Parrot.Sip.Headers.MaxForwards (Parrot Platform v0.0.1-alpha.3)

Module for working with SIP Max-Forwards headers as defined in RFC 3261 Section 20.22.

The Max-Forwards header is used to limit the number of proxies or gateways that can forward a request. It consists of a single integer value that is decremented by each proxy that forwards the message.

Max-Forwards serves important purposes in SIP:

  • Preventing infinite loops in proxy networks
  • Detecting forwarding loops caused by misconfiguration
  • Limiting the request scope to a specific number of hops
  • Triggering 483 (Too Many Hops) responses when reaching zero

Each proxy MUST decrement the Max-Forwards value by one when forwarding a request. The recommended initial value is 70, as specified in RFC 3261 Section 8.1.1.6.

References:

  • RFC 3261 Section 8.1.1.6: Max-Forwards
  • RFC 3261 Section 16.6: Request Forwarding (proxy behavior)
  • RFC 3261 Section 20.22: Max-Forwards Header Field
  • RFC 3261 Section 21.4.20: 483 Too Many Hops

Summary

Functions

decrement(value)

Decrements the Max-Forwards value by 1. Returns nil if value is already 0.

default()

Creates a new Max-Forwards header with the default value of 70.

format(value)

Formats a Max-Forwards value as a string.

new(value)

Creates a new Max-Forwards header with the specified value.

parse(string)

Parses a Max-Forwards header string into an integer value.

zero?(value)

Checks if the Max-Forwards value has reached 0.

Functions

decrement(value)

@spec decrement(integer()) :: integer() | nil

Decrements the Max-Forwards value by 1. Returns nil if value is already 0.

Examples

iex> Parrot.Sip.Headers.MaxForwards.decrement(70)
69

iex> Parrot.Sip.Headers.MaxForwards.decrement(1)
0

iex> Parrot.Sip.Headers.MaxForwards.decrement(0)
nil

default()

@spec default() :: integer()

Creates a new Max-Forwards header with the default value of 70.

Examples

iex> Parrot.Sip.Headers.MaxForwards.default()
70

format(value)

@spec format(integer()) :: String.t()

Formats a Max-Forwards value as a string.

Examples

iex> Parrot.Sip.Headers.MaxForwards.format(70)
"70"

iex> Parrot.Sip.Headers.MaxForwards.format(0)
"0"

new(value)

@spec new(integer()) :: integer()

Creates a new Max-Forwards header with the specified value.

Examples

iex> Parrot.Sip.Headers.MaxForwards.new(70)
70

parse(string)

@spec parse(String.t()) :: integer()

Parses a Max-Forwards header string into an integer value.

Examples

iex> Parrot.Sip.Headers.MaxForwards.parse("70")
70

iex> Parrot.Sip.Headers.MaxForwards.parse("0")
0

zero?(value)

@spec zero?(integer()) :: boolean()

Checks if the Max-Forwards value has reached 0.

Examples

iex> Parrot.Sip.Headers.MaxForwards.zero?(0)
true

iex> Parrot.Sip.Headers.MaxForwards.zero?(1)
false