xinetd.d listening twice on port 69

[Paul Howarth]

Andy Green wrote:
> David Curry wrote:
> | Andy Green wrote:
> |
> |>
> |> But I am still bemused by the two listening sockets on the same port
> |> being possible.  Maybe it is some kind of cool load balancing feature I
> |> never heard of.  Can anyone else here explain how it can be?
> |>
> |> - -Andy
> |
> |
> |
> | May be this is a dumb question from a clueless neophyte, but does the
> | phenomenon constitute a security problem that needs to be addressed?
> 
> Probably not, because I'm pretty sure it will only allow it if the two
> listens are coming from inside the same process ID.
> 
> For example in one window
> 
> [root at server root]# nc -l -p 1234
> 
> works and is listening
> 
> [root at server root]# netstat -plutn | grep 1234
> tcp        0      0 0.0.0.0:1234                0.0.0.0:*
> ~    LISTEN      19055/nc
> 
> If you try to start a second nc to the same port in another window...
> 
> [root at server root]# nc -l -p 1234
> Can't grab 0.0.0.0:1234 with bind
> 
> 
> So it seems that maybe it's just a (little-known?) feature for a single
> process rather than a bug?

No, you've been setting up TCP sockets. If you do it with UDP sockets 
(nc -l -u -p 1234) you can have multiple listeners, and they don't have 
to be the same process or even started by the same user.

Paul.