This patch updates the DNS resolver to support IPv6 and introduces an
improved API for looking up DNS entries. This patch also adds optional
support for mDNS lookups and responses to the DNS resolver.
Here is a quick summary of the changes:
* Added support for IPv6 lookups.
* DNS queries now honor record expiration.
* Added support for mDNS, compatible with "Bonjour".
* Implemented a new lookup api, `resolv_lookup2()`, which provides
more information about the state of the record(error, expired,
looking-up, etc.).
About mDNS/Bonjour Support
--------------------------
This patch adds basic support for mDNS/Bonjour, which allows you to
refer to the name of a device instead of its IP address. This is
incredibly convenient for IPv6 addresses because they tend to be very
long and difficult to remember. It is especially important for
link-local IPv6 addresses, since not all programs support the '%'
notation for indicating a network interface (required on systems with
more than one network interface to disambiguate).
In other words, instead of typing in this:
* `http://[fe80::58dc:d7ed:a644:628f%en1]/`
You can type this instead:
* `http://contiki.local/`
Huge improvement, no?
The convenience extends beyond that: this mechanism can be used for
nodes to talk to each other based on their human-readable names instead
of their IPv6 addresses. So instead of a switch on
`aaaa::58dc:d7ed:a644:628f` triggering an actuator on
`aaaa::ed26:19c1:4bd2:f95b`, `light-switch.local` can trigger the
actuator on `living-room-lights.local`.
What you need to do to be able to look up `.local` names on your
workstation depends on a few factors:
* Your machine needs to be able to send and receive multicast packets
to and from the LoWPAN. You can do this easily with the Jackdaw
firmware on an RZUSBStick. If you have a border router, you will need
it to bridge the mDNS multicast packets across the border.
* If you are using a Mac, you win. All Apple devices support mDNS
lookups.
* If you are using Windows, you can install Apple's Bonjour for Windows
package. (This may be already installed on your machine if you have
installed iTunes) After you install this you can easily do `.local`
lookups.
* If you are using a Unix machine, you can install Avahi.
The default hostname is set to `contiki.local.`. You can change the
hostname programmatically by calling `resolv_set_hostname()`. You can
change the default hostname by changing `CONTIKI_CONF_DEFAULT_HOSTNAME`.
You may disable mDNS support by setting `RESOLV_CONF_SUPPORTS_MDNS` to
`0`.
---------------------------------
core/net/resolv: `resolv_lookup2()` -> `resolv_lookup()`
Note that this patch should fix several `resolv_lookup()` bugs
that already existed. There were many cases where `resolv_lookup()`
was being called and the IP address ignored, but later code
assumed that the IP address had been fetched... ANYWAY, those
should be fixed now.
---------------------------------
examples/udp-ipv6: Updated client to use MDNS to lookup the server.
Also updated the Cooja regression test simulation.
- Up to now the web browser used several fixed size arrays to hold the various types attribute data of the web page. This turned out to be way to inflexible for any non-trivial web page. Therefore now all attribute data is stored in a single buffer one after the other as they arrive from the parser only occupying the memory actually needed. This allows for pages with many links with rather short URLs as well as pages with few link with long URLs as well as pages with several simple forms as well as pages with one form with many form inputs.
- Using the actual web page buffer to hold the text buffers of text entry fields was in general a cool idea but in reality it is often necessary to enter text longer than the size of the text entry field. Therefore the text buffer is now stored in the new unified attribute data buffer.
- Splitting up the process of canonicalizing a link URL and actually navigating to the resulting URL allowed to get rid of the 'tmpurl' buffer used during form submit. Now the form action is canonicalized like a usual link, then the form input name/value pairs are written right into the 'url' buffer and afterwards the navigation is triggered.
- Support for the 'render states' was completely removed. The only actually supported render state was centered output. The new unified attribute buffer would have complicated enumerating all widgets added to the page in order to adjust their position. Therefore I decided to drop the whole feature as the <center> tag is barely used anymore and newer center attributes are to hard to parse.
The "normal" web is moving forward quickly reducing the interoperability of the Contiki web browser to nearly zero. The Mobile Web fits the capabilities of the Contiki web browser much better. Modern smartphones don't need the Mobile Web anymore but there are large areas in world with rather low end mobile phones and limited mobile bandwidth where the Mobile Web will be necessary for quite some time.
From that perspective it is reasonable to increase the Contiki web browser's interoperability with the Mobie Web - namely WAP 2.0 aka XHTML MP. XHTML MP is delivered as MIME types 'application/vnd.wap.xhtml+xml' or 'application/xhtml+xml'. Therefore we (try to) parse the document if the MIME type contains the substring 'html' (which is true 'text/html' too).
Unfortunately I overlooked the dynamically created textentry fields for web forms. Changing their behaviour was a little more complicated as the length of the existing text was used to determine the size of the textentry field. Now this size is passed explicitly.
