ESTABILISHED connections are not that estabilished

Gioele Barabucci dev at gioelebarabucci.com
Wed Jul 27 20:52:26 CEST 2005


Gioele Barabucci wrote:
> In my logs I often find reports of dropped input packets from my DNS:53 or
> dropped output packets generated from localhost:25 to other mail servers.
An example of the DNS issue. I think that the SMTP issue is identical.

This is what happens when I launch 

  $ dig -x 66.70.178.103
  ;; Warning: Message parser reports malformed message packet.
  ;; Truncated, retrying in TCP mode.
  ;; Connection to 209.51.143.76#53(209.51.143.76) for
103.178.70.66.in-addr.arpa. failed: connection refused.
  ;; Connection to 69.93.28.254#53(69.93.28.254) for
103.178.70.66.in-addr.arpa. failed: connection refused.

  iptables OUTPUT DROP IN= OUT=eth0 SRC=myIP DST=209.51.143.76 LEN=60
TOS=0x00 PREC=0x00 TTL=64 ID=2747 DF PROTO=TCP SPT=1025 DPT=53 WINDOW=5840
RES=0x00 SYN URGP=0 OPT (020405B40402080A00008F8F0000000001030301)
  iptables OUTPUT DROP IN= OUT=eth0 SRC=myIP DST=69.93.28.254 LEN=60
TOS=0x00 PREC=0x00 TTL=64 ID=8196 DF PROTO=TCP SPT=1026 DPT=53 WINDOW=5840
RES=0x00 SYN URGP=0 OPT (020405B40402080A00008FF40000000001030301)
  iptables OUTPUT DROP IN= OUT=eth0 SRC=myIP DST=209.51.143.76 LEN=60
TOS=0x00 PREC=0x00 TTL=64 ID=2749 DF PROTO=TCP SPT=1025 DPT=53 WINDOW=5840
RES=0x00 SYN URGP=0 OPT (020405B40402080A000090BB0000000001030301)
  iptables OUTPUT DROP IN= OUT=eth0 SRC=myIP DST=69.93.28.254 LEN=60
TOS=0x00 PREC=0x00 TTL=64 ID=8198 DF PROTO=TCP SPT=1026 DPT=53 WINDOW=5840
RES=0x00 SYN URGP=0 OPT (020405B40402080A000091200000000001030301)


but then
  $ dig netfilter.org
  ;; QUESTION SECTION:
  ;netfilter.org.                 IN      A
  
  ;; ANSWER SECTION:
  netfilter.org.          43200   IN      A       213.95.27.115

and iptables don't drop any packets.

Obviously I have these broad rules for output

iptables -A OUTPUT -p udp --dport nameserver -j ACCEPT
iptables -A OUTPUT -p tcp --dport nameserver -j ACCEPT

-- 
Gioele <dev at gioelebarabucci.com>




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