nmbd using the wrong source address upon sending Node Status requests

Kashif Shaikh kshaikh at consensys.com
Thu Apr 24 18:01:09 GMT 2003

Christopher R. Hertel wrote:
> On Thu, Apr 24, 2003 at 06:00:50PM +0200, Volker Lendecke wrote:
>>Hash: SHA1
>>Being a LMB nmbd has to send out a node status request to the DMB to
>>find its real name to send as called name. This is done from the wrong
>>source ip address if we use 'bind interfaces only = yes' to a virtual
>>interface. This is needed if you want to run several LMBs on a machine
>>or in a cluster environment.
>>The node status request goes out with the main interface's IP address
>>as the socket used to send the UDP packet is bound to and nmbd
>>will not receive this. I have not really followed why we ignore the
>>I can supply logs, sniffs & confs upon request.
>>I have a little proof of concept patch that revives the socket address
>>parameter for this purpose:
>>Index: source/nmbd/nmbd.c
>>RCS file: /space/vl/cvstree/samba/source/nmbd/nmbd.c,v
>>retrieving revision
>>diff -u -r1.105.2.21 nmbd.c
>>- --- source/nmbd/nmbd.c	30 Mar 2003 23:04:17 -0000
>>+++ source/nmbd/nmbd.c	24 Apr 2003 15:20:55 -0000
>>@@ -532,7 +532,7 @@
>>    */
>>   if ( isdaemon )
>>- -    ClientNMB = open_socket_in(SOCK_DGRAM, port,0,0,True);
>>+    ClientNMB = open_socket_in(SOCK_DGRAM, port,0,interpret_addr(lp_socket_address()),True);
>>   else
>>     ClientNMB = 0;
>>There was some discussion on irc that this might be not the right
>>solution as 'socket address' is now deprecated. But what is the right
>>one to this rather obvious bug? This *definitely* needs fixing. Why is
>>'socket address' deprecated in the first place?
> As Volker says, the problem is that we send the NBT Node Status query from 
>  The outbound packet is then assigned the address of the 
> interface from which it is actually sent (which depends upon the routing).
> So, by sending from, the source address may be one to which Samba
> is not bound.  As a result we are, essentially, spoofing the packet.  The
> reply will then arrive on an interface to which Samba is not bound and
> will, therefore, be ignored (we probably don't even put it into
> unexpected.tdb).
> Volker's solution is to use the "socket address" parameter, and bind the 
> outbound socket to the interface specified by the "socket address".  Doing 
> this proves that he's got the right diagnosis.  I think, though, that the 
> better solution might be to choose the first address in the "interfaces" 
> list, if such is defined (if not, using will be okay).
> Using the first "interfaces" entry means that "socket address" can remain 
> depricated, and it also means that the sysadmin doesn't have to think 
> about configuring the "socket address" parameter.
> I also thought about running through the list of interfaces to see if one 
> of them was on the same subnet as the destination address.  Volker pointed 
> out, however, that in the case he's dealing with the Node Status is being 
> sent to a node on a separate network.  We would wind up needing to dig 
> into the routing table to find useful information.  Ick.  Probably not a 
> good idea...
> Chris -)-----

However, if you provide a ip address, i.e."interfaces =" in the smb.conf file, nmbd will setup a total of *4* sockets 
across the and interfaces.

Therefore instead of nmbd not opening the socket, what it should 
do is use the proper socket it has already setup, no?


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