On Wed, 3 Jan 2007, Jeff Haran wrote:
> > -----Original Message-----
> > From: [EMAIL PROTECTED]
> > [mailto:[EMAIL PROTECTED] On Behalf Of Jeff Haran
> > Sent: Tuesday, January 02, 2007 5:37 PM
> > To: [email protected]
> > Subject: ESTABLISHED TCP connections missing from /proc/net/tcp
> >
> > Hi,
> >
> > I telnet to my target system running linux 2.6.14 (PowerPC 32
> > platform).
> >
> > If at that time I cat /proc/net/tcp at my serial console, I
> > see no entries for the ESTABLISHED tcp connection that telnet
> > is running
> > through:
> >
> > FD21:root> cat /proc/net/tcp
> > sl local_address rem_address st tx_queue rx_queue tr tm->when
> > retrnsmt uid timeout inode
> > 0: C0A84A66:0381 00000000:0000 0A 00000000:00000000 00:00000000
> > 00000000 0 0 814 1 c7eb1040 300 0 0 2 -1
> > 1: 7F000001:8009 00000000:0000 0A 00000000:00000000 00:00000000
> > 00000000 0 0 575 1 c7eb17c0 300 0 0 2 -1
> > 2: 00000000:006F 00000000:0000 0A 00000000:00000000 00:00000000
> > 00000000 0 0 195 1 c7eb1b80 300 0 0 2 -1
> > 3: C0A84A66:0050 00000000:0000 0A 00000000:00000000 00:00000000
> > 00000000 0 0 948 1 c7eb1400 300 0 0 2 -1
> > 4: DCDCDC02:0050 00000000:0000 0A 00000000:00000000 00:00000000
> > 00000000 0 0 949 1 c343cba0 300 0 0 2 -1
> > 5: C0A84A66:0050 C0A84A66:0471 06 00000000:00000000 03:000000BD
> > 00000000 0 0 0 2 c2fda660
> >
> > Those "0A"s under "st" are listening sockets. The "06" is an
> > old connection in time wait. But no established connections
> > are shown, which I believe should be showing up as "01"s (at
> > least they do when I do the same on the PC I have Redhat running on).
> >
> > netstat, which appears to derive its output from this proc
> > entry, thus shows no active connections:
> >
> > FD21:root> netstat -tn
> > Active Internet connections (w/o servers)
> > Proto Recv-Q Send-Q Local Address Foreign Address
> > State
> > FD21:root>
> >
> > Any ideas as to why I am not seeing established TCP
> > connections in /proc/net/tcp?
> >
>
> Hi all,
>
> Just documenting the resolution of this for posterity.
>
> It turns out that when you enable IPv6 in your kernel (like we have
> here), then established IPv4 TCP connections show up under
> /proc/net/tcp6 rather than /proc/net/tcp:
>
> FD21:root> cat /proc/net/tcp6
> sl local_address remote_address
> st tx_queue rx_queue tr tm->when retrnsmt uid timeout inode
> 0: 00000000000000000000000000000000:0016
> 00000000000000000000000000000000:0000 0A 00000000:00000000 00:00000000
> 00000000 0 0 395 1 c7f3e040 300 0 0 2 -1
> 1: 00000000000000000000000000000000:0017
> 00000000000000000000000000000000:0000 0A 00000000:00000000 00:00000000
> 00000000 0 0 212 1 c7f3f9c0 300 0 0 2 -1
> 2: 00000000000000000000FFFFC0A84A67:0017
> 00000000000000000000FFFFC0A82E67:05BB 01 00000002:00000000 01:00000024
> 00000000 0 0 1137 4 c7f3f580 37 4 1 3 100
>
> That last line represents an IPv4 telnet connection between a PC running
> XP and my target system. I've sniffed the traffic and verified that this
> TCP connection is being carried in IPv4 packets not IPv6. Seems odd that
> it shows up under /proc/net/tcp6, but once that is understood it seems
> to work reliably.
>
> Then you have to make sure you are running a version of netstat with
> IPv6 support and make sure to add the "-v" option to prevent netstat
> from truncating the IPv4 address that it will display in IPv6 form:
>
> FD21:root> netstat -t -n
> Active Internet connections (w/o servers)
> Proto Recv-Q Send-Q Local Address Foreign Address
> State
> tcp 0 208 ::ffff:192.168.74.10:23 ::ffff:192.168.46.:1467
> ESTABLISHED
> FD21:root>
>
> FD21:root> netstat -v -t -n
> Active Internet connections (w/o servers)
> Proto Recv-Q Send-Q Local Address Foreign Address
> State
> tcp 0 2 ::ffff:192.168.74.103:23 ::ffff:192.168.46.103:1467
> ESTABLISHED
> FD21:root>
>
> Thanks for the help,
>
> Jeff Haran
> Brocade Communications Systems
That seems like a bug to me. I'm running a 2.6.15-rc5 kernel and
my established TCP connections appear in /proc/net/tcp as expected.
And I do have IPv6 enabled (as a module), although I am not actually
using IPv6 for anything at the moment.
-Bill
-
To unsubscribe from this list: send the line "unsubscribe linux-net" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
