Nmap Development: Re: WARNING: Unable to find appropriate interface for system route to ...

[kx <kxmail () gmail com>]

Thanks clozapina! You are a fricking hero.  I however, am an nmap
n00b. 3.84 was the first version to include dnet and the whole rework
of that infrastructure. I should have known better.

Looking back at 3.81, it appears as though the routethrough function
in tcpip.cc was responsible for some of the same work that route_dst
does now. Not sure if we need to add some logic back in from that, but
let me ramble some more.

A question I have, could someone send me the output when they specify
the -e output? I could use that error message if any.

Again, I don't have a *BSD box, but here is my take at what is going on:

Getting the routes from Linux-style /proc/net/route isn't working. So
nmap tries to get the routes with dnet via, collect_dnet_routes(),
which is the call that produces the error("WARNING: Unable to find
appropriate interface for system route to %s\n",
addr_ntoa(&entry->route_gw)); I was focusing on the "nexthost" error
in earlier emails, which is a result of this.

The good news, is that nmap knows what gateway to use, but it can't
determine the interface to fill in the route table.

This the code in collect_dnet_routes that is failing, probably due to
failure to match the mask bits and then nmap thinks we aren't on the
same subnet? I am not familiar with ppp, pppoe, or tun interfaces. Is
the default mask not /0? If anyone could take a look at the values in
this loop, it would help for sure.

  /* Now determine which interface the route relates to */
  u32 mask;
  struct sockaddr_in *sin;
  for(i = 0; i < dcrn->numifaces; i++) {
    sin = (struct sockaddr_in *) &dcrn->ifaces[i].addr;
    mask = htonl((unsigned long) (0-1) << (32 - dcrn->ifaces[i].netmask_bits));
    if ((sin->sin_addr.s_addr & mask) == (entry->route_gw.addr_ip & mask)) {
      dcrn->routes[dcrn->numroutes].device = &dcrn->ifaces[i];
      break;
    }
  }

Last if not least, it is a hack, but we could consider adding a
--next_hop option to force a next hop, and it would complete the -e
and -S options we have now.

Cheers,
  kx



On 4/18/06, clozapina <clozapina () gmail com> wrote:
> Ciao hx,
>
> here your request, starting from the end ;-):
>
>
> 3.81 configure and make: work
> 3.84alfa1 configure and make: don't work
> 3.84alfa2 configure and make: don't work
> 3.90  configure and make: don't work
> 4.01 configure and make: don't work
> 4.02alfa2  configure and make: don't work
>
> ifconfig -a
> lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
>         inet 127.0.0.1 netmask 0xff000000
>         inet6 ::1 prefixlen 128
>         inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1
> gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
> stf0: flags=0<> mtu 1280
> en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>         ether 00:0a:95:xx:xx:xx
>         media: autoselect (none) status: inactive
>         supported media: none autoselect 10baseT/UTP <half-duplex>
> 10baseT/UTP <full-duplex> 10baseT/UTP <full-duplex,hw-loopback>
> 100baseTX <half-duplex> 100baseTX <full-duplex> 100baseTX <full-
> duplex,hw-loopback>
> en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>         ether 00:0d:93:xx:xx:xx
>         media: autoselect (<unknown type>) status: inactive
>         supported media: autoselect
> fw0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 2030
>         lladdr 00:0a:95:xx:xx:xx:xx:xx
>         media: autoselect <full-duplex> status: inactive
>         supported media: autoselect <full-duplex>
> ppp0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1500
>         inet 217.201.16.30 --> 217.200.178.19 netmask 0xffffff00
>
> ./nmap --iflist
>
> Starting Nmap 4.01 ( http://www.insecure.org/nmap/ ) at 2006-04-18
> 18:38 CEST
> ************************INTERFACES************************
> DEV  (SHORT) IP/MASK          TYPE        UP MAC
> lo0  (lo0)   127.0.0.1/8      loopback    up
> ppp0 (ppp0)  217.201.28.62/24 point2point up
>
> WARNING: Unable to find appropriate interface for system route to
> 217.200.178.19
>
> WARNING: Unable to find appropriate interface for system route to
> 217.200.178.19
>
> WARNING: Unable to find appropriate interface for system route to
> 217.200.178.19
>
> **************************ROUTES**************************
> DST/MASK          DEV  GATEWAY
> 127.0.0.1/32      lo0  127.0.0.1
> 217.200.178.19/32 ppp0 217.201.28.62
> 127.0.0.0/8       lo0  127.0.0.1
>
> ask me for more info.
> thks
> bye
>
>
> On 18/apr/06, at 14:13, kx wrote:
>
> > Bottom line, something in nmap or dnet is having difficulty getting
> > system routes, and it appears to be most common on *BSD kernels on
> > non-ethernet adapters.
> >
> > Gianluigi, can you please send the output of "nmap --iflist" from
> > nmap 4.01?
> >
> > Can you also please send the output of your "ifconfig -a" on OS X?
> >
> > And last but not least, would you be willing to try working your way
> > up from nmap 3.81 to 4.01 and let us know what is the first version of
> > nmap that breaks?  I know that is asking a lot, but it would be the
> > most valuable. Old distributions can be found here:
> > http://www.insecure.org/nmap/dist/
> >
> > Thanks again,
> >   kx
> >
> > On 4/17/06, gianluigi angotti <clozapina () gmail com> wrote:
> > > Hi,
> > > this is only a note; i know that this problem is known.
> > > I try to use nmap on a ppp via gprs connection and the result is
> > > WARNING: Unable to find appropriate interface for system route to ...
> > > At this moment i don't have experience on a different connection.
> > > I compile nmap 4.01 on Mac OSX 10.4.6.
> > > libdnet is 1.10
> > > I use without problem 3.81.
> > > bye
> > >
> > >
> > >
> > >
> > > _______________________________________________
> > > Sent through the nmap-dev mailing list
> > > http://cgi.insecure.org/mailman/listinfo/nmap-dev

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