Thank you a lot for writing the document in such a short period. I will have it in mind when I will write the patches for dpif. If I have further questions can I get back to you Eitan?
Regards, Alin. -----Mesaj original----- De la: Nithin Raju [mailto:nit...@vmware.com] Trimis: Wednesday, August 6, 2014 10:58 PM Către: Eitan Eliahu Cc: dev@openvswitch.org; Rajiv Krishnamurthy; Alin Serdean; Ben Pfaff; Kaushik Guha; Ben Pfaff; Justin Pettit; Ankur Sharma; Samuel Ghinet; Linda Sun; Keith Amidon Subiect: Re: Design notes for provisioning Netlink interface from the OVS Windows driver (Switch extension) Eitan, Thanks so much for writing this up. This should clarify the questions that the folks had during the IRC meeting. Alin, Pls. feel free to send out a writeup if you have anything to discuss regarding the changes in dpif-linux.c. If not, if you can cleanup dpif-linux.c, and submit it with the changes/interface that was working with the Cloudbase kernel implementation, that should also be a major step forward. We can take up how to make the changes in dpif-linux.c to fit the (efficient) I/O model that Eitan has described. thanks, Nithin On Aug 6, 2014, at 11:15 AM, Eitan Eliahu <elia...@vmware.com> wrote: > > Hello all, > Here is a summary of our initial design. Not all areas are covered so we > would be glad to discuss anything listed here and any other code/features we > could leverage. > Thanks! > Eitan > > > A. Objectives: > [1] Create a NetLink (NL) driver interface for Windows which interoperates > with > the OVS NL user mode. > [2] User mode code should be mostly cross platform with some minimal changes > to > support specific Windows OS calls. > [3] The Driver should not have to maintain a state or resources for > transaction > or dumps > [4] Reduce the number of system calls: User mode NL code should use Device > IOCTL > system call to send an NL commands and to receive the associated NL reply > in the same system call, whenever possible (*). > [5] An event may be associated with a NL socket I/O request to signal a > completion for an outstanding receive operation on the socket. > (For simplicity a single outstanding I/O request could be associated > with > a socket for the signaling purpose) > > (*) We assume Multiple NL transactions for the same socket can never be > interleaved > > B. Netlink operation types: > There are four types of interactions carried by processes through the NL > layer: > > [1] Transaction based DPIF primitives: these DPIF commands are mapped to > nl_sock_transact NL interface to nl_sock_transact_multiple. The > transaction > based command creates an ad hoc socket and submits a synchronous device > I/O to the driver. The driver constructs the NL reply and copies it to > the > output buffer of the IRP representing the I/O transaction. > (Provisioning of transaction based command can be brought up and exercised > through the ovs-dpctl command in parallel to the exsisting DPIF > device) > > > [2] State aware DPIF Dump commands: port and flow dump calls the following NL > interfaces: > a) nl_dump_start() > b) nl_dump_next() > c) nl_dump_done() > > With the exception of nl_dump_start these NL primitives are based on a > synchronous IOCTL system call rather than Write/Read. Thus, the > driver > does not have to maintain any dump transaction outstanding request nor > need to allocate any resources for it. > > [3] UpCall Port/PID/Unicast socket: > The driver maintains per socket queue for all packets which have no > matching flow in the flow table. The socket has a single overlapped > (event) > structure which will be signalled through a completion of a pending I/O > request sent by user mode on subscription (similar to the current > implementation). When dpif_recv_wait is called, the event associated > with > the pending I/O request is passed poll_fd_wait_event inorder to wake > the > thread which polls the port queue. > > dpif_recv calls nl_socket_recv which in turn drains the queue > maintained by the kernel in a synchronous fashion (through the use of > system ioctl call). The overlapped structure is rearmed when the > recv_set > DPIF callback function is called. > > [4] Event notification / NL multicast subscription: > An event (such as port addition/deletion link up/down) are propagated from > the kernel to user mode through a subscription of a socket to a > multicast > group (nl_sock_join_mcgroup()) and a synchronous Receive > (nl_sock_recv()) > for retrieving the events. The driver maintains a single event queue for > all events. Similar to the UpCall mechanism, a user mode process keeps > an > outstanding I/O request in the driver which is triggered whenever a new > event is generated. The event associated with the overlapped structure > of > the socket is passed to poll_fd_wait_event() whenever > dpif_port_poll_wait() > callback function is called. dpif_poll() will drain the event queue > through > the call of nl_sock_recv(). > > C. Implementation work flow: > The driver creates a device object which provides a NetLink interface > for user mode processes. During the development phase this device is > created in addition to the existing DPIF device. (This means that the > bring-up of the NL based user mode can be done on a live kernel with > resident DPs, ports and flows) All transaction and dump based DPIF > functions could be developed and brought up when the NL device is a > secondary device (ovs-dpctl show and dump XXX should work). After the > initial phase is completed (i.e. all transaction and dump based DPIF > primitives are implemented), the original device interface will be > removed and packet and event propagation path will be brought up > (driven by vswicth.exe) > > [1] Socket creation > Since PID should be allocated on a system wide basis and unique across all > processes, the kernel > assigns the PID for a newly created socket. A new IOCTL command > OVS_GET_PID returns the PID to a user > mode client to be associated with the socket. > > [2] Detailed description > nl_sock_transact_multiple() which calls into a series of nl_sock_send__() > and nl_sock_recv__(). These can be implemented using ReadFile() and > WriteFile() > or an ioctl modeled on a transaction which does both read and write. One > thing > though is that, nl_sock_transact_multiple() might have to be modified to > the > series of nl_sock_send__() and nl_sock_recv__(), rather than doing a bunch > of > sends first and then doing the recvs. This is because Windows may not > preserve > message boundaries when we do the recv. > > _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
