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 16 #include "dccp.h" 17 18 /* sysctl variables governing numbers of retransmission attempts */ 19 int sysctl_dccp_request_retries __read_mostly = TCP_SYN_RETRIES; 20 int sysctl_dccp_retries1 __read_mostly = TCP_RETR1; 21 int sysctl_dccp_retries2 __read_mostly = TCP_RETR2; 22 23 static void dccp_write_err(struct sock *sk) 24 { 25 sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT; 26 sk->sk_error_report(sk); 27 28 dccp_send_reset(sk, DCCP_RESET_CODE_ABORTED); 29 dccp_done(sk); 30 DCCP_INC_STATS_BH(DCCP_MIB_ABORTONTIMEOUT); 31 } 32 33 /* A write timeout has occurred. Process the after effects. */ 34 static int dccp_write_timeout(struct sock *sk) 35 { 36 const struct inet_connection_sock *icsk = inet_csk(sk); 37 int retry_until; 38 39 if (sk->sk_state == DCCP_REQUESTING || sk->sk_state == DCCP_PARTOPEN) { 40 if (icsk->icsk_retransmits != 0) 41 dst_negative_advice(&sk->sk_dst_cache); 42 retry_until = icsk->icsk_syn_retries ? 43 : sysctl_dccp_request_retries; 44 } else { 45 if (icsk->icsk_retransmits >= sysctl_dccp_retries1) { 46 /* NOTE. draft-ietf-tcpimpl-pmtud-01.txt requires pmtu 47 black hole detection. :-( 48 49 It is place to make it. It is not made. I do not want 50 to make it. It is disguisting. It does not work in any 51 case. Let me to cite the same draft, which requires for 52 us to implement this: 53 54 "The one security concern raised by this memo is that ICMP black holes 55 are often caused by over-zealous security administrators who block 56 all ICMP messages. It is vitally important that those who design and 57 deploy security systems understand the impact of strict filtering on 58 upper-layer protocols. The safest web site in the world is worthless 59 if most TCP implementations cannot transfer data from it. It would 60 be far nicer to have all of the black holes fixed rather than fixing 61 all of the TCP implementations." 62 63 Golden words :-). 64 */ 65 66 dst_negative_advice(&sk->sk_dst_cache); 67 } 68 69 retry_until = sysctl_dccp_retries2; 70 /* 71 * FIXME: see tcp_write_timout and tcp_out_of_resources 72 */ 73 } 74 75 if (icsk->icsk_retransmits >= retry_until) { 76 /* Has it gone just too far? */ 77 dccp_write_err(sk); 78 return 1; 79 } 80 return 0; 81 } 82 83 /* 84 * The DCCP retransmit timer. 85 */ 86 static void dccp_retransmit_timer(struct sock *sk) 87 { 88 struct inet_connection_sock *icsk = inet_csk(sk); 89 90 /* retransmit timer is used for feature negotiation throughout 91 * connection. In this case, no packet is re-transmitted, but rather an 92 * ack is generated and pending changes are placed into its options. 93 */ 94 if (sk->sk_send_head == NULL) { 95 dccp_pr_debug("feat negotiation retransmit timeout %p\n", sk); 96 if (sk->sk_state == DCCP_OPEN) 97 dccp_send_ack(sk); 98 goto backoff; 99 } 100 101 /* 102 * sk->sk_send_head has to have one skb with 103 * DCCP_SKB_CB(skb)->dccpd_type set to one of the retransmittable DCCP 104 * packet types. The only packets eligible for retransmission are: 105 * -- Requests in client-REQUEST state (sec. 8.1.1) 106 * -- Acks in client-PARTOPEN state (sec. 8.1.5) 107 * -- CloseReq in server-CLOSEREQ state (sec. 8.3) 108 * -- Close in node-CLOSING state (sec. 8.3) */ 109 BUG_TRAP(sk->sk_send_head != NULL); 110 111 /* 112 * More than than 4MSL (8 minutes) has passed, a RESET(aborted) was 113 * sent, no need to retransmit, this sock is dead. 114 */ 115 if (dccp_write_timeout(sk)) 116 goto out; 117 118 /* 119 * We want to know the number of packets retransmitted, not the 120 * total number of retransmissions of clones of original packets. 121 */ 122 if (icsk->icsk_retransmits == 0) 123 DCCP_INC_STATS_BH(DCCP_MIB_TIMEOUTS); 124 125 if (dccp_retransmit_skb(sk, sk->sk_send_head) < 0) { 126 /* 127 * Retransmission failed because of local congestion, 128 * do not backoff. 129 */ 130 if (icsk->icsk_retransmits == 0) 131 icsk->icsk_retransmits = 1; 132 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 133 min(icsk->icsk_rto, 134 TCP_RESOURCE_PROBE_INTERVAL), 135 DCCP_RTO_MAX); 136 goto out; 137 } 138 139 backoff: 140 icsk->icsk_backoff++; 141 icsk->icsk_retransmits++; 142 143 icsk->icsk_rto = min(icsk->icsk_rto << 1, DCCP_RTO_MAX); 144 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, 145 DCCP_RTO_MAX); 146 if (icsk->icsk_retransmits > sysctl_dccp_retries1) 147 __sk_dst_reset(sk); 148 out:; 149 } 150 151 static void dccp_write_timer(unsigned long data) 152 { 153 struct sock *sk = (struct sock *)data; 154 struct inet_connection_sock *icsk = inet_csk(sk); 155 int event = 0; 156 157 bh_lock_sock(sk); 158 if (sock_owned_by_user(sk)) { 159 /* Try again later */ 160 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, 161 jiffies + (HZ / 20)); 162 goto out; 163 } 164 165 if (sk->sk_state == DCCP_CLOSED || !icsk->icsk_pending) 166 goto out; 167 168 if (time_after(icsk->icsk_timeout, jiffies)) { 169 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, 170 icsk->icsk_timeout); 171 goto out; 172 } 173 174 event = icsk->icsk_pending; 175 icsk->icsk_pending = 0; 176 177 switch (event) { 178 case ICSK_TIME_RETRANS: 179 dccp_retransmit_timer(sk); 180 break; 181 } 182 out: 183 bh_unlock_sock(sk); 184 sock_put(sk); 185 } 186 187 /* 188 * Timer for listening sockets 189 */ 190 static void dccp_response_timer(struct sock *sk) 191 { 192 inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL, DCCP_TIMEOUT_INIT, 193 DCCP_RTO_MAX); 194 } 195 196 static void dccp_keepalive_timer(unsigned long data) 197 { 198 struct sock *sk = (struct sock *)data; 199 200 /* Only process if socket is not in use. */ 201 bh_lock_sock(sk); 202 if (sock_owned_by_user(sk)) { 203 /* Try again later. */ 204 inet_csk_reset_keepalive_timer(sk, HZ / 20); 205 goto out; 206 } 207 208 if (sk->sk_state == DCCP_LISTEN) { 209 dccp_response_timer(sk); 210 goto out; 211 } 212 out: 213 bh_unlock_sock(sk); 214 sock_put(sk); 215 } 216 217 /* This is the same as tcp_delack_timer, sans prequeue & mem_reclaim stuff */ 218 static void dccp_delack_timer(unsigned long data) 219 { 220 struct sock *sk = (struct sock *)data; 221 struct inet_connection_sock *icsk = inet_csk(sk); 222 223 bh_lock_sock(sk); 224 if (sock_owned_by_user(sk)) { 225 /* Try again later. */ 226 icsk->icsk_ack.blocked = 1; 227 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOCKED); 228 sk_reset_timer(sk, &icsk->icsk_delack_timer, 229 jiffies + TCP_DELACK_MIN); 230 goto out; 231 } 232 233 if (sk->sk_state == DCCP_CLOSED || 234 !(icsk->icsk_ack.pending & ICSK_ACK_TIMER)) 235 goto out; 236 if (time_after(icsk->icsk_ack.timeout, jiffies)) { 237 sk_reset_timer(sk, &icsk->icsk_delack_timer, 238 icsk->icsk_ack.timeout); 239 goto out; 240 } 241 242 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER; 243 244 if (inet_csk_ack_scheduled(sk)) { 245 if (!icsk->icsk_ack.pingpong) { 246 /* Delayed ACK missed: inflate ATO. */ 247 icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, 248 icsk->icsk_rto); 249 } else { 250 /* Delayed ACK missed: leave pingpong mode and 251 * deflate ATO. 252 */ 253 icsk->icsk_ack.pingpong = 0; 254 icsk->icsk_ack.ato = TCP_ATO_MIN; 255 } 256 dccp_send_ack(sk); 257 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKS); 258 } 259 out: 260 bh_unlock_sock(sk); 261 sock_put(sk); 262 } 263 264 /* Transmit-delay timer: used by the CCIDs to delay actual send time */ 265 static void dccp_write_xmit_timer(unsigned long data) 266 { 267 struct sock *sk = (struct sock *)data; 268 struct dccp_sock *dp = dccp_sk(sk); 269 270 bh_lock_sock(sk); 271 if (sock_owned_by_user(sk)) 272 sk_reset_timer(sk, &dp->dccps_xmit_timer, jiffies+1); 273 else 274 dccp_write_xmit(sk, 0); 275 bh_unlock_sock(sk); 276 sock_put(sk); 277 } 278 279 static void dccp_init_write_xmit_timer(struct sock *sk) 280 { 281 struct dccp_sock *dp = dccp_sk(sk); 282 283 init_timer(&dp->dccps_xmit_timer); 284 dp->dccps_xmit_timer.data = (unsigned long)sk; 285 dp->dccps_xmit_timer.function = dccp_write_xmit_timer; 286 } 287 288 void dccp_init_xmit_timers(struct sock *sk) 289 { 290 dccp_init_write_xmit_timer(sk); 291 inet_csk_init_xmit_timers(sk, &dccp_write_timer, &dccp_delack_timer, 292 &dccp_keepalive_timer); 293 } 294