package yggdrasil // This manages the tun driver to send/recv packets to/from applications import "github.com/songgao/packets/ethernet" import "github.com/yggdrasil-network/water" const tun_IPv6_HEADER_LENGTH = 40 const tun_ETHER_HEADER_LENGTH = 14 // Represents a running TUN/TAP interface. type tunDevice struct { core *Core icmpv6 icmpv6 send chan<- []byte recv <-chan []byte mtu int iface *water.Interface } // Defines which parameters are expected by default for a TUN/TAP adapter on a // specific platform. These values are populated in the relevant tun_*.go for // the platform being targeted. They must be set. type tunDefaultParameters struct { maximumIfMTU int defaultIfMTU int defaultIfName string defaultIfTAPMode bool } // Gets the maximum supported MTU for the platform based on the defaults in // getDefaults(). func getSupportedMTU(mtu int) int { if mtu > getDefaults().maximumIfMTU { return getDefaults().maximumIfMTU } return mtu } // Initialises the TUN/TAP adapter. func (tun *tunDevice) init(core *Core) { tun.core = core tun.icmpv6.init(tun) } // Starts the setup process for the TUN/TAP adapter, and if successful, starts // the read/write goroutines to handle packets on that interface. func (tun *tunDevice) start(ifname string, iftapmode bool, addr string, mtu int) error { if ifname == "none" { return nil } if err := tun.setup(ifname, iftapmode, addr, mtu); err != nil { return err } go func() { panic(tun.read()) }() go func() { panic(tun.write()) }() return nil } // Writes a packet to the TUN/TAP adapter. If the adapter is running in TAP // mode then additional ethernet encapsulation is added for the benefit of the // host operating system. func (tun *tunDevice) write() error { for { data := <-tun.recv if tun.iface == nil { continue } if tun.iface.IsTAP() { var frame ethernet.Frame frame.Prepare( tun.icmpv6.peermac[:6], // Destination MAC address tun.icmpv6.mymac[:6], // Source MAC address ethernet.NotTagged, // VLAN tagging ethernet.IPv6, // Ethertype len(data)) // Payload length copy(frame[tun_ETHER_HEADER_LENGTH:], data[:]) if _, err := tun.iface.Write(frame); err != nil { panic(err) } } else { if _, err := tun.iface.Write(data); err != nil { panic(err) } } util_putBytes(data) } } // Reads any packets that are waiting on the TUN/TAP adapter. If the adapter // is running in TAP mode then the ethernet headers will automatically be // processed and stripped if necessary. If an ICMPv6 packet is found, then // the relevant helper functions in icmpv6.go are called. func (tun *tunDevice) read() error { mtu := tun.mtu if tun.iface.IsTAP() { mtu += tun_ETHER_HEADER_LENGTH } buf := make([]byte, mtu) for { n, err := tun.iface.Read(buf) if err != nil { // panic(err) return err } o := 0 if tun.iface.IsTAP() { o = tun_ETHER_HEADER_LENGTH } if buf[o]&0xf0 != 0x60 || n != 256*int(buf[o+4])+int(buf[o+5])+tun_IPv6_HEADER_LENGTH+o { // Either not an IPv6 packet or not the complete packet for some reason //panic("Should not happen in testing") continue } if buf[o+6] == 58 { // Found an ICMPv6 packet b := make([]byte, n) copy(b, buf) // tun.icmpv6.recv <- b go tun.icmpv6.parse_packet(b) } packet := append(util_getBytes(), buf[o:n]...) tun.send <- packet } } // Closes the TUN/TAP adapter. This is only usually called when the Yggdrasil // process stops. Typically this operation will happen quickly, but on macOS // it can block until a read operation is completed. func (tun *tunDevice) close() error { if tun.iface == nil { return nil } return tun.iface.Close() }