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.
sebastiw · 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() ->
-    % http://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}
     ).