index 0000000..e173cdb
--- /dev/null
+++ b/scapy/contrib/bier.py
-@@ -0,0 +1,39 @@
+@@ -0,0 +1,56 @@
+# http://trac.secdev.org/scapy/ticket/31
+
-+# scapy.contrib.description = MPLS
++# scapy.contrib.description = BIER
+# scapy.contrib.status = loads
+
+from scapy.packet import *
+from scapy.fields import *
-+from scapy.layers.inet import IP
++from scapy.layers.inet import IP, UDP
+from scapy.layers.inet6 import IPv6
+
++
+class BIERLength:
-+ BIER_LEN_64 = 0
-+ BIER_LEN_128 = 1
-+ BIER_LEN_256 = 2
++ BIER_LEN_64 = 0
++ BIER_LEN_128 = 1
++ BIER_LEN_256 = 2
++ BIER_LEN_512 = 3
++ BIER_LEN_1024 = 4
++
++
++BIERnhcls = {1: "MPLS",
++ 2: "MPLS",
++ 4: "IPv4",
++ 5: "IPv6"}
+
+
++class BIFT(Packet):
++ name = "BIFT"
++ fields_desc = [BitField("bsl", 0, 4),
++ BitField("sd", 0, 8),
++ BitField("set", 0, 8),
++ BitField("cos", 0, 3),
++ BitField("s", 1, 1),
++ ByteField("ttl", 0)]
+
-+BIERnhcls = { 1: "MPLS",
-+ 2: "MPLS",
-+ 4: "IPv4",
-+ 5: "IPv6" }
+
+class BIER(Packet):
-+ name = "BIER"
-+ fields_desc = [ BitField("id", 5, 4),
-+ BitField("version", 0, 4),
-+ BitField("length", 0, 4),
-+ BitField("entropy", 0, 20),
-+ BitField("OAM", 0, 2),
-+ BitField("RSV", 0, 2),
-+ BitField("DSCP", 0, 6),
-+ BitEnumField("Proto", 2, 6, BIERnhcls),
-+ ShortField("BFRID", 0),
-+ StrFixedLenField("BitString",
-+ chr(255)*32, 32) ]
++ name = "BIER"
++ fields_desc = [BitField("id", 5, 4),
++ BitField("version", 0, 4),
++ BitFieldLenField("length", BIERLength.BIER_LEN_256, 4,
++ length_of=lambda x:(x.BitString >> 8)),
++ BitField("entropy", 0, 20),
++ BitField("OAM", 0, 2),
++ BitField("RSV", 0, 2),
++ BitField("DSCP", 0, 6),
++ BitEnumField("Proto", 2, 6, BIERnhcls),
++ ShortField("BFRID", 0),
++ StrLenField("BitString",
++ "",
++ length_from=lambda x:(8 << x.length))]
+
+
+bind_layers(BIER, IP, Proto=4)
+bind_layers(BIER, IPv6, Proto=5)
++bind_layers(UDP, BIFT, dport=8138)
++bind_layers(BIFT, BIER)