/*
 *  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,
        .hashinfo       = &dccp_hashinfo,
};

EXPORT_SYMBOL_GPL(dccp_death_row);

void dccp_time_wait(struct sock *sk, int state, int timeo)
{
        struct inet_timewait_sock *tw;

        tw = inet_twsk_alloc(sk, &dccp_death_row, 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) {
                        tw->tw_v6_daddr = sk->sk_v6_daddr;
                        tw->tw_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
                        tw->tw_ipv6only = sk->sk_ipv6only;
                }
#endif

                /* Get the TIME_WAIT timeout firing. */
                if (timeo < rto)
                        timeo = rto;

                if (state == DCCP_TIME_WAIT)
                        timeo = DCCP_TIMEWAIT_LEN;

                /* tw_timer is pinned, so we need to make sure BH are disabled
                 * in following section, otherwise timer handler could run before
                 * we complete the initialization.
                 */
                local_bh_disable();
                inet_twsk_schedule(tw, timeo);
                /* Linkage updates.
                 * Note that access to tw after this point is illegal.
                 */
                inet_twsk_hashdance(tw, sk, &dccp_hashinfo);
                local_bh_enable();
        } 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(const 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)) {
                        sk_free_unlock_clone(newsk);
                        return NULL;
                }
                dccp_init_xmit_timers(newsk);

                __DCCP_INC_STATS(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 sock *child = NULL;
        struct dccp_request_sock *dreq = dccp_rsk(req);
        bool own_req;

        /* TCP/DCCP listeners became lockless.
         * DCCP stores complex state in its request_sock, so we need
         * a protection for them, now this code runs without being protected
         * by the parent (listener) lock.
         */
        spin_lock_bh(&dreq->dreq_lock);

        /* 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\n");
                        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 */
                goto out;
        }

        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\n",
                              (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,
                                                         req, &own_req);
        if (child) {
                child = inet_csk_complete_hashdance(sk, child, req, own_req);
                goto out;
        }

        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);
out:
        spin_unlock_bh(&dreq->dreq_lock);
        return child;
}

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);
        } 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(const 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);

        spin_lock_init(&dreq->dreq_lock);
        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);