xref: /openbmc/linux/net/dccp/timer.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
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