frameassembly 1.5.1

A DSL for creating custom .pcap/.pcapng captures and decompiling captures to .fasm for testing firewalls, IDS rules, SNMP traps, and pentesting.
Documentation 
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//! Layer 4 transport-layer protocol and header modifier parsers for FrameAssembly.
//!
//! This module coordinates syntactic combinators for Layer 4 transport protocols and shared
//! transport modifiers, including Transmission Control Protocol (`TCP`), User Datagram Protocol
//! (`UDP`), and Stream Control Transmission Protocol (`SCTP`). It also parses universal transport
//! overrides such as source port (`SRCPORT`), destination port (`DSTPORT`), sequence and
//! acknowledgment numbers (`SEQ`, `ACKNUM`), and explicit transport selection (`TRANSPORT`).

use winnow::ModalResult as PResult;
use winnow::combinator::{alt, cut_err};
use winnow::prelude::*;

use crate::ast::*;
use crate::lexer::Token;
use crate::parser::{ParsedField, Stream, parse_u16, parse_u32, tag};

pub(crate) mod sctp;
pub(crate) mod tcp;
pub(crate) mod udp;

pub(crate) use sctp::*;
pub(crate) use tcp::*;
pub(crate) use udp::*;

/// Parses a Layer 4 protocol or modifier field from a token stream.
pub(crate) fn parse_l4_field<'i, 'a>(input: &mut Stream<'i, 'a>) -> PResult<ParsedField<'a>> {
    alt((
        parse_tcp_field,
        parse_udp_field,
        parse_sctp_field,
        alt((
            (tag(Token::SrcPort), cut_err(parse_u16))
                .map(|((_, s), v)| ParsedField::SrcPort(v, (s.start, s.end - s.start))),
            (tag(Token::DstPort), cut_err(parse_u16))
                .map(|((_, s), v)| ParsedField::DstPort(v, (s.start, s.end - s.start))),
            (
                tag(Token::Transport),
                cut_err(alt((
                    tag(Token::Tcp).value(TransportProto::Tcp),
                    tag(Token::Udp).value(TransportProto::Udp),
                ))),
            )
                .map(|((_, s), v)| ParsedField::Transport(v, (s.start, s.end - s.start))),
            (tag(Token::Seq), cut_err(parse_u32))
                .map(|((_, s), v)| ParsedField::Seq(v, (s.start, s.end - s.start))),
            (tag(Token::AckNum), cut_err(parse_u32))
                .map(|((_, s), v)| ParsedField::AckNum(v, (s.start, s.end - s.start))),
        )),
    ))
    .parse_next(input)
}