Struct LayerContext 

pub struct LayerContext {
    pub info: BTreeMap<String, Vec<u8>>,
}

Context passed between network layers for routing decisions

This structure carries routing information through the protocol stack, allowing each layer to add or consume information needed for proper packet delivery. This is designed to be protocol-agnostic and avoids hard-coding specific protocol fields like IP addresses.

Design Philosophy

• Protocol-agnostic: No IP addresses or protocol-specific fields in core structure
• Flexible key-value store: Each protocol layer can add/read arbitrary data
• Layer composition: Enables proper separation without tight coupling
• Follows @petitstrawberry’s guidance: Generic, not tied to specific protocols

Example Flow

// TCP layer creates context with its info
let mut ctx = LayerContext::new();
ctx.set("tcp_src_port", &5000u16.to_be_bytes());
ctx.set("tcp_dst_port", &80u16.to_be_bytes());

// TCP layer sends to IP, IP adds its info
let ip_src = [192, 168, 1, 100];
let ip_dst = [192, 168, 1, 1];
ctx.set("ip_src", &ip_src);
ctx.set("ip_dst", &ip_dst);
ctx.set("ip_protocol", &[6]); // TCP

// IP layer sends to Ethernet, Ethernet performs ARP
// Ethernet can read "ip_dst" to determine MAC address

Fields

info: BTreeMap<String, Vec<u8>>

Protocol-agnostic key-value store for routing information Each layer can add/read arbitrary data needed for packet delivery

Common keys (convention, not enforced):

• “ip_src”, “ip_dst”: IPv4/IPv6 addresses
• “tcp_src_port”, “tcp_dst_port”: TCP ports
• “udp_src_port”, “udp_dst_port”: UDP ports
• “ip_protocol”: Protocol number (6=TCP, 17=UDP)
• “ttl”: Time-to-live
• “tos”: Type of service

Implementations

impl LayerContext

pub fn new() -> Self

Create a new empty LayerContext

pub fn set(&mut self, key: &str, value: &[u8])

Set a value in the context

pub fn get(&self, key: &str) -> Option<&[u8]>

Get a value from the context

pub fn contains(&self, key: &str) -> bool

Check if a key exists

Trait Implementations

impl Clone for LayerContext

fn clone(&self) -> LayerContext

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for LayerContext

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for LayerContext

fn default() -> LayerContext

Returns the “default value” for a type.