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Adding DHCP lease management #437

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merged 8 commits into from
Mar 24, 2021
Merged

Adding DHCP lease management #437

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3eea096
Adding DHCP lease management
ryan-summers Mar 12, 2021
bda278f
Refactoring retry mechanism
ryan-summers Mar 12, 2021
532fb02
Updating control logic
ryan-summers Mar 12, 2021
267084a
Adding parsing test with lease time
ryan-summers Mar 12, 2021
e3954eb
Adding changelog
ryan-summers Mar 12, 2021
921a962
Removing lease expiration on reset - the lease does not expire
ryan-summers Mar 18, 2021
90ebf97
Merge branch 'master' into feature/dhcp-lease-updates
Dirbaio Mar 24, 2021
d3954e2
Merge branch 'master' into feature/dhcp-lease-updates
Dirbaio Mar 24, 2021
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3 changes: 2 additions & 1 deletion CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

## [Unreleased]

No unreleased changes yet
### New features
* dhcp: Updated DHCP client to respect lease times provided by the server.

## [0.7.0] - 2021-01-20

Expand Down
48 changes: 22 additions & 26 deletions src/dhcp/clientv4.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,8 +13,7 @@ use super::{UDP_SERVER_PORT, UDP_CLIENT_PORT};
const DISCOVER_TIMEOUT: u64 = 10;
const REQUEST_TIMEOUT: u64 = 1;
const REQUEST_RETRIES: u16 = 15;
const RENEW_INTERVAL: u64 = 60;
const RENEW_RETRIES: u16 = 3;
const DEFAULT_RENEW_INTERVAL: u32 = 60;
const PARAMETER_REQUEST_LIST: &[u8] = &[
dhcpv4_field::OPT_SUBNET_MASK,
dhcpv4_field::OPT_ROUTER,
Expand All @@ -39,7 +38,6 @@ struct RequestState {

#[derive(Debug)]
struct RenewState {
retry: u16,
endpoint_ip: Ipv4Address,
server_identifier: Ipv4Address,
}
Expand All @@ -59,6 +57,8 @@ pub struct Client {
raw_handle: SocketHandle,
/// When to send next request
next_egress: Instant,
/// When any existing DHCP address will expire.
lease_expiration: Option<Instant>,
transaction_id: u32,
}

Expand Down Expand Up @@ -104,6 +104,7 @@ impl Client {
raw_handle,
next_egress: now,
transaction_id: 1,
lease_expiration: None,
}
}

Expand Down Expand Up @@ -199,12 +200,18 @@ impl Client {

// once we receive the ack, we can pass the config to the user
let config = if dhcp_repr.message_type == DhcpMessageType::Ack {
let address = dhcp_repr.subnet_mask
.and_then(|mask| IpAddress::Ipv4(mask).to_prefix_len())
.map(|prefix_len| Ipv4Cidr::new(dhcp_repr.your_ip, prefix_len));
let router = dhcp_repr.router;
let dns_servers = dhcp_repr.dns_servers
.unwrap_or([None; 3]);
let lease_duration = dhcp_repr.lease_duration.unwrap_or(DEFAULT_RENEW_INTERVAL * 2);
self.lease_expiration = Some(now + Duration::from_secs(lease_duration.into()));

// RFC 2131 indicates clients should renew a lease halfway through its expiration.
self.next_egress = now + Duration::from_secs((lease_duration / 2).into());

let address = dhcp_repr.subnet_mask
.and_then(|mask| IpAddress::Ipv4(mask).to_prefix_len())
.map(|prefix_len| Ipv4Cidr::new(dhcp_repr.your_ip, prefix_len));
let router = dhcp_repr.router;
let dns_servers = dhcp_repr.dns_servers
.unwrap_or([None; 3]);
Some(Config { address, router, dns_servers })
} else {
None
Expand All @@ -227,22 +234,12 @@ impl Client {
if dhcp_repr.message_type == DhcpMessageType::Ack &&
server_identifier == r_state.server_identifier =>
{
self.next_egress = now + Duration::from_secs(RENEW_INTERVAL);
let p_state = RenewState {
retry: 0,
endpoint_ip: *src_ip,
server_identifier,
};
Some(ClientState::Renew(p_state))
}
ClientState::Renew(ref mut p_state)
if dhcp_repr.message_type == DhcpMessageType::Ack &&
server_identifier == p_state.server_identifier =>
{
self.next_egress = now + Duration::from_secs(RENEW_INTERVAL);
p_state.retry = 0;
None
}
_ => None
}.map(|new_state| self.state = new_state);

Expand All @@ -256,13 +253,12 @@ impl Client {
net_debug!("DHCP request retries exceeded, restarting discovery");
true
}
ClientState::Renew(ref mut r_state) if r_state.retry >= RENEW_RETRIES => {
net_debug!("DHCP renew retries exceeded, restarting discovery");
true
}
_ => false
};
if retries_exceeded {

let lease_expired = self.lease_expiration.map_or(false, |expiration| now >= expiration);

if lease_expired || retries_exceeded {
self.reset(now);
// Return a config now so that user code assigns the
// 0.0.0.0/0 address, which will be used sending a DHCP
Expand Down Expand Up @@ -294,6 +290,7 @@ impl Client {
server_identifier: None,
parameter_request_list: None,
max_size: Some(raw_socket.payload_recv_capacity() as u16),
lease_duration: None,
dns_servers: None,
};
let mut send_packet = |iface, endpoint, dhcp_repr| {
Expand Down Expand Up @@ -329,8 +326,7 @@ impl Client {
send_packet(iface, endpoint, dhcp_repr)
}
ClientState::Renew(ref mut p_state) => {
p_state.retry += 1;
self.next_egress = now + Duration::from_secs(RENEW_INTERVAL);
self.next_egress = now + Duration::from_secs(DEFAULT_RENEW_INTERVAL.into());

let endpoint = IpEndpoint {
addr: p_state.endpoint_ip.into(),
Expand Down
57 changes: 55 additions & 2 deletions src/wire/dhcpv4.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,7 @@ pub enum DhcpOption<'a> {
RequestedIp(Ipv4Address),
ClientIdentifier(EthernetAddress),
ServerIdentifier(Ipv4Address),
IpLeaseTime(u32),
Router(Ipv4Address),
SubnetMask(Ipv4Address),
MaximumDhcpMessageSize(u16),
Expand Down Expand Up @@ -103,6 +104,9 @@ impl<'a> DhcpOption<'a> {
(field::OPT_MAX_DHCP_MESSAGE_SIZE, 2) => {
option = DhcpOption::MaximumDhcpMessageSize(u16::from_be_bytes([data[0], data[1]]));
}
(field::OPT_IP_LEASE_TIME, 4) => {
option = DhcpOption::IpLeaseTime(u32::from_be_bytes([data[0], data[1], data[2], data[3]]))
}
(_, _) => {
option = DhcpOption::Other { kind: kind, data: data };
}
Expand All @@ -129,6 +133,7 @@ impl<'a> DhcpOption<'a> {
&DhcpOption::MaximumDhcpMessageSize(_) => {
4
}
&DhcpOption::IpLeaseTime(_) => 6,
&DhcpOption::Other { data, .. } => 2 + data.len()
}
}
Expand Down Expand Up @@ -178,6 +183,10 @@ impl<'a> DhcpOption<'a> {
buffer[0] = field::OPT_MAX_DHCP_MESSAGE_SIZE;
buffer[2..4].copy_from_slice(&size.to_be_bytes()[..]);
}
DhcpOption::IpLeaseTime(lease_time) => {
buffer[0] = field::OPT_IP_LEASE_TIME;
buffer[2..6].copy_from_slice(&lease_time.to_be_bytes()[..]);
}
DhcpOption::Other { kind, data: provided } => {
buffer[0] = kind;
buffer[2..skip_length].copy_from_slice(provided);
Expand Down Expand Up @@ -674,6 +683,8 @@ pub struct Repr<'a> {
pub dns_servers: Option<[Option<Ipv4Address>; 3]>,
/// The maximum size dhcp packet the interface can receive
pub max_size: Option<u16>,
/// The DHCP IP lease duration, specified in seconds.
pub lease_duration: Option<u32>
}

impl<'a> Repr<'a> {
Expand Down Expand Up @@ -725,6 +736,7 @@ impl<'a> Repr<'a> {
let mut parameter_request_list = None;
let mut dns_servers = None;
let mut max_size = None;
let mut lease_duration = None;

let mut options = packet.options()?;
while !options.is_empty() {
Expand Down Expand Up @@ -755,6 +767,9 @@ impl<'a> Repr<'a> {
DhcpOption::MaximumDhcpMessageSize(size) => {
max_size = Some(size);
}
DhcpOption::IpLeaseTime(duration) => {
lease_duration = Some(duration);
}
DhcpOption::Other {kind: field::OPT_PARAMETER_REQUEST_LIST, data} => {
parameter_request_list = Some(data);
}
Expand All @@ -776,6 +791,7 @@ impl<'a> Repr<'a> {
transaction_id, client_hardware_address, client_ip, your_ip, server_ip, relay_agent_ip,
broadcast, requested_ip, server_identifier, router,
subnet_mask, client_identifier, parameter_request_list, dns_servers, max_size,
lease_duration,
message_type: message_type?,
})
}
Expand Down Expand Up @@ -820,6 +836,9 @@ impl<'a> Repr<'a> {
if let Some(size) = self.max_size {
let tmp = options; options = DhcpOption::MaximumDhcpMessageSize(size).emit(tmp);
}
if let Some(duration) = self.lease_duration {
let tmp = options; options = DhcpOption::IpLeaseTime(duration).emit(tmp);
}
if let Some(list) = self.parameter_request_list {
let option = DhcpOption::Other{ kind: field::OPT_PARAMETER_REQUEST_LIST, data: list };
let tmp = options; options = option.emit(tmp);
Expand Down Expand Up @@ -858,7 +877,7 @@ mod test {
0x00, 0x00, 0x39, 0x2, 0x5, 0xdc, 0x37, 0x04, 0x01, 0x03, 0x06, 0x2a, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
];

static ACK_BYTES: &[u8] = &[
static ACK_DNS_SERVER_BYTES: &[u8] = &[
0x02, 0x01, 0x06, 0x00, 0xcc, 0x34, 0x75, 0xab, 0x00, 0x00, 0x80, 0x00, 0x0a, 0xff, 0x06, 0x91,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0a, 0xff, 0x06, 0xfe, 0x34, 0x17, 0xeb, 0xc9,
0xaa, 0x2f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
Expand All @@ -882,6 +901,28 @@ mod test {
0x01, 0x4a, 0x06, 0xa3, 0x01, 0x4a, 0x07, 0x2e, 0x01, 0x08, 0xff
];

static ACK_LEASE_TIME_BYTES: &[u8] = &[
0x02, 0x01, 0x06, 0x00, 0x00, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x0a, 0x22, 0x10, 0x0b, 0x0a, 0x22, 0x10, 0x0a, 0x00, 0x00, 0x00, 0x00, 0x04, 0x91, 0x62, 0xd2,
0xa8, 0x6f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x63, 0x82, 0x53, 0x63,
0x35, 0x01, 0x05, 0x36, 0x04, 0x0a, 0x22, 0x10, 0x0a, 0x33, 0x04, 0x00, 0x00, 0x02, 0x56, 0x01,
0x04, 0xff, 0xff, 0xff, 0x00, 0x03, 0x04, 0x0a, 0x22, 0x10, 0x0a, 0xff, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
];

const IP_NULL: Ipv4Address = Ipv4Address([0, 0, 0, 0]);
const CLIENT_MAC: EthernetAddress = EthernetAddress([0x0, 0x0b, 0x82, 0x01, 0xfc, 0x42]);
const DHCP_SIZE: u16 = 1500;
Expand Down Expand Up @@ -984,6 +1025,7 @@ mod test {
relay_agent_ip: IP_NULL,
broadcast: false,
max_size: Some(DHCP_SIZE),
lease_duration: None,
requested_ip: Some(IP_NULL),
client_identifier: Some(CLIENT_MAC),
server_identifier: None,
Expand Down Expand Up @@ -1031,8 +1073,9 @@ mod test {

#[test]
fn test_parse_ack_dns_servers() {
let packet = Packet::new_unchecked(ACK_BYTES);
let packet = Packet::new_unchecked(ACK_DNS_SERVER_BYTES);
let repr = Repr::parse(&packet).unwrap();

// The packet described by ACK_BYTES advertises 4 DNS servers
// Here we ensure that we correctly parse the first 3 into our fixed
// length-3 array (see issue #305)
Expand All @@ -1041,4 +1084,14 @@ mod test {
Some(Ipv4Address([163, 1, 74, 7])),
Some(Ipv4Address([163, 1, 74, 3]))]));
}

#[test]
fn test_parse_ack_lease_duration() {
let packet = Packet::new_unchecked(ACK_LEASE_TIME_BYTES);
let repr = Repr::parse(&packet).unwrap();

// Verify that the lease time in the ACK is properly parsed. The packet contains a lease
// duration of 598s.
assert_eq!(repr.lease_duration, Some(598));
}
}