Hi Vikktor, Thank you for your reply.
It surprising because currently I have no firewall enabled. Below an example when the connection is properly established. 07:07:15.040105 IP mail-vx0-f173.google.com.61783 > passrlminisrv.cinema-voiron.fr.smtp: Flags [S], seq 4025038703, win 5720, options [mss 1430,sackOK,TS val 4181884618 ecr 0,nop,wscale 6], length 0 07:07:18.039674 IP mail-vx0-f173.google.com.61783 > passrlminisrv.cinema-voiron.fr.smtp: Flags [S], seq 4025038703, win 5720, options [mss 1430,sackOK,TS val 4181887618 ecr 0,nop,wscale 6], length 0 07:07:24.038889 IP mail-vx0-f173.google.com.61783 > passrlminisrv.cinema-voiron.fr.smtp: Flags [S], seq 4025038703, win 5720, options [mss 1430,sackOK,TS val 4181893618 ecr 0,nop,wscale 6], length 0 07:07:30.090982 IP passrlminisrv.cinema-voiron.fr.smtp > mail-vx0-f173.google.com.61783: Flags [S.], seq 2112870518, ack 4025038704, win 65535, options [mss 1460,nop,wscale 1,nop,nop,TS val 537761090 ecr 4181893618,sackOK,eol], length 0 07:07:30.217508 IP mail-vx0-f173.google.com.61783 > passrlminisrv.cinema-voiron.fr.smtp: Flags [.], ack 1, win 90, options [nop,nop,TS val 4181899796 ecr 537761090], length 0 Maybe it's my router which manages the internet connection and NAT the incoming connection to my server which breaks the window scaling? Any workaround? xavier Le 18 juin 2011 à 02:26, Victor Duchovni a écrit : > On Sat, Jun 18, 2011 at 01:30:21AM +0200, Xavier Ambrosioni wrote: > >> 22:16:25.978773 IP smtp10.smtpout.orange.fr.41183 > >> passrlminisrv.cinema-voiron.fr.smtp: Flags [S], seq 105066692, win 5840, >> options [mss 1380,sackOK,TS val 2993558281 ecr 0,nop,wscale 8], length 0 >> 22:16:28.978262 IP smtp10.smtpout.orange.fr.41183 > >> passrlminisrv.cinema-voiron.fr.smtp: Flags [S], seq 105066692, win 5840, >> options [mss 1380,sackOK,TS val 2993561281 ecr 0,nop,wscale 8], length 0 >> 22:16:34.977258 IP smtp10.smtpout.orange.fr.41183 > >> passrlminisrv.cinema-voiron.fr.smtp: Flags [S], seq 105066692, win 5840, >> options [mss 1380,sackOK,TS val 2993567281 ecr 0,nop,wscale 8], length 0 >> 22:16:41.011109 IP passrlminisrv.cinema-voiron.fr.smtp > >> smtp10.smtpout.orange.fr.41183: Flags [S.], seq 1934215990, ack 105066693, >> win 65535, options [mss 1460,nop,wscale 1,nop,nop,TS val 537443811 >> ecr2993567281,sackOK,eol], length 0 >> 22:16:41.051125 IP smtp10.smtpout.orange.fr.41183 > >> passrlminisrv.cinema-voiron.fr.smtp: Flags [R], seq 105066693, win 0, length >> 0 >> >> Any idea of the root cause? Could it be an issue with my DNS configuration >> or is it related with my own smtp server? > > Here's a nickel kid, buy yourself a real firewall. > > More seriously, your firewall does not understand window scaling. Disable > it on your Linux system (see the list archiving for the many previous > instances). Then consider getting a firewall that works with modern > TCP stacks. > > -- > Viktor.
