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Hello,
On Fri, 14 Jul 2017, Timothy R. Weiand wrote:
> I am building a DR-TUN configuration to load balance DNS traffic. My issue
> is with the real servers: the ipip packet get unwrapped and appears on the
> tunnel interface and becomes a martian. Also, I have not been able to
> determine how to bind to the tunnel interface to capture these packets. I
> have verified details with tcpdump/dmesg. All my configuration is scripted
> to ensure reproducibility. tcpdumps below do not show real DNS traffic;
> using netcat to send text.
>
> Much more detail can be supplied, please request it.
>
> Configuration:
>
> ==============
>
> - All machines are currently Debian 9 (4.9.30-2+deb9u2)
>
> - Client: 192.168.200.10
>
> - Director: 192.168.200.11
>
> - Real Server: 192.168.200.12
>
> - No VIP: I am using the IP address for my director interface -
> 192.168.200.11
>
>
> Director Configuration:
>
> ==================
>
> vagrant@debian-9-lb:~$ sudo ipvsadm -Ln
>
> IP Virtual Server version 1.2.1 (size=4096)
>
> Prot LocalAddress:Port Scheduler Flags
>
> -> RemoteAddress:Port Forward Weight ActiveConn InActConn
>
> UDP 192.168.200.11:53 rr
>
> -> 192.168.200.12:53 Tunnel 1 0 0
>
>
>
> Real Server:
>
> ============
>
> # modprobe ipip
>
> # echo 1 > /proc/sys/net/ipv4/ip_forward
>
> # ip tunnel add tunl1 mode ipip ttl 32 local 192.168.200.12 remote
> 192.168.200.11
>
> # ip link set tunl1 up arp off
>
> # echo 2 > /proc/sys/net/ipv4/conf/all/rp_filter
>
> # echo 2 > /proc/sys/net/ipv4/conf/default/rp_filter
>
> # echo 2 > /proc/sys/net/ipv4/conf/tunl0/rp_filter
>
> # echo 2 > /proc/sys/net/ipv4/conf/tunl1/rp_filter
tunl1/rp_filter=2 is ignored if there are no
IPv4 addresses configured on tunl1, you can see
__fib_validate_source() for reference:
if (no_addr)
goto last_resort;
As result, packets are dropped as martians due to rpf=2.
To check if packets are dropped by routing try:
ip route get from 192.168.200.10 to 192.168.200.11 iif tunl1
Here is small howto for TUN (outdated):
http://ja.ssi.bg/TUN-HOWTO.txt
> vagrant@debian-9-dns:~$ sudo tcpdump -e -n -s 0 -i tunl1 -vv
>
> tcpdump: listening on tunl1, link-type RAW (Raw IP), capture size 262144
> bytes
>
> 10:16:13.919646 ip: (tos 0x0, ttl 64, id 63545, offset 0, flags [DF], proto
> UDP (17), length 40)
>
> 192.168.200.10.51149 > 192.168.200.11.53: [udp sum ok] 26226 updateMA+
> [b2&3=0x6f6d] [27753a] [11619q] [25966n] [29706au][|domain]
>
>
>
> If I add an IP address to the interface the packet never reaches tunl1
>
> # ip addr add 192.168.200.11/24 brd 192.168.200.11 dev tunl1
Try with (note mask /32):
ip addr add 192.168.200.11/32 dev tunl1
as shown in LVS HOWTO (8.3):
http://www.austintek.com/LVS/LVS-HOWTO/HOWTO/LVS-HOWTO.LVS-Tun.html
> Notes:
>
> ======
>
>
>
> LVS-DR was not an option because the real servers will be in different
> subnets (I was able to get LVS-DR working though).
>
>
>
> I am looking for advice on how to better understand or resolve this issue.
> Or, who would be better to answer this question.
>
>
>
> I have groked as many articles on how to setup this configuration as I can.
> And, I have read a good deal of the archives of this mailing list.
>
>
>
> Linux distributions I have tried are Debian, Ubuntu and Amazon linux. This
> is been tested on both AWS and VMware fusion.
>
>
>
> ------
>
>
>
> I have a feeling I am missing something simple...
>
>
>
> Thanks!
>
> -Timothy
Regards
--
Julian Anastasov <ja@xxxxxx>
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