net/dccp/timer.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *  net/dccp/timer.c
   4  *
   5  *  An implementation of the DCCP protocol
   6  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   7  */
   8
   9 #include <linux/dccp.h>
  10 #include <linux/skbuff.h>
  11 #include <linux/export.h>
  12
  13 #include "dccp.h"
  14
  15 /* sysctl variables governing numbers of retransmission attempts */
  16 int  sysctl_dccp_request_retries        __read_mostly = TCP_SYN_RETRIES;
  17 int  sysctl_dccp_retries1               __read_mostly = TCP_RETR1;
  18 int  sysctl_dccp_retries2               __read_mostly = TCP_RETR2;
  19
  20 static void dccp_write_err(struct sock *sk)
  21 {
  22         sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
  23         sk->sk_error_report(sk);
  24
  25         dccp_send_reset(sk, DCCP_RESET_CODE_ABORTED);
  26         dccp_done(sk);
  27         __DCCP_INC_STATS(DCCP_MIB_ABORTONTIMEOUT);
  28 }
  29
  30 /* A write timeout has occurred. Process the after effects. */
  31 static int dccp_write_timeout(struct sock *sk)
  32 {
  33         const struct inet_connection_sock *icsk = inet_csk(sk);
  34         int retry_until;
  35
  36         if (sk->sk_state == DCCP_REQUESTING || sk->sk_state == DCCP_PARTOPEN) {
  37                 if (icsk->icsk_retransmits != 0)
  38                         dst_negative_advice(sk);
  39                 retry_until = icsk->icsk_syn_retries ?
  40                             : sysctl_dccp_request_retries;
  41         } else {
  42                 if (icsk->icsk_retransmits >= sysctl_dccp_retries1) {
  43                         /* NOTE. draft-ietf-tcpimpl-pmtud-01.txt requires pmtu
  44                            black hole detection. :-(
  45
  46                            It is place to make it. It is not made. I do not want
  47                            to make it. It is disguisting. It does not work in any
  48                            case. Let me to cite the same draft, which requires for
  49                            us to implement this:
  50
  51    "The one security concern raised by this memo is that ICMP black holes
  52    are often caused by over-zealous security administrators who block
  53    all ICMP messages.  It is vitally important that those who design and
  54    deploy security systems understand the impact of strict filtering on
  55    upper-layer protocols.  The safest web site in the world is worthless
  56    if most TCP implementations cannot transfer data from it.  It would
  57    be far nicer to have all of the black holes fixed rather than fixing
  58    all of the TCP implementations."
  59
  60                            Golden words :-).
  61                    */
  62
  63                         dst_negative_advice(sk);
  64                 }
  65
  66                 retry_until = sysctl_dccp_retries2;
  67                 /*
  68                  * FIXME: see tcp_write_timout and tcp_out_of_resources
  69                  */
  70         }
  71
  72         if (icsk->icsk_retransmits >= retry_until) {
  73                 /* Has it gone just too far? */
  74                 dccp_write_err(sk);
  75                 return 1;
  76         }
  77         return 0;
  78 }
  79
  80 /*
  81  *      The DCCP retransmit timer.
  82  */
  83 static void dccp_retransmit_timer(struct sock *sk)
  84 {
  85         struct inet_connection_sock *icsk = inet_csk(sk);
  86
  87         /*
  88          * More than 4MSL (8 minutes) has passed, a RESET(aborted) was
  89          * sent, no need to retransmit, this sock is dead.
  90          */
  91         if (dccp_write_timeout(sk))
  92                 return;
  93
  94         /*
  95          * We want to know the number of packets retransmitted, not the
  96          * total number of retransmissions of clones of original packets.
  97          */
  98         if (icsk->icsk_retransmits == 0)
  99                 __DCCP_INC_STATS(DCCP_MIB_TIMEOUTS);
 100
 101         if (dccp_retransmit_skb(sk) != 0) {
 102                 /*
 103                  * Retransmission failed because of local congestion,
 104                  * do not backoff.
 105                  */
 106                 if (--icsk->icsk_retransmits == 0)
 107                         icsk->icsk_retransmits = 1;
 108                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 109                                           min(icsk->icsk_rto,
 110                                               TCP_RESOURCE_PROBE_INTERVAL),
 111                                           DCCP_RTO_MAX);
 112                 return;
 113         }
 114
 115         icsk->icsk_backoff++;
 116
 117         icsk->icsk_rto = min(icsk->icsk_rto << 1, DCCP_RTO_MAX);
 118         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto,
 119                                   DCCP_RTO_MAX);
 120         if (icsk->icsk_retransmits > sysctl_dccp_retries1)
 121                 __sk_dst_reset(sk);
 122 }
 123
 124 static void dccp_write_timer(struct timer_list *t)
 125 {
 126         struct inet_connection_sock *icsk =
 127                         from_timer(icsk, t, icsk_retransmit_timer);
 128         struct sock *sk = &icsk->icsk_inet.sk;
 129         int event = 0;
 130
 131         bh_lock_sock(sk);
 132         if (sock_owned_by_user(sk)) {
 133                 /* Try again later */
 134                 sk_reset_timer(sk, &icsk->icsk_retransmit_timer,
 135                                jiffies + (HZ / 20));
 136                 goto out;
 137         }
 138
 139         if (sk->sk_state == DCCP_CLOSED || !icsk->icsk_pending)
 140                 goto out;
 141
 142         if (time_after(icsk->icsk_timeout, jiffies)) {
 143                 sk_reset_timer(sk, &icsk->icsk_retransmit_timer,
 144                                icsk->icsk_timeout);
 145                 goto out;
 146         }
 147
 148         event = icsk->icsk_pending;
 149         icsk->icsk_pending = 0;
 150
 151         switch (event) {
 152         case ICSK_TIME_RETRANS:
 153                 dccp_retransmit_timer(sk);
 154                 break;
 155         }
 156 out:
 157         bh_unlock_sock(sk);
 158         sock_put(sk);
 159 }
 160
 161 static void dccp_keepalive_timer(struct timer_list *t)
 162 {
 163         struct sock *sk = from_timer(sk, t, sk_timer);
 164
 165         pr_err("dccp should not use a keepalive timer !\n");
 166         sock_put(sk);
 167 }
 168
 169 /* This is the same as tcp_delack_timer, sans prequeue & mem_reclaim stuff */
 170 static void dccp_delack_timer(struct timer_list *t)
 171 {
 172         struct inet_connection_sock *icsk =
 173                         from_timer(icsk, t, icsk_delack_timer);
 174         struct sock *sk = &icsk->icsk_inet.sk;
 175
 176         bh_lock_sock(sk);
 177         if (sock_owned_by_user(sk)) {
 178                 /* Try again later. */
 179                 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
 180                 sk_reset_timer(sk, &icsk->icsk_delack_timer,
 181                                jiffies + TCP_DELACK_MIN);
 182                 goto out;
 183         }
 184
 185         if (sk->sk_state == DCCP_CLOSED ||
 186             !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
 187                 goto out;
 188         if (time_after(icsk->icsk_ack.timeout, jiffies)) {
 189                 sk_reset_timer(sk, &icsk->icsk_delack_timer,
 190                                icsk->icsk_ack.timeout);
 191                 goto out;
 192         }
 193
 194         icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
 195
 196         if (inet_csk_ack_scheduled(sk)) {
 197                 if (!inet_csk_in_pingpong_mode(sk)) {
 198                         /* Delayed ACK missed: inflate ATO. */
 199                         icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1,
 200                                                  icsk->icsk_rto);
 201                 } else {
 202                         /* Delayed ACK missed: leave pingpong mode and
 203                          * deflate ATO.
 204                          */
 205                         inet_csk_exit_pingpong_mode(sk);
 206                         icsk->icsk_ack.ato = TCP_ATO_MIN;
 207                 }
 208                 dccp_send_ack(sk);
 209                 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS);
 210         }
 211 out:
 212         bh_unlock_sock(sk);
 213         sock_put(sk);
 214 }
 215
 216 /**
 217  * dccp_write_xmitlet  -  Workhorse for CCID packet dequeueing interface
 218  * @t: pointer to the tasklet associated with this handler
 219  *
 220  * See the comments above %ccid_dequeueing_decision for supported modes.
 221  */
 222 static void dccp_write_xmitlet(struct tasklet_struct *t)
 223 {
 224         struct dccp_sock *dp = from_tasklet(dp, t, dccps_xmitlet);
 225         struct sock *sk = &dp->dccps_inet_connection.icsk_inet.sk;
 226
 227         bh_lock_sock(sk);
 228         if (sock_owned_by_user(sk))
 229                 sk_reset_timer(sk, &dccp_sk(sk)->dccps_xmit_timer, jiffies + 1);
 230         else
 231                 dccp_write_xmit(sk);
 232         bh_unlock_sock(sk);
 233         sock_put(sk);
 234 }
 235
 236 static void dccp_write_xmit_timer(struct timer_list *t)
 237 {
 238         struct dccp_sock *dp = from_timer(dp, t, dccps_xmit_timer);
 239
 240         dccp_write_xmitlet(&dp->dccps_xmitlet);
 241 }
 242
 243 void dccp_init_xmit_timers(struct sock *sk)
 244 {
 245         struct dccp_sock *dp = dccp_sk(sk);
 246
 247         tasklet_setup(&dp->dccps_xmitlet, dccp_write_xmitlet);
 248         timer_setup(&dp->dccps_xmit_timer, dccp_write_xmit_timer, 0);
 249         inet_csk_init_xmit_timers(sk, &dccp_write_timer, &dccp_delack_timer,
 250                                   &dccp_keepalive_timer);
 251 }
 252
 253 static ktime_t dccp_timestamp_seed;
 254 /**
 255  * dccp_timestamp  -  10s of microseconds time source
 256  * Returns the number of 10s of microseconds since loading DCCP. This is native
 257  * DCCP time difference format (RFC 4340, sec. 13).
 258  * Please note: This will wrap around about circa every 11.9 hours.
 259  */
 260 u32 dccp_timestamp(void)
 261 {
 262         u64 delta = (u64)ktime_us_delta(ktime_get_real(), dccp_timestamp_seed);
 263
 264         do_div(delta, 10);
 265         return delta;
 266 }
 267 EXPORT_SYMBOL_GPL(dccp_timestamp);
 268
 269 void __init dccp_timestamping_init(void)
 270 {
 271         dccp_timestamp_seed = ktime_get_real();
 272 }