That's amazing, thanks. We'll have to try to recompile curl under cygwin to confirm that it keeps up the constants, and then does the right posix calls.
I will grab the files, and try to have this tested and report back to you. Take care, Cary Lewis On Wed, Jul 1, 2020 at 3:51 PM Corinna Vinschen <corinna-cyg...@cygwin.com> wrote: > On Jun 30 18:53, Corinna Vinschen wrote: > > On Jun 30 09:46, Cary Lewis via Cygwin wrote: > > > Thanks for the reply. The answer to your question is that the 2 hour > keep > > > alive was not sufficient for a particular use case I encountered. > > > > > > I was trying to use curl under cygwin to access a very slow REST > endpoint > > > that was taking up to 8 minutes to generate download before any data > flowed > > > back to the client. This caused the server to abort the socket. > > > > > > Accessing the endpoint in chrome or firefox revealed that they set a > > > keepalive to 45 seconds, which kept the server happy. > > > > > > Attempting to set --keepalive-time=45 in cygwin's curl didn't work, and > > > wireshark revealed that no keepalives were being sent. > > > > > > I will attempt to patch cygwin, I got the build to work. Can you point > me > > > in the right direction, in terms of where the socket calls get mapped > to > > > the winsock calls? > > > > Actually, while I'm usually happy to take contributions, you don't have > > to dig into that yourself. I already have a few local patches in the > > loop changing some of the affected code. I have a good idea what's > > required to add the keep-alive socket options to that code, so just lay > > back and stay tuned for now. > > Ok, so I added support for a couple more IPPROTO_TCP socket options. > First of all I fixed TCP_MAXSEG which was using the BSD value, rather > than the WinSock value. Then I added TCP_FASTOPEN, TCP_KEEPIDLE, > TCP_KEEPCNT, TCP_KEEPINTVL, TCP_QUICKACK and TCP_USER_TIMEOUT: > > - TCP_FASTOPEN is supported since W10 1607, it's just faked on older > systems. > > - TCP_KEEPIDLE, TCP_KEEPCNT, TCP_KEEPINTVL are using the options > of the same name since W10 1709, WSAIoctl(SIO_KEEPALIVE_VALS) > on older systems. > > But here's a problem: Older systems didn't allow to change > TCP_KEEPCNT. It is always fixed to 10. Mulling over that problem in > the shower, I came up with the following solution: > > The max keep-alive timeout is TCP_KEEPIDLE + TCP_KEEPCNT * TCP_KEEPINTVL. > This should stay the same from a user space perspective. So the current > code tweaks the TCP_KEEPINTVL given to WinSock so that > > TCP_KEEPCNT * user space TCP_KEEPINTVL == 10 * WinSock TCP_KEEPINTVL > > Example: user space TCP_KEEPCNT 4, TCP_KEEPINTVL 5 (4 * 5 == 20) > ==> WinSock TCP_KEEPCNT 10, TCP_KEEPINTVL 2 (10 * 2 == 20) > > I hope that makes sense. > > - TCP_USER_TIMEOUT is supported with msec granularity since W10 1607 > (called TCP_MAXRTMS), with 1 secs granularity on older systems > (called TCP_MAXRT). Use the latter on older systems under the expected > loss of precision. > > - TCP_QUICKACK is supposedly supported on Windows as a socket option > but it's still not clear if the net got that right so far. However, > there's WSAIoctl(SIO_TCP_SET_ACK_FREQUENCY) doing the same. > > I uploaded developer snapshots to https://cygwin.com/snapshots/, > please test. > > For testing, you'll need at least the DLL, plus the changed headers > cygwin/socket.h and netinet/tcp.h from the complete tar file > cygwin-20200701.tar.xz. Or, just take the DLL and fetch the headers > right from the git repo. > > > Thanks, > Corinna > > -- > Corinna Vinschen > Cygwin Maintainer > -- > Problem reports: https://cygwin.com/problems.html > FAQ: https://cygwin.com/faq/ > Documentation: https://cygwin.com/docs.html > Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple > -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
