Bug #11531

IPAddr#== implements wrong logic

Added by panasyuk (Aleksander Panasyuk) over 5 years ago. Updated about 1 year ago.

Target version:



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:

return @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 = ''
ip2 = ''
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 == && @addr == other.to_i && @mask_addr == other.netmask

Updated by knu (Akinori MUSHA) over 4 years ago

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.

Updated by bjmllr (Ben Miller) over 4 years ago

it does not consider a difference in netmasks as significant isn't consistent with this principle:"") =="") # => false is valid notation for a host address, yet will drop the low-order bits to make it a valid network address:"") =="") # => true

I'm not sure why we would want to have a netmask at all if IPAddr is only for host addresses.

Updated by sahglie (Steven Hansen) over 4 years ago

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:'').to_range.to_a # => [#<IPAddr: IPv4:>]'').to_range.to_a # => [
  #<IPAddr: IPv4:>, 
  #<IPAddr: IPv4:>, 
  #<IPAddr: IPv4:│5.252>, 
  #<IPAddr: IPv4:>

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

Updated by jeremyevans0 (Jeremy Evans) over 1 year ago

I am not sure whether this is a bug. eql? considers the netmask, but == does not. So if you want to consider the netmask, you can currently use eql?. Changing == to be the same as eql? could cause backwards compatibility issues.

The major problem is one of design, in that IPAddr can operate as either a specific IP address or as a network/CIDR-block. I think it would have been better to use separate classes for those two concepts, but that is not fixable with the current design.


Updated by hsbt (Hiroshi SHIBATA) about 1 year ago

  • Assignee set to knu (Akinori MUSHA)
  • Status changed from Open to Assigned

Also available in: Atom PDF