https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=13932
--- Comment #13 from Huang Qiangxiong <qiangxiong.hu...@gmail.com> ---
(In reply to Michael Mann from comment #12)
> (In reply to Huang Qiangxiong from comment #0)
> > Created attachment 15730 [details]
> > grpc/protobuf sample cap file. (message compress by gzip)
>
> I don't see in https://developers.google.cn/protocol-buffers/docs/encoding
> how bitmasks are explained. When looking at this capture file, packet 9 has
> 5 fields, and the field number for the 5th buffer is 536870910 (i.e. really
> large number). But ProtoBuf is trying to apply a bitmask of 0xF8 (maybe
> because it's presumed that field number should be a UINT8). It seems like
> the current logic is "if varint has more bytes that bitmask covers, treat
> other bytes with bitmask 0xFF". I don't think that's how bitmasks should
> work.
>
> I'm working on https://code.wireshark.org/review/23813 (using
> packet-protobuf.c in other patches for testing) and I have it so that the
> varint number is retrieved and then the bitmask is applied, which makes the
> field number 30, not 536870910. This seems "more correct" to me, but
> wanted other opinions (possibly documentation showing how bitmasks are
> applied)
The 536870910 is correct field number. This is a test case made by me for
testing parsing a big field number. This package is generated by offical
protobuf library (for java) according to the attachment of "A more complicated
grpc/protobuf proto file -- helloworld.proto". You can see the definition of
this field in helloworld.proto:
message HelloRequest {
...
sfixed32 sfixed32param_largefn = 536870910;
...
}
Dissected result like this: (with *.proto file supported)
Frame 9: 245 bytes on wire (1960 bits), 245 bytes captured (1960 bits) on
interface 0
Ethernet II, Src: Vmware_c0:00:08 (00:50:56:c0:00:08), Dst: Vmware_94:16:c4
(00:0c:29:94:16:c4)
Internet Protocol Version 4, Src: 192.168.65.1, Dst: 192.168.65.10
Transmission Control Protocol, Src Port: 61063, Dst Port: 50051, Seq: 80, Ack:
50, Len: 191
HyperText Transfer Protocol 2
Stream: HEADERS, Stream ID: 3, Length 124, POST
/helloworld.Greeter/SayHello
Stream: DATA, Stream ID: 3, Length 49
GRPC Message: /helloworld.Greeter/SayHello, Request
Protocol Buffers: /helloworld.Greeter/SayHello,request
Message: helloworld.HelloRequest
[Message Name: helloworld.HelloRequest]
Field[1]: name = world (string)
Field[2]: sint32param = -6 (sint32)
Field[3]: uint64param = 10 (uint64)
Field[4]: int32param = -5 (int32)
Field[536870910]: sfixed32param_largefn = 888 (sfixed32)
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