frameassembly 1.4.4

Compile .fasm code into deterministic .pcap/.pcapng captures across 81 L2-L7 protocols to test firewalls, IDS rules, SNMPv3 traps, Wireshark & Rust.
Documentation 
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//! Generic Routing Encapsulation (GRE, RFC 2784 / RFC 2890) AST definitions.
//!
//! Defines the multiprotocol IP-in-IP and Layer 2 overlay tunneling header specified in RFC 2784 and
//! extended with Key and Sequence Number fields in RFC 2890 over IP protocol `47` (`0x2F`). The GRE
//! header begins with a 16-bit Flags and Version word (`C` Checksum bit `0x8000`, `K` Key bit `0x2000`,
//! `S` Sequence bit `0x1000`, Version `0`) followed by a 16-bit IEEE EtherType `Protocol Type`
//! (`GRE_PROTO`, default `0x0800` IPv4, `0x6558` NVGRE TEB, `0x88BE` ERSPAN, `0x8847` MPLS) and
//! optional 32-bit Checksum/Reserved (`CHECKSUM`), Key (`GRE_KEY`), and Sequence (`GRE_SEQ`) words.
//!
//! Canonical `.fasm` syntax:
//! `a -> b GRE [GRE_KEY <u32>] [GRE_SEQ <u32>] [GRE_PROTO <u16>] [CHECKSUM] [PAYLOAD "<str>" | HEXPAYLOAD "<hex>"]`

use core::marker::PhantomData;

/// Generic Routing Encapsulation (RFC 2784 / RFC 2890) specification over IP protocol `47`.
///
/// Syntax mapping: `GRE [GRE_KEY <u32>] [GRE_SEQ <u32>] [GRE_PROTO <u16>] [CHECKSUM]`
#[doc(alias = "GRE")]
#[doc(alias = "RFC 2784")]
#[doc(alias = "RFC2784")]
#[doc(alias = "RFC 2890")]
#[doc(alias = "RFC2890")]
#[doc(alias = "NVGRE")]
#[doc(alias = "ERSPAN")]
#[doc(alias = "GRE_KEY")]
#[doc(alias = "GRE_SEQ")]
#[doc(alias = "GRE_PROTO")]
#[doc(alias = "CHECKSUM")]
#[derive(Debug, Clone, PartialEq, Eq, Default)]
pub struct GreSpec<'a> {
    /// Optional 32-bit RFC 2890 GRE Key / VSID field (`GRE_KEY <u32>`, sets `K` flag `0x2000`).
    pub key: Option<u32>,
    /// Optional 32-bit RFC 2890 Sequence Number field (`GRE_SEQ <u32>`, sets `S` flag `0x1000`).
    pub seq: Option<u32>,
    /// 16-bit IEEE EtherType of the encapsulated passenger protocol (`GRE_PROTO <u16>`, default `0x0800`).
    pub proto: Option<u16>,
    /// RFC 2784 Checksum Present flag (`CHECKSUM`, sets `C` flag `0x8000` and inserts 32-bit Checksum/Reserved word).
    pub checksum: bool,
    /// Optional lifetime phantom marker for AST uniformity.
    pub _marker: PhantomData<&'a ()>,
}