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DEF CON 17 Audio and Video now available!

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  • YenTheFirst
    replied
    Re: DEF CON 17 Audio and Video now available!

    As of tonight, I'm experiencing the same issue as before - no communication at all with the download server. no ACK.

    Leave a comment:


  • TheCotMan
    replied
    Re: DEF CON 17 Audio and Video now available!

    Originally posted by Deviant Ollam View Post
    oh, and thanks for the good explanation about HTTP transfer standards, cot!
    Thanks. :-)

    Originally posted by Dark Tangent View Post
    I'll check into content-length to make sure there is no strange stripping going on. Thanks Cot! you rule.
    I had another thought on what could cause the length to be removed:

    If there is a filter between the server and the client that is compressing (or trying to compress) the video, audio, rar-files, iso, etc., then it would also, likely, compress content as a stream, and as a result, not have a total size of content being transmitted over http/https before it starts transmitting it. (Again, for efficiency, the server would not want to pre-compress and store an entire file before transmitting it.)

    Usually, when compression is enabled for web servers to web browsers, a selection list of either extensions or MIME-types is provided to either specify:
    * Items that should be compressed, with default compression disabled (or)
    * What should NOT be compressed, with everything else being compressed.

    Most of the time, web and network admins will disable compression for any 8-bit content, but leave it enabled for 7-bit content (as text such as .txt, .html, .js, and css.) This is especially important when looking to serve video, which is usually compressed with much *better compression than an inline gzip compression done with an emphasis for speed and low CPU use.

    But is this the case?

    wget --header="accept-encoding: gzip" http://media.defcon.org/dc-17/video/...d%20Slides.m4v

    vs.

    wget http://media.defcon.org/dc-17/video/...d%20Slides.m4v

    And, what-do-you-know? When I specify compression as "ok" with wget, I get no time estimate for when it will be completed, but when I don't support compression, I see a time estimate.

    Solution? Disable compression for 8-bit content, or at least for video, and audio, because you are probably not saving much, but you are taxing your CPU more than you need to.

    Leave a comment:


  • TheCotMan
    replied
    Re: DEF CON 17 Audio and Video now available!

    I had some free time and checked this latest problem out.

    If I visit the links from the dc17 archives, they are https, and have spaces in the filenames and path. Once I click the link, it appears as though my access to the media server is black-holed (or may not have worked to begin with.)

    Once I changed my IP address, I converted a link like:

    https://media.defcon.org/dc-17/video/DEFCON 17 Hacking Conference Presentation By Dark Tangent - Closing Ceremonies - Video and Slides.m4v

    to

    https://media.defcon.org/dc-17/vide%...d%20Slides.m4v

    and then change the "https" to "http", I was able to download the file.

    After doing that, a request with wget works from a new IP address that never tried to download the file over https from media.defcon.org, and I was able to download a video.

    Additionally, I see a time estimate for how long it will take to download the file from wget.

    As a work-around until the firewall admin (or maybe media server admin) resolves this problem, why don't you try the following to see if you are at least able to download content.

    You'll want to use a new IP address, or wait a while (half an hour, day, few days) for your IP to no longer be filtered.

    Once your IP address works, you should be able to visit media . defcon . org using http (not https) (h t t p : / / m e d i a . d e f c o n . o r g /)(no spaces) and see a web page load. Until that works, there is no point in going on from here. If you can see that, then proceed to the next step:

    I wrote a one-liner to download the media archive list from https://www.defcon.org/html/links/dc...7-archive.html yank out the links to media.defcon.org, and then replace ' ' with '%20' and convert 'https' to 'http' and then generate a new web page in html with links to the links as html-parsed links:

    https://forum.defcon.org/ical/links-dc17.html
    (I'll leave this up for a few days, and then remove it.)

    See if they work for you.

    Be careful. You probably only want to download one at a time. I don't know if a firewall rule might view an attempt to download too many at the same time as a false-positive for a DoS and then blackhole you. (No. I am not the admin of media.defcon.org or the firewall.)

    Feedback on how this works or doesn't may help the firewall admin, or media server admin diagnose this problem.
    Last edited by TheCotMan; February 11, 2010, 10:28.

    Leave a comment:


  • theprez98
    replied
    Re: DEF CON 17 Audio and Video now available!

    Originally posted by Deviant Ollam View Post
    well, i've now at least managed to find the links (on an archive section of the web site, not that RSS feed linked earlier in this thread) but all that i try appear to fail. they don't 404... they just never start the download.
    This is the same situation I have seen; no 404s, just downloads that never start.

    Leave a comment:


  • Deviant Ollam
    replied
    Re: DEF CON 17 Audio and Video now available!

    Originally posted by Dark Tangent View Post
    I'll check into content-length to make sure there is no strange stripping going on.
    thanks, man! and, for what it's worth, they all appear to be downloading well for me now. i'm not certain why some of them experienced truncation problems in the past.

    so pleased to have these talks now... i can't remember the last time i got to see a talk in-person at DEFCON other than ones i was giving.

    Leave a comment:


  • The Dark Tangent
    replied
    Re: DEF CON 17 Audio and Video now available!

    Originally posted by Deviant Ollam View Post
    interestingly, all of the files i had tried queueing up seemed to eventually download now that i've come back and sat down again. the first few files i'm checking out seem to be alright. i don't know what could have changed, but i'm thrilled!

    they're in M4V format, heh, so it might be a while before i can get some of these on to the Traveling Terabyte as i had hoped... but whatcha gonna do. i'm just so glad to have them working and i'll re-process them later on.

    oh, and thanks for the good explanation about HTTP transfer standards, cot!
    Deviant, they were originally .mov file extensions until I renamed the to better describe what they are.

    I'll check into content-length to make sure there is no strange stripping going on. Thanks Cot! you rule.

    Leave a comment:


  • Deviant Ollam
    replied
    Re: DEF CON 17 Audio and Video now available!

    interestingly, all of the files i had tried queueing up seemed to eventually download now that i've come back and sat down again. the first few files i'm checking out seem to be alright. i don't know what could have changed, but i'm thrilled!

    they're in M4V format, heh, so it might be a while before i can get some of these on to the Traveling Terabyte as i had hoped... but whatcha gonna do. i'm just so glad to have them working and i'll re-process them later on.

    oh, and thanks for the good explanation about HTTP transfer standards, cot!

    Leave a comment:


  • TheCotMan
    replied
    Re: DEF CON 17 Audio and Video now available!

    Originally posted by Deviant Ollam View Post
    what is the cause for some HTTP traffic to easily identify itself to a browser client in terms of file size when other traffic does not?
    Part of HTTP when transmitting content like files after a request is received, is a statement of size/length before content is transmitted, which describes how much data is coming.

    When the length is removed, then the browser has no idea how much data is coming, and you'll no longer see an ever increasing bar, but more often a "Cylon-like" game of pong between the left and right side of a small rectangle that would otherwise provide a bar graph.

    it's frustrating for Firefox to simply tell me "i'm downloading this stuff... but i have no idea when it might be done" etc etc.
    It is a common side-effect when dealing with a query against a DB, or when a CGI provides dynamic content based on live data and/or items in a request. As a result, the CGI or server script (for efficiency) does not store all of the data to be transmitted locally (so that it can compute the size of data to be transmitted) before transmitting it.

    It is unusual for static content to not specify size/length, because it is so easy to determine, with very little overhead. I don't know how the media server works for its content. If it is just serving flat-files, then it is more likely that the size/lenth is being stripped from the HTTP between the server and your client.

    HTH

    Citation:
    14.13 Content-Length
    http://www.faqs.org/rfcs/rfc2616.html

    Originally posted by rfc
    Applications SHOULD use this field to indicate the transfer-length of the message-body, unless this is prohibited by the rules in section 4.4.
    Of course, this is "SHOULD" not MUST, so it is not required, just strongly suggested.
    Last edited by TheCotMan; February 9, 2010, 22:13.

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  • Deviant Ollam
    replied
    Re: DEF CON 17 Audio and Video now available!

    Originally posted by theprez98 View Post
    I too have had no such luck.

    Just tried about four different talks at random, none of the video links worked.
    well, i've now at least managed to find the links (on an archive section of the web site, not that RSS feed linked earlier in this thread) but all that i try appear to fail. they don't 404... they just never start the download.

    UPDATE: found a couple that do download... but i think i ran into this before... the download never completes and the resulting file is not playable. what is the cause for some HTTP traffic to easily identify itself to a browser client in terms of file size when other traffic does not?

    it's frustrating for Firefox to simply tell me "i'm downloading this stuff... but i have no idea when it might be done" etc etc.

    Leave a comment:


  • theprez98
    replied
    Re: DEF CON 17 Audio and Video now available!

    Originally posted by Deviant Ollam View Post
    well, i like to think i'm pretty on the ball, and i have never had any success with getting the videos.
    I too have had no such luck.

    Just tried about four different talks at random, none of the video links worked.
    Last edited by theprez98; February 9, 2010, 12:18.

    Leave a comment:


  • Deviant Ollam
    replied
    Re: DEF CON 17 Audio and Video now available!

    Originally posted by xboxbman View Post
    they all seem to be working now
    well, i like to think i'm pretty on the ball, and i have never had any success with getting the videos. the links above in the first post lead to an RSS feed page.

    that page lists a number of talks. there are links in here, in bold and highlighted in blue. these links, however, are just to basic HTML pages... the speakers page, as it turns out. this is just another list of speakers and talks. there do not seem to be any links to other content, video files, etc.

    Leave a comment:


  • YenTheFirst
    replied
    Re: DEF CON 17 Audio and Video now available!

    I've noticed it comes and goes - it usually downloads fine, but sometimes it doesn't work at all.

    A bit more info on what I did one time, from what I could recall wireshark showing:
    1) I tried to download a file with wget.
    2) wget would send TCP SYN requests from a particular local port. It would retry that connection 5 times, before giving up and trying a new connection, on a different local port. I didn't time it, but according to linux docs, this should correspond to about 180 seconds. (no response from the server was had)
    3) wget would try again on a new port, and again, until I killed the program.
    4) about 600 seconds later, I'd receive from a TCP rst for the first port from media.defcon.org

    My theory at this point (don't quite know how things work server side), was that the server was slow for whatever reason, and was getting mad at my client trying a new port when it still had the older one 'open'.
    so, I bumped up the # of TCP retries (/proc/sys/net/ipv4/tcp_syn_retries on linux), to 255, to give the server more time to respond before trying on a new port.
    I was able to get an ACK and download the file.

    I didn't save the capture log at the time, but if you want, I can save it if the problem comes up again.

    Leave a comment:


  • xboxbman
    replied
    Re: DEF CON 17 Audio and Video now available!

    Originally posted by xboxbman View Post
    Is there any other source for these videos? Say a torrent perhaps? I get timeout from the archive, and from wget as well. I find some videos on emule, but they are not transferring at all.
    nevermind. hours after making this post, they all seem to be working now. I swear they weren't before though. Honest!

    Leave a comment:


  • xboxbman
    replied
    Re: DEF CON 17 Audio and Video now available!

    Is there any other source for these videos? Say a torrent perhaps? I get timeout from the archive, and from wget as well. I find some videos on emule, but they are not transferring at all.

    Leave a comment:


  • The Dark Tangent
    replied
    Re: DEF CON 17 Audio and Video now available!

    Originally posted by YenTheFirst View Post
    Even this far out from the initial launching of the archives, I still have trouble downloading the files. Most attempts are met with a TCP RST - I don't even get any HTTP response.

    edit: also, this RST is about 600 seconds removed from the original SYN
    edit2: manually bumping up the number of TCP SYN retries got it to download.
    YTF,

    600 is important for me to debug. Thank you!

    Leave a comment:

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