[Planetlab-users] tcpdump and capturing incoming packets

[Greg Banks]

hi all,

i am new to planet lab and am having some problems with tcpdump and  
capturing http sessions that are originating from my slice/node.  
basically, i see all outgoing packets, including those with an HTTP  
payload, but only incoming ACKs with no HTTP payload (not even SYN/ 
ACK packets). here is some sample output when trying to capture http  
traffic to a proxy running on port 4545:

01:04:33.187359 IP planetlab01.dis.unina.it.43387 > planetlab01.mpi- 
sws.mpg.de.worldscores: S 1248952370:1248952370(0) win 5840 <mss  
1460,sackOK,timestamp 1116447448 0>
E..8". at .@............{..Jq.2........K..........
B.......
01:04:33.219712 IP planetlab01.dis.unina.it.43387 > planetlab01.mpi- 
sws.mpg.de.worldscores: . ack 55681466 win 5840 <nop,nop,timestamp  
1116447481 229909180>
E..4". at .@............{..Jq.3.Q.......(.....
."..
01:04:39.933180 IP planetlab01.dis.unina.it.43387 > planetlab01.mpi- 
sws.mpg.de.worldscores: P 0:15(15) ack 1 win 5840 <nop,nop,timestamp  
1116454194 229909180>
E..C". at .@............{..Jq.3.Q.......K.....
.".GET / HTTP/1.1

01:04:39.966642 IP planetlab01.mpi-sws.mpg.de.worldscores >  
planetlab01.dis.unina.it.43387: . ack 15 win 5792 <nop,nop,timestamp  
229915928 1116454194>
E..4.f at .1.7{...........{.Q..Jq.B....[......
.=.B..2
01:04:45.387559 IP planetlab01.dis.unina.it.43387 > planetlab01.mpi- 
sws.mpg.de.worldscores: P 15:37(22) ack 1 win 5840 <nop,nop,timestamp  
1116459649 229915928>
E..J". at .@............{..Jq.B.Q.......t.....
.=.host: www.cs.ucsb.edu

01:04:45.419964 IP planetlab01.mpi-sws.mpg.de.worldscores >  
planetlab01.dis.unina.it.43387: . ack 37 win 5792 <nop,nop,timestamp  
229921384 1116459649>
E..4.g at .1.7z...........{.Q..Jq.X....0......
.RhB...
01:04:45.628316 IP planetlab01.dis.unina.it.43387 > planetlab01.mpi- 
sws.mpg.de.worldscores: P 37:38(1) ack 1 win 5840 <nop,nop,timestamp  
1116459889 229921384>
E..5". at .@............{..Jq.X.Q......%......
.Rhq

01:04:45.661794 IP planetlab01.mpi-sws.mpg.de.worldscores >  
planetlab01.dis.unina.it.43387: . ack 38 win 5792 <nop,nop,timestamp  
229921625 1116459889>
E..4.h at .1.7y...........{.Q..Jq.Y..../......
.SYB..q
01:04:46.307563 IP planetlab01.dis.unina.it.43387 > planetlab01.mpi- 
sws.mpg.de.worldscores: . ack 1449 win 8688 <nop,nop,timestamp  
1116460569 229922271>
E..4". at .@............{..Jq.Y.Q.b..!........
.U..
01:04:46.307768 IP planetlab01.dis.unina.it.43387 > planetlab01.mpi- 
sws.mpg.de.worldscores: . ack 2897 win 11584 <nop,nop,timestamp  
1116460569 229922271>
E..4". at .@............{..Jq.Y.Q.
..- at .......
.U..
01:04:46.307790 IP planetlab01.dis.unina.it.43387 > planetlab01.mpi- 
sws.mpg.de.worldscores: . ack 4127 win 14480 <nop,nop,timestamp  
1116460569 229922271>
E..4". at .@............{..Jq.Y.Q....8........
.U..
01:04:46.483128 IP planetlab01.dis.unina.it.43387 > planetlab01.mpi- 
sws.mpg.de.worldscores: . ack 5575 win 17376 <nop,nop,timestamp  
1116460744 229922446>
E..4". at .@............{..Jq.Y.Q....C........
.V..
01:04:46.483155 IP planetlab01.dis.unina.it.43387 > planetlab01.mpi- 
sws.mpg.de.worldscores: . ack 7023 win 20272 <nop,nop,timestamp  
1116460744 229922446>
E..4". at .@............{..Jq.Y.Q.(..O0.......
.V..
01:04:46.484308 IP planetlab01.dis.unina.it.43387 > planetlab01.mpi- 
sws.mpg.de.worldscores: . ack 8231 win 23168 <nop,nop,timestamp  
1116460745 229922446>
E..4". at .@............{..Jq.Y.Q....Z........
.V..
01:04:46.484331 IP planetlab01.dis.unina.it.43387 > planetlab01.mpi- 
sws.mpg.de.worldscores: . ack 9679 win 26064 <nop,nop,timestamp  
1116460745 229922447>
E..4". at .@............{..Jq.Y.Q....e........
.V..

should this be the case? am i doing something wrong? any suggestions  
would be much appreciated. thanks.

cheers,
greg