func getRequest(conn *ss.Conn) (host string, extra []byte, err error) {
const (
idType = 0 // address type index
idIP0 = 1 // ip addres start index
idDmLen = 1 // domain address length index
idDm0 = 2 // domain address start index
typeIPv4 = 1 // type is ipv4 address
typeDm = 3 // type is domain address
typeIPv6 = 4 // type is ipv6 address
lenIPv4 = 1 + net.IPv4len + 2 // 1addrType + ipv4 + 2port
lenIPv6 = 1 + net.IPv6len + 2 // 1addrType + ipv6 + 2port
lenDmBase = 1 + 1 + 2 // 1addrType + 1addrLen + 2port, plus addrLen
)
// buf size should at least have the same size with the largest possible
// request size (when addrType is 3, domain name has at most 256 bytes)
// 1(addrType) + 1(lenByte) + 256(max length address) + 2(port)
buf := make([]byte, 260)
var n int
// read till we get possible domain length field
ss.SetReadTimeout(conn)
if n, err = io.ReadAtLeast(conn, buf, idDmLen+1); err != nil {
return
}
//fmt.Println(buf)
reqLen := -1
switch buf[idType] {
case typeIPv4:
reqLen = lenIPv4
case typeIPv6:
reqLen = lenIPv6
case typeDm:
reqLen = int(buf[idDmLen]) + lenDmBase
default:
err = fmt.Errorf("addr type %d not supported", buf[idType])
return
}
if n < reqLen { // rare case
ss.SetReadTimeout(conn)
if _, err = io.ReadFull(conn, buf[n:reqLen]); err != nil {
return
}
} else if n > reqLen {
// it's possible to read more than just the request head
extra = buf[reqLen:n]
}
tp := strings.Split(conn.LocalAddr().String(), ":")
if len(tp) == 2 {
p := tp[1]
now := time.Now().Format("2006-01-02 15:04:05")
if len(flowData.Usage[p]) == 0 {
flowData.Usage[p] = []string{"0", now}
}
used, _ := strconv.ParseUint(flowData.Usage[p][0], 10, 64)
used += uint64(n - reqLen)
flowData.Usage[p][0] = strconv.FormatUint(used, 10)
flowData.Usage[p][1] = now
}
// Return string for typeIP is not most efficient, but browsers (Chrome,
// Safari, Firefox) all seems using typeDm exclusively. So this is not a
// big problem.
switch buf[idType] {
case typeIPv4:
host = net.IP(buf[idIP0 : idIP0+net.IPv4len]).String()
case typeIPv6:
host = net.IP(buf[idIP0 : idIP0+net.IPv6len]).String()
case typeDm:
host = string(buf[idDm0 : idDm0+buf[idDmLen]])
}
// parse port
port := binary.BigEndian.Uint16(buf[reqLen-2 : reqLen])
host = net.JoinHostPort(host, strconv.Itoa(int(port)))
return
}
func handleConnection(conn *ss.Conn, port string) {
var host string
//fmt.Println(strings.Split(conn.LocalAddr().String(), ":")[1])
connCnt++ // this maybe not accurate, but should be enough
if connCnt-nextLogConnCnt >= 0 {
// XXX There's no xadd in the atomic package, so it's difficult to log
// the message only once with low cost. Also note nextLogConnCnt maybe
// added twice for current peak connection number level.
log.Printf("Number of client connections reaches %d\n", nextLogConnCnt)
nextLogConnCnt += logCntDelta
}
// function arguments are always evaluated, so surround debug statement
// with if statement
if debug {
debug.Printf("new client %s->%s\n", conn.RemoteAddr().String(), conn.LocalAddr())
}
closed := false
defer func() {
if debug {
debug.Printf("closed pipe %s<->%s\n", conn.RemoteAddr(), host)
}
connCnt--
if !closed {
conn.Close()
}
}()
host, extra, err := getRequest(conn)
if err != nil {
log.Println("error getting request", conn.RemoteAddr(), conn.LocalAddr(), err)
return
}
debug.Println("connecting", host)
remote, err := net.Dial("tcp", host)
if err != nil {
if ne, ok := err.(*net.OpError); ok && (ne.Err == syscall.EMFILE || ne.Err == syscall.ENFILE) {
// log too many open file error
// EMFILE is process reaches open file limits, ENFILE is system limit
log.Println("dial error:", err)
} else {
log.Println("error connecting to:", host, err)
}
return
}
defer func() {
if !closed {
remote.Close()
}
}()
// write extra bytes read from
if extra != nil {
// debug.Println("getRequest read extra data, writing to remote, len", len(extra))
if _, err = remote.Write(extra); err != nil {
debug.Println("write request extra error:", err)
return
}
}
if debug {
debug.Printf("piping %s<->%s", conn.RemoteAddr(), host)
}
go ss.PipeThenClose(conn, remote, ss.SET_TIMEOUT, flowData, port)
ss.PipeThenClose(remote, conn, ss.NO_TIMEOUT, flowData, port)
closed = true
return
}