diff --git a/Cargo.lock b/Cargo.lock
index f5fd22574..3299a2723 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -66,6 +66,15 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d92bec98840b8f03a5ff5413de5293bfcd8bf96467cf5452609f939ec6f5de16"
 
+[[package]]
+name = "aster-bigtcp"
+version = "0.1.0"
+dependencies = [
+ "keyable-arc",
+ "ostd",
+ "smoltcp",
+]
+
 [[package]]
 name = "aster-block"
 version = "0.1.0"
@@ -144,6 +153,7 @@ version = "0.1.0"
 dependencies = [
  "align_ext",
  "ascii",
+ "aster-bigtcp",
  "aster-block",
  "aster-console",
  "aster-framebuffer",
@@ -179,7 +189,6 @@ dependencies = [
  "ostd",
  "paste",
  "rand",
- "smoltcp",
  "spin 0.9.8",
  "static_assertions",
  "takeable",
diff --git a/Cargo.toml b/Cargo.toml
index 64ffc7e58..0bda9ac7b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -24,6 +24,7 @@ members = [
     "kernel/libs/aster-rights",
     "kernel/libs/aster-rights-proc",
     "kernel/libs/aster-util",
+    "kernel/libs/aster-bigtcp",
     "kernel/libs/keyable-arc",
     "kernel/libs/typeflags",
     "kernel/libs/typeflags-util",
diff --git a/Makefile b/Makefile
index 5559f12c2..bb2285303 100644
--- a/Makefile
+++ b/Makefile
@@ -126,7 +126,8 @@ OSDK_CRATES := \
 	kernel/comps/network \
 	kernel/comps/time \
 	kernel/comps/virtio \
-	kernel/libs/aster-util
+	kernel/libs/aster-util \
+	kernel/libs/aster-bigtcp
 
 .PHONY: all
 all: build
diff --git a/kernel/Cargo.toml b/kernel/Cargo.toml
index 1fbc860c9..d4369885c 100644
--- a/kernel/Cargo.toml
+++ b/kernel/Cargo.toml
@@ -22,6 +22,7 @@ typeflags = { path = "libs/typeflags" }
 typeflags-util = { path = "libs/typeflags-util" }
 aster-rights-proc = { path = "libs/aster-rights-proc" }
 aster-util = { path = "libs/aster-util" }
+aster-bigtcp = { path = "libs/aster-bigtcp" }
 id-alloc = { path = "../ostd/libs/id-alloc" }
 int-to-c-enum = { path = "libs/int-to-c-enum" }
 cpio-decoder = { path = "libs/cpio-decoder" }
@@ -29,20 +30,6 @@ ascii = { version = "1.1", default-features = false, features = ["alloc"] }
 intrusive-collections = "0.9.5"
 paste = "1.0"
 time = { version = "0.3", default-features = false, features = ["alloc"] }
-smoltcp = { git = "https://github.com/smoltcp-rs/smoltcp", rev = "dc08e0b", default-features = false, features = [
-    "alloc",
-    "log",
-    "medium-ethernet",
-    "medium-ip",
-    "proto-dhcpv4",
-    "proto-ipv4",
-    "proto-igmp",
-    "socket-icmp",
-    "socket-udp",
-    "socket-tcp",
-    "socket-raw",
-    "socket-dhcpv4",
-] }
 tdx-guest = { version = "0.1.7", optional = true }
 
 # parse elf file
diff --git a/kernel/libs/aster-bigtcp/Cargo.toml b/kernel/libs/aster-bigtcp/Cargo.toml
new file mode 100644
index 000000000..793265de4
--- /dev/null
+++ b/kernel/libs/aster-bigtcp/Cargo.toml
@@ -0,0 +1,24 @@
+[package]
+name = "aster-bigtcp"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+keyable-arc = { path = "../keyable-arc" }
+ostd = { path = "../../../ostd" }
+smoltcp = { git = "https://github.com/smoltcp-rs/smoltcp", rev = "dc08e0b", default-features = false, features = [
+    "alloc",
+    "log",
+    "medium-ethernet",
+    "medium-ip",
+    "proto-dhcpv4",
+    "proto-ipv4",
+    "proto-igmp",
+    "socket-icmp",
+    "socket-udp",
+    "socket-tcp",
+    "socket-raw",
+    "socket-dhcpv4",
+] }
diff --git a/kernel/src/net/iface/device.rs b/kernel/libs/aster-bigtcp/src/device.rs
similarity index 92%
rename from kernel/src/net/iface/device.rs
rename to kernel/libs/aster-bigtcp/src/device.rs
index 25725de9c..2b0e509e1 100644
--- a/kernel/src/net/iface/device.rs
+++ b/kernel/libs/aster-bigtcp/src/device.rs
@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MPL-2.0
 
-use smoltcp::phy::Device;
+pub use smoltcp::phy::{Device, Loopback, Medium};
 
 /// A trait that allows to obtain a mutable reference of [`Device`].
 ///
diff --git a/kernel/libs/aster-bigtcp/src/errors.rs b/kernel/libs/aster-bigtcp/src/errors.rs
new file mode 100644
index 000000000..57d7e75fc
--- /dev/null
+++ b/kernel/libs/aster-bigtcp/src/errors.rs
@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: MPL-2.0
+
+/// An error describing the reason why `bind` failed.
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+pub enum BindError {
+    /// All ephemeral ports is exhausted.
+    Exhausted,
+    /// The specified address is in use.
+    InUse,
+}
+
+pub mod tcp {
+    pub use smoltcp::socket::tcp::{ConnectError, ListenError, RecvError, SendError};
+}
+
+pub mod udp {
+    pub use smoltcp::socket::udp::{RecvError, SendError};
+}
diff --git a/kernel/src/net/iface/common.rs b/kernel/libs/aster-bigtcp/src/iface/common.rs
similarity index 84%
rename from kernel/src/net/iface/common.rs
rename to kernel/libs/aster-bigtcp/src/iface/common.rs
index 492e73294..3ab7f1862 100644
--- a/kernel/src/net/iface/common.rs
+++ b/kernel/libs/aster-bigtcp/src/iface/common.rs
@@ -1,24 +1,30 @@
 // SPDX-License-Identifier: MPL-2.0
 
-use alloc::collections::btree_map::Entry;
+use alloc::{
+    boxed::Box,
+    collections::{
+        btree_map::{BTreeMap, Entry},
+        btree_set::BTreeSet,
+    },
+    sync::Arc,
+    vec::Vec,
+};
 
 use keyable_arc::KeyableArc;
-use ostd::sync::LocalIrqDisabled;
+use ostd::sync::{LocalIrqDisabled, RwLock, SpinLock, SpinLockGuard};
 use smoltcp::{
     iface::{SocketHandle, SocketSet},
     phy::Device,
+    wire::Ipv4Address,
 };
 
-use super::{
-    any_socket::{AnyBoundSocketInner, AnyRawSocket, AnyUnboundSocket, SocketFamily},
-    ext::IfaceExt,
-    time::get_network_timestamp,
-    util::BindPortConfig,
-    AnyBoundSocket, Iface,
+use super::{port::BindPortConfig, time::get_network_timestamp, Iface};
+use crate::{
+    errors::BindError,
+    socket::{AnyBoundSocket, AnyBoundSocketInner, AnyRawSocket, AnyUnboundSocket, SocketFamily},
 };
-use crate::{net::socket::ip::Ipv4Address, prelude::*};
 
-pub struct IfaceCommon<E = IfaceExt> {
+pub struct IfaceCommon<E> {
     interface: SpinLock<smoltcp::iface::Interface>,
     sockets: SpinLock<SocketSet<'static>>,
     used_ports: RwLock<BTreeMap<u16, usize>>,
@@ -44,14 +50,14 @@ impl<E> IfaceCommon<E> {
     /// Acquires the lock to the interface.
     ///
     /// *Lock ordering:* [`Self::sockets`] first, [`Self::interface`] second.
-    pub(super) fn interface(&self) -> SpinLockGuard<smoltcp::iface::Interface, LocalIrqDisabled> {
+    pub(crate) fn interface(&self) -> SpinLockGuard<smoltcp::iface::Interface, LocalIrqDisabled> {
         self.interface.disable_irq().lock()
     }
 
     /// Acuqires the lock to the sockets.
     ///
     /// *Lock ordering:* [`Self::sockets`] first, [`Self::interface`] second.
-    pub(super) fn sockets(
+    pub(crate) fn sockets(
         &self,
     ) -> SpinLockGuard<smoltcp::iface::SocketSet<'static>, LocalIrqDisabled> {
         self.sockets.disable_irq().lock()
@@ -62,34 +68,35 @@ impl<E> IfaceCommon<E> {
     }
 
     /// Alloc an unused port range from 49152 ~ 65535 (According to smoltcp docs)
-    fn alloc_ephemeral_port(&self) -> Result<u16> {
+    fn alloc_ephemeral_port(&self) -> Option<u16> {
         let mut used_ports = self.used_ports.write();
         for port in IP_LOCAL_PORT_START..=IP_LOCAL_PORT_END {
             if let Entry::Vacant(e) = used_ports.entry(port) {
                 e.insert(0);
-                return Ok(port);
+                return Some(port);
             }
         }
-        return_errno_with_message!(Errno::EAGAIN, "no ephemeral port is available");
+        None
     }
 
-    fn bind_port(&self, port: u16, can_reuse: bool) -> Result<()> {
+    #[must_use]
+    fn bind_port(&self, port: u16, can_reuse: bool) -> bool {
         let mut used_ports = self.used_ports.write();
         if let Some(used_times) = used_ports.get_mut(&port) {
             if *used_times == 0 || can_reuse {
                 // FIXME: Check if the previous socket was bound with SO_REUSEADDR.
                 *used_times += 1;
             } else {
-                return_errno_with_message!(Errno::EADDRINUSE, "the address is already in use");
+                return false;
             }
         } else {
             used_ports.insert(port, 1);
         }
-        Ok(())
+        true
     }
 
     /// Release port number so the port can be used again. For reused port, the port may still be in use.
-    pub(super) fn release_port(&self, port: u16) {
+    pub(crate) fn release_port(&self, port: u16) {
         let mut used_ports = self.used_ports.write();
         if let Some(used_times) = used_ports.remove(&port) {
             if used_times != 1 {
@@ -103,17 +110,17 @@ impl<E> IfaceCommon<E> {
         iface: Arc<dyn Iface<E>>,
         socket: Box<AnyUnboundSocket>,
         config: BindPortConfig,
-    ) -> core::result::Result<AnyBoundSocket<E>, (Error, Box<AnyUnboundSocket>)> {
+    ) -> core::result::Result<AnyBoundSocket<E>, (BindError, Box<AnyUnboundSocket>)> {
         let port = if let Some(port) = config.port() {
             port
         } else {
             match self.alloc_ephemeral_port() {
-                Ok(port) => port,
-                Err(err) => return Err((err, socket)),
+                Some(port) => port,
+                None => return Err((BindError::Exhausted, socket)),
             }
         };
-        if let Some(err) = self.bind_port(port, config.can_reuse()).err() {
-            return Err((err, socket));
+        if !self.bind_port(port, config.can_reuse()) {
+            return Err((BindError::InUse, socket));
         }
 
         let (handle, socket_family, observer) = match socket.into_raw() {
@@ -135,7 +142,7 @@ impl<E> IfaceCommon<E> {
     }
 
     /// Remove a socket from the interface
-    pub(super) fn remove_socket(&self, handle: SocketHandle) {
+    pub(crate) fn remove_socket(&self, handle: SocketHandle) {
         self.sockets.disable_irq().lock().remove(handle);
     }
 
@@ -209,7 +216,7 @@ impl<E> IfaceCommon<E> {
         assert!(inserted);
     }
 
-    pub(super) fn remove_bound_socket_now(&self, socket: &Arc<AnyBoundSocketInner<E>>) {
+    pub(crate) fn remove_bound_socket_now(&self, socket: &Arc<AnyBoundSocketInner<E>>) {
         let keyable_socket = KeyableArc::from(socket.clone());
 
         let removed = self
@@ -219,7 +226,7 @@ impl<E> IfaceCommon<E> {
         assert!(removed);
     }
 
-    pub(super) fn remove_bound_socket_when_closed(&self, socket: &Arc<AnyBoundSocketInner<E>>) {
+    pub(crate) fn remove_bound_socket_when_closed(&self, socket: &Arc<AnyBoundSocketInner<E>>) {
         let keyable_socket = KeyableArc::from(socket.clone());
 
         let removed = self
diff --git a/kernel/libs/aster-bigtcp/src/iface/iface.rs b/kernel/libs/aster-bigtcp/src/iface/iface.rs
new file mode 100644
index 000000000..01d06762f
--- /dev/null
+++ b/kernel/libs/aster-bigtcp/src/iface/iface.rs
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use alloc::{boxed::Box, sync::Arc};
+
+use smoltcp::wire::Ipv4Address;
+
+use super::port::BindPortConfig;
+use crate::{
+    errors::BindError,
+    socket::{AnyBoundSocket, AnyUnboundSocket},
+};
+
+/// A network interface.
+///
+/// A network interface (abbreviated as iface) is a hardware or software component that connects a
+/// computer to a network. Network interfaces can be physical components like Ethernet ports or
+/// wireless adapters. They can also be virtual interfaces created by software, such as virtual
+/// private network (VPN) connections.
+pub trait Iface<E>: internal::IfaceInternal<E> + Send + Sync {
+    /// Transmits or receives packets queued in the iface, and updates socket status accordingly.
+    ///
+    /// The `schedule_next_poll` callback is invoked with the time at which the next poll should be
+    /// performed, or `None` if no next poll is required. It's up to the caller to determine the
+    /// mechanism to ensure that the next poll happens at the right time (e.g. by setting a timer).
+    fn raw_poll(&self, schedule_next_poll: &dyn Fn(Option<u64>));
+}
+
+impl<E> dyn Iface<E> {
+    /// Gets the extension of the iface.
+    pub fn ext(&self) -> &E {
+        self.common().ext()
+    }
+
+    /// Binds a socket to the iface.
+    ///
+    /// After binding the socket to the iface, the iface will handle all packets to and from the
+    /// socket.
+    ///
+    /// If [`BindPortConfig::Ephemeral`] is specified, the iface will pick up an ephemeral port for
+    /// the socket.
+    ///
+    /// FIXME: The reason for binding the socket and the iface together is because there are
+    /// limitations inside smoltcp. See discussion at
+    /// <https://github.com/smoltcp-rs/smoltcp/issues/779>.
+    pub fn bind_socket(
+        self: &Arc<Self>,
+        socket: Box<AnyUnboundSocket>,
+        config: BindPortConfig,
+    ) -> core::result::Result<AnyBoundSocket<E>, (BindError, Box<AnyUnboundSocket>)> {
+        let common = self.common();
+        common.bind_socket(self.clone(), socket, config)
+    }
+
+    /// Gets the IPv4 address of the iface, if any.
+    ///
+    /// FIXME: One iface may have multiple IPv4 addresses.
+    pub fn ipv4_addr(&self) -> Option<Ipv4Address> {
+        self.common().ipv4_addr()
+    }
+}
+
+pub(super) mod internal {
+    use crate::iface::common::IfaceCommon;
+
+    /// An internal trait that abstracts the common part of different ifaces.
+    pub trait IfaceInternal<E> {
+        fn common(&self) -> &IfaceCommon<E>;
+    }
+}
diff --git a/kernel/libs/aster-bigtcp/src/iface/mod.rs b/kernel/libs/aster-bigtcp/src/iface/mod.rs
new file mode 100644
index 000000000..744699cbf
--- /dev/null
+++ b/kernel/libs/aster-bigtcp/src/iface/mod.rs
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: MPL-2.0
+
+mod common;
+#[allow(clippy::module_inception)]
+mod iface;
+mod phy;
+mod port;
+mod time;
+
+pub use iface::Iface;
+pub use phy::{EtherIface, IpIface};
+pub use port::BindPortConfig;
diff --git a/kernel/src/net/iface/ether.rs b/kernel/libs/aster-bigtcp/src/iface/phy/ether.rs
similarity index 80%
rename from kernel/src/net/iface/ether.rs
rename to kernel/libs/aster-bigtcp/src/iface/phy/ether.rs
index 045dcf615..dc7016a63 100644
--- a/kernel/src/net/iface/ether.rs
+++ b/kernel/libs/aster-bigtcp/src/iface/phy/ether.rs
@@ -1,17 +1,20 @@
 // SPDX-License-Identifier: MPL-2.0
 
-pub use smoltcp::wire::EthernetAddress;
+use alloc::sync::Arc;
+
+use ostd::prelude::*;
 use smoltcp::{
     iface::{Config, SocketHandle, SocketSet},
     socket::dhcpv4,
-    wire::{self, IpCidr},
+    wire::{self, EthernetAddress, IpCidr},
 };
 
-use super::{
-    common::IfaceCommon, device::WithDevice, internal::IfaceInternal, time::get_network_timestamp,
-    Iface,
+use crate::{
+    device::WithDevice,
+    iface::{
+        common::IfaceCommon, iface::internal::IfaceInternal, time::get_network_timestamp, Iface,
+    },
 };
-use crate::prelude::*;
 
 pub struct EtherIface<D: WithDevice, E> {
     driver: D,
@@ -51,18 +54,15 @@ impl<D: WithDevice, E> EtherIface<D, E> {
     pub fn process_dhcp(&self) {
         let mut socket_set = self.common.sockets();
         let dhcp_socket: &mut dhcpv4::Socket = socket_set.get_mut(self.dhcp_handle);
-        let config = if let Some(event) = dhcp_socket.poll() {
-            debug!("event = {:?}", event);
-            if let dhcpv4::Event::Configured(config) = event {
-                config
-            } else {
-                return;
-            }
-        } else {
+
+        let Some(dhcpv4::Event::Configured(config)) = dhcp_socket.poll() else {
             return;
         };
         let ip_addr = IpCidr::Ipv4(config.address);
+
         let mut interface = self.common.interface();
+
+        println!("[DHCP] Local IP address: {:?}", ip_addr,);
         interface.update_ip_addrs(|ipaddrs| {
             if let Some(addr) = ipaddrs.iter_mut().next() {
                 // already has ipaddrs
@@ -72,12 +72,9 @@ impl<D: WithDevice, E> EtherIface<D, E> {
                 ipaddrs.push(ip_addr).unwrap();
             }
         });
-        println!(
-            "DHCP update IP address: {:?}",
-            interface.ipv4_addr().unwrap()
-        );
+
         if let Some(router) = config.router {
-            println!("Default router address: {:?}", router);
+            println!("[DHCP] Router IP address: {:?}", router);
             interface
                 .routes_mut()
                 .add_default_ipv4_route(router)
diff --git a/kernel/src/net/iface/ip.rs b/kernel/libs/aster-bigtcp/src/iface/phy/ip.rs
similarity index 83%
rename from kernel/src/net/iface/ip.rs
rename to kernel/libs/aster-bigtcp/src/iface/phy/ip.rs
index 950da42c8..d888c5ac3 100644
--- a/kernel/src/net/iface/ip.rs
+++ b/kernel/libs/aster-bigtcp/src/iface/phy/ip.rs
@@ -1,10 +1,15 @@
 // SPDX-License-Identifier: MPL-2.0
 
-use smoltcp::iface::Config;
-pub use smoltcp::wire::{IpAddress, IpCidr, Ipv4Address};
+use alloc::sync::Arc;
 
-use super::{common::IfaceCommon, device::WithDevice, internal::IfaceInternal, Iface};
-use crate::{net::iface::time::get_network_timestamp, prelude::*};
+use smoltcp::{iface::Config, wire::IpCidr};
+
+use crate::{
+    device::WithDevice,
+    iface::{
+        common::IfaceCommon, iface::internal::IfaceInternal, time::get_network_timestamp, Iface,
+    },
+};
 
 pub struct IpIface<D: WithDevice, E> {
     driver: D,
diff --git a/kernel/libs/aster-bigtcp/src/iface/phy/mod.rs b/kernel/libs/aster-bigtcp/src/iface/phy/mod.rs
new file mode 100644
index 000000000..60fc8abf7
--- /dev/null
+++ b/kernel/libs/aster-bigtcp/src/iface/phy/mod.rs
@@ -0,0 +1,7 @@
+// SPDX-License-Identifier: MPL-2.0
+
+mod ether;
+mod ip;
+
+pub use ether::EtherIface;
+pub use ip::IpIface;
diff --git a/kernel/libs/aster-bigtcp/src/iface/port.rs b/kernel/libs/aster-bigtcp/src/iface/port.rs
new file mode 100644
index 000000000..88b70d52b
--- /dev/null
+++ b/kernel/libs/aster-bigtcp/src/iface/port.rs
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: MPL-2.0
+
+/// The configuration using for bind to a TCP/UDP port.
+pub enum BindPortConfig {
+    /// Binds to the specified non-reusable port.
+    CanReuse(u16),
+    /// Binds to the specified reusable port.
+    Specified(u16),
+    /// Allocates an ephemeral port to bind.
+    Ephemeral,
+}
+
+impl BindPortConfig {
+    /// Creates new configuration using for bind to a TCP/UDP port.
+    ///
+    /// # Panics
+    ///
+    /// This method will panic if `port` is zero (indicating that an ephemeral port should be
+    /// allocated) and `can_use` is true. This makes no sense because new ephemeral ports are
+    /// always not reused.
+    pub fn new(port: u16, can_reuse: bool) -> Self {
+        match (port, can_reuse) {
+            (0, _) => {
+                assert!(!can_reuse);
+                Self::Ephemeral
+            }
+            (_, true) => Self::CanReuse(port),
+            (_, false) => Self::Specified(port),
+        }
+    }
+
+    pub(super) fn can_reuse(&self) -> bool {
+        matches!(self, Self::CanReuse(_))
+    }
+
+    pub(super) fn port(&self) -> Option<u16> {
+        match self {
+            Self::CanReuse(port) | Self::Specified(port) => Some(*port),
+            Self::Ephemeral => None,
+        }
+    }
+}
diff --git a/kernel/src/net/iface/time.rs b/kernel/libs/aster-bigtcp/src/iface/time.rs
similarity index 100%
rename from kernel/src/net/iface/time.rs
rename to kernel/libs/aster-bigtcp/src/iface/time.rs
diff --git a/kernel/libs/aster-bigtcp/src/lib.rs b/kernel/libs/aster-bigtcp/src/lib.rs
new file mode 100644
index 000000000..ef6a3be6f
--- /dev/null
+++ b/kernel/libs/aster-bigtcp/src/lib.rs
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: MPL-2.0
+
+//! _bigtcp_ is a crate that wraps [`smoltcp`].
+//!
+//! [`smoltcp`] is designed for embedded systems where the number of sockets is always small. It
+//! turns out that such a design cannot satisfy the need to implement the network stack of a
+//! general-purpose OS kernel, in terms of flexibility and efficiency.
+//!
+//! The short-term goal of _bigtcp_ is to reuse the powerful TCP implementation of _smoltcp_, while
+//! reimplementing Ethernet and IP protocols to increase the flexibility and performance of packet
+//! dispatching.
+
+#![no_std]
+#![deny(unsafe_code)]
+#![feature(btree_extract_if)]
+
+pub mod device;
+pub mod errors;
+pub mod iface;
+pub mod socket;
+pub mod wire;
+
+extern crate alloc;
diff --git a/kernel/src/net/iface/any_socket.rs b/kernel/libs/aster-bigtcp/src/socket/bound.rs
similarity index 54%
rename from kernel/src/net/iface/any_socket.rs
rename to kernel/libs/aster-bigtcp/src/socket/bound.rs
index 97379fc5e..cc7b0c303 100644
--- a/kernel/src/net/iface/any_socket.rs
+++ b/kernel/libs/aster-bigtcp/src/socket/bound.rs
@@ -1,77 +1,30 @@
 // SPDX-License-Identifier: MPL-2.0
 
-use super::{ext::IfaceExt, Iface};
-use crate::{
-    events::Observer,
-    net::socket::ip::{IpAddress, IpEndpoint},
-    prelude::*,
+use alloc::sync::{Arc, Weak};
+
+use ostd::sync::RwLock;
+use smoltcp::{
+    socket::tcp::ConnectError,
+    wire::{IpAddress, IpEndpoint},
 };
 
-pub type RawTcpSocket = smoltcp::socket::tcp::Socket<'static>;
-pub type RawUdpSocket = smoltcp::socket::udp::Socket<'static>;
+use super::{event::SocketEventObserver, RawTcpSocket, RawUdpSocket};
+use crate::iface::Iface;
 
-pub struct AnyUnboundSocket {
-    socket_family: AnyRawSocket,
-    observer: Weak<dyn Observer<()>>,
-}
-
-#[allow(clippy::large_enum_variant)]
-pub(super) enum AnyRawSocket {
-    Tcp(RawTcpSocket),
-    Udp(RawUdpSocket),
-}
-
-pub(super) enum SocketFamily {
+pub(crate) enum SocketFamily {
     Tcp,
     Udp,
 }
 
-impl AnyUnboundSocket {
-    pub fn new_tcp(observer: Weak<dyn Observer<()>>) -> Self {
-        let raw_tcp_socket = {
-            let rx_buffer = smoltcp::socket::tcp::SocketBuffer::new(vec![0u8; TCP_RECV_BUF_LEN]);
-            let tx_buffer = smoltcp::socket::tcp::SocketBuffer::new(vec![0u8; TCP_SEND_BUF_LEN]);
-            RawTcpSocket::new(rx_buffer, tx_buffer)
-        };
-        AnyUnboundSocket {
-            socket_family: AnyRawSocket::Tcp(raw_tcp_socket),
-            observer,
-        }
-    }
-
-    pub fn new_udp(observer: Weak<dyn Observer<()>>) -> Self {
-        let raw_udp_socket = {
-            let metadata = smoltcp::socket::udp::PacketMetadata::EMPTY;
-            let rx_buffer = smoltcp::socket::udp::PacketBuffer::new(
-                vec![metadata; UDP_METADATA_LEN],
-                vec![0u8; UDP_RECV_PAYLOAD_LEN],
-            );
-            let tx_buffer = smoltcp::socket::udp::PacketBuffer::new(
-                vec![metadata; UDP_METADATA_LEN],
-                vec![0u8; UDP_SEND_PAYLOAD_LEN],
-            );
-            RawUdpSocket::new(rx_buffer, tx_buffer)
-        };
-        AnyUnboundSocket {
-            socket_family: AnyRawSocket::Udp(raw_udp_socket),
-            observer,
-        }
-    }
-
-    pub(super) fn into_raw(self) -> (AnyRawSocket, Weak<dyn Observer<()>>) {
-        (self.socket_family, self.observer)
-    }
-}
-
-pub struct AnyBoundSocket<E = IfaceExt>(Arc<AnyBoundSocketInner<E>>);
+pub struct AnyBoundSocket<E>(Arc<AnyBoundSocketInner<E>>);
 
 impl<E> AnyBoundSocket<E> {
-    pub(super) fn new(
+    pub(crate) fn new(
         iface: Arc<dyn Iface<E>>,
         handle: smoltcp::iface::SocketHandle,
         port: u16,
         socket_family: SocketFamily,
-        observer: Weak<dyn Observer<()>>,
+        observer: Weak<dyn SocketEventObserver>,
     ) -> Self {
         Self(Arc::new(AnyBoundSocketInner {
             iface,
@@ -82,18 +35,18 @@ impl<E> AnyBoundSocket<E> {
         }))
     }
 
-    pub(super) fn inner(&self) -> &Arc<AnyBoundSocketInner<E>> {
+    pub(crate) fn inner(&self) -> &Arc<AnyBoundSocketInner<E>> {
         &self.0
     }
 
-    /// Set the observer whose `on_events` will be called when certain iface events happen. After
+    /// Sets the observer whose `on_events` will be called when certain iface events happen. After
     /// setting, the new observer will fire once immediately to avoid missing any events.
     ///
     /// If there is an existing observer, due to race conditions, this function does not guarantee
     /// that the old observer will never be called after the setting. Users should be aware of this
     /// and proactively handle the race conditions if necessary.
-    pub fn set_observer(&self, handler: Weak<dyn Observer<()>>) {
-        *self.0.observer.write() = handler;
+    pub fn set_observer(&self, new_observer: Weak<dyn SocketEventObserver>) {
+        *self.0.observer.write() = new_observer;
 
         self.0.on_iface_events();
     }
@@ -118,7 +71,7 @@ impl<E> AnyBoundSocket<E> {
     /// # Panics
     ///
     /// This method will panic if the socket is not a TCP socket.
-    pub fn do_connect(&self, remote_endpoint: IpEndpoint) -> Result<()> {
+    pub fn do_connect(&self, remote_endpoint: IpEndpoint) -> Result<(), ConnectError> {
         let common = self.iface().common();
 
         let mut sockets = common.sockets();
@@ -127,21 +80,7 @@ impl<E> AnyBoundSocket<E> {
         let mut iface = common.interface();
         let cx = iface.context();
 
-        // The only reason this method might fail is because we're trying to connect to an
-        // unspecified address (i.e. 0.0.0.0). We currently have no support for binding to,
-        // listening on, or connecting to the unspecified address.
-        //
-        // We assume the remote will just refuse to connect, so we return `ECONNREFUSED`.
-        socket
-            .connect(cx, remote_endpoint, self.0.port)
-            .map_err(|_| {
-                Error::with_message(
-                    Errno::ECONNREFUSED,
-                    "connecting to an unspecified address is not supported",
-                )
-            })?;
-
-        Ok(())
+        socket.connect(cx, remote_endpoint, self.0.port)
     }
 
     pub fn iface(&self) -> &Arc<dyn Iface<E>> {
@@ -162,22 +101,22 @@ impl<E> Drop for AnyBoundSocket<E> {
     }
 }
 
-pub(super) struct AnyBoundSocketInner<E> {
+pub(crate) struct AnyBoundSocketInner<E> {
     iface: Arc<dyn Iface<E>>,
     handle: smoltcp::iface::SocketHandle,
     port: u16,
     socket_family: SocketFamily,
-    observer: RwLock<Weak<dyn Observer<()>>>,
+    observer: RwLock<Weak<dyn SocketEventObserver>>,
 }
 
 impl<E> AnyBoundSocketInner<E> {
-    pub(super) fn on_iface_events(&self) {
+    pub(crate) fn on_iface_events(&self) {
         if let Some(observer) = Weak::upgrade(&*self.observer.read()) {
-            observer.on_events(&())
+            observer.on_events();
         }
     }
 
-    pub(super) fn is_closed(&self) -> bool {
+    pub(crate) fn is_closed(&self) -> bool {
         match self.socket_family {
             SocketFamily::Tcp => self.raw_with(|socket: &mut RawTcpSocket| {
                 socket.state() == smoltcp::socket::tcp::State::Closed
@@ -225,12 +164,3 @@ impl<E> Drop for AnyBoundSocketInner<E> {
         iface_common.release_port(self.port);
     }
 }
-
-// For TCP
-pub const TCP_RECV_BUF_LEN: usize = 65536;
-pub const TCP_SEND_BUF_LEN: usize = 65536;
-
-// For UDP
-pub const UDP_SEND_PAYLOAD_LEN: usize = 65536;
-pub const UDP_RECV_PAYLOAD_LEN: usize = 65536;
-const UDP_METADATA_LEN: usize = 256;
diff --git a/kernel/libs/aster-bigtcp/src/socket/event.rs b/kernel/libs/aster-bigtcp/src/socket/event.rs
new file mode 100644
index 000000000..d0770aae7
--- /dev/null
+++ b/kernel/libs/aster-bigtcp/src/socket/event.rs
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: MPL-2.0
+
+/// A observer that will be invoked whenever events occur on the socket.
+pub trait SocketEventObserver: Send + Sync {
+    /// Notifies that events occurred on the socket.
+    fn on_events(&self);
+}
+
+impl SocketEventObserver for () {
+    fn on_events(&self) {}
+}
diff --git a/kernel/libs/aster-bigtcp/src/socket/mod.rs b/kernel/libs/aster-bigtcp/src/socket/mod.rs
new file mode 100644
index 000000000..4c5929a32
--- /dev/null
+++ b/kernel/libs/aster-bigtcp/src/socket/mod.rs
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: MPL-2.0
+
+mod bound;
+mod event;
+mod unbound;
+
+pub use bound::AnyBoundSocket;
+pub(crate) use bound::{AnyBoundSocketInner, SocketFamily};
+pub use event::SocketEventObserver;
+pub(crate) use unbound::AnyRawSocket;
+pub use unbound::{
+    AnyUnboundSocket, TCP_RECV_BUF_LEN, TCP_SEND_BUF_LEN, UDP_RECV_PAYLOAD_LEN,
+    UDP_SEND_PAYLOAD_LEN,
+};
+
+pub type RawTcpSocket = smoltcp::socket::tcp::Socket<'static>;
+pub type RawUdpSocket = smoltcp::socket::udp::Socket<'static>;
diff --git a/kernel/libs/aster-bigtcp/src/socket/unbound.rs b/kernel/libs/aster-bigtcp/src/socket/unbound.rs
new file mode 100644
index 000000000..9fbba4e08
--- /dev/null
+++ b/kernel/libs/aster-bigtcp/src/socket/unbound.rs
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use alloc::{sync::Weak, vec};
+
+use super::{event::SocketEventObserver, RawTcpSocket, RawUdpSocket};
+
+pub struct AnyUnboundSocket {
+    socket_family: AnyRawSocket,
+    observer: Weak<dyn SocketEventObserver>,
+}
+
+#[allow(clippy::large_enum_variant)]
+pub(crate) enum AnyRawSocket {
+    Tcp(RawTcpSocket),
+    Udp(RawUdpSocket),
+}
+
+impl AnyUnboundSocket {
+    pub fn new_tcp(observer: Weak<dyn SocketEventObserver>) -> Self {
+        let raw_tcp_socket = {
+            let rx_buffer = smoltcp::socket::tcp::SocketBuffer::new(vec![0u8; TCP_RECV_BUF_LEN]);
+            let tx_buffer = smoltcp::socket::tcp::SocketBuffer::new(vec![0u8; TCP_SEND_BUF_LEN]);
+            RawTcpSocket::new(rx_buffer, tx_buffer)
+        };
+        AnyUnboundSocket {
+            socket_family: AnyRawSocket::Tcp(raw_tcp_socket),
+            observer,
+        }
+    }
+
+    pub fn new_udp(observer: Weak<dyn SocketEventObserver>) -> Self {
+        let raw_udp_socket = {
+            let metadata = smoltcp::socket::udp::PacketMetadata::EMPTY;
+            let rx_buffer = smoltcp::socket::udp::PacketBuffer::new(
+                vec![metadata; UDP_METADATA_LEN],
+                vec![0u8; UDP_RECV_PAYLOAD_LEN],
+            );
+            let tx_buffer = smoltcp::socket::udp::PacketBuffer::new(
+                vec![metadata; UDP_METADATA_LEN],
+                vec![0u8; UDP_SEND_PAYLOAD_LEN],
+            );
+            RawUdpSocket::new(rx_buffer, tx_buffer)
+        };
+        AnyUnboundSocket {
+            socket_family: AnyRawSocket::Udp(raw_udp_socket),
+            observer,
+        }
+    }
+
+    pub(crate) fn into_raw(self) -> (AnyRawSocket, Weak<dyn SocketEventObserver>) {
+        (self.socket_family, self.observer)
+    }
+}
+
+// For TCP
+pub const TCP_RECV_BUF_LEN: usize = 65536;
+pub const TCP_SEND_BUF_LEN: usize = 65536;
+
+// For UDP
+pub const UDP_SEND_PAYLOAD_LEN: usize = 65536;
+pub const UDP_RECV_PAYLOAD_LEN: usize = 65536;
+const UDP_METADATA_LEN: usize = 256;
diff --git a/kernel/libs/aster-bigtcp/src/wire.rs b/kernel/libs/aster-bigtcp/src/wire.rs
new file mode 100644
index 000000000..f640ed907
--- /dev/null
+++ b/kernel/libs/aster-bigtcp/src/wire.rs
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: MPL-2.0
+
+pub use smoltcp::wire::{EthernetAddress, IpAddress, IpCidr, IpEndpoint, Ipv4Address, Ipv4Cidr};
+
+pub type PortNum = u16;
diff --git a/kernel/src/net/iface/ext.rs b/kernel/src/net/iface/ext.rs
index 48ad7da95..07e00b64f 100644
--- a/kernel/src/net/iface/ext.rs
+++ b/kernel/src/net/iface/ext.rs
@@ -67,7 +67,7 @@ pub trait IfaceEx {
     fn poll(&self);
 }
 
-impl IfaceEx for dyn Iface<IfaceExt> {
+impl IfaceEx for Iface {
     fn name(&self) -> &str {
         &self.ext().name
     }
diff --git a/kernel/src/net/iface/init.rs b/kernel/src/net/iface/init.rs
index bbf406617..afa08f288 100644
--- a/kernel/src/net/iface/init.rs
+++ b/kernel/src/net/iface/init.rs
@@ -2,19 +2,17 @@
 
 use alloc::{borrow::ToOwned, sync::Arc};
 
+use aster_bigtcp::device::WithDevice;
 use ostd::sync::PreemptDisabled;
 use spin::Once;
 
-use super::{spawn_background_poll_thread, Iface};
+use super::{poll_ifaces, Iface};
 use crate::{
-    net::iface::{
-        device::WithDevice,
-        ext::{IfaceEx, IfaceExt},
-    },
+    net::iface::ext::{IfaceEx, IfaceExt},
     prelude::*,
 };
 
-pub static IFACES: Once<Vec<Arc<dyn Iface>>> = Once::new();
+pub static IFACES: Once<Vec<Arc<Iface>>> = Once::new();
 
 pub fn init() {
     IFACES.call_once(|| {
@@ -34,12 +32,11 @@ pub fn init() {
     poll_ifaces();
 }
 
-fn new_virtio() -> Arc<dyn Iface> {
+fn new_virtio() -> Arc<Iface> {
+    use aster_bigtcp::{iface::EtherIface, wire::EthernetAddress};
     use aster_network::AnyNetworkDevice;
     use aster_virtio::device::network::DEVICE_NAME;
 
-    use super::ether::{EtherIface, EthernetAddress};
-
     let virtio_net = aster_network::get_device(DEVICE_NAME).unwrap();
 
     let ether_addr = virtio_net.disable_irq().lock().mac_addr().0;
@@ -65,10 +62,12 @@ fn new_virtio() -> Arc<dyn Iface> {
     )
 }
 
-fn new_loopback() -> Arc<dyn Iface> {
-    use smoltcp::phy::{Loopback, Medium};
-
-    use super::ip::{IpAddress, IpCidr, IpIface, Ipv4Address};
+fn new_loopback() -> Arc<Iface> {
+    use aster_bigtcp::{
+        device::{Loopback, Medium},
+        iface::IpIface,
+        wire::{IpAddress, IpCidr, Ipv4Address},
+    };
 
     const LOOPBACK_ADDRESS: IpAddress = {
         let ipv4_addr = Ipv4Address::new(127, 0, 0, 1);
@@ -96,17 +95,3 @@ fn new_loopback() -> Arc<dyn Iface> {
         IfaceExt::new("lo".to_owned()),
     ) as _
 }
-
-pub fn lazy_init() {
-    for iface in IFACES.get().unwrap() {
-        spawn_background_poll_thread(iface.clone());
-    }
-}
-
-pub fn poll_ifaces() {
-    let ifaces = IFACES.get().unwrap();
-
-    for iface in ifaces.iter() {
-        iface.poll();
-    }
-}
diff --git a/kernel/src/net/iface/mod.rs b/kernel/src/net/iface/mod.rs
index 72c709f60..ce5674fea 100644
--- a/kernel/src/net/iface/mod.rs
+++ b/kernel/src/net/iface/mod.rs
@@ -1,82 +1,11 @@
 // SPDX-License-Identifier: MPL-2.0
 
-use self::common::IfaceCommon;
-use crate::prelude::*;
-
-mod any_socket;
-mod common;
-mod device;
-mod ether;
 mod ext;
 mod init;
-mod ip;
-mod time;
-mod util;
+mod poll;
 
-pub use any_socket::{
-    AnyBoundSocket, AnyUnboundSocket, RawTcpSocket, RawUdpSocket, TCP_RECV_BUF_LEN,
-    TCP_SEND_BUF_LEN, UDP_RECV_PAYLOAD_LEN, UDP_SEND_PAYLOAD_LEN,
-};
-pub use init::{init, lazy_init, poll_ifaces, IFACES};
-pub use smoltcp::wire::EthernetAddress;
-pub use util::{spawn_background_poll_thread, BindPortConfig};
+pub use init::{init, IFACES};
+pub use poll::{lazy_init, poll_ifaces};
 
-use crate::net::socket::ip::Ipv4Address;
-
-/// A network interface.
-///
-/// A network interface (abbreviated as iface) is a hardware or software component that connects a
-/// computer to a network. Network interfaces can be physical components like Ethernet ports or
-/// wireless adapters. They can also be virtual interfaces created by software, such as virtual
-/// private network (VPN) connections.
-pub trait Iface<E = ext::IfaceExt>: internal::IfaceInternal<E> + Send + Sync {
-    /// Transmits or receives packets queued in the iface, and updates socket status accordingly.
-    ///
-    /// The `schedule_next_poll` callback is invoked with the time at which the next poll should be
-    /// performed, or `None` if no next poll is required. It's up to the caller to determine the
-    /// mechanism to ensure that the next poll happens at the right time (e.g. by setting a timer).
-    fn raw_poll(&self, schedule_next_poll: &dyn Fn(Option<u64>));
-}
-
-impl<E> dyn Iface<E> {
-    /// Gets the extension of the iface.
-    pub fn ext(&self) -> &E {
-        self.common().ext()
-    }
-
-    /// Binds a socket to the iface.
-    ///
-    /// After binding the socket to the iface, the iface will handle all packets to and from the
-    /// socket.
-    ///
-    /// If [`BindPortConfig::Ephemeral`] is specified, the iface will pick up an ephemeral port for
-    /// the socket.
-    ///
-    /// FIXME: The reason for binding the socket and the iface together is because there are
-    /// limitations inside smoltcp. See discussion at
-    /// <https://github.com/smoltcp-rs/smoltcp/issues/779>.
-    pub fn bind_socket(
-        self: &Arc<Self>,
-        socket: Box<AnyUnboundSocket>,
-        config: BindPortConfig,
-    ) -> core::result::Result<AnyBoundSocket<E>, (Error, Box<AnyUnboundSocket>)> {
-        let common = self.common();
-        common.bind_socket(self.clone(), socket, config)
-    }
-
-    /// Gets the IPv4 address of the iface, if any.
-    ///
-    /// FIXME: One iface may have multiple IPv4 addresses.
-    pub fn ipv4_addr(&self) -> Option<Ipv4Address> {
-        self.common().ipv4_addr()
-    }
-}
-
-mod internal {
-    use super::*;
-
-    /// An internal trait that abstracts the common part of different ifaces.
-    pub trait IfaceInternal<E> {
-        fn common(&self) -> &IfaceCommon<E>;
-    }
-}
+pub type Iface = dyn aster_bigtcp::iface::Iface<ext::IfaceExt>;
+pub type AnyBoundSocket = aster_bigtcp::socket::AnyBoundSocket<ext::IfaceExt>;
diff --git a/kernel/src/net/iface/util.rs b/kernel/src/net/iface/poll.rs
similarity index 68%
rename from kernel/src/net/iface/util.rs
rename to kernel/src/net/iface/poll.rs
index 8416bc023..0a57e9d4d 100644
--- a/kernel/src/net/iface/util.rs
+++ b/kernel/src/net/iface/poll.rs
@@ -1,53 +1,35 @@
 // SPDX-License-Identifier: MPL-2.0
 
+use alloc::sync::Arc;
 use core::time::Duration;
 
+use log::trace;
 use ostd::{arch::timer::Jiffies, task::Priority};
 
-use super::{ext::IfaceEx, Iface};
+use super::{ext::IfaceEx, Iface, IFACES};
 use crate::{
-    prelude::*,
     thread::{
         kernel_thread::{KernelThreadExt, ThreadOptions},
         Thread,
     },
+    WaitTimeout,
 };
 
-pub enum BindPortConfig {
-    CanReuse(u16),
-    Specified(u16),
-    Ephemeral,
-}
-
-impl BindPortConfig {
-    pub fn new(port: u16, can_reuse: bool) -> Result<Self> {
-        let config = if port != 0 {
-            if can_reuse {
-                Self::CanReuse(port)
-            } else {
-                Self::Specified(port)
-            }
-        } else if can_reuse {
-            return_errno_with_message!(Errno::EINVAL, "invalid bind port config");
-        } else {
-            Self::Ephemeral
-        };
-        Ok(config)
-    }
-
-    pub(super) fn can_reuse(&self) -> bool {
-        matches!(self, Self::CanReuse(_))
-    }
-
-    pub(super) fn port(&self) -> Option<u16> {
-        match self {
-            Self::CanReuse(port) | Self::Specified(port) => Some(*port),
-            Self::Ephemeral => None,
-        }
+pub fn lazy_init() {
+    for iface in IFACES.get().unwrap() {
+        spawn_background_poll_thread(iface.clone());
     }
 }
 
-pub fn spawn_background_poll_thread(iface: Arc<dyn Iface>) {
+pub fn poll_ifaces() {
+    let ifaces = IFACES.get().unwrap();
+
+    for iface in ifaces.iter() {
+        iface.poll();
+    }
+}
+
+fn spawn_background_poll_thread(iface: Arc<Iface>) {
     let task_fn = move || {
         trace!("spawn background poll thread for {}", iface.name());
 
diff --git a/kernel/src/net/socket/ip/addr.rs b/kernel/src/net/socket/ip/addr.rs
index 047581138..169a6712d 100644
--- a/kernel/src/net/socket/ip/addr.rs
+++ b/kernel/src/net/socket/ip/addr.rs
@@ -1,11 +1,9 @@
 // SPDX-License-Identifier: MPL-2.0
 
-pub use smoltcp::wire::{IpAddress, IpEndpoint, Ipv4Address};
+use aster_bigtcp::wire::{IpAddress, IpEndpoint, Ipv4Address};
 
 use crate::{net::socket::SocketAddr, prelude::*, return_errno_with_message};
 
-pub type PortNum = u16;
-
 impl TryFrom<SocketAddr> for IpEndpoint {
     type Error = Error;
 
@@ -29,3 +27,11 @@ impl From<IpEndpoint> for SocketAddr {
         }
     }
 }
+
+/// A local endpoint, which indicates that the local endpoint is unspecified.
+///
+/// According to the Linux man pages and the Linux implementation, `getsockname()` will _not_ fail
+/// even if the socket is unbound. Instead, it will return an unspecified socket address. This
+/// unspecified endpoint helps with that.
+pub(super) const UNSPECIFIED_LOCAL_ENDPOINT: IpEndpoint =
+    IpEndpoint::new(IpAddress::Ipv4(Ipv4Address::UNSPECIFIED), 0);
diff --git a/kernel/src/net/socket/ip/common.rs b/kernel/src/net/socket/ip/common.rs
index c60d33644..113acea8f 100644
--- a/kernel/src/net/socket/ip/common.rs
+++ b/kernel/src/net/socket/ip/common.rs
@@ -1,12 +1,18 @@
 // SPDX-License-Identifier: MPL-2.0
 
-use super::{IpAddress, IpEndpoint};
+use aster_bigtcp::{
+    errors::BindError,
+    iface::BindPortConfig,
+    socket::AnyUnboundSocket,
+    wire::{IpAddress, IpEndpoint},
+};
+
 use crate::{
-    net::iface::{AnyBoundSocket, AnyUnboundSocket, BindPortConfig, Iface, IFACES},
+    net::iface::{AnyBoundSocket, Iface, IFACES},
     prelude::*,
 };
 
-pub fn get_iface_to_bind(ip_addr: &IpAddress) -> Option<Arc<dyn Iface>> {
+pub(super) fn get_iface_to_bind(ip_addr: &IpAddress) -> Option<Arc<Iface>> {
     let ifaces = IFACES.get().unwrap();
     let IpAddress::Ipv4(ipv4_addr) = ip_addr;
     ifaces
@@ -24,7 +30,7 @@ pub fn get_iface_to_bind(ip_addr: &IpAddress) -> Option<Arc<dyn Iface>> {
 /// Get a suitable iface to deal with sendto/connect request if the socket is not bound to an iface.
 /// If the remote address is the same as that of some iface, we will use the iface.
 /// Otherwise, we will use a default interface.
-fn get_ephemeral_iface(remote_ip_addr: &IpAddress) -> Arc<dyn Iface> {
+fn get_ephemeral_iface(remote_ip_addr: &IpAddress) -> Arc<Iface> {
     let ifaces = IFACES.get().unwrap();
     let IpAddress::Ipv4(remote_ipv4_addr) = remote_ip_addr;
     if let Some(iface) = ifaces.iter().find(|iface| {
@@ -48,18 +54,35 @@ pub(super) fn bind_socket(
     let iface = match get_iface_to_bind(&endpoint.addr) {
         Some(iface) => iface,
         None => {
-            let err = Error::with_message(Errno::EADDRNOTAVAIL, "Request iface is not available");
+            let err = Error::with_message(
+                Errno::EADDRNOTAVAIL,
+                "the address is not available from the local machine",
+            );
             return Err((err, unbound_socket));
         }
     };
-    let bind_port_config = match BindPortConfig::new(endpoint.port, can_reuse) {
-        Ok(config) => config,
-        Err(e) => return Err((e, unbound_socket)),
-    };
-    iface.bind_socket(unbound_socket, bind_port_config)
+
+    let bind_port_config = BindPortConfig::new(endpoint.port, can_reuse);
+
+    iface
+        .bind_socket(unbound_socket, bind_port_config)
+        .map_err(|(err, unbound)| (err.into(), unbound))
 }
 
-pub fn get_ephemeral_endpoint(remote_endpoint: &IpEndpoint) -> IpEndpoint {
+impl From<BindError> for Error {
+    fn from(value: BindError) -> Self {
+        match value {
+            BindError::Exhausted => {
+                Error::with_message(Errno::EAGAIN, "no ephemeral port is available")
+            }
+            BindError::InUse => {
+                Error::with_message(Errno::EADDRINUSE, "the address is already in use")
+            }
+        }
+    }
+}
+
+pub(super) fn get_ephemeral_endpoint(remote_endpoint: &IpEndpoint) -> IpEndpoint {
     let iface = get_ephemeral_iface(&remote_endpoint.addr);
     let ip_addr = iface.ipv4_addr().unwrap();
     IpEndpoint::new(IpAddress::Ipv4(ip_addr), 0)
diff --git a/kernel/src/net/socket/ip/datagram/bound.rs b/kernel/src/net/socket/ip/datagram/bound.rs
index 5181a826a..32592a4f6 100644
--- a/kernel/src/net/socket/ip/datagram/bound.rs
+++ b/kernel/src/net/socket/ip/datagram/bound.rs
@@ -1,14 +1,14 @@
 // SPDX-License-Identifier: MPL-2.0
 
-use smoltcp::socket::udp::{RecvError, SendError};
+use aster_bigtcp::{
+    errors::udp::{RecvError, SendError},
+    socket::RawUdpSocket,
+    wire::IpEndpoint,
+};
 
-use super::IpEndpoint;
 use crate::{
     events::IoEvents,
-    net::{
-        iface::{AnyBoundSocket, RawUdpSocket},
-        socket::util::send_recv_flags::SendRecvFlags,
-    },
+    net::{iface::AnyBoundSocket, socket::util::send_recv_flags::SendRecvFlags},
     prelude::*,
     process::signal::Pollee,
 };
diff --git a/kernel/src/net/socket/ip/datagram/mod.rs b/kernel/src/net/socket/ip/datagram/mod.rs
index 6420919ac..0c97d9381 100644
--- a/kernel/src/net/socket/ip/datagram/mod.rs
+++ b/kernel/src/net/socket/ip/datagram/mod.rs
@@ -2,10 +2,11 @@
 
 use core::sync::atomic::{AtomicBool, Ordering};
 
+use aster_bigtcp::{socket::SocketEventObserver, wire::IpEndpoint};
 use takeable::Takeable;
 
 use self::{bound::BoundDatagram, unbound::UnboundDatagram};
-use super::{common::get_ephemeral_endpoint, IpEndpoint, UNSPECIFIED_LOCAL_ENDPOINT};
+use super::{common::get_ephemeral_endpoint, UNSPECIFIED_LOCAL_ENDPOINT};
 use crate::{
     events::{IoEvents, Observer},
     fs::{file_handle::FileLike, utils::StatusFlags},
@@ -393,8 +394,8 @@ impl Socket for DatagramSocket {
     }
 }
 
-impl Observer<()> for DatagramSocket {
-    fn on_events(&self, _events: &()) {
+impl SocketEventObserver for DatagramSocket {
+    fn on_events(&self) {
         self.update_io_events();
     }
 }
diff --git a/kernel/src/net/socket/ip/datagram/unbound.rs b/kernel/src/net/socket/ip/datagram/unbound.rs
index 7d363eddc..365233f36 100644
--- a/kernel/src/net/socket/ip/datagram/unbound.rs
+++ b/kernel/src/net/socket/ip/datagram/unbound.rs
@@ -2,15 +2,14 @@
 
 use alloc::sync::Weak;
 
-use super::{bound::BoundDatagram, IpEndpoint};
+use aster_bigtcp::{
+    socket::{AnyUnboundSocket, RawUdpSocket, SocketEventObserver},
+    wire::IpEndpoint,
+};
+
+use super::bound::BoundDatagram;
 use crate::{
-    events::{IoEvents, Observer},
-    net::{
-        iface::{AnyUnboundSocket, RawUdpSocket},
-        socket::ip::common::bind_socket,
-    },
-    prelude::*,
-    process::signal::Pollee,
+    events::IoEvents, net::socket::ip::common::bind_socket, prelude::*, process::signal::Pollee,
 };
 
 pub struct UnboundDatagram {
@@ -18,7 +17,7 @@ pub struct UnboundDatagram {
 }
 
 impl UnboundDatagram {
-    pub fn new(observer: Weak<dyn Observer<()>>) -> Self {
+    pub fn new(observer: Weak<dyn SocketEventObserver>) -> Self {
         Self {
             unbound_socket: Box::new(AnyUnboundSocket::new_udp(observer)),
         }
diff --git a/kernel/src/net/socket/ip/mod.rs b/kernel/src/net/socket/ip/mod.rs
index d6c0cb93a..313260606 100644
--- a/kernel/src/net/socket/ip/mod.rs
+++ b/kernel/src/net/socket/ip/mod.rs
@@ -5,14 +5,6 @@ mod common;
 mod datagram;
 pub mod stream;
 
-pub use addr::{IpAddress, IpEndpoint, Ipv4Address, PortNum};
+use addr::UNSPECIFIED_LOCAL_ENDPOINT;
 pub use datagram::DatagramSocket;
 pub use stream::StreamSocket;
-
-/// A local endpoint, which indicates that the local endpoint is unspecified.
-///
-/// According to the Linux man pages and the Linux implementation, `getsockname()` will _not_ fail
-/// even if the socket is unbound. Instead, it will return an unspecified socket address. This
-/// unspecified endpoint helps with that.
-const UNSPECIFIED_LOCAL_ENDPOINT: IpEndpoint =
-    IpEndpoint::new(IpAddress::Ipv4(Ipv4Address::UNSPECIFIED), 0);
diff --git a/kernel/src/net/socket/ip/stream/connected.rs b/kernel/src/net/socket/ip/stream/connected.rs
index d5e337c9d..e0f4fd90b 100644
--- a/kernel/src/net/socket/ip/stream/connected.rs
+++ b/kernel/src/net/socket/ip/stream/connected.rs
@@ -2,13 +2,16 @@
 
 use alloc::sync::Weak;
 
-use smoltcp::socket::tcp::{RecvError, SendError};
+use aster_bigtcp::{
+    errors::tcp::{RecvError, SendError},
+    socket::{RawTcpSocket, SocketEventObserver},
+    wire::IpEndpoint,
+};
 
-use super::IpEndpoint;
 use crate::{
-    events::{IoEvents, Observer},
+    events::IoEvents,
     net::{
-        iface::{AnyBoundSocket, RawTcpSocket},
+        iface::AnyBoundSocket,
         socket::util::{send_recv_flags::SendRecvFlags, shutdown_cmd::SockShutdownCmd},
     },
     prelude::*,
@@ -122,7 +125,7 @@ impl ConnectedStream {
         });
     }
 
-    pub(super) fn set_observer(&self, observer: Weak<dyn Observer<()>>) {
+    pub(super) fn set_observer(&self, observer: Weak<dyn SocketEventObserver>) {
         self.bound_socket.set_observer(observer)
     }
 }
diff --git a/kernel/src/net/socket/ip/stream/connecting.rs b/kernel/src/net/socket/ip/stream/connecting.rs
index 8833b1560..413e1cb9c 100644
--- a/kernel/src/net/socket/ip/stream/connecting.rs
+++ b/kernel/src/net/socket/ip/stream/connecting.rs
@@ -1,11 +1,9 @@
 // SPDX-License-Identifier: MPL-2.0
 
-use super::{connected::ConnectedStream, init::InitStream, IpEndpoint};
-use crate::{
-    net::iface::{AnyBoundSocket, RawTcpSocket},
-    prelude::*,
-    process::signal::Pollee,
-};
+use aster_bigtcp::{socket::RawTcpSocket, wire::IpEndpoint};
+
+use super::{connected::ConnectedStream, init::InitStream};
+use crate::{net::iface::AnyBoundSocket, prelude::*, process::signal::Pollee};
 
 pub struct ConnectingStream {
     bound_socket: AnyBoundSocket,
@@ -29,9 +27,21 @@ impl ConnectingStream {
         bound_socket: AnyBoundSocket,
         remote_endpoint: IpEndpoint,
     ) -> core::result::Result<Self, (Error, AnyBoundSocket)> {
-        if let Err(err) = bound_socket.do_connect(remote_endpoint) {
-            return Err((err, bound_socket));
+        // The only reason this method might fail is because we're trying to connect to an
+        // unspecified address (i.e. 0.0.0.0). We currently have no support for binding to,
+        // listening on, or connecting to the unspecified address.
+        //
+        // We assume the remote will just refuse to connect, so we return `ECONNREFUSED`.
+        if bound_socket.do_connect(remote_endpoint).is_err() {
+            return Err((
+                Error::with_message(
+                    Errno::ECONNREFUSED,
+                    "connecting to an unspecified address is not supported",
+                ),
+                bound_socket,
+            ));
         }
+
         Ok(Self {
             bound_socket,
             remote_endpoint,
diff --git a/kernel/src/net/socket/ip/stream/init.rs b/kernel/src/net/socket/ip/stream/init.rs
index 8f04de7c2..0f312793d 100644
--- a/kernel/src/net/socket/ip/stream/init.rs
+++ b/kernel/src/net/socket/ip/stream/init.rs
@@ -2,11 +2,16 @@
 
 use alloc::sync::Weak;
 
-use super::{connecting::ConnectingStream, listen::ListenStream, IpEndpoint};
+use aster_bigtcp::{
+    socket::{AnyUnboundSocket, SocketEventObserver},
+    wire::IpEndpoint,
+};
+
+use super::{connecting::ConnectingStream, listen::ListenStream};
 use crate::{
-    events::{IoEvents, Observer},
+    events::IoEvents,
     net::{
-        iface::{AnyBoundSocket, AnyUnboundSocket},
+        iface::AnyBoundSocket,
         socket::ip::common::{bind_socket, get_ephemeral_endpoint},
     },
     prelude::*,
@@ -19,7 +24,7 @@ pub enum InitStream {
 }
 
 impl InitStream {
-    pub fn new(observer: Weak<dyn Observer<()>>) -> Self {
+    pub fn new(observer: Weak<dyn SocketEventObserver>) -> Self {
         InitStream::Unbound(Box::new(AnyUnboundSocket::new_tcp(observer)))
     }
 
diff --git a/kernel/src/net/socket/ip/stream/listen.rs b/kernel/src/net/socket/ip/stream/listen.rs
index 9e576e1f2..45b6f7cfa 100644
--- a/kernel/src/net/socket/ip/stream/listen.rs
+++ b/kernel/src/net/socket/ip/stream/listen.rs
@@ -1,15 +1,15 @@
 // SPDX-License-Identifier: MPL-2.0
 
-use smoltcp::socket::tcp::ListenError;
-
-use super::{connected::ConnectedStream, IpEndpoint};
-use crate::{
-    events::IoEvents,
-    net::iface::{AnyBoundSocket, AnyUnboundSocket, BindPortConfig, RawTcpSocket},
-    prelude::*,
-    process::signal::Pollee,
+use aster_bigtcp::{
+    errors::tcp::ListenError,
+    iface::BindPortConfig,
+    socket::{AnyUnboundSocket, RawTcpSocket},
+    wire::IpEndpoint,
 };
 
+use super::connected::ConnectedStream;
+use crate::{events::IoEvents, net::iface::AnyBoundSocket, prelude::*, process::signal::Pollee};
+
 pub struct ListenStream {
     backlog: usize,
     /// A bound socket held to ensure the TCP port cannot be released
@@ -117,7 +117,7 @@ impl BacklogSocket {
         let unbound_socket = Box::new(AnyUnboundSocket::new_tcp(Weak::<()>::new()));
         let bound_socket = {
             let iface = bound_socket.iface();
-            let bind_port_config = BindPortConfig::new(local_endpoint.port, true)?;
+            let bind_port_config = BindPortConfig::new(local_endpoint.port, true);
             iface
                 .bind_socket(unbound_socket, bind_port_config)
                 .map_err(|(err, _)| err)?
diff --git a/kernel/src/net/socket/ip/stream/mod.rs b/kernel/src/net/socket/ip/stream/mod.rs
index bedd310bb..921233f61 100644
--- a/kernel/src/net/socket/ip/stream/mod.rs
+++ b/kernel/src/net/socket/ip/stream/mod.rs
@@ -2,12 +2,12 @@
 
 use core::sync::atomic::{AtomicBool, Ordering};
 
+use aster_bigtcp::{socket::SocketEventObserver, wire::IpEndpoint};
 use connected::ConnectedStream;
 use connecting::ConnectingStream;
 use init::InitStream;
 use listen::ListenStream;
 use options::{Congestion, MaxSegment, NoDelay, WindowClamp};
-use smoltcp::wire::IpEndpoint;
 use takeable::Takeable;
 use util::{TcpOptionSet, DEFAULT_MAXSEG};
 
@@ -647,8 +647,8 @@ impl Socket for StreamSocket {
     }
 }
 
-impl Observer<()> for StreamSocket {
-    fn on_events(&self, _events: &()) {
+impl SocketEventObserver for StreamSocket {
+    fn on_events(&self) {
         let conn_ready = self.update_io_events();
 
         if conn_ready {
diff --git a/kernel/src/net/socket/util/options.rs b/kernel/src/net/socket/util/options.rs
index f7f8ddd52..be3a0541f 100644
--- a/kernel/src/net/socket/util/options.rs
+++ b/kernel/src/net/socket/util/options.rs
@@ -2,13 +2,14 @@
 
 use core::time::Duration;
 
+use aster_bigtcp::socket::{
+    TCP_RECV_BUF_LEN, TCP_SEND_BUF_LEN, UDP_RECV_PAYLOAD_LEN, UDP_SEND_PAYLOAD_LEN,
+};
+
 use crate::{
     match_sock_option_mut, match_sock_option_ref,
-    net::{
-        iface::{TCP_RECV_BUF_LEN, TCP_SEND_BUF_LEN, UDP_RECV_PAYLOAD_LEN, UDP_SEND_PAYLOAD_LEN},
-        socket::options::{
-            Error as SocketError, Linger, RecvBuf, ReuseAddr, ReusePort, SendBuf, SocketOption,
-        },
+    net::socket::options::{
+        Error as SocketError, Linger, RecvBuf, ReuseAddr, ReusePort, SendBuf, SocketOption,
     },
     prelude::*,
 };
diff --git a/kernel/src/net/socket/util/socket_addr.rs b/kernel/src/net/socket/util/socket_addr.rs
index 445fd6b27..3c1b994f3 100644
--- a/kernel/src/net/socket/util/socket_addr.rs
+++ b/kernel/src/net/socket/util/socket_addr.rs
@@ -1,11 +1,9 @@
 // SPDX-License-Identifier: MPL-2.0
 
+use aster_bigtcp::wire::{Ipv4Address, PortNum};
+
 use crate::{
-    net::socket::{
-        ip::{Ipv4Address, PortNum},
-        unix::UnixSocketAddr,
-        vsock::addr::VsockSocketAddr,
-    },
+    net::socket::{unix::UnixSocketAddr, vsock::addr::VsockSocketAddr},
     prelude::*,
 };
 
diff --git a/kernel/src/util/net/addr/ip.rs b/kernel/src/util/net/addr/ip.rs
index c43dc83be..873cef184 100644
--- a/kernel/src/util/net/addr/ip.rs
+++ b/kernel/src/util/net/addr/ip.rs
@@ -1,10 +1,9 @@
 // SPDX-License-Identifier: MPL-2.0
 
+use aster_bigtcp::wire::{Ipv4Address, PortNum};
+
 use super::family::CSocketAddrFamily;
-use crate::{
-    net::socket::ip::{Ipv4Address, PortNum},
-    prelude::*,
-};
+use crate::prelude::*;
 
 /// IPv4 socket address.
 ///