Thread: TCP packets not reaching application

hi,

trying use wireless broadband device on ubuntu 10.10. device able ip address , can ping outside world through interface. tcp , udp packets outside world not reaching applications. e.g. if ftp out external machine on wireless broadband interface, see remote server responding syn ack ftp program doesnt receive that. can see syn ack packet on wireshark running on ubuntu machine , wireshark able decode tcp syn ack correctly. idea why packet wouldnt reach application ? tried telnet, ftp, iperf tcp etc , none of them work.

have eth0 (wired ethernet) , on these applications work without problem. iptables has no policy.

php code:

# iptables -l -v
chain input (policy accept 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         

chain forward (policy accept 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         

chain output (policy accept 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination 

here is the pkt dump

no.     time        source                destination           protocol info
  11211 22.951034   27.143.21.90          27.135.2.13           tcp      45969 > ftp [syn] seq=0 win=5840 len=0 mss=1460 tsv=453226043 tser=0 ws=6

frame 11211 (74 bytes on wire, 74 bytes captured)
ethernet ii, src: woonsang_04:01:03 (01:02:03:04:01:03), dst: kollmorg_87:02:0d (01:02:1b:87:02:0d)
internet protocol, src: 27.143.21.90 (27.143.21.90), dst: 27.135.2.13 (27.135.2.13)
transmission control protocol, src port: 45969 (45969), dst port: ftp (21), seq: 0, len: 0
    source port: 45969 (45969)
    destination port: ftp (21)
    [stream index: 0]
    sequence number: 0    (relative sequence number)
    header length: 40 bytes
    flags: 0x02 (syn)
    window size: 5840
    checksum: 0x91ac [validation disabled]
    options: (20 bytes)

no.     time        source                destination           protocol info
  11230 22.990016   27.135.2.13           27.143.21.90          tcp      ftp > 45969 [syn, ack] seq=0 ack=1 win=5792 len=0 mss=1460 tsv=2544061120 tser=453226043 ws=6

frame 11230 (74 bytes on wire, 74 bytes captured)
ethernet ii, src: woonsang_ca:d8:02 (01:02:03:ca:d8:02), dst: woonsang_04:01:03 (01:02:03:04:01:03)
internet protocol, src: 27.135.2.13 (27.135.2.13), dst: 27.143.21.90 (27.143.21.90)
transmission control protocol, src port: ftp (21), dst port: 45969 (45969), seq: 0, ack: 1, len: 0
    source port: ftp (21)
    destination port: 45969 (45969)
    [stream index: 0]
    sequence number: 0    (relative sequence number)
    acknowledgement number: 1    (relative ack number)
    header length: 40 bytes
    flags: 0x12 (syn, ack)
    window size: 5792
    checksum: 0xf901 [validation disabled]
    options: (20 bytes)
    [seq/ack analysis]
        [this is an ack to the segment in frame: 11211]
        [the rtt to ack the segment was: 0.038982000 seconds] 


kind of new ubuntu. dont see error on /var/log/messages or anywhere packets being dropped. ?.

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