From: Lorenzo A. <le...@ti...> - 2001-12-25 15:02:08
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At 13.50 24/12/01 -0500, Jeff Dike wrote: >le...@ti... said: >> They are identical. > >So that means that all the packets generated by UML network are making it >out to the host. > >> Interesting enough, I changed the MTU on both interfaces from 1500 to >> 1484. In this way it seems to work, but I get just 1MB/s. > >This suggests that the TUN/TAP driver is messing up somehow, or the UML >driver is sending packets that are too big or something. > >> UML: >> ) ack 9 win 5728 <nop,nop,timestamp 63996 10758> (DF) >[snip] >> host: >> 14:42:12.968224 192.168.1.3.31236 > 192.168.1.128.1026: . >[snip] > >Those two dumps don't look identical at all. Were they generated from the >same traffic? Yes. >Does it work when you reverse the direction? Yes it does, see below. >If so, I guess we need to >compare that tcpdump to the ones that show the hang. bw_tcp -s on UML tcpdump -n -i eth0 (UML): 14:49:51.936850 192.168.1.127.32773 > 192.168.1.128.31236: . ack 10449185 win 47784 <nop,nop,timestamp 19879 2286> (DF) 14:49:51.936850 192.168.1.128.31236 > 192.168.1.127.32773: . 10449185:10450633(1448) ack 9 win 5792 <nop,nop,timestamp 2286 19873> (DF) 14:49:51.936850 192.168.1.128.31236 > 192.168.1.127.32773: . 10450633:10452081(1448) ack 9 win 5792 <nop,nop,timestamp 2286 19873> (DF) 14:49:51.936850 192.168.1.127.32773 > 192.168.1.128.31236: . ack 10452081 win 47784 <nop,nop,timestamp 19879 2286> (DF) 14:49:51.936850 192.168.1.128.31236 > 192.168.1.127.32773: . 10452081:10453529(1448) ack 9 win 5792 <nop,nop,timestamp 2286 19873> (DF) 14:49:51.936850 192.168.1.128.31236 > 192.168.1.127.32773: . 10453529:10454977(1448) ack 9 win 5792 <nop,nop,timestamp 2286 19873> (DF) 14:49:51.936850 192.168.1.127.32773 > 192.168.1.128.31236: . ack 10454977 win 47784 <nop,nop,timestamp 19879 2286> (DF) 14:49:51.936850 192.168.1.128.31236 > 192.168.1.127.32773: . 10454977:10456425(1448) ack 9 win 5792 <nop,nop,timestamp 2286 19873> (DF) 14:49:51.936850 192.168.1.128.31236 > 192.168.1.127.32773: F 10485761:10485761(0) ack 10 win 5792 <nop,nop,timestamp 2286 19879> (DF) 14:49:51.936850 192.168.1.127.32773 > 192.168.1.128.31236: . ack 10485762 win 47784 <nop,nop,timestamp 19881 2286> (DF) 5926 packets received by filter 0 packets dropped by kernel tcpdump -n -i tap0 (host): 14:49:51.819163 192.168.1.128.31236 > 192.168.1.127.32773: . 10348521:10349969(1448) ack 9 win 5792 <nop,nop,timestamp 2285 19866> (DF) 14:49:51.819218 192.168.1.127.32773 > 192.168.1.128.31236: . 9:9(0) ack 10349969 win 47784 <nop,nop,timestamp 19871 2285> (DF) 14:49:51.819421 192.168.1.128.31236 > 192.168.1.127.32773: . 10349969:10351417(1448) ack 9 win 5792 <nop,nop,timestamp 2285 19866> (DF) 14:49:51.819539 192.168.1.128.31236 > 192.168.1.127.32773: . 10351417:10352865(1448) ack 9 win 5792 <nop,nop,timestamp 2285 19866> (DF) 14:49:51.819594 192.168.1.127.32773 > 192.168.1.128.31236: . 9:9(0) ack 10352865 win 47784 <nop,nop,timestamp 19871 2285> (DF) 14:49:51.819801 192.168.1.128.31236 > 192.168.1.127.32773: . 10352865:10354313(1448) ack 9 win 5792 <nop,nop,timestamp 2285 19866> (DF) 14:49:51.819920 192.168.1.128.31236 > 192.168.1.127.32773: P 10354313:10354689(376) ack 9 win 5792 <nop,nop,timestamp 2285 19866> (DF) 14:49:51.819973 192.168.1.127.32773 > 192.168.1.128.31236: . 9:9(0) ack 10354689 win 47784 <nop,nop,timestamp 19871 2285> (DF) 14:49:51.835378 192.168.1.127.32773 > 192.168.1.128.31236: . 9:9(0) ack 10357585 win 47784 <nop,nop,timestamp 19872 2285> (DF) 14:49:51.835784 192.168.1.127.32773 > 192.168.1.128.31236: . 9:9(0) ack 10360481 win 47784 <nop,nop,timestamp 19872 2285> (DF) 5056 packets received by filter 6013 packets dropped by kernel The bandwidth reported by bw_tcp is about 6.7MB/sec. .. and now bw_tcp -s on the host tcpdump -n -i eth0: 14:53:02.217289 192.168.1.128.1024 > 192.168.1.3.31236: . ack 10460769 win 47784 <nop,nop,timestamp 6037 38603> (DF) 14:53:02.217289 192.168.1.128.1024 > 192.168.1.3.31236: . ack 10462217 win 47784 <nop,nop,timestamp 6037 38604> (DF) 14:53:02.217289 192.168.1.128.1024 > 192.168.1.3.31236: . ack 10463665 win 47784 <nop,nop,timestamp 6037 38604> (DF) 14:53:02.217289 192.168.1.128.1024 > 192.168.1.3.31236: . ack 10465113 win 47784 <nop,nop,timestamp 6037 38604> (DF) 14:53:02.217289 192.168.1.128.1024 > 192.168.1.3.31236: . ack 10466561 win 47784 <nop,nop,timestamp 6037 38604> (DF) 14:53:02.217289 192.168.1.128.1024 > 192.168.1.3.31236: . ack 10468009 win 47784 <nop,nop,timestamp 6037 38604> (DF) 14:53:02.217289 192.168.1.128.1024 > 192.168.1.3.31236: . ack 10469457 win 47784 <nop,nop,timestamp 6037 38604> (DF) 14:53:02.217289 192.168.1.128.1024 > 192.168.1.3.31236: . ack 10470905 win 47784 <nop,nop,timestamp 6037 38604> (DF) 14:53:02.217289 192.168.1.128.1024 > 192.168.1.3.31236: . ack 10472353 win 47784 <nop,nop,timestamp 6037 38604> (DF) 14:53:02.217289 192.168.1.128.1024 > 192.168.1.3.31236: . ack 10473801 win 47784 <nop,nop,timestamp 6037 38604> (DF) 2607 packets received by filter 0 packets dropped by kernel tcpdump -n -i tap0: 14:53:02.168646 192.168.1.128.1024 > 192.168.1.3.31236: . 9:9(0) ack 10460769 win 47784 <nop,nop,timestamp 6037 38603> (DF) 14:53:02.168814 192.168.1.128.1024 > 192.168.1.3.31236: . 9:9(0) ack 10462217 win 47784 <nop,nop,timestamp 6037 38604> (DF) 14:53:02.168982 192.168.1.128.1024 > 192.168.1.3.31236: . 9:9(0) ack 10463665 win 47784 <nop,nop,timestamp 6037 38604> (DF) 14:53:02.169144 192.168.1.128.1024 > 192.168.1.3.31236: . 9:9(0) ack 10465113 win 47784 <nop,nop,timestamp 6037 38604> (DF) 14:53:02.169307 192.168.1.128.1024 > 192.168.1.3.31236: . 9:9(0) ack 10466561 win 47784 <nop,nop,timestamp 6037 38604> (DF) 14:53:02.169466 192.168.1.128.1024 > 192.168.1.3.31236: . 9:9(0) ack 10468009 win 47784 <nop,nop,timestamp 6037 38604> (DF) 14:53:02.169628 192.168.1.128.1024 > 192.168.1.3.31236: . 9:9(0) ack 10469457 win 47784 <nop,nop,timestamp 6037 38604> (DF) 14:53:02.169804 192.168.1.128.1024 > 192.168.1.3.31236: . 9:9(0) ack 10470905 win 47784 <nop,nop,timestamp 6037 38604> (DF) 14:53:02.169973 192.168.1.128.1024 > 192.168.1.3.31236: . 9:9(0) ack 10472353 win 47784 <nop,nop,timestamp 6037 38604> (DF) 14:53:02.170140 192.168.1.128.1024 > 192.168.1.3.31236: . 9:9(0) ack 10473801 win 47784 <nop,nop,timestamp 6037 38604> (DF) 1850 packets received by filter 6266 packets dropped by kernel bw_tcp hangs. As you can see in both tests tcpdump reports many dropped packets on the host, but "ifconfig tap0" doesn't report such packets. All tests done with the default MTU, 1500. Host is a SuSE 7.2, UML is a Debian 2.2 root image. Both bw_tcp compiled on Debian 2.2 -- Lorenzo |