move port prediction into dedicated module

port_prediction.nim

@@ -0,0 +1,11 @@
+from net import Port
+
+proc predictPortRange*(dstPorts: seq[Port]): seq[Port] =
+  # TODO: do real port prediction
+  result = newSeq[Port](1)
+  let basePort = min(dstPorts[1].uint16,
+                     uint16.high - (result.len - 1).uint16)
+  for i in 0 .. result.len - 1:
+    result[i] = Port(basePort + i.uint16)
+
+

puncher.nim

@@ -42,14 +42,6 @@ proc injectTcpPacket*(rawFd: AsyncFD, ipPacket: IpPacket) {.async.} =
   except OSError as e:
     raise newException(PunchHoleError, e.msg)
 
-proc predictPortRange*(dstPorts: seq[Port]): seq[Port] =
-  # TODO: do real port prediction
-  result = newSeq[Port](1)
-  let basePort = min(dstPorts[1].uint16,
-                     uint16.high - (result.len - 1).uint16)
-  for i in 0 .. result.len - 1:
-    result[i] = Port(basePort + i.uint16)
-
 proc makeFirewallRule(srcIp: IpAddress, srcPort: Port,
                       dstIp: IpAddress, dstPort: Port): string =
   # FIXME: use & instead of fmt?

tcp_syni_accept.nim

@@ -3,6 +3,7 @@ from net import IpAddress, Port, `$`, `==`, parseIpAddress
 from random import randomize, rand
 from sequtils import any
 import ip_packet
+import port_prediction
 import puncher
 import raw_socket
 import utils

tcp_syni_connect.nim

@@ -3,6 +3,7 @@ from net import IpAddress, Port, `$`, `==`
 from nativesockets import setSockOptInt
 import ip_packet
 import network_interface
+import port_prediction
 import puncher
 import raw_socket
 import utils