Add RFC2890 for GRE packets

Decoding previously did not honor RFC2890 (Key and Sequence Number Extensions to GRE), it now does. Also, the completely wrong GRE packet binary has been fixed in pkt_gre_tests.
msantos · May 17, 2018 · b2da5bf · b2da5bf
1 parent 892ecdd
commit b2da5bf
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Showing 3 changed files with 31 additions and 21 deletions.
diff --git a/include/pkt_gre.hrl b/include/pkt_gre.hrl
@@ -1,6 +1,8 @@
 %% RFC 2784 - Generic Routing Encapsulation (GRE)
 -record(gre, {
- c = 0 :: pkt:bit(), res0 = 0 :: 0..2#111111111111, ver = 0 :: 0..2#111,
+ c = 0 :: pkt:bit(), r = 0 :: pkt:bit(), k = 0 :: pkt:bit(), s = 0 :: pkt:bit(),
+ res0 = 0 :: 0..2#111111111, ver = 0 :: 0..2#111,
  type = ?ETH_P_IP :: pkt:uint16_t(),
- chksum = 0 :: pkt:uint16_t(), res1 = 0 :: pkt:uint16_t()
+ chksum = 0 :: pkt:uint16_t(), res1 = 0 :: pkt:uint16_t(),
+ key = 0 :: pkt:uint16_t(), sequence = 0 :: pkt:uint16_t()
  }).
diff --git a/src/pkt_gre.erl b/src/pkt_gre.erl
@@ -35,17 +35,27 @@
 
 -export([codec/1]).
 
-codec(<<0:1,Res0:12,Ver:3,Type:16,Rest/binary>>) ->
- {#gre{c = 0, res0 = Res0, ver = Ver, type = Type
- },Rest
+codec(<<C:1,R:1,K:1,S:1,Res0:9,Ver:3,Type:16,Bin/binary>>) ->
+ {[Chksum, Res1, Key, Sequence], Payload} = unpack([C, K, S], Bin),
+ {#gre{c = C, r = R, k = K, s = S, res0 = Res0, ver = Ver, type = Type, chksum = Chksum,
+ res1 = Res1, key = Key, sequence = Sequence
+ },Payload
  };
-codec(<<1:1,Res0:12,Ver:3,Type:16,Chksum:16,Res1:16,Rest/binary>>) ->
- {#gre{c = 1, res0 = Res0, ver = Ver, type = Type,
- chksum = Chksum, res1 = Res1
- },Rest
- };
-codec(#gre{c = 0, res0 = Res0, ver = Ver, type = Type}) ->
- <<0:1,Res0:12,Ver:3,Type:16>>;
-codec(#gre{c = 1, res0 = Res0, ver = Ver, type = Type,
- chksum = Chksum, res1 = Res1}) ->
- <<1:1,Res0:12,Ver:3,Type:16,Chksum:16,Res1:16>>.
+
+codec(#gre{c = C, r = R, k = K, s = S, res0 = Res0, ver = Ver, type = Type, chksum = Chksum,
+ res1 = Res1, key = Key, sequence = Sequence
+ }) ->
+ ChecksumLength = C*16,
+ Res1Length = ChecksumLength,
+ KeyLength = K*32,
+ SequenceLength = S*32,
+ <<C:1,R:1,K:1,S:1,Res0:9,Ver:3,Type:16,Chksum:ChecksumLength,Res1:Res1Length,Key:KeyLength,Sequence:SequenceLength>>.
+
+unpack([0, 0, 0], Bin) -> {[0, 0, 0, 0], Bin};
+unpack([C, K, S], Bin) ->
+ ChecksumLength = C*16,
+ Res1Length = ChecksumLength,
+ KeyLength = K*32,
+ SequenceLength = S*32,
+ <<Chksum:ChecksumLength,Res1:Res1Length,Key:KeyLength,Sequence:SequenceLength,Payload/binary>> = Bin,
+ {[Chksum, Res1, Key, Sequence], Payload}.
diff --git a/test/pkt_gre_tests.erl b/test/pkt_gre_tests.erl
@@ -10,16 +10,14 @@ codec_test_() ->
  ].
 
 packet() ->
- % https://pcapr.net/view/mu/2009/8/3/21/gre-keepalive.pcap.html
- <<255,0,8,0,119,128,0,0,69,0,0,35,148,47,0,0,64,1,238,215,
- 127,0,0,1,127,0,0,1,8,0,165,38,217,147,0,1>>.
+ <<48,0,8,0,0,0,48,57,0,0,0,1,
+ 69,0,0,20,0,0,0,0,64,6,0,0,127,0,0,1,127,0,0,1>>.
 
 decode() ->
  {Header, Payload} = pkt:gre(packet()),
  ?_assertEqual(
- {{gre,1,4064,0,2048,30592,0},
- <<69,0,0,35,148,47,0,0,64,1,238,215,127,0,0,1,127,0,0,1,
- 8,0,165,38,217,147,0,1>>},
+ {{gre,0,0,1,1,0,0,2048,0,0,12345,1},
+ <<69,0,0,20,0,0,0,0,64,6,0,0,127,0,0,1,127,0,0,1>>},
  {Header, Payload}
  ).