path: root/tinyrtc.c

/**
 * WebRTC implementation for tiny devices
 *
 * Copyright (c) 2022 Chris Hiszpanski. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 * 4. This software may not be used for commercial purposes. For a commercial
 *    license, contact the copyright holder.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 */

#include <ifaddrs.h>                    // freeifaddrs, getifaddrs
#include <stdbool.h>
#include <stdio.h>                      // snprintf
#include <string.h>                     // memset
#include <unistd.h>                     // close

#include <arpa/inet.h>
#include <net/if.h>
#include <netinet/in.h>
#include <sys/socket.h>

#include "tinyrtc.h"


///  OPAQUE TYPE DEFINITIONS  ////////////////////////////////////////////////

struct rtc_peer_connection {
    bool active;

    char offer[TINYRTC_MAX_SDP_SIZE];
    char answer[TINYRTC_MAX_SDP_SIZE];

    /* local description */
    const char* ldesc;

    /* remote description */
    const char* rdesc;

    char l_ice_pwd[TINYRTC_MAX_ICE_PWD_SIZE];
    char l_ice_ufrag[TINYRTC_MAX_ICE_UFRAG_SIZE];

    /* onIceCandidate callback */
    rtc_on_ice_candidate* on_ice_candidate;
    void* on_ice_candidate_arg;

    /* tcp host candidate socket */
    int host_tcp_fd;
};


///  STATIC ALLOCATIONS  /////////////////////////////////////////////////////

static struct rtc_peer_connection
peer_connection_pool[TINYRTC_MAX_PEER_CONNECTIONS];


///  RTC PEER CONNECTION API  ////////////////////////////////////////////////

void rtc_init() {
    memset(peer_connection_pool, 0, sizeof(peer_connection_pool));
}

/**
 * Get host candidates
 *
 * \return 0 on success, -1 on error.
 */
static int get_host_candidates(struct rtc_peer_connection* pc) {
    struct ifaddrs *ifaddr, *ifa;
    socklen_t laddrlen;

    /* sanity check */
    if (!pc) return -1;

    /* create tcp socket */
    pc->host_tcp_fd = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (-1 == pc->host_tcp_fd) {
        return -1;
    }

    /* bind to arbitrary port */
    struct sockaddr_in laddr = {
        .sin_family = AF_INET,
        .sin_addr.s_addr = INADDR_ANY,
        .sin_port = 0,
    };
    if (-1 == bind(pc->host_tcp_fd, (struct sockaddr*)&laddr, sizeof(laddr))) {
        return -1;
    }
    laddrlen = sizeof(struct sockaddr_in);
    if (-1 == getsockname(pc->host_tcp_fd, (struct sockaddr *)&laddr, &laddrlen)) {
        return -1;
    }

    /* listen on socket */
    if (-1 == listen(pc->host_tcp_fd, 0)) {
        return -1;
    }

    /* get network interface addresses */
    if (-1 == getifaddrs(&ifaddr)) {
        return -1;
    }

    /* iterate over addresses */
    for (ifa = ifaddr; ifa; ifa = ifa->ifa_next) {
        if (!ifa->ifa_addr) continue;

        /* skip loopback interface addresses */
        if (IFF_LOOPBACK & ifa->ifa_flags) continue;

        if (AF_INET == ifa->ifa_addr->sa_family) {
            struct sockaddr_in *sa = (struct sockaddr_in*)ifa->ifa_addr;

            /* host tcp candidate */
            struct rtc_ice_candidate c = {
                .sdp_mid = "0",
                .sdp_mline_index = 0
            };
            snprintf(c.candidate, TINYRTC_MAX_ICE_CANDIDATE_SIZE,
                "candidate:2894319779 1 tcp 212260223 %s %d typ host tcptype passive",
                inet_ntoa(sa->sin_addr),
                laddr.sin_port); // XXXX

            /* callback */
            if (pc->on_ice_candidate) {
                pc->on_ice_candidate(c, pc->on_ice_candidate_arg);
            }
        }
    }

    freeifaddrs(ifaddr);

    return 0;
}

/**
 * Peer connection thread
 *
 * Each peer connection uses one background thread for stepping the ICE agent,
 * handling timeouts, and sending/receiving packets.
 *
 * \param arg[in] User-specified argument.
 *
 * \return NULL.
 */
static void* peer_connection_thread(void *arg) {
    return NULL;
}

struct rtc_peer_connection* rtc_peer_connection_create(struct rtc_configuration cfg) {
    struct rtc_peer_connection* pc = NULL;

    for (int i = 0; i < TINYRTC_MAX_PEER_CONNECTIONS; i++) {
        if (!peer_connection_pool[i].active) {
            memset(&peer_connection_pool[i], 0, sizeof(struct rtc_peer_connection));
            pc = &peer_connection_pool[i];
            break;
        }
    }

    return pc;
}

void rtc_peer_connection_destroy(struct rtc_peer_connection* pc)
{
    if (!pc) return;

    close(pc->host_tcp_fd);

    // XXX mark as available
}

int rtc_set_on_ice_candidate(struct rtc_peer_connection* pc,
        rtc_on_ice_candidate* cb, void* arg)
{
    if (!pc || !cb) return -1;

    pc->on_ice_candidate = cb;
    pc->on_ice_candidate_arg = arg;

    return 0;
}

int rtc_add_ice_candidate(struct rtc_peer_connection* pc,
        const struct rtc_ice_candidate c)
{
    return -1;
};

const char* rtc_create_answer(struct rtc_peer_connection* pc)
{
    unsigned char fp[32];

    snprintf(pc->l_ice_ufrag, TINYRTC_MAX_ICE_UFRAG_SIZE, "xxxx"); // XXX
    snprintf(pc->l_ice_pwd, TINYRTC_MAX_ICE_PWD_SIZE, "xxxxxxxxxxxxxxxxxxxxxx"); // XXX

    snprintf(pc->answer, TINYRTC_MAX_SDP_SIZE,
        "v=0\\r\\n"
        "o=- 2210401696197537454 2 IN IP4 127.0.0.1\\r\\n" // XXX
        "s=-\\r\\n"
        "u=https://liburtc.org/\\r\\n"
        "t=0 0\\r\\n"
        "a=group:BUNDLE 0\\r\\n"
        "a=msid-semantic: WMS\\r\\n"
        "m=video 9 UDP/TLS/RTP/SAVPF 98\\r\\n" // XXX
        "c=IN IP4 0.0.0.0\\r\\n"
        "a=rtcp:9 IN IP4 0.0.0.0\\r\\n"
        "a=ice-ufrag:%s\\r\\n"
        "a=ice-pwd:%s\\r\\n"
        "a=ice-options:trickle\\r\\n"
        "a=fingerprint:sha-256 "
            "%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:"
            "%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:"
            "%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:"
            "%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:%02hhX\\r\\n"
        "a=setup:passive\\r\\n"
        "a=mid:0\\r\\n"
        "a=sendonly\\r\\n"
        "a=rtcp-mux\\r\\n"
        "a=rtcp-rsize\\r\\n"
        "a=rtpmap:98 H264/90000\\r\\n"
        "a=rtcp-fb:98 nack\\r\\n"
        "a=rtcp-fb:98 nack pli\\r\\n"
        "a=fmtp:98 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f\\r\\n",
        pc->l_ice_ufrag,
        pc->l_ice_pwd,
        fp[ 0], fp[ 1], fp[ 2], fp[ 3], fp[ 4], fp[ 5], fp[ 6], fp[ 7],
        fp[ 8], fp[ 9], fp[10], fp[11], fp[12], fp[13], fp[14], fp[15],
        fp[16], fp[17], fp[18], fp[19], fp[20], fp[21], fp[22], fp[23],
        fp[24], fp[25], fp[26], fp[27], fp[28], fp[29], fp[30], fp[31]
    );

    return pc->answer;
};

int rtc_set_local_description(struct rtc_peer_connection* pc, const char* sdp)
{
    pc->ldesc = sdp;
    get_host_candidates(pc);
    return -1;
};

int rtc_set_remote_description(struct rtc_peer_connection* pc, const char* sdp)
{
    pc->rdesc = sdp;
    return -1;
};

/* vim: set et ts=4 sw=4 : */