diff --git a/realm_io/src/lib.rs b/realm_io/src/lib.rs
index b186adb8..20c5c111 100644
--- a/realm_io/src/lib.rs
+++ b/realm_io/src/lib.rs
@@ -57,9 +57,7 @@ mod linux;
 #[cfg(any(target_os = "linux", doc))]
 #[cfg_attr(doc, doc(cfg(target_os = "linux")))]
 pub use linux::{
-    AsyncRawIO,
-    mmsg::{Packet, PacketMut, PacketStore, SockAddrStore, STORE_LEN},
-    mmsg::{send_mul_pkts, recv_mul_pkts},
+    AsyncRawIO, mmsg,
     zero_copy::{Pipe, bidi_zero_copy, pipe_size, set_pipe_size},
 };
 
diff --git a/realm_io/src/linux/mmsg.rs b/realm_io/src/linux/mmsg.rs
index f66839f5..9073d002 100644
--- a/realm_io/src/linux/mmsg.rs
+++ b/realm_io/src/linux/mmsg.rs
@@ -1,85 +1,24 @@
+//! Mmsg impl.
+
 use std::task::{Poll, Context};
 use std::io::Result;
-use std::io::{IoSlice, IoSliceMut};
 use std::os::unix::io::RawFd;
 
 use crate::AsyncRawIO;
 
-#[derive(Debug, Clone, Copy)]
-pub struct Packet<'a, 'buf> {
-    addr: &'a SockAddrStore,
-    iovec: IoSlice<'buf>,
-}
-
-#[derive(Debug)]
-pub struct PacketMut<'a, 'buf> {
-    addr: &'a mut SockAddrStore,
-    iovec: IoSliceMut<'buf>,
-}
-
-impl<'a, 'buf> Packet<'a, 'buf> {
-    pub fn new(addr: &'a SockAddrStore, data: &'buf [u8]) -> Self {
-        Self {
-            addr,
-            iovec: IoSlice::new(data),
-        }
-    }
-
-    pub fn into_store<'pkt>(&'pkt self) -> PacketStore<'a, 'buf, 'pkt> {
-        use std::marker::PhantomData;
-        let Packet { addr, iovec } = self;
-        PacketStore {
-            msg: libc::msghdr {
-                msg_name: addr.0.as_ptr() as *mut _,
-                msg_namelen: addr.0.len(),
-                msg_iov: iovec as *const IoSlice as *mut _,
-                msg_iovlen: 1,
-                msg_control: std::ptr::null_mut(),
-                msg_controllen: 0,
-                msg_flags: 0,
-            },
-            addr: PhantomData,
-            iovec: PhantomData,
-            packet: PhantomData,
-        }
-    }
-}
-
-impl<'a, 'buf> PacketMut<'a, 'buf> {
-    pub fn new(addr: &'a mut SockAddrStore, data: &'buf mut [u8]) -> Self {
-        Self {
-            addr,
-            iovec: IoSliceMut::new(data),
-        }
-    }
-
-    pub fn into_store<'pkt>(&'pkt mut self) -> PacketStore<'a, 'buf, 'pkt> {
-        use std::marker::PhantomData;
-        let PacketMut { addr, iovec } = self;
-        PacketStore {
-            msg: libc::msghdr {
-                msg_name: addr.0.as_ptr() as *mut _,
-                msg_namelen: addr.0.len(),
-                msg_iov: iovec as *mut IoSliceMut as *mut _,
-                msg_iovlen: 1,
-                msg_control: std::ptr::null_mut(),
-                msg_controllen: 0,
-                msg_flags: 0,
-            },
-            addr: PhantomData,
-            iovec: PhantomData,
-            packet: PhantomData,
-        }
-    }
-}
+pub use store::{PacketStore, Const, Mutable};
+pub use store::{PacketRef, PacketMutRef};
+pub use store::{SockAddrStore, SOCK_STORE_LEN};
+pub type Packet<'a, 'buf, 'iov, 'ctrl> = PacketStore<'a, 'buf, 'iov, 'ctrl, Const>;
+pub type PacketMut<'a, 'buf, 'iov, 'ctrl> = PacketStore<'a, 'buf, 'iov, 'ctrl, Mutable>;
 
 #[inline]
-fn sendmpkts(fd: RawFd, pkts: &[PacketStore]) -> i32 {
+fn sendmpkts<M>(fd: RawFd, pkts: &mut [PacketStore<'_, '_, '_, '_, M>]) -> i32 {
     unsafe { libc::sendmmsg(fd, pkts.as_ptr() as *mut _, pkts.len() as u32, 0) }
 }
 
 #[inline]
-fn recvmpkts(fd: RawFd, pkts: &mut [PacketStore]) -> i32 {
+fn recvmpkts(fd: RawFd, pkts: &mut [PacketMut]) -> i32 {
     unsafe {
         libc::recvmmsg(
             fd,
@@ -91,77 +30,252 @@ fn recvmpkts(fd: RawFd, pkts: &mut [PacketStore]) -> i32 {
     }
 }
 
-fn poll_sendmpkts<S>(stream: &mut S, cx: &mut Context<'_>, pkts: &[PacketStore]) -> Poll<Result<usize>>
+fn poll_sendmpkts<S, M>(
+    stream: &mut S,
+    cx: &mut Context<'_>,
+    pkts: &mut [PacketStore<'_, '_, '_, '_, M>],
+) -> Poll<Result<usize>>
 where
     S: AsyncRawIO + Unpin,
 {
-    stream.poll_read_raw(cx, || sendmpkts(stream.as_raw_fd(), pkts) as isize)
+    stream.poll_write_raw(cx, || sendmpkts(stream.as_raw_fd(), pkts) as isize)
 }
 
-fn poll_recvmpkts<S>(stream: &mut S, cx: &mut Context<'_>, pkts: &mut [PacketStore]) -> Poll<Result<usize>>
+fn poll_recvmpkts<S>(stream: &mut S, cx: &mut Context<'_>, pkts: &mut [PacketMut]) -> Poll<Result<usize>>
 where
     S: AsyncRawIO + Unpin,
 {
-    stream.poll_write_raw(cx, || recvmpkts(stream.as_raw_fd(), pkts) as isize)
+    stream.poll_read_raw(cx, || recvmpkts(stream.as_raw_fd(), pkts) as isize)
 }
 
-pub async fn send_mul_pkts<S>(stream: &mut S, pkts: &[PacketStore<'_, '_, '_>]) -> Result<usize>
+/// Send multiple packets.
+pub async fn send_mul_pkts<S>(stream: &mut S, pkts: &mut [Packet<'_, '_, '_, '_>]) -> Result<usize>
 where
     S: AsyncRawIO + Unpin,
 {
     std::future::poll_fn(move |cx| poll_sendmpkts(stream, cx, pkts)).await
 }
 
-pub async fn recv_mul_pkts<S>(stream: &mut S, pkts: &mut [PacketStore<'_, '_, '_>]) -> Result<usize>
+/// Recv multiple packets.
+pub async fn recv_mul_pkts<S>(stream: &mut S, pkts: &mut [PacketMut<'_, '_, '_, '_>]) -> Result<usize>
 where
     S: AsyncRawIO + Unpin,
 {
     std::future::poll_fn(move |cx| poll_recvmpkts(stream, cx, pkts)).await
 }
 
-pub use store::{PacketStore, SockAddrStore, STORE_LEN};
 mod store {
-    use std::mem;
+    use std::{mem, ptr, slice};
     use std::marker::PhantomData;
+    use std::io::{IoSlice, IoSliceMut};
     use std::net::SocketAddr;
     use socket2::SockAddr;
-    use libc::{msghdr, sockaddr_storage, socklen_t};
+    use libc::{msghdr, mmsghdr};
+    use libc::{sockaddr_storage, socklen_t};
+
+    /// Marker.
+    pub struct Const {}
+
+    /// Marker.
+    pub struct Mutable {}
 
-    /// Represent [`libc::msghdr`].
+    /// Represent [`libc::mmsghdr`].
     #[derive(Clone, Copy)]
     #[repr(transparent)]
-    pub struct PacketStore<'a, 'buf, 'pkt> {
-        pub(crate) msg: msghdr,
-        pub(crate) addr: PhantomData<&'a ()>,
-        pub(crate) iovec: PhantomData<&'buf ()>,
-        pub(crate) packet: PhantomData<&'pkt ()>,
+    pub struct PacketStore<'a, 'buf, 'iov, 'ctrl, M> {
+        pub(crate) store: mmsghdr,
+        _type: PhantomData<M>,
+        _lifetime: PhantomData<(&'a (), &'buf (), &'iov (), &'ctrl ())>,
+    }
+
+    /// Constant field accessor for [`PacketStore`].
+    pub struct PacketRef<'a, 'buf, 'iov, 'ctrl, 'this> {
+        addr: &'a SockAddrStore,
+        iovec: &'iov [IoSlice<'buf>],
+        control: &'ctrl [u8],
+        flags: i32,
+        nbytes: u32,
+        _lifetime: PhantomData<&'this ()>,
+    }
+
+    /// Mutable field accessor for [`PacketStore`].
+    pub struct PacketMutRef<'a, 'buf, 'iov, 'ctrl, 'this> {
+        addr: &'a mut SockAddrStore,
+        iovec: &'iov mut [IoSlice<'buf>],
+        control: &'ctrl mut [u8],
+        flags: i32,
+        nbytes: u32,
+        _lifetime: PhantomData<&'this ()>,
+    }
+
+    #[rustfmt::skip]
+    macro_rules! access_fn {
+        (!ref, $field: ident, $type: ty) => {
+            pub fn $field(&self) -> $type { &self.$field }
+        };
+        (!mut, $field: ident, $type: ty) => {
+            pub fn $field(&mut self) -> $type { &mut self.$field }
+        };
+        (!val, $field: ident, $type: ty) => {
+            pub fn $field(&self) -> $type { self.$field }
+        };
+    }
+
+    impl<'a, 'buf, 'iov, 'ctrl, 'this> PacketRef<'a, 'buf, 'iov, 'ctrl, 'this> {
+        access_fn!(!ref, addr, &&'a SockAddrStore);
+        access_fn!(!ref, iovec, &&'iov [IoSlice<'buf>]);
+        access_fn!(!ref, control, &&'ctrl [u8]);
+        access_fn!(!val, flags, i32);
+        access_fn!(!val, nbytes, u32);
+    }
+
+    impl<'a, 'buf, 'iov, 'ctrl, 'this> PacketMutRef<'a, 'buf, 'iov, 'ctrl, 'this> {
+        access_fn!(!mut, addr, &mut &'a mut SockAddrStore);
+        access_fn!(!mut, iovec, &mut &'iov mut [IoSlice<'buf>]);
+        access_fn!(!mut, control, &mut &'ctrl mut [u8]);
+        access_fn!(!val, flags, i32);
+        access_fn!(!val, nbytes, u32);
+    }
+
+    impl<'a, 'buf, 'iov, 'ctrl, M> PacketStore<'a, 'buf, 'iov, 'ctrl, M> {
+        /// New zeroed storage.
+        pub const fn new() -> Self {
+            Self {
+                store: unsafe { mem::zeroed::<mmsghdr>() },
+                _type: PhantomData,
+                _lifetime: PhantomData,
+            }
+        }
+
+        /// Get constant accessor.
+        #[rustfmt::skip]
+        pub fn get_ref<'this>(&'this self) -> PacketRef<'this, 'a, 'buf, 'iov, 'ctrl> {
+            let msghdr {
+                msg_name, msg_namelen,
+                msg_iov, msg_iovlen,
+                msg_control, msg_controllen, msg_flags,
+            } = self.store.msg_hdr;
+            let msg_len = self.store.msg_len;
+            unsafe { PacketRef {
+                addr: &*msg_name.cast(), // todo!
+                iovec: slice::from_raw_parts(msg_iov as *const _, msg_iovlen),
+                control: slice::from_raw_parts(msg_control as *const _, msg_controllen),
+                flags: msg_flags,
+                nbytes: msg_len,
+                _lifetime: PhantomData,
+            }}
+        }
+    }
+
+    impl<'a, 'buf, 'iov, 'ctrl, M> Default for PacketStore<'a, 'buf, 'iov, 'ctrl, M> {
+        fn default() -> Self {
+            Self::new()
+        }
+    }
+
+    impl<'a, 'buf, 'iov, 'ctrl> PacketStore<'a, 'buf, 'iov, 'ctrl, Const> {
+        /// Set target address.
+        pub const fn with_addr(mut self, addr: &'a SockAddrStore) -> Self {
+            self.store.msg_hdr.msg_name = addr.0.as_ptr() as *mut _;
+            self.store.msg_hdr.msg_namelen = addr.0.len();
+            self
+        }
+
+        /// Set data to send.
+        pub const fn with_iovec(mut self, iov: &'iov [IoSlice<'buf>]) -> Self {
+            self.store.msg_hdr.msg_iov = ptr::from_ref(iov) as *mut _;
+            self.store.msg_hdr.msg_iovlen = iov.len();
+            self
+        }
+
+        /// Set control message to send.
+        pub const fn with_control(mut self, ctrl: &'ctrl [u8]) -> Self {
+            self.store.msg_hdr.msg_control = ptr::from_ref(ctrl) as *mut _;
+            self.store.msg_hdr.msg_controllen = ctrl.len();
+            self
+        }
+
+        /// Set sending flags.
+        pub const fn with_flags(mut self, flags: i32) -> Self {
+            self.store.msg_hdr.msg_flags = flags;
+            self
+        }
+    }
+
+    impl<'a, 'buf, 'iov, 'ctrl> PacketStore<'a, 'buf, 'iov, 'ctrl, Mutable> {
+        /// Set storage to accommodate peer address.
+        pub fn with_addr(mut self, addr: &'a mut SockAddrStore) -> Self {
+            self.store.msg_hdr.msg_name = addr.0.as_ptr() as *mut _;
+            self.store.msg_hdr.msg_namelen = addr.0.len();
+            self
+        }
+
+        /// Set storage to receive data.
+        pub fn with_iovec(mut self, iov: &'iov mut [IoSliceMut<'buf>]) -> Self {
+            self.store.msg_hdr.msg_iov = ptr::from_mut(iov) as *mut _;
+            self.store.msg_hdr.msg_iovlen = iov.len();
+            self
+        }
+
+        /// Set storage to receive control message.
+        pub fn with_control(mut self, ctrl: &'ctrl mut [u8]) -> Self {
+            self.store.msg_hdr.msg_control = ptr::from_mut(ctrl) as *mut _;
+            self.store.msg_hdr.msg_controllen = ctrl.len();
+            self
+        }
+
+        /// Get mutable accessor.
+        #[rustfmt::skip]
+        pub fn get_mut<'this>(&'this mut self) -> PacketMutRef<'this, 'a, 'buf, 'iov, 'ctrl> {
+            let msghdr {
+                msg_name, msg_namelen,
+                msg_iov, msg_iovlen,
+                msg_control, msg_controllen, msg_flags,
+            } = self.store.msg_hdr;
+            let msg_len = self.store.msg_len;
+            unsafe { PacketMutRef {
+                addr: &mut *msg_name.cast(), // todo!
+                iovec: slice::from_raw_parts_mut(msg_iov as *mut _, msg_iovlen),
+                control: slice::from_raw_parts_mut(msg_control as *mut _, msg_controllen),
+                flags: msg_flags,
+                nbytes: msg_len,
+                _lifetime: PhantomData,
+            }}
+        }
     }
 
     /// Represent [`libc::sockaddr_storage`].
     #[derive(Debug, Clone, PartialEq, Eq, Hash)]
     pub struct SockAddrStore(pub(crate) SockAddr);
-    pub const STORE_LEN: socklen_t = mem::size_of::<sockaddr_storage>() as socklen_t;
-    mod addr {
-        use super::*;
-        impl SockAddrStore {
-            pub const fn new_zeroed() -> Self {
-                Self(unsafe { SockAddr::new(mem::zeroed::<sockaddr_storage>(), STORE_LEN) })
-            }
+
+    /// Size of [`libc::sockaddr_storage`].
+    pub const SOCK_STORE_LEN: socklen_t = mem::size_of::<sockaddr_storage>() as socklen_t;
+
+    impl SockAddrStore {
+        /// New zeroed storage.
+        pub const fn new() -> Self {
+            Self(unsafe { SockAddr::new(mem::zeroed::<sockaddr_storage>(), SOCK_STORE_LEN) })
         }
+    }
 
-        impl<T> From<T> for SockAddrStore
-        where
-            SockAddr: From<T>,
-        {
-            fn from(addr: T) -> Self {
-                Self(addr.into())
-            }
+    impl Default for SockAddrStore {
+        fn default() -> Self {
+            Self::new()
+        }
+    }
+
+    impl<T> From<T> for SockAddrStore
+    where
+        SockAddr: From<T>,
+    {
+        fn from(addr: T) -> Self {
+            Self(addr.into())
         }
+    }
 
-        impl From<SockAddrStore> for SocketAddr {
-            fn from(store: SockAddrStore) -> Self {
-                store.0.as_socket().unwrap()
-            }
+    impl From<SockAddrStore> for SocketAddr {
+        fn from(store: SockAddrStore) -> Self {
+            store.0.as_socket().unwrap()
         }
     }
 }
diff --git a/realm_io/src/linux/mod.rs b/realm_io/src/linux/mod.rs
index ef12dd61..c15fccf7 100644
--- a/realm_io/src/linux/mod.rs
+++ b/realm_io/src/linux/mod.rs
@@ -4,8 +4,8 @@ use std::os::unix::io::AsRawFd;
 
 use tokio::io::Interest;
 
-pub(crate) mod mmsg;
-pub(crate) mod zero_copy;
+pub mod mmsg;
+pub mod zero_copy;
 
 /// Type traits of Linux objects.
 pub trait AsyncRawIO: AsRawFd {