curl and/or libcurl related
Claes at foss-magasin.se asked a bunch of questions about me, my commitments within the FOSS community and related matters recently over email. This Swedish interview just now went public: Daniel Stenberg cURL, Rockbox och FOSS-Sthlm (dead link).
For my international friends who don’t understand the Swedish: I am quite happy with the questions and being allowed to answer them at this lengths etc, so I am considering doing a full translation of it and posting it at a later date.
Believe me, this kind of seemingly random act of kindness warms up even the most seasoned and cold hacker’s heart. Look at this excerpt from a mail I received:
From: Stephanie T <…@google.com>
Subject: 2 Googlers would like to recognize your hard work on cURLHello Daniel,
As you know, we here in Google’s Open Source Programs Office are always interested in learning about new projects and people in the open source community. To that end, we asked our co-workers to help us by nominating people outside of Google that they thought were doing great things in the world of open source. This information helps us determine which organizations to fund and which projects to select for the Google Summer of Code and related programs.
Chris C and John M (Googlers) believe your work on cURL deserves to be recognized. To show our appreciation for this work, we would like to send you a special thank you gift and 2- $175 USD gift codes (totaling $350 USD) to the Google online store so you can pick out tee shirts or other gifts for yourself and loved ones.
[snip]
Thanks a lot!
(The names of the persons in the mail have been shortened by me to reduce their exposure here.)
I tweeted about me finding a change in Apple’s version of curl that I haven’t seen any public patch for. Apple otherwise hosts a whole slew of curl patches which they never discuss with us about but still make public and we can see what they did.
I was trying to help out a fellow curl user on IRC (we’re in #curl on freenode, come see us) and he was trying to understand some funny effects of running curl against a HTTPS site and he showed me the output from a “curl -v” log. The verbose log curiously was different than mine (same curl version built by myself on Linux). My conclusion was that something was different in the Apple version.
The users log said:
* About to connect() to host.example.com port 443 (#0) * Trying 1.2.3.4... connected * Connected to host.example.com (1.2.3.4) port 443 (#0) * SSLv3, TLS handshake, Client hello (1):
… while my command against the same site said:
* About to connect() to host.example.com port 443 (#0) * Trying 1.2.3.4... connected * Connected to host.example.com (1.2.3.4) port 443 (#0) * successfully set certificate verify locations: * CAfile: /etc/ssl/certs/ca-certificates.crt CApath: none * SSLv3, TLS handshake, Client hello (1):
(I’ve bolded the part my output showed that wasn’t in the mac version, the real host name and IP have been changed.)
It seems I was wrong however.
The output above is only shown if libcurl sets the CA cert path to OpenSSL and it seems the Mac version doesn’t. Somehow they get the CA certs loaded to libcurl differently.
So ok, maybe they didn’t modify curl but they certainly changed how curl uses CA certs and they did this by modifying OpenSSL and clearly their version of OpenSSL now defaults to use their CA cert bundle. The end result for me is still the same though: I have no idea how CA certs work with curl on Mac so it leaves me with the unfortunate situation where I can’t help fellow curl users when they have CA cert problems on a Mac.
It also leaves me very curious on what –cacert does exactly on the mac version of curl.
OpenSSL is patched. Apparently it now works so that if the “normal” x509 validation fails, and TrustEvaluationAgent (TEA) is enabled, it will attempt to use the TEA to validate the certificate. The apple source code to read through for this is x509_vfy_apple.c in their patched OpenSSL tree. It is also possible to skip the TEA verification thing in OpenSSL by setting an environment variable, so that we can still have curl on mac act “as default” with a command line like:
$ env OPENSSL_X509_TEA_DISABLE=1 curl https://www.example.com/
Finally: yes, curl is released under an MIT license. They’re perfectly allowed to do whichever of these actions they want. I know this, and I chose the MIT license fully aware that any company can take the code, modify it and never return any changes. I’m not arguing against anyone’s rights to do this with curl.
Thank you, friendly anonymous helper for helping me straighten out my findings!
If I’m not part of the solution, I’m part of the problem and I don’t want to be part of the problem. More specifically, I’m talking about female presence in tech and in particular in open source projects.
I’ve been an open source and free software hacker, contributor and maintainer for almost 20 years. I’m the perfect stereo-type too: a white, hetero, 40+ years old male living in a suburb of a west European city. (I just lack a beard.) I’ve done more than 20,000 commits in public open source code repositories. In the projects I maintain, and have a leading role in, and for the sake of this argument I’ll limit the discussion to curl, libssh2, and c-ares, we’re certainly no better than the ordinary average male-dominated open source projects. We’re basically only men (boys?) talking to other men and virtually all the documentation, design and coding is done by male contributors (to a significant degree).
Sure, we have female contributors in all these projects, but for example in the curl case we have over 850 named contributors and while I’m certainly not sure who is a woman and who is not when I get contributions, there’s only like 10 names in the list that are typically western female names. Let’s say there are 20. or 30. Out of a total of 850 the proportions are devastating no matter what. It might be up to 3%. Three. THREE. I know women are under-represented in technology in general and in open source in particular, but I think 3% is even lower than the already low bad average open source number. (Although, some reports claim the number of female developers in foss is as low as just above 1%, geekfeminism says 1-5%).
Three percent. (In a project that’s been alive and kicking for thirteen years…) At this level after this long time, there’s already a bad precedent and it of course doesn’t make it easier to change now. It is also three percent of the contributors when we consider all contributors alike. If we’d count the number of female persons in leading roles in these projects, the amount would be even less.
It could be worth noting that we don’t really have any recent reliable stats for “real world” female share either. Most sources that I find on the Internet and people have quoted in talks tend to repeat old numbers that were extracted using debatable means and questions. The comparisons I’ve seen repeated many times on female participation in FOSS vs commercial software, are very often based on stats that are really not comparable. If someone has reliable and somewhat fresh data, please point them out for me!
I would blame “the system”. I’m working in embedded systems professionally as a consultant and contract developer. I’ve worked as a professional developer for some 20 years. In my niche, there’s not even 10% female developers. A while ago I went through my past assignments in order to find the last female developer that I’ve worked with, in a project, physically located in the same office. The last time I met a fellow developer at work who was female was early 2007. I’ve worked in 17 (seventeen!) projects since then, without even once having had a single female developer colleague. I usually work in smaller projects with like 5-10 people. So one female in 18 projects makes it something like one out of 130 or so. I’m not saying this is a number that is anything to draw any conclusions from since it just me and my guesstimates. It does however hint that the problem is far beyond “just” FOSS. It is a tech problem. Engineering? Software? Embedded software? Software development? I don’t know, but I know it is present both in my professional life as well as in my volunteer open source work.
Geekfeminism says the share is 10-30% in the “tech industry”. My experience says the share gets smaller and smaller the closer to “the metal” and low level programming you get – but I don’t have any explanation for it.
What are we (I) doing wrong? Am I at fault? Is the the way I talk or the way we run these projects in some subtle – or obvious – ways not friendly enough or downright hostile to women? What can or should we change in these projects to make us less hostile? The sad reality is that I don’t think we have any such fatal flaws in our projects that create the obstacles. I don’t think many females ever show up near enough the projects to even get mistreated in the first place.
I have a son and I have a daughter – they’re both still young and unaware of this kind of differences and problems. I hope I will be able to motivate and push and raise them equally. I don’t want to live in a world where my daughter will have a hard time to get into tech just because she’s a girl.
SPDY is a neat new protocol and possible contender to replace HTTP – at least in some areas and for some use cases. SPDY has been invented and developed mostly by Google engineers.
SPDY allows better usage of fewer TCP connections (since it sends multiple logical streams over a single physical TCP connection) and it helps clients overcome problems with TCP (like how a new connection starts slowly) while at the same time reducing latency and bandwidth requirements. Very similar to how channels are handled over an SSH connection.
Chrome of course already supports SPDY and Firefox has some early experimental support being worked on.
Of course there are also legitimate criticisms against SPDY as well, including subjects like how it makes caching proxies impossible (because everything goes over SSL), how it makes debugging a lot harder by using compressed headers, how it is impossible to extract just a single header from the stream due to its compression approach and how the compression state buffers make each individual stream use more memory than plain old HTTP (plain TCP) ones.
We can expect SPDY<=>HTTP gateways to appear so that nobody gets locked into either side of these protocols.
SPDY will provide faster transfers. libcurl is currently used for speed reasons in many cases. To me, it makes perfect sense to have libcurl use and try to use SPDY instead of HTTP exactly like how the browsers are starting to do it, so that the libcurl using applications will get their contents transferred faster.
My thinking is that we introduce some new magic option(s) that makes libcurl use SPDY, and for normal easy interface transfers it will remain to use a single connection for each new SPDY transfer, but if you use the multi interface and you enable pipelining you’ll instead make libcurl do multiple transfers over the same single SPDY connection (as long as you speak with the same server and port etc). From an application’s stand-point it shouldn’t make any difference, apart from being faster than otherwise. Just like we want it!
Implementation wise, I would like to use a reliable and efficient third-party library for the actual SPDY implementation. If there doesn’t exist any, we make one and run that one independently. I found libspdy, but I found some concerns about it (no mailing list, looks like one-man project, not C89 compliant, no API docs etc). I mailed the libspdy author, I hoping we’d sort out my doubts and then I’d base my continued work on that library.
After some time Thomas Roth, primary libspdy author, responded and during our subsequent email exchange I’ve gotten a restored faith and belief in this library and its direction. Not only did he fix the C89 compliance pretty quickly, he is also promising rather big changes that are pending to get committed within a week or so.
Comforted by what I’ve learned from Thomas, I’ll wait for his upcoming changes and I’ll join the soon to be created mailing list for the libspdy project and I’ll contribute some ideas and efforts to help shape it into the fine SPDY library we all want. I can only encourage other fellow SPDY library interested persons to do the same!
Updated: Join the SPDY library development
The FOSDEM 2012 dates were recently revealed (4-5 February 2012).
I’d be happy to arrange a get-together for libcurl hackers at Fosdem this year. To me, Brussels, Belgium seems mid-europe enough to be able to attract a bunch of us:
Potential subjects to discuss at such a meeting:
I would like at least 4-5 people voicing interest for this to be worthwhile for me to actually try to do anything. Please speak up on the libcurl mailing list, tweet me or mail me privately! The more people that are interested, the more planning and stuff we’ll do for it.
Another release of curl and libcurl just happened. 7.22.0 is released.
Apart from the 28 something documented bug fixes, we introduce a range of changes that could be noteworthy:
This release is this great thanks to 25 friendly contributors.
If you click the image you’ll see a full-resolution screendump for my recent search for “libcurl” on google. Where did that (image of a) girl come from? Judging from where it appears on the results page right next to the information about the cURL project you can’t but assume that she’s somehow related to the project.
That’s of course not true. When moving the mouse over the image I get a tooltip with a funny “hair curling” URL and that’s also where a click on the image takes me.
A mighty weird way of presenting a search result if you ask me!
(I am not a lawyer, this is not legal advice and these are not legal analyses, just my personal observations and ramblings. Please correct me where I’m wrong or add info if you have any!)
At 3:45 pm on March 18th 2011, the company Content Delivery Solutions LLC filed a complaint in a court in Texas, USA. The defendants are several bigwigs and the list includes several big and known names of the Internet:
The complaint was later amended with an additional patent (filed on April 18th), making it list three patents that these companies are claimed to violate (I can’t find the amended version online though). Two of the patents ( 6,393,471 and 6,058,418) are for marketing data and how to use client info to present ads basically. The third is about file transfer resumes.
I was contacted by a person involved in the case at one of the defendants’. This unspecified company makes one or more products that use “curl“. I don’t actually know if they use the command line tool or the library – but I figure that’s not too important here. curl gets all its superpowers from libcurl anyway.
This Patent Troll thus basically claims that curl violates a patent on resumed file transfers!
The patent in question that would be one that curl would violate is the US patent 6,098,180 which basically claims to protect this idea:
A system is provided for the safe transfer of large data files over an unreliable network link in which the connection can be interrupted for a long period of time.
The patent describes several ways in how it may detect how it should continue the transfer from such a break. As curl only does transfer resumes based on file name and an offset, as told by the user/application, that could be the only method that they can say curl would violate of their patent.
The patent goes into detail in how a client first sends a “signature” and after an interruption when the file transfer is about to continue, the client would ask the server about details of what to send in the continuation. With a very vivid imagination, that could possibly equal the response to a FTP SIZE command or the Content-Length: response in a HTTP GET or HEAD request.
A more normal reader would rather say that no modern file transfer protocol works as described in that patent and we should go with “defendant is not infringing, move on nothing to see here”.
But for the sake of the argument, let’s pretend that the patent actually describes a method of file transfer resuming that curl uses.
The ‘180 (it is referred to with that name within the court documents) patent was filed at February 18th 1997 (and issued on August 1, 2000). Apparently we need to find prior art that was around no later than February 17th 1996, that is to say one year before the filing of the stupid thing. (This I’ve been told, I had no idea it could work like this and it seems shockingly weird to me.)
What existing tools and protocols did resumed transfers in February 1996 based on a file name and a file offset?
Lots!
Thank you all friends for the pointers and references you’ve brought to me.
At the time of this writing I don’t know where this will end up or what’s going to happen. Time will tell.
This Software patent obviously is a concern mostly to US-based companies and those selling products in the US. I am neither a US citizen nor do I have or run any companies based in the US. However, since curl and libcurl are widely used products that are being used by several hundred companies already, I want to help bring out as much light as possible onto this problem.
The patent itself is of course utterly stupid and silly and it should never have been accepted as it describes trivially thought out ideas and concepts that have been thought of and implemented already decades before this patent was filed or granted although I claim that the exact way explained in the patent is not frequently used. Possibly the protocol using a method that is closed to the description of the patent is zmodem.
I guess I don’t have to mention what I think about software patents.
I’m convinced that most or all download tools and browsers these days know how to resume a previously interrupted transfer this way. Why wouldn’t these guys also approach one of the big guys (with thick wallets) who also use this procedure? Surely we can think of a few additional major players with file tools that can resume file transfers and who weren’t targeted in this suit!
I don’t know why. Clearly they’ve not backed down from attacking some of the biggest tech and software companies.
(Illustration from the ‘180 patent.)
Recently we’ve put in some efforts into remodeling libcurl’s code that handles name resolves, and then in particular the two asynchronous name resolver backends that we support: c-ares and threaded.
libcurl can be built to do name resolves using different means. The primary difference between them is that they are either synchronous or asynchronous. The synchronous way makes the operation block during name resolves and there’s no “decent” way to abort the resolves if they take longer time than the program wants to allow it (other than using signals and that’s not what we consider a decent way).
This is done using one of two ways: by building libcurl with c-ares support or by building libcurl and tell it to use threads to solve the problem. libcurl can be built using either mechanism on just about all platforms, but on Windows the build defaults to using the threaded resolver.
c-ares’ primary benefit is that it is an asynchronous name resolver library so it can do name resolves without blocking without requiring a new thread. It makes it use less resources and remain a perfect choice even if you’d scale up your application up to and beyond an insane number of simultaneous connections. Its primary drawback is that since it isn’t based on the system default name resolver functions, they don’t work exactly like the system name resolver functions and that causes trouble at times.
By making sure the system functions are still used, this makes name resolving work exactly as with the synchronous solution, but thanks to the threading it doesn’t block. The downside here is of course that it uses a new thread for every name resolve, which in some cases can become quite a large number and of course creating and killing threads at a high rate is much more costly than sticking with the single thread.
Now we’ve made sure that we have an internal API that both our asynchronous name resolvers implement, and all code internally use this API. It makes the code a lot cleaner than the previous #ifdef maze for the different approaches, and it has the side-effect that it should allow much easier pluggable backends in case someone would like to make libcurl support another asynchronous name resolver or system.
This is all brand new in the master branch so please try it out and help us polish the initial quirks that may still exist in the code.
There is no current plan to allow this plugging to happen run-time or using any kind of external plugins. I don’t see any particular benefit for us to do that, but it would give us a lot more work and responsibilities.