Function ice_create_request

libavformat/whip.c:1053–1135

* Creates and marshals an ICE binding request packet. * * This function creates and marshals an ICE binding request packet. The function only * generates the username attribute and does not include goog-network-info, * use-candidate. However, some of these attributes may be added in the future. * * @param s Pointer to the AVFormatContext * @param buf Pointer to memory buffer to store the re

 * @return Returns 0 if successful or AVERROR_xxx if an error occurs.
 */
static int ice_create_request(AVFormatContext *s, uint8_t *buf, int buf_size, int *request_size)
{
    int ret, size, crc32;
    char username[128];
    AVIOContext *pb = NULL;
    AVHMAC *hmac = NULL;
    WHIPContext *whip = s->priv_data;

    pb = avio_alloc_context(buf, buf_size, 1, NULL, NULL, NULL, NULL);
    if (!pb)
        return AVERROR(ENOMEM);

    hmac = av_hmac_alloc(AV_HMAC_SHA1);
    if (!hmac) {
        ret = AVERROR(ENOMEM);
        goto end;
    }

    /* Write 20 bytes header */
    avio_wb16(pb, 0x0001); /* STUN binding request */
    avio_wb16(pb, 0);      /* length */
    avio_wb32(pb, STUN_MAGIC_COOKIE); /* magic cookie */
    avio_wb32(pb, av_lfg_get(&whip->rnd)); /* transaction ID */
    avio_wb32(pb, av_lfg_get(&whip->rnd)); /* transaction ID */
    avio_wb32(pb, av_lfg_get(&whip->rnd)); /* transaction ID */

    /* The username is the concatenation of the two ICE ufrag */
    ret = snprintf(username, sizeof(username), "%s:%s", whip->ice_ufrag_remote, whip->ice_ufrag_local);
    if (ret <= 0 || ret >= sizeof(username)) {
        av_log(whip, AV_LOG_ERROR, "Failed to build username %s:%s, max=%zu, ret=%d\n",
            whip->ice_ufrag_remote, whip->ice_ufrag_local, sizeof(username), ret);
        ret = AVERROR(EIO);
        goto end;
    }

    /* Write the username attribute */
    avio_wb16(pb, STUN_ATTR_USERNAME); /* attribute type username */
    avio_wb16(pb, ret); /* size of username */
    avio_write(pb, username, ret); /* bytes of username */
    ffio_fill(pb, 0, (4 - (ret % 4)) % 4); /* padding */

    /* Write the use-candidate attribute */
    avio_wb16(pb, STUN_ATTR_USE_CANDIDATE); /* attribute type use-candidate */
    avio_wb16(pb, 0); /* size of use-candidate */

    avio_wb16(pb, STUN_ATTR_PRIORITY);
    avio_wb16(pb, 4);
    avio_wb32(pb, STUN_HOST_CANDIDATE_PRIORITY);

    avio_wb16(pb, STUN_ATTR_ICE_CONTROLLING);
    avio_wb16(pb, 8);
    avio_wb64(pb, whip->ice_tie_breaker);

    /* Build and update message integrity */
    avio_wb16(pb, STUN_ATTR_MESSAGE_INTEGRITY); /* attribute type message integrity */
    avio_wb16(pb, 20); /* size of message integrity */
    ffio_fill(pb, 0, 20); /* fill with zero to directly write and skip it */
    size = avio_tell(pb);