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yggdrasil-go/src/tuntap/iface.go

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package tuntap
import (
"github.com/yggdrasil-network/yggdrasil-go/src/address"
"github.com/yggdrasil-network/yggdrasil-go/src/crypto"
"github.com/yggdrasil-network/yggdrasil-go/src/yggdrasil"
"golang.org/x/net/icmp"
"golang.org/x/net/ipv6"
"github.com/Arceliar/phony"
)
const TUN_OFFSET_BYTES = 4
type tunWriter struct {
phony.Inbox
tun *TunAdapter
buf [TUN_OFFSET_BYTES + 65536]byte
}
func (w *tunWriter) writeFrom(from phony.Actor, b []byte) {
w.Act(from, func() {
w._write(b)
})
}
// write is pretty loose with the memory safety rules, e.g. it assumes it can
// read w.tun.iface.IsTap() safely
func (w *tunWriter) _write(b []byte) {
var written int
var err error
n := len(b)
if n == 0 {
return
}
temp := append(w.buf[:TUN_OFFSET_BYTES], b...)
written, err = w.tun.iface.Write(temp, TUN_OFFSET_BYTES)
if err != nil {
w.tun.Act(w, func() {
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if !w.tun.isOpen {
w.tun.log.Errorln("TUN iface write error:", err)
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}
})
}
if written != n+TUN_OFFSET_BYTES {
// FIXME some platforms return the wrong number of bytes written, causing error spam
//w.tun.log.Errorln("TUN iface write mismatch:", written, "bytes written vs", n+TUN_OFFSET_BYTES, "bytes given")
}
}
type tunReader struct {
phony.Inbox
tun *TunAdapter
buf [TUN_OFFSET_BYTES + 65536]byte
}
func (r *tunReader) _read() {
// Get a slice to store the packet in
// Wait for a packet to be delivered to us through the TUN adapter
n, err := r.tun.iface.Read(r.buf[:], TUN_OFFSET_BYTES)
if n <= TUN_OFFSET_BYTES || err != nil {
r.tun.log.Errorln("Error reading TUN:", err)
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ferr := r.tun.iface.Flush()
if ferr != nil {
r.tun.log.Errorln("Unable to flush packets:", ferr)
}
} else {
bs := make([]byte, n, n+crypto.BoxOverhead) // extra capacity for later...
copy(bs, r.buf[TUN_OFFSET_BYTES:n+TUN_OFFSET_BYTES])
r.tun.handlePacketFrom(r, bs, err)
}
if err == nil {
// Now read again
r.Act(nil, r._read)
}
}
func (tun *TunAdapter) handlePacketFrom(from phony.Actor, packet []byte, err error) {
tun.Act(from, func() {
tun._handlePacket(packet, err)
})
}
// does the work of reading a packet and sending it to the correct tunConn
func (tun *TunAdapter) _handlePacket(recvd []byte, err error) {
if err != nil {
tun.log.Errorln("TUN iface read error:", err)
return
}
// Offset the buffer from now on so that we can ignore ethernet frames if
// they are present
bs := recvd[:]
// Check if the packet is long enough to detect if it's an ICMP packet or not
if len(bs) < 7 {
tun.log.Traceln("TUN iface read undersized unknown packet, length:", len(bs))
return
}
// From the IP header, work out what our source and destination addresses
// and node IDs are. We will need these in order to work out where to send
// the packet
var dstAddr address.Address
var dstSnet address.Subnet
var addrlen int
n := len(bs)
// Check the IP protocol - if it doesn't match then we drop the packet and
// do nothing with it
if bs[0]&0xf0 == 0x60 {
// Check if we have a fully-sized IPv6 header
if len(bs) < 40 {
tun.log.Traceln("TUN iface read undersized ipv6 packet, length:", len(bs))
return
}
// Check the packet size
if n-tun_IPv6_HEADER_LENGTH != 256*int(bs[4])+int(bs[5]) {
return
}
// IPv6 address
addrlen = 16
copy(dstAddr[:addrlen], bs[24:])
copy(dstSnet[:addrlen/2], bs[24:])
} else if bs[0]&0xf0 == 0x40 {
// Check if we have a fully-sized IPv4 header
if len(bs) < 20 {
tun.log.Traceln("TUN iface read undersized ipv4 packet, length:", len(bs))
return
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}
// Check the packet size
if n != 256*int(bs[2])+int(bs[3]) {
return
}
// IPv4 address
addrlen = 4
copy(dstAddr[:addrlen], bs[16:])
} else {
// Unknown address length or protocol, so drop the packet and ignore it
tun.log.Traceln("Unknown packet type, dropping")
return
}
if tun.ckr.isEnabled() {
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if addrlen != 16 || (!dstAddr.IsValid() && !dstSnet.IsValid()) {
if key, err := tun.ckr.getPublicKeyForAddress(dstAddr, addrlen); err == nil {
// A public key was found, get the node ID for the search
dstNodeID := crypto.GetNodeID(&key)
dstAddr = *address.AddrForNodeID(dstNodeID)
dstSnet = *address.SubnetForNodeID(dstNodeID)
addrlen = 16
}
}
}
if addrlen != 16 || (!dstAddr.IsValid() && !dstSnet.IsValid()) {
// Couldn't find this node's ygg IP
dlen := len(bs)
if dlen > 900 {
dlen = 900
}
ptb := &icmp.DstUnreach{
Data: bs[:dlen],
}
if packet, err := CreateICMPv6(bs[8:24], bs[24:40], ipv6.ICMPTypeDestinationUnreachable, 0, ptb); err == nil {
tun.writer.writeFrom(nil, packet)
}
return
}
// Do we have an active connection for this node address?
var dstString string
session, isIn := tun.addrToConn[dstAddr]
if !isIn || session == nil {
session, isIn = tun.subnetToConn[dstSnet]
if !isIn || session == nil {
// Neither an address nor a subnet mapping matched, therefore populate
// the node ID and mask to commence a search
if dstAddr.IsValid() {
dstString = dstAddr.GetNodeIDLengthString()
} else {
dstString = dstSnet.GetNodeIDLengthString()
}
}
}
// If we don't have a connection then we should open one
if !isIn || session == nil {
// Check we haven't been given empty node ID, really this shouldn't ever
// happen but just to be sure...
if dstString == "" {
panic("Given empty dstString - this shouldn't happen")
}
_, known := tun.dials[dstString]
tun.dials[dstString] = append(tun.dials[dstString], bs)
for len(tun.dials[dstString]) > 32 {
tun.dials[dstString] = tun.dials[dstString][1:]
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}
if !known {
go func() {
conn, err := tun.dialer.Dial("nodeid", dstString)
tun.Act(nil, func() {
packets := tun.dials[dstString]
delete(tun.dials, dstString)
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if err != nil {
return
}
// We've been given a connection so prepare the session wrapper
var tc *tunConn
if tc, err = tun._wrap(conn.(*yggdrasil.Conn)); err != nil {
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// Something went wrong when storing the connection, typically that
// something already exists for this address or subnet
tun.log.Debugln("TUN iface wrap:", err)
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return
}
for _, packet := range packets {
tc.writeFrom(nil, packet)
}
})
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}()
}
}
// If we have a connection now, try writing to it
if isIn && session != nil {
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session.writeFrom(tun, bs)
}
}