// receives packets from the receive loop and dispatches them
// to their corresponding connections
func processLoop(c net.PacketConn, l *listener, rld *receiveLoopData, pld *processLoopData) {
var (
quit bool
wg = new(sync.WaitGroup)
tq = newTimerQueue()
connections = struct {
sync.RWMutex
M map[uint32]*connection
}{
M: make(map[uint32]*connection),
}
)
// keep a refcount to `c` for ourselves
wg.Add(1)
defer wg.Done()
// wait for all pending connections, then close the socket
go func() {
wg.Wait()
c.Close()
tq.Close()
}()
// generate a new key for cookies
cookieKey := make([]byte, sha1.Size)
if _, err := crand.Read(cookieKey); err != nil {
l.L.Lock()
l.err = fmt.Errorf("Failed to generate cookie secret: %v", err)
l.L.Unlock()
l.Broadcast()
return
}
sig := hmac.New(sha1.New, cookieKey)
// generate addler32(localaddr)
var localAddrSum [4]byte
binary.LittleEndian.PutUint32(localAddrSum[:], adler32.Checksum([]byte(c.LocalAddr().String())))
shouldWait := func() bool {
waitOnConnections := pld.rejectNewConnections && pld.remainingConnections == 0
return pld.err == nil && len(pld.Q) == 0 && !waitOnConnections
}
var packets []processLoopPacket
for !quit {
// wait for a packet to become available
pld.L.Lock()
for shouldWait() {
pld.Wait()
}
rejectNewConnections := pld.rejectNewConnections
pldErr := pld.err
quit = pldErr != nil
packets, pld.Q = pld.Q, packets[:0]
remainingConnections := pld.remainingConnections
pld.L.Unlock()
if rejectNewConnections && remainingConnections == 0 {
quit = true
}
// process packets
for ii := range packets {
buffer, addr := packets[ii].D, packets[ii].A
switch PacketType(buffer[0]) {
case PacketInit:
// are we accepting new connections?
if rejectNewConnections {
continue
}
// verify length
const MinInitPacketLength = 9
if len(buffer) < MinInitPacketLength {
continue
}
// verify protocol magic
if !bytes.Equal(buffer[1:5], protocolMagic) {
continue
}
// verify version
if buffer[5] != version1 {
sendAbort(c, addr, buffer[6:9])
continue
}
var outgoing [32]byte
now := time.Now()
outgoing[0] = byte(PacketCookie)
if _, err := crand.Read(outgoing[1:4]); err != nil {
return
}
copy(outgoing[4:7], buffer[6:9])
outgoing[7] = version1
binary.LittleEndian.PutUint32(outgoing[8:12], uint32(now.Add(5*time.Second).Unix()+1))
sig.Reset()
sig.Write(outgoing[1:12])
sig.Write(localAddrSum[:])
sig.Sum(outgoing[1:12])
c.WriteTo(outgoing[:], addr)
case PacketCookieEcho:
// are we accepting new connections
if rejectNewConnections {
continue
}
// verify length
const CookieEchoPacketLength = 32
if len(buffer) != CookieEchoPacketLength {
continue
}
// verify signature
sig.Reset()
sig.Write(buffer[1:12])
sig.Write(localAddrSum[:])
if !hmac.Equal(sig.Sum(nil), buffer[12:]) {
continue
}
// verify version
if buffer[7] != version1 {
sendAbort(c, addr, buffer[1:4])
continue
}
// vetify timeout
now := time.Now()
if time.Unix(int64(binary.LittleEndian.Uint32(buffer[8:12])), 0).Before(now) {
sendAbort(c, addr, buffer[1:4])
continue
}
// decode connection tag to uin32
tagId := binary.LittleEndian.Uint32(buffer[3:7]) >> 8
connections.RLock()
_, ok := connections.M[tagId]
connections.RUnlock()
// create new connection
if !ok {
// create connection
wg.Add(1)
connections.Lock()
conn := newConnection(c, addr, tq, buffer[1:4], func() {
connections.Lock()
delete(connections.M, tagId)
connections.Unlock()
wg.Done()
pld.L.Lock()
pld.remainingConnections--
remain := pld.remainingConnections
pld.L.Unlock()
if remain == 0 {
pld.Signal()
}
})
connections.M[tagId] = conn
connections.Unlock()
pld.L.Lock()
pld.remainingConnections++
pld.L.Unlock()
l.L.Lock()
l.pending = append(l.pending, conn)
l.L.Unlock()
l.Signal()
}
// send COOKIE-ACK
var outgoing [4]byte
outgoing[0] = byte(PacketCookieAck)
copy(outgoing[1:4], buffer[1:4])
c.WriteTo(outgoing[:], addr)
default:
// parse connection tag
tagId := binary.LittleEndian.Uint32(buffer[0:4]) >> 8
connections.RLock()
conn, ok := connections.M[tagId]
connections.RUnlock()
// discard packets addressed to unknown connections
if !ok {
sendAbort(c, addr, buffer[1:4])
continue
}
// copy the packet data so we can reuse the buffer
p := NewPacket(len(buffer))
copy(p.D, buffer)
// queue the packet onto the connection
conn.L.Lock()
conn.Incoming = append(conn.Incoming, p)
conn.L.Unlock()
conn.Signal()
}
}
// return the packet to the receive loop
rld.L.Lock()
for ii := range packets {
rld.buffers = append(rld.buffers, packets[ii].D)
}
rld.L.Unlock()
rld.Signal()
// if we were signaled to quit, terminate existing connections
if pldErr != nil {
connections.Lock()
m := connections.M
connections.M = make(map[uint32]*connection)
connections.Unlock()
for _, c := range m {
c.closeWithError(pldErr)
}
}
}
}
