If you want to hear what we’ve got to say, but can only cope with 140 characters at a time then you can now follow us on Twitter.
We may use Twitter to give updates on service status when we’ve got problems, but the official source for such information remains our status page.
A few days ago we unveiled our IPv6 Health Check tool, and it very quickly proved its worth.
There are plenty of other IPv6 website checkers already out there that do a cursory check to make sure that you have some IPv6 addresses for your website, nameservers, and mail servers. Our checker attempts to dig a little deeper. Do your webservers actually respond over IPv6? On all addresses? Do all your MXs have working IPv6 reverse DNS? Are your DNS entries dependent on other zones that don’t have IPv6 nameservers?
One user pointed us towards the results for one of the Regional Internet Registries, initially because it broke the checker. A few bug-fixes (both in our code, and in CPAN modules) later, and we’d determined that there was a real problem behind it: www had two AAAA records, both servers were up, but only one was accepting connections on its IPv6 address. Connections to the other server eventually timed out.
Although this issue would cause real problems to an IPv6-only user, this is exactly the kind of problem that the Happy Eyeballs (aka Fast Fallback) algorithm does a perfect job of masking. If you pick the duff IPv6 server out of the DNS, it’ll almost immediately and silently fall back on an IPv4 server. Even if you use a tool like SixOrNot to show you what connection got used, it may not be obvious that something is amiss, as falling back to IPv4 becomes part of normal operation.
Even in a dual-stack world, such a problem isn’t without side effects, as it would likely lead to an imbalance in the load spread between the two web servers.
We’re continuing to broaden the range of tests performed by the tool in order to help catch the less obvious problems that can occur when IPv6-enabling your site.
Ever wondered whether users would get to your website in an IPv6-only world? Well, now you can find out. Our IPv6 Health Check tool checks not only that your web and mail servers are accessible via IPv6 addresses, but also that you can obtain those addresses from DNS using IPv6.
You can try it out by entering a domain name below:
Should you care? Well, typing domains for a few well-known websites into the checker reveals that the IPv6 Internet isn’t currently a very exciting place, so it’s going to be a little while before not having an IPv6 presence becomes a problem. On the other hand, there’s a growing number of users with both IPv4 and IPv6 connectivity, with the latter being preferred. Google recently announced that over 2% of their traffic was now over IPv61, so if you’re going to list IPv6 addresses for your servers then it’s important that they work.
1. Although you still need an IPv4 connection to find Google in the first place.
I’ve been keeping an eye on the effectiveness of the blacklist that we recently installed to block spam from Communicado Ltd.
The number of messages directed at our servers seems to vary significantly, but we’ve seen close to 1,000 in a single day rejected by the filter. Whilst not a huge number in the grand scheme of things (our servers reject several connections per second using IP blacklists), it’s a pretty significant number to be spread amongst a relatively small number of customers.
What we have noticed is that the domains that we’re now seeing have been registered increasingly recently, suggesting that the older domains are becoming unusable due to people blocking them. So, we have an arms race between our ability to keep our blacklist up to date, and their ability to keep buying and deploying domains. This is actually a good thing because the domains cost the spammers at Communicado real money, so if enough people use the blacklists and keep them up-to-date then sending spam in this way will become uneconomical. In the meantime, the only consolation of the spammers chucking all this money at Nominet, is that we occassionally get to drink it.
I did some mining of our mail logs, and identified another half dozen Communicado domains. Martin fed these into his Nominet search tool yielding another 1,000 or so domains, so we’ve now got over 5,000 on the list.
If you run a mail server and aren’t already using it, please add the blacklist to your configuration and keep it up-to-date.
We’ve just put in place a new spam blacklist. What’s unusual about this list is that it’s a list of sender domains. Filtering on sender domains is not normally something we’d consider since standard operating procedure for spammers is to use a fake sender address containing a legitimate domain.
In this case, it seems that a particular company, Communicado Ltd, has gone to the trouble of registering a very large number of UK domains specifically for the purposes of spamming. We first noticed this in response to a customer complaint last week, and the thing that got my interest was that the various different domains had valid SPF records. For example:
$ host -t txt hurvabne.co.uk hurvabne.co.uk descriptive text "v=spf1 a mx ip4:76.73.88.0/24 ip4:76.73.91.0/24 ~all"
SPF isn’t the world’s greatest anti-spam measure, but a pass on a record with specific IPs is generally a pretty positive indicator, as you have to either compromise the mail server or the DNS server – or own the domain.
What I didn’t twig was just how many domains were involved, or that they were all owned by the same company, until one of my colleagues came across Martin A. Brooks’ blog post, which identifies over 4,500 domains owned by this single outfit.
Martin has kindly shared his list of domains and we’re now filtering using it.
For what it’s worth, those domains will have cost them the best part of £17k for a year’s registration (somehow, I don’t think they’ll be renewed).
We’ve just extended our range of Virtual Servers to include a 512MB “VS Lite” option for just £7 + VAT per month – or the equivalent of £5.83/month if you pay annually.
We’ve been doing Virtual Servers for 10 years now, and we’ve always hosted them on machines with hot-swappable hardware RAID, meaning that we can replace failed disks without customers even being aware that there was a problem. One of the great things about virtualisation is that reliability shares really well – but it still adds a bit to the cost
A large proporption of our Dedicated Server customers use machines without hot-swappable drives, and we thought we’d extend the option of using cheaper hardware to our Virtual Server range in the form of the VS Lite, our most affordable Virtual Server yet.
The VS Lite host hardware still has monitored RAID, so we can cope with disk failures without data loss*, but it requires downtime in order to replace the drive.
Our standard Virtual Servers start at £12.50 + VAT per month for a 1GB server, and all run RAID-10 on hot-swappable drives, and offer a choice of data centres, allowing you to spread multiple servers across geographically diverse sites.
In the unlikely event that even £7/month sounds expensive, then we’ve got an even more affordable alternative with a bit of a twist up our sleeves which we’ll be unveiling shortly. The first person to guess what we’re planning can have one free for a year, and don’t worry, as with all our Virtual Servers you can upgrade and downgrade easily, so don’t be put off by the prospect of an even better offer in the pipeline!
On the other hand, there are no prizes for guessing what hardware we’re using for the VS Lite host servers…
Last year we announced some improvements to the Mythic Beasts DNS API, and I asserted that this made it good for implementing a Dynamic DNS service. Dynamic DNS is simply a mechanism for programmatically updating a DNS record, typically used to provide a consistent name for a computer that is at the end of an internet connection with a dynamically assigned IP address.
Well, last weekend I had the opportunity to try implementing a Dynamic DNS service with our API, and realised that it actually makes the task unduly difficult. It can be done, but in order to change a record, you need to remove the old record, and to remove the old record you need to know what it is currently. This meant that you had to use the LIST command, grep out the old record, and then issue the necessary DELETE and ADD commands. Aside from being hassle, it introduces an unavoidable race condiition between the LIST and DELETE commands.
We’ve now implemented the obvious fix: a REPLACE command, which replaces all existing records for the specified host and type, and replaces them with the one provided. Obviously this doesn’t work if for some reason you want multiple records for a single host, but for the obvious use case it means that Dynamic DNS can be handled in a single command:
curl --data "domain=MY_DOMAIN&password=MY_PASSWORD&command=REPLACE \ myhost 300 A 1.2.3.4" https://ctrlpanel.mythic-beasts.com/customer/primarydnsapi
The DNS API is a standard feature included with all Mythic Beasts domain registrations. Full documentation can be be found here.
We’ve had an IPv6 aware network for quite some time, and we’ve been gradually rolling it out to our services with the aim of eventually having every service we offer fully available over IPv6 and IPv4. We host the Raspberry Pi website which has an IPv6 only internal network, IPv6 only virtual machines and IPv4 on the front end to help out those of you with the ‘legacy’ internet.
A quick skim over the logfiles suggests that about 96% of you still access the site through the legacy IPv4 network – about 4% of hosts are now connecting over IPv6 which is starting to become a non trivial fraction of the traffic. Of course this is much higher than typical sites, Raspberry Pi users are much more technically aware than the general population.
Yesterday we had our first real connectivity problem to investigate – an end user within Ja.net (the UK academic network) was unable to access files from the Raspberry Pi download server on about half of the occasions. Further investigation showed that they could access the load balancers in our Sovereign House site with connectivity via the London Internet Exchange Juniper LAN, but not the load balancers in our Harbour Exchange site with connectivity over the London Internet Exchange Extreme LAN.
When we started investigating we confirmed that it seemed to be a problem with the Extreme LAN, if we forced the connectivity via the Juniper LAN it worked from both sites, if we forced it via the Extreme LAN it failed from both sites. Odder and odder though, a packet dump on our LINX interface didn’t show us passing the packets on.
Our IPv4 peering worked fine, this was IPv6 specific.
We then started looking at the routing table on the router. Over IPv4 it looks like
131.111.0.0/16 via 195.66.236.15 dev eth0
and over IPv6 it looks like
2001:630::/32 via fe80::5e5e:abff:fe23:2fc2 dev eth0
That gives us the netblock, and the next hop to send the packet to.
So the next step is to check you can reach the gateway happily enough.
# ping 195.66.236.15
PING 195.66.236.15 (195.66.236.15) 56(84) bytes of data.
64 bytes from 195.66.236.15: icmp_seq=1 ttl=64 time=0.220 ms
and
# ping6 fe80::5e5e:abff:fe23:2fc2
connect: Invalid argument
Odd. Then I realised that fe80:: in IPv6 means a link local address – the address is specific to the network card so to ping it you have to specify the destination address and the network interface.
# ping6 fe80::5e5e:abff:fe23:2fc2 -I eth9
PING fe80::5e5e:abff:fe23:2fc2(fe80::5e5e:abff:fe23:2fc2) from fe80::21b:21ff:fe65:a4c5 eth9: 56 data bytes
64 bytes from fe80::5e5e:abff:fe23:2fc2: icmp_seq=1 ttl=64 time=0.451 ms
Then the penny dropped. The routing table has eth0 in it but we’re actually connected to eth9. Under IPv4 this is fine because the next-hop address is globally unique and only accessible over eth9 so we send the packets out of eth9 and they go to the correct destination. Under IPv6 it’s a link local address and therefore valid over any interface, so we obey the routing table and throw the packets out of eth0 whereupon they fall onto the floor because there’s no fibre connected.
Fixing the config to put the right interface description in made it all work, and our end user is happily able to access all the load balancers on all the v6 addresses in all of the buildings.
Obviously if you’re a Mythic Beasts customer and you don’t already have an IPv6 allocation for your real or virtual server, drop us an email and we’ll hand you your own address space to play with.
So our newest Mythic Beast started working for us today. The first task is to start installing your new laptop and reading and signing employment contracts. Today we had our newest employee fail at the first hurdle.
The laptop in question is a shiny Toshiba z930. This one came with Windows 8 and a fully charged battery. On first powering it on it comes up with the Windows 8 licence. This has a tickbox option for ‘I accept the license’ and a big button labelled ‘Accept’ to click on.
If you don’t tick the box, it tells you you have to. There’s no option to reject the license.
If you press the power button the laptop suspends itself. If you press and hold the power button the laptop still suspends itself. Ctrl-Alt-Delete doesn’t work. You can’t remove the battery as it’s built in. In frustration our newest employee suggested pouring his coffee over the damn thing to make it power cycle. This was a really stupid idea, not only does the laptop have a spill proof keyboard he’d also then have no coffee.
The best plan we could come up with was to wait for the batteries to run out which requires pressing a key about every five minutes to stop the thing suspending itself.
We’ve upgraded our DNS resolvers in our SOV and HEX data centres. New features include DNSSEC validation and IPv6.
The addresses are,
SOV : 2a00:1098:0:80:1000::12 / 93.93.128.2
HEX : 2a00:1098:0:82:1000::10 / 93.93.130.2
They’re now DNSSEC aware and validating resolvers. That means if a site has correctly configured DNSSEC and we receive an answer that fails the security check we will return no answer rather than an incorrect/forged one.
To demonstrate the difference,
a non dns sec validating resolver :
# dig +short sigfail.verteiltesysteme.net
134.91.78.139
a mythic beasts server using our resolvers
# dig +short sigfail.verteiltesysteme.net
<no answer>
#
and on the DNS server it logs an error,
debug.log:28-Aug-2013 15:44:57.565 dnssec: info: validating @0x7fba880b69e0: sigfail.verteiltesysteme.net A: no valid signature found
and correctly drops the reply.
Googles DNS servers on 8.8.8.8 work the same as ours so we’re fairly confident that there will be no compatibility issues.