packet lib: serialize in reverse order

- we need to serialize in reverse order since some need to know
  payload.
- TCP and UDP need the previous protocol info (IP) to calculate the
  checksum.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

ryu/lib/packet/arp.py

@@ -15,7 +15,6 @@
 
 import struct
 from . import packet_base
-from ryu.ofproto.ofproto_parser import msg_pack_into
 
 
 class arp(packet_base.PacketBase):
@@ -42,7 +41,8 @@ class arp(packet_base.PacketBase):
         return cls(hwtype, proto, hlen, plen, opcode, src_mac, src_ip,
                    dst_mac, dst_ip), None
 
-    def serialize(self, buf, offset):
-        msg_pack_into(arp._PACK_STR, buf, offset, self.hwtype, self.proto,
-                      self.hlen, self.plen, self.opcode,
-                      self.src_mac, self.src_ip, self.dst_mac, self.dst_ip)
+    def serialize(self, payload, prev):
+        return struct.pack(arp._PACK_STR, self.hwtype, self.proto,
+                           self.hlen, self.plen, self.opcode,
+                           self.src_mac, self.src_ip, self.dst_mac,
+                           self.dst_ip)

ryu/lib/packet/ethernet.py

@@ -17,7 +17,6 @@ import struct
 from . import packet_base
 from . import vlan
 from ryu.ofproto import ether
-from ryu.ofproto.ofproto_parser import msg_pack_into
 
 
 class ethernet(packet_base.PacketBase):
@@ -35,9 +34,9 @@ class ethernet(packet_base.PacketBase):
         dst, src, ethertype = struct.unpack_from(cls._PACK_STR, buf)
         return cls(dst, src, ethertype), ethernet.get_packet_type(ethertype)
 
-    def serialize(self, buf, offset):
-        msg_pack_into(ethernet._PACK_STR, buf, offset,
-                      self.dst, self.src, self.ethertype)
+    def serialize(self, payload, prev):
+        return struct.pack(ethernet._PACK_STR, self.dst, self.src,
+                           self.ethertype)
 
 
 # copy vlan _TYPES

ryu/lib/packet/ipv4.py

@@ -16,7 +16,6 @@
 import struct
 from . import packet_base
 from . import udp
-from ryu.ofproto.ofproto_parser import msg_pack_into
 from ryu.ofproto import inet
 
 
@@ -69,13 +68,15 @@ class ipv4(packet_base.PacketBase):
             s = self.carry_around_add(s, w)
         return ~s & 0xffff
 
-    def serialize(self, buf, offset):
+    def serialize(self, payload, prev):
+        hdr = bytearray().zfill(self.header_length * 4)
         version = self.version << 4 | self.header_length
         flags = self.flags << 15 | self.offset
-        msg_pack_into(ipv4._PACK_STR, buf, offset, version, self.tos,
-                      self.total_length, self.identification, flags,
-                      self.ttl, self.proto, 0, self.src, self.dst)
-        self.csum = self.checksum(buf[offset:offset + self.length])
-        msg_pack_into('H', buf, offset + 10, self.csum)
+        struct.pack_into(ipv4._PACK_STR, hdr, 0, version, self.tos,
+                         self.total_length, self.identification, flags,
+                         self.ttl, self.proto, 0, self.src, self.dst)
+        self.csum = self.checksum(hdr)
+        struct.pack_into('H', hdr, 10, self.csum)
+        return hdr
 
 ipv4.register_packet_type(udp.udp, inet.IPPROTO_UDP)

ryu/lib/packet/packet.py

@@ -34,11 +34,15 @@ class Packet(object):
                 self.protocols.append(proto)
 
     def serialize(self):
-        offset = 0
         self.data = bytearray()
-        for p in self.protocols:
-            p.serialize(self.data, offset)
-            offset += p.length
+        r = self.protocols[::-1]
+        for i, p in enumerate(r):
+            if i == len(r) - 1:
+                prev = None
+            else:
+                prev = r[i + 1]
+            data = p.serialize(self.data, prev)
+            self.data = data + self.data
 
     def add_protocol(self, proto):
         self.protocols.append(proto)

ryu/lib/packet/udp.py

@@ -15,7 +15,6 @@
 
 import struct
 from . import packet_base
-from ryu.ofproto.ofproto_parser import msg_pack_into
 
 
 class udp(packet_base.PacketBase):
@@ -39,6 +38,6 @@ class udp(packet_base.PacketBase):
 
         return msg, None
 
-    def serialize(self, buf, offset):
-        msg_pack_into(udp._PACK_STR, buf, offset, self.src_port, self.dst_port,
-                      self.length, self.csum)
+    def serialize(self, payload, prev):
+        return struct.pack(udp._PACK_STR, self.src_port, self.dst_port,
+                           self.length, self.csum)

ryu/lib/packet/vlan.py

@@ -40,9 +40,9 @@ class vlan(packet_base.PacketBase):
         vid = tci & ((1 << 12) - 1)
         return cls(pcp, cfi, vid, ethertype), vlan.get_packet_type(ethertype)
 
-    def serialize(self, buf, offset):
+    def serialize(self, payload, prev):
         tci = self.pcp << 15 | self.cfi << 12 | self.vid
-        msg_pack_into(vlan._PACK_STR, buf, offset, tci, self.ethertype)
+        return struct.pack(vlan._PACK_STR, tci, self.ethertype)
 
 vlan.register_packet_type(arp.arp, ether.ETH_TYPE_ARP)
 vlan.register_packet_type(ipv4.ipv4, ether.ETH_TYPE_IP)