How do you do a DNS lookup, like nslookup?

pisymbol
3rd May 2006 20:40 UTC

How do you do a DNS lookup, like nslookup?
Is there a way to do this easily? I can't seem to get this to work.

pisymbol
3rd May 2006 23:02 UTC

Anyone have any clue on how to do this? I have an IP address and I want to get back the domain piece...

pisymbol
4th May 2006 00:13 UTC

It seems I want gethostbyaddress() from the ws32_32 API but I don't quite grasp the syntax of the System pluging.

It uses parameters lists to pass pack and forth between NSIS and System32 DLL variables. I appologize, I am new to the Windows world (I'm aUNIX guy).

Alright, the gethostbyaddress() from what I gather can take a string for an IP and return the DNS name (what I want). I realize it has been deprecated by gethostentry() but anyway...

Can someone give me a quick example and EXPLAIN the syntax?

Based on the doc:

System::Call 'CondMgr::CmGetHotSyncExecPath(t, *i) i(.r0, r1r1).r2'

This says CmGetHostSyncExecPath takes a pointer to a string, pointer to an int returns an int. The t is address of r0 with no input/output passing, the *i comes from r1 and whatever is returned in r1 after the call completes and the return value should be placed in r2. Right?

So by that logic for gethostbyaddress() I should have

System::Call 'ws32_32::gethostbyaddress(t) t($IPADDRESS).r5'

Pass a string which is my variable IPADDRESS and the return value (the string I presume) place it in r5. This barfs miserably. Obviously its pilot error but can I get a quick explanation? Maybe I'm looking at the wrong API doc on MSDN...

pisymbol
4th May 2006 00:16 UTC

Whooops...looks like I am looking at the wrong API doc...arrghhh..

pisymbol
4th May 2006 01:02 UTC

System::Call 'ws2_32::WSAStartup(i 514, i r2) i .r3'
# Convert IP to proper format
System::Call 'ws2_32::inet_addr(t "$IPADDRESS") l .r5'
System::Call 'ws2_32::gethostbyaddr(t r5, i 4, i 2) *i .r6'

The above crashes on the gethostbyaddr call. What am I doing wrong? I would think the pointer to the hostent structure would be returned in R6, right?

Again, any help would be much appreciated (I'm starting to get the SystemDLL plugin).

Afrow UK
4th May 2006 09:57 UTC

Where is $IPADDRESS coming from, or have you not posted all your code?

-Stu

CancerFace
4th May 2006 10:12 UTC

The first command should be

System::Call 'ws2_32::WSAStartup(i 514, *i .r2) i .r3'

(note the * and the . before r2). It is a pointer (hence the *) and you are getting it out of the function (hence the .).
Your code will give an error since the first call fails to initiallize the WS2_32 process.

I think that the 3rd call is also wrong. Maybe try to allocate the hostent structure instead of pointing $6 to it:

System::Call '*(t,t,i,i,t)i.s'
Pop $6
System::Call 'ws2_32::gethostbyaddr(t r5, i 4, i ${AF_INET}) i r6'

I am not also sure about the 't r5' on the third call. You get an unsigned long from the second call to $5 and then you place this as a 't' on the third call?

I'll try to look at this as soon as I get to work.

CF

CancerFace
4th May 2006 12:34 UTC

This code works:

!define AF_INET 2
!define strhostent '(t,t,i,i,t)i'
StrCpy $IPADDRESS "aaa.xxx.yyy.zzz" ; put your address here
System::Call 'Ws2_32::WSAStartup(i 514, *i .r2) i .r3'
System::Call 'Ws2_32::inet_addr(t "$IPADRESS") l .r5'
System::Call 'Ws2_32::gethostbyaddr(*l r5, i 4, i ${AF_INET}) i .r6'
System::Call '*$6${strhostent}(.R1,,,,)'
DetailPrint 'The full DNS name of "$IPADDRESS" is "$R1"'
System::Call 'Ws2_32::WSACleanup()i.R9'
System::Free $6

This gives you the full domain name. For example if $IPADDRESS is '205.188.229.57' $R1 will be 'waforumweb-dtc1l-0.stream.aol.com'

:)
CF

pisymbol
8th May 2006 16:33 UTC

Originally posted by CancerFace
This code works:

!define AF_INET 2
!define strhostent '(t,t,i,i,t)i'
StrCpy $IPADDRESS "aaa.xxx.yyy.zzz" ; put your address here
System::Call 'Ws2_32::WSAStartup(i 514, *i .r2) i .r3'
System::Call 'Ws2_32::inet_addr(t "$IPADRESS") l .r5'
System::Call 'Ws2_32::gethostbyaddr(*l r5, i 4, i ${AF_INET}) i .r6'
System::Call '*$6${strhostent}(.R1,,,,)'
DetailPrint 'The full DNS name of "$IPADDRESS" is "$R1"'
System::Call 'Ws2_32::WSACleanup()i.R9'
System::Free $6

This gives you the full domain name. For example if $IPADDRESS is '205.188.229.57' $R1 will be 'waforumweb-dtc1l-0.stream.aol.com'

:)
CF

Thanks dude. I'm sorry for not getting back to you, I'm on vacation!

This works for me though I had to make some changes. I was still confused about the *l r5 over the t r5 and the gethostname thread I believe is wrong since its not allocating a buffer to store the name (I had to combine the two).

Anyway, I'm starting to get a hand of the System syntax - its still awkward though!

CancerFace
8th May 2006 20:47 UTC

and the gethostname thread I believe is wrong since its not allocating a buffer to store the name (I had to combine the two).

:igor:
You lost me there ... The above code works for me for a given IP in $IPADDRESS. There is no reason to allocate space for the name as it will be allocated by the system (in $6)...

CF