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1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *  net/dccp/timer.c
4  *
5  *  An implementation of the DCCP protocol
6  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
7  */
8 
9 #include <linux/dccp.h>
10 #include <linux/skbuff.h>
11 #include <linux/export.h>
12 
13 #include "dccp.h"
14 
15 /* sysctl variables governing numbers of retransmission attempts */
16 int  sysctl_dccp_request_retries	__read_mostly = TCP_SYN_RETRIES;
17 int  sysctl_dccp_retries1		__read_mostly = TCP_RETR1;
18 int  sysctl_dccp_retries2		__read_mostly = TCP_RETR2;
19 
dccp_write_err(struct sock * sk)20 static void dccp_write_err(struct sock *sk)
21 {
22 	sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
23 	sk->sk_error_report(sk);
24 
25 	dccp_send_reset(sk, DCCP_RESET_CODE_ABORTED);
26 	dccp_done(sk);
27 	__DCCP_INC_STATS(DCCP_MIB_ABORTONTIMEOUT);
28 }
29 
30 /* A write timeout has occurred. Process the after effects. */
dccp_write_timeout(struct sock * sk)31 static int dccp_write_timeout(struct sock *sk)
32 {
33 	const struct inet_connection_sock *icsk = inet_csk(sk);
34 	int retry_until;
35 
36 	if (sk->sk_state == DCCP_REQUESTING || sk->sk_state == DCCP_PARTOPEN) {
37 		if (icsk->icsk_retransmits != 0)
38 			dst_negative_advice(sk);
39 		retry_until = icsk->icsk_syn_retries ?
40 			    : sysctl_dccp_request_retries;
41 	} else {
42 		if (icsk->icsk_retransmits >= sysctl_dccp_retries1) {
43 			/* NOTE. draft-ietf-tcpimpl-pmtud-01.txt requires pmtu
44 			   black hole detection. :-(
45 
46 			   It is place to make it. It is not made. I do not want
47 			   to make it. It is disguisting. It does not work in any
48 			   case. Let me to cite the same draft, which requires for
49 			   us to implement this:
50 
51    "The one security concern raised by this memo is that ICMP black holes
52    are often caused by over-zealous security administrators who block
53    all ICMP messages.  It is vitally important that those who design and
54    deploy security systems understand the impact of strict filtering on
55    upper-layer protocols.  The safest web site in the world is worthless
56    if most TCP implementations cannot transfer data from it.  It would
57    be far nicer to have all of the black holes fixed rather than fixing
58    all of the TCP implementations."
59 
60 			   Golden words :-).
61 		   */
62 
63 			dst_negative_advice(sk);
64 		}
65 
66 		retry_until = sysctl_dccp_retries2;
67 		/*
68 		 * FIXME: see tcp_write_timout and tcp_out_of_resources
69 		 */
70 	}
71 
72 	if (icsk->icsk_retransmits >= retry_until) {
73 		/* Has it gone just too far? */
74 		dccp_write_err(sk);
75 		return 1;
76 	}
77 	return 0;
78 }
79 
80 /*
81  *	The DCCP retransmit timer.
82  */
dccp_retransmit_timer(struct sock * sk)83 static void dccp_retransmit_timer(struct sock *sk)
84 {
85 	struct inet_connection_sock *icsk = inet_csk(sk);
86 
87 	/*
88 	 * More than 4MSL (8 minutes) has passed, a RESET(aborted) was
89 	 * sent, no need to retransmit, this sock is dead.
90 	 */
91 	if (dccp_write_timeout(sk))
92 		return;
93 
94 	/*
95 	 * We want to know the number of packets retransmitted, not the
96 	 * total number of retransmissions of clones of original packets.
97 	 */
98 	if (icsk->icsk_retransmits == 0)
99 		__DCCP_INC_STATS(DCCP_MIB_TIMEOUTS);
100 
101 	if (dccp_retransmit_skb(sk) != 0) {
102 		/*
103 		 * Retransmission failed because of local congestion,
104 		 * do not backoff.
105 		 */
106 		if (--icsk->icsk_retransmits == 0)
107 			icsk->icsk_retransmits = 1;
108 		inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
109 					  min(icsk->icsk_rto,
110 					      TCP_RESOURCE_PROBE_INTERVAL),
111 					  DCCP_RTO_MAX);
112 		return;
113 	}
114 
115 	icsk->icsk_backoff++;
116 
117 	icsk->icsk_rto = min(icsk->icsk_rto << 1, DCCP_RTO_MAX);
118 	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto,
119 				  DCCP_RTO_MAX);
120 	if (icsk->icsk_retransmits > sysctl_dccp_retries1)
121 		__sk_dst_reset(sk);
122 }
123 
dccp_write_timer(struct timer_list * t)124 static void dccp_write_timer(struct timer_list *t)
125 {
126 	struct inet_connection_sock *icsk =
127 			from_timer(icsk, t, icsk_retransmit_timer);
128 	struct sock *sk = &icsk->icsk_inet.sk;
129 	int event = 0;
130 
131 	bh_lock_sock(sk);
132 	if (sock_owned_by_user(sk)) {
133 		/* Try again later */
134 		sk_reset_timer(sk, &icsk->icsk_retransmit_timer,
135 			       jiffies + (HZ / 20));
136 		goto out;
137 	}
138 
139 	if (sk->sk_state == DCCP_CLOSED || !icsk->icsk_pending)
140 		goto out;
141 
142 	if (time_after(icsk->icsk_timeout, jiffies)) {
143 		sk_reset_timer(sk, &icsk->icsk_retransmit_timer,
144 			       icsk->icsk_timeout);
145 		goto out;
146 	}
147 
148 	event = icsk->icsk_pending;
149 	icsk->icsk_pending = 0;
150 
151 	switch (event) {
152 	case ICSK_TIME_RETRANS:
153 		dccp_retransmit_timer(sk);
154 		break;
155 	}
156 out:
157 	bh_unlock_sock(sk);
158 	sock_put(sk);
159 }
160 
dccp_keepalive_timer(struct timer_list * t)161 static void dccp_keepalive_timer(struct timer_list *t)
162 {
163 	struct sock *sk = from_timer(sk, t, sk_timer);
164 
165 	pr_err("dccp should not use a keepalive timer !\n");
166 	sock_put(sk);
167 }
168 
169 /* This is the same as tcp_delack_timer, sans prequeue & mem_reclaim stuff */
dccp_delack_timer(struct timer_list * t)170 static void dccp_delack_timer(struct timer_list *t)
171 {
172 	struct inet_connection_sock *icsk =
173 			from_timer(icsk, t, icsk_delack_timer);
174 	struct sock *sk = &icsk->icsk_inet.sk;
175 
176 	bh_lock_sock(sk);
177 	if (sock_owned_by_user(sk)) {
178 		/* Try again later. */
179 		__NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
180 		sk_reset_timer(sk, &icsk->icsk_delack_timer,
181 			       jiffies + TCP_DELACK_MIN);
182 		goto out;
183 	}
184 
185 	if (sk->sk_state == DCCP_CLOSED ||
186 	    !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
187 		goto out;
188 	if (time_after(icsk->icsk_ack.timeout, jiffies)) {
189 		sk_reset_timer(sk, &icsk->icsk_delack_timer,
190 			       icsk->icsk_ack.timeout);
191 		goto out;
192 	}
193 
194 	icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
195 
196 	if (inet_csk_ack_scheduled(sk)) {
197 		if (!inet_csk_in_pingpong_mode(sk)) {
198 			/* Delayed ACK missed: inflate ATO. */
199 			icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1,
200 						 icsk->icsk_rto);
201 		} else {
202 			/* Delayed ACK missed: leave pingpong mode and
203 			 * deflate ATO.
204 			 */
205 			inet_csk_exit_pingpong_mode(sk);
206 			icsk->icsk_ack.ato = TCP_ATO_MIN;
207 		}
208 		dccp_send_ack(sk);
209 		__NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS);
210 	}
211 out:
212 	bh_unlock_sock(sk);
213 	sock_put(sk);
214 }
215 
216 /**
217  * dccp_write_xmitlet  -  Workhorse for CCID packet dequeueing interface
218  * @data: Socket to act on
219  *
220  * See the comments above %ccid_dequeueing_decision for supported modes.
221  */
dccp_write_xmitlet(unsigned long data)222 static void dccp_write_xmitlet(unsigned long data)
223 {
224 	struct sock *sk = (struct sock *)data;
225 
226 	bh_lock_sock(sk);
227 	if (sock_owned_by_user(sk))
228 		sk_reset_timer(sk, &dccp_sk(sk)->dccps_xmit_timer, jiffies + 1);
229 	else
230 		dccp_write_xmit(sk);
231 	bh_unlock_sock(sk);
232 	sock_put(sk);
233 }
234 
dccp_write_xmit_timer(struct timer_list * t)235 static void dccp_write_xmit_timer(struct timer_list *t)
236 {
237 	struct dccp_sock *dp = from_timer(dp, t, dccps_xmit_timer);
238 	struct sock *sk = &dp->dccps_inet_connection.icsk_inet.sk;
239 
240 	dccp_write_xmitlet((unsigned long)sk);
241 }
242 
dccp_init_xmit_timers(struct sock * sk)243 void dccp_init_xmit_timers(struct sock *sk)
244 {
245 	struct dccp_sock *dp = dccp_sk(sk);
246 
247 	tasklet_init(&dp->dccps_xmitlet, dccp_write_xmitlet, (unsigned long)sk);
248 	timer_setup(&dp->dccps_xmit_timer, dccp_write_xmit_timer, 0);
249 	inet_csk_init_xmit_timers(sk, &dccp_write_timer, &dccp_delack_timer,
250 				  &dccp_keepalive_timer);
251 }
252 
253 static ktime_t dccp_timestamp_seed;
254 /**
255  * dccp_timestamp  -  10s of microseconds time source
256  * Returns the number of 10s of microseconds since loading DCCP. This is native
257  * DCCP time difference format (RFC 4340, sec. 13).
258  * Please note: This will wrap around about circa every 11.9 hours.
259  */
dccp_timestamp(void)260 u32 dccp_timestamp(void)
261 {
262 	u64 delta = (u64)ktime_us_delta(ktime_get_real(), dccp_timestamp_seed);
263 
264 	do_div(delta, 10);
265 	return delta;
266 }
267 EXPORT_SYMBOL_GPL(dccp_timestamp);
268 
dccp_timestamping_init(void)269 void __init dccp_timestamping_init(void)
270 {
271 	dccp_timestamp_seed = ktime_get_real();
272 }
273