Ftp hangs after some transferts

Ftp hangs after some transferts

[Emmanuel Lacour]

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Hi, 

Maybe it's not a netfilter problem, but I know that people on this list
is ftp/firewall/network aware.

Here is my pbm.

Active connections from workstation/FW to ftpserver2 hangs after some
files have been transfered.

                     
		     ------------------ ftpserver1
                     | 
                     |
		     |
ftpserver2-------Internet
                     |
		     |
		     |
		FW netfilter
		     |
		     |
		     -----------workstation
		    


If somone know a similar problem or has any idea...


Some test:

In ftp passive mode: all is ok

In ftp active mode:

workstation->ftpserver2: Hang after some files are transfered

workstation->ftpserver1: OK

ftpserver1->ftpserver2: OK

FW->ftpserver2: Hang after some files are transfered
(iptables unloaded for this test)



Configs:

ftpserver2: debian potato with proftpd
ftpserver1: debian woody with proftpd (pre-nated with a
potato+netfilter+kernel-2.4.18 box)
FW: debian potato with netfilter (kernel 2.4.18)



Here is the end of tcpdump on FW external iface just before it hangs:


workstation.3006 > ftpserver2.ftp: P 790:811(21) ack 1522 win 16060 <nop,nop,timestamp 451190278 1158115672> (DF)
ftpserver2.ftp > workstation.3006: P 1522:1542(20) ack 811 win 16060 <nop,nop,timestamp 1158115673 451190278> (DF)
workstation.3006 > ftpserver2.ftp: P 811:837(26) ack 1542 win 16060 <nop,nop,timestamp 451190280 1158115673> (DF)
ftpserver2.ftp > workstation.3006: P 1542:1572(30) ack 837 win 16060 <nop,nop,timestamp 1158115675 451190280> (DF)
workstation.3006 > ftpserver2.ftp: P 837:858(21) ack 1572 win 16060 <nop,nop,timestamp 451190281 1158115675> (DF)
ftpserver2.ftp-data > workstation.3015: S 1214809980:1214809980(0) win 16060 <mss 1460,sackOK,timestamp 1158115676 0,nop,wscale 0> (DF)
workstation.3015 > ftpserver2.ftp-data: S 1558404700:1558404700(0) ack 1214809981 win 16060 <mss 1460,sackOK,timestamp 451190283 1158115676,nop,wscale 0> (DF)
ftpserver2.ftp > workstation.3006: . ack 858 win 16060 <nop,nop,timestamp 1158115678 451190281> (DF)
ftpserver2.ftp > workstation.3006: P 1572:1633(61) ack 858 win 16060 <nop,nop,timestamp 1158115678 451190281> (DF)
workstation.3006 > ftpserver2.ftp: . ack 1633 win 16060 <nop,nop,timestamp 451190286 1158115678> (DF)
ftpserver2.ftp-data > workstation.3009: F 1:1(0) ack 30805 win 15928 <nop,nop,timestamp 1158115758 451190061> (DF)
workstation.3009 > ftpserver2.ftp-data: . ack 2 win 16060 <nop,nop,timestamp 451190364 1158115758> (DF)
ftpserver2.ftp-data > workstation.3011: F 1:1(0) ack 24799 win 15928 <nop,nop,timestamp 1158115879 451190179> (DF)
workstation.3011 > ftpserver2.ftp-data: . ack 2 win 16060 <nop,nop,timestamp 451190485 1158115879> (DF)
ftpserver2.ftp-data > workstation.3012: F 1:1(0) ack 60672 win 15928 <nop,nop,timestamp 1158115922 451190220> (DF)
workstation.3012 > ftpserver2.ftp-data: . ack 2 win 16060 <nop,nop,timestamp 451190528 1158115922> (DF)
ftpserver2.ftp-data > workstation.3013: F 1:1(0) ack 17269 win 15928 <nop,nop,timestamp 1158115941 451190243> (DF)
workstation.3013 > ftpserver2.ftp-data: . ack 2 win 16060 <nop,nop,timestamp 451190547 1158115941> (DF)
ftpserver2.ftp-data > workstation.3014: F 1:1(0) ack 33877 win 15928 <nop,nop,timestamp 1158115969 451190269> (DF)
workstation.3014 > ftpserver2.ftp-data: . ack 2 win 16060 <nop,nop,timestamp 451190577 1158115969> (DF)
workstation.3015 > ftpserver2.ftp-data: S 1558404700:1558404700(0) ack 1214809981 win 16060 <mss 1460,sackOK,timestamp 451190611 1158115676,nop,wscale 0> (DF)
workstation.3015 > ftpserver2.ftp-data: S 1558404700:1558404700(0) ack 1214809981 win 16060 <mss 1460,sackOK,timestamp 451191261 1158115676,nop,wscale 0> (DF)
workstation.3015 > ftpserver2.ftp-data: S 1558404700:1558404700(0) ack 1214809981 win 16060 <mss 1460,sackOK,timestamp 451192511 1158115676,nop,wscale 0> (DF)
workstation.3006 > ftpserver2.ftp: P 858:879(21) ack 1633 win 16060 <nop,nop,timestamp 451193284 1158115678> (DF)
ftpserver2.ftp > workstation.3006: . ack 879 win 16060 <nop,nop,timestamp 1158118680 451193284> (DF)





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