Friday, January 22, 2016

Obtaining the external WAN IP address from a Netgear WNR2000v5

Earlier I used a DNS service in order to get the IP address of my internet connection. I used some free ones, and they worked very well. Until they didn't work.

Then I used an external server, like duckduckgo.com, utilizing the computer, with python, already running in my house. Something like:

adr = "https://duckduckgo.com/?q=what+is+my+ip&ia=answer"
req = urllib2.Request(adr)
res = urllib2.urlopen(req)
data = res.read()
res.close()
...
p = re.compile('\"Answer\":"Your IP address is (\d*).(\d*).(\d*).(\d*) in')
m = p.search(data)
...
current_ip = (m.groups()[0], m.groups()[1], m.groups()[2], m.groups()[3])
...

This data were then uploaded to a know web page if it were different from the previous address.

And that worked great, until I occasionally started to use a VPN service on the machine running the script. Then duckduckgo.com returned the IP address of my VPN, which would not forward my ssh logins to my home.


So I checked my router, Netgear WNR2000v5, and it returned the IP address as expected. But only from the page "RST_conn_status.htm". It would also return "Access denied" for the first login attempt if someone had logged in to the router for another machine. And it required a username/password.

The script then became:

username='admin'
password='password'
adr = 'http://10.0.0.1/RST_conn_status.htm'
try:  #if someone else logged in to the router we get access denied the first time
 req = urllib2.Request(adr)
 base64string = base64.encodestring('%s:%s'%(username, password)).replace('\n', '')
 req.add_header("Authorization", "Basic %s" % base64string)   
 res = urllib2.urlopen(req)
except:
 time.sleep(1)
req = urllib2.Request(adr)
base64string = base64.encodestring('%s:%s' % (username, password)).replace('\n', '')
req.add_header("Authorization", "Basic %s" % base64string)   
res = urllib2.urlopen(req)
time.sleep(1)
data = res.read()
res.close()
...
p = re.compile('var info_get_wanip=\"(\d*).(\d*).(\d*).(\d*)\";')
m = p.search(data)
...
current_ip = (m.groups()[0], m.groups()[1], m.groups()[2], m.groups()[3])
...


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