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README.md

Table of Contents

Netdever

TinyGo's network device driver model comprises two Go interfaces: Netdever and Netlinker. This README covers Netdever.

The Netdever interface describes an L4/L3 network interface modeled after the BSD sockets. A netdev is a concrete implementation of a Netdever. See Netlinker for the L2 network interface.

A netdev can:

  • Send and receive L4/L3 packets
  • Resolve DNS lookups
  • Get/set the device's IP address

TinyGo network drivers implement the Netdever interface, providing a BSD sockets interface to TinyGo's "net" package. net.Conn implementations (TCPConn, UDPConn, and TLSConn) use the netdev socket. For example, net.DialTCP, which returns a net.TCPConn, calls netdev.Socket() and netdev.Connect():

func DialTCP(network string, laddr, raddr *TCPAddr) (*TCPConn, error) {

        fd, _ := netdev.Socket(netdev.AF_INET, netdev.SOCK_STREAM, netdev.IPPROTO_TCP)

        netdev.Connect(fd, "", raddr.IP, raddr.Port)

        return &TCPConn{
                fd:    fd,
                laddr: laddr,
                raddr: raddr,
        }, nil
}

Setting Netdev

Before the app can use TinyGo's "net" package, the app must set the netdev using UseNetdev(). This binds the "net" package to the netdev driver. For example, setting the wifinina driver as the netdev:

	nina := wifinina.New(&cfg)
	netdev.UseNetdev(nina)

Netdev Driver Notes

See the wifinina and rtl8720dn for examples of netdev drivers. Here are some notes for netdev drivers.

Locking

Multiple goroutines may invoke methods on a net.Conn simultaneously, and since the net package translates net.Conn calls into netdev socket calls, it follows that multiple goroutines may invoke socket calls, so locking is required to keep socket calls from stepping on one another.

Don't hold a lock while Time.Sleep()ing waiting for a long hardware operation to finish. Unlocking while sleeping let's other goroutines make progress.

Sockfd

The netdev BSD socket interface uses a socket fd (int) to represent a socket connection (end-point). Each fd maps 1:1 to a net.Conn maps. The number of fds available is a hardware limitation. Wifinina, for example, can hand out 10 fds, representing 10 active sockets.

Testing

The netdev driver should minimally run all of the example/net examples.