Wrong NetMask shown for IP

[nsgundy]

Node: 6.9.1 network: 0.4.0

I have this situation where eth0 has two IP addresses (one assigned by DHCP and the other is a link-local address assigned by systemd-networkd), but get_interfaces_list() returns the IP of the DHCP address with the netmask of the link-local address.

{
  "name": "eth0",
  "ip_address": "192.168.2.116",
  "mac_address": "5c:f8:21:0f:40:d8",
  "gateway_ip": "192.168.2.1",
  "netmask": "255.255.0.0",
  "type": "Wired"
}

Output from os.networkInterfaces()

> os.networkInterfaces()
{ lo:
   [ { address: '127.0.0.1',
       netmask: '255.0.0.0',
       family: 'IPv4',
       mac: '00:00:00:00:00:00',
       internal: true } ],
  eth0:
   [ { address: '169.254.123.48',
       netmask: '255.255.0.0',
       family: 'IPv4',
       mac: '5c:f8:21:0f:40:d8',
       internal: false },
     { address: '192.168.2.116',
       netmask: '255.255.255.0',
       family: 'IPv4',
       mac: '5c:f8:21:0f:40:d8',
       internal: false } ] }

Output from ip -o -4 addr show eth0:

2: eth0    inet 169.254.123.48/16 brd 169.254.255.255 scope link eth0\       valid_lft forever preferred_lft forever
2: eth0    inet 192.168.2.116/24 brd 192.168.2.255 scope global dynamic eth0\       valid_lft 1803687sec preferred_lft 1803687sec

This also poses the question: How can I grab a specific IP address for an interface using network? In my application for example, I am interested in the scope global address when available, otherwise in the scope local address.

[nsgundy]

Right... I just took a look at the code and the command that is executed to grab the netmask for eth0 is the following, followed by the output

ifconfig "eth0" 2> /dev/null | egrep 'netmask|Mask:' | awk '{print $4}' | sed 's/Mask://'
255.255.0.0

Well, in this case ifconfig isn't the right thing to use as it only lists one of the two IPs and in this case its the link-local address:

ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 5C:F8:21:0F:40:D8
          inet addr:169.254.123.48  Bcast:169.254.255.255  Mask:255.255.0.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:7177 errors:0 dropped:122 overruns:0 frame:0
          TX packets:8245 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1095587 (1.0 MiB)  TX bytes:4655128 (4.4 MiB)
          Interrupt:33

Using ip -o -4 addr show eth0 might be better suited, as it outputs both IPs (see post above for output). I don't know how good / bad this is for backwards compatibility.

[tomas]

@nsgundy What's the actual output you're getting from interfaces_list(), then? Are you getting a single eth0 interface or two?

[nsgundy]

The array returned by interfaces_list() contains a single entry:

[ { name: 'eth0',
    ip_address: '192.168.2.116',
    mac_address: '5c:f8:21:0f:40:d8',
    gateway_ip: '192.168.2.1',
    netmask: '255.255.0.0',
    type: 'Wired' } ]

So far, from what I have observed, ifconfig seems to list the address that was assigned last, where as ip addr and the built in os.networkInterfaces() lists them in the order they have been added.

[tomas]

Ok, I'll take a look at this later. Thanks for the heads up!