Fix decoding inet with netmask

[leah-u]

I got the following error when trying to select an inet value with a netmask other than 32:

1> pgo:query("SELECT '192.168.0.1/24'::inet").
** exception error: no function clause matching 
                    pg_inet:decode(<<2,24,0,4,192,168,0,1>>,
                                   ...

It looks like pg_inet:decode currently matches on the third byte depending on the netmask value. This byte however is a flag indicating whether the type is inet or cidr¹. Unless we want to return this type information, it should just be ignored.

I also changed the encoding for consistency, the is_cidr flag is ignored by postgres².

Footnotes

1. https://github.com/postgres/postgres/blob/e849bd551c323a384f2b14d20a1b7bfaa6127ed7/src/backend/utils/adt/network.c#L278 ↩

2. https://github.com/postgres/postgres/blob/e849bd551c323a384f2b14d20a1b7bfaa6127ed7/src/backend/utils/adt/network.c#L217 ↩

[tsloughter]

Thanks! I'm guessing we should include that type information somehow, but for now we can do this as any other change would be backwards incompatible.

[tsloughter]

Looks like the prop test for cidr broke.

[leah-u]

I changed my solution to just add decoding for inet values with a netmask.

[tsloughter]

How is this different from what is already there

pg_types/src/pg_inet.erl

Lines 35 to 38 in 5cf6552

	decode(<<?INET, Mask:8, 1, ?IP_SIZE, Bin/binary>>, _) ->
	{list_to_tuple(binary_to_list(Bin)), Mask};
	decode(<<?INET6, Mask:8, 1, ?IP6_SIZE, Bin/binary>>, _) ->
	{list_to_tuple([X || <<X:16>> <= Bin]), Mask};

[tsloughter]

Sorry about that! Merging now.