Struct Replaces 

pub struct Replaces {
    pub call_id: Vec<u8>,
    pub to_tag: Vec<u8>,
    pub from_tag: Vec<u8>,
    pub early_only: bool,
}

The dialog an INVITE asks to take the place of (RFC 3891).

All three fields are load-bearing, and the two tags are the security. A Call-ID is carried in every message of a dialog and is visible to every element on the path — a proxy, a load balancer, anything that logged a header. The tags are random and known only to the two parties. Matching on the Call-ID alone would turn this header into a call-hijack primitive: anyone who had seen one message of a call could ask to be put in the middle of it.

RFC 3891 §5 says as much, and it is the reason this type has no constructor that takes fewer than three fields.

Fields

call_id: Vec<u8>

The Call-ID of the dialog to replace.

to_tag: Vec<u8>

The To tag, from the point of view of whoever built this header.

from_tag: Vec<u8>

The From tag, likewise.

early_only: bool

Whether the sender will only replace a dialog that has not been answered yet.

Implementations

impl Replaces

pub fn of(request: &Request) -> Option<Self>

Read a Replaces header out of a request.

None when there is none, and also when there is one that is unusable — a header missing either tag names no dialog, and treating it as though it named one with an empty tag is how the tags stop being a secret.

pub fn parse(value: &[u8]) -> Option<Self>

Parse a header value: call-id;to-tag=x;from-tag=y[;early-only].

pub fn matches(&self, dialog: &Dialog) -> bool

Whether this names that dialog.

The tags swap sides. A Replaces is built by the party that observed the dialog from outside it — in an attended transfer, the transferor describing its own call to the transferee — so the to-tag is the tag of the party receiving this INVITE, which is that party’s local tag. Getting the orientation wrong makes every legitimate transfer fail while leaving the hijack case wide open, because a mismatch is a mismatch either way and only the successful case would have shown it up.

pub fn to_header(&self) -> String

Render as a header value, for the INVITE that asks for the replacement.

Trait Implementations

impl Clone for Replaces

fn clone(&self) -> Replaces

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Replaces

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for Replaces

fn eq(&self, other: &Replaces) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for Replaces

impl StructuralPartialEq for Replaces