/*
 *  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/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_minisock_init(struct dccp_minisock *dmsk)
{
        dmsk->dccpms_sequence_window = sysctl_dccp_feat_sequence_window;
        dmsk->dccpms_rx_ccid         = sysctl_dccp_feat_rx_ccid;
        dmsk->dccpms_tx_ccid         = sysctl_dccp_feat_tx_ccid;
        dmsk->dccpms_ack_ratio       = sysctl_dccp_feat_ack_ratio;
        dmsk->dccpms_send_ack_vector = sysctl_dccp_feat_send_ack_vector;
        dmsk->dccpms_send_ndp_count  = sysctl_dccp_feat_send_ndp_count;
}

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 defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
                if (tw->tw_family == PF_INET6) {
                        const struct ipv6_pinfo *np = inet6_sk(sk);
                        struct inet6_timewait_sock *tw6;

                        tw->tw_ipv6_offset = inet6_tw_offset(sk->sk_prot);
                        tw6 = inet6_twsk((struct sock *)tw);
                        ipv6_addr_copy(&tw6->tw_v6_daddr, &np->daddr);
                        ipv6_addr_copy(&tw6->tw_v6_rcv_saddr, &np->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\n");
        }

        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(sk, req, GFP_ATOMIC);

        if (newsk != NULL) {
                const struct dccp_request_sock *dreq = dccp_rsk(req);
                struct inet_connection_sock *newicsk = inet_csk(newsk);
                struct dccp_sock *newdp = dccp_sk(newsk);
                struct dccp_minisock *newdmsk = dccp_msk(newsk);

                newdp->dccps_role          = DCCP_ROLE_SERVER;
                newdp->dccps_hc_rx_ackvec  = NULL;
                newdp->dccps_service_list  = NULL;
                newdp->dccps_service       = dreq->dreq_service;
                newicsk->icsk_rto          = DCCP_TIMEOUT_INIT;

                if (dccp_feat_clone(sk, newsk))
                        goto out_free;

                if (newdmsk->dccpms_send_ack_vector) {
                        newdp->dccps_hc_rx_ackvec =
                                                dccp_ackvec_alloc(GFP_ATOMIC);
                        if (unlikely(newdp->dccps_hc_rx_ackvec == NULL))
                                goto out_free;
                }

                newdp->dccps_hc_rx_ccid =
                            ccid_hc_rx_new(newdmsk->dccpms_rx_ccid,
                                           newsk, GFP_ATOMIC);
                newdp->dccps_hc_tx_ccid =
                            ccid_hc_tx_new(newdmsk->dccpms_tx_ccid,
                                           newsk, GFP_ATOMIC);
                if (unlikely(newdp->dccps_hc_rx_ccid == NULL ||
                             newdp->dccps_hc_tx_ccid == NULL)) {
                        dccp_ackvec_free(newdp->dccps_hc_rx_ackvec);
                        ccid_hc_rx_delete(newdp->dccps_hc_rx_ccid, newsk);
                        ccid_hc_tx_delete(newdp->dccps_hc_tx_ccid, newsk);
out_free:
                        /* It is still raw copy of parent, so invalidate
                         * destructor and make plain sk_free() */
                        newsk->sk_destruct = NULL;
                        sk_free(newsk);
                        return NULL;
                }

                /*
                 * 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, S.SWL, S.SWH from packet or Init Cookies
                 */

                /* See dccp_v4_conn_request */
                newdmsk->dccpms_sequence_window = req->rcv_wnd;

                newdp->dccps_gar = newdp->dccps_isr = dreq->dreq_isr;
                dccp_update_gsr(newsk, dreq->dreq_isr);

                newdp->dccps_iss = dreq->dreq_iss;
                dccp_update_gss(newsk, dreq->dreq_iss);

                /*
                 * SWL and AWL are initially adjusted so that they are not less than
                 * the initial Sequence Numbers received and sent, respectively:
                 *      SWL := max(GSR + 1 - floor(W/4), ISR),
                 *      AWL := max(GSS - W' + 1, ISS).
                 * These adjustments MUST be applied only at the beginning of the
                 * connection.
                 */
                dccp_set_seqno(&newdp->dccps_swl,
                               max48(newdp->dccps_swl, newdp->dccps_isr));
                dccp_set_seqno(&newdp->dccps_awl,
                               max48(newdp->dccps_awl, newdp->dccps_iss));

                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;

        /* Check for retransmitted REQUEST */
        if (dccp_hdr(skb)->dccph_type == DCCP_PKT_REQUEST) {
                struct dccp_request_sock *dreq = dccp_rsk(req);

                if (after48(DCCP_SKB_CB(skb)->dccpd_seq, dreq->dreq_isr)) {
                        dccp_pr_debug("Retransmitted REQUEST\n");
                        dreq->dreq_isr = DCCP_SKB_CB(skb)->dccpd_seq;
                        /*
                         * Send another RESPONSE packet
                         * To protect against Request floods, increment retrans
                         * counter (backoff, monitored by dccp_response_timer).
                         */
                        req->retrans++;
                        req->rsk_ops->rtx_syn_ack(sk, req, NULL);
                }
                /* 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 (DCCP_SKB_CB(skb)->dccpd_ack_seq != dccp_rsk(req)->dreq_iss) {
                dccp_pr_debug("Invalid ACK number: ack_seq=%llu, "
                              "dreq_iss=%llu\n",
                              (unsigned long long)
                              DCCP_SKB_CB(skb)->dccpd_ack_seq,
                              (unsigned long long)
                              dccp_rsk(req)->dreq_iss);
                goto drop;
        }

        child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL);
        if (child == NULL)
                goto listen_overflow;

        /* FIXME: deal with options */

        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!\n");
        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 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);

void dccp_reqsk_init(struct request_sock *req, struct sk_buff *skb)
{
        inet_rsk(req)->rmt_port = dccp_hdr(skb)->dccph_sport;
        inet_rsk(req)->acked    = 0;
        req->rcv_wnd            = sysctl_dccp_feat_sequence_window;
}

EXPORT_SYMBOL_GPL(dccp_reqsk_init);