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(unsigned long data) 129 { 130 struct sock *sk = (struct sock *)data; 131 struct inet_connection_sock *icsk = inet_csk(sk); 132 int event = 0; 133 134 bh_lock_sock(sk); 135 if (sock_owned_by_user(sk)) { 136 /* Try again later */ 137 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, 138 jiffies + (HZ / 20)); 139 goto out; 140 } 141 142 if (sk->sk_state == DCCP_CLOSED || !icsk->icsk_pending) 143 goto out; 144 145 if (time_after(icsk->icsk_timeout, jiffies)) { 146 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, 147 icsk->icsk_timeout); 148 goto out; 149 } 150 151 event = icsk->icsk_pending; 152 icsk->icsk_pending = 0; 153 154 switch (event) { 155 case ICSK_TIME_RETRANS: 156 dccp_retransmit_timer(sk); 157 break; 158 } 159 out: 160 bh_unlock_sock(sk); 161 sock_put(sk); 162 } 163 164 static void dccp_keepalive_timer(unsigned long data) 165 { 166 struct sock *sk = (struct sock *)data; 167 168 pr_err("dccp should not use a keepalive timer !\n"); 169 sock_put(sk); 170 } 171 172 /* This is the same as tcp_delack_timer, sans prequeue & mem_reclaim stuff */ 173 static void dccp_delack_timer(unsigned long data) 174 { 175 struct sock *sk = (struct sock *)data; 176 struct inet_connection_sock *icsk = inet_csk(sk); 177 178 bh_lock_sock(sk); 179 if (sock_owned_by_user(sk)) { 180 /* Try again later. */ 181 icsk->icsk_ack.blocked = 1; 182 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED); 183 sk_reset_timer(sk, &icsk->icsk_delack_timer, 184 jiffies + TCP_DELACK_MIN); 185 goto out; 186 } 187 188 if (sk->sk_state == DCCP_CLOSED || 189 !(icsk->icsk_ack.pending & ICSK_ACK_TIMER)) 190 goto out; 191 if (time_after(icsk->icsk_ack.timeout, jiffies)) { 192 sk_reset_timer(sk, &icsk->icsk_delack_timer, 193 icsk->icsk_ack.timeout); 194 goto out; 195 } 196 197 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER; 198 199 if (inet_csk_ack_scheduled(sk)) { 200 if (!icsk->icsk_ack.pingpong) { 201 /* Delayed ACK missed: inflate ATO. */ 202 icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, 203 icsk->icsk_rto); 204 } else { 205 /* Delayed ACK missed: leave pingpong mode and 206 * deflate ATO. 207 */ 208 icsk->icsk_ack.pingpong = 0; 209 icsk->icsk_ack.ato = TCP_ATO_MIN; 210 } 211 dccp_send_ack(sk); 212 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS); 213 } 214 out: 215 bh_unlock_sock(sk); 216 sock_put(sk); 217 } 218 219 /** 220 * dccp_write_xmitlet - Workhorse for CCID packet dequeueing interface 221 * See the comments above %ccid_dequeueing_decision for supported modes. 222 */ 223 static void dccp_write_xmitlet(unsigned long data) 224 { 225 struct sock *sk = (struct sock *)data; 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 } 234 235 static void dccp_write_xmit_timer(unsigned long data) 236 { 237 dccp_write_xmitlet(data); 238 sock_put((struct sock *)data); 239 } 240 241 void dccp_init_xmit_timers(struct sock *sk) 242 { 243 struct dccp_sock *dp = dccp_sk(sk); 244 245 tasklet_init(&dp->dccps_xmitlet, dccp_write_xmitlet, (unsigned long)sk); 246 setup_timer(&dp->dccps_xmit_timer, dccp_write_xmit_timer, 247 (unsigned long)sk); 248 inet_csk_init_xmit_timers(sk, &dccp_write_timer, &dccp_delack_timer, 249 &dccp_keepalive_timer); 250 } 251 252 static ktime_t dccp_timestamp_seed; 253 /** 254 * dccp_timestamp - 10s of microseconds time source 255 * Returns the number of 10s of microseconds since loading DCCP. This is native 256 * DCCP time difference format (RFC 4340, sec. 13). 257 * Please note: This will wrap around about circa every 11.9 hours. 258 */ 259 u32 dccp_timestamp(void) 260 { 261 u64 delta = (u64)ktime_us_delta(ktime_get_real(), dccp_timestamp_seed); 262 263 do_div(delta, 10); 264 return delta; 265 } 266 EXPORT_SYMBOL_GPL(dccp_timestamp); 267 268 void __init dccp_timestamping_init(void) 269 { 270 dccp_timestamp_seed = ktime_get_real(); 271 } 272