core-legacy/endpoints/api_v1_controllers_discover.c

#include <cJSON.h>
#include <constants.h>
#include <endpoints/api_v1_controllers.h>
#include <models/controller.h>
#include <logger.h>
#include <mpack.h>

#define DISCOVERY_TIMEOUT_MS 2000

typedef enum
{
    DISCOVERY_MAPPING_ID = 0,
    DISCOVERY_MAPPING_NAME = 1,
    DISCOVERY_MAPPING_COMMAND_PORT = 2,
    DISCOVERY_MAPPING_RELAY_COUNT = 3,
} discovery_mapping_t;

static int
bind_tcp_server(const char *addr, const char *port, int max_client_backlog)
{
    struct addrinfo hints, *res;
    int fd;
    int status;

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE;

    if ((status = getaddrinfo(addr, port, &hints, &res)) != 0)
    {
        LOG_ERROR("error getting address info: %s\n", gai_strerror(status));
    }

    fd = socket(res->ai_family, res->ai_socktype, res->ai_protocol);

    if ((status = bind(fd, res->ai_addr, res->ai_addrlen)) == -1)
    {
        LOG_ERROR("error binding socket: %s\n", status);
        freeaddrinfo(res);
        return -1;
    }

    if ((status = listen(fd, max_client_backlog)) == -1)
    {
        LOG_ERROR("error setting up listener: %s\n", status);
        freeaddrinfo(res);
        return -1;
    }

    freeaddrinfo(res);

    return fd;
}

static int
get_server_port(int fd)
{
    if(fd == -1)
    {
        return -1;
    }
    struct sockaddr_in sin;
    socklen_t addr_len = sizeof(sin);
    if(getsockname(fd, (struct sockaddr *)&sin, &addr_len) == 0)
    {
        return ntohs(sin.sin_port);
    }
    return -1;
}

static int
send_udp_broadcast(const char *addr, uint16_t port, void *message, size_t length)
{
    struct sockaddr_in their_addr;
    int fd;

    if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
    {
        LOG_ERROR("error creating socket\n");
        return -1;
    }

    int broadcast = 1;
    if (setsockopt(fd, SOL_SOCKET, SO_BROADCAST, &broadcast, sizeof broadcast) < 0)
    {
        LOG_ERROR("error setting broadcast\n");
        return -1;
    }

    memset(&their_addr, 0, sizeof(their_addr));
    their_addr.sin_family = AF_INET;
    their_addr.sin_port = htons(port);
    their_addr.sin_addr.s_addr = inet_addr(addr);

    if(sendto(fd, message, length, 0, (struct sockaddr *)&their_addr, sizeof(their_addr)) < 0)
    {
        LOG_ERROR("error sending broadcast (%d): '%s'\n", errno, strerror(errno));
        return -1;
    }
    close(fd);

    return 0;
}

void
api_v1_controllers_discover_POST(struct mg_connection *c, endpoint_args_t *args, struct http_message *hm)
{
    int discover_server_socket = bind_tcp_server("0.0.0.0", "0", 20);
    int discover_server_port = get_server_port(discover_server_socket);

    if(discover_server_port == -1)
    {
        mg_send_head(c, 500, 2, "Content-Type: application/json\r\n" STANDARD_HEADERS);
        mg_printf(c, "[]");
        return;
    }

    int16_t payload[1];
    payload[0] = discover_server_port;

    if(send_udp_broadcast("255.255.255.255", global_config.discovery_port, payload, sizeof(payload)) < 0)
    {
        mg_send_head(c, 500, 2, "Content-Type: application/json\r\n" STANDARD_HEADERS);
        mg_printf(c, "[]");
        return;
    }

    struct sockaddr_storage their_addr;
    socklen_t addr_size;
    int client_fd, s_ret;
    fd_set accept_fds;
    struct timeval timeout;

    uint8_t discover_answer_buf[1];

    controller_t **known_controllers = controller_get_all();

    while(true)
    {
        addr_size = sizeof(their_addr);

        FD_ZERO(&accept_fds);
        FD_SET(discover_server_socket, &accept_fds); // NOLINT(hicpp-signed-bitwise)

        timeout.tv_sec = DISCOVERY_TIMEOUT_MS / 1000;
        timeout.tv_usec = (DISCOVERY_TIMEOUT_MS % 1000) * 1000;

        s_ret = select(discover_server_socket + 1, &accept_fds, NULL, NULL, &timeout);
        if(s_ret == 0)
        {
            break;
        }
        else
        {
            if((client_fd = accept(discover_server_socket, (struct sockaddr *) &their_addr, &addr_size)) < 0)
            {
                LOG_ERROR("error accepting client %s\n", strerror(errno));
                continue;
            }

            size_t payload_length;

            if(recv(client_fd, &payload_length, sizeof(payload_length), 0) <= 0)
            {
                LOG_ERROR("error receiving header from client\n");
                continue;
            }

            char *answer_payload = (char*)malloc((payload_length));
            ssize_t bytes_transferred;

            if((bytes_transferred = recv(client_fd, answer_payload, payload_length, 0)) <= 0)
            {
                LOG_ERROR("error receiving payload from client\n");
                continue;
            }

            struct sockaddr_in addr;
            socklen_t client_addr_size = sizeof(struct sockaddr_in);
            if(getpeername(client_fd, (struct sockaddr *)&addr, &client_addr_size) != 0)
            {

                LOG_ERROR("error receiving payload from client\n");
                continue;
            }

            uuid_t discovered_id;

            mpack_tree_t tree;
            mpack_tree_init_data(&tree, answer_payload, payload_length);
            mpack_tree_parse(&tree);
            mpack_node_t root = mpack_tree_root(&tree);

            memcpy(discovered_id, mpack_node_data(mpack_node_map_uint(root, DISCOVERY_MAPPING_ID)), sizeof(uuid_t));

            uint16_t discovered_command_port = mpack_node_u16(mpack_node_map_uint(root, DISCOVERY_MAPPING_COMMAND_PORT));
            uint8_t discovered_relay_count = mpack_node_u8(mpack_node_map_uint(root, DISCOVERY_MAPPING_RELAY_COUNT));
            const char *discovered_name = mpack_node_str(mpack_node_map_uint(root, DISCOVERY_MAPPING_NAME));
            size_t discovered_name_len = mpack_node_strlen(mpack_node_map_uint(root, DISCOVERY_MAPPING_NAME));

            if(discovered_name_len > MAX_NAME_LENGTH)
            {
                discovered_name_len = MAX_NAME_LENGTH;
            }

            bool found_discovered_in_list = 0;

            for(int i = 0; known_controllers[i] != NULL; i++)
            {
                if(!found_discovered_in_list)
                {
                    if(uuid_compare(known_controllers[i]->uid, discovered_id) == 0)
                    {
                        known_controllers[i]->active = 1;
                        strncpy(known_controllers[i]->name, discovered_name, discovered_name_len);
                        known_controllers[i]->name[MAX_NAME_LENGTH] = '\0';
                        known_controllers[i]->port = discovered_command_port;
                        known_controllers[i]->relay_count = discovered_relay_count;

                        controller_save(known_controllers[i]);
                        controller_free(known_controllers[i]);

                        found_discovered_in_list = 1;
                        known_controllers[i] = known_controllers[i + 1];
                    }
                }
                else
                {
                    known_controllers[i] = known_controllers[i + 1];
                }
            }

            if(!found_discovered_in_list)
            {
                controller_t *discovered_controller = malloc(sizeof(controller_t));
                discovered_controller->id = 0;
                strcpy(discovered_controller->ip, inet_ntoa(addr.sin_addr));
                memcpy(discovered_controller->uid, discovered_id, sizeof(uuid_t));
                strncpy(discovered_controller->name, discovered_name, MAX_NAME_LENGTH);
                discovered_controller->name[MAX_NAME_LENGTH] = '\0';
                discovered_controller->relay_count = discovered_relay_count;
                discovered_controller->port = discovered_command_port;
                discovered_controller->active = 1;

                controller_save(discovered_controller);
            }
            mpack_tree_destroy(&tree);
            free(answer_payload);

            discover_answer_buf[0] = 0; // TODO add discovery return codes
            send(client_fd, discover_answer_buf, sizeof(uint8_t), 0);
            close(client_fd);
        }
    }
    for(int i = 0; known_controllers[i] != NULL; i++)
    {
        known_controllers[i]->active = false;
        controller_save(known_controllers[i]);
        LOG_DEBUG("lost: %s\n", known_controllers[i]->name);
    }
    controller_free_list(known_controllers);

    api_v1_controllers_GET(c, args, hm);
}