[FFmpeg-devel] [PATCH 2/3] libavformat/dashdec: Fix for ticket 6658 (Dash demuxer segfault)

刘歧 lq at chinaffmpeg.org
Wed Jan 17 05:39:03 EET 2018


> On 17 Jan 2018, at 11:00, Colin NG <colin_ng at hotmail.com> wrote:
> 
> - Add function 'resolve_content_path' to propagate the baseURL from upper level nodes.
> * if no baseURL is available, the path of mpd file will be set as the baseURL.
> - Remove checking for newly established connection.
> - Establish the communication protocol in each connection rather than applying one protocol to all connection.
> ---
> libavformat/dashdec.c | 128 +++++++++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 115 insertions(+), 13 deletions(-)
> 
> diff --git a/libavformat/dashdec.c b/libavformat/dashdec.c
> index 67a92d6..1d520d4 100644
> --- a/libavformat/dashdec.c
> +++ b/libavformat/dashdec.c
> @@ -149,6 +149,11 @@ typedef struct DASHContext {
>     AVDictionary *avio_opts;
> } DASHContext;
> 
> +static int ishttp(char *url) {
> +    const char *proto_name = avio_find_protocol_name(url);
> +    return av_strstart(proto_name, "http", NULL);
> +}
> +
> static uint64_t get_current_time_in_sec(void)
> {
>     return  av_gettime() / 1000000;
> @@ -420,7 +425,8 @@ static int open_url(AVFormatContext *s, AVIOContext **pb, const char *url,
>     else if (strcmp(proto_name, "file") || !strncmp(url, "file,", 5))
>         return AVERROR_INVALIDDATA;
> 
> -    ret = s->io_open(s, pb, url, AVIO_FLAG_READ, &tmp);
> +    av_freep(pb);
> +    ret = avio_open2(pb, url, AVIO_FLAG_READ, c->interrupt_callback, &tmp);
>     if (ret >= 0) {
>         // update cookies on http response with setcookies.
>         char *new_cookies = NULL;
> @@ -564,6 +570,7 @@ static struct fragment * get_Fragment(char *range)
>         seg->url_offset = strtoll(str_offset, NULL, 10);
>         seg->size = strtoll(str_end_offset, NULL, 10) - seg->url_offset;
>     }
> +
>     return seg;
> }
> 
> @@ -591,6 +598,7 @@ static int parse_manifest_segmenturlnode(AVFormatContext *s, struct representati
>                                                      rep_id_val,
>                                                      rep_bandwidth_val,
>                                                      initialization_val);
> +
>             if (!rep->init_section->url) {
>                 av_free(rep->init_section);
>                 xmlFree(initialization_val);
> @@ -665,6 +673,105 @@ static int parse_manifest_segmenttimeline(AVFormatContext *s, struct representat
>     return 0;
> }
> 
> +static int resolve_content_path(AVFormatContext *s, const char *url, xmlNodePtr *baseurl_nodes, int n_baseurl_nodes) {
> +
> +    char *tmp_str = NULL;
> +    char *path = NULL;
> +    char *mpdName = NULL;
> +    xmlNodePtr node = NULL;
> +    char *baseurl = NULL;
> +    char *root_url = NULL;
> +    char *text = NULL;
> +
> +    int isRootHttp = 0;
> +    char token ='/';
> +    int start =  0;
> +    int rootId = 0;
> +    int updated = 0;
> +    int size = 0;
> +    int i;
> +    int max_url_size = strlen(url);
> +
> +    for (i = n_baseurl_nodes-1; i >= 0 ; i--) {
> +        text = xmlNodeGetContent(baseurl_nodes[i]);
> +        if (!text)
> +            continue;
> +        max_url_size += strlen(text);
> +        if (ishttp(text)) {
> +            xmlFree(text);
> +            break;
> +        }
> +        xmlFree(text);
> +    }
> +
> +    text = av_mallocz(max_url_size);
> +    if (!text) {
> +        updated = AVERROR(ENOMEM);
> +        goto end;
> +    }
> +    av_strlcpy(text, url, strlen(url)+1);
> +    while (mpdName = av_strtok(text, "/", &text))  {
> +        size = strlen(mpdName);
> +    }
> +
> +    path = av_mallocz(max_url_size);
> +    tmp_str = av_mallocz(max_url_size);
> +    if (!tmp_str || !path) {
> +        updated = AVERROR(ENOMEM);
> +        goto end;
> +    }
> +
> +    av_strlcpy (path, url, strlen(url) - size + 1);
> +    for (rootId = n_baseurl_nodes - 1; rootId > 0; rootId --) {
> +        if (!(node = baseurl_nodes[rootId])) {
> +            continue;
> +        }
> +        if (ishttp(xmlNodeGetContent(node))) {
> +            break;
> +        }
> +    }
> +
> +    node = baseurl_nodes[rootId];
> +    baseurl = xmlNodeGetContent(node);
> +    root_url = (av_strcasecmp(baseurl, "")) ? baseurl : path;
> +    if (node) {
> +        xmlNodeSetContent(node, root_url);
> +        updated = 1;
> +    }
> +
> +    size = strlen(root_url);
> +    isRootHttp = ishttp(root_url);
> +
> +    if (root_url[size - 1] != token) {
> +        av_strlcat(root_url, "/", size + 2);
> +        size += 2;
> +    }
> +
> +    for (i = 0; i < n_baseurl_nodes; ++i) {
> +        if (i == rootId) {
> +            continue;
> +        }
> +        text = xmlNodeGetContent(baseurl_nodes[i]);
> +        if (text) {
> +            memset(tmp_str, 0, strlen(tmp_str));
> +            if (!ishttp(text) && isRootHttp) {
> +                av_strlcpy(tmp_str, root_url, size + 1);
> +            }
> +            start = (text[0] == token);
> +            av_strlcat(tmp_str, text + start, max_url_size);
> +            xmlNodeSetContent(baseurl_nodes[i], tmp_str);
> +            updated = 1;
> +            xmlFree(text);
> +        }
> +    }
> +
> +end:
> +    av_free(path);
> +    av_free(tmp_str);
> +    return updated;
> +
> +}
> +
> static int parse_manifest_representation(AVFormatContext *s, const char *url,
>                                          xmlNodePtr node,
>                                          xmlNodePtr adaptionset_node,
> @@ -727,6 +834,10 @@ static int parse_manifest_representation(AVFormatContext *s, const char *url,
>         baseurl_nodes[2] = adaptionset_baseurl_node;
>         baseurl_nodes[3] = representation_baseurl_node;
> 
> +        ret = resolve_content_path(s, url, baseurl_nodes, 4);
> +        if (ret == AVERROR(ENOMEM) || (ret == 0)) {
> +            goto end;
> +        }
>         if (representation_segmenttemplate_node || fragment_template_node || period_segmenttemplate_node) {
>             fragment_timeline_node = NULL;
>             fragment_templates_tab[0] = representation_segmenttemplate_node;
> @@ -1038,6 +1149,9 @@ static int parse_manifest(AVFormatContext *s, const char *url, AVIOContext *in)
>         }
> 
>         mpd_baseurl_node = find_child_node_by_name(node, "BaseURL");
> +        if (!mpd_baseurl_node) {
> +            mpd_baseurl_node = xmlNewNode(NULL, "BaseURL");
> +        }
> 
>         // at now we can handle only one period, with the longest duration
>         node = xmlFirstElementChild(node);
> @@ -1405,18 +1519,6 @@ static int open_input(DASHContext *c, struct representation *pls, struct fragmen
>         goto cleanup;
>     }
> 
> -    /* Seek to the requested position. If this was a HTTP request, the offset
> -     * should already be where want it to, but this allows e.g. local testing
> -     * without a HTTP server. */
> -    if (!ret && seg->url_offset) {
> -        int64_t seekret = avio_seek(pls->input, seg->url_offset, SEEK_SET);
> -        if (seekret < 0) {
> -            av_log(pls->parent, AV_LOG_ERROR, "Unable to seek to offset %"PRId64" of DASH fragment '%s'\n", seg->url_offset, seg->url);
> -            ret = (int) seekret;
> -            ff_format_io_close(pls->parent, &pls->input);
> -        }
> -    }
> -
> cleanup:
>     av_dict_free(&opts);
>     pls->cur_seg_offset = 0;
> -- 
> 2.7.4
> 


Patchset LGTM, but there have some compiling warning:

liuqideMacBook-Pro:dash liuqi$ make
CC	libavformat/dashdec.o
src/libavformat/dashdec.c:1530:9: warning: variable 'ret' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
    if (!url) {
        ^~~~
src/libavformat/dashdec.c:1554:12: note: uninitialized use occurs here
    return ret;
           ^~~
src/libavformat/dashdec.c:1530:5: note: remove the 'if' if its condition is always false
    if (!url) {
    ^~~~~~~~~~~
src/libavformat/dashdec.c:1528:12: note: initialize the variable 'ret' to silence this warning
    int ret;
           ^
            = 0
1 warning generated.
AR	libavformat/libavformat.a
LD	ffmpeg_g




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