New: TCP madness - some packets are shunned.
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Quoted 28 lines · On Thu, 18 Mar 2010 02:46:29 GMT [email protected] wrote:
http://bugzilla.kernel.org/show_bug.cgi?id=15571
URL: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=53646 2 Summary: TCP madness - some packets are shunned. Product: Networking Version: 2.5 Kernel Version: 2.6.30 Platform: All OS/Version: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: Other AssignedTo: [email protected] ReportedBy: [email protected] Regression: NoThe host http://www.cv-it.com is virtually unreachable with kernel 2.6.26 (and later) slow with kernel 2.6.18 and just fine with windows XP.
I used telnet to port 80 for testing.
it seems to be a TCP issue, as the having the XP machine behind a linux based iptables firewall pc causes no problems, but telnet from the firewall pc itself to port 80 on www.cv-it.com does not work
Am 22.03.2010 22:37, schrieb Andrew Morton:
Quoted 35 lines
(switched to email. Please respond via emailed reply-to-all, not via the bugzilla web interface).
Quoted 28 lines · On Thu, 18 Mar 2010 02:46:29 GMT [email protected] wrote:
http://bugzilla.kernel.org/show_bug.cgi?id=15571
URL: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=53646 2 Summary: TCP madness - some packets are shunned. Product: Networking Version: 2.5 Kernel Version: 2.6.30 Platform: All OS/Version: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: Other AssignedTo: [email protected] ReportedBy: [email protected] Regression: NoThe host http://www.cv-it.com is virtually unreachable with kernel 2.6.26 (and later) slow with kernel 2.6.18 and just fine with windows XP.
I used telnet to port 80 for testing.
it seems to be a TCP issue, as the having the XP machine behind a linux based iptables firewall pc causes no problems, but telnet from the firewall pc itself to port 80 on www.cv-it.com does not work
For me it seems to be the host is messing up with the window scale option.
Although it claims to support window scaling:
16:23:17.466592 IP x.x.x.x.51151 > 121.199.32.220.80: Flags [S], seq 2159265664, win 5840, options [mss 1460,sackOK,TS val 8382141 ecr 0,nop,wscale 7], length 0 16:23:17.761697 IP 121.199.32.220.80 > x.x.x.x.51151: Flags [S.], seq 3910885479, ack 2159265665, win 65535, options [mss 1448,sackOK,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,wscale 8], length 0
My host (linux 2.6.32) is offering a window of 5888 (46<<7):
16:23:17.761740 IP x.x.x.x.51151 > 121.199.32.220.80: Flags [.], ack 1, win 46, length 0
And cv-it.com seems to think there is only a window of 46 ignoring the previously negotiated window scaling:
16:23:23.066318 IP 121.199.32.220.80 > x.x.x.x.51151: Flags [.], seq 1:47, ack 112, win 65160, length 46
You can disable window scaling with:
sysctl -w "net.ipv4.tcp_window_scaling=0"
Best regards,
Arnd
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Am 26.03.2010 06:31, schrieb Jasen Betts:
Quoted 49 lines · Arnd Hannemann
Quoted 48 lines
Am 22.03.2010 22:37, schrieb Andrew Morton:
Quoted 35 lines
(switched to email. Please respond via emailed reply-to-all, not via the bugzilla web interface).
Quoted 28 lines · On Thu, 18 Mar 2010 02:46:29 GMT [email protected] wrote:
http://bugzilla.kernel.org/show_bug.cgi?id=15571
URL: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=53646 2 Summary: TCP madness - some packets are shunned. Product: Networking Version: 2.5 Kernel Version: 2.6.30 Platform: All OS/Version: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: Other AssignedTo: [email protected] ReportedBy: [email protected] Regression: NoThe host http://www.cv-it.com is virtually unreachable with kernel 2.6.26 (and later) slow with kernel 2.6.18 and just fine with windows XP.
I used telnet to port 80 for testing.
it seems to be a TCP issue, as the having the XP machine behind a linux based iptables firewall pc causes no problems, but telnet from the firewall pc itself to port 80 on www.cv-it.com does not work
For me it seems to be the host is messing up with the window scale option.
Although it claims to support window scaling:
16:23:17.466592 IP x.x.x.x.51151 > 121.199.32.220.80: Flags [S], seq 2159265664, win 5840, options [mss 1460,sackOK,TS val 8382141 ecr 0,nop,wscale 7], length 0 16:23:17.761697 IP 121.199.32.220.80 > x.x.x.x.51151: Flags [S.], seq 3910885479, ack 2159265665, win 65535, options [mss 1448,sackOK,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,wscale 8], length 0My host (linux 2.6.32) is offering a window of 5888 (46<<7):
16:23:17.761740 IP x.x.x.x.51151 > 121.199.32.220.80: Flags [.], ack 1, win 46, length 0And cv-it.com seems to think there is only a window of 46 ignoring the previously negotiated window scaling:
16:23:23.066318 IP 121.199.32.220.80 > x.x.x.x.51151: Flags [.], seq 1:47, ack 112, win 65160, length 46
Quoted 8 lines
Quoted 3 lines
You can disable window scaling with:
sysctl -w "net.ipv4.tcp_window_scaling=0"yeah, that works for me.
I don't know a lot about this stuff. wikipedia says windows XP does window scaling also, yet it's not a problem with XP only with linux.
This may be pure coincidence that XP "works".
For instance if XP is only using a window scale of 1 or 2, the effect of ignoring the window scale may not be so drastic. However, the problem is:
once you negotiated the window scale for a connection you must not change
it and you may actually need a big window for performance reasons. So you have to pick a window scale value, so you can express the largest window you are going to use.
In Linux the maximum tcp receive window can be manipulated with the "net.ipv4.tcp_rmem" sysctl. (The max is the third value) Recent linux kernels use the amount of ram your machine has to calculate the default value for this.
Quoted 5 lines
Quoted 3 lines
My host (linux 2.6.32) is offering a window of 5888 (46<<7):
16:23:17.761740 IP x.x.x.x.51151 > 121.199.32.220.80: Flags [.], ack 1, win 46, length 0so you mean it seems to see '46' as '46' instead of 46<<7 == 5888
Exactly.
Best regards,
Arnd
Quoted 61 lines · On Fri, 26 Mar 2010 09:41:30 +0100 Arnd Hannemann…
[re-adding CCs] please reply to all
Am 26.03.2010 06:31, schrieb Jasen Betts:
Quoted 49 lines · Arnd Hannemann
Quoted 48 lines
Am 22.03.2010 22:37, schrieb Andrew Morton:
Quoted 35 lines
(switched to email. Please respond via emailed reply-to-all, not via the bugzilla web interface).
Quoted 28 lines · On Thu, 18 Mar 2010 02:46:29 GMT [email protected] wrote:
http://bugzilla.kernel.org/show_bug.cgi?id=15571
URL: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=53646 2 Summary: TCP madness - some packets are shunned. Product: Networking Version: 2.5 Kernel Version: 2.6.30 Platform: All OS/Version: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: Other AssignedTo: [email protected] ReportedBy: [email protected] Regression: NoThe host http://www.cv-it.com is virtually unreachable with kernel 2.6.26 (and later) slow with kernel 2.6.18 and just fine with windows XP.
I used telnet to port 80 for testing.
it seems to be a TCP issue, as the having the XP machine behind a linux based iptables firewall pc causes no problems, but telnet from the firewall pc itself to port 80 on www.cv-it.com does not work
For me it seems to be the host is messing up with the window scale option.
Although it claims to support window scaling:
16:23:17.466592 IP x.x.x.x.51151 > 121.199.32.220.80: Flags [S], seq 2159265664, win 5840, options [mss 1460,sackOK,TS val 8382141 ecr 0,nop,wscale 7], length 0 16:23:17.761697 IP 121.199.32.220.80 > x.x.x.x.51151: Flags [S.], seq 3910885479, ack 2159265665, win 65535, options [mss 1448,sackOK,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,nop,wscale 8], length 0My host (linux 2.6.32) is offering a window of 5888 (46<<7):
16:23:17.761740 IP x.x.x.x.51151 > 121.199.32.220.80: Flags [.], ack 1, win 46, length 0And cv-it.com seems to think there is only a window of 46 ignoring the previously negotiated window scaling:
16:23:23.066318 IP 121.199.32.220.80 > x.x.x.x.51151: Flags [.], seq 1:47, ack 112, win 65160, length 46Quoted 8 lines
Quoted 3 lines
You can disable window scaling with:
sysctl -w "net.ipv4.tcp_window_scaling=0"yeah, that works for me.
I don't know a lot about this stuff. wikipedia says windows XP does window scaling also, yet it's not a problem with XP only with linux.
Quoted 17 lines
This may be pure coincidence that XP "works".
For instance if XP is only using a window scale of 1 or 2, the effect of ignoring the window scale may not be so drastic. However, the problem is:
once you negotiated the window scale for a connection you must not change
it and you may actually need a big window for performance reasons. So you have to pick a window scale value, so you can express the largest window you are going to use.
In Linux the maximum tcp receive window can be manipulated with the "net.ipv4.tcp_rmem" sysctl. (The max is the third value) Recent linux kernels use the amount of ram your machine has to calculate the default value for this.Quoted 5 lines
Quoted 3 lines
My host (linux 2.6.32) is offering a window of 5888 (46<<7):
16:23:17.761740 IP x.x.x.x.51151 > 121.199.32.220.80: Flags [.], ack 1, win 46, length 0so you mean it seems to see '46' as '46' instead of 46<<7 == 5888
The window is also settable on a per route basis as well.
Quoted 4 lines · Stephen Hemminger
The window is also settable on a per route basis as well.
Have used this on our squid proxy server, all is good now. thanks.
ip route add 121.199.32.220 via upstream.ip.router.addr window 65535