On Thu, Apr 11, 2013 at 02:19:25PM -0700, Oleg Moskalenko wrote: >Hi All > >I found a non-standard behavior of UDP sockets in Cygwin. Normally, people = >do not experience it, but the communication pattern that I am going to desc= >ribe here is often used in DTLS (actually, this is virtually the only way t= o >make OpenSSL working with DTLS on the server side), so I suppose that wit= h >the growing DTLS popularity people will experience the problem often. > >So this is how to reproduce the problem in "plain" UDP (without actually using >DTLS): > >1) Server application: open a UDP socket (socket A); > >2) Server application: bind socket A to a local server address (say, >172.17.17.107:3478); > >3) Server application: wait for a packet from a client application; > >4) Client application: open a UDP socket (socket C); > >5) Client application: bind socket C it to a local client address (say, >168.16.16.106:12345); > >6) Client application: send a UDP packet P1 from socket C to server >socket A (to 172.17.17.107:3478); > >7) Server application: socket A receives the packet P1 from socket C; > >8) Server application: create another UDP socket B; > >9) Server application: bind socket B TO THE SAME LOCAL ADDRESS as socket >A (172.17.17.107:3478); > >10) Server application: connect socket B to the remote address of socket C >(168.16.16.106:12345) by calling connect() on the datagram socket B. > >11) Server application: send packet P2 from socket B to socket C (to >168.16.16.106:12345). > >12) Client application: on socket C, receive packet P2 from socket B (from >172.17.17.107:3478). > >13) Client application: from socket C, send packet P3 to the server address >172.17.17.107:3478. > >14) Server application: socket A receives the packet P3 from the client >socket. ERROR !!! > >Step 14 is wrong: the packet P3 must be delivered to socket B, because socket >B is "connected" >to the remote address 168.16.16.106:12345, but socket A is "unconnected". >Both sockets (A and B) are "bound" to the same server ad= dress >(172.17.17.107:3478) but the connected one >(socket B) must be obtaining packets from the remote address that it is >connected to. > >This is a very essential functionality for anybody who wants to implement the >server-side DTLS communications. > >This patterns works in any OS that I tried (all FreeBSD versions, all Linux >versions and Solaris) but Cygwin fails, unfortunately. > >I am trying to migrate (port) our server application to Cygwin, and it stops >us completely. It works everywhere else. > >Please take a look if this is something that can be fixed quickly.
How about a simple test case? cgf -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
