minisocks.c

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/*
 *  net/dccp/minisocks.c
 *
 *  An implementation of the DCCP protocol
 *  Arnaldo Carvalho de Melo <[email protected]>
 *
 *  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);
            struct inet6_timewait_sock *tw6;

            tw->tw_ipv6_offset = inet6_tw_offset(sk->sk_prot);
            tw6 = inet6_twsk((struct sock *)tw);
            tw6->tw_v6_daddr = np->daddr;
            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_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\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).
             */
            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 (!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);
    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!\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 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)->rmt_port   = dccp_hdr(skb)->dccph_sport;
    inet_rsk(req)->loc_port   = 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);