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* An implementation of the DCCP protocol
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* Arnaldo Carvalho de Melo <acme@conectiva.com.br>
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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#include <linux/dccp.h>
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#include <linux/skbuff.h>
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#include <linux/export.h>
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/* sysctl variables governing numbers of retransmission attempts */
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int sysctl_dccp_request_retries __read_mostly = TCP_SYN_RETRIES;
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int sysctl_dccp_retries1 __read_mostly = TCP_RETR1;
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int sysctl_dccp_retries2 __read_mostly = TCP_RETR2;
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static void dccp_write_err(struct sock *sk)
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sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
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sk->sk_error_report(sk);
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dccp_send_reset(sk, DCCP_RESET_CODE_ABORTED);
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DCCP_INC_STATS_BH(DCCP_MIB_ABORTONTIMEOUT);
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/* A write timeout has occurred. Process the after effects. */
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static int dccp_write_timeout(struct sock *sk)
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const struct inet_connection_sock *icsk = inet_csk(sk);
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if (sk->sk_state == DCCP_REQUESTING || sk->sk_state == DCCP_PARTOPEN) {
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if (icsk->icsk_retransmits != 0)
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dst_negative_advice(sk);
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retry_until = icsk->icsk_syn_retries ?
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: sysctl_dccp_request_retries;
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if (icsk->icsk_retransmits >= sysctl_dccp_retries1) {
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/* NOTE. draft-ietf-tcpimpl-pmtud-01.txt requires pmtu
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black hole detection. :-(
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It is place to make it. It is not made. I do not want
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to make it. It is disguisting. It does not work in any
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case. Let me to cite the same draft, which requires for
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"The one security concern raised by this memo is that ICMP black holes
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are often caused by over-zealous security administrators who block
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all ICMP messages. It is vitally important that those who design and
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deploy security systems understand the impact of strict filtering on
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upper-layer protocols. The safest web site in the world is worthless
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if most TCP implementations cannot transfer data from it. It would
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be far nicer to have all of the black holes fixed rather than fixing
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all of the TCP implementations."
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dst_negative_advice(sk);
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retry_until = sysctl_dccp_retries2;
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* FIXME: see tcp_write_timout and tcp_out_of_resources
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if (icsk->icsk_retransmits >= retry_until) {
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/* Has it gone just too far? */
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* The DCCP retransmit timer.
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static void dccp_retransmit_timer(struct sock *sk)
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struct inet_connection_sock *icsk = inet_csk(sk);
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* More than than 4MSL (8 minutes) has passed, a RESET(aborted) was
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* sent, no need to retransmit, this sock is dead.
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if (dccp_write_timeout(sk))
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* We want to know the number of packets retransmitted, not the
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* total number of retransmissions of clones of original packets.
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if (icsk->icsk_retransmits == 0)
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DCCP_INC_STATS_BH(DCCP_MIB_TIMEOUTS);
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if (dccp_retransmit_skb(sk) != 0) {
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* Retransmission failed because of local congestion,
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if (--icsk->icsk_retransmits == 0)
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icsk->icsk_retransmits = 1;
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inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
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TCP_RESOURCE_PROBE_INTERVAL),
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icsk->icsk_backoff++;
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icsk->icsk_rto = min(icsk->icsk_rto << 1, DCCP_RTO_MAX);
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inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto,
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if (icsk->icsk_retransmits > sysctl_dccp_retries1)
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static void dccp_write_timer(unsigned long data)
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struct sock *sk = (struct sock *)data;
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struct inet_connection_sock *icsk = inet_csk(sk);
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if (sock_owned_by_user(sk)) {
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/* Try again later */
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sk_reset_timer(sk, &icsk->icsk_retransmit_timer,
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jiffies + (HZ / 20));
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if (sk->sk_state == DCCP_CLOSED || !icsk->icsk_pending)
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if (time_after(icsk->icsk_timeout, jiffies)) {
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sk_reset_timer(sk, &icsk->icsk_retransmit_timer,
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event = icsk->icsk_pending;
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icsk->icsk_pending = 0;
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case ICSK_TIME_RETRANS:
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dccp_retransmit_timer(sk);
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* Timer for listening sockets
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static void dccp_response_timer(struct sock *sk)
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inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL, DCCP_TIMEOUT_INIT,
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static void dccp_keepalive_timer(unsigned long data)
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struct sock *sk = (struct sock *)data;
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/* Only process if socket is not in use. */
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if (sock_owned_by_user(sk)) {
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/* Try again later. */
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inet_csk_reset_keepalive_timer(sk, HZ / 20);
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if (sk->sk_state == DCCP_LISTEN) {
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dccp_response_timer(sk);
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/* This is the same as tcp_delack_timer, sans prequeue & mem_reclaim stuff */
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static void dccp_delack_timer(unsigned long data)
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struct sock *sk = (struct sock *)data;
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struct inet_connection_sock *icsk = inet_csk(sk);
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if (sock_owned_by_user(sk)) {
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/* Try again later. */
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icsk->icsk_ack.blocked = 1;
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NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
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sk_reset_timer(sk, &icsk->icsk_delack_timer,
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jiffies + TCP_DELACK_MIN);
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if (sk->sk_state == DCCP_CLOSED ||
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!(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
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if (time_after(icsk->icsk_ack.timeout, jiffies)) {
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sk_reset_timer(sk, &icsk->icsk_delack_timer,
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icsk->icsk_ack.timeout);
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icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
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if (inet_csk_ack_scheduled(sk)) {
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if (!icsk->icsk_ack.pingpong) {
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/* Delayed ACK missed: inflate ATO. */
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icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1,
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/* Delayed ACK missed: leave pingpong mode and
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icsk->icsk_ack.pingpong = 0;
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icsk->icsk_ack.ato = TCP_ATO_MIN;
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NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKS);
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* dccp_write_xmitlet - Workhorse for CCID packet dequeueing interface
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* See the comments above %ccid_dequeueing_decision for supported modes.
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static void dccp_write_xmitlet(unsigned long data)
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struct sock *sk = (struct sock *)data;
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if (sock_owned_by_user(sk))
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sk_reset_timer(sk, &dccp_sk(sk)->dccps_xmit_timer, jiffies + 1);
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static void dccp_write_xmit_timer(unsigned long data)
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dccp_write_xmitlet(data);
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sock_put((struct sock *)data);
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void dccp_init_xmit_timers(struct sock *sk)
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struct dccp_sock *dp = dccp_sk(sk);
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tasklet_init(&dp->dccps_xmitlet, dccp_write_xmitlet, (unsigned long)sk);
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setup_timer(&dp->dccps_xmit_timer, dccp_write_xmit_timer,
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inet_csk_init_xmit_timers(sk, &dccp_write_timer, &dccp_delack_timer,
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&dccp_keepalive_timer);
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static ktime_t dccp_timestamp_seed;
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* dccp_timestamp - 10s of microseconds time source
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* Returns the number of 10s of microseconds since loading DCCP. This is native
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* DCCP time difference format (RFC 4340, sec. 13).
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* Please note: This will wrap around about circa every 11.9 hours.
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u32 dccp_timestamp(void)
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s64 delta = ktime_us_delta(ktime_get_real(), dccp_timestamp_seed);
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EXPORT_SYMBOL_GPL(dccp_timestamp);
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void __init dccp_timestamping_init(void)
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dccp_timestamp_seed = ktime_get_real();