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Reframe
Reframe — Click element; reframes a fragmented stream of packets
Reframe([keywords FOFF, FLEN, NTOH, MUL, ALIGN, ADD])
Ports: 1 input, 1 output
Drivers: userlevel
Queues incoming packet fragments until a full Ethernet, IP, or fixed-size frame can be built, then emits it. Does not set packet annotations. Useful for reframing a fragmented stream of packets emitted by a userlevel element like Socket. Assumes that the stream is either continuous, or that frames are separated by aligned and/or fixed-size padding.
The length of each frame should be encoded in a FLEN (1, 2, or 4) byte field located FOFF bytes into each frame. The encoded length is assumed to include FOFF plus FLEN. If the field is encoded in network order, specify the keyword NTOH. Specify the byte multiplier that should be used in the keyword MUL, the alignment within the byte stream (if any) of each frame in the keyword ALIGN, and any additional bytes that should be added to the result in the keyword ADD.
If FLEN is 0, all keywords except ADD are ignored and the length of each frame is assumed to be fixed at ADD bytes.
For example, to reframe a fragment stream of IP packets (total length in bytes is encoded 2 bytes into the frame as a 2-byte variable in network order):
... -> Reframe(FOFF 2, FLEN 2, NTOH 1, MUL 1, ALIGN 1, ADD 0) -> ...
Or since these are the keyword defaults:
... -> Reframe -> ...
To reframe a fragment stream of IP-in-Ethernet packets:
... -> Reframe(FOFF 16, FLEN 2, ADD 14) -> ...
To reframe a fragment stream of fixed-size 100 byte packets:
... -> Reframe(FLEN 0, ADD 100) -> ...
Keyword arguments are:
- FOFF — Integer. Specifies the byte offset of the encoded length field in each frame in the fragment stream. Default is 2 (IP).
- FLEN — Integer. Specifies the length of the encoded length field in each frame in the fragment stream. Default is 2 (IP).
- NTOH — Boolean. When true, Reframe will assume that the length field is encoded in network order in each frame in the fragment stream. Default is true (IP).
- MUL — Integer. Specifies the number of bytes per unit of encoded length. Default is 1 (IP).
- ALIGN — Integer. Specifies the byte alignment of each frame in the fragment stream. For example, a byte alignment of 4 would ensure that each frame began and ended at a byte offset (from the start of the stream) that was divisible by 4. Default is 1 (IP).
- ADD — Integer. Specifies the number of additional bytes that should be added to each frame in the fragment stream. Default is 0 (IP).
// Reframe a fragmented stream of tunnelled IP frames Socket(TCP, 0.0.0.0, 12345) -> Reframe -> ...
// Reframe a fragmented stream of tunnelled IP-in-GRE frames. Plain // GRE headers are 4 bytes long and do not include a payload length // field, so we must reach 4 + 2 = 6 bytes into each frame to reach // the IP length field, and add 4 bytes to account for the GRE header. Socket(TCP, 0.0.0.0, 12345) -> Reframe(FOFF 6, ADD 4) -> StripGREHeader ...
// A useless 1000 byte latency bucket ... -> Reframe(FLEN 0, ADD 1000) -> ...
Generated by click-elem2man from ../elements/local/reframe.hh:6 on 2017/10/17.