Struct Fingerprint 

pub struct Fingerprint;

The FINGERPRINT attribute MAY be present in all STUN messages.

The value of the attribute is computed as the CRC-32 of the STUN message up to (but excluding) the FINGERPRINT attribute itself, XOR’ed with the 32-bit value 0x5354554e. (The XOR operation ensures that the FINGERPRINT test will not report a false positive on a packet containing a CRC-32 generated by an application protocol.)

The 32-bit CRC is the one defined in ITU V.42, which has a generator polynomial of x^32 + x^26 + x^23 + x^22 + x^16 + x^12 + x^11 + x^10 + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1. See the sample code for the CRC-32 in Section 8 of RFC1952.

When present, the FINGERPRINT attribute MUST be the last attribute in the message and thus will appear after MESSAGE-INTEGRITY and MESSAGE- INTEGRITY-SHA256.

The FINGERPRINT attribute can aid in distinguishing STUN packets from packets of other protocols. See Section 7.

As with MESSAGE-INTEGRITY and MESSAGE-INTEGRITY-SHA256, the CRC used in the FINGERPRINT attribute covers the Length field from the STUN message header. Therefore, prior to computation of the CRC, this value must be correct and include the CRC attribute as part of the message length. When using the FINGERPRINT attribute in a message, the attribute is first placed into the message with a dummy value; then, the CRC is computed, and the value of the attribute is updated. If the MESSAGE-INTEGRITY or MESSAGE-INTEGRITY-SHA256 attribute is also present, then it must be present with the correct message- integrity value before the CRC is computed, since the CRC is done over the value of the MESSAGE-INTEGRITY and MESSAGE-INTEGRITY-SHA256 attributes as well.

Trait Implementations

impl<'a> Attribute<'a> for Fingerprint

const KIND: AttrKind = AttrKind::Fingerprint

current attribute type.

type Error = StunError

type Item = u32

current attribute inner type.

fn encode(value: Self::Item, bytes: &mut BytesMut, _: &'a [u8])

write the current attribute to the bytesfer.

fn decode(bytes: &'a [u8], _: &'a [u8]) -> Result<Self::Item, Self::Error>

convert bytesfer to current attribute.