udptl.c

Go to the documentation of this file.

/*
 * Asterisk -- An open source telephony toolkit.
 *
 * UDPTL support for T.38
 *
 * Copyright (C) 2005, Steve Underwood, partly based on RTP code which is
 * Copyright (C) 1999-2009, Digium, Inc.
 *
 * Steve Underwood <steveu@coppice.org>
 * Kevin P. Fleming <kpfleming@digium.com>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 *
 * A license has been granted to Digium (via disclaimer) for the use of
 * this code.
 */
 
/*!
 * \file
 *
 * \brief UDPTL support for T.38 faxing
 *
 *
 * \author Mark Spencer <markster@digium.com>
 * \author Steve Underwood <steveu@coppice.org>
 * \author Kevin P. Fleming <kpfleming@digium.com>
 *
 * \page T38fax_udptl T.38 support :: UDPTL
 *
 * Asterisk supports T.38 fax passthrough, origination and termination. It does
 * not support gateway operation.
 *
 * UDPTL is handled very much like RTP. It can be reinvited to go directly between
 * the endpoints, without involving Asterisk in the media stream.
 *
 * \b References:
 * - udptl.c
 * - app_fax.c
 */
 
/*! \li \ref udptl.c uses the configuration file \ref udptl.conf
 * \addtogroup configuration_file Configuration Files
 */
 
/*!
 * \page udptl.conf udptl.conf
 * \verbinclude udptl.conf.sample
 */
 
/*** MODULEINFO
    <support_level>core</support_level>
 ***/
 
#include "asterisk.h"
 
#include <sys/time.h>
#include <signal.h>
#include <fcntl.h>
 
#include "asterisk/module.h"
#include "asterisk/udptl.h"
#include "asterisk/frame.h"
#include "asterisk/channel.h"
#include "asterisk/acl.h"
#include "asterisk/config_options.h"
#include "asterisk/lock.h"
#include "asterisk/utils.h"
#include "asterisk/netsock2.h"
#include "asterisk/cli.h"
#include "asterisk/unaligned.h"
 
/*** DOCUMENTATION
    <configInfo name="udptl" language="en_US">
        <configFile name="udptl.conf">
            <configObject name="global">
                <synopsis>Global options for configuring UDPTL</synopsis>
                <configOption name="udptlstart">
                    <synopsis>The start of the UDPTL port range</synopsis>
                </configOption>
                <configOption name="udptlend">
                    <synopsis>The end of the UDPTL port range</synopsis>
                </configOption>
                <configOption name="udptlchecksums">
                    <synopsis>Whether to enable or disable UDP checksums on UDPTL traffic</synopsis>
                </configOption>
                <configOption name="udptlfecentries">
                    <synopsis>The number of error correction entries in a UDPTL packet</synopsis>
                </configOption>
                <configOption name="udptlfecspan">
                    <synopsis>The span over which parity is calculated for FEC in a UDPTL packet</synopsis>
                </configOption>
                <configOption name="use_even_ports">
                    <synopsis>Whether to only use even-numbered UDPTL ports</synopsis>
                </configOption>
                <configOption name="t38faxudpec">
                    <synopsis>Removed</synopsis>
                </configOption>
                <configOption name="t38faxmaxdatagram">
                    <synopsis>Removed</synopsis>
                </configOption>
            </configObject>
        </configFile>
    </configInfo>
***/
 
#define UDPTL_MTU       1200
 
#if !defined(FALSE)
#define FALSE 0
#endif
#if !defined(TRUE)
#define TRUE (!FALSE)
#endif
 
#define LOG_TAG(u) S_OR(u->tag, "no tag")
 
#define DEFAULT_UDPTLSTART 4000
#define DEFAULT_UDPTLEND 4999
 
static int udptldebug;                      /*!< Are we debugging? */
static struct ast_sockaddr udptldebugaddr;   /*!< Debug packets to/from this host */
 
#define LOCAL_FAX_MAX_DATAGRAM      1400
#define DEFAULT_FAX_MAX_DATAGRAM    400
#define FAX_MAX_DATAGRAM_LIMIT      1400
#define MAX_FEC_ENTRIES             5
#define MAX_FEC_SPAN                5
 
#define UDPTL_BUF_MASK              15
 
typedef struct {
    int buf_len;
    uint8_t buf[LOCAL_FAX_MAX_DATAGRAM];
} udptl_fec_tx_buffer_t;
 
typedef struct {
    int buf_len;
    uint8_t buf[LOCAL_FAX_MAX_DATAGRAM];
    unsigned int fec_len[MAX_FEC_ENTRIES];
    uint8_t fec[MAX_FEC_ENTRIES][LOCAL_FAX_MAX_DATAGRAM];
    unsigned int fec_span;
    unsigned int fec_entries;
} udptl_fec_rx_buffer_t;
 
/*! \brief Structure for an UDPTL session */
struct ast_udptl {
    int fd;
    char resp;
    struct ast_frame f[16];
    unsigned char rawdata[8192 + AST_FRIENDLY_OFFSET];
    unsigned int lasteventseqn;
    int nat;
    int flags;
    struct ast_sockaddr us;
    struct ast_sockaddr them;
    int *ioid;
    struct ast_sched_context *sched;
    struct io_context *io;
    void *data;
    char *tag;
    ast_udptl_callback callback;
 
    /*! This option indicates the error correction scheme used in transmitted UDPTL
     * packets and expected in received UDPTL packets.
     */
    enum ast_t38_ec_modes error_correction_scheme;
 
    /*! This option indicates the number of error correction entries transmitted in
     * UDPTL packets and expected in received UDPTL packets.
     */
    unsigned int error_correction_entries;
 
    /*! This option indicates the span of the error correction entries in transmitted
     * UDPTL packets (FEC only).
     */
    unsigned int error_correction_span;
 
    /*! The maximum size UDPTL packet that can be accepted by
     * the remote device.
     */
    int far_max_datagram;
 
    /*! The maximum size UDPTL packet that we are prepared to
     * accept, or -1 if it hasn't been calculated since the last
     * changes were applied to the UDPTL structure.
     */
    int local_max_datagram;
 
    /*! The maximum IFP that can be submitted for sending
     * to the remote device. Calculated from far_max_datagram,
     * error_correction_scheme and error_correction_entries,
     * or -1 if it hasn't been calculated since the last
     * changes were applied to the UDPTL structure.
     */
    int far_max_ifp;
 
    /*! The maximum IFP that the local endpoint is prepared
     * to accept. Along with error_correction_scheme and
     * error_correction_entries, used to calculate local_max_datagram.
     */
    int local_max_ifp;
 
    unsigned int tx_seq_no;
    unsigned int rx_seq_no;
 
    udptl_fec_tx_buffer_t tx[UDPTL_BUF_MASK + 1];
    udptl_fec_rx_buffer_t rx[UDPTL_BUF_MASK + 1];
};
 
struct udptl_global_options {
    unsigned int start; /*< The UDPTL start port */
    unsigned int end;   /*< The UDPTL end port */
    unsigned int fecentries;
    unsigned int fecspan;
    unsigned int nochecksums;
    unsigned int use_even_ports;
};
 
static AO2_GLOBAL_OBJ_STATIC(globals);
 
struct udptl_config {
    struct udptl_global_options *general;
};
 
static void *udptl_snapshot_alloc(void);
static int udptl_pre_apply_config(void);
 
static struct aco_type general_option = {
    .type = ACO_GLOBAL,
    .name = "global",
    .category_match = ACO_WHITELIST_EXACT,
    .item_offset = offsetof(struct udptl_config, general),
    .category = "general",
};
 
static struct aco_type *general_options[] = ACO_TYPES(&general_option);
 
static struct aco_file udptl_conf = {
    .filename = "udptl.conf",
    .types = ACO_TYPES(&general_option),
};
 
CONFIG_INFO_CORE("udptl", cfg_info, globals, udptl_snapshot_alloc,
    .files = ACO_FILES(&udptl_conf),
    .pre_apply_config = udptl_pre_apply_config,
);
 
static inline int udptl_debug_test_addr(const struct ast_sockaddr *addr)
{
    if (udptldebug == 0)
        return 0;
 
    if (ast_sockaddr_isnull(&udptldebugaddr)) {
        return 1;
    }
 
    if (ast_sockaddr_port(&udptldebugaddr)) {
        return !ast_sockaddr_cmp(&udptldebugaddr, addr);
    } else {
        return !ast_sockaddr_cmp_addr(&udptldebugaddr, addr);
    }
}
 
static int decode_length(uint8_t *buf, unsigned int limit, unsigned int *len, unsigned int *pvalue)
{
    if (*len >= limit)
        return -1;
    if ((buf[*len] & 0x80) == 0) {
        *pvalue = buf[*len];
        (*len)++;
        return 0;
    }
    if ((buf[*len] & 0x40) == 0) {
        if (*len == limit - 1)
            return -1;
        *pvalue = (buf[*len] & 0x3F) << 8;
        (*len)++;
        *pvalue |= buf[*len];
        (*len)++;
        return 0;
    }
    *pvalue = (buf[*len] & 0x3F) << 14;
    (*len)++;
    /* We have a fragment.  Currently we don't process fragments. */
    ast_debug(1, "UDPTL packet with length greater than 16K received, decoding will fail\n");
    return 1;
}
/*- End of function --------------------------------------------------------*/
 
static int decode_open_type(uint8_t *buf, unsigned int limit, unsigned int *len, const uint8_t **p_object, unsigned int *p_num_octets)
{
    unsigned int octet_cnt = 0;
 
    if (decode_length(buf, limit, len, &octet_cnt) != 0)
        return -1;
 
    /* Make sure the buffer contains at least the number of bits requested */
    if ((*len + octet_cnt) > limit) {
        return -1;
    }
 
    *p_num_octets = octet_cnt;
    *p_object = &buf[*len];
    *len += octet_cnt;
 
    return 0;
}
/*- End of function --------------------------------------------------------*/
 
static unsigned int encode_length(uint8_t *buf, unsigned int *len, unsigned int value)
{
    unsigned int multiplier;
 
    if (value < 0x80) {
        /* 1 octet */
        buf[*len] = value;
        (*len)++;
        return value;
    }
    if (value < 0x4000) {
        /* 2 octets */
        /* Set the first bit of the first octet */
        buf[*len] = ((0x8000 | value) >> 8) & 0xFF;
        (*len)++;
        buf[*len] = value & 0xFF;
        (*len)++;
        return value;
    }
    /* Fragmentation */
    multiplier = (value < 0x10000) ? (value >> 14) : 4;
    /* Set the first 2 bits of the octet */
    buf[*len] = 0xC0 | multiplier;
    (*len)++;
    return multiplier << 14;
}
/*- End of function --------------------------------------------------------*/
 
static int encode_open_type(const struct ast_udptl *udptl, uint8_t *buf, unsigned int buflen,
                unsigned int *len, const uint8_t *data, unsigned int num_octets)
{
    unsigned int enclen;
    unsigned int octet_idx;
    uint8_t zero_byte;
 
    /* If open type is of zero length, add a single zero byte (10.1) */
    if (num_octets == 0) {
        zero_byte = 0;
        data = &zero_byte;
        num_octets = 1;
    }
    /* Encode the open type */
    for (octet_idx = 0; ; num_octets -= enclen, octet_idx += enclen) {
        enclen = encode_length(buf, len, num_octets);
        if (enclen + *len > buflen) {
            ast_log(LOG_ERROR, "UDPTL (%s): Buffer overflow detected (%u + %u > %u)\n",
                LOG_TAG(udptl), enclen, *len, buflen);
            return -1;
        }
        if (enclen > 0) {
            memcpy(&buf[*len], &data[octet_idx], enclen);
            *len += enclen;
        }
        if (enclen >= num_octets)
            break;
    }
 
    return 0;
}
/*- End of function --------------------------------------------------------*/
 
static int udptl_rx_packet(struct ast_udptl *s, uint8_t *buf, unsigned int len)
{
    int stat1;
    int stat2;
    int i;
    unsigned int ptr;   /* an index that keeps track of how much of the UDPTL packet has been processed */
    int seq_no;
    const uint8_t *ifp = NULL;
    const uint8_t *data = NULL;
    unsigned int ifp_len = 0;
    int repaired[16];
    const uint8_t *bufs[ARRAY_LEN(s->f) - 1];
    unsigned int lengths[ARRAY_LEN(s->f) - 1];
    int span;
    int entries;
    int ifp_no;
 
    ptr = 0;
    ifp_no = 0;
    memset(&s->f[0], 0, sizeof(s->f[0]));
 
    /* Decode seq_number */
    if (ptr + 2 > len)
        return -1;
    seq_no = (buf[0] << 8) | buf[1];
    ptr += 2;
 
    /* UDPTL sequence numbers are 16 bit so after 0xFFFF comes
       0 which breaks all packet recovery logic.  To fix this
       if we see that next expected packet (rx_seq_no) is close
       to or beyond the wrap around limit & the received packet
       is still near zero, then we 'unwrap' the received seqno
       so it has the value it would have had.  After a 16
       packet grace period (there shouldn't be  more than
       that many recovery packets) we wrap the expected
       sequence number around and things can return back
       to normal */
    if (seq_no < 0x000F && s->rx_seq_no > 0xFFF0) {
        /* received seq_no has wrapped adjust it */
        seq_no += 0x10000;
    } else {
        /* otherwise make sure expected rx_seq_no is properly wrapped */
        s->rx_seq_no &= 0xFFFF;
    }
 
    /* Break out the primary packet */
    if ((stat1 = decode_open_type(buf, len, &ptr, &ifp, &ifp_len)) != 0)
        return -1;
    /* Decode error_recovery */
    if (ptr + 1 > len)
        return -1;
    if ((buf[ptr++] & 0x80) == 0) {
        /* Secondary packet mode for error recovery */
        if (seq_no > s->rx_seq_no) {
            /* We received a later packet than we expected, so we need to check if we can fill in the gap from the
               secondary packets. */
            int total_count = 0;
            do {
                unsigned int count;
                if ((stat2 = decode_length(buf, len, &ptr, &count)) < 0)
                    return -1;
                for (i = 0; i < count && total_count + i < ARRAY_LEN(bufs); i++) {
                    if ((stat1 = decode_open_type(buf, len, &ptr, &bufs[total_count + i], &lengths[total_count + i])) != 0) {
                        return -1;
                    }
                    /* valid secondaries can contain zero-length packets that should be ignored */
                    if (!bufs[total_count + i] || !lengths[total_count + i]) {
                        /* drop the count of items to process and reuse the buffers that were just set */
                        i--;
                        count--;
                    }
                }
                total_count += i;
            }
            while (stat2 > 0 && total_count < ARRAY_LEN(bufs));
            /* Step through in reverse order, so we go oldest to newest */
            for (i = total_count; i > 0; i--) {
                if (seq_no - i >= s->rx_seq_no) {
                    /* This one wasn't seen before */
                    /* Decode the secondary IFP packet */
                    ast_debug(3, "Recovering lost packet via secondary %d, len %u\n", seq_no - i, lengths[i - 1]);
                    s->f[ifp_no].frametype = AST_FRAME_MODEM;
                    s->f[ifp_no].subclass.integer = AST_MODEM_T38;
 
                    s->f[ifp_no].mallocd = 0;
                    s->f[ifp_no].seqno = seq_no - i;
                    s->f[ifp_no].datalen = lengths[i - 1];
                    s->f[ifp_no].data.ptr = (uint8_t *) bufs[i - 1];
                    s->f[ifp_no].offset = 0;
                    s->f[ifp_no].src = "UDPTL";
                    if (ifp_no > 0)
                        AST_LIST_NEXT(&s->f[ifp_no - 1], frame_list) = &s->f[ifp_no];
                    AST_LIST_NEXT(&s->f[ifp_no], frame_list) = NULL;
                    ifp_no++;
                }
            }
        }
    }
    else
    {
        int j;
        int l;
        int x;
        /* FEC mode for error recovery */
        /* Our buffers cannot tolerate overlength IFP packets in FEC mode */
        if (ifp_len > LOCAL_FAX_MAX_DATAGRAM)
            return -1;
        /* Update any missed slots in the buffer */
        for ( ; seq_no > s->rx_seq_no; s->rx_seq_no++) {
            x = s->rx_seq_no & UDPTL_BUF_MASK;
            s->rx[x].buf_len = -1;
            s->rx[x].fec_len[0] = 0;
            s->rx[x].fec_span = 0;
            s->rx[x].fec_entries = 0;
        }
 
        x = seq_no & UDPTL_BUF_MASK;
 
        memset(repaired, 0, sizeof(repaired));
 
        /* Save the new IFP packet */
        memcpy(s->rx[x].buf, ifp, ifp_len);
        s->rx[x].buf_len = ifp_len;
        repaired[x] = TRUE;
 
        /* Decode the FEC packets */
        /* The span is defined as an unconstrained integer, but will never be more
           than a small value. */
        if (ptr + 2 > len)
            return -1;
        if (buf[ptr++] != 1)
            return -1;
        span = buf[ptr++];
        s->rx[x].fec_span = span;
 
        /* The number of entries is defined as a length, but will only ever be a small
           value. Treat it as such. */
        if (ptr + 1 > len)
            return -1;
        entries = buf[ptr++];
        if (entries > MAX_FEC_ENTRIES) {
            return -1;
        }
        s->rx[x].fec_entries = entries;
 
        /* Decode the elements */
        for (i = 0; i < entries; i++) {
            if ((stat1 = decode_open_type(buf, len, &ptr, &data, &s->rx[x].fec_len[i])) != 0)
                return -1;
            if (s->rx[x].fec_len[i] > LOCAL_FAX_MAX_DATAGRAM)
                return -1;
 
            /* Save the new FEC data */
            memcpy(s->rx[x].fec[i], data, s->rx[x].fec_len[i]);
#if 0
            fprintf(stderr, "FEC: ");
            for (j = 0; j < s->rx[x].fec_len[i]; j++)
                fprintf(stderr, "%02hhX ", data[j]);
            fprintf(stderr, "\n");
#endif
        }
 
        /* See if we can reconstruct anything which is missing */
        /* TODO: this does not comprehensively hunt back and repair everything that is possible */
        for (l = x; l != ((x - (16 - span*entries)) & UDPTL_BUF_MASK); l = (l - 1) & UDPTL_BUF_MASK) {
            int m;
            if (s->rx[l].fec_len[0] <= 0)
                continue;
            for (m = 0; m < s->rx[l].fec_entries; m++) {
                int k;
                int which;
                int limit = (l + m) & UDPTL_BUF_MASK;
 
                /* only repair buffers that actually exist! */
                if (seq_no <= (s->rx[l].fec_span * s->rx[l].fec_entries) - m) {
                    continue;
                }
 
                for (which = -1, k = (limit - s->rx[l].fec_span * s->rx[l].fec_entries) & UDPTL_BUF_MASK; k != limit; k = (k + s->rx[l].fec_entries) & UDPTL_BUF_MASK) {
                    if (s->rx[k].buf_len <= 0)
                        which = (which == -1) ? k : -2;
                }
                if (which >= 0) {
                    /* Repairable */
                    for (j = 0; j < s->rx[l].fec_len[m]; j++) {
                        s->rx[which].buf[j] = s->rx[l].fec[m][j];
                        for (k = (limit - s->rx[l].fec_span * s->rx[l].fec_entries) & UDPTL_BUF_MASK; k != limit; k = (k + s->rx[l].fec_entries) & UDPTL_BUF_MASK)
                            s->rx[which].buf[j] ^= (s->rx[k].buf_len > j) ? s->rx[k].buf[j] : 0;
                    }
                    s->rx[which].buf_len = s->rx[l].fec_len[m];
                    repaired[which] = TRUE;
                }
            }
        }
        /* Now play any new packets forwards in time */
        for (l = (x + 1) & UDPTL_BUF_MASK, j = seq_no - UDPTL_BUF_MASK; l != x; l = (l + 1) & UDPTL_BUF_MASK, j++) {
            if (repaired[l]) {
                //fprintf(stderr, "Fixed packet %d, len %d\n", j, l);
                s->f[ifp_no].frametype = AST_FRAME_MODEM;
                s->f[ifp_no].subclass.integer = AST_MODEM_T38;
 
                s->f[ifp_no].mallocd = 0;
                s->f[ifp_no].seqno = j;
                s->f[ifp_no].datalen = s->rx[l].buf_len;
                s->f[ifp_no].data.ptr = s->rx[l].buf;
                s->f[ifp_no].offset = 0;
                s->f[ifp_no].src = "UDPTL";
                if (ifp_no > 0)
                    AST_LIST_NEXT(&s->f[ifp_no - 1], frame_list) = &s->f[ifp_no];
                AST_LIST_NEXT(&s->f[ifp_no], frame_list) = NULL;
                ifp_no++;
            }
        }
    }
 
    /* If packets are received out of sequence, we may have already processed this packet from the error
       recovery information in a packet already received. */
    if (seq_no >= s->rx_seq_no) {
        /* Decode the primary IFP packet */
        s->f[ifp_no].frametype = AST_FRAME_MODEM;
        s->f[ifp_no].subclass.integer = AST_MODEM_T38;
 
        s->f[ifp_no].mallocd = 0;
        s->f[ifp_no].seqno = seq_no;
        s->f[ifp_no].datalen = ifp_len;
        s->f[ifp_no].data.ptr = (uint8_t *) ifp;
        s->f[ifp_no].offset = 0;
        s->f[ifp_no].src = "UDPTL";
        if (ifp_no > 0)
            AST_LIST_NEXT(&s->f[ifp_no - 1], frame_list) = &s->f[ifp_no];
        AST_LIST_NEXT(&s->f[ifp_no], frame_list) = NULL;
 
        ifp_no++;
    }
 
    s->rx_seq_no = seq_no + 1;
    return ifp_no;
}
/*- End of function --------------------------------------------------------*/
 
static int udptl_build_packet(struct ast_udptl *s, uint8_t *buf, unsigned int buflen, uint8_t *ifp, unsigned int ifp_len)
{
    uint8_t fec[LOCAL_FAX_MAX_DATAGRAM * 2] = { 0, };
    int i;
    int j;
    int seq;
    int entry;
    int entries;
    int span;
    int m;
    unsigned int len;
    int limit;
    int high_tide;
 
    seq = s->tx_seq_no & 0xFFFF;
 
    /* Map the sequence number to an entry in the circular buffer */
    entry = seq & UDPTL_BUF_MASK;
 
    /* We save the message in a circular buffer, for generating FEC or
       redundancy sets later on. */
    s->tx[entry].buf_len = ifp_len;
    memcpy(s->tx[entry].buf, ifp, ifp_len);
 
    /* Build the UDPTLPacket */
 
    len = 0;
    /* Encode the sequence number */
    buf[len++] = (seq >> 8) & 0xFF;
    buf[len++] = seq & 0xFF;
 
    /* Encode the primary IFP packet */
    if (encode_open_type(s, buf, buflen, &len, ifp, ifp_len) < 0)
        return -1;
 
    /* Encode the appropriate type of error recovery information */
    switch (s->error_correction_scheme)
    {
    case UDPTL_ERROR_CORRECTION_NONE:
        /* Encode the error recovery type */
        buf[len++] = 0x00;
        /* The number of entries will always be zero, so it is pointless allowing
           for the fragmented case here. */
        encode_length(buf, &len, 0);
        break;
    case UDPTL_ERROR_CORRECTION_REDUNDANCY:
        /* Encode the error recovery type */
        buf[len++] = 0x00;
        if (s->tx_seq_no > s->error_correction_entries)
            entries = s->error_correction_entries;
        else
            entries = s->tx_seq_no;
        /* The number of entries will always be small, so it is pointless allowing
           for the fragmented case here. */
        encode_length(buf, &len, entries);
        /* Encode the elements */
        for (i = 0; i < entries; i++) {
            j = (entry - i - 1) & UDPTL_BUF_MASK;
            if (encode_open_type(s, buf, buflen, &len, s->tx[j].buf, s->tx[j].buf_len) < 0) {
                ast_debug(1, "UDPTL (%s): Encoding failed at i=%d, j=%d\n",
                      LOG_TAG(s), i, j);
                return -1;
            }
        }
        break;
    case UDPTL_ERROR_CORRECTION_FEC:
        span = s->error_correction_span;
        entries = s->error_correction_entries;
        if (seq < s->error_correction_span*s->error_correction_entries) {
            /* In the initial stages, wind up the FEC smoothly */
            entries = seq/s->error_correction_span;
            if (seq < s->error_correction_span)
                span = 0;
        }
        /* Encode the error recovery type */
        buf[len++] = 0x80;
        /* Span is defined as an unconstrained integer, which it dumb. It will only
           ever be a small value. Treat it as such. */
        buf[len++] = 1;
        buf[len++] = span;
        /* The number of entries is defined as a length, but will only ever be a small
           value. Treat it as such. */
        buf[len++] = entries;
        for (m = 0; m < entries; m++) {
            /* Make an XOR'ed entry the maximum length */
            limit = (entry + m) & UDPTL_BUF_MASK;
            high_tide = 0;
            for (i = (limit - span*entries) & UDPTL_BUF_MASK; i != limit; i = (i + entries) & UDPTL_BUF_MASK) {
                if (high_tide < s->tx[i].buf_len) {
                    for (j = 0; j < high_tide; j++)
                        fec[j] ^= s->tx[i].buf[j];
                    for ( ; j < s->tx[i].buf_len; j++)
                        fec[j] = s->tx[i].buf[j];
                    high_tide = s->tx[i].buf_len;
                } else {
                    for (j = 0; j < s->tx[i].buf_len; j++)
                        fec[j] ^= s->tx[i].buf[j];
                }
            }
            if (encode_open_type(s, buf, buflen, &len, fec, high_tide) < 0)
                return -1;
        }
        break;
    }
 
    s->tx_seq_no++;
    return len;
}
 
int ast_udptl_fd(const struct ast_udptl *udptl)
{
    return udptl->fd;
}
 
void ast_udptl_set_data(struct ast_udptl *udptl, void *data)
{
    udptl->data = data;
}
 
void ast_udptl_set_callback(struct ast_udptl *udptl, ast_udptl_callback callback)
{
    udptl->callback = callback;
}
 
void ast_udptl_setnat(struct ast_udptl *udptl, int nat)
{
    udptl->nat = nat;
}
 
static int udptlread(int *id, int fd, short events, void *cbdata)
{
    struct ast_udptl *udptl = cbdata;
    struct ast_frame *f;
 
    if ((f = ast_udptl_read(udptl))) {
        if (udptl->callback)
            udptl->callback(udptl, f, udptl->data);
    }
    return 1;
}
 
struct ast_frame *ast_udptl_read(struct ast_udptl *udptl)
{
    int res;
    struct ast_sockaddr addr;
    uint8_t *buf;
 
    buf = udptl->rawdata + AST_FRIENDLY_OFFSET;
 
    /* Cache where the header will go */
    res = ast_recvfrom(udptl->fd,
            buf,
            sizeof(udptl->rawdata) - AST_FRIENDLY_OFFSET,
            0,
            &addr);
    if (res < 0) {
        if (errno != EAGAIN)
            ast_log(LOG_WARNING, "UDPTL (%s): read error: %s\n",
                LOG_TAG(udptl), strerror(errno));
        ast_assert(errno != EBADF);
        return &ast_null_frame;
    }
 
    /* Ignore if the other side hasn't been given an address yet. */
    if (ast_sockaddr_isnull(&udptl->them)) {
        return &ast_null_frame;
    }
 
    /*
     * If early media isn't turned on for the channel driver, it's going to
     * drop this frame.  By that time though, udptl has already incremented
     * the expected sequence number so if the CPE re-sends, the second frame
     * will be dropped as a dup even though the first frame never went through.
     * So we drop the frame here if the channel isn't up. 'tag' is set by the
     * channel drivers on T38_ENABLED or T38_PEER_REINVITE.
     */
    if (udptl->tag == NULL) {
        return &ast_null_frame;
    }
 
    if (udptl->nat) {
        /* Send to whoever sent to us */
        if (ast_sockaddr_cmp(&udptl->them, &addr)) {
            ast_sockaddr_copy(&udptl->them, &addr);
            ast_debug(1, "UDPTL (%s): NAT, Using address %s\n",
                  LOG_TAG(udptl), ast_sockaddr_stringify(&udptl->them));
        }
    }
 
    if (udptl_debug_test_addr(&addr)) {
        int seq_no;
 
        /* Decode sequence number just for verbose message. */
        if (res < 2) {
            /* Short packet. */
            seq_no = -1;
        } else {
            seq_no = (buf[0] << 8) | buf[1];
        }
 
        ast_verb(1, "UDPTL (%s): packet from %s (seq %d, len %d)\n",
            LOG_TAG(udptl), ast_sockaddr_stringify(&addr), seq_no, res);
    }
    if (udptl_rx_packet(udptl, buf, res) < 1) {
        return &ast_null_frame;
    }
 
    return &udptl->f[0];
}
 
static void calculate_local_max_datagram(struct ast_udptl *udptl)
{
    unsigned int new_max = 0;
 
    if (udptl->local_max_ifp == -1) {
        ast_log(LOG_WARNING, "UDPTL (%s): Cannot calculate local_max_datagram before local_max_ifp has been set.\n",
            LOG_TAG(udptl));
        udptl->local_max_datagram = -1;
        return;
    }
 
    /* calculate the amount of space required to receive an IFP
     * of the maximum size supported by the application/endpoint
     * that we are delivering them to (local endpoint), and add
     * the amount of space required to support the selected
     * error correction mode
     */
    switch (udptl->error_correction_scheme) {
    case UDPTL_ERROR_CORRECTION_NONE:
        /* need room for sequence number, length indicator, redundancy
         * indicator and following length indicator
         */
        new_max = 5 + udptl->local_max_ifp;
        break;
    case UDPTL_ERROR_CORRECTION_REDUNDANCY:
        /* need room for sequence number, length indicators, plus
         * room for up to 3 redundancy packets
         */
        new_max = 5 + udptl->local_max_ifp + 2 + (3 * udptl->local_max_ifp);
        break;
    case UDPTL_ERROR_CORRECTION_FEC:
        /* need room for sequence number, length indicators and a
         * a single IFP of the maximum size expected
         */
        new_max = 5 + udptl->local_max_ifp + 4 + udptl->local_max_ifp;
        break;
    }
    /* add 5% extra space for insurance, but no larger than LOCAL_FAX_MAX_DATAGRAM */
    udptl->local_max_datagram = MIN(new_max * 1.05, LOCAL_FAX_MAX_DATAGRAM);
}
 
static void calculate_far_max_ifp(struct ast_udptl *udptl)
{
    unsigned new_max = 0;
 
    if (udptl->far_max_datagram == -1) {
        ast_log(LOG_WARNING, "UDPTL (%s): Cannot calculate far_max_ifp before far_max_datagram has been set.\n",
            LOG_TAG(udptl));
        udptl->far_max_ifp = -1;
        return;
    }
 
    /* the goal here is to supply the local endpoint (application
     * or bridged channel) a maximum IFP value that will allow it
     * to effectively and efficiently transfer image data at its
     * selected bit rate, taking into account the selected error
     * correction mode, but without overrunning the far endpoint's
     * datagram buffer. this is complicated by the fact that some
     * far endpoints send us bogus (small) max datagram values,
     * which would result in either buffer overrun or no error
     * correction. we try to accomodate those, but if the supplied
     * value is too small to do so, we'll emit warning messages and
     * the user will have to use configuration options to override
     * the max datagram value supplied by the far endpoint.
     */
    switch (udptl->error_correction_scheme) {
    case UDPTL_ERROR_CORRECTION_NONE:
        /* need room for sequence number, length indicator, redundancy
         * indicator and following length indicator
         */
        new_max = udptl->far_max_datagram - 5;
        break;
    case UDPTL_ERROR_CORRECTION_REDUNDANCY:
        /* for this case, we'd like to send as many error correction entries
         * as possible (up to the number we're configured for), but we'll settle
         * for sending fewer if the configured number would cause the
         * calculated max IFP to be too small for effective operation
         *
         * need room for sequence number, length indicators and the
         * configured number of redundant packets
         *
         * note: we purposely don't allow error_correction_entries to drop to
         * zero in this loop; we'd rather send smaller IFPs (and thus reduce
         * the image data transfer rate) than sacrifice redundancy completely
         */
        for (;;) {
            new_max = (udptl->far_max_datagram - 8) / (udptl->error_correction_entries + 1);
 
            if ((new_max < 80) && (udptl->error_correction_entries > 1)) {
                /* the max ifp is not large enough, subtract an
                 * error correction entry and calculate again
                 * */
                --udptl->error_correction_entries;
            } else {
                break;
            }
        }
        break;
    case UDPTL_ERROR_CORRECTION_FEC:
        /* need room for sequence number, length indicators and a
         * a single IFP of the maximum size expected
         */
        new_max = (udptl->far_max_datagram - 10) / 2;
        break;
    }
    /* subtract 5% of space for insurance */
    udptl->far_max_ifp = new_max * 0.95;
}
 
enum ast_t38_ec_modes ast_udptl_get_error_correction_scheme(const struct ast_udptl *udptl)
{
    return udptl->error_correction_scheme;
}
 
void ast_udptl_set_error_correction_scheme(struct ast_udptl *udptl, enum ast_t38_ec_modes ec)
{
    udptl->error_correction_scheme = ec;
    switch (ec) {
    case UDPTL_ERROR_CORRECTION_FEC:
        udptl->error_correction_scheme = UDPTL_ERROR_CORRECTION_FEC;
        if (udptl->error_correction_entries == 0) {
            udptl->error_correction_entries = 3;
        }
        if (udptl->error_correction_span == 0) {
            udptl->error_correction_span = 3;
        }
        break;
    case UDPTL_ERROR_CORRECTION_REDUNDANCY:
        udptl->error_correction_scheme = UDPTL_ERROR_CORRECTION_REDUNDANCY;
        if (udptl->error_correction_entries == 0) {
            udptl->error_correction_entries = 3;
        }
        break;
    default:
        /* nothing to do */
        break;
    };
    /* reset calculated values so they'll be computed again */
    udptl->local_max_datagram = -1;
    udptl->far_max_ifp = -1;
}
 
void ast_udptl_set_local_max_ifp(struct ast_udptl *udptl, unsigned int max_ifp)
{
    /* make sure max_ifp is a positive value since a cast will take place when
     * when setting local_max_ifp */
    if ((signed int) max_ifp > 0) {
        udptl->local_max_ifp = max_ifp;
        /* reset calculated values so they'll be computed again */
        udptl->local_max_datagram = -1;
    }
}
 
unsigned int ast_udptl_get_local_max_datagram(struct ast_udptl *udptl)
{
    if (udptl->local_max_datagram == -1) {
        calculate_local_max_datagram(udptl);
    }
 
    /* this function expects a unsigned value in return. */
    if (udptl->local_max_datagram < 0) {
        return 0;
    }
    return udptl->local_max_datagram;
}
 
void ast_udptl_set_far_max_datagram(struct ast_udptl *udptl, unsigned int max_datagram)
{
    if (!max_datagram || (max_datagram > FAX_MAX_DATAGRAM_LIMIT)) {
        udptl->far_max_datagram = DEFAULT_FAX_MAX_DATAGRAM;
    } else {
        udptl->far_max_datagram = max_datagram;
    }
    /* reset calculated values so they'll be computed again */
    udptl->far_max_ifp = -1;
}
 
unsigned int ast_udptl_get_far_max_datagram(const struct ast_udptl *udptl)
{
    if (udptl->far_max_datagram < 0) {
        return 0;
    }
    return udptl->far_max_datagram;
}
 
unsigned int ast_udptl_get_far_max_ifp(struct ast_udptl *udptl)
{
    if (udptl->far_max_ifp == -1) {
        calculate_far_max_ifp(udptl);
    }
 
    if (udptl->far_max_ifp < 0) {
        return 0;
    }
    return udptl->far_max_ifp;
}
 
struct ast_udptl *ast_udptl_new_with_bindaddr(struct ast_sched_context *sched, struct io_context *io, int callbackmode, struct ast_sockaddr *addr)
{
    struct ast_udptl *udptl;
    int x;
    int startplace;
    int i;
    RAII_VAR(struct udptl_config *, cfg, ao2_global_obj_ref(globals), ao2_cleanup);
 
    if (!cfg || !cfg->general) {
        ast_log(LOG_ERROR, "Could not access global udptl options!\n");
        return NULL;
    }
 
    if (!(udptl = ast_calloc(1, sizeof(*udptl)))) {
        return NULL;
    }
 
    udptl->error_correction_span = cfg->general->fecspan;
    udptl->error_correction_entries = cfg->general->fecentries;
 
    udptl->far_max_datagram = -1;
    udptl->far_max_ifp = -1;
    udptl->local_max_ifp = -1;
    udptl->local_max_datagram = -1;
 
    for (i = 0; i <= UDPTL_BUF_MASK; i++) {
        udptl->rx[i].buf_len = -1;
        udptl->tx[i].buf_len = -1;
    }
 
    if ((udptl->fd = ast_socket_nonblock(ast_sockaddr_is_ipv6(addr) ?
                    AF_INET6 : AF_INET, SOCK_DGRAM, 0)) < 0) {
        ast_free(udptl);
        ast_log(LOG_WARNING, "Unable to allocate socket: %s\n", strerror(errno));
        return NULL;
    }
 
#ifdef SO_NO_CHECK
    if (cfg->general->nochecksums)
        setsockopt(udptl->fd, SOL_SOCKET, SO_NO_CHECK, &cfg->general->nochecksums, sizeof(cfg->general->nochecksums));
#endif
 
    /* Find us a place */
    x = (cfg->general->start == cfg->general->end) ? cfg->general->start : (ast_random() % (cfg->general->end - cfg->general->start)) + cfg->general->start;
    if (cfg->general->use_even_ports && (x & 1)) {
        ++x;
    }
    startplace = x;
    for (;;) {
        ast_sockaddr_copy(&udptl->us, addr);
        ast_sockaddr_set_port(&udptl->us, x);
        if (ast_bind(udptl->fd, &udptl->us) == 0) {
            break;
        }
        if (errno != EADDRINUSE && errno != EACCES) {
            ast_log(LOG_WARNING, "Unexpected bind error: %s\n", strerror(errno));
            close(udptl->fd);
            ast_free(udptl);
            return NULL;
        }
        if (cfg->general->use_even_ports) {
            x += 2;
        } else {
            ++x;
        }
        if (x > cfg->general->end)
            x = cfg->general->start;
        if (x == startplace) {
            ast_log(LOG_WARNING, "No UDPTL ports remaining\n");
            close(udptl->fd);
            ast_free(udptl);
            return NULL;
        }
    }
    if (io && sched && callbackmode) {
        /* Operate this one in a callback mode */
        udptl->sched = sched;
        udptl->io = io;
        udptl->ioid = ast_io_add(udptl->io, udptl->fd, udptlread, AST_IO_IN, udptl);
    }
 
    return udptl;
}
 
void ast_udptl_set_tag(struct ast_udptl *udptl, const char *format, ...)
{
    va_list ap;
 
    ast_free(udptl->tag);
    udptl->tag = NULL;
    va_start(ap, format);
    if (ast_vasprintf(&udptl->tag, format, ap) == -1) {
        udptl->tag = NULL;
    }
    va_end(ap);
}
 
int ast_udptl_setqos(struct ast_udptl *udptl, unsigned int tos, unsigned int cos)
{
    return ast_set_qos(udptl->fd, tos, cos, "UDPTL");
}
 
void ast_udptl_set_peer(struct ast_udptl *udptl, const struct ast_sockaddr *them)
{
    ast_sockaddr_copy(&udptl->them, them);
}
 
void ast_udptl_get_peer(const struct ast_udptl *udptl, struct ast_sockaddr *them)
{
    ast_sockaddr_copy(them, &udptl->them);
}
 
void ast_udptl_get_us(const struct ast_udptl *udptl, struct ast_sockaddr *us)
{
    ast_sockaddr_copy(us, &udptl->us);
}
 
void ast_udptl_stop(struct ast_udptl *udptl)
{
    ast_sockaddr_setnull(&udptl->them);
}
 
void ast_udptl_destroy(struct ast_udptl *udptl)
{
    if (udptl->ioid)
        ast_io_remove(udptl->io, udptl->ioid);
    if (udptl->fd > -1)
        close(udptl->fd);
    if (udptl->tag)
        ast_free(udptl->tag);
    ast_free(udptl);
}
 
int ast_udptl_write(struct ast_udptl *s, struct ast_frame *f)
{
    unsigned int seq;
    unsigned int len = f->datalen;
    /* if no max datagram size is provided, use default value */
    const int bufsize = (s->far_max_datagram > 0) ? s->far_max_datagram : DEFAULT_FAX_MAX_DATAGRAM;
    uint8_t buf[bufsize];
 
    memset(buf, 0, sizeof(buf));
 
    /* If we have no peer, return immediately */
    if (ast_sockaddr_isnull(&s->them)) {
        return 0;
    }
 
    /* If there is no data length, return immediately */
    if (f->datalen == 0)
        return 0;
 
    if ((f->frametype != AST_FRAME_MODEM) ||
        (f->subclass.integer != AST_MODEM_T38)) {
        ast_log(LOG_WARNING, "UDPTL (%s): UDPTL can only send T.38 data.\n",
            LOG_TAG(s));
        return -1;
    }
 
    if (len > s->far_max_ifp) {
        ast_log(LOG_WARNING,
            "UDPTL (%s): UDPTL asked to send %u bytes of IFP when far end only prepared to accept %d bytes; data loss will occur."
            "You may need to override the T38FaxMaxDatagram value for this endpoint in the channel driver configuration.\n",
            LOG_TAG(s), len, s->far_max_ifp);
        len = s->far_max_ifp;
    }
 
    /* Save seq_no for debug output because udptl_build_packet increments it */
    seq = s->tx_seq_no & 0xFFFF;
 
    /* Cook up the UDPTL packet, with the relevant EC info. */
    len = udptl_build_packet(s, buf, sizeof(buf), f->data.ptr, len);
 
    if ((signed int) len > 0 && !ast_sockaddr_isnull(&s->them)) {
        if (ast_sendto(s->fd, buf, len, 0, &s->them) < 0) {
            ast_log(LOG_NOTICE, "UDPTL (%s): Transmission error to %s: %s\n",
                LOG_TAG(s), ast_sockaddr_stringify(&s->them), strerror(errno));
        }
        if (udptl_debug_test_addr(&s->them)) {
            ast_verb(1, "UDPTL (%s): packet to %s (seq %u, len %u)\n",
                LOG_TAG(s), ast_sockaddr_stringify(&s->them), seq, len);
        }
    }
 
    return 0;
}
 
static char *handle_cli_udptl_set_debug(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
    switch (cmd) {
    case CLI_INIT:
        e->command = "udptl set debug {on|off|ip}";
        e->usage =
            "Usage: udptl set debug {on|off|ip host[:port]}\n"
            "       Enable or disable dumping of UDPTL packets.\n"
            "       If ip is specified, limit the dumped packets to those to and from\n"
            "       the specified 'host' with optional port.\n";
        return NULL;
    case CLI_GENERATE:
        return NULL;
    }
 
    if (a->argc < 4 || a->argc > 5)
        return CLI_SHOWUSAGE;
 
    if (a->argc == 4) {
        if (!strncasecmp(a->argv[3], "on", 2)) {
            udptldebug = 1;
            memset(&udptldebugaddr, 0, sizeof(udptldebugaddr));
            ast_cli(a->fd, "UDPTL Debugging Enabled\n");
        } else if (!strncasecmp(a->argv[3], "off", 3)) {
            udptldebug = 0;
            ast_cli(a->fd, "UDPTL Debugging Disabled\n");
        } else {
            return CLI_SHOWUSAGE;
        }
    } else {
        struct ast_sockaddr *addrs;
        if (strncasecmp(a->argv[3], "ip", 2))
            return CLI_SHOWUSAGE;
        if (!ast_sockaddr_resolve(&addrs, a->argv[4], 0, 0)) {
            return CLI_SHOWUSAGE;
        }
        ast_sockaddr_copy(&udptldebugaddr, &addrs[0]);
            ast_cli(a->fd, "UDPTL Debugging Enabled for IP: %s\n", ast_sockaddr_stringify(&udptldebugaddr));
        udptldebug = 1;
        ast_free(addrs);
    }
 
    return CLI_SUCCESS;
}
 
static char *handle_cli_show_config(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
    RAII_VAR(struct udptl_config *, cfg, NULL, ao2_cleanup);
 
    switch (cmd) {
    case CLI_INIT:
        e->command = "udptl show config";
        e->usage =
            "Usage: udptl show config\n"
            "       Display UDPTL configuration options\n";
        return NULL;
    case CLI_GENERATE:
        return NULL;
    }
 
    if (!(cfg = ao2_global_obj_ref(globals))) {
        return CLI_FAILURE;
    }
 
    ast_cli(a->fd, "UDPTL Global options\n");
    ast_cli(a->fd, "--------------------\n");
    ast_cli(a->fd, "udptlstart:      %u\n", cfg->general->start);
    ast_cli(a->fd, "udptlend:        %u\n", cfg->general->end);
    ast_cli(a->fd, "udptlfecentries: %u\n", cfg->general->fecentries);
    ast_cli(a->fd, "udptlfecspan:    %u\n", cfg->general->fecspan);
    ast_cli(a->fd, "use_even_ports:  %s\n", AST_CLI_YESNO(cfg->general->use_even_ports));
    ast_cli(a->fd, "udptlchecksums: %s\n", AST_CLI_YESNO(!cfg->general->nochecksums));
 
    return CLI_SUCCESS;
}
 
static struct ast_cli_entry cli_udptl[] = {
    AST_CLI_DEFINE(handle_cli_udptl_set_debug, "Enable/Disable UDPTL debugging"),
    AST_CLI_DEFINE(handle_cli_show_config, "Show UDPTL config options"),
};
 
static void udptl_config_destructor(void *obj)
{
    struct udptl_config *cfg = obj;
    ao2_cleanup(cfg->general);
}
 
static void *udptl_snapshot_alloc(void)
{
    struct udptl_config *cfg;
 
    if (!(cfg = ao2_alloc(sizeof(*cfg), udptl_config_destructor))) {
        return NULL;
    }
    if (!(cfg->general = ao2_alloc(sizeof(*cfg->general), NULL))) {
        ao2_ref(cfg, -1);
        return NULL;
    }
 
    return cfg;
}
 
static int removed_options_handler(const struct aco_option *opt, struct ast_variable *var, void *obj)
{
    if (!strcasecmp(var->name, "t38faxudpec")) {
        ast_log(LOG_WARNING, "t38faxudpec in udptl.conf is no longer supported.\n");
    } else if (!strcasecmp(var->name, "t38faxmaxdatagram")) {
        ast_log(LOG_WARNING, "t38faxmaxdatagram in udptl.conf is no longer supported; value is now supplied by T.38 applications.\n");
    }
    return 0;
}
 
static void __ast_udptl_reload(int reload)
{
    if (aco_process_config(&cfg_info, reload) == ACO_PROCESS_ERROR) {
        if (!reload) {
            RAII_VAR(struct udptl_config *, udptl_cfg, udptl_snapshot_alloc(), ao2_cleanup);
 
            if (aco_set_defaults(&general_option, "general", udptl_cfg->general)) {
                ast_log(LOG_ERROR, "Failed to load udptl.conf and failed to initialize defaults.\n");
                return;
            }
 
            ast_log(LOG_NOTICE, "Could not load udptl config; using defaults\n");
            ao2_global_obj_replace_unref(globals, udptl_cfg);
        }
    }
}
 
static int udptl_pre_apply_config(void) {
    struct udptl_config *cfg = aco_pending_config(&cfg_info);
 
    if (!cfg->general) {
        return -1;
    }
 
#ifndef SO_NO_CHECK
    if (cfg->general->nochecksums) {
        ast_log(LOG_WARNING, "Disabling UDPTL checksums is not supported on this operating system!\n");
        cfg->general->nochecksums = 0;
    }
#endif
 
    /* Fix up any global config values that we can handle before replacing the config */
    if (cfg->general->use_even_ports && (cfg->general->start & 1)) {
        ++cfg->general->start;
        ast_log(LOG_NOTICE, "Odd numbered udptlstart specified but use_even_ports enabled. udptlstart is now %u\n", cfg->general->start);
    }
    if (cfg->general->start > cfg->general->end) {
        ast_log(LOG_WARNING, "Unreasonable values for UDPTL start/end ports; defaulting to %s-%s.\n", __stringify(DEFAULT_UDPTLSTART), __stringify(DEFAULT_UDPTLEND));
        cfg->general->start = DEFAULT_UDPTLSTART;
        cfg->general->end = DEFAULT_UDPTLEND;
    }
    if (cfg->general->use_even_ports && (cfg->general->end & 1)) {
        --cfg->general->end;
        ast_log(LOG_NOTICE, "Odd numbered udptlend specified but use_even_ports enabled. udptlend is now %u\n", cfg->general->end);
    }
 
    return 0;
}
 
static int reload_module(void)
{
    __ast_udptl_reload(1);
 
    return 0;
}
 
/*!
 * \internal
 * \brief Clean up resources on Asterisk shutdown
 */
static int unload_module(void)
{
    ast_cli_unregister_multiple(cli_udptl, ARRAY_LEN(cli_udptl));
    ao2_t_global_obj_release(globals, "Unref udptl global container in shutdown");
    aco_info_destroy(&cfg_info);
 
    return 0;
}
 
static int load_module(void)
{
    if (aco_info_init(&cfg_info)) {
        return AST_MODULE_LOAD_FAILURE;
    }
 
    aco_option_register(&cfg_info, "udptlstart", ACO_EXACT, general_options, __stringify(DEFAULT_UDPTLSTART),
        OPT_UINT_T, PARSE_IN_RANGE | PARSE_DEFAULT,
        FLDSET(struct udptl_global_options, start), DEFAULT_UDPTLSTART, 1024, 65535);
 
    aco_option_register(&cfg_info, "udptlend", ACO_EXACT, general_options, __stringify(DEFAULT_UDPTLEND),
        OPT_UINT_T, PARSE_IN_RANGE | PARSE_DEFAULT,
        FLDSET(struct udptl_global_options, end), DEFAULT_UDPTLEND, 1024, 65535);
 
    aco_option_register(&cfg_info, "udptlfecentries", ACO_EXACT, general_options, NULL,
        OPT_UINT_T, PARSE_IN_RANGE | PARSE_RANGE_DEFAULTS,
        FLDSET(struct udptl_global_options, fecentries), 1, MAX_FEC_ENTRIES);
 
    aco_option_register(&cfg_info, "udptlfecspan", ACO_EXACT, general_options, NULL,
        OPT_UINT_T, PARSE_IN_RANGE | PARSE_RANGE_DEFAULTS,
        FLDSET(struct udptl_global_options, fecspan), 1, MAX_FEC_SPAN);
 
    aco_option_register(&cfg_info, "udptlchecksums", ACO_EXACT, general_options, "yes",
        OPT_BOOL_T, 0, FLDSET(struct udptl_global_options, nochecksums));
 
    aco_option_register(&cfg_info, "use_even_ports", ACO_EXACT, general_options, "no",
        OPT_BOOL_T, 1, FLDSET(struct udptl_global_options, use_even_ports));
 
    aco_option_register_custom(&cfg_info, "t38faxudpec", ACO_EXACT, general_options, NULL, removed_options_handler, 0);
    aco_option_register_custom(&cfg_info, "t38faxmaxdatagram", ACO_EXACT, general_options, NULL, removed_options_handler, 0);
 
    __ast_udptl_reload(0);
 
    ast_cli_register_multiple(cli_udptl, ARRAY_LEN(cli_udptl));
 
    return AST_MODULE_LOAD_SUCCESS;
}
 
AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_GLOBAL_SYMBOLS | AST_MODFLAG_LOAD_ORDER, "UDPTL",
    .support_level = AST_MODULE_SUPPORT_CORE,
    .load = load_module,
    .unload = unload_module,
    .reload = reload_module,
    .load_pri = AST_MODPRI_CORE,
    .requires = "extconfig",
);