Category: Uncategorized

Should anyone ask, Nokia E61s like SRV records

I was doing some work behind a broken AOL connection this weekend. The problem was that my phone on a NAT’d subnet was unable to connect out and register with my Asterisk server which sits on a public IP. I’d see it registering on the Asterisk server and the asterisk server dutifully trying to keep the NAT open with regular “Option” requests. No matter what I did, the connection didn’t stay open. Many tcpdumps later I discovered that the STUN support on the E61 is actually quite nice. On registering the phone will lookup the STUN server for the domain it’s registering to using DNS SRV records. This is cool. You can check they exist using the following command:

dig -t SRV _stun._udp.imaginator.com or,
dig -t SRV _stun._tcp.imaginator.com

If they don’t you can add them like so:

$ORIGIN imaginator.com.
_stun._udp SRV 0 0 3478 stun.ekiga.net.
_stun._tcp SRV 0 0 3478 stun.ekiga.net.

Now when my phone registers and is potentially behind a horrible NAT it can query a STUN server. In this case I’m using the ekiga stun servers. I would run my own but a stun server requires 2 public IP addresses on the same server. Something I don’t have.

Here’s the registration process now.

47454.208033 10.15.11.8 -> 88.217.199.112 DNS Standard query NAPTR imaginator.com
47454.208519 88.217.199.112 -> 10.15.11.8 DNS Standard query response
47454.218645 10.15.11.8 -> 88.217.199.112 DNS Standard query SRV _sip._udp.imaginator.com
47454.219045 88.217.199.112 -> 10.15.11.8 DNS Standard query response SRV 0 0 5060 sip.imaginator.com
47454.235146 10.15.11.8 -> 88.217.199.112 DNS Standard query A sip.imaginator.com
47454.235440 88.217.199.112 -> 10.15.11.8 DNS Standard query response CNAME bunker.imaginator.com A 88.217.199.112
47454.241153 10.15.11.8 -> 88.217.199.112 DNS Standard query AAAA sip.imaginator.com
47454.241550 88.217.199.112 -> 10.15.11.8 DNS Standard query response CNAME bunker.imaginator.com
47454.283984 10.15.11.8 -> 88.217.199.112 DNS Standard query SRV _stun._tcp.imaginator.com
47454.284320 88.217.199.112 -> 10.15.11.8 DNS Standard query response SRV 0 0 3478 stun.ekiga.net
47454.298726 10.15.11.8 -> 88.217.199.112 DNS Standard query A stun.ekiga.net
47454.348053 88.217.199.112 -> 10.15.11.8 DNS Standard query response CNAME stun.buildserver.net A 194.39.182.241
47454.354068 10.15.11.8 -> 88.217.199.112 DNS Standard query AAAA stun.ekiga.net
47455.422987 88.217.199.112 -> 10.15.11.8 DNS Standard query response CNAME stun.buildserver.net
47455.468823 10.15.11.8 -> 88.217.199.112 DNS Standard query AAAA stun.ekiga.net
47455.469167 88.217.199.112 -> 10.15.11.8 DNS Standard query response CNAME stun.buildserver.net
47455.507036 10.15.11.8 -> 88.217.199.112 DNS Standard query SRV _stun._udp.imaginator.com
47455.508302 88.217.199.112 -> 10.15.11.8 DNS Standard query response SRV 0 0 3478 stun.ekiga.net

Look at that STUN goodness happening! Not sure that this will help my AOL problem but, the E-series SIP clients need all the help they can get.

For completeness here’s a packet dump of port 5060 and the registration process (sinkhole.imagilan being the E61 phone):

sudo tcpdump -i vlan4 port 5060
tcpump: verbose output suppressed, use -v or -vv for full protocol decode
listening on vlan4, link-type EN10MB (Ethernet), capture size 96 bytes
10:15:15.756401 IP bunker.imaginator.com.sip > sinkhole.imagilan.sip: SIP, length: 479
10:15:16.755989 IP bunker.imaginator.com.sip > sinkhole.imagilan.sip: SIP, length: 479
10:15:16.971890 IP sinkhole.imagilan.sip > 194.39.182.241.3478: SIP, length: 20
10:15:17.003216 IP 194.39.182.241.3478 > sinkhole.imagilan.sip: SIP, length: 88
10:15:17.010745 IP sinkhole.imagilan.sip > bunker.imaginator.com.sip: SIP, length: 324
10:15:17.026108 IP sinkhole.imagilan.sip > bunker.imaginator.com.sip: SIP, length: 448
10:15:17.026289 IP bunker.imaginator.com.sip > sinkhole.imagilan.sip: SIP, length: 422
10:15:17.026375 IP bunker.imaginator.com.sip > sinkhole.imagilan.sip: SIP, length: 484
10:15:17.190018 IP sinkhole.imagilan.sip > bunker.imaginator.com.sip: SIP, length: 603
10:15:17.190263 IP bunker.imaginator.com.sip > sinkhole.imagilan.sip: SIP, length: 422
10:15:17.269910 IP bunker.imaginator.com.sip > sinkhole.imagilan.sip: SIP, length: 503
10:15:27.010448 IP bunker.imaginator.com.sip > sinkhole.imagilan.sip: SIP, length: 497
10:15:27.148699 IP sinkhole.imagilan.sip > bunker.imaginator.com.sip: SIP, length: 328
10:15:28.149370 IP bunker.imaginator.com.sip > sinkhole.imagilan.sip: SIP, length: 561
10:15:28.272179 IP sinkhole.imagilan.sip > bunker.imaginator.com.sip: SIP, length: 336
10:15:58.978251 IP sinkhole.imagilan.sip > bunker.imaginator.com.sip: SIP, length: 4
10:15:58.978997 IP sinkhole.imagilan.sip > 194.39.182.241.3478: SIP, length: 20
10:15:59.011163 IP 194.39.182.241.3478 > sinkhole.imagilan.sip: SIP, length: 88
10:16:27.148729 IP bunker.imaginator.com.sip > sinkhole.imagilan.sip: SIP, length: 497

That final packet coming back is the SIP option command that Asterisk sends out to keep the connection alive.

Here’s a diagram of the STUN process.

Should anyone ask, carpets aid terrorism

What have we learnt from the recent terrorism threats. Well, other than they piss everyone off and show that the terrorists have won.

I’ve discovered that McGyver was right all along and that I could make a bomb by mixing 2 parts toothpaste with three parts aftershave, using a catalyst of lipstick, I can create an explosive that will explode with enough force to rupture the hull of an aeroplane built to survive some pretty intense forces. But: if it’s put in a clear bag then we’re safe or if you buy it after the security check in duty free, then then the toothpaste manufacturer has reduced the level of nitrogen in toothpaste and the possibility of the above recipe working is significantly reduced. Although it’s good to see that some are doing their bit for security by abandoning the use of toothpaste altogether.

I’ve also learnt that if I do need to blow up an aeroplane and don’t mind going down with it then I should just check the bomb in since this luggage is not xray’d.

And I’ve learnt that 2 parts fear with 3 parts of human irrationality, with a catalyst of the fear of flight, are enough for politicians to implement these security “checks” in our name. Yes, I’m referring to the “I’ll take your pocket knife but give you a metal steak knife on board brigade”. Honestly, when are the public going to tell the emperor that he has no clothes on?

What else have I learned this weekend? Well, the Scots should definitely be in the Union if only because they share the British love of carpet. For those that don’t understand carpet, I’ll clarify: It’s a covering that the British love to put on perfectly good floors. It’s good at retaining dust and any gum that may drop on it and allows you to see where people walk by wearing out heavily on heavily used areas. It’s also everywhere. From the moment you step off an aeroplane onto the trademark BAA mottled grey black to the pubs with their “once was red but is now dark red and flecked with chewing gum” patterning (and who knows what other fluids). While the rest of the world has never had more than a removable rug, the Brits have gone all out for covering a perfectly good hardwood floor with something that is difficult to clean and provides a lovely environment for all sorts of mites to live in.

So I urge my lone reader, go to the polls when Gordon decrees and vote out this government, their security checks from the land of carpet. For the rest of you, I urge you to short the stocks of the British Carpet Manufacturing Association members. Enough is enough.

Have I mentioned church bells yet?

Should anyone ask, carpets aid terrorism

What have we learnt from the recent terrorism threats. Well, other than they piss everyone off and show that the terrorists have won.

I’ve discovered that McGyver was right all along and that I could make a bomb by mixing 2 parts toothpaste with three parts aftershave, using a catalyst of lipstick, I can create an explosive that will explode with enough force to rupture the hull of an aeroplane built to survive some

pretty intense forces. But: if it’s put in a clear bag then we’re safe or if you buy it after the security check in duty free, then then the toothpaste manufacturer has reduced the level of nitrogen in toothpaste and the possibility of the above recipe working is significantly reduced. Although it’s good to see that some are doing their bit for security by abandoning the use of toothpaste altogether.

I’ve also learnt that if I do need to blow up an aeroplane and don’t mind going down with it then I should just check the bomb in since this luggage is not xray’d.

And I’ve learnt that 2 parts fear with 3 parts of human irrationality, with a catalyst of the fear of flight, are enough for politicians to implement these security “checks” in our name. Yes, I’m referring to the “I’ll take your pocket knife but give you a metal steak knife on board brigade”. Honestly, when are the public going to tell the emperor that he has no clothes on?

What else have I learned this weekend? Well, the Scots should definitely be in the Union if only because they share the British love of carpet. For those that don’t understand carpet, I’ll clarify: It’s a covering that the British love to put on perfectly good floors. It’s good at retaining dust and any gum that may drop on it and allows you to see where people walk by wearing out heavily on heavily used areas. It’s also everywhere. From the moment you step off an aeroplane onto the trademark BAA mottled grey black to the pubs with their “once was red but is now dark red and flecked with chewing gum” patterning (and who knows what other fluids). While the rest of the world has never had more than a removable rug, the Brits have gone all out for covering a perfectly good hardwood floor with something that is difficult to clean and provides a lovely environment for all sorts of mites to live in.

So I urge my lone reader, go to the polls when Gordon decrees and vote out this government, their security checks from the land of carpet. For the rest of you, I urge you to short the stocks of the British Carpet Manufacturing Association members. Enough is enough.

Have I mentioned church bells yet?

Should anyone ask, my cats domesticated themselves

Interesting Smithsonian Article:A Brief History of House Cats

When humans were predominantly hunters, dogs were of great use, and thus were domesticated long before cats. Cats, on the other hand, only became useful to people when we began to settle down, till the earth and—crucially—store surplus crops. With grain stores came mice, and when the first wild cats wandered into town, the stage was set for what the Science study authors call “one of the more successful ‘biological experiments’ ever undertaken.” The cats were delighted by the abundance of prey in the storehouses; people were delighted by the pest control.

“We think what happened is that the cats sort of domesticated themselves,” Carlos Driscoll, one of the study authors, told the Washington Post. The cats invited themselves in, and over time, as people favored cats with more docile traits, certain cats adapted to this new environment, producing the dozens of breeds of house cats known today. In the United States, cats are the most popular house pet, with 90 million domesticated cats slinking around 34 percent of U.S. homes.

Should anyone ask, my cats domesticated themselves

Interesting Smithsonian Article:A Brief History of House Cats

When humans were predominantly hunters, dogs were of great use, and thus were domesticated long before cats. Cats, on the other hand, only became useful to people when we began to settle down, till the earth and—crucially—store surplus crops. With grain stores came mice, and when the first wild cats wandered into town, the stage was set for what the Science study authors call “one of the more successful ‘biological experiments’ ever undertaken.” The cats were delighted by the abundance of prey in the storehouses; people were delighted by the pest control.

“We think what happened is that the cats sort of domesticated themselves,” Carlos Driscoll, one of the study authors, told the Washington Post. The cats invited themselves in, and over time, as people favored cats with more docile traits, certain cats adapted to this new environment, producing the dozens of breeds of house cats known today. In the United States, cats are the most popular house pet, with 90 million domesticated cats slinking around 34 percent of U.S. homes.