On Tue, Dec 13, 2016 at 11:49 PM, Du, Fan <fan...@intel.com> wrote: > Hi > > I'm interested to one Docker issue[1] which looks like related to kernel > vxlan socket creation > as described in the thread. From my limited knowledge here, socket creation > is synchronous , > and after the *socket* syscall, the sock handle will be valid and ready to > linkup.
You need to read the code. vxlan tunnel is a UDP tunnel, it needs a kernel socket (and a port) to setup UDP communication, unlike GRE tunnel etc. > > Somehow I'm not sure the detailed scenario here, and which/how possible > commit fix? > Thanks! > > Quoted analysis: > -------------------------------------------------------------------------- > (Found in kernel 3.13) > The issue happens because in older kernels when a vxlan interface is created, > the socket creation is queued up in a worker thread which actually creates > the socket. But this needs to happen before we bring up the link on the vxlan > interface. > If for some chance, the worker thread hasn't completed the creation of the > socket > before we did link up then when we do link up the kernel checks if the socket > was > created and if not it will return ENOTCONN. This was a bug in the kernel > which got fixed > in later kernels. That is why retrying with a timer fixes the issue. This was introduced by commit 1c51a9159ddefa5119724a4c7da3fd3ef44b68d5 and later fixed by commit 56ef9c909b40483d2c8cb63fcbf83865f162d5ec.
