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document the dhcp packet representation (phil-opp/smoltcp#1) 

Closes: #75
Approved by: whitequark
v0.7.x
Corentin Henry 2017-11-18 15:59:09 -08:00 committed by Homu
parent 745df22709
commit 55e75fe85e
1 changed files with 70 additions and 0 deletions
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70
src/wire/dhcpv4.rs
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@ -540,16 +540,84 @@ impl<'a, T: AsRef<[u8]> + AsMut<[u8]> + ?Sized> Packet<&'a mut T> {
}
/// A high-level representation of a Dynamic Host Configuration Protocol packet.
///
/// DHCP messages have the following layout (see [RFC 2131](https://tools.ietf.org/html/rfc2131)
/// for details):
///
/// ```no_rust
/// 0 1 2 3
/// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// | message_type | htype (N/A) | hlen (N/A) | hops |
/// +---------------+---------------+---------------+---------------+
/// | transaction_id |
/// +-------------------------------+-------------------------------+
/// | secs | flags |
/// +-------------------------------+-------------------------------+
/// | client_ip |
/// +---------------------------------------------------------------+
/// | your_ip |
/// +---------------------------------------------------------------+
/// | server_ip |
/// +---------------------------------------------------------------+
/// | relay_agent_ip |
/// +---------------------------------------------------------------+
/// | |
/// | client_hardware_address |
/// | |
/// | |
/// +---------------------------------------------------------------+
/// | |
/// | sname (N/A) |
/// +---------------------------------------------------------------+
/// | |
/// | file (N/A) |
/// +---------------------------------------------------------------+
/// | |
/// | options |
/// +---------------------------------------------------------------+
/// ```
///
/// It is assumed that the access layer is Ethernet, so `htype` (the field representing the
/// hardware address type) is always set to `1`, and `hlen` (which represents the hardware address
/// length) is set to `6`.
///
/// The `options` field has a variable length.
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub struct Repr<'a> {
/// This field is also known as `op` in the RFC. It indicates the type of DHCP message this
/// packet represents.
pub message_type: MessageType,
/// This field is also known as `xid` in the RFC. It is a random number chosen by the client,
/// used by the client and server to associate messages and responses between a client and a
/// server.
pub transaction_id: u32,
/// This field is also known as `chaddr` in the RFC and for networks where the access layer is
/// ethernet, it is the client MAC address.
pub client_hardware_address: EthernetAddress,
/// This field is also known as `ciaddr` in the RFC. It is only filled in if client is in
/// BOUND, RENEW or REBINDING state and can respond to ARP requests.
pub client_ip: Ipv4Address,
/// This field is also known as `yiaddr` in the RFC.
pub your_ip: Ipv4Address,
/// 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,
/// 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
/// agent receives the broadcast and transmits it to one or more DHCP servers using unicast.
/// The relay agent stores its own IP address in the `relay_agent_ip` field of the DHCP packet.
/// The DHCP server uses the `relay_agent_ip` to determine the subnet on which the relay agent
/// received the broadcast, and allocates an IP address on that subnet. When the DHCP server
/// replies to the client, it sends the reply to the `relay_agent_ip` address, again using
/// unicast. The relay agent then retransmits the response on the local network
pub relay_agent_ip: Ipv4Address,
/// Broadcast flags. It can be set in DHCPDISCOVER, DHCPINFORM and DHCPREQUEST message if the
/// client requires the response to be broadcasted.
pub broadcast: bool,
/// The "requested IP address" option. It can be used by clients in DHCPREQUEST or DHCPDISCOVER
/// messages, or by servers in DHCPDECLINE messages.
pub requested_ip: Option<Ipv4Address>,
/// The "client identifier" option.
///
@ -561,6 +629,8 @@ pub struct Repr<'a> {
/// it MUST use that same identifier in all subsequent messages, to ensure that all servers
/// correctly identify the client.
pub client_identifier: Option<EthernetAddress>,
/// The "server identifier" option. It is used both to identify a DHCP server
/// in a DHCP message and as a destination address from clients to servers.
pub server_identifier: Option<Ipv4Address>,
/// The parameter request list informs the server about which configuration parameters
/// the client is interested in.