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1 /*
2  *  net/dccp/minisocks.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/gfp.h>
15 #include <linux/kernel.h>
16 #include <linux/skbuff.h>
17 #include <linux/timer.h>
18 
19 #include <net/sock.h>
20 #include <net/xfrm.h>
21 #include <net/inet_timewait_sock.h>
22 
23 #include "ackvec.h"
24 #include "ccid.h"
25 #include "dccp.h"
26 #include "feat.h"
27 
28 struct inet_timewait_death_row dccp_death_row = {
29 	.sysctl_max_tw_buckets = NR_FILE * 2,
30 	.hashinfo	= &dccp_hashinfo,
31 };
32 
33 EXPORT_SYMBOL_GPL(dccp_death_row);
34 
dccp_time_wait(struct sock * sk,int state,int timeo)35 void dccp_time_wait(struct sock *sk, int state, int timeo)
36 {
37 	struct inet_timewait_sock *tw;
38 
39 	tw = inet_twsk_alloc(sk, &dccp_death_row, state);
40 
41 	if (tw != NULL) {
42 		const struct inet_connection_sock *icsk = inet_csk(sk);
43 		const int rto = (icsk->icsk_rto << 2) - (icsk->icsk_rto >> 1);
44 #if IS_ENABLED(CONFIG_IPV6)
45 		if (tw->tw_family == PF_INET6) {
46 			tw->tw_v6_daddr = sk->sk_v6_daddr;
47 			tw->tw_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
48 			tw->tw_ipv6only = sk->sk_ipv6only;
49 		}
50 #endif
51 
52 		/* Get the TIME_WAIT timeout firing. */
53 		if (timeo < rto)
54 			timeo = rto;
55 
56 		if (state == DCCP_TIME_WAIT)
57 			timeo = DCCP_TIMEWAIT_LEN;
58 
59 		/* tw_timer is pinned, so we need to make sure BH are disabled
60 		 * in following section, otherwise timer handler could run before
61 		 * we complete the initialization.
62 		 */
63 		local_bh_disable();
64 		inet_twsk_schedule(tw, timeo);
65 		/* Linkage updates.
66 		 * Note that access to tw after this point is illegal.
67 		 */
68 		inet_twsk_hashdance(tw, sk, &dccp_hashinfo);
69 		local_bh_enable();
70 	} else {
71 		/* Sorry, if we're out of memory, just CLOSE this
72 		 * socket up.  We've got bigger problems than
73 		 * non-graceful socket closings.
74 		 */
75 		DCCP_WARN("time wait bucket table overflow\n");
76 	}
77 
78 	dccp_done(sk);
79 }
80 
dccp_create_openreq_child(const struct sock * sk,const struct request_sock * req,const struct sk_buff * skb)81 struct sock *dccp_create_openreq_child(const struct sock *sk,
82 				       const struct request_sock *req,
83 				       const struct sk_buff *skb)
84 {
85 	/*
86 	 * Step 3: Process LISTEN state
87 	 *
88 	 *   (* Generate a new socket and switch to that socket *)
89 	 *   Set S := new socket for this port pair
90 	 */
91 	struct sock *newsk = inet_csk_clone_lock(sk, req, GFP_ATOMIC);
92 
93 	if (newsk != NULL) {
94 		struct dccp_request_sock *dreq = dccp_rsk(req);
95 		struct inet_connection_sock *newicsk = inet_csk(newsk);
96 		struct dccp_sock *newdp = dccp_sk(newsk);
97 
98 		newdp->dccps_role	    = DCCP_ROLE_SERVER;
99 		newdp->dccps_hc_rx_ackvec   = NULL;
100 		newdp->dccps_service_list   = NULL;
101 		newdp->dccps_hc_rx_ccid     = NULL;
102 		newdp->dccps_hc_tx_ccid     = NULL;
103 		newdp->dccps_service	    = dreq->dreq_service;
104 		newdp->dccps_timestamp_echo = dreq->dreq_timestamp_echo;
105 		newdp->dccps_timestamp_time = dreq->dreq_timestamp_time;
106 		newicsk->icsk_rto	    = DCCP_TIMEOUT_INIT;
107 
108 		INIT_LIST_HEAD(&newdp->dccps_featneg);
109 		/*
110 		 * Step 3: Process LISTEN state
111 		 *
112 		 *    Choose S.ISS (initial seqno) or set from Init Cookies
113 		 *    Initialize S.GAR := S.ISS
114 		 *    Set S.ISR, S.GSR from packet (or Init Cookies)
115 		 *
116 		 *    Setting AWL/AWH and SWL/SWH happens as part of the feature
117 		 *    activation below, as these windows all depend on the local
118 		 *    and remote Sequence Window feature values (7.5.2).
119 		 */
120 		newdp->dccps_iss = dreq->dreq_iss;
121 		newdp->dccps_gss = dreq->dreq_gss;
122 		newdp->dccps_gar = newdp->dccps_iss;
123 		newdp->dccps_isr = dreq->dreq_isr;
124 		newdp->dccps_gsr = dreq->dreq_gsr;
125 
126 		/*
127 		 * Activate features: initialise CCIDs, sequence windows etc.
128 		 */
129 		if (dccp_feat_activate_values(newsk, &dreq->dreq_featneg)) {
130 			sk_free_unlock_clone(newsk);
131 			return NULL;
132 		}
133 		dccp_init_xmit_timers(newsk);
134 
135 		__DCCP_INC_STATS(DCCP_MIB_PASSIVEOPENS);
136 	}
137 	return newsk;
138 }
139 
140 EXPORT_SYMBOL_GPL(dccp_create_openreq_child);
141 
142 /*
143  * Process an incoming packet for RESPOND sockets represented
144  * as an request_sock.
145  */
dccp_check_req(struct sock * sk,struct sk_buff * skb,struct request_sock * req)146 struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
147 			    struct request_sock *req)
148 {
149 	struct sock *child = NULL;
150 	struct dccp_request_sock *dreq = dccp_rsk(req);
151 	bool own_req;
152 
153 	/* TCP/DCCP listeners became lockless.
154 	 * DCCP stores complex state in its request_sock, so we need
155 	 * a protection for them, now this code runs without being protected
156 	 * by the parent (listener) lock.
157 	 */
158 	spin_lock_bh(&dreq->dreq_lock);
159 
160 	/* Check for retransmitted REQUEST */
161 	if (dccp_hdr(skb)->dccph_type == DCCP_PKT_REQUEST) {
162 
163 		if (after48(DCCP_SKB_CB(skb)->dccpd_seq, dreq->dreq_gsr)) {
164 			dccp_pr_debug("Retransmitted REQUEST\n");
165 			dreq->dreq_gsr = DCCP_SKB_CB(skb)->dccpd_seq;
166 			/*
167 			 * Send another RESPONSE packet
168 			 * To protect against Request floods, increment retrans
169 			 * counter (backoff, monitored by dccp_response_timer).
170 			 */
171 			inet_rtx_syn_ack(sk, req);
172 		}
173 		/* Network Duplicate, discard packet */
174 		goto out;
175 	}
176 
177 	DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
178 
179 	if (dccp_hdr(skb)->dccph_type != DCCP_PKT_ACK &&
180 	    dccp_hdr(skb)->dccph_type != DCCP_PKT_DATAACK)
181 		goto drop;
182 
183 	/* Invalid ACK */
184 	if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
185 				dreq->dreq_iss, dreq->dreq_gss)) {
186 		dccp_pr_debug("Invalid ACK number: ack_seq=%llu, "
187 			      "dreq_iss=%llu, dreq_gss=%llu\n",
188 			      (unsigned long long)
189 			      DCCP_SKB_CB(skb)->dccpd_ack_seq,
190 			      (unsigned long long) dreq->dreq_iss,
191 			      (unsigned long long) dreq->dreq_gss);
192 		goto drop;
193 	}
194 
195 	if (dccp_parse_options(sk, dreq, skb))
196 		 goto drop;
197 
198 	child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
199 							 req, &own_req);
200 	if (child) {
201 		child = inet_csk_complete_hashdance(sk, child, req, own_req);
202 		goto out;
203 	}
204 
205 	DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
206 drop:
207 	if (dccp_hdr(skb)->dccph_type != DCCP_PKT_RESET)
208 		req->rsk_ops->send_reset(sk, skb);
209 
210 	inet_csk_reqsk_queue_drop(sk, req);
211 out:
212 	spin_unlock_bh(&dreq->dreq_lock);
213 	return child;
214 }
215 
216 EXPORT_SYMBOL_GPL(dccp_check_req);
217 
218 /*
219  *  Queue segment on the new socket if the new socket is active,
220  *  otherwise we just shortcircuit this and continue with
221  *  the new socket.
222  */
dccp_child_process(struct sock * parent,struct sock * child,struct sk_buff * skb)223 int dccp_child_process(struct sock *parent, struct sock *child,
224 		       struct sk_buff *skb)
225 {
226 	int ret = 0;
227 	const int state = child->sk_state;
228 
229 	if (!sock_owned_by_user(child)) {
230 		ret = dccp_rcv_state_process(child, skb, dccp_hdr(skb),
231 					     skb->len);
232 
233 		/* Wakeup parent, send SIGIO */
234 		if (state == DCCP_RESPOND && child->sk_state != state)
235 			parent->sk_data_ready(parent);
236 	} else {
237 		/* Alas, it is possible again, because we do lookup
238 		 * in main socket hash table and lock on listening
239 		 * socket does not protect us more.
240 		 */
241 		__sk_add_backlog(child, skb);
242 	}
243 
244 	bh_unlock_sock(child);
245 	sock_put(child);
246 	return ret;
247 }
248 
249 EXPORT_SYMBOL_GPL(dccp_child_process);
250 
dccp_reqsk_send_ack(const struct sock * sk,struct sk_buff * skb,struct request_sock * rsk)251 void dccp_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
252 			 struct request_sock *rsk)
253 {
254 	DCCP_BUG("DCCP-ACK packets are never sent in LISTEN/RESPOND state");
255 }
256 
257 EXPORT_SYMBOL_GPL(dccp_reqsk_send_ack);
258 
dccp_reqsk_init(struct request_sock * req,struct dccp_sock const * dp,struct sk_buff const * skb)259 int dccp_reqsk_init(struct request_sock *req,
260 		    struct dccp_sock const *dp, struct sk_buff const *skb)
261 {
262 	struct dccp_request_sock *dreq = dccp_rsk(req);
263 
264 	spin_lock_init(&dreq->dreq_lock);
265 	inet_rsk(req)->ir_rmt_port = dccp_hdr(skb)->dccph_sport;
266 	inet_rsk(req)->ir_num	   = ntohs(dccp_hdr(skb)->dccph_dport);
267 	inet_rsk(req)->acked	   = 0;
268 	dreq->dreq_timestamp_echo  = 0;
269 
270 	/* inherit feature negotiation options from listening socket */
271 	return dccp_feat_clone_list(&dp->dccps_featneg, &dreq->dreq_featneg);
272 }
273 
274 EXPORT_SYMBOL_GPL(dccp_reqsk_init);
275