unsigned len);
extern int dccp_init_sock(struct sock *sk, const __u8 ctl_sock_initialized);
extern void dccp_destroy_sock(struct sock *sk);
extern void dccp_close(struct sock *sk, long timeout);
extern struct sk_buff *dccp_make_response(struct sock *sk,
struct dst_entry *dst,
struct request_sock *req);
extern int dccp_connect(struct sock *sk);
extern int dccp_disconnect(struct sock *sk, int flags);
extern int dccp_getsockopt(struct sock *sk, int level, int optname,
char __user *optval, int __user *optlen);
extern int dccp_setsockopt(struct sock *sk, int level, int optname,
char __user *optval, unsigned int optlen);
extern int compat_dccp_getsockopt(struct sock *sk,
int level, int optname,
char __user *optval, int __user *optlen);
extern int compat_dccp_setsockopt(struct sock *sk,
int level, int optname,
char __user *optval, unsigned int optlen);
extern int dccp_ioctl(struct sock *sk, int cmd, unsigned long arg);
extern int dccp_sendmsg(struct kiocb *iocb, struct sock *sk,
struct msghdr *msg, size_t size);
extern int dccp_recvmsg(struct kiocb *iocb, struct sock *sk,
struct msghdr *msg, size_t len, int nonblock,
int flags, int *addr_len);
extern void dccp_shutdown(struct sock *sk, int how);
extern int inet_dccp_listen(struct socket *sock, int backlog);
extern unsigned int dccp_poll(struct file *file, struct socket *sock,
poll_table *wait);
extern int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr,
int addr_len);
extern struct sk_buff *dccp_ctl_make_reset(struct sock *sk,
struct sk_buff *skb);
extern int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code);
extern void dccp_send_close(struct sock *sk, const int active);
extern int dccp_invalid_packet(struct sk_buff *skb);
extern u32 dccp_sample_rtt(struct sock *sk, long delta);
static inline int dccp_bad_service_code(const struct sock *sk,
const __be32 service)
const struct dccp_sock *dp = dccp_sk(sk);
if (dp->dccps_service == service)
return 0;
return !dccp_list_has_service(dp->dccps_service_list, service);
* dccp_skb_cb - DCCP per-packet control information
* @dccpd_type: one of %dccp_pkt_type (or unknown)
* @dccpd_ccval: CCVal field (5.1), see e.g. RFC 4342, 8.1
* @dccpd_reset_code: one of %dccp_reset_codes
* @dccpd_reset_data: Data1..3 fields (depend on @dccpd_reset_code)
* @dccpd_opt_len: total length of all options (5.8) in the packet
* @dccpd_seq: sequence number
* @dccpd_ack_seq: acknowledgment number subheader field value
* This is used for transmission as well as for reception.
struct dccp_skb_cb {
union {
struct inet_skb_parm h4;
#if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
struct inet6_skb_parm h6;
} header;
__u8 dccpd_type:4;
__u8 dccpd_ccval:4;
__u8 dccpd_reset_code,
__u16 dccpd_opt_len;
__u64 dccpd_seq;
__u64 dccpd_ack_seq;
#define DCCP_SKB_CB(__skb) ((struct dccp_skb_cb *)&((__skb)->cb[0]))
/* RFC 4340, sec. 7.7 */
static inline int dccp_non_data_packet(const struct sk_buff *skb)
const __u8 type = DCCP_SKB_CB(skb)->dccpd_type;
return type == DCCP_PKT_ACK ||
type == DCCP_PKT_CLOSE ||
type == DCCP_PKT_RESET ||
type == DCCP_PKT_SYNC ||
/* RFC 4340, sec. 7.7 */
static inline int dccp_data_packet(const struct sk_buff *skb)
const __u8 type = DCCP_SKB_CB(skb)->dccpd_type;
return type == DCCP_PKT_DATA ||
static inline int dccp_packet_without_ack(const struct sk_buff *skb)
const __u8 type = DCCP_SKB_CB(skb)->dccpd_type;
return type == DCCP_PKT_DATA || type == DCCP_PKT_REQUEST;
static inline void dccp_hdr_set_seq(struct dccp_hdr *dh, const u64 gss)
struct dccp_hdr_ext *dhx = (struct dccp_hdr_ext *)((void *)dh +
dh->dccph_seq2 = 0;
dh->dccph_seq = htons((gss >> 32) & 0xfffff);
dhx->dccph_seq_low = htonl(gss & 0xffffffff);
static inline void dccp_hdr_set_ack(struct dccp_hdr_ack_bits *dhack,
const u64 gsr)
dhack->dccph_reserved1 = 0;
dhack->dccph_ack_nr_high = htons(gsr >> 32);
dhack->dccph_ack_nr_low = htonl(gsr & 0xffffffff);
static inline void dccp_update_gsr(struct sock *sk, u64 seq)
struct dccp_sock *dp = dccp_sk(sk);
if (after48(seq, dp->dccps_gsr))
dp->dccps_gsr = seq;
/* Sequence validity window depends on remote Sequence Window (7.5.1) */
dp->dccps_swl = SUB48(ADD48(dp->dccps_gsr, 1), dp->dccps_r_seq_win / 4);
* Adjust SWL so that it is not below ISR. In contrast to RFC 4340,
* 7.5.1 we perform this check beyond the initial handshake: W/W' are
* always > 32, so for the first W/W' packets in the lifetime of a
* connection we always have to adjust SWL.
* A second reason why we are doing this is that the window depends on
* the feature-remote value of Sequence Window: nothing stops the peer
* from updating this value while we are busy adjusting SWL for the
* first W packets (we would have to count from scratch again then).
* Therefore it is safer to always make sure that the Sequence Window
* is not artificially extended by a peer who grows SWL downwards by
* continually updating the feature-remote Sequence-Window.
* If sequence numbers wrap it is bad luck. But that will take a while
* (48 bit), and this measure prevents Sequence-number attacks.
if (before48(dp->dccps_swl, dp->dccps_isr))
dp->dccps_swl = dp->dccps_isr;
dp->dccps_swh = ADD48(dp->dccps_gsr, (3 * dp->dccps_r_seq_win) / 4);
static inline void dccp_update_gss(struct sock *sk, u64 seq)
struct dccp_sock *dp = dccp_sk(sk);
dp->dccps_gss = seq;
/* Ack validity window depends on local Sequence Window value (7.5.1) */
dp->dccps_awl = SUB48(ADD48(dp->dccps_gss, 1), dp->dccps_l_seq_win);
/* Adjust AWL so that it is not below ISS - see comment above for SWL */
if (before48(dp->dccps_awl, dp->dccps_iss))
dp->dccps_awl = dp->dccps_iss;
dp->dccps_awh = dp->dccps_gss;
static inline int dccp_ackvec_pending(const struct sock *sk)
return dccp_sk(sk)->dccps_hc_rx_ackvec != NULL &&
static inline int dccp_ack_pending(const struct sock *sk)
return dccp_ackvec_pending(sk) || inet_csk_ack_scheduled(sk);
extern int dccp_feat_finalise_settings(struct dccp_sock *dp);
extern int dccp_feat_server_ccid_dependencies(struct dccp_request_sock *dreq);
extern int dccp_feat_insert_opts(struct dccp_sock*, struct dccp_request_sock*,
struct sk_buff *skb);
extern int dccp_feat_activate_values(struct sock *sk, struct list_head *fn);
extern void dccp_feat_list_purge(struct list_head *fn_list);
extern int dccp_insert_options(struct sock *sk, struct sk_buff *skb);
extern int dccp_insert_options_rsk(struct dccp_request_sock*, struct sk_buff*);
extern int dccp_insert_option_elapsed_time(struct sk_buff *skb, u32 elapsed);
extern u32 dccp_timestamp(void);
extern void dccp_timestamping_init(void);
extern int dccp_insert_option(struct sk_buff *skb, unsigned char option,
const void *value, unsigned char len);
extern int dccp_sysctl_init(void);
extern void dccp_sysctl_exit(void);
static inline int dccp_sysctl_init(void)
return 0;
static inline void dccp_sysctl_exit(void)
#endif /* _DCCP_H */