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https://github.com/jmcorgan/fips.git
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Johnathan Corgan
a481520191
PathMtuEntry and PathMtuLookup describe per-destination path MTU state that only the node writes, releases and expires; the TUN threads merely read it. FIPS_OVERHEAD is the combined FMP and FSP framing cost and is also used by the native datagram API. MIN_REACTIVE_PATH_MTU is path MTU policy for the MtuExceeded carrier and belongs beside MIN_ACTIONABLE_PATH_MTU. Define the path MTU types in node/path_mtu.rs, FIPS_OVERHEAD in a new proto/framing.rs, and MIN_REACTIVE_PATH_MTU in proto/mmp/limits.rs. The upper tun and icmp modules re-export all of them, so every existing crate and public path keeps resolving and no consumer changes. Values, types and documentation are unchanged, and none of the moved items has a log site.
54 lines
2.0 KiB
Rust
54 lines
2.0 KiB
Rust
//! Per-destination path MTU state shared with the TCP MSS clamp.
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//!
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//! Every writer, the release paths and the expiry pass live in the node;
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//! the TUN reader and writer threads only read the map.
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use crate::FipsAddress;
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use std::collections::HashMap;
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use std::sync::{Arc, RwLock};
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/// One `path_mtu_lookup` entry: the MTU the TCP MSS clamp reads, plus how
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/// the entry is released.
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#[derive(Clone, Copy, Debug, PartialEq, Eq)]
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pub struct PathMtuEntry {
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/// Path MTU in bytes.
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pub mtu: u16,
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/// Unix ms at which a discovery `LookupResponse` supplied this value, or
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/// `None` for an entry that some event releases instead of a timer.
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///
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/// The discovery carrier is the one with no release path: it writes an
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/// entry for a destination this node may never open a session with, and
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/// all three callers of `path_mtu_lookup_release` fire on session state.
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/// A link MTU this node derived from its own transport, and a value
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/// learned inside a session, are both released by an event that says the
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/// thing they describe is gone, so they carry no deadline.
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pub learned_ms: Option<u64>,
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}
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impl PathMtuEntry {
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/// An entry released by an event rather than a timer: a locally derived
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/// link MTU, or a value learned inside a session.
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pub fn held(mtu: u16) -> Self {
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Self {
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mtu,
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learned_ms: None,
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}
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}
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/// A remote party's claim stored at `at_ms` for a destination with no
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/// other release path. Expires.
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pub fn learned(mtu: u16, at_ms: u64) -> Self {
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Self {
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mtu,
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learned_ms: Some(at_ms),
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}
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}
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}
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/// Read-only handle to the per-destination path MTU map. Populated by
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/// the discovery handler on `LookupResponse`; read by the TUN reader
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/// (outbound clamp) and writer (inbound clamp) at TCP MSS clamp time.
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/// Keyed by [`FipsAddress`] (16 bytes, the IPv6 form of a fips peer
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/// address).
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pub type PathMtuLookup = Arc<RwLock<HashMap<FipsAddress, PathMtuEntry>>>;
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