int dtls1_read_bytes(SSL *s, int type, int *recvd_type, unsigned char *buf,
                     int len, int peek)
{
    int al, i, j, ret;
    unsigned int n;
    SSL3_RECORD *rr;
    void (*cb) (const SSL *ssl, int type2, int val) = NULL;

    if (!SSL3_BUFFER_is_initialised(&s->rlayer.rbuf)) {
        /* Not initialized yet */
        if (!ssl3_setup_buffers(s))
            return (-1);
    }

    if ((type && (type != SSL3_RT_APPLICATION_DATA) &&
         (type != SSL3_RT_HANDSHAKE)) ||
        (peek && (type != SSL3_RT_APPLICATION_DATA))) {
        SSLerr(SSL_F_DTLS1_READ_BYTES, ERR_R_INTERNAL_ERROR);
        return -1;
    }

    /*
     * check whether there's a handshake message (client hello?) waiting
     */
    if ((ret = have_handshake_fragment(s, type, buf, len)))
        return ret;

    /*
     * Now s->rlayer.d->handshake_fragment_len == 0 if
     * type == SSL3_RT_HANDSHAKE.
     */

#ifndef OPENSSL_NO_SCTP
    /*
     * Continue handshake if it had to be interrupted to read app data with
     * SCTP.
     */
    if ((!ossl_statem_get_in_handshake(s) && SSL_in_init(s)) ||
        (BIO_dgram_is_sctp(SSL_get_rbio(s))
         && ossl_statem_in_sctp_read_sock(s)
         && s->s3->in_read_app_data != 2))
#else
    if (!ossl_statem_get_in_handshake(s) && SSL_in_init(s))
#endif
    {
        /* type == SSL3_RT_APPLICATION_DATA */
        i = s->handshake_func(s);
        if (i < 0)
            return (i);
        if (i == 0) {
            SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_SSL_HANDSHAKE_FAILURE);
            return (-1);
        }
    }

 start:
    s->rwstate = SSL_NOTHING;

    /*-
     * s->s3->rrec.type         - is the type of record
     * s->s3->rrec.data,    - data
     * s->s3->rrec.off,     - offset into 'data' for next read
     * s->s3->rrec.length,  - number of bytes.
     */
    rr = s->rlayer.rrec;

    /*
     * We are not handshaking and have no data yet, so process data buffered
     * during the last handshake in advance, if any.
     */
    if (SSL_is_init_finished(s) && SSL3_RECORD_get_length(rr) == 0) {
        pitem *item;
        item = pqueue_pop(s->rlayer.d->buffered_app_data.q);
        if (item) {
#ifndef OPENSSL_NO_SCTP
            /* Restore bio_dgram_sctp_rcvinfo struct */
            if (BIO_dgram_is_sctp(SSL_get_rbio(s))) {
                DTLS1_RECORD_DATA *rdata = (DTLS1_RECORD_DATA *)item->data;
                BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SCTP_SET_RCVINFO,
                         sizeof(rdata->recordinfo), &rdata->recordinfo);
            }
#endif

            dtls1_copy_record(s, item);

            OPENSSL_free(item->data);
            pitem_free(item);
        }
    }

    /* Check for timeout */
    if (dtls1_handle_timeout(s) > 0)
        goto start;

    /* get new packet if necessary */
    if ((SSL3_RECORD_get_length(rr) == 0)
        || (s->rlayer.rstate == SSL_ST_READ_BODY)) {
        ret = dtls1_get_record(s);
        if (ret <= 0) {
            ret = dtls1_read_failed(s, ret);
            /* anything other than a timeout is an error */
            if (ret <= 0)
                return (ret);
            else
                goto start;
        }
    }

    /* we now have a packet which can be read and processed */

    if (s->s3->change_cipher_spec /* set when we receive ChangeCipherSpec,
                                   * reset by ssl3_get_finished */
        && (SSL3_RECORD_get_type(rr) != SSL3_RT_HANDSHAKE)) {
        /*
         * We now have application data between CCS and Finished. Most likely
         * the packets were reordered on their way, so buffer the application
         * data for later processing rather than dropping the connection.
         */
        if (dtls1_buffer_record(s, &(s->rlayer.d->buffered_app_data),
                                SSL3_RECORD_get_seq_num(rr)) < 0) {
            SSLerr(SSL_F_DTLS1_READ_BYTES, ERR_R_INTERNAL_ERROR);
            return -1;
        }
        SSL3_RECORD_set_length(rr, 0);
        goto start;
    }

    /*
     * If the other end has shut down, throw anything we read away (even in
     * 'peek' mode)
     */
    if (s->shutdown & SSL_RECEIVED_SHUTDOWN) {
        SSL3_RECORD_set_length(rr, 0);
        s->rwstate = SSL_NOTHING;
        return (0);
    }

    if (type == SSL3_RECORD_get_type(rr)
        || (SSL3_RECORD_get_type(rr) == SSL3_RT_CHANGE_CIPHER_SPEC
            && type == SSL3_RT_HANDSHAKE && recvd_type != NULL)) {
        /*
         * SSL3_RT_APPLICATION_DATA or
         * SSL3_RT_HANDSHAKE or
         * SSL3_RT_CHANGE_CIPHER_SPEC
         */
        /*
         * make sure that we are not getting application data when we are
         * doing a handshake for the first time
         */
        if (SSL_in_init(s) && (type == SSL3_RT_APPLICATION_DATA) &&
            (s->enc_read_ctx == NULL)) {
            al = SSL_AD_UNEXPECTED_MESSAGE;
            SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_APP_DATA_IN_HANDSHAKE);
            goto f_err;
        }

        if (recvd_type != NULL)
            *recvd_type = SSL3_RECORD_get_type(rr);

        if (len <= 0)
            return (len);

        if ((unsigned int)len > SSL3_RECORD_get_length(rr))
            n = SSL3_RECORD_get_length(rr);
        else
            n = (unsigned int)len;

        memcpy(buf, &(SSL3_RECORD_get_data(rr)[SSL3_RECORD_get_off(rr)]), n);
        if (!peek) {
            SSL3_RECORD_sub_length(rr, n);
            SSL3_RECORD_add_off(rr, n);
            if (SSL3_RECORD_get_length(rr) == 0) {
                s->rlayer.rstate = SSL_ST_READ_HEADER;
                SSL3_RECORD_set_off(rr, 0);
            }
        }
#ifndef OPENSSL_NO_SCTP
        /*
         * We were about to renegotiate but had to read belated application
         * data first, so retry.
         */
        if (BIO_dgram_is_sctp(SSL_get_rbio(s)) &&
            SSL3_RECORD_get_type(rr) == SSL3_RT_APPLICATION_DATA &&
            ossl_statem_in_sctp_read_sock(s)) {
            s->rwstate = SSL_READING;
            BIO_clear_retry_flags(SSL_get_rbio(s));
            BIO_set_retry_read(SSL_get_rbio(s));
        }

        /*
         * We might had to delay a close_notify alert because of reordered
         * app data. If there was an alert and there is no message to read
         * anymore, finally set shutdown.
         */
        if (BIO_dgram_is_sctp(SSL_get_rbio(s)) &&
            s->d1->shutdown_received
            && !BIO_dgram_sctp_msg_waiting(SSL_get_rbio(s))) {
            s->shutdown |= SSL_RECEIVED_SHUTDOWN;
            return (0);
        }
#endif
        return (n);
    }

    /*
     * If we get here, then type != rr->type; if we have a handshake message,
     * then it was unexpected (Hello Request or Client Hello).
     */

    /*
     * In case of record types for which we have 'fragment' storage, fill
     * that so that we can process the data at a fixed place.
     */
    {
        unsigned int k, dest_maxlen = 0;
        unsigned char *dest = NULL;
        unsigned int *dest_len = NULL;

        if (SSL3_RECORD_get_type(rr) == SSL3_RT_HANDSHAKE) {
            dest_maxlen = sizeof s->rlayer.d->handshake_fragment;
            dest = s->rlayer.d->handshake_fragment;
            dest_len = &s->rlayer.d->handshake_fragment_len;
        } else if (SSL3_RECORD_get_type(rr) == SSL3_RT_ALERT) {
            dest_maxlen = sizeof(s->rlayer.d->alert_fragment);
            dest = s->rlayer.d->alert_fragment;
            dest_len = &s->rlayer.d->alert_fragment_len;
        }
#ifndef OPENSSL_NO_HEARTBEATS
        else if (SSL3_RECORD_get_type(rr) == DTLS1_RT_HEARTBEAT) {
            /* We allow a 0 return */
            if (dtls1_process_heartbeat(s, SSL3_RECORD_get_data(rr),
                                        SSL3_RECORD_get_length(rr)) < 0) {
                return -1;
            }
            /* Exit and notify application to read again */
            SSL3_RECORD_set_length(rr, 0);
            s->rwstate = SSL_READING;
            BIO_clear_retry_flags(SSL_get_rbio(s));
            BIO_set_retry_read(SSL_get_rbio(s));
            return (-1);
        }
#endif
        /* else it's a CCS message, or application data or wrong */
        else if (SSL3_RECORD_get_type(rr) != SSL3_RT_CHANGE_CIPHER_SPEC) {
            /*
             * Application data while renegotiating is allowed. Try again
             * reading.
             */
            if (SSL3_RECORD_get_type(rr) == SSL3_RT_APPLICATION_DATA) {
                BIO *bio;
                s->s3->in_read_app_data = 2;
                bio = SSL_get_rbio(s);
                s->rwstate = SSL_READING;
                BIO_clear_retry_flags(bio);
                BIO_set_retry_read(bio);
                return (-1);
            }

            /* Not certain if this is the right error handling */
            al = SSL_AD_UNEXPECTED_MESSAGE;
            SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_UNEXPECTED_RECORD);
            goto f_err;
        }

        if (dest_maxlen > 0) {
            /*
             * XDTLS: In a pathological case, the Client Hello may be
             * fragmented--don't always expect dest_maxlen bytes
             */
            if (SSL3_RECORD_get_length(rr) < dest_maxlen) {
#ifdef DTLS1_AD_MISSING_HANDSHAKE_MESSAGE
                /*
                 * for normal alerts rr->length is 2, while
                 * dest_maxlen is 7 if we were to handle this
                 * non-existing alert...
                 */
                FIX ME;
#endif
                s->rlayer.rstate = SSL_ST_READ_HEADER;
                SSL3_RECORD_set_length(rr, 0);
                goto start;
            }

            /* now move 'n' bytes: */
            for (k = 0; k < dest_maxlen; k++) {
                dest[k] = SSL3_RECORD_get_data(rr)[SSL3_RECORD_get_off(rr)];
                SSL3_RECORD_add_off(rr, 1);
                SSL3_RECORD_add_length(rr, -1);
            }
            *dest_len = dest_maxlen;
        }
    }

    /*-
     * s->rlayer.d->handshake_fragment_len == 12  iff  rr->type == SSL3_RT_HANDSHAKE;
     * s->rlayer.d->alert_fragment_len == 7      iff  rr->type == SSL3_RT_ALERT.
     * (Possibly rr is 'empty' now, i.e. rr->length may be 0.)
     */

    /* If we are a client, check for an incoming 'Hello Request': */
    if ((!s->server) &&
        (s->rlayer.d->handshake_fragment_len >= DTLS1_HM_HEADER_LENGTH) &&
        (s->rlayer.d->handshake_fragment[0] == SSL3_MT_HELLO_REQUEST) &&
        (s->session != NULL) && (s->session->cipher != NULL)) {
        s->rlayer.d->handshake_fragment_len = 0;

        if ((s->rlayer.d->handshake_fragment[1] != 0) ||
            (s->rlayer.d->handshake_fragment[2] != 0) ||
            (s->rlayer.d->handshake_fragment[3] != 0)) {
            al = SSL_AD_DECODE_ERROR;
            SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_BAD_HELLO_REQUEST);
            goto f_err;
        }

        /*
         * no need to check sequence number on HELLO REQUEST messages
         */

        if (s->msg_callback)
            s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE,
                            s->rlayer.d->handshake_fragment, 4, s,
                            s->msg_callback_arg);

        if (SSL_is_init_finished(s) &&
            !(s->s3->flags & SSL3_FLAGS_NO_RENEGOTIATE_CIPHERS) &&
            !s->s3->renegotiate) {
            s->d1->handshake_read_seq++;
            s->new_session = 1;
            ssl3_renegotiate(s);
            if (ssl3_renegotiate_check(s)) {
                i = s->handshake_func(s);
                if (i < 0)
                    return (i);
                if (i == 0) {
                    SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_SSL_HANDSHAKE_FAILURE);
                    return (-1);
                }

                if (!(s->mode & SSL_MODE_AUTO_RETRY)) {
                    if (SSL3_BUFFER_get_left(&s->rlayer.rbuf) == 0) {
                        /* no read-ahead left? */
                        BIO *bio;
                        /*
                         * In the case where we try to read application data,
                         * but we trigger an SSL handshake, we return -1 with
                         * the retry option set.  Otherwise renegotiation may
                         * cause nasty problems in the blocking world
                         */
                        s->rwstate = SSL_READING;
                        bio = SSL_get_rbio(s);
                        BIO_clear_retry_flags(bio);
                        BIO_set_retry_read(bio);
                        return (-1);
                    }
                }
            }
        }
        /*
         * we either finished a handshake or ignored the request, now try
         * again to obtain the (application) data we were asked for
         */
        goto start;
    }

    if (s->rlayer.d->alert_fragment_len >= DTLS1_AL_HEADER_LENGTH) {
        int alert_level = s->rlayer.d->alert_fragment[0];
        int alert_descr = s->rlayer.d->alert_fragment[1];

        s->rlayer.d->alert_fragment_len = 0;

        if (s->msg_callback)
            s->msg_callback(0, s->version, SSL3_RT_ALERT,
                            s->rlayer.d->alert_fragment, 2, s,
                            s->msg_callback_arg);

        if (s->info_callback != NULL)
            cb = s->info_callback;
        else if (s->ctx->info_callback != NULL)
            cb = s->ctx->info_callback;

        if (cb != NULL) {
            j = (alert_level << 8) | alert_descr;
            cb(s, SSL_CB_READ_ALERT, j);
        }

        if (alert_level == SSL3_AL_WARNING) {
            s->s3->warn_alert = alert_descr;
            if (alert_descr == SSL_AD_CLOSE_NOTIFY) {
#ifndef OPENSSL_NO_SCTP
                /*
                 * With SCTP and streams the socket may deliver app data
                 * after a close_notify alert. We have to check this first so
                 * that nothing gets discarded.
                 */
                if (BIO_dgram_is_sctp(SSL_get_rbio(s)) &&
                    BIO_dgram_sctp_msg_waiting(SSL_get_rbio(s))) {
                    s->d1->shutdown_received = 1;
                    s->rwstate = SSL_READING;
                    BIO_clear_retry_flags(SSL_get_rbio(s));
                    BIO_set_retry_read(SSL_get_rbio(s));
                    return -1;
                }
#endif
                s->shutdown |= SSL_RECEIVED_SHUTDOWN;
                return (0);
            }
#if 0
            /* XXX: this is a possible improvement in the future */
            /* now check if it's a missing record */
            if (alert_descr == DTLS1_AD_MISSING_HANDSHAKE_MESSAGE) {
                unsigned short seq;
                unsigned int frag_off;
                unsigned char *p = &(s->rlayer.d->alert_fragment[2]);

                n2s(p, seq);
                n2l3(p, frag_off);

                dtls1_retransmit_message(s,
                                         dtls1_get_queue_priority
                                         (frag->msg_header.seq, 0), frag_off,
                                         &found);
                if (!found && SSL_in_init(s)) {
                    /*
                     * fprintf( stderr,"in init = %d\n", SSL_in_init(s));
                     */
                    /*
                     * requested a message not yet sent, send an alert
                     * ourselves
                     */
                    ssl3_send_alert(s, SSL3_AL_WARNING,
                                    DTLS1_AD_MISSING_HANDSHAKE_MESSAGE);
                }
            }
#endif
        } else if (alert_level == SSL3_AL_FATAL) {
            char tmp[16];

            s->rwstate = SSL_NOTHING;
            s->s3->fatal_alert = alert_descr;
            SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_AD_REASON_OFFSET + alert_descr);
            BIO_snprintf(tmp, sizeof tmp, "%d", alert_descr);
            ERR_add_error_data(2, "SSL alert number ", tmp);
            s->shutdown |= SSL_RECEIVED_SHUTDOWN;
            SSL_CTX_remove_session(s->session_ctx, s->session);
            return (0);
        } else {
            al = SSL_AD_ILLEGAL_PARAMETER;
            SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_UNKNOWN_ALERT_TYPE);
            goto f_err;
        }

        goto start;
    }

    if (s->shutdown & SSL_SENT_SHUTDOWN) { /* but we have not received a
                                            * shutdown */
        s->rwstate = SSL_NOTHING;
        SSL3_RECORD_set_length(rr, 0);
        return (0);
    }

    if (SSL3_RECORD_get_type(rr) == SSL3_RT_CHANGE_CIPHER_SPEC) {
        /*
         * We can't process a CCS now, because previous handshake messages
         * are still missing, so just drop it.
         */
        SSL3_RECORD_set_length(rr, 0);
        goto start;
    }

    /*
     * Unexpected handshake message (Client Hello, or protocol violation)
     */
    if ((s->rlayer.d->handshake_fragment_len >= DTLS1_HM_HEADER_LENGTH) &&
        !ossl_statem_get_in_handshake(s)) {
        struct hm_header_st msg_hdr;

        /* this may just be a stale retransmit */
        dtls1_get_message_header(rr->data, &msg_hdr);
        if (SSL3_RECORD_get_epoch(rr) != s->rlayer.d->r_epoch) {
            SSL3_RECORD_set_length(rr, 0);
            goto start;
        }

        /*
         * If we are server, we may have a repeated FINISHED of the client
         * here, then retransmit our CCS and FINISHED.
         */
        if (msg_hdr.type == SSL3_MT_FINISHED) {
            if (dtls1_check_timeout_num(s) < 0)
                return -1;

            dtls1_retransmit_buffered_messages(s);
            SSL3_RECORD_set_length(rr, 0);
            goto start;
        }

        if (SSL_is_init_finished(s) &&
            !(s->s3->flags & SSL3_FLAGS_NO_RENEGOTIATE_CIPHERS)) {
            ossl_statem_set_in_init(s, 1);
            s->renegotiate = 1;
            s->new_session = 1;
        }
        i = s->handshake_func(s);
        if (i < 0)
            return (i);
        if (i == 0) {
            SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_SSL_HANDSHAKE_FAILURE);
            return (-1);
        }

        if (!(s->mode & SSL_MODE_AUTO_RETRY)) {
            if (SSL3_BUFFER_get_left(&s->rlayer.rbuf) == 0) {
                /* no read-ahead left? */
                BIO *bio;
                /*
                 * In the case where we try to read application data, but we
                 * trigger an SSL handshake, we return -1 with the retry
                 * option set.  Otherwise renegotiation may cause nasty
                 * problems in the blocking world
                 */
                s->rwstate = SSL_READING;
                bio = SSL_get_rbio(s);
                BIO_clear_retry_flags(bio);
                BIO_set_retry_read(bio);
                return (-1);
            }
        }
        goto start;
    }

    switch (SSL3_RECORD_get_type(rr)) {
    default:
        /* TLS just ignores unknown message types */
        if (s->version == TLS1_VERSION) {
            SSL3_RECORD_set_length(rr, 0);
            goto start;
        }
        al = SSL_AD_UNEXPECTED_MESSAGE;
        SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_UNEXPECTED_RECORD);
        goto f_err;
    case SSL3_RT_CHANGE_CIPHER_SPEC:
    case SSL3_RT_ALERT:
    case SSL3_RT_HANDSHAKE:
        /*
         * we already handled all of these, with the possible exception of
         * SSL3_RT_HANDSHAKE when ossl_statem_get_in_handshake(s) is true, but
         * that should not happen when type != rr->type
         */
        al = SSL_AD_UNEXPECTED_MESSAGE;
        SSLerr(SSL_F_DTLS1_READ_BYTES, ERR_R_INTERNAL_ERROR);
        goto f_err;
    case SSL3_RT_APPLICATION_DATA:
        /*
         * At this point, we were expecting handshake data, but have
         * application data.  If the library was running inside ssl3_read()
         * (i.e. in_read_app_data is set) and it makes sense to read
         * application data at this point (session renegotiation not yet
         * started), we will indulge it.
         */
        if (s->s3->in_read_app_data &&
            (s->s3->total_renegotiations != 0) &&
            ossl_statem_app_data_allowed(s)) {
            s->s3->in_read_app_data = 2;
            return (-1);
        } else {
            al = SSL_AD_UNEXPECTED_MESSAGE;
            SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_UNEXPECTED_RECORD);
            goto f_err;
        }
    }
    /* not reached */

 f_err:
    ssl3_send_alert(s, SSL3_AL_FATAL, al);
    return (-1);
}