Crate pcap_parser

PCAP and PCAPNG parsers

This crate contains several parsers for PCAP and PCAPNG files.

Compared to other similar projects, it is designed to offer a complete support of the many possible formats (legacy pcap, pcapng, little or big-endian, etc.) and features (pcapng files with multiple sections, interfaces, and endianness) while using only safe code and without copying data (zero-copy).

The code is available on Github and is part of the Rusticata project.

The pcap format(s)

The PCAP format (files usually ending with .pcap extension) is rather trivial. The PCAPNG format (usually .pcapng extension) is much more complex: it can be composed of multiple sections, each with multiple interfaces, having different capture lengths, time precision and even endianness!

These formats are more containers than data formats: packets contain data, formatted according to its interface linktype. There are many possible linktypes, defined in the linktypes registry. Support for parsing some of them is provided using the data feature (disabled by default).

This crate provides an abstraction over these different formats.

Parsing a file

pcap-parser provides several ways of parsing pcap data. Choosing the right one is mostly driven by resources: if the input file is small, the parse_pcap and parse_pcapng functions can be used directly.

Fine-grained functions are also available, to parse specifically some block types for example. They are listed in the pcap and pcapng modules.

If the input is larger and cannot fit into memory, then streaming parsers are available. They work by iterating on blocks, and so do not require to map the entire input. They cannot seek to a specific block, however.

Note: due to PCAPNG limitations, it is not possible to directly seek in a file to get a packet and handle it: the caller has to iterate though the file and store (at least) the interface descriptions for the current section, in order of appearance.

Example: streaming parsers

The following code shows how to parse a file in the pcap-ng format, using a PcapNGReader streaming parser.

use pcap_parser::*;
use pcap_parser::traits::PcapReaderIterator;
use std::fs::File;
use std::io::Read;

let mut file = File::open(path).unwrap();
let mut num_blocks = 0;
let mut reader = PcapNGReader::new(65536, file).expect("PcapNGReader");
loop {
    match reader.next() {
        Ok((offset, _block)) => {
            println!("got new block");
            num_blocks += 1;
            reader.consume(offset);
        },
        Err(PcapError::Eof) => break,
        Err(PcapError::Incomplete) => {
            reader.refill().unwrap();
        },
        Err(e) => panic!("error while reading: {:?}", e),
    }
}
println!("num_blocks: {}", num_blocks);

See PcapNGReader for a complete example, including handling of linktype and accessing packet data.

For legacy pcap files, use similar code with the LegacyPcapReader streaming parser.

See pcap-tools, pcap-parse and integration tests for more examples.

Example: generic streaming parsing

To create a pcap reader for input in either PCAP or PCAPNG format, use the create_reader function.

Serialization

Support for serialization (i.e. generating binary data) is available by enabling the serialize feature. Most structures gain the to_vec() method (provided by the ToVec trait).

Note: support is still experimental, though working. API may change in the future.

Re-exports

pub use pcap::*;

pub use pcapng::*;

Modules

data	Helper functions to access block contents (depending in linktype)
pcap	PCAP file format
pcapng	PCAPNG file format
traits

Structs

CurrentSectionInfo
LegacyPcapIterator	Iterator over PcapCapture
LegacyPcapReader	Parsing iterator over legacy pcap data (streaming version)
LegacyPcapSlice	Parsing iterator over legacy pcap data (requires data to be loaded into memory)
Linktype	Data link type
PcapCapture	Generic interface for PCAP file access
PcapNGCapture	Generic interface for PCAPNG file access
PcapNGCaptureIterator	Iterator over PcapNGCapture
PcapNGReader	Parsing iterator over pcap-ng data (streaming version)
PcapNGSlice	Parsing iterator over pcap-ng data (requires data to be loaded into memory)

Enums

Data	A container for owned or borrowed data
MutableData	A container for owned or borrowed mutable data
PcapBlock	A block from a Pcap or PcapNG file
PcapBlockOwned	A block from a Pcap or PcapNG file
PcapError

Traits

Capture	Generic interface for PCAP or PCAPNG file access
ToVec	Common trait for all serialization functions

Functions

create_reader	Get a generic PcapReaderIterator, given a Read input. The input is probed for pcap-ng first, then pcap.
parse_pcap	Parse the entire file
parse_pcapng	Parse the entire file