The inet_pton() function incorrectly converts some invalid
IPv6 address strings containing the double colon characters (::).
It appears that the problematic address strings are of the
format
    x:x:x:x:x::x:x:x
with exactly eight 16-bit pieces of the address and "::".
The "::" can appear anywhere in the sequence.

When given such an address string, inet_pton() returns 1,
indicating a successful conversion.  The converted binary
address has zeros starting from the location of the "::" till
the end of the binary address.

For example, the input address string
    1:2:3::4:5:6:7:8
is converted to the binary address:
    0001:0002:0003:0000:0000:0000:0000:0000