/*
   *  net/dccp/minisocks.c
   *
   *  An implementation of the DCCP protocol
   *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   *
   *	This program is free software; you can redistribute it and/or
   *	modify it under the terms of the GNU General Public License
   *	as published by the Free Software Foundation; either version
   *	2 of the License, or (at your option) any later version.
   */
  
  #include <linux/dccp.h>
  #include <linux/gfp.h>
  #include <linux/kernel.h>
  #include <linux/skbuff.h>
  #include <linux/timer.h>
  
  #include <net/sock.h>
  #include <net/xfrm.h>
  #include <net/inet_timewait_sock.h>
  
  #include "ackvec.h"
  #include "ccid.h"
  #include "dccp.h"
  #include "feat.h"
  
  struct inet_timewait_death_row dccp_death_row = {
  	.sysctl_max_tw_buckets = NR_FILE * 2,
  	.period		= DCCP_TIMEWAIT_LEN / INET_TWDR_TWKILL_SLOTS,
  	.death_lock	= __SPIN_LOCK_UNLOCKED(dccp_death_row.death_lock),
  	.hashinfo	= &dccp_hashinfo,
  	.tw_timer	= TIMER_INITIALIZER(inet_twdr_hangman, 0,
  					    (unsigned long)&dccp_death_row),
  	.twkill_work	= __WORK_INITIALIZER(dccp_death_row.twkill_work,
  					     inet_twdr_twkill_work),
  /* Short-time timewait calendar */
  
  	.twcal_hand	= -1,
  	.twcal_timer	= TIMER_INITIALIZER(inet_twdr_twcal_tick, 0,
  					    (unsigned long)&dccp_death_row),
  };
  
  EXPORT_SYMBOL_GPL(dccp_death_row);
  
  void dccp_time_wait(struct sock *sk, int state, int timeo)
  {
  	struct inet_timewait_sock *tw = NULL;
  
  	if (dccp_death_row.tw_count < dccp_death_row.sysctl_max_tw_buckets)
  		tw = inet_twsk_alloc(sk, state);
  
  	if (tw != NULL) {
  		const struct inet_connection_sock *icsk = inet_csk(sk);
  		const int rto = (icsk->icsk_rto << 2) - (icsk->icsk_rto >> 1);
  #if IS_ENABLED(CONFIG_IPV6)
  		if (tw->tw_family == PF_INET6) {
  			const struct ipv6_pinfo *np = inet6_sk(sk);
  
  			tw->tw_v6_daddr = sk->sk_v6_daddr;
  			tw->tw_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
  			tw->tw_ipv6only = np->ipv6only;
  		}
  #endif
  		/* Linkage updates. */
  		__inet_twsk_hashdance(tw, sk, &dccp_hashinfo);
  
  		/* Get the TIME_WAIT timeout firing. */
  		if (timeo < rto)
  			timeo = rto;
  
  		tw->tw_timeout = DCCP_TIMEWAIT_LEN;
  		if (state == DCCP_TIME_WAIT)
  			timeo = DCCP_TIMEWAIT_LEN;
  
  		inet_twsk_schedule(tw, &dccp_death_row, timeo,
  				   DCCP_TIMEWAIT_LEN);
  		inet_twsk_put(tw);
  	} else {
  		/* Sorry, if we're out of memory, just CLOSE this
  		 * socket up.  We've got bigger problems than
  		 * non-graceful socket closings.
  		 */
  		DCCP_WARN("time wait bucket table overflow
  ");
  	}
  
  	dccp_done(sk);
  }
  
  struct sock *dccp_create_openreq_child(struct sock *sk,
  				       const struct request_sock *req,
  				       const struct sk_buff *skb)
  {
  	/*
  	 * Step 3: Process LISTEN state
  	 *
  	 *   (* Generate a new socket and switch to that socket *)
  	 *   Set S := new socket for this port pair
  	 */
  	struct sock *newsk = inet_csk_clone_lock(sk, req, GFP_ATOMIC);
  
  	if (newsk != NULL) {
  		struct dccp_request_sock *dreq = dccp_rsk(req);
  		struct inet_connection_sock *newicsk = inet_csk(newsk);
  		struct dccp_sock *newdp = dccp_sk(newsk);
  
  		newdp->dccps_role	    = DCCP_ROLE_SERVER;
  		newdp->dccps_hc_rx_ackvec   = NULL;
  		newdp->dccps_service_list   = NULL;
  		newdp->dccps_service	    = dreq->dreq_service;
  		newdp->dccps_timestamp_echo = dreq->dreq_timestamp_echo;
  		newdp->dccps_timestamp_time = dreq->dreq_timestamp_time;
  		newicsk->icsk_rto	    = DCCP_TIMEOUT_INIT;
  
  		INIT_LIST_HEAD(&newdp->dccps_featneg);
  		/*
  		 * Step 3: Process LISTEN state
  		 *
  		 *    Choose S.ISS (initial seqno) or set from Init Cookies
  		 *    Initialize S.GAR := S.ISS
  		 *    Set S.ISR, S.GSR from packet (or Init Cookies)
  		 *
  		 *    Setting AWL/AWH and SWL/SWH happens as part of the feature
  		 *    activation below, as these windows all depend on the local
  		 *    and remote Sequence Window feature values (7.5.2).
  		 */
  		newdp->dccps_iss = dreq->dreq_iss;
  		newdp->dccps_gss = dreq->dreq_gss;
  		newdp->dccps_gar = newdp->dccps_iss;
  		newdp->dccps_isr = dreq->dreq_isr;
  		newdp->dccps_gsr = dreq->dreq_gsr;
  
  		/*
  		 * Activate features: initialise CCIDs, sequence windows etc.
  		 */
  		if (dccp_feat_activate_values(newsk, &dreq->dreq_featneg)) {
  			/* It is still raw copy of parent, so invalidate
  			 * destructor and make plain sk_free() */
  			newsk->sk_destruct = NULL;
  			sk_free(newsk);
  			return NULL;
  		}
  		dccp_init_xmit_timers(newsk);
  
  		DCCP_INC_STATS_BH(DCCP_MIB_PASSIVEOPENS);
  	}
  	return newsk;
  }
  
  EXPORT_SYMBOL_GPL(dccp_create_openreq_child);
  
  /*
   * Process an incoming packet for RESPOND sockets represented
   * as an request_sock.
   */
  struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
  			    struct request_sock *req,
  			    struct request_sock **prev)
  {
  	struct sock *child = NULL;
  	struct dccp_request_sock *dreq = dccp_rsk(req);
  
  	/* Check for retransmitted REQUEST */
  	if (dccp_hdr(skb)->dccph_type == DCCP_PKT_REQUEST) {
  
  		if (after48(DCCP_SKB_CB(skb)->dccpd_seq, dreq->dreq_gsr)) {
  			dccp_pr_debug("Retransmitted REQUEST
  ");
  			dreq->dreq_gsr = DCCP_SKB_CB(skb)->dccpd_seq;
  			/*
  			 * Send another RESPONSE packet
  			 * To protect against Request floods, increment retrans
  			 * counter (backoff, monitored by dccp_response_timer).
  			 */
  			inet_rtx_syn_ack(sk, req);
  		}
  		/* Network Duplicate, discard packet */
  		return NULL;
  	}
  
  	DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
  
  	if (dccp_hdr(skb)->dccph_type != DCCP_PKT_ACK &&
  	    dccp_hdr(skb)->dccph_type != DCCP_PKT_DATAACK)
  		goto drop;
  
  	/* Invalid ACK */
  	if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
  				dreq->dreq_iss, dreq->dreq_gss)) {
  		dccp_pr_debug("Invalid ACK number: ack_seq=%llu, "
  			      "dreq_iss=%llu, dreq_gss=%llu
  ",
  			      (unsigned long long)
  			      DCCP_SKB_CB(skb)->dccpd_ack_seq,
  			      (unsigned long long) dreq->dreq_iss,
  			      (unsigned long long) dreq->dreq_gss);
  		goto drop;
  	}
  
  	if (dccp_parse_options(sk, dreq, skb))
  		 goto drop;
  
  	child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL);
  	if (child == NULL)
  		goto listen_overflow;
  
  	inet_csk_reqsk_queue_unlink(sk, req, prev);
  	inet_csk_reqsk_queue_removed(sk, req);
  	inet_csk_reqsk_queue_add(sk, req, child);
  out:
  	return child;
  listen_overflow:
  	dccp_pr_debug("listen_overflow!
  ");
  	DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
  drop:
  	if (dccp_hdr(skb)->dccph_type != DCCP_PKT_RESET)
  		req->rsk_ops->send_reset(sk, skb);
  
  	inet_csk_reqsk_queue_drop(sk, req, prev);
  	goto out;
  }
  
  EXPORT_SYMBOL_GPL(dccp_check_req);
  
  /*
   *  Queue segment on the new socket if the new socket is active,
   *  otherwise we just shortcircuit this and continue with
   *  the new socket.
   */
  int dccp_child_process(struct sock *parent, struct sock *child,
  		       struct sk_buff *skb)
  {
  	int ret = 0;
  	const int state = child->sk_state;
  
  	if (!sock_owned_by_user(child)) {
  		ret = dccp_rcv_state_process(child, skb, dccp_hdr(skb),
  					     skb->len);
  
  		/* Wakeup parent, send SIGIO */
  		if (state == DCCP_RESPOND && child->sk_state != state)
  			parent->sk_data_ready(parent, 0);
  	} else {
  		/* Alas, it is possible again, because we do lookup
  		 * in main socket hash table and lock on listening
  		 * socket does not protect us more.
  		 */
  		__sk_add_backlog(child, skb);
  	}
  
  	bh_unlock_sock(child);
  	sock_put(child);
  	return ret;
  }
  
  EXPORT_SYMBOL_GPL(dccp_child_process);
  
  void dccp_reqsk_send_ack(struct sock *sk, struct sk_buff *skb,
  			 struct request_sock *rsk)
  {
  	DCCP_BUG("DCCP-ACK packets are never sent in LISTEN/RESPOND state");
  }
  
  EXPORT_SYMBOL_GPL(dccp_reqsk_send_ack);
  
  int dccp_reqsk_init(struct request_sock *req,
  		    struct dccp_sock const *dp, struct sk_buff const *skb)
  {
  	struct dccp_request_sock *dreq = dccp_rsk(req);
  
  	inet_rsk(req)->ir_rmt_port = dccp_hdr(skb)->dccph_sport;
  	inet_rsk(req)->ir_num	   = ntohs(dccp_hdr(skb)->dccph_dport);
  	inet_rsk(req)->acked	   = 0;
  	dreq->dreq_timestamp_echo  = 0;
  
  	/* inherit feature negotiation options from listening socket */
  	return dccp_feat_clone_list(&dp->dccps_featneg, &dreq->dreq_featneg);
  }
  
  EXPORT_SYMBOL_GPL(dccp_reqsk_init);