1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *  net/dccp/minisocks.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/gfp.h>
11 #include <linux/kernel.h>
12 #include <linux/skbuff.h>
13 #include <linux/timer.h>
14 
15 #include <net/sock.h>
16 #include <net/xfrm.h>
17 #include <net/inet_timewait_sock.h>
18 
19 #include "ackvec.h"
20 #include "ccid.h"
21 #include "dccp.h"
22 #include "feat.h"
23 
24 struct inet_timewait_death_row dccp_death_row = {
25 	.sysctl_max_tw_buckets = NR_FILE * 2,
26 	.hashinfo	= &dccp_hashinfo,
27 };
28 
29 EXPORT_SYMBOL_GPL(dccp_death_row);
30 
dccp_time_wait(struct sock * sk,int state,int timeo)31 void dccp_time_wait(struct sock *sk, int state, int timeo)
32 {
33 	struct inet_timewait_sock *tw;
34 
35 	tw = inet_twsk_alloc(sk, &dccp_death_row, state);
36 
37 	if (tw != NULL) {
38 		const struct inet_connection_sock *icsk = inet_csk(sk);
39 		const int rto = (icsk->icsk_rto << 2) - (icsk->icsk_rto >> 1);
40 #if IS_ENABLED(CONFIG_IPV6)
41 		if (tw->tw_family == PF_INET6) {
42 			tw->tw_v6_daddr = sk->sk_v6_daddr;
43 			tw->tw_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
44 			tw->tw_ipv6only = sk->sk_ipv6only;
45 		}
46 #endif
47 
48 		/* Get the TIME_WAIT timeout firing. */
49 		if (timeo < rto)
50 			timeo = rto;
51 
52 		if (state == DCCP_TIME_WAIT)
53 			timeo = DCCP_TIMEWAIT_LEN;
54 
55 		/* tw_timer is pinned, so we need to make sure BH are disabled
56 		 * in following section, otherwise timer handler could run before
57 		 * we complete the initialization.
58 		 */
59 		local_bh_disable();
60 		inet_twsk_schedule(tw, timeo);
61 		/* Linkage updates.
62 		 * Note that access to tw after this point is illegal.
63 		 */
64 		inet_twsk_hashdance(tw, sk, &dccp_hashinfo);
65 		local_bh_enable();
66 	} else {
67 		/* Sorry, if we're out of memory, just CLOSE this
68 		 * socket up.  We've got bigger problems than
69 		 * non-graceful socket closings.
70 		 */
71 		DCCP_WARN("time wait bucket table overflow\n");
72 	}
73 
74 	dccp_done(sk);
75 }
76 
dccp_create_openreq_child(const struct sock * sk,const struct request_sock * req,const struct sk_buff * skb)77 struct sock *dccp_create_openreq_child(const struct sock *sk,
78 				       const struct request_sock *req,
79 				       const struct sk_buff *skb)
80 {
81 	/*
82 	 * Step 3: Process LISTEN state
83 	 *
84 	 *   (* Generate a new socket and switch to that socket *)
85 	 *   Set S := new socket for this port pair
86 	 */
87 	struct sock *newsk = inet_csk_clone_lock(sk, req, GFP_ATOMIC);
88 
89 	if (newsk != NULL) {
90 		struct dccp_request_sock *dreq = dccp_rsk(req);
91 		struct inet_connection_sock *newicsk = inet_csk(newsk);
92 		struct dccp_sock *newdp = dccp_sk(newsk);
93 
94 		newdp->dccps_role	    = DCCP_ROLE_SERVER;
95 		newdp->dccps_hc_rx_ackvec   = NULL;
96 		newdp->dccps_service_list   = NULL;
97 		newdp->dccps_hc_rx_ccid     = NULL;
98 		newdp->dccps_hc_tx_ccid     = NULL;
99 		newdp->dccps_service	    = dreq->dreq_service;
100 		newdp->dccps_timestamp_echo = dreq->dreq_timestamp_echo;
101 		newdp->dccps_timestamp_time = dreq->dreq_timestamp_time;
102 		newicsk->icsk_rto	    = DCCP_TIMEOUT_INIT;
103 
104 		INIT_LIST_HEAD(&newdp->dccps_featneg);
105 		/*
106 		 * Step 3: Process LISTEN state
107 		 *
108 		 *    Choose S.ISS (initial seqno) or set from Init Cookies
109 		 *    Initialize S.GAR := S.ISS
110 		 *    Set S.ISR, S.GSR from packet (or Init Cookies)
111 		 *
112 		 *    Setting AWL/AWH and SWL/SWH happens as part of the feature
113 		 *    activation below, as these windows all depend on the local
114 		 *    and remote Sequence Window feature values (7.5.2).
115 		 */
116 		newdp->dccps_iss = dreq->dreq_iss;
117 		newdp->dccps_gss = dreq->dreq_gss;
118 		newdp->dccps_gar = newdp->dccps_iss;
119 		newdp->dccps_isr = dreq->dreq_isr;
120 		newdp->dccps_gsr = dreq->dreq_gsr;
121 
122 		/*
123 		 * Activate features: initialise CCIDs, sequence windows etc.
124 		 */
125 		if (dccp_feat_activate_values(newsk, &dreq->dreq_featneg)) {
126 			sk_free_unlock_clone(newsk);
127 			return NULL;
128 		}
129 		dccp_init_xmit_timers(newsk);
130 
131 		__DCCP_INC_STATS(DCCP_MIB_PASSIVEOPENS);
132 	}
133 	return newsk;
134 }
135 
136 EXPORT_SYMBOL_GPL(dccp_create_openreq_child);
137 
138 /*
139  * Process an incoming packet for RESPOND sockets represented
140  * as an request_sock.
141  */
dccp_check_req(struct sock * sk,struct sk_buff * skb,struct request_sock * req)142 struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
143 			    struct request_sock *req)
144 {
145 	struct sock *child = NULL;
146 	struct dccp_request_sock *dreq = dccp_rsk(req);
147 	bool own_req;
148 
149 	/* TCP/DCCP listeners became lockless.
150 	 * DCCP stores complex state in its request_sock, so we need
151 	 * a protection for them, now this code runs without being protected
152 	 * by the parent (listener) lock.
153 	 */
154 	spin_lock_bh(&dreq->dreq_lock);
155 
156 	/* Check for retransmitted REQUEST */
157 	if (dccp_hdr(skb)->dccph_type == DCCP_PKT_REQUEST) {
158 
159 		if (after48(DCCP_SKB_CB(skb)->dccpd_seq, dreq->dreq_gsr)) {
160 			dccp_pr_debug("Retransmitted REQUEST\n");
161 			dreq->dreq_gsr = DCCP_SKB_CB(skb)->dccpd_seq;
162 			/*
163 			 * Send another RESPONSE packet
164 			 * To protect against Request floods, increment retrans
165 			 * counter (backoff, monitored by dccp_response_timer).
166 			 */
167 			inet_rtx_syn_ack(sk, req);
168 		}
169 		/* Network Duplicate, discard packet */
170 		goto out;
171 	}
172 
173 	DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
174 
175 	if (dccp_hdr(skb)->dccph_type != DCCP_PKT_ACK &&
176 	    dccp_hdr(skb)->dccph_type != DCCP_PKT_DATAACK)
177 		goto drop;
178 
179 	/* Invalid ACK */
180 	if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
181 				dreq->dreq_iss, dreq->dreq_gss)) {
182 		dccp_pr_debug("Invalid ACK number: ack_seq=%llu, "
183 			      "dreq_iss=%llu, dreq_gss=%llu\n",
184 			      (unsigned long long)
185 			      DCCP_SKB_CB(skb)->dccpd_ack_seq,
186 			      (unsigned long long) dreq->dreq_iss,
187 			      (unsigned long long) dreq->dreq_gss);
188 		goto drop;
189 	}
190 
191 	if (dccp_parse_options(sk, dreq, skb))
192 		 goto drop;
193 
194 	child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
195 							 req, &own_req);
196 	if (child) {
197 		child = inet_csk_complete_hashdance(sk, child, req, own_req);
198 		goto out;
199 	}
200 
201 	DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
202 drop:
203 	if (dccp_hdr(skb)->dccph_type != DCCP_PKT_RESET)
204 		req->rsk_ops->send_reset(sk, skb);
205 
206 	inet_csk_reqsk_queue_drop(sk, req);
207 out:
208 	spin_unlock_bh(&dreq->dreq_lock);
209 	return child;
210 }
211 
212 EXPORT_SYMBOL_GPL(dccp_check_req);
213 
214 /*
215  *  Queue segment on the new socket if the new socket is active,
216  *  otherwise we just shortcircuit this and continue with
217  *  the new socket.
218  */
dccp_child_process(struct sock * parent,struct sock * child,struct sk_buff * skb)219 int dccp_child_process(struct sock *parent, struct sock *child,
220 		       struct sk_buff *skb)
221 	__releases(child)
222 {
223 	int ret = 0;
224 	const int state = child->sk_state;
225 
226 	if (!sock_owned_by_user(child)) {
227 		ret = dccp_rcv_state_process(child, skb, dccp_hdr(skb),
228 					     skb->len);
229 
230 		/* Wakeup parent, send SIGIO */
231 		if (state == DCCP_RESPOND && child->sk_state != state)
232 			parent->sk_data_ready(parent);
233 	} else {
234 		/* Alas, it is possible again, because we do lookup
235 		 * in main socket hash table and lock on listening
236 		 * socket does not protect us more.
237 		 */
238 		__sk_add_backlog(child, skb);
239 	}
240 
241 	bh_unlock_sock(child);
242 	sock_put(child);
243 	return ret;
244 }
245 
246 EXPORT_SYMBOL_GPL(dccp_child_process);
247 
dccp_reqsk_send_ack(const struct sock * sk,struct sk_buff * skb,struct request_sock * rsk)248 void dccp_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
249 			 struct request_sock *rsk)
250 {
251 	DCCP_BUG("DCCP-ACK packets are never sent in LISTEN/RESPOND state");
252 }
253 
254 EXPORT_SYMBOL_GPL(dccp_reqsk_send_ack);
255 
dccp_reqsk_init(struct request_sock * req,struct dccp_sock const * dp,struct sk_buff const * skb)256 int dccp_reqsk_init(struct request_sock *req,
257 		    struct dccp_sock const *dp, struct sk_buff const *skb)
258 {
259 	struct dccp_request_sock *dreq = dccp_rsk(req);
260 
261 	spin_lock_init(&dreq->dreq_lock);
262 	inet_rsk(req)->ir_rmt_port = dccp_hdr(skb)->dccph_sport;
263 	inet_rsk(req)->ir_num	   = ntohs(dccp_hdr(skb)->dccph_dport);
264 	inet_rsk(req)->acked	   = 0;
265 	dreq->dreq_timestamp_echo  = 0;
266 
267 	/* inherit feature negotiation options from listening socket */
268 	return dccp_feat_clone_list(&dp->dccps_featneg, &dreq->dreq_featneg);
269 }
270 
271 EXPORT_SYMBOL_GPL(dccp_reqsk_init);
272