This is a second article on using the trust-dns-resolver crate
Warning: This code is not intended to be used in production. You should review and adjust to your own needs.
First we will need to create our development environment.
cargo new trust-dns-resolver && cd $_
This will give us our standard rust directly structure. We need to add our crate to the
-snip- [dependencies] trust-dns-resolver = "0.20.1"
Next edit the
src/main.rs as follows.
Compile and run the code to make sure everything is ok.
This outputs the following
Admin: dns-admin.google.com. Admin Email: email@example.com Primary: ns1.google.com. Serial: 364996005
Explaining the code
Documentation for the SOA RData can be found here
Let’s take a look at what we are doing here.
Like the first example we create a resolver which will do the work of doing the DNS lookups.
Next we use the resolver to call
soa_lookup() and store the result into
soa_response will contain either and
SoaLookup or an
Err. For this reason we need to handle these two cases. I have changed things up a little this time and I am passing a reference to the
display_soa() function. So I am allowing
display_soa() to borrow the data. In doing this I am saving on memory and I am also promising that I am not going to mutate
soa_response within this function. I will cheat a little and
clone() some data later.
display_soa I again use
match to handle my two cases.
In the case of
Err. I do nothing and just report there were no records.
In the case of
SoaLookup, I will need to do some more processing.
- First lets make an
soa_responseand loop over it.
- In the loop we get the
rname()or the administrative contact and the
mname()or primary name server for this domain as well as
serial()and access to a few more elements.
Line 26 is just a cobbled together function to redisplay
rname() as a more valid email address which is what it really represents. If anyone can point in the direction of a better way to handle this it would greatly appreciated.
I hope you find this interesting and useful.