1 /* 2 * net/dccp/timer.c 3 * 4 * An implementation of the DCCP protocol 5 * Arnaldo Carvalho de Melo <acme@conectiva.com.br> 6 * 7 * This program is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU General Public License 9 * as published by the Free Software Foundation; either version 10 * 2 of the License, or (at your option) any later version. 11 */ 12 13 #include <linux/dccp.h> 14 #include <linux/skbuff.h> 15 #include <linux/export.h> 16 17 #include "dccp.h" 18 19 /* sysctl variables governing numbers of retransmission attempts */ 20 int sysctl_dccp_request_retries __read_mostly = TCP_SYN_RETRIES; 21 int sysctl_dccp_retries1 __read_mostly = TCP_RETR1; 22 int sysctl_dccp_retries2 __read_mostly = TCP_RETR2; 23 24 static void dccp_write_err(struct sock *sk) 25 { 26 sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT; 27 sk->sk_error_report(sk); 28 29 dccp_send_reset(sk, DCCP_RESET_CODE_ABORTED); 30 dccp_done(sk); 31 __DCCP_INC_STATS(DCCP_MIB_ABORTONTIMEOUT); 32 } 33 34 /* A write timeout has occurred. Process the after effects. */ 35 static int dccp_write_timeout(struct sock *sk) 36 { 37 const struct inet_connection_sock *icsk = inet_csk(sk); 38 int retry_until; 39 40 if (sk->sk_state == DCCP_REQUESTING || sk->sk_state == DCCP_PARTOPEN) { 41 if (icsk->icsk_retransmits != 0) 42 dst_negative_advice(sk); 43 retry_until = icsk->icsk_syn_retries ? 44 : sysctl_dccp_request_retries; 45 } else { 46 if (icsk->icsk_retransmits >= sysctl_dccp_retries1) { 47 /* NOTE. draft-ietf-tcpimpl-pmtud-01.txt requires pmtu 48 black hole detection. :-( 49 50 It is place to make it. It is not made. I do not want 51 to make it. It is disguisting. It does not work in any 52 case. Let me to cite the same draft, which requires for 53 us to implement this: 54 55 "The one security concern raised by this memo is that ICMP black holes 56 are often caused by over-zealous security administrators who block 57 all ICMP messages. It is vitally important that those who design and 58 deploy security systems understand the impact of strict filtering on 59 upper-layer protocols. The safest web site in the world is worthless 60 if most TCP implementations cannot transfer data from it. It would 61 be far nicer to have all of the black holes fixed rather than fixing 62 all of the TCP implementations." 63 64 Golden words :-). 65 */ 66 67 dst_negative_advice(sk); 68 } 69 70 retry_until = sysctl_dccp_retries2; 71 /* 72 * FIXME: see tcp_write_timout and tcp_out_of_resources 73 */ 74 } 75 76 if (icsk->icsk_retransmits >= retry_until) { 77 /* Has it gone just too far? */ 78 dccp_write_err(sk); 79 return 1; 80 } 81 return 0; 82 } 83 84 /* 85 * The DCCP retransmit timer. 86 */ 87 static void dccp_retransmit_timer(struct sock *sk) 88 { 89 struct inet_connection_sock *icsk = inet_csk(sk); 90 91 /* 92 * More than than 4MSL (8 minutes) has passed, a RESET(aborted) was 93 * sent, no need to retransmit, this sock is dead. 94 */ 95 if (dccp_write_timeout(sk)) 96 return; 97 98 /* 99 * We want to know the number of packets retransmitted, not the 100 * total number of retransmissions of clones of original packets. 101 */ 102 if (icsk->icsk_retransmits == 0) 103 __DCCP_INC_STATS(DCCP_MIB_TIMEOUTS); 104 105 if (dccp_retransmit_skb(sk) != 0) { 106 /* 107 * Retransmission failed because of local congestion, 108 * do not backoff. 109 */ 110 if (--icsk->icsk_retransmits == 0) 111 icsk->icsk_retransmits = 1; 112 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 113 min(icsk->icsk_rto, 114 TCP_RESOURCE_PROBE_INTERVAL), 115 DCCP_RTO_MAX); 116 return; 117 } 118 119 icsk->icsk_backoff++; 120 121 icsk->icsk_rto = min(icsk->icsk_rto << 1, DCCP_RTO_MAX); 122 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, 123 DCCP_RTO_MAX); 124 if (icsk->icsk_retransmits > sysctl_dccp_retries1) 125 __sk_dst_reset(sk); 126 } 127 128 static void dccp_write_timer(struct timer_list *t) 129 { 130 struct inet_connection_sock *icsk = 131 from_timer(icsk, t, icsk_retransmit_timer); 132 struct sock *sk = &icsk->icsk_inet.sk; 133 int event = 0; 134 135 bh_lock_sock(sk); 136 if (sock_owned_by_user(sk)) { 137 /* Try again later */ 138 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, 139 jiffies + (HZ / 20)); 140 goto out; 141 } 142 143 if (sk->sk_state == DCCP_CLOSED || !icsk->icsk_pending) 144 goto out; 145 146 if (time_after(icsk->icsk_timeout, jiffies)) { 147 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, 148 icsk->icsk_timeout); 149 goto out; 150 } 151 152 event = icsk->icsk_pending; 153 icsk->icsk_pending = 0; 154 155 switch (event) { 156 case ICSK_TIME_RETRANS: 157 dccp_retransmit_timer(sk); 158 break; 159 } 160 out: 161 bh_unlock_sock(sk); 162 sock_put(sk); 163 } 164 165 static void dccp_keepalive_timer(struct timer_list *t) 166 { 167 struct sock *sk = from_timer(sk, t, sk_timer); 168 169 pr_err("dccp should not use a keepalive timer !\n"); 170 sock_put(sk); 171 } 172 173 /* This is the same as tcp_delack_timer, sans prequeue & mem_reclaim stuff */ 174 static void dccp_delack_timer(struct timer_list *t) 175 { 176 struct inet_connection_sock *icsk = 177 from_timer(icsk, t, icsk_delack_timer); 178 struct sock *sk = &icsk->icsk_inet.sk; 179 180 bh_lock_sock(sk); 181 if (sock_owned_by_user(sk)) { 182 /* Try again later. */ 183 icsk->icsk_ack.blocked = 1; 184 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED); 185 sk_reset_timer(sk, &icsk->icsk_delack_timer, 186 jiffies + TCP_DELACK_MIN); 187 goto out; 188 } 189 190 if (sk->sk_state == DCCP_CLOSED || 191 !(icsk->icsk_ack.pending & ICSK_ACK_TIMER)) 192 goto out; 193 if (time_after(icsk->icsk_ack.timeout, jiffies)) { 194 sk_reset_timer(sk, &icsk->icsk_delack_timer, 195 icsk->icsk_ack.timeout); 196 goto out; 197 } 198 199 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER; 200 201 if (inet_csk_ack_scheduled(sk)) { 202 if (!icsk->icsk_ack.pingpong) { 203 /* Delayed ACK missed: inflate ATO. */ 204 icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, 205 icsk->icsk_rto); 206 } else { 207 /* Delayed ACK missed: leave pingpong mode and 208 * deflate ATO. 209 */ 210 icsk->icsk_ack.pingpong = 0; 211 icsk->icsk_ack.ato = TCP_ATO_MIN; 212 } 213 dccp_send_ack(sk); 214 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS); 215 } 216 out: 217 bh_unlock_sock(sk); 218 sock_put(sk); 219 } 220 221 /** 222 * dccp_write_xmitlet - Workhorse for CCID packet dequeueing interface 223 * See the comments above %ccid_dequeueing_decision for supported modes. 224 */ 225 static void dccp_write_xmitlet(unsigned long data) 226 { 227 struct sock *sk = (struct sock *)data; 228 229 bh_lock_sock(sk); 230 if (sock_owned_by_user(sk)) 231 sk_reset_timer(sk, &dccp_sk(sk)->dccps_xmit_timer, jiffies + 1); 232 else 233 dccp_write_xmit(sk); 234 bh_unlock_sock(sk); 235 sock_put(sk); 236 } 237 238 static void dccp_write_xmit_timer(struct timer_list *t) 239 { 240 struct dccp_sock *dp = from_timer(dp, t, dccps_xmit_timer); 241 struct sock *sk = &dp->dccps_inet_connection.icsk_inet.sk; 242 243 dccp_write_xmitlet((unsigned long)sk); 244 } 245 246 void dccp_init_xmit_timers(struct sock *sk) 247 { 248 struct dccp_sock *dp = dccp_sk(sk); 249 250 tasklet_init(&dp->dccps_xmitlet, dccp_write_xmitlet, (unsigned long)sk); 251 timer_setup(&dp->dccps_xmit_timer, dccp_write_xmit_timer, 0); 252 inet_csk_init_xmit_timers(sk, &dccp_write_timer, &dccp_delack_timer, 253 &dccp_keepalive_timer); 254 } 255 256 static ktime_t dccp_timestamp_seed; 257 /** 258 * dccp_timestamp - 10s of microseconds time source 259 * Returns the number of 10s of microseconds since loading DCCP. This is native 260 * DCCP time difference format (RFC 4340, sec. 13). 261 * Please note: This will wrap around about circa every 11.9 hours. 262 */ 263 u32 dccp_timestamp(void) 264 { 265 u64 delta = (u64)ktime_us_delta(ktime_get_real(), dccp_timestamp_seed); 266 267 do_div(delta, 10); 268 return delta; 269 } 270 EXPORT_SYMBOL_GPL(dccp_timestamp); 271 272 void __init dccp_timestamping_init(void) 273 { 274 dccp_timestamp_seed = ktime_get_real(); 275 } 276