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 = READ_ONCE(sk->sk_err_soft) ? : ETIMEDOUT; 23 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_t(u32, 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 } 273