> -----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 - 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
