[PATCH] g_file_storage: fix obscure race condition

[linux/fpc-iii.git] / net / dccp / input.c

/*
 *  net/dccp/input.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/config.h>
#include <linux/dccp.h>
#include <linux/skbuff.h>

#include <net/sock.h>

#include "ackvec.h"
#include "ccid.h"
#include "dccp.h"

static void dccp_fin(struct sock *sk, struct sk_buff *skb)
{
        sk->sk_shutdown |= RCV_SHUTDOWN;
        sock_set_flag(sk, SOCK_DONE);
        __skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
        __skb_queue_tail(&sk->sk_receive_queue, skb);
        skb_set_owner_r(skb, sk);
        sk->sk_data_ready(sk, 0);
}

static void dccp_rcv_close(struct sock *sk, struct sk_buff *skb)
{
        dccp_v4_send_reset(sk, DCCP_RESET_CODE_CLOSED);
        dccp_fin(sk, skb);
        dccp_set_state(sk, DCCP_CLOSED);
        sk_wake_async(sk, 1, POLL_HUP);
}

static void dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
{
        /*
         *   Step 7: Check for unexpected packet types
         *      If (S.is_server and P.type == CloseReq)
         *        Send Sync packet acknowledging P.seqno
         *        Drop packet and return
         */
        if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT) {
                dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
                return;
        }

        if (sk->sk_state != DCCP_CLOSING)
                dccp_set_state(sk, DCCP_CLOSING);
        dccp_send_close(sk, 0);
}

static inline void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
{
        struct dccp_sock *dp = dccp_sk(sk);

        if (dp->dccps_options.dccpo_send_ack_vector)
                dccp_ackvec_check_rcv_ackno(dp->dccps_hc_rx_ackvec, sk,
                                            DCCP_SKB_CB(skb)->dccpd_ack_seq);
}

static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
{
        const struct dccp_hdr *dh = dccp_hdr(skb);
        struct dccp_sock *dp = dccp_sk(sk);
        u64 lswl, lawl;

        /*
         *   Step 5: Prepare sequence numbers for Sync
         *     If P.type == Sync or P.type == SyncAck,
         *        If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
         *           / * P is valid, so update sequence number variables
         *               accordingly.  After this update, P will pass the tests
         *               in Step 6.  A SyncAck is generated if necessary in
         *               Step 15 * /
         *           Update S.GSR, S.SWL, S.SWH
         *        Otherwise,
         *           Drop packet and return
         */
        if (dh->dccph_type == DCCP_PKT_SYNC || 
            dh->dccph_type == DCCP_PKT_SYNCACK) {
                if (between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
                              dp->dccps_awl, dp->dccps_awh) &&
                    !before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_swl))
                        dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
                else
                        return -1;
        }
        
        /*
         *   Step 6: Check sequence numbers
         *      Let LSWL = S.SWL and LAWL = S.AWL
         *      If P.type == CloseReq or P.type == Close or P.type == Reset,
         *        LSWL := S.GSR + 1, LAWL := S.GAR
         *      If LSWL <= P.seqno <= S.SWH
         *           and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
         *        Update S.GSR, S.SWL, S.SWH
         *        If P.type != Sync,
         *           Update S.GAR
         *      Otherwise,
         *        Send Sync packet acknowledging P.seqno
         *        Drop packet and return
         */
        lswl = dp->dccps_swl;
        lawl = dp->dccps_awl;

        if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
            dh->dccph_type == DCCP_PKT_CLOSE ||
            dh->dccph_type == DCCP_PKT_RESET) {
                lswl = dp->dccps_gsr;
                dccp_inc_seqno(&lswl);
                lawl = dp->dccps_gar;
        }

        if (between48(DCCP_SKB_CB(skb)->dccpd_seq, lswl, dp->dccps_swh) &&
            (DCCP_SKB_CB(skb)->dccpd_ack_seq == DCCP_PKT_WITHOUT_ACK_SEQ ||
             between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
                       lawl, dp->dccps_awh))) {
                dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);

                if (dh->dccph_type != DCCP_PKT_SYNC &&
                    (DCCP_SKB_CB(skb)->dccpd_ack_seq !=
                     DCCP_PKT_WITHOUT_ACK_SEQ))
                        dp->dccps_gar = DCCP_SKB_CB(skb)->dccpd_ack_seq;
        } else {
                LIMIT_NETDEBUG(KERN_WARNING "DCCP: Step 6 failed for %s packet, "
                                            "(LSWL(%llu) <= P.seqno(%llu) <= S.SWH(%llu)) and "
                                            "(P.ackno %s or LAWL(%llu) <= P.ackno(%llu) <= S.AWH(%llu), "
                                            "sending SYNC...\n",
                               dccp_packet_name(dh->dccph_type),
                               (unsigned long long) lswl,
                               (unsigned long long)
                               DCCP_SKB_CB(skb)->dccpd_seq,
                               (unsigned long long) dp->dccps_swh,
                               (DCCP_SKB_CB(skb)->dccpd_ack_seq ==
                                DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist" : "exists",
                               (unsigned long long) lawl,
                               (unsigned long long)
                               DCCP_SKB_CB(skb)->dccpd_ack_seq,
                               (unsigned long long) dp->dccps_awh);
                dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
                return -1;
        }

        return 0;
}

int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
                         const struct dccp_hdr *dh, const unsigned len)
{
        struct dccp_sock *dp = dccp_sk(sk);

        if (dccp_check_seqno(sk, skb))
                goto discard;

        if (dccp_parse_options(sk, skb))
                goto discard;

        if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
                dccp_event_ack_recv(sk, skb);

        if (dp->dccps_options.dccpo_send_ack_vector &&
            dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
                            DCCP_SKB_CB(skb)->dccpd_seq,
                            DCCP_ACKVEC_STATE_RECEIVED))
                goto discard;

        ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
        ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);

        switch (dccp_hdr(skb)->dccph_type) {
        case DCCP_PKT_DATAACK:
        case DCCP_PKT_DATA:
                /*
                 * FIXME: check if sk_receive_queue is full, schedule DATA_DROPPED
                 * option if it is.
                 */
                __skb_pull(skb, dh->dccph_doff * 4);
                __skb_queue_tail(&sk->sk_receive_queue, skb);
                skb_set_owner_r(skb, sk);
                sk->sk_data_ready(sk, 0);
                return 0;
        case DCCP_PKT_ACK:
                goto discard;
        case DCCP_PKT_RESET:
                /*
                 *  Step 9: Process Reset
                 *      If P.type == Reset,
                 *              Tear down connection
                 *              S.state := TIMEWAIT
                 *              Set TIMEWAIT timer
                 *              Drop packet and return
                */
                dccp_fin(sk, skb);
                dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
                return 0;
        case DCCP_PKT_CLOSEREQ:
                dccp_rcv_closereq(sk, skb);
                goto discard;
        case DCCP_PKT_CLOSE:
                dccp_rcv_close(sk, skb);
                return 0;
        case DCCP_PKT_REQUEST:
                /* Step 7 
                 *   or (S.is_server and P.type == Response)
                 *   or (S.is_client and P.type == Request)
                 *   or (S.state >= OPEN and P.type == Request
                 *      and P.seqno >= S.OSR)
                 *    or (S.state >= OPEN and P.type == Response
                 *      and P.seqno >= S.OSR)
                 *    or (S.state == RESPOND and P.type == Data),
                 *  Send Sync packet acknowledging P.seqno
                 *  Drop packet and return
                 */
                if (dp->dccps_role != DCCP_ROLE_LISTEN)
                        goto send_sync;
                goto check_seq;
        case DCCP_PKT_RESPONSE:
                if (dp->dccps_role != DCCP_ROLE_CLIENT)
                        goto send_sync;
check_seq:
                if (!before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_osr)) {
send_sync:
                        dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
                                       DCCP_PKT_SYNC);
                }
                break;
        case DCCP_PKT_SYNC:
                dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
                               DCCP_PKT_SYNCACK);
                /*
                 * From the draft:
                 *
                 * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
                 * MAY have non-zero-length application data areas, whose
                 * contents * receivers MUST ignore.
                 */
                goto discard;
        }

        DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
discard:
        __kfree_skb(skb);
        return 0;
}

static int dccp_rcv_request_sent_state_process(struct sock *sk,
                                               struct sk_buff *skb,
                                               const struct dccp_hdr *dh,
                                               const unsigned len)
{
        /* 
         *  Step 4: Prepare sequence numbers in REQUEST
         *     If S.state == REQUEST,
         *        If (P.type == Response or P.type == Reset)
         *              and S.AWL <= P.ackno <= S.AWH,
         *           / * Set sequence number variables corresponding to the
         *              other endpoint, so P will pass the tests in Step 6 * /
         *           Set S.GSR, S.ISR, S.SWL, S.SWH
         *           / * Response processing continues in Step 10; Reset
         *              processing continues in Step 9 * /
        */
        if (dh->dccph_type == DCCP_PKT_RESPONSE) {
                const struct inet_connection_sock *icsk = inet_csk(sk);
                struct dccp_sock *dp = dccp_sk(sk);

                /* Stop the REQUEST timer */
                inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
                BUG_TRAP(sk->sk_send_head != NULL);
                __kfree_skb(sk->sk_send_head);
                sk->sk_send_head = NULL;

                if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
                               dp->dccps_awl, dp->dccps_awh)) {
                        dccp_pr_debug("invalid ackno: S.AWL=%llu, "
                                      "P.ackno=%llu, S.AWH=%llu \n",
                                      (unsigned long long)dp->dccps_awl,
                           (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
                                      (unsigned long long)dp->dccps_awh);
                        goto out_invalid_packet;
                }

                dp->dccps_isr = DCCP_SKB_CB(skb)->dccpd_seq;
                dccp_update_gsr(sk, dp->dccps_isr);
                /*
                 * 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.
                 *
                 * AWL was adjusted in dccp_v4_connect -acme
                 */
                dccp_set_seqno(&dp->dccps_swl,
                               max48(dp->dccps_swl, dp->dccps_isr));

                if (ccid_hc_rx_init(dp->dccps_hc_rx_ccid, sk) != 0 ||
                    ccid_hc_tx_init(dp->dccps_hc_tx_ccid, sk) != 0) {
                        ccid_hc_rx_exit(dp->dccps_hc_rx_ccid, sk);
                        ccid_hc_tx_exit(dp->dccps_hc_tx_ccid, sk);
                        /* FIXME: send appropriate RESET code */
                        goto out_invalid_packet;
                }

                dccp_sync_mss(sk, dp->dccps_pmtu_cookie);

                /*
                 *    Step 10: Process REQUEST state (second part)
                 *       If S.state == REQUEST,
                 *        / * If we get here, P is a valid Response from the
                 *            server (see Step 4), and we should move to
                 *            PARTOPEN state. PARTOPEN means send an Ack,
                 *            don't send Data packets, retransmit Acks
                 *            periodically, and always include any Init Cookie
                 *            from the Response * /
                 *        S.state := PARTOPEN
                 *        Set PARTOPEN timer
                 *        Continue with S.state == PARTOPEN
                 *        / * Step 12 will send the Ack completing the
                 *            three-way handshake * /
                 */
                dccp_set_state(sk, DCCP_PARTOPEN);

                /* Make sure socket is routed, for correct metrics. */
                inet_sk_rebuild_header(sk);

                if (!sock_flag(sk, SOCK_DEAD)) {
                        sk->sk_state_change(sk);
                        sk_wake_async(sk, 0, POLL_OUT);
                }

                if (sk->sk_write_pending || icsk->icsk_ack.pingpong ||
                    icsk->icsk_accept_queue.rskq_defer_accept) {
                        /* Save one ACK. Data will be ready after
                         * several ticks, if write_pending is set.
                         *
                         * It may be deleted, but with this feature tcpdumps
                         * look so _wonderfully_ clever, that I was not able
                         * to stand against the temptation 8)     --ANK
                         */
                        /*
                         * OK, in DCCP we can as well do a similar trick, its
                         * even in the draft, but there is no need for us to
                         * schedule an ack here, as dccp_sendmsg does this for
                         * us, also stated in the draft. -acme
                         */
                        __kfree_skb(skb);
                        return 0;
                } 
                dccp_send_ack(sk);
                return -1;
        }

out_invalid_packet:
        /* dccp_v4_do_rcv will send a reset */
        DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
        return 1; 
}

static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
                                                   struct sk_buff *skb,
                                                   const struct dccp_hdr *dh,
                                                   const unsigned len)
{
        int queued = 0;

        switch (dh->dccph_type) {
        case DCCP_PKT_RESET:
                inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
                break;
        case DCCP_PKT_DATA:
                if (sk->sk_state == DCCP_RESPOND)
                        break;
        case DCCP_PKT_DATAACK:
        case DCCP_PKT_ACK:
                /*
                 * FIXME: we should be reseting the PARTOPEN (DELACK) timer
                 * here but only if we haven't used the DELACK timer for
                 * something else, like sending a delayed ack for a TIMESTAMP
                 * echo, etc, for now were not clearing it, sending an extra
                 * ACK when there is nothing else to do in DELACK is not a big
                 * deal after all.
                 */

                /* Stop the PARTOPEN timer */
                if (sk->sk_state == DCCP_PARTOPEN)
                        inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);

                dccp_sk(sk)->dccps_osr = DCCP_SKB_CB(skb)->dccpd_seq;
                dccp_set_state(sk, DCCP_OPEN);

                if (dh->dccph_type == DCCP_PKT_DATAACK ||
                    dh->dccph_type == DCCP_PKT_DATA) {
                        dccp_rcv_established(sk, skb, dh, len);
                        queued = 1; /* packet was queued
                                       (by dccp_rcv_established) */
                }
                break;
        }

        return queued;
}

int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
                           struct dccp_hdr *dh, unsigned len)
{
        struct dccp_sock *dp = dccp_sk(sk);
        struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
        const int old_state = sk->sk_state;
        int queued = 0;

        /*
         *  Step 3: Process LISTEN state
         *      (Continuing from dccp_v4_do_rcv and dccp_v6_do_rcv)
         *
         *     If S.state == LISTEN,
         *        If P.type == Request or P contains a valid Init Cookie
         *              option,
         *           * Must scan the packet's options to check for an Init
         *              Cookie.  Only the Init Cookie is processed here,
         *              however; other options are processed in Step 8.  This
         *              scan need only be performed if the endpoint uses Init
         *              Cookies *
         *           * Generate a new socket and switch to that socket *
         *           Set S := new socket for this port pair
         *           S.state = RESPOND
         *           Choose S.ISS (initial seqno) or set from Init Cookie
         *           Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
         *           Continue with S.state == RESPOND
         *           * A Response packet will be generated in Step 11 *
         *        Otherwise,
         *           Generate Reset(No Connection) unless P.type == Reset
         *           Drop packet and return
         *
         * NOTE: the check for the packet types is done in
         *       dccp_rcv_state_process
         */
        if (sk->sk_state == DCCP_LISTEN) {
                if (dh->dccph_type == DCCP_PKT_REQUEST) {
                        if (dccp_v4_conn_request(sk, skb) < 0)
                                return 1;

                        /* FIXME: do congestion control initialization */
                        goto discard;
                }
                if (dh->dccph_type == DCCP_PKT_RESET)
                        goto discard;

                /* Caller (dccp_v4_do_rcv) will send Reset */
                dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
                return 1;
        }

        if (sk->sk_state != DCCP_REQUESTING) {
                if (dccp_check_seqno(sk, skb))
                        goto discard;

                /*
                 * Step 8: Process options and mark acknowledgeable
                 */
                if (dccp_parse_options(sk, skb))
                        goto discard;

                if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
                        dccp_event_ack_recv(sk, skb);

                ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
                ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);

                if (dp->dccps_options.dccpo_send_ack_vector &&
                    dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
                                    DCCP_SKB_CB(skb)->dccpd_seq,
                                    DCCP_ACKVEC_STATE_RECEIVED))
                        goto discard;
        }

        /*
         *  Step 9: Process Reset
         *      If P.type == Reset,
         *              Tear down connection
         *              S.state := TIMEWAIT
         *              Set TIMEWAIT timer
         *              Drop packet and return
        */
        if (dh->dccph_type == DCCP_PKT_RESET) {
                /*
                 * Queue the equivalent of TCP fin so that dccp_recvmsg
                 * exits the loop
                 */
                dccp_fin(sk, skb);
                dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
                return 0;
                /*
                 *   Step 7: Check for unexpected packet types
                 *      If (S.is_server and P.type == CloseReq)
                 *          or (S.is_server and P.type == Response)
                 *          or (S.is_client and P.type == Request)
                 *          or (S.state == RESPOND and P.type == Data),
                 *        Send Sync packet acknowledging P.seqno
                 *        Drop packet and return
                 */
        } else if ((dp->dccps_role != DCCP_ROLE_CLIENT &&
                    (dh->dccph_type == DCCP_PKT_RESPONSE ||
                     dh->dccph_type == DCCP_PKT_CLOSEREQ)) ||
                    (dp->dccps_role == DCCP_ROLE_CLIENT &&
                     dh->dccph_type == DCCP_PKT_REQUEST) ||
                    (sk->sk_state == DCCP_RESPOND &&
                     dh->dccph_type == DCCP_PKT_DATA)) {
                dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNC);
                goto discard;
        } else if (dh->dccph_type == DCCP_PKT_CLOSEREQ) {
                dccp_rcv_closereq(sk, skb);
                goto discard;
        } else if (dh->dccph_type == DCCP_PKT_CLOSE) {
                dccp_rcv_close(sk, skb);
                return 0;
        }

        if (unlikely(dh->dccph_type == DCCP_PKT_SYNC)) {
                dccp_send_sync(sk, dcb->dccpd_seq, DCCP_PKT_SYNCACK);
                goto discard;
        }

        switch (sk->sk_state) {
        case DCCP_CLOSED:
                dcb->dccpd_reset_code = DCCP_RESET_CODE_NO_CONNECTION;
                return 1;

        case DCCP_REQUESTING:
                /* FIXME: do congestion control initialization */

                queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
                if (queued >= 0)
                        return queued;

                __kfree_skb(skb);
                return 0;

        case DCCP_RESPOND:
        case DCCP_PARTOPEN:
                queued = dccp_rcv_respond_partopen_state_process(sk, skb,
                                                                 dh, len);
                break;
        }

        if (dh->dccph_type == DCCP_PKT_ACK ||
            dh->dccph_type == DCCP_PKT_DATAACK) {
                switch (old_state) {
                case DCCP_PARTOPEN:
                        sk->sk_state_change(sk);
                        sk_wake_async(sk, 0, POLL_OUT);
                        break;
                }
        }

        if (!queued) { 
discard:
                __kfree_skb(skb);
        }
        return 0;
}