topic Re: Emulate parts of netstat functionality through socket hack in Operating System - HP-UX

Emulate parts of netstat functionality through socket hack

Ralph Grothe — Mon, 01 Oct 2001 08:58:03 GMT

Hi system hackers / networkers,

I couldn't quite make up my mind which would be the appropriate section for this posting (either Languages or Networking).
Indeed, this isn't anything especially HP-UX specific, but rather common Unix BSD Socket fair.
But I'm sure there are many experienced system hackers among you sysadmins.
I wish to write a wee prog / script which stats sockets of AF_INET *without* falling back to a system call to netstat.
I would want to do this in Perl with the Socket module, or the more comfortable OO module IO::Socket (which inherits from IO::Handle).
I know that the system calls of the socket library are 1:1 adaptations to Perl so any suggestions in C would also be very welcome.
Having read quite a bit about socket programming in Perl I now would know how to open a socket, bind it to a port, put it into listening mode, and make it accept connections.
Even how to trap dreaded PIPE signals, use syslog, change euid, chroot, disociate from the terminal, auto-background and serve clients, preforking, multiplexing, or simple forking.
I also read how to write clients that connect to a server.
What I didn't find though, was how to simply stat already established (or listening) sockets, say to simply count the number of connectios to a certain port.
As a last resort I think I could get the sources of a GNU netstat, and try to understand how they did it.
But I thought that maybe some of you also know, and could give me a little hint.

Many thanks
Ralph

Re: Emulate parts of netstat functionality through socket hack

Vincent Fleming — Tue, 02 Oct 2001 17:00:10 GMT

There's about 7000 lines of C code in netstat on my FreeBSD system. You can get the code at www.freebsd.org - I'm sure it's in there somewhere.

I think this is what you're looking for:
struct ngpcb *this, *next;
struct ngpcb ngpcb;
struct ngsock info;
struct socket sockb;
/* Read in socket structure */
kread((u_long)ngpcb.ng_socket, (char *)&sockb, sizeof(sockb));

Re: Emulate parts of netstat functionality through socket hack

Ralph Grothe — Thu, 04 Oct 2001 09:34:54 GMT

Hi Vincent,

thanks for looking at netstat's sources.

I would have done this with my Linux distro's netstat as well.

Blimy, 7000 lines of code?

That's what I sort of feared, and why I posted here.

Unfortunately it looks as there aren't many HP-UX admin folks interested in this stuff, gathering from the overwhelming response to this post :-(