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Add a few DHCP options #255

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3f68033
Add a few DHCP options
astro Jul 24, 2018
565cdad
Add IpAddress.to_prefix_len()
astro Jul 24, 2018
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1 change: 1 addition & 0 deletions Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,7 @@ verbose = []
"socket-udp" = []
"socket-tcp" = []
"socket-icmp" = []
"proto-dhcpv4" = ["proto-ipv4"]
default = [
"std", "log", # needed for `cargo test --no-default-features --features default` :/
"phy-raw_socket", "phy-tap_interface",
Expand Down
60 changes: 57 additions & 3 deletions src/wire/dhcpv4.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,8 @@ pub enum DhcpOption<'a> {
RequestedIp(Ipv4Address),
ClientIdentifier(EthernetAddress),
ServerIdentifier(Ipv4Address),
Router(Ipv4Address),
SubnetMask(Ipv4Address),
Other { kind: u8, data: &'a [u8] }
}

Expand Down Expand Up @@ -91,6 +93,12 @@ impl<'a> DhcpOption<'a> {
(field::OPT_SERVER_IDENTIFIER, 4) => {
option = DhcpOption::ServerIdentifier(Ipv4Address::from_bytes(data));
}
(field::OPT_ROUTER, 4) => {
option = DhcpOption::Router(Ipv4Address::from_bytes(data));
}
(field::OPT_SUBNET_MASK, 4) => {
option = DhcpOption::SubnetMask(Ipv4Address::from_bytes(data));
}
(_, _) => {
option = DhcpOption::Other { kind: kind, data: data };
}
Expand All @@ -108,7 +116,10 @@ impl<'a> DhcpOption<'a> {
&DhcpOption::ClientIdentifier(eth_addr) => {
3 + eth_addr.as_bytes().len()
}
&DhcpOption::RequestedIp(ip) | &DhcpOption::ServerIdentifier(ip) => {
&DhcpOption::RequestedIp(ip) |
&DhcpOption::ServerIdentifier(ip) |
&DhcpOption::Router(ip) |
&DhcpOption::SubnetMask(ip) => {
2 + ip.as_bytes().len()
},
&DhcpOption::Other { data, .. } => 2 + data.len()
Expand Down Expand Up @@ -148,6 +159,14 @@ impl<'a> DhcpOption<'a> {
buffer[0] = field::OPT_SERVER_IDENTIFIER;
buffer[2..6].copy_from_slice(ip.as_bytes());
}
&DhcpOption::Router(ip) => {
buffer[0] = field::OPT_ROUTER;
buffer[2..6].copy_from_slice(ip.as_bytes());
}
&DhcpOption::SubnetMask(mask) => {
buffer[0] = field::OPT_SUBNET_MASK;
buffer[2..6].copy_from_slice(mask.as_bytes());
}
&DhcpOption::Other { kind, data: provided } => {
buffer[0] = kind;
buffer[2..skip_length].copy_from_slice(provided);
Expand All @@ -165,7 +184,7 @@ pub struct Packet<T: AsRef<[u8]>> {
buffer: T
}

mod field {
pub(crate) mod field {
#![allow(non_snake_case)]
#![allow(unused)]

Expand Down Expand Up @@ -603,6 +622,10 @@ pub struct Repr<'a> {
/// This field is also known as `siaddr` in the RFC. It may be set by the server in DHCPOFFER
/// and DHCPACK messages, and represent the address of the next server to use in bootstrap.
pub server_ip: Ipv4Address,
/// Default gateway
pub router: Option<Ipv4Address>,
/// This field comes from a corresponding DhcpOption.
pub subnet_mask: Option<Ipv4Address>,
/// This field is also known as `giaddr` in the RFC. In order to allow DHCP clients on subnets
/// not directly served by DHCP servers to communicate with DHCP servers, DHCP relay agents can
/// be installed on these subnets. The DHCP client broadcasts on the local link; the relay
Expand Down Expand Up @@ -635,6 +658,8 @@ pub struct Repr<'a> {
/// The parameter request list informs the server about which configuration parameters
/// the client is interested in.
pub parameter_request_list: Option<&'a [u8]>,
/// DNS servers
pub dns_servers: Option<[Option<Ipv4Address>; 3]>,
}

impl<'a> Repr<'a> {
Expand Down Expand Up @@ -680,7 +705,10 @@ impl<'a> Repr<'a> {
let mut requested_ip = None;
let mut client_identifier = None;
let mut server_identifier = None;
let mut router = None;
let mut subnet_mask = None;
let mut parameter_request_list = None;
let mut dns_servers = None;

let mut options = packet.options()?;
while options.len() > 0 {
Expand All @@ -702,9 +730,25 @@ impl<'a> Repr<'a> {
DhcpOption::ServerIdentifier(ip) => {
server_identifier = Some(ip);
}
DhcpOption::Router(ip) => {
router = Some(ip);
}
DhcpOption::SubnetMask(mask) => {
subnet_mask = Some(mask);
}
DhcpOption::Other {kind: field::OPT_PARAMETER_REQUEST_LIST, data} => {
parameter_request_list = Some(data);
}
DhcpOption::Other {kind: field::OPT_DOMAIN_NAME_SERVER, data} => {
let mut dns_servers_inner = [None; 3];
for i in 0.. {
let offset = 4 * i;
let end = offset + 4;
if end > data.len() { break }
dns_servers_inner[i] = Some(Ipv4Address::from_bytes(&data[offset..end]));
}
dns_servers = Some(dns_servers_inner);
}
DhcpOption::Other {..} => {}
}
options = next_options;
Expand All @@ -714,7 +758,8 @@ impl<'a> Repr<'a> {

Ok(Repr {
transaction_id, client_hardware_address, client_ip, your_ip, server_ip, relay_agent_ip,
broadcast, requested_ip, server_identifier, client_identifier, parameter_request_list,
broadcast, requested_ip, server_identifier, router,
subnet_mask, client_identifier, parameter_request_list, dns_servers,
message_type: message_type?,
})
}
Expand Down Expand Up @@ -746,6 +791,12 @@ impl<'a> Repr<'a> {
if let Some(ip) = self.server_identifier {
let tmp = options; options = DhcpOption::ServerIdentifier(ip).emit(tmp);
}
if let Some(ip) = self.router {
let tmp = options; options = DhcpOption::Router(ip).emit(tmp);
}
if let Some(ip) = self.subnet_mask {
let tmp = options; options = DhcpOption::SubnetMask(ip).emit(tmp);
}
if let Some(ip) = self.requested_ip {
let tmp = options; options = DhcpOption::RequestedIp(ip).emit(tmp);
}
Expand Down Expand Up @@ -878,12 +929,15 @@ mod test {
client_ip: IP_NULL,
your_ip: IP_NULL,
server_ip: IP_NULL,
router: None,
subnet_mask: None,
relay_agent_ip: IP_NULL,
broadcast: false,
requested_ip: Some(IP_NULL),
client_identifier: Some(CLIENT_MAC),
server_identifier: None,
parameter_request_list: Some(&[1, 3, 6, 42]),
dns_servers: None,
}
}

Expand Down
97 changes: 97 additions & 0 deletions src/wire/ip.rs
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Expand Up @@ -184,6 +184,34 @@ impl Address {
&Address::__Nonexhaustive => unreachable!()
}
}

/// If `self` is a CIDR-compatible subnet mask, return `Some(prefix_len)`,
/// where `prefix_len` is the number of leading zeroes. Return `None` otherwise.
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@whitequark whitequark Jul 31, 2018

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This docstring wasn't particularly great; I fixed it.

pub fn to_prefix_len(&self) -> Option<u8> {
let mut ones = true;
let mut prefix_len = 0;
for byte in self.as_bytes() {
let mut mask = 0x80;
for _ in 0..8 {
let one = *byte & mask != 0;
if ones {
// Expect 1s until first 0
if one {
prefix_len += 1;
} else {
ones = false;
}
} else {
if one {
// 1 where 0 was expected
return None
}
}
mask >>= 1;
}
}
Some(prefix_len)
}
}

#[cfg(all(feature = "std", feature = "proto-ipv4", feature = "proto-ipv6"))]
Expand Down Expand Up @@ -1074,4 +1102,73 @@ pub(crate) mod test {
fn endpoint_unspecified() {
assert!(!Endpoint::UNSPECIFIED.is_specified());
}

#[test]
#[cfg(feature = "proto-ipv4")]
fn to_prefix_len_ipv4() {
fn test_eq<A: Into<Address>>(prefix_len: u8, mask: A) {
assert_eq!(
Some(prefix_len),
mask.into().to_prefix_len()
);
}

test_eq(0, Ipv4Address::new(0, 0, 0, 0));
test_eq(1, Ipv4Address::new(128, 0, 0, 0));
test_eq(2, Ipv4Address::new(192, 0, 0, 0));
test_eq(3, Ipv4Address::new(224, 0, 0, 0));
test_eq(4, Ipv4Address::new(240, 0, 0, 0));
test_eq(5, Ipv4Address::new(248, 0, 0, 0));
test_eq(6, Ipv4Address::new(252, 0, 0, 0));
test_eq(7, Ipv4Address::new(254, 0, 0, 0));
test_eq(8, Ipv4Address::new(255, 0, 0, 0));
test_eq(9, Ipv4Address::new(255, 128, 0, 0));
test_eq(10, Ipv4Address::new(255, 192, 0, 0));
test_eq(11, Ipv4Address::new(255, 224, 0, 0));
test_eq(12, Ipv4Address::new(255, 240, 0, 0));
test_eq(13, Ipv4Address::new(255, 248, 0, 0));
test_eq(14, Ipv4Address::new(255, 252, 0, 0));
test_eq(15, Ipv4Address::new(255, 254, 0, 0));
test_eq(16, Ipv4Address::new(255, 255, 0, 0));
test_eq(17, Ipv4Address::new(255, 255, 128, 0));
test_eq(18, Ipv4Address::new(255, 255, 192, 0));
test_eq(19, Ipv4Address::new(255, 255, 224, 0));
test_eq(20, Ipv4Address::new(255, 255, 240, 0));
test_eq(21, Ipv4Address::new(255, 255, 248, 0));
test_eq(22, Ipv4Address::new(255, 255, 252, 0));
test_eq(23, Ipv4Address::new(255, 255, 254, 0));
test_eq(24, Ipv4Address::new(255, 255, 255, 0));
test_eq(25, Ipv4Address::new(255, 255, 255, 128));
test_eq(26, Ipv4Address::new(255, 255, 255, 192));
test_eq(27, Ipv4Address::new(255, 255, 255, 224));
test_eq(28, Ipv4Address::new(255, 255, 255, 240));
test_eq(29, Ipv4Address::new(255, 255, 255, 248));
test_eq(30, Ipv4Address::new(255, 255, 255, 252));
test_eq(31, Ipv4Address::new(255, 255, 255, 254));
test_eq(32, Ipv4Address::new(255, 255, 255, 255));
}

#[cfg(feature = "proto-ipv4")]
fn to_prefix_len_ipv4_error() {
assert_eq!(None, IpAddress::from(Ipv4Address::new(255,255,255,1)).to_prefix_len());
}

#[test]
#[cfg(feature = "proto-ipv6")]
fn to_prefix_len_ipv6() {
fn test_eq<A: Into<Address>>(prefix_len: u8, mask: A) {
assert_eq!(
Some(prefix_len),
mask.into().to_prefix_len()
);
}

test_eq(0, Ipv6Address::new(0, 0, 0, 0, 0, 0, 0, 0));
test_eq(128, Ipv6Address::new(0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff));
}

#[cfg(feature = "proto-ipv6")]
fn to_prefix_len_ipv6_error() {
assert_eq!(None, IpAddress::from(Ipv6Address::new(0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0, 1)).to_prefix_len());
}
}
9 changes: 5 additions & 4 deletions src/wire/mod.rs
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Expand Up @@ -109,8 +109,8 @@ mod ndiscoption;
mod mld;
mod udp;
mod tcp;
#[cfg(feature = "proto-ipv4")]
mod dhcpv4;
#[cfg(feature = "proto-dhcpv4")]
pub(crate) mod dhcpv4;

pub use self::pretty_print::PrettyPrinter;

Expand Down Expand Up @@ -216,6 +216,7 @@ pub use self::tcp::{SeqNumber as TcpSeqNumber,
Repr as TcpRepr,
Control as TcpControl};

#[cfg(feature = "proto-ipv4")]
#[cfg(feature = "proto-dhcpv4")]
pub use self::dhcpv4::{Packet as DhcpPacket,
Repr as DhcpRepr};
Repr as DhcpRepr,
MessageType as DhcpMessageType};