Module wire

Low-level packet access and construction.

The wire module deals with the packet representation. It provides two levels of functionality.

• First, it provides functions to extract fields from sequences of octets, and to insert fields into sequences of octets. This happens Packet family of structures, e.g. EthernetFrame or Ipv4Packet.
• Second, in cases where the space of valid field values is much smaller than the space of possible field values, it provides a compact, high-level representation of packet data that can be parsed from and emitted into a sequence of octets. This happens through the Repr family of structs and enums, e.g. ArpRepr or Ipv4Repr.

The functions in the wire module are designed for use together with -Cpanic=abort.

The Packet family of data structures guarantees that, if the Packet::check_len() method returned Ok(()), then no accessor or setter method will panic; however, the guarantee provided by Packet::check_len() may no longer hold after changing certain fields, which are listed in the documentation for the specific packet.

The Packet::new_checked method is a shorthand for a combination of Packet::new_unchecked and Packet::check_len. When parsing untrusted input, it is necessary to use Packet::new_checked(); so long as the buffer is not modified, no accessor will fail. When emitting output, though, it is incorrect to use Packet::new_checked(); the length check is likely to succeed on a zeroed buffer, but fail on a buffer filled with data from a previous packet, such as when reusing buffers, resulting in nondeterministic panics with some network devices but not others. The buffer length for emission is not calculated by the Packet layer.

In the Repr family of data structures, the Repr::parse() method never panics as long as Packet::new_checked() (or Packet::check_len()) has succeeded, and the Repr::emit() method never panics as long as the underlying buffer is exactly Repr::buffer_len() octets long.

Examples

To emit an IP packet header into an octet buffer, and then parse it back:

use smoltcp::phy::ChecksumCapabilities;
use smoltcp::wire::*;
let repr = Ipv4Repr {
    src_addr:    Ipv4Address::new(10, 0, 0, 1),
    dst_addr:    Ipv4Address::new(10, 0, 0, 2),
    next_header: IpProtocol::Tcp,
    payload_len: 10,
    hop_limit:   64,
};
let mut buffer = vec![0; repr.buffer_len() + repr.payload_len];
{ // emission
    let mut packet = Ipv4Packet::new_unchecked(&mut buffer);
    repr.emit(&mut packet, &ChecksumCapabilities::default());
}
{ // parsing
    let packet = Ipv4Packet::new_checked(&buffer)
                            .expect("truncated packet");
    let parsed = Ipv4Repr::parse(&packet, &ChecksumCapabilities::default())
                          .expect("malformed packet");
    assert_eq!(repr, parsed);
}

Re-exports

pub use self::pretty_print::PrettyPrinter;

Modules

pretty_print

Pretty-printing of packet representation.

Structs

ArpPacket

A read/write wrapper around an Address Resolution Protocol packet buffer.

DhcpOption

A representation of a single DHCP option.

DhcpOptionWriter

A buffer for DHCP options.

DhcpPacket

A read/write wrapper around a Dynamic Host Configuration Protocol packet buffer.

DhcpRepr

A high-level representation of a Dynamic Host Configuration Protocol packet.

DnsFlags

DnsPacket

A read/write wrapper around a DNS packet buffer.

DnsRepr

High-level DNS packet representation.

Error

Parsing a packet failed.

EthernetAddress

A six-octet Ethernet II address.

EthernetFrame

A read/write wrapper around an Ethernet II frame buffer.

EthernetRepr

A high-level representation of an Internet Protocol version 4 packet header.

Icmpv4Packet

A read/write wrapper around an Internet Control Message Protocol version 4 packet buffer.

IpEndpoint

An internet endpoint address.

IpListenEndpoint

An internet endpoint address for listening.

Ipv4Address

A four-octet IPv4 address.

Ipv4Cidr

A specification of an IPv4 CIDR block, containing an address and a variable-length subnet masking prefix length.

Ipv4FragKey

Ipv4Packet

A read/write wrapper around an Internet Protocol version 4 packet buffer.

Ipv4Repr

A high-level representation of an Internet Protocol version 4 packet header.

RawHardwareAddress

Unparsed hardware address.

TcpPacket

A read/write wrapper around a Transmission Control Protocol packet buffer.

TcpRepr

A high-level representation of a Transmission Control Protocol packet.

TcpSeqNumber

A TCP sequence number.

UdpPacket

A read/write wrapper around an User Datagram Protocol packet buffer.

UdpRepr

A high-level representation of an User Datagram Protocol packet.

Enums

ArpHardware

ARP hardware type.

ArpOperation

ARP operation type.

ArpRepr

A high-level representation of an Address Resolution Protocol packet.

DhcpMessageType

The possible message types of a DHCP packet.

DnsOpcode

DNS OpCodes

DnsQueryType

DNS record types

DnsRcode

DNS OpCodes

EthernetProtocol

Ethernet protocol type.

HardwareAddress

Representation of an hardware address, such as an Ethernet address or an IEEE802.15.4 address.

IcmpRepr

Icmpv4DstUnreachable

Internet protocol control message subtype for type “Destination Unreachable”.

Icmpv4Message

Internet protocol control message type.

Icmpv4ParamProblem

Internet protocol control message subtype for type “Parameter Problem”.

Icmpv4Redirect

Internet protocol control message subtype for type “Redirect Message”.

Icmpv4Repr

A high-level representation of an Internet Control Message Protocol version 4 packet header.

Icmpv4TimeExceeded

Internet protocol control message subtype for type “Time Exceeded”.

IpAddress

An internetworking address.

IpCidr

A specification of a CIDR block, containing an address and a variable-length subnet masking prefix length.

IpProtocol

IP datagram encapsulated protocol.

IpRepr

An IP packet representation.

IpVersion

Internet protocol version.

TcpControl

The possible control flags of a Transmission Control Protocol packet.

TcpOption

A representation of a single TCP option.

Constants

DHCP_CLIENT_PORT

DHCP_MAX_DNS_SERVER_COUNT

DHCP_SERVER_PORT

ETHERNET_HEADER_LEN

The Ethernet header length

IPV4_HEADER_LEN

IPV4_MIN_MTU

Minimum MTU required of all links supporting IPv4. See RFC 791 § 3.1.

MAX_HARDWARE_ADDRESS_LEN

TCP_HEADER_LEN

UDP_HEADER_LEN

Type Aliases

Result