This is a sample ip addr command output on linux:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
     inet 127.0.0.1/8 scope host lo
     inet6 ::1/128 scope host
        valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
state UP qlen 1000
     link/ether 08:00:27:fc:25:9f brd ff:ff:ff:ff:ff:ff
     inet 192.168.1.4/24 brd 192.168.1.255 scope global eth0
     inet6 fe80::a00:27ff:fefc:259f/64 scope link
        valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
state UP qlen 1000
     link/ether 08:00:27:b1:42:d0 brd ff:ff:ff:ff:ff:ff
     inet 192.168.240.1/24 brd 192.168.240.255 scope global eth1
     inet 192.168.241.1/24 brd 192.168.241.255 scope global eth1
     inet 192.168.239.1/24 brd 192.168.239.255 scope global eth1
     inet 10.0.0.1/22 brd 10.0.3.255 scope global eth1
     inet6 fe80::a00:27ff:feb1:42d0/64 scope link
        valid_lft forever preferred_lft forever

This is the output of a test java program that uses
the java.net.NetworkInterface class to display all IP addresses and their
corresponding settings:

eth1:10.0.0.1/24 broadcast:192.168.240.255
eth1:192.168.239.1/24 broadcast:192.168.240.255
eth1:192.168.241.1/24 broadcast:192.168.240.255
eth1:192.168.240.1/24 broadcast:192.168.240.255
eth0:192.168.1.4/24 broadcast:192.168.1.255
lo:127.0.0.1/8

As you can see there are 2 problems visible here:

1. On all eth1 lines same broadcast is displayed. The value is the
broadcast of the first IP address set on that interface

2. All addresses are with prefix length of 24 which is not correct. We
have 10.0.0.1/22 in the "ip addr" output.

So the problem is in NetworkInterfaces native code for Unix.

For IPv4 addresses that code uses 2 functions (getBordacast and
getSubnet and these 2 functions use ioctl with SIOCGIFNETMASK and
SIOCGIFBRDADDR. Both of these requests receive as parameter interface
name. They are not prepared to work in environments where you can
specify more then one IP on the same interface without using virtual
interfaces.

The proposal is to read ip address information for interfaces with getifaddrs. getifaddrs knows how to handle this case properly. It returns all the necessary information in an array of "struct ifaddrs"