2 files changed, 253 insertions, 362 deletions

diff --git a/src/dhcp.rs b/src/dhcp.rs
index b53ee92..38cc8e4 100644
--- a/src/dhcp.rs
+++ b/src/dhcp.rs
@@ -1,11 +1,12 @@
 use std::{
-    io::{Result, Write},
+    io::{Cursor, Read as _, Result, Write},
     net::Ipv4Addr,
 };
 
 use crate::wire;
 
 const MAGIC_COOKIE: [u8; 4] = [0x63, 0x82, 0x53, 0x63];
+const FLAG_BROADCAST: u16 = 1 << 15;
 
 #[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum BootOp {
@@ -55,14 +56,17 @@ impl From<HardwareType> for u8 {
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum DhcpMessageType {
+    Offer,
     Ack,
 }
 
 impl DhcpMessageType {
+    pub const CODE_OFFER: u8 = 2;
     pub const CODE_ACK: u8 = 5;
 
     pub fn code(&self) -> u8 {
         match self {
+            DhcpMessageType::Offer => Self::CODE_OFFER,
             DhcpMessageType::Ack => Self::CODE_ACK,
         }
     }
@@ -78,7 +82,7 @@ pub enum DhcpOption {
     TftpServerName(String),
     TftpFileName(String),
     UserClassInformation(String),
-    ClientMachineIdentifier(String),
+    ClientMachineIdentifier(Vec<u8>),
     Unknown { code: u8, data: Vec<u8> },
 }
 
@@ -113,6 +117,7 @@ impl DhcpOption {
 pub struct DhcpPacket {
     pub op: BootOp,
     pub htype: HardwareType,
+    pub hops: u8,
     pub xid: u32,
     pub secs: u16,
     pub flags: u16,
@@ -122,9 +127,9 @@ pub struct DhcpPacket {
     pub giaddr: Ipv4Addr,
     pub chaddr: [u8; 16],
     // server host name
-    pub sname: Option<String>,
+    pub sname: String,
     // boot file name
-    pub file: Option<String>,
+    pub file: String,
     pub options: Vec<DhcpOption>,
 }
 
@@ -133,6 +138,7 @@ impl Default for DhcpPacket {
         Self {
             op: Default::default(),
             htype: Default::default(),
+            hops: Default::default(),
             xid: Default::default(),
             secs: Default::default(),
             flags: Default::default(),
@@ -148,11 +154,209 @@ impl Default for DhcpPacket {
     }
 }
 
+impl DhcpPacket {
+    pub fn new_boot(
+        xid: u32,
+        chaddr: [u8; 16],
+        client_uuid: Vec<u8>,
+        local_ip: Ipv4Addr,
+        local_hostname: String,
+        filename: String,
+    ) -> Self {
+        Self {
+            op: BootOp::Reply,
+            htype: HardwareType::Ethernet,
+            hops: Default::default(),
+            xid,
+            secs: Default::default(),
+            flags: FLAG_BROADCAST,
+            ciaddr: Ipv4Addr::UNSPECIFIED,
+            yiaddr: Ipv4Addr::UNSPECIFIED,
+            siaddr: local_ip,
+            giaddr: Ipv4Addr::UNSPECIFIED,
+            chaddr,
+            sname: Default::default(),
+            file: Default::default(),
+            options: vec![
+                DhcpOption::MessageType(DhcpMessageType::Offer),
+                DhcpOption::ServerIdentifier(local_ip),
+                DhcpOption::VendorClassIdentifier("PXEClient".to_string()),
+                DhcpOption::ClientMachineIdentifier(client_uuid),
+                DhcpOption::TftpServerName(local_hostname),
+                DhcpOption::TftpFileName(filename),
+            ],
+        }
+    }
+
+    pub fn new_boot_ack(
+        xid: u32,
+        chaddr: [u8; 16],
+        client_uuid: Vec<u8>,
+        local_ip: Ipv4Addr,
+        hostname: String,
+        filename: String,
+    ) -> Self {
+        Self {
+            op: BootOp::Reply,
+            htype: HardwareType::Ethernet,
+            hops: 0,
+            xid,
+            secs: 0,
+            flags: 0,
+            ciaddr: Ipv4Addr::UNSPECIFIED,
+            yiaddr: Ipv4Addr::UNSPECIFIED,
+            siaddr: Ipv4Addr::UNSPECIFIED,
+            giaddr: Ipv4Addr::UNSPECIFIED,
+            chaddr,
+            sname: Default::default(),
+            file: Default::default(),
+            options: vec![
+                DhcpOption::MessageType(DhcpMessageType::Ack),
+                DhcpOption::ServerIdentifier(local_ip),
+                DhcpOption::VendorClassIdentifier("PXEClient".to_string()),
+                DhcpOption::ClientMachineIdentifier(client_uuid),
+                DhcpOption::TftpServerName(hostname),
+                DhcpOption::TftpFileName(filename),
+            ],
+        }
+    }
+
+    pub fn write<W: Write>(&self, writer: W) -> Result<()> {
+        write_packet(writer, self)
+    }
+}
+
+fn read_u8(cursor: &mut Cursor<&[u8]>) -> Result<u8> {
+    let mut buf = [0u8; 1];
+    cursor.read_exact(&mut buf)?;
+    Ok(buf[0])
+}
+
+fn read_u16(cursor: &mut Cursor<&[u8]>) -> Result<u16> {
+    let mut buf = [0u8; 2];
+    cursor.read_exact(&mut buf)?;
+    Ok(u16::from_be_bytes(buf))
+}
+
+fn read_u32(cursor: &mut Cursor<&[u8]>) -> Result<u32> {
+    let mut buf = [0u8; 4];
+    cursor.read_exact(&mut buf)?;
+    Ok(u32::from_be_bytes(buf))
+}
+
+fn read_arr<const N: usize>(cursor: &mut Cursor<&[u8]>) -> Result<[u8; N]> {
+    let mut buf = [0u8; N];
+    cursor.read_exact(&mut buf)?;
+    Ok(buf)
+}
+
+fn read_len8_prefixed_vec(cursor: &mut Cursor<&[u8]>) -> Result<Vec<u8>> {
+    let len = read_u8(cursor)?;
+    let mut buf = vec![0u8; len as usize];
+    cursor.read_exact(&mut buf)?;
+    Ok(buf)
+}
+
+fn read_len8_prefixed_string(cursor: &mut Cursor<&[u8]>) -> Result<String> {
+    let buf = read_len8_prefixed_vec(cursor)?;
+    Ok(String::from_utf8(buf).unwrap())
+}
+
+fn read_ipv4(cursor: &mut Cursor<&[u8]>) -> Result<Ipv4Addr> {
+    Ok(Ipv4Addr::from_octets(read_arr(cursor)?))
+}
+
+fn read_op(cursor: &mut Cursor<&[u8]>) -> Result<BootOp> {
+    let v = read_u8(cursor)?;
+    match v {
+        BootOp::OP_REQUEST => Ok(BootOp::Request),
+        BootOp::OP_REPLY => Ok(BootOp::Reply),
+        _ => Err(std::io::Error::new(
+            std::io::ErrorKind::InvalidData,
+            "invalid boot op",
+        )),
+    }
+}
+
+fn read_htype(cursor: &mut Cursor<&[u8]>) -> Result<HardwareType> {
+    let ty = read_u8(cursor)?;
+    let len = read_u8(cursor)?;
+    match (ty, len) {
+        (HardwareType::TYPE_ETHER, HardwareType::LEN_ETHER) => Ok(HardwareType::Ethernet),
+        _ => Err(std::io::Error::new(
+            std::io::ErrorKind::InvalidData,
+            "invalid hardware type",
+        )),
+    }
+}
+
+fn read_option(cursor: &mut Cursor<&[u8]>) -> Result<DhcpOption> {
+    let code = read_u8(cursor)?;
+    Ok(match code {
+        DhcpOption::CODE_PAD => DhcpOption::Pad,
+        DhcpOption::CODE_END => DhcpOption::End,
+        DhcpOption::CODE_VENDOR_CLASS_IDENTIFIER => {
+            DhcpOption::VendorClassIdentifier(read_len8_prefixed_string(cursor)?)
+        }
+        DhcpOption::CODE_USER_CLASS_INFORMATION => {
+            DhcpOption::UserClassInformation(read_len8_prefixed_string(cursor)?)
+        }
+        _ => {
+            let len = read_u8(cursor)?;
+            let mut data = vec![0u8; usize::from(len)];
+            cursor.read_exact(&mut data)?;
+            DhcpOption::Unknown { code, data }
+        }
+    })
+}
+
+fn read_sname(cursor: &mut Cursor<&[u8]>) -> Result<String> {
+    let arr = read_arr::<64>(cursor)?;
+    let sname = std::str::from_utf8(&arr).unwrap();
+    Ok(sname.to_string())
+}
+
+fn read_filename(cursor: &mut Cursor<&[u8]>) -> Result<String> {
+    let arr = read_arr::<128>(cursor)?;
+    let filename = std::str::from_utf8(&arr).unwrap();
+    Ok(filename.to_string())
+}
+
+pub fn parse_packet(buf: &[u8]) -> Result<DhcpPacket> {
+    let mut cursor = Cursor::new(buf);
+    let mut packet = DhcpPacket {
+        op: read_op(&mut cursor)?,
+        htype: read_htype(&mut cursor)?,
+        hops: read_u8(&mut cursor)?,
+        xid: read_u32(&mut cursor)?,
+        secs: read_u16(&mut cursor)?,
+        flags: read_u16(&mut cursor)?,
+        ciaddr: read_ipv4(&mut cursor)?,
+        yiaddr: read_ipv4(&mut cursor)?,
+        siaddr: read_ipv4(&mut cursor)?,
+        giaddr: read_ipv4(&mut cursor)?,
+        chaddr: read_arr(&mut cursor)?,
+        sname: read_sname(&mut cursor)?,
+        file: read_filename(&mut cursor)?,
+        options: Default::default(),
+    };
+
+    let magic = read_arr::<4>(&mut cursor)?;
+    assert_eq!(magic, MAGIC_COOKIE);
+
+    while cursor.position() < buf.len() as u64 {
+        let option = read_option(&mut cursor)?;
+        packet.options.push(option);
+    }
+
+    Ok(packet)
+}
+
 pub fn write_packet<W: Write>(mut writer: W, packet: &DhcpPacket) -> Result<()> {
     wire::write_u8(&mut writer, u8::from(packet.op))?;
     wire::write_u8(&mut writer, u8::from(packet.htype))?;
     wire::write_u8(&mut writer, packet.htype.hardware_len())?;
-    wire::write_u8(&mut writer, 0)?; // hops
+    wire::write_u8(&mut writer, packet.hops)?;
     wire::write_u32(&mut writer, packet.xid)?;
     wire::write_u16(&mut writer, packet.secs)?;
     wire::write_u16(&mut writer, packet.flags)?;
@@ -161,14 +365,10 @@ pub fn write_packet<W: Write>(mut writer: W, packet: &DhcpPacket) -> Result<()>
     wire::write_ipv4(&mut writer, packet.siaddr)?;
     wire::write_ipv4(&mut writer, packet.giaddr)?;
     wire::write(&mut writer, &packet.chaddr)?;
-    match &packet.sname {
-        Some(name) => wire::write_null_terminated_string(&mut writer, &name)?,
-        None => wire::write_null_terminated_string(&mut writer, "")?,
-    };
-    match &packet.file {
-        Some(name) => wire::write_null_terminated_string(&mut writer, &name)?,
-        None => wire::write_null_terminated_string(&mut writer, "")?,
-    };
+    //wire::write_null_terminated_string(&mut writer, &packet.sname)?;
+    //wire::write_null_terminated_string(&mut writer, &packet.file)?;
+    wire::write(&mut writer, &vec![0u8; 64])?;
+    wire::write(&mut writer, &vec![0u8; 128])?;
     wire::write(&mut writer, &MAGIC_COOKIE)?;
     for option in &packet.options {
         write_option(&mut writer, option)?;
@@ -198,7 +398,7 @@ pub fn write_option<W: Write>(mut writer: W, option: &DhcpOption) -> Result<()>
             write_option_len_prefixed_string(&mut writer, &user_class)?
         }
         DhcpOption::ClientMachineIdentifier(identifier) => {
-            write_option_len_prefixed_string(&mut writer, &identifier)?
+            write_option_len_prefixed_buf(&mut writer, &identifier)?
         }
         DhcpOption::Unknown { data, .. } => {
             wire::write_u8(&mut writer, u8::try_from(data.len()).unwrap())?;
@@ -212,3 +412,8 @@ fn write_option_len_prefixed_string<W: Write>(mut writer: W, s: &str) -> Result<
     wire::write_u8(&mut writer, u8::try_from(s.len()).unwrap())?;
     wire::write(&mut writer, s.as_bytes())
 }
+
+fn write_option_len_prefixed_buf<W: Write>(mut writer: W, s: &[u8]) -> Result<()> {
+    wire::write_u8(&mut writer, u8::try_from(s.len()).unwrap())?;
+    wire::write(&mut writer, s)
+}
diff --git a/src/main.rs b/src/main.rs
index 321b5ea..51bbd77 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,351 +3,17 @@ pub mod dhcp;
 pub mod tftp;
 pub mod wire;
 
-use std::io::{BufRead, Cursor, Read, Result, Write};
-use std::net::{Ipv4Addr, SocketAddr, SocketAddrV4, UdpSocket};
+use std::{
+    io::Result,
+    net::{Ipv4Addr, SocketAddr, SocketAddrV4, UdpSocket},
+};
 
 use ipnet::Ipv4Net;
 
-const FLAG_BROADCAST: u16 = 1 << 15;
+use crate::dhcp::{DhcpOption, DhcpPacket};
 
-const OPTION_CODE_PAD: u8 = 0;
-const OPTION_CODE_END: u8 = 255;
-const OPTION_CODE_VENDOR_CLASS_IDENTIFIER: u8 = 60;
-const OPTION_CODE_USER_CLASS_INFORMATION: u8 = 77;
-
-const MAGIC_COOKIE: [u8; 4] = [0x63, 0x82, 0x53, 0x63];
-
-//const BOOT_FILE_NAME: &[u8] = b"pxelinux.0";
-//const BOOT_FILE_NAME: &[u8] = b"debian-installer/amd64/bootnetx64.efi";
-const BOOT_FILE_NAME: &[u8] = b"ipxe.efi";
-const BOOT_FILE_NAME_IPXE: &[u8] = b"test.ipxe";
-
-const LOCAL_IPV4: Ipv4Addr = Ipv4Addr::new(192, 168, 1, 100);
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-enum BootOp {
-    Request,
-    Reply,
-}
-
-impl BootOp {
-    pub const OP_REQUEST: u8 = 1;
-    pub const OP_REPLY: u8 = 2;
-}
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-enum HardwareType {
-    Ethernet,
-}
-
-impl HardwareType {
-    pub const TYPE_ETHER: u8 = 1;
-    pub const LEN_ETHER: u8 = 6;
-}
-
-#[derive(Debug, Clone)]
-enum DhcpOption {
-    Pad,
-    End,
-    VendorClassIdentifier(String),
-    UserClassInformation(String),
-    Unknown { code: u8, data: Vec<u8> },
-}
-
-#[derive(Debug)]
-struct DhcpPacket {
-    op: BootOp,
-    htype: HardwareType,
-    hlen: u8,
-    hops: u8, // should be zero
-    xid: u32,
-    secs: u16,
-    flags: u16,
-    ciaddr: Ipv4Addr,
-    yiaddr: Ipv4Addr,
-    siaddr: Ipv4Addr,
-    giaddr: Ipv4Addr,
-    chaddr: [u8; 16],
-    sname: [u8; 64],
-    file: [u8; 128],
-    options: Vec<DhcpOption>,
-}
-
-fn read_u8(cursor: &mut Cursor<&[u8]>) -> Result<u8> {
-    let mut buf = [0u8; 1];
-    cursor.read_exact(&mut buf)?;
-    Ok(buf[0])
-}
-
-fn read_u16(cursor: &mut Cursor<&[u8]>) -> Result<u16> {
-    let mut buf = [0u8; 2];
-    cursor.read_exact(&mut buf)?;
-    Ok(u16::from_be_bytes(buf))
-}
-
-fn read_u32(cursor: &mut Cursor<&[u8]>) -> Result<u32> {
-    let mut buf = [0u8; 4];
-    cursor.read_exact(&mut buf)?;
-    Ok(u32::from_be_bytes(buf))
-}
-
-fn read_arr<const N: usize>(cursor: &mut Cursor<&[u8]>) -> Result<[u8; N]> {
-    let mut buf = [0u8; N];
-    cursor.read_exact(&mut buf)?;
-    Ok(buf)
-}
-
-fn read_null_terminated_vec(cursor: &mut Cursor<&[u8]>) -> Result<Vec<u8>> {
-    let mut buf = Vec::default();
-    cursor.read_until(0, &mut buf)?;
-    buf.pop();
-    Ok(buf)
-}
-
-fn read_null_terminated_string(cursor: &mut Cursor<&[u8]>) -> Result<String> {
-    let buf = read_null_terminated_vec(cursor)?;
-    Ok(String::from_utf8(buf).unwrap())
-}
-
-fn read_len8_prefixed_vec(cursor: &mut Cursor<&[u8]>) -> Result<Vec<u8>> {
-    let len = read_u8(cursor)?;
-    let mut buf = vec![0u8; len as usize];
-    cursor.read_exact(&mut buf)?;
-    Ok(buf)
-}
-
-fn read_len8_prefixed_string(cursor: &mut Cursor<&[u8]>) -> Result<String> {
-    let buf = read_len8_prefixed_vec(cursor)?;
-    Ok(String::from_utf8(buf).unwrap())
-}
-
-fn read_ipv4(cursor: &mut Cursor<&[u8]>) -> Result<Ipv4Addr> {
-    Ok(Ipv4Addr::from_octets(read_arr(cursor)?))
-}
-
-fn read_op(cursor: &mut Cursor<&[u8]>) -> Result<BootOp> {
-    let v = read_u8(cursor)?;
-    match v {
-        BootOp::OP_REQUEST => Ok(BootOp::Request),
-        BootOp::OP_REPLY => Ok(BootOp::Reply),
-        _ => Err(std::io::Error::new(
-            std::io::ErrorKind::InvalidData,
-            "invalid boot op",
-        )),
-    }
-}
-
-fn read_htype(cursor: &mut Cursor<&[u8]>) -> Result<HardwareType> {
-    match read_u8(cursor)? {
-        HardwareType::TYPE_ETHER => Ok(HardwareType::Ethernet),
-        _ => Err(std::io::Error::new(
-            std::io::ErrorKind::InvalidData,
-            "invalid hardware type",
-        )),
-    }
-}
-
-fn read_option(cursor: &mut Cursor<&[u8]>) -> Result<DhcpOption> {
-    let code = read_u8(cursor)?;
-    Ok(match code {
-        OPTION_CODE_PAD => DhcpOption::Pad,
-        OPTION_CODE_END => DhcpOption::End,
-        OPTION_CODE_VENDOR_CLASS_IDENTIFIER => {
-            DhcpOption::VendorClassIdentifier(read_len8_prefixed_string(cursor)?)
-        }
-        OPTION_CODE_USER_CLASS_INFORMATION => {
-            DhcpOption::UserClassInformation(read_len8_prefixed_string(cursor)?)
-        }
-        _ => {
-            let len = read_u8(cursor)?;
-            let mut data = vec![0u8; usize::from(len)];
-            cursor.read_exact(&mut data)?;
-            DhcpOption::Unknown { code, data }
-        }
-    })
-}
-
-fn parse_packet(buf: &[u8]) -> Result<DhcpPacket> {
-    let mut cursor = Cursor::new(buf);
-    let mut packet = DhcpPacket {
-        op: read_op(&mut cursor)?,
-        htype: read_htype(&mut cursor)?,
-        hlen: read_u8(&mut cursor)?,
-        hops: read_u8(&mut cursor)?,
-        xid: read_u32(&mut cursor)?,
-        secs: read_u16(&mut cursor)?,
-        flags: read_u16(&mut cursor)?,
-        ciaddr: read_ipv4(&mut cursor)?,
-        yiaddr: read_ipv4(&mut cursor)?,
-        siaddr: read_ipv4(&mut cursor)?,
-        giaddr: read_ipv4(&mut cursor)?,
-        chaddr: read_arr(&mut cursor)?,
-        sname: read_arr(&mut cursor)?,
-        file: read_arr(&mut cursor)?,
-        options: Default::default(),
-    };
-
-    let magic = read_arr::<4>(&mut cursor)?;
-    assert_eq!(magic, MAGIC_COOKIE);
-
-    while cursor.position() < buf.len() as u64 {
-        let option = read_option(&mut cursor)?;
-        packet.options.push(option);
-    }
-
-    Ok(packet)
-}
-
-fn write_buf(writer: &mut Vec<u8>, buf: &[u8]) -> Result<()> {
-    writer.write_all(buf)
-}
-
-fn write_u8(writer: &mut Vec<u8>, v: u8) -> Result<()> {
-    write_buf(writer, &[v])
-}
-
-fn write_u16(writer: &mut Vec<u8>, v: u16) -> Result<()> {
-    let buf = u16::to_be_bytes(v);
-    write_buf(writer, &buf)
-}
-
-fn write_u32(writer: &mut Vec<u8>, v: u32) -> Result<()> {
-    let buf = u32::to_be_bytes(v);
-    write_buf(writer, &buf)
-}
-
-fn write_ipv4(writer: &mut Vec<u8>, v: Ipv4Addr) -> Result<()> {
-    write_buf(writer, &v.octets())
-}
-
-fn write_boot_packet(
-    xid: u32,
-    chaddr: [u8; 16],
-    client_uuid: Option<Vec<u8>>,
-    ipxe: bool,
-) -> Result<Vec<u8>> {
-    let mut writer = Vec::default();
-    write_u8(&mut writer, BootOp::OP_REPLY)?;
-    write_u8(&mut writer, HardwareType::TYPE_ETHER)?;
-    write_u8(&mut writer, 6)?;
-    write_u8(&mut writer, 0)?;
-    write_u32(&mut writer, xid)?;
-    write_u16(&mut writer, 0)?;
-    write_u16(&mut writer, FLAG_BROADCAST)?;
-    write_ipv4(&mut writer, Ipv4Addr::UNSPECIFIED)?; // ciaddr
-    write_ipv4(&mut writer, Ipv4Addr::UNSPECIFIED)?; // yiaddr  
-    write_ipv4(&mut writer, LOCAL_IPV4)?; // siaddr (TFTP server)
-    write_ipv4(&mut writer, Ipv4Addr::UNSPECIFIED)?; // giaddr
-    write_buf(&mut writer, &chaddr)?;
-    write_buf(&mut writer, &[0u8; 64])?;
-    write_buf(&mut writer, &[0u8; 128])?;
-    write_buf(&mut writer, &MAGIC_COOKIE)?;
-
-    // Option 53: DHCP Message Type (DHCPOFFER)
-    write_u8(&mut writer, 53)?;
-    write_u8(&mut writer, 1)?;
-    write_u8(&mut writer, 2)?; // DHCPOFFER
-
-    // Option 54: DHCP Server Identifier
-    write_u8(&mut writer, 54)?;
-    write_u8(&mut writer, 4)?;
-    write_ipv4(&mut writer, LOCAL_IPV4)?; // Your server IP
-
-    // Option 60: Vendor Class Identifier
-    const PXE_CLIENT: &[u8] = b"PXEClient";
-    write_u8(&mut writer, 60)?;
-    write_u8(&mut writer, PXE_CLIENT.len() as u8)?;
-    write_buf(&mut writer, PXE_CLIENT)?;
-
-    // Option 97: Client Machine Identifier (UUID from client)
-    if let Some(uuid) = client_uuid {
-        write_u8(&mut writer, 97)?;
-        write_u8(&mut writer, uuid.len() as u8)?;
-        write_buf(&mut writer, &uuid)?;
-    }
-
-    // TFTP server name
-    const SERVER_NAME: &[u8] = b"diogos-air";
-    write_u8(&mut writer, 66)?;
-    write_u8(&mut writer, SERVER_NAME.len() as u8)?;
-    write_buf(&mut writer, SERVER_NAME)?;
-
-    write_u8(&mut writer, 67)?;
-    if !ipxe {
-        write_u8(&mut writer, BOOT_FILE_NAME.len() as u8)?;
-        write_buf(&mut writer, BOOT_FILE_NAME)?;
-    } else {
-        write_u8(&mut writer, BOOT_FILE_NAME_IPXE.len() as u8)?;
-        write_buf(&mut writer, BOOT_FILE_NAME_IPXE)?;
-    }
-
-    // Option 255: End
-    write_u8(&mut writer, 255)?;
-
-    Ok(writer)
-}
-
-fn write_boot_ack(xid: u32, chaddr: [u8; 16], client_uuid: Option<Vec<u8>>) -> Result<Vec<u8>> {
-    let mut writer = Vec::default();
-    write_u8(&mut writer, BootOp::OP_REPLY)?;
-    write_u8(&mut writer, HardwareType::TYPE_ETHER)?;
-    write_u8(&mut writer, 6)?;
-    write_u8(&mut writer, 0)?;
-    write_u32(&mut writer, xid)?;
-    write_u16(&mut writer, 0)?;
-    write_u16(&mut writer, 0)?;
-    write_ipv4(&mut writer, Ipv4Addr::UNSPECIFIED)?; // ciaddr
-    write_ipv4(&mut writer, Ipv4Addr::UNSPECIFIED)?; // yiaddr  
-    write_ipv4(&mut writer, Ipv4Addr::UNSPECIFIED)?; // siaddr (TFTP server)
-    write_ipv4(&mut writer, Ipv4Addr::UNSPECIFIED)?; // giaddr
-    write_buf(&mut writer, &chaddr)?;
-    write_buf(&mut writer, &[0u8; 64])?;
-    write_buf(&mut writer, &[0u8; 128])?;
-    write_buf(&mut writer, &MAGIC_COOKIE)?;
-
-    // Option 53: DHCP Message Type (DHCPOFFER)
-    write_u8(&mut writer, 53)?;
-    write_u8(&mut writer, 1)?;
-    write_u8(&mut writer, 5)?; // DHCPACK
-
-    // Option 54: DHCP Server Identifier
-    write_u8(&mut writer, 54)?;
-    write_u8(&mut writer, 4)?;
-    write_ipv4(&mut writer, LOCAL_IPV4)?; // Your server IP
-
-    // Option 60: Vendor Class Identifier
-    const PXE_CLIENT: &[u8] = b"PXEClient";
-    write_u8(&mut writer, 60)?;
-    write_u8(&mut writer, PXE_CLIENT.len() as u8)?;
-    write_buf(&mut writer, PXE_CLIENT)?;
-
-    // Option 97: Client Machine Identifier (UUID from client)
-    if let Some(uuid) = client_uuid {
-        write_u8(&mut writer, 97)?;
-        write_u8(&mut writer, uuid.len() as u8)?;
-        write_buf(&mut writer, &uuid)?;
-    }
-
-    // TFTP server name
-    const SERVER_NAME: &[u8] = b"diogos-air";
-    write_u8(&mut writer, 66)?;
-    write_u8(&mut writer, SERVER_NAME.len() as u8)?;
-    write_buf(&mut writer, SERVER_NAME)?;
-
-    // TFTP file name
-    write_u8(&mut writer, 67)?;
-    write_u8(&mut writer, BOOT_FILE_NAME.len() as u8)?;
-    write_buf(&mut writer, BOOT_FILE_NAME)?;
-
-    write_u8(&mut writer, 71)?;
-    write_u8(&mut writer, 4)?;
-    write_buf(&mut writer, &[0, 0, 0, 0])?;
-
-    // Option 255: End
-    write_u8(&mut writer, 255)?;
-
-    Ok(writer)
-}
+const LOCAL_IPV4: Ipv4Addr = Ipv4Addr::new(192, 168, 1, 103);
+const LOCAL_HOSTNAME: &'static str = "Diogos-Air";
 
 #[derive(Debug, Clone)]
 struct InterfaceAddr {
@@ -433,7 +99,7 @@ fn main() {
 }
 
 fn handle_packet(buf: &[u8], socket: &UdpSocket) {
-    match parse_packet(buf) {
+    match dhcp::parse_packet(buf) {
         Ok(packet) => {
             println!("Parsed DHCP packet: XID={:08x}", packet.xid);
 
@@ -464,10 +130,21 @@ fn handle_packet(buf: &[u8], socket: &UdpSocket) {
 
             if is_pxe {
                 println!("Responding to PXE client with DHCPOFFER");
-                let response =
-                    write_boot_packet(packet.xid, packet.chaddr, client_uuid, is_ipxe).unwrap();
+                let mut response_buf = Vec::default();
+                let response = DhcpPacket::new_boot(
+                    packet.xid,
+                    packet.chaddr,
+                    client_uuid.unwrap(),
+                    LOCAL_IPV4,
+                    LOCAL_HOSTNAME.to_string(),
+                    match is_ipxe {
+                        true => "test.ipxe".to_string(),
+                        false => "ipxe.efi".to_string(),
+                    },
+                );
+                response.write(&mut response_buf).unwrap();
                 socket
-                    .send_to(&response, SocketAddrV4::new(Ipv4Addr::BROADCAST, 68))
+                    .send_to(&response_buf, SocketAddrV4::new(Ipv4Addr::BROADCAST, 68))
                     .unwrap();
             } else {
                 println!("Not a PXE client, ignoring");
@@ -480,7 +157,7 @@ fn handle_packet(buf: &[u8], socket: &UdpSocket) {
 }
 
 fn handle_packet_4011(buf: &[u8], socket: &UdpSocket, sender_addr: SocketAddr) {
-    match parse_packet(buf) {
+    match dhcp::parse_packet(buf) {
         Ok(packet) => {
             println!("Parsed DHCP packet on 4011: XID={:08x}", packet.xid);
 
@@ -494,8 +171,17 @@ fn handle_packet_4011(buf: &[u8], socket: &UdpSocket, sender_addr: SocketAddr) {
             }
 
             println!("Responding with DHCPACK");
-            let response = write_boot_ack(packet.xid, packet.chaddr, client_uuid).unwrap();
-            socket.send_to(&response, sender_addr).unwrap();
+            let mut response_buf = Vec::default();
+            let response = DhcpPacket::new_boot_ack(
+                packet.xid,
+                packet.chaddr,
+                client_uuid.unwrap(),
+                LOCAL_IPV4,
+                LOCAL_HOSTNAME.to_string(),
+                "ipxe.efi".to_string(),
+            );
+            response.write(&mut response_buf).unwrap();
+            socket.send_to(&response_buf, sender_addr).unwrap();
         }
         Err(e) => {
             println!("Failed to parse packet on 4011: {}", e);