VALE ports, and it helps reducing data copies in This is only supported on the transmit ring of User virtual address is in the 'ptr' field of the slot. NS_INDIRECT indicates that the packet's payload is in a user-supplied buffer whose NS_NO_LEARN tells the forwarding code that the source MAC address for this packet must User application are forwarded to the other endpoint at the next systemĬall, thus restoring (in a selective way) the connection between a NIC and NS_FORWARD When a ring is in 'transparent' mode, packets marked with this flag by the Packets have been sent and a file descriptor can be closed. Hence signals can be delayed indefinitely. Netmap notifies transmit completions in batches, NS_REPORT reports when this buffer has been transmitted. The following flags affect slot and buffer processing: NS_BUF_CHANGED must be used when Normally, packets should be stored in the netmap-allocated buffersĪssigned to slots when ports are bound to a file descriptor. NICRXSYNC/poll()/select() recovers slots and reports new packets User advances head and cur, releasing some slots and holding others Irrespectively of the buffers originally provided by the kernel onĪfter the syscall, there are some (h)eld and some (R)eceived slots WhenĬlosing the netmap file descriptor, the kernel frees the buffersĬontained in the list pointed by ni_bufs_head , The buffers (i.e., binding them to the slots of a netmap ring). The application is free to modify this list and use ni_bufs_headĬontains the index of the first of these extra buffers, which areĬonnected in a list (the first uint32_t of each buffer being the index On success, the kernel writesīack to arg.nr_arg3 the number of extra buffersĪctually allocated (they may be less than the amount requested if the The number of extra buffers is specified in theĪrg.nr_arg3 field. In the same memory space, to be used as temporary storage for packets. NIOCREGIF can also request additional unbound buffers NICs also have an extra tx/rx ring pair connected to the host stack. Ni_rx_rings) normally depends on the hardware. ( struct netmap_rings) and their position in the Uint32_t ni_bufs_head /* head of extra bufs list */ Ports and rings are created and controlled through a fileĭescriptor, created by opening a special deviceĬonst uint32_t ni_flags /* properties */Ĭonst uint32_t ni_tx_rings /* NIC tx rings */Ĭonst uint32_t ni_rx_rings /* NIC rx rings */ Simpler, higher level functions are described in the The following section describes the system calls to create and Independently configured to share memory. Pipe ports by default use separate memory regions, but can be dev/netmap file descriptors bound to NICs. Same memory region, accessible to all processes who own Through the rings, and possibly implement zero-copy forwarding betweenĪll NICs operating in netmap mode use the Netmap client can send or receive packets in batches An additional ring pair connects to the hostĪfter binding a file descriptor to a port, a There is one ring for each transmit/receive Which can be connected to a physical interface In the rest of this (long) manual page we document various aspectsĪrchitecture, features and usage. A list of such devices is at the end of this document. Performance, netmap requires native support inĭevice drivers. Switch are implemented by a single kernel module, which also emulates Through ioctl(2), synchronization and blocking I/O throughĪ file descriptor and standard OS mechanisms such as Providing high speed packet I/O between processes, virtual machines, NICs Netmap monitors can be created dynamically, Netmap mode and send and receive raw packets through Userspace clients can dynamically switch NICs into Mode, which uses unmodified device drivers and is 3-5 times faster than Netmap support can still use the API in emulated Gbit/s NICs 35-40 Mpps on 40 Gbit/s NICs (limited by the hardware) aboutĢ0 Mpps per core for VALE ports and over 100 Mpps for Packet I/O using netmap on supported NICs reachesġ4.88 million packets per second (Mpps) with much less than one core on 10 With suitably fast hardware (NICs, PCIe buses, CPUs), Interchangeably with the same API, and are at least one order of magnitudeįaster than standard OS mechanisms (sockets, bpf, tun/tap interfaces, native Switch/dataplane netmap pipes a shared memory packet transport channel netmap monitors a mechanism similar to bpf(4) to capture traffic Including physical NIC ports to access individual queues of network interfaces host ports to inject packets into the host stack VALE ports implementing a very fast and modular in-kernel software Of Windows, and supports a variety of netmap ports, It runs on FreeBSD Linux and some versions And efficient packet I/O for userspace and kernel clients, and for Virtual
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