On 2012-12-04, Rob Landley <r...@landley.net> wrote: > On 12/04/2012 12:17:25 AM, Woody Wu wrote: >> Hi, list >> >> I am not sure this has something with kernel. > > It doesn't. > >> But the system I just >> generated cannot be reached from ping. It can ping outside, but if I >> ping it from outside, I just get "Destination Host Unreachable". > > Some distributions' default firewall rules respond to icmp packets with > a host unreachable packet. This is a system/network administration > thing (iptables) and nothing to do with kernel development. > >> I think there is not firewall in between, > > There's a firewall built into linux, read the man page for the > "iptables" command. The "iptables-save" command dumps your entire > current ruleset to stdout so you can see what's in there. (You might > have to run it as root, I forget.) > > https://help.ubuntu.com/community/IptablesHowTo >
This 'distribution' I am running is a tailor linux 3.4.19 on an embedded system (Samsung S3C2410). Because this is a very small system, I believe I did not add any ip-table options in the kernel. And, I did not install any user space firware packet for it. So maybe this is really a firewall play in between. Now I run tcpdump on the target system with 'tcpdump -i eth0'. Then when I ping it from another Linux box, I see nothing from the tcpdump output. Does this confirm there is a firewall blocked the ping packets? Thanks in advance. -- woody I can't go back to yesterday - because I was a different person then. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/