hdhomerun_discover.c

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/*
 * hdhomerun_discover.c
 *
 * Copyright © 2006-2007 Silicondust USA Inc. <www.silicondust.com>.
 *
 * This library is free software; you can redistribute it and/or 
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
 * 
 * As a special exception to the GNU Lesser General Public License,
 * you may link, statically or dynamically, an application with a
 * publicly distributed version of the Library to produce an
 * executable file containing portions of the Library, and
 * distribute that executable file under terms of your choice,
 * without any of the additional requirements listed in clause 4 of
 * the GNU Lesser General Public License.
 * 
 * By "a publicly distributed version of the Library", we mean
 * either the unmodified Library as distributed by Silicondust, or a
 * modified version of the Library that is distributed under the
 * conditions defined in the GNU Lesser General Public License.
 */

#include "hdhomerun.h"

#if defined(__CYGWIN__) || defined(__WINDOWS__)
#include <windows.h>
#include <iphlpapi.h>
#define USE_IPHLPAPI 1
#else
#include <net/if.h>
#include <sys/ioctl.h>
#ifndef _SIZEOF_ADDR_IFREQ
#define _SIZEOF_ADDR_IFREQ(x) sizeof(x)
#endif
#endif

#define HDHOMERUN_DISOCVER_MAX_SOCK_COUNT 16

struct hdhomerun_discover_sock_t {
        int sock;
        uint32_t local_ip;
        uint32_t subnet_mask;
};

struct hdhomerun_discover_t {
        struct hdhomerun_discover_sock_t socks[HDHOMERUN_DISOCVER_MAX_SOCK_COUNT];
        unsigned int sock_count;
        struct hdhomerun_pkt_t tx_pkt;
        struct hdhomerun_pkt_t rx_pkt;
};

static bool_t hdhomerun_discover_sock_create(struct hdhomerun_discover_t *ds, uint32_t local_ip, uint32_t subnet_mask)
{
        if (ds->sock_count >= HDHOMERUN_DISOCVER_MAX_SOCK_COUNT) {
                return FALSE;
        }

        /* Create socket. */
        int sock = (int)socket(AF_INET, SOCK_DGRAM, 0);
        if (sock == -1) {
                return FALSE;
        }

        /* Set timeouts. */
        setsocktimeout(sock, SOL_SOCKET, SO_SNDTIMEO, 1000);
        setsocktimeout(sock, SOL_SOCKET, SO_RCVTIMEO, 1000);

        /* Allow broadcast. */
        int sock_opt = 1;
        setsockopt(sock, SOL_SOCKET, SO_BROADCAST, (char *)&sock_opt, sizeof(sock_opt));

        /* Bind socket. */
        struct sockaddr_in sock_addr;
        memset(&sock_addr, 0, sizeof(sock_addr));
        sock_addr.sin_family = AF_INET;
        sock_addr.sin_addr.s_addr = htonl(local_ip);
        sock_addr.sin_port = htons(0);
        if (bind(sock, (struct sockaddr *)&sock_addr, sizeof(sock_addr)) != 0) {
                close(sock);
                return FALSE;
        }

        /* Write sock entry. */
        struct hdhomerun_discover_sock_t *dss = &ds->socks[ds->sock_count++];
        dss->sock = sock;
        dss->local_ip = local_ip;
        dss->subnet_mask = subnet_mask;

        return TRUE;
}

#if defined(USE_IPHLPAPI)
static void hdhomerun_discover_sock_detect(struct hdhomerun_discover_t *ds)
{
        PIP_ADAPTER_INFO pAdapterInfo = (IP_ADAPTER_INFO *)malloc(sizeof(IP_ADAPTER_INFO));
        ULONG ulOutBufLen = sizeof(IP_ADAPTER_INFO);

        DWORD Ret = GetAdaptersInfo(pAdapterInfo, &ulOutBufLen);
        if (Ret != NO_ERROR) {
                free(pAdapterInfo);
                if (Ret != ERROR_BUFFER_OVERFLOW) {
                        return;
                }
                pAdapterInfo = (IP_ADAPTER_INFO *)malloc(ulOutBufLen); 
                Ret = GetAdaptersInfo(pAdapterInfo, &ulOutBufLen);
                if (Ret != NO_ERROR) {
                        free(pAdapterInfo);
                        return;
                }
        }

        PIP_ADAPTER_INFO pAdapter = pAdapterInfo;
        while (pAdapter) {
                IP_ADDR_STRING *pIPAddr = &pAdapter->IpAddressList;
                while (pIPAddr) {
                        uint32_t local_ip = ntohl(inet_addr(pIPAddr->IpAddress.String));
                        uint32_t mask = ntohl(inet_addr(pIPAddr->IpMask.String));

                        if (local_ip == 0) {
                                pIPAddr = pIPAddr->Next;
                                continue;
                        }

                        hdhomerun_discover_sock_create(ds, local_ip, mask);
                        pIPAddr = pIPAddr->Next;
                }

                pAdapter = pAdapter->Next;
        }

        free(pAdapterInfo);
}

#else

static void hdhomerun_discover_sock_detect(struct hdhomerun_discover_t *ds)
{
        int fd = socket(AF_INET, SOCK_DGRAM, 0);
        if (fd == -1) {
                return;
        }

        struct ifconf ifc;
        uint8_t buf[8192];
        ifc.ifc_len = sizeof(buf);
        ifc.ifc_buf = (char *)buf;

        memset(buf, 0, sizeof(buf));

        if (ioctl(fd, SIOCGIFCONF, &ifc) != 0) {
                close(fd);
                return;
        }

        uint8_t *ptr = (uint8_t *)ifc.ifc_req;
        uint8_t *end = (uint8_t *)&ifc.ifc_buf[ifc.ifc_len];

        while (ptr <= end) {
                struct ifreq *ifr = (struct ifreq *)ptr;
                ptr += _SIZEOF_ADDR_IFREQ(*ifr);

                if (ioctl(fd, SIOCGIFADDR, ifr) != 0) {
                        continue;
                }
                struct sockaddr_in *addr_in = (struct sockaddr_in *)&(ifr->ifr_addr);
                uint32_t local_ip = ntohl(addr_in->sin_addr.s_addr);
                if (local_ip == 0) {
                        continue;
                }

                if (ioctl(fd, SIOCGIFNETMASK, ifr) != 0) {
                        continue;
                }
                struct sockaddr_in *mask_in = (struct sockaddr_in *)&(ifr->ifr_addr);
                uint32_t mask = ntohl(mask_in->sin_addr.s_addr);

                hdhomerun_discover_sock_create(ds, local_ip, mask);
        }
}
#endif

static struct hdhomerun_discover_t *hdhomerun_discover_create(void)
{
        struct hdhomerun_discover_t *ds = (struct hdhomerun_discover_t *)calloc(1, sizeof(struct hdhomerun_discover_t));
        if (!ds) {
                return NULL;
        }

        /* Create a routable socket. */
        if (!hdhomerun_discover_sock_create(ds, 0, 0)) {
                free(ds);
                return NULL;
        }

        /* Detect & create local sockets. */
        hdhomerun_discover_sock_detect(ds);

        /* Success. */
        return ds;
}

static void hdhomerun_discover_destroy(struct hdhomerun_discover_t *ds)
{
        unsigned int i;
        for (i = 0; i < ds->sock_count; i++) {
                struct hdhomerun_discover_sock_t *dss = &ds->socks[i];
                close(dss->sock);
        }

        free(ds);
}

static bool_t hdhomerun_discover_send_internal(struct hdhomerun_discover_t *ds, struct hdhomerun_discover_sock_t *dss, uint32_t target_ip, uint32_t device_type, uint32_t device_id)
{
        struct hdhomerun_pkt_t *tx_pkt = &ds->tx_pkt;
        hdhomerun_pkt_reset(tx_pkt);

        hdhomerun_pkt_write_u8(tx_pkt, HDHOMERUN_TAG_DEVICE_TYPE);
        hdhomerun_pkt_write_var_length(tx_pkt, 4);
        hdhomerun_pkt_write_u32(tx_pkt, device_type);
        hdhomerun_pkt_write_u8(tx_pkt, HDHOMERUN_TAG_DEVICE_ID);
        hdhomerun_pkt_write_var_length(tx_pkt, 4);
        hdhomerun_pkt_write_u32(tx_pkt, device_id);
        hdhomerun_pkt_seal_frame(tx_pkt, HDHOMERUN_TYPE_DISCOVER_REQ);

        struct sockaddr_in sock_addr;
        memset(&sock_addr, 0, sizeof(sock_addr));
        sock_addr.sin_family = AF_INET;
        sock_addr.sin_addr.s_addr = htonl(target_ip);
        sock_addr.sin_port = htons(HDHOMERUN_DISCOVER_UDP_PORT);

        int length = (int)(tx_pkt->end - tx_pkt->start);
        if (sendto(dss->sock, (char *)tx_pkt->start, length, 0, (struct sockaddr *)&sock_addr, sizeof(sock_addr)) != length) {
                return FALSE;
        }

        return TRUE;
}

static bool_t hdhomerun_discover_send_wildcard_ip(struct hdhomerun_discover_t *ds, uint32_t device_type, uint32_t device_id)
{
        bool_t result = FALSE;

        /*
         * Send subnet broadcast using each local ip socket.
         * This will work with multiple separate 169.254.x.x interfaces.
         */
        unsigned int i;
        for (i = 1; i < ds->sock_count; i++) {
                struct hdhomerun_discover_sock_t *dss = &ds->socks[i];
                uint32_t target_ip = dss->local_ip | ~dss->subnet_mask;
                result |= hdhomerun_discover_send_internal(ds, dss, target_ip, device_type, device_id);
        }

        /*
         * If no local ip sockets then fall back to sending a global broadcast letting the OS choose the interface.
         */
        if (!result) {
                struct hdhomerun_discover_sock_t *dss = &ds->socks[0];
                result = hdhomerun_discover_send_internal(ds, dss, 0xFFFFFFFF, device_type, device_id);
        }

        return result;
}

static bool_t hdhomerun_discover_send_target_ip(struct hdhomerun_discover_t *ds, uint32_t target_ip, uint32_t device_type, uint32_t device_id)
{
        bool_t result = FALSE;

        /*
         * Send targeted packet from any local ip that is in the same subnet.
         * This will work with multiple separate 169.254.x.x interfaces.
         */
        unsigned int i;
        for (i = 1; i < ds->sock_count; i++) {
                struct hdhomerun_discover_sock_t *dss = &ds->socks[i];
                if ((target_ip & dss->subnet_mask) != (dss->local_ip & dss->subnet_mask)) {
                        continue;
                }

                result |= hdhomerun_discover_send_internal(ds, dss, target_ip, device_type, device_id);
        }

        /*
         * If target IP does not match a local subnet then fall back to letting the OS choose the gateway interface.
         */
        if (!result) {
                struct hdhomerun_discover_sock_t *dss = &ds->socks[0];
                result = hdhomerun_discover_send_internal(ds, dss, target_ip, device_type, device_id);
        }

        return result;
}

static bool_t hdhomerun_discover_send(struct hdhomerun_discover_t *ds, uint32_t target_ip, uint32_t device_type, uint32_t device_id)
{
        if (target_ip != 0) {
                return hdhomerun_discover_send_target_ip(ds, target_ip, device_type, device_id);
        }

        return hdhomerun_discover_send_wildcard_ip(ds, device_type, device_id);
}

static int hdhomerun_discover_recv_internal(struct hdhomerun_discover_t *ds, struct hdhomerun_discover_sock_t *dss, struct hdhomerun_discover_device_t *result)
{
        struct hdhomerun_pkt_t *rx_pkt = &ds->rx_pkt;
        hdhomerun_pkt_reset(rx_pkt);

        struct sockaddr_in sock_addr;
        memset(&sock_addr, 0, sizeof(sock_addr));
        socklen_t sockaddr_size = sizeof(sock_addr);

        int rx_length = recvfrom(dss->sock, (char *)rx_pkt->end, (int)(rx_pkt->limit - rx_pkt->end), 0, (struct sockaddr *)&sock_addr, &sockaddr_size);
        if (rx_length <= 0) {
                /* Don't return error - windows machine on VPN can sometimes cause a sock error here but otherwise works. */
                return 0;
        }
        rx_pkt->end += rx_length;

        uint16_t type;
        if (hdhomerun_pkt_open_frame(rx_pkt, &type) <= 0) {
                return 0;
        }
        if (type != HDHOMERUN_TYPE_DISCOVER_RPY) {
                return 0;
        }

        result->ip_addr = ntohl(sock_addr.sin_addr.s_addr);
        result->device_type = 0;
        result->device_id = 0;

        while (1) {
                uint8_t tag;
                size_t len;
                uint8_t *next = hdhomerun_pkt_read_tlv(rx_pkt, &tag, &len);
                if (!next) {
                        break;
                }

                switch (tag) {
                case HDHOMERUN_TAG_DEVICE_TYPE:
                        if (len != 4) {
                                break;
                        }
                        result->device_type = hdhomerun_pkt_read_u32(rx_pkt);
                        break;

                case HDHOMERUN_TAG_DEVICE_ID:
                        if (len != 4) {
                                break;
                        }
                        result->device_id = hdhomerun_pkt_read_u32(rx_pkt);
                        break;

                default:
                        break;
                }

                rx_pkt->pos = next;
        }

        return 1;
}

static int hdhomerun_discover_recv(struct hdhomerun_discover_t *ds, struct hdhomerun_discover_device_t *result)
{
        struct timeval t;
        t.tv_sec = 0;
        t.tv_usec = 250000;

        fd_set readfds;
        FD_ZERO(&readfds);
        int max_sock = -1;

        unsigned int i;
        for (i = 0; i < ds->sock_count; i++) {
                struct hdhomerun_discover_sock_t *dss = &ds->socks[i];
                FD_SET(dss->sock, &readfds);
                if (dss->sock > max_sock) {
                        max_sock = dss->sock;
                }
        }

        if (select(max_sock+1, &readfds, NULL, NULL, &t) < 0) {
                return -1;
        }

        for (i = 0; i < ds->sock_count; i++) {
                struct hdhomerun_discover_sock_t *dss = &ds->socks[i];
                if (!FD_ISSET(dss->sock, &readfds)) {
                        continue;
                }

                if (hdhomerun_discover_recv_internal(ds, dss, result) <= 0) {
                        continue;
                }

                return 1;
        }

        return 0;
}

static struct hdhomerun_discover_device_t *hdhomerun_discover_find_in_list(struct hdhomerun_discover_device_t result_list[], int count, uint32_t ip_addr)
{
        int index;
        for (index = 0; index < count; index++) {
                struct hdhomerun_discover_device_t *result = &result_list[index];
                if (result->ip_addr == ip_addr) {
                        return result;
                }
        }

        return NULL;
}

static int hdhomerun_discover_find_devices_internal(struct hdhomerun_discover_t *ds, uint32_t target_ip, uint32_t device_type, uint32_t device_id, struct hdhomerun_discover_device_t result_list[], int max_count)
{
        int count = 0;
        int attempt;
        for (attempt = 0; attempt < 4; attempt++) {
                if (!hdhomerun_discover_send(ds, target_ip, device_type, device_id)) {
                        return -1;
                }

                uint64_t timeout = getcurrenttime() + 250;
                while (getcurrenttime() < timeout) {
                        struct hdhomerun_discover_device_t *result = &result_list[count];

                        int ret = hdhomerun_discover_recv(ds, result);
                        if (ret < 0) {
                                return -1;
                        }
                        if (ret == 0) {
                                continue;
                        }

                        /* Filter. */
                        if (device_type != HDHOMERUN_DEVICE_TYPE_WILDCARD) {
                                if (device_type != result->device_type) {
                                        continue;
                                }
                        }
                        if (device_id != HDHOMERUN_DEVICE_ID_WILDCARD) {
                                if (device_id != result->device_id) {
                                        continue;
                                }
                        }

                        /* Ensure not already in list. */
                        if (hdhomerun_discover_find_in_list(result_list, count, result->ip_addr)) {
                                continue;
                        }

                        /* Add to list. */
                        count++;
                        if (count >= max_count) {
                                return count;
                        }
                }
        }

        return count;
}

int hdhomerun_discover_find_devices_custom(uint32_t target_ip, uint32_t device_type, uint32_t device_id, struct hdhomerun_discover_device_t result_list[], int max_count)
{
        struct hdhomerun_discover_t *ds = hdhomerun_discover_create();
        if (!ds) {
                return -1;
        }

        int ret = hdhomerun_discover_find_devices_internal(ds, target_ip, device_type, device_id, result_list, max_count);

        hdhomerun_discover_destroy(ds);
        return ret;
}

bool_t hdhomerun_discover_validate_device_id(uint32_t device_id)
{
        static uint32_t lookup_table[16] = {0xA, 0x5, 0xF, 0x6, 0x7, 0xC, 0x1, 0xB, 0x9, 0x2, 0x8, 0xD, 0x4, 0x3, 0xE, 0x0};

        uint32_t checksum = 0;

        checksum ^= lookup_table[(device_id >> 28) & 0x0F];
        checksum ^= (device_id >> 24) & 0x0F;
        checksum ^= lookup_table[(device_id >> 20) & 0x0F];
        checksum ^= (device_id >> 16) & 0x0F;
        checksum ^= lookup_table[(device_id >> 12) & 0x0F];
        checksum ^= (device_id >> 8) & 0x0F;
        checksum ^= lookup_table[(device_id >> 4) & 0x0F];
        checksum ^= (device_id >> 0) & 0x0F;

        return (checksum == 0);
}

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