[ruby-core:78278] [Ruby trunk Bug#11531] IPAddr#== implements wrong logic

[runner@berkeley.edu]

Issue #11531 has been updated by Steven Hansen.


Akinori MUSHA wrote:
> I think this is intentional.  IPAddr represents an IP address, not an IP network, so it does not consider a difference in netmasks as significant.

I disagree that IPAddr represents an IP address (I think a more accurately represents a CIDR block).  To add to Ben's point:

`
IPAddr.new('128.128.128.128').to_range.to_a # => [#<IPAddr: IPv4:128.128.128.128/255.255.255.255>]
`

`
IPAddr.new('128.128.128.128/30').to_range.to_a # => [#<IPAddr: IPv4:128.128.128.128/255.255.255.252>, #<IPAddr: IPv4:128.128.128.129/255.255.255.252>, #<IPAddr: IPv4:128.128.128.130/255.255.25│
5.252>, #<IPAddr: IPv4:128.128.128.131/255.255.255.252>]
`

The fact that IPAddr accepts a CIDR block mean it represents 1 or more IPs.  So an IPAddr with 1 IP should not be equal to an IPAddr with 4 IPs

----------------------------------------
Bug #11531: IPAddr#== implements wrong logic
https://bugs.ruby-lang.org/issues/11531#change-61645

* Author: Aleksander Panasyuk
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: 2.1.5p273
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
----------------------------------------
# Description
IPAddr#== should implement the logic of comparison of two IPAddr instances. This generally means that it compares two IP addresses.
Lets look at the code of this method:

https://github.com/ruby/ruby/blob/c8b3f1b470e343e7408ab5883f046b1056d94ccc/lib/ipaddr.rb#L151

`return @family == other.family && @addr == other.to_i`

It returns the result of comparison of the families and the addresses, but it should also compare the netmask which describes the network where this address is located.
The code below shows the test case for this comparison:
`
ip1 = IPAddr.new '195.51.100.0/24'
ip2 = IPAddr.new '195.51.100.0/26'
ip1 == ip2 #=> true
`
This code shows that two identical IP addresses from different networks are equal. But the result should be `false` because these addresses are not identical.

# Possible solution
Depending on Feature #11210 i would propose following implementation of this method:
`
def ==(other)
  other = coerce_other(other)
  return @family == other.family && @addr == other.to_i && @mask_addr == other.netmask
end
`



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