timer.c revision 2e2e9e92bd723244ea20fa488b1780111f2b05e1
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 */ 19int sysctl_dccp_request_retries __read_mostly = TCP_SYN_RETRIES; 20int sysctl_dccp_retries1 __read_mostly = TCP_RETR1; 21int sysctl_dccp_retries2 __read_mostly = TCP_RETR2; 22 23static void dccp_write_timer(unsigned long data); 24static void dccp_keepalive_timer(unsigned long data); 25static void dccp_delack_timer(unsigned long data); 26 27void dccp_init_xmit_timers(struct sock *sk) 28{ 29 inet_csk_init_xmit_timers(sk, &dccp_write_timer, &dccp_delack_timer, 30 &dccp_keepalive_timer); 31} 32 33static void dccp_write_err(struct sock *sk) 34{ 35 sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT; 36 sk->sk_error_report(sk); 37 38 dccp_send_reset(sk, DCCP_RESET_CODE_ABORTED); 39 dccp_done(sk); 40 DCCP_INC_STATS_BH(DCCP_MIB_ABORTONTIMEOUT); 41} 42 43/* A write timeout has occurred. Process the after effects. */ 44static int dccp_write_timeout(struct sock *sk) 45{ 46 const struct inet_connection_sock *icsk = inet_csk(sk); 47 int retry_until; 48 49 if (sk->sk_state == DCCP_REQUESTING || sk->sk_state == DCCP_PARTOPEN) { 50 if (icsk->icsk_retransmits != 0) 51 dst_negative_advice(&sk->sk_dst_cache); 52 retry_until = icsk->icsk_syn_retries ? 53 : sysctl_dccp_request_retries; 54 } else { 55 if (icsk->icsk_retransmits >= sysctl_dccp_retries1) { 56 /* NOTE. draft-ietf-tcpimpl-pmtud-01.txt requires pmtu 57 black hole detection. :-( 58 59 It is place to make it. It is not made. I do not want 60 to make it. It is disguisting. It does not work in any 61 case. Let me to cite the same draft, which requires for 62 us to implement this: 63 64 "The one security concern raised by this memo is that ICMP black holes 65 are often caused by over-zealous security administrators who block 66 all ICMP messages. It is vitally important that those who design and 67 deploy security systems understand the impact of strict filtering on 68 upper-layer protocols. The safest web site in the world is worthless 69 if most TCP implementations cannot transfer data from it. It would 70 be far nicer to have all of the black holes fixed rather than fixing 71 all of the TCP implementations." 72 73 Golden words :-). 74 */ 75 76 dst_negative_advice(&sk->sk_dst_cache); 77 } 78 79 retry_until = sysctl_dccp_retries2; 80 /* 81 * FIXME: see tcp_write_timout and tcp_out_of_resources 82 */ 83 } 84 85 if (icsk->icsk_retransmits >= retry_until) { 86 /* Has it gone just too far? */ 87 dccp_write_err(sk); 88 return 1; 89 } 90 return 0; 91} 92 93/* This is the same as tcp_delack_timer, sans prequeue & mem_reclaim stuff */ 94static void dccp_delack_timer(unsigned long data) 95{ 96 struct sock *sk = (struct sock *)data; 97 struct inet_connection_sock *icsk = inet_csk(sk); 98 99 bh_lock_sock(sk); 100 if (sock_owned_by_user(sk)) { 101 /* Try again later. */ 102 icsk->icsk_ack.blocked = 1; 103 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOCKED); 104 sk_reset_timer(sk, &icsk->icsk_delack_timer, 105 jiffies + TCP_DELACK_MIN); 106 goto out; 107 } 108 109 if (sk->sk_state == DCCP_CLOSED || 110 !(icsk->icsk_ack.pending & ICSK_ACK_TIMER)) 111 goto out; 112 if (time_after(icsk->icsk_ack.timeout, jiffies)) { 113 sk_reset_timer(sk, &icsk->icsk_delack_timer, 114 icsk->icsk_ack.timeout); 115 goto out; 116 } 117 118 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER; 119 120 if (inet_csk_ack_scheduled(sk)) { 121 if (!icsk->icsk_ack.pingpong) { 122 /* Delayed ACK missed: inflate ATO. */ 123 icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, 124 icsk->icsk_rto); 125 } else { 126 /* Delayed ACK missed: leave pingpong mode and 127 * deflate ATO. 128 */ 129 icsk->icsk_ack.pingpong = 0; 130 icsk->icsk_ack.ato = TCP_ATO_MIN; 131 } 132 dccp_send_ack(sk); 133 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKS); 134 } 135out: 136 bh_unlock_sock(sk); 137 sock_put(sk); 138} 139 140/* 141 * The DCCP retransmit timer. 142 */ 143static void dccp_retransmit_timer(struct sock *sk) 144{ 145 struct inet_connection_sock *icsk = inet_csk(sk); 146 147 /* retransmit timer is used for feature negotiation throughout 148 * connection. In this case, no packet is re-transmitted, but rather an 149 * ack is generated and pending changes are placed into its options. 150 */ 151 if (sk->sk_send_head == NULL) { 152 dccp_pr_debug("feat negotiation retransmit timeout %p\n", sk); 153 if (sk->sk_state == DCCP_OPEN) 154 dccp_send_ack(sk); 155 goto backoff; 156 } 157 158 /* 159 * sk->sk_send_head has to have one skb with 160 * DCCP_SKB_CB(skb)->dccpd_type set to one of the retransmittable DCCP 161 * packet types. The only packets eligible for retransmission are: 162 * -- Requests in client-REQUEST state (sec. 8.1.1) 163 * -- Acks in client-PARTOPEN state (sec. 8.1.5) 164 * -- CloseReq in server-CLOSEREQ state (sec. 8.3) 165 * -- Close in node-CLOSING state (sec. 8.3) */ 166 BUG_TRAP(sk->sk_send_head != NULL); 167 168 /* 169 * More than than 4MSL (8 minutes) has passed, a RESET(aborted) was 170 * sent, no need to retransmit, this sock is dead. 171 */ 172 if (dccp_write_timeout(sk)) 173 goto out; 174 175 /* 176 * We want to know the number of packets retransmitted, not the 177 * total number of retransmissions of clones of original packets. 178 */ 179 if (icsk->icsk_retransmits == 0) 180 DCCP_INC_STATS_BH(DCCP_MIB_TIMEOUTS); 181 182 if (dccp_retransmit_skb(sk, sk->sk_send_head) < 0) { 183 /* 184 * Retransmission failed because of local congestion, 185 * do not backoff. 186 */ 187 if (icsk->icsk_retransmits == 0) 188 icsk->icsk_retransmits = 1; 189 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 190 min(icsk->icsk_rto, 191 TCP_RESOURCE_PROBE_INTERVAL), 192 DCCP_RTO_MAX); 193 goto out; 194 } 195 196backoff: 197 icsk->icsk_backoff++; 198 icsk->icsk_retransmits++; 199 200 icsk->icsk_rto = min(icsk->icsk_rto << 1, DCCP_RTO_MAX); 201 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, 202 DCCP_RTO_MAX); 203 if (icsk->icsk_retransmits > sysctl_dccp_retries1) 204 __sk_dst_reset(sk); 205out:; 206} 207 208static void dccp_write_timer(unsigned long data) 209{ 210 struct sock *sk = (struct sock *)data; 211 struct inet_connection_sock *icsk = inet_csk(sk); 212 int event = 0; 213 214 bh_lock_sock(sk); 215 if (sock_owned_by_user(sk)) { 216 /* Try again later */ 217 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, 218 jiffies + (HZ / 20)); 219 goto out; 220 } 221 222 if (sk->sk_state == DCCP_CLOSED || !icsk->icsk_pending) 223 goto out; 224 225 if (time_after(icsk->icsk_timeout, jiffies)) { 226 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, 227 icsk->icsk_timeout); 228 goto out; 229 } 230 231 event = icsk->icsk_pending; 232 icsk->icsk_pending = 0; 233 234 switch (event) { 235 case ICSK_TIME_RETRANS: 236 dccp_retransmit_timer(sk); 237 break; 238 } 239out: 240 bh_unlock_sock(sk); 241 sock_put(sk); 242} 243 244/* 245 * Timer for listening sockets 246 */ 247static void dccp_response_timer(struct sock *sk) 248{ 249 inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL, DCCP_TIMEOUT_INIT, 250 DCCP_RTO_MAX); 251} 252 253static void dccp_keepalive_timer(unsigned long data) 254{ 255 struct sock *sk = (struct sock *)data; 256 257 /* Only process if socket is not in use. */ 258 bh_lock_sock(sk); 259 if (sock_owned_by_user(sk)) { 260 /* Try again later. */ 261 inet_csk_reset_keepalive_timer(sk, HZ / 20); 262 goto out; 263 } 264 265 if (sk->sk_state == DCCP_LISTEN) { 266 dccp_response_timer(sk); 267 goto out; 268 } 269out: 270 bh_unlock_sock(sk); 271 sock_put(sk); 272} 273