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refactor(net): bitmap-backed TCP/UDP local port allocation #700

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665d965
refactor(net): bitmap-backed TCP/UDP local port allocation
ytakano Jun 22, 2026
9baa6f4
fmt
ytakano Jun 22, 2026
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1 change: 1 addition & 0 deletions awkernel_lib/src/net.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,7 @@ pub mod ipv6;
pub mod multicast;
pub mod net_device;
mod port_alloc;
mod port_bitmap;
pub mod tcp;
pub mod tcp_listener;
pub mod tcp_stream;
Expand Down
153 changes: 34 additions & 119 deletions awkernel_lib/src/net/port_alloc.rs
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Original file line number Diff line number Diff line change
@@ -1,10 +1,11 @@
#![cfg(not(feature = "std"))]

use alloc::collections::{btree_map::Entry, BTreeMap, BTreeSet};

use crate::sync::{mcs::MCSNode, mutex::Mutex};

use super::tcp::TcpPort;
use super::{
port_bitmap::{TcpPortSet, UdpPortSet},
tcp::TcpPort,
};

/// RAII handle for a claimed UDP port. Frees the port from [`PORT_ALLOC`] on drop,
/// so the port is released on any error path between claiming it and constructing
Expand All @@ -30,72 +31,37 @@ impl Drop for UdpPort {
}
}

struct TcpPortsInner {
map: BTreeMap<u16, u64>,
cursor: u16,
}

struct UdpPortsInner {
set: BTreeSet<u16>,
cursor: u16,
}

pub(super) struct PortAllocator {
tcp_ipv4: Mutex<TcpPortsInner>,
tcp_ipv6: Mutex<TcpPortsInner>,
udp_ipv4: Mutex<UdpPortsInner>,
udp_ipv6: Mutex<UdpPortsInner>,
tcp_ipv4: Mutex<TcpPortSet>,
tcp_ipv6: Mutex<TcpPortSet>,
udp_ipv4: Mutex<UdpPortSet>,
udp_ipv6: Mutex<UdpPortSet>,
}

pub(super) static PORT_ALLOC: PortAllocator = PortAllocator::new();

impl PortAllocator {
pub(super) const fn new() -> Self {
Self {
tcp_ipv4: Mutex::new(TcpPortsInner {
map: BTreeMap::new(),
cursor: u16::MAX >> 2,
}),
tcp_ipv6: Mutex::new(TcpPortsInner {
map: BTreeMap::new(),
cursor: u16::MAX >> 2,
}),
udp_ipv4: Mutex::new(UdpPortsInner {
set: BTreeSet::new(),
cursor: u16::MAX >> 2,
}),
udp_ipv6: Mutex::new(UdpPortsInner {
set: BTreeSet::new(),
cursor: u16::MAX >> 2,
}),
tcp_ipv4: Mutex::new(TcpPortSet::new()),
tcp_ipv6: Mutex::new(TcpPortSet::new()),
udp_ipv4: Mutex::new(UdpPortSet::new()),
udp_ipv6: Mutex::new(UdpPortSet::new()),
}
}

/// Allocate an ephemeral TCP IPv4 port.
pub(super) fn get_ephemeral_tcp_ipv4(&self) -> Option<TcpPort> {
let mut node = MCSNode::new();
let mut ports = self.tcp_ipv4.lock(&mut node);
for _ in 0..(u16::MAX >> 2) {
ports.cursor = ports.cursor.wrapping_add(1);
let port = if ports.cursor == 0 {
u16::MAX >> 2
} else {
ports.cursor
};
if let Entry::Vacant(e) = ports.map.entry(port) {
e.insert(1);
return Some(TcpPort::new(port, true));
}
}
None
ports.alloc_ephemeral().map(|port| TcpPort::new(port, true))
}

/// Claim a specific TCP IPv4 port. Returns `None` if the port is already in use.
pub(super) fn try_claim_tcp_ipv4(&self, port: u16) -> Option<TcpPort> {
let mut node = MCSNode::new();
let mut ports = self.tcp_ipv4.lock(&mut node);
if let Entry::Vacant(e) = ports.map.entry(port) {
e.insert(1);
if ports.try_claim(port) {
Some(TcpPort::new(port, true))
} else {
None
Expand All @@ -106,51 +72,31 @@ impl PortAllocator {
pub(super) fn increment_ref_tcp_ipv4(&self, port: u16) -> TcpPort {
let mut node = MCSNode::new();
let mut ports = self.tcp_ipv4.lock(&mut node);
if let Some(e) = ports.map.get_mut(&port) {
*e += 1;
} else {
ports.map.insert(port, 1);
}
ports.increment(port);
TcpPort::new(port, true)
}

/// Decrement the reference count for a TCP IPv4 port, freeing it when it reaches zero.
pub(super) fn decrement_ref_tcp_ipv4(&self, port: u16) {
let mut node = MCSNode::new();
let mut ports = self.tcp_ipv4.lock(&mut node);
if let Some(e) = ports.map.get_mut(&port) {
*e -= 1;
if *e == 0 {
ports.map.remove(&port);
}
}
ports.decrement(port);
}

/// Allocate an ephemeral TCP IPv6 port.
pub(super) fn get_ephemeral_tcp_ipv6(&self) -> Option<TcpPort> {
let mut node = MCSNode::new();
let mut ports = self.tcp_ipv6.lock(&mut node);
for _ in 0..(u16::MAX >> 2) {
ports.cursor = ports.cursor.wrapping_add(1);
let port = if ports.cursor == 0 {
u16::MAX >> 2
} else {
ports.cursor
};
if let Entry::Vacant(e) = ports.map.entry(port) {
e.insert(1);
return Some(TcpPort::new(port, false));
}
}
None
ports
.alloc_ephemeral()
.map(|port| TcpPort::new(port, false))
}

/// Claim a specific TCP IPv6 port. Returns `None` if the port is already in use.
pub(super) fn try_claim_tcp_ipv6(&self, port: u16) -> Option<TcpPort> {
let mut node = MCSNode::new();
let mut ports = self.tcp_ipv6.lock(&mut node);
if let Entry::Vacant(e) = ports.map.entry(port) {
e.insert(1);
if ports.try_claim(port) {
Some(TcpPort::new(port, false))
} else {
None
Expand All @@ -161,52 +107,32 @@ impl PortAllocator {
pub(super) fn increment_ref_tcp_ipv6(&self, port: u16) -> TcpPort {
let mut node = MCSNode::new();
let mut ports = self.tcp_ipv6.lock(&mut node);
if let Some(e) = ports.map.get_mut(&port) {
*e += 1;
} else {
ports.map.insert(port, 1);
}
ports.increment(port);
TcpPort::new(port, false)
}

/// Decrement the reference count for a TCP IPv6 port, freeing it when it reaches zero.
pub(super) fn decrement_ref_tcp_ipv6(&self, port: u16) {
let mut node = MCSNode::new();
let mut ports = self.tcp_ipv6.lock(&mut node);
if let Some(e) = ports.map.get_mut(&port) {
*e -= 1;
if *e == 0 {
ports.map.remove(&port);
}
}
ports.decrement(port);
}

/// Allocate an ephemeral UDP IPv4 port.
pub(super) fn get_ephemeral_udp_ipv4(&self) -> Option<UdpPort> {
let mut node = MCSNode::new();
let mut ports = self.udp_ipv4.lock(&mut node);
for _ in 0..(u16::MAX >> 2) {
ports.cursor = ports.cursor.wrapping_add(1);
let port = if ports.cursor == 0 {
u16::MAX >> 2
} else {
ports.cursor
};
if ports.set.insert(port) {
return Some(UdpPort {
port,
is_ipv4: true,
});
}
}
None
ports.alloc_ephemeral().map(|port| UdpPort {
port,
is_ipv4: true,
})
}

/// Claim a specific UDP IPv4 port. Returns `None` if the port is already in use.
pub(super) fn try_claim_udp_ipv4(&self, port: u16) -> Option<UdpPort> {
let mut node = MCSNode::new();
let mut ports = self.udp_ipv4.lock(&mut node);
if ports.set.insert(port) {
if ports.try_claim(port) {
Some(UdpPort {
port,
is_ipv4: true,
Expand All @@ -220,35 +146,24 @@ impl PortAllocator {
pub(super) fn free_udp_ipv4(&self, port: u16) {
let mut node = MCSNode::new();
let mut ports = self.udp_ipv4.lock(&mut node);
ports.set.remove(&port);
ports.free(port);
}

/// Allocate an ephemeral UDP IPv6 port.
pub(super) fn get_ephemeral_udp_ipv6(&self) -> Option<UdpPort> {
let mut node = MCSNode::new();
let mut ports = self.udp_ipv6.lock(&mut node);
for _ in 0..(u16::MAX >> 2) {
ports.cursor = ports.cursor.wrapping_add(1);
let port = if ports.cursor == 0 {
u16::MAX >> 2
} else {
ports.cursor
};
if ports.set.insert(port) {
return Some(UdpPort {
port,
is_ipv4: false,
});
}
}
None
ports.alloc_ephemeral().map(|port| UdpPort {
port,
is_ipv4: false,
})
}

/// Claim a specific UDP IPv6 port. Returns `None` if the port is already in use.
pub(super) fn try_claim_udp_ipv6(&self, port: u16) -> Option<UdpPort> {
let mut node = MCSNode::new();
let mut ports = self.udp_ipv6.lock(&mut node);
if ports.set.insert(port) {
if ports.try_claim(port) {
Some(UdpPort {
port,
is_ipv4: false,
Expand All @@ -262,6 +177,6 @@ impl PortAllocator {
pub(super) fn free_udp_ipv6(&self, port: u16) {
let mut node = MCSNode::new();
let mut ports = self.udp_ipv6.lock(&mut node);
ports.set.remove(&port);
ports.free(port);
}
}
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