On Wed, 3 Jan 2007, Jeff Haran wrote: > > -----Original Message----- > > From: linux-net-owner@xxxxxxxxxxxxxxx > > [mailto:linux-net-owner@xxxxxxxxxxxxxxx] On Behalf Of Jeff Haran > > Sent: Tuesday, January 02, 2007 5:37 PM > > To: linux-net@xxxxxxxxxxxxxxx > > 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 majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
