Hi, any chance I could get some of the netfilter gurus to have a look at this? Essentially we have a reproducible situation where conntrack is (apparently) relating a packet to a connection, but not incrementing the connection counters? Thanks for any help figuring out a fix? Ed W On 15/07/2011 12:45, Ed W wrote: > Hi, This is related to a previous thread, but more complete problem > statement below: > > I notice that I can get an ICMP packet to bypass parts of conntrack > under the following conditions > > - Send a UDP packet that triggers some kind of UDP reply > - Close the listening UDP socket before that reply arrives > - Kernel generates an ICMP unreachable response which does not appear to > be tracked (as expected) by conntrack > > Tested with kernel 2.6.38.4 + iptables 1.4.11.1 > > Reproduce this easily like so: > > nslookup www.yahoo.co.uk 8.8.8.8 & sleep 0.001 && killall nslookup > > (where the sleep obviously needs to be smaller than your DNS RTT > lookup time. Obviously substitute nslookup/dig as appropriate...) > > My results > > # conntrack -E > > [NEW] udp 17 30 src=10.141.86.7 dst=8.8.8.8 sport=60721 > dport=53 [UNREPLIED] src=8.8.8.8 dst=10.141.86.7 sport=53 dport=60721 > [UPDATE] udp 17 29 src=10.141.86.7 dst=8.8.8.8 sport=60721 > dport=53 src=8.8.8.8 dst=10.141.86.7 sport=53 dport=60721 > [DESTROY] udp 17 src=10.141.86.7 dst=8.8.8.8 sport=60721 dport=53 > packets=1 bytes=66 src=8.8.8.8 dst=10.141.86.7 sport=53 dport=60721 > packets=1 bytes=110 > > # tcpdump > > 11:26:35.072564 IP 10.141.86.7.60721 > 8.8.8.8.domain: 2+ PTR? > 8.8.8.8.in-addr.arpa. (38) > 11:26:35.351804 IP 8.8.8.8.domain > 10.141.86.7.60721: 2 1/0/0 PTR > google-public-dns-a.google.com. (82) > 11:26:35.352110 IP 10.141.86.7 > 8.8.8.8: ICMP 10.141.86.7 udp port > 60721 unreachable, length 118 > > > # iptables -A OUTPUT -j LOGMARK > # iptables -A OUTPUT -j LOG > > Jul 15 11:26:35 localhost kern.warn kernel: [ 6676.964396] iif=0 > hook=OUTPUT nfmark=0x0 secmark=0x0 classify=0x0 ctdir=ORIGINAL > ct=0xcf3d5060 ctmark=0x0 ctstate=NEW ctstatus= lifetime=6346s > Jul 15 11:26:35 localhost kern.warn kernel: [ 6676.964396] IN= OUT=ppp1 > SRC=10.141.86.7 DST=8.8.8.8 LEN=66 TOS=0x00 PREC=0x00 TTL=64 ID=19971 DF > PROTO=UDP SPT=60721 DPT=53 LEN=46 > Jul 15 11:26:35 localhost kern.warn kernel: [ 6677.249312] iif=0 > hook=OUTPUT nfmark=0x0 secmark=0x0 classify=0x0 ctdir=ORIGINAL > ct=0xcf3d5060 ctmark=0x0 ctstate=RELATED ctstatus=SEEN_REPLY,CONFIRMED > lifetime=4294937s > Jul 15 11:26:35 localhost kern.warn kernel: [ 6677.249426] IN= OUT=ppp1 > SRC=10.141.86.7 DST=8.8.8.8 LEN=138 TOS=0x00 PREC=0xC0 TTL=64 ID=18412 > PROTO=ICMP TYPE=3 CODE=3 [SRC=8.8.8.8 DST=10.141.86.7 LEN=110 TOS=0x00 > PREC=0x00 TTL=46 ID=3897 PROTO=UDP SPT=53 DPT=60721 LEN=90 > > > Notice that logmark seems to show that the ctstatus on the ICMP packet > is SEEN_REPLY, but conntrack -E shows only packets=1? tcpdump shows > that the ICMP packet did indeed go out > > Could someone with more knowledge of conntrack please investigate further? > > Thanks > > Ed W > -- > To unsubscribe from this list: send the line "unsubscribe netfilter" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe netfilter" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
