On Saturday, 07 August 2004, at 20:27:49 +0200, Jose Luis Domingo Lopez wrote: > In the last couple of months I have been having a problem trying to > access just one web site of the many I usually browse from my home PC, > with Linux kernels 2.6.x. The only site I have been experiencing > problems with is: > http://gestiona.madrid.org/nomecalles/ > Hate to reply to myself, but as I found the cause of the problem (and a fix for it) I thought it could be of interest to someone browsing the archives in the search for help. To summarize the problem, in recent 2.6.x Linux kernels and with no changes in userland or in the kernel .config, I was unable to fully display the web site at: http://gestiona.madrid.org/nomecalles/ A "tcpdump" showed my Linux PC ACK'ing some TCP segments, but completely ignoring some other following the former, for which Linux would never send and ACK, but duplicate ACK for the already acknowledged segments. The cause of the problem is the ingress queuing discipline being used in the box to policy incoming traffic in the hope of keeping remote sessions interactive enough while downloading over a POTS PPP link. It seems the remote web server (some Oracle application server) never tried to resend TCP segments still not acknowledged, and when it did several big segments where sent at once, in fact triggering the ingress policy limit, and so the networking stack never saw those segments, so no chance for any acknowledgment back to the server. Once I delete the ingress queuing discipline (tc qdisc del dev ppp0 ingress) the access to the remote web server works fine, as expected. As the remote server underwent some changes and upgrades when or around the problem first arised, and since I have been unable to identify the first kernel which gave me the described problems, I suppose what happened is just "bad luck" :-) Thanks, and sorry for the noise. -- Jose Luis Domingo Lopez Linux Registered User #189436 Debian Linux Sid (Linux 2.6.8.1-vp) - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
