Date: Mon, 18 Aug 2008 23:43:50 +0200 From: Todor Genov <todor.genov@za.verizonbusiness.com> To: freebsd-bugs@freebsd.org Subject: Possible bug - GRE tunnel routing Message-ID: <48A9ED16.2060201@za.verizonbusiness.com>
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Hi everyone,
I may have found a routing bug relating to GRE tunnels. Could somebody
try and replicate this?
As per the setup below GRE-encapsulated traffic to 194.31.254.148
should be going out via tun1, but a tcpdump shows the traffic leaving
via tun0. Any other traffic (icmp, tcp etc) destined to 194.31.154.148
goes out via tun1 as expected.
Configuration:
FreeBSD 7.0-STABLE #4: Mon Aug 18 13:50:38 SAST 2008
tun0 - PPPoE connection to ISP
tun1 - vpn connection to office PIX (via vpnc)
gre0 - GRE tunnel to machine sitting behind the PIX
tun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> metric 0 mtu 1492
inet 41.142.82.37 --> 41.142.82.1 netmask 0xffffff00
Opened by PID 509
tun1: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> metric 0 mtu 1500
inet 194.31.137.70 --> 194.31.137.64 netmask 0xffffff40
Opened by PID 984
gre0: flags=9051<UP,POINTOPOINT,RUNNING,LINK0,MULTICAST> metric 0 mtu 1476
tunnel inet 194.31.137.70 --> 194.31.154.148
inet 192.168.254.2 --> 192.168.254.1 netmask 0xffffff00
Routing table:
Destination Gateway Flags Refs Use Netif Expire
default 41.142.82.1 UGS 1 1365 tun0
41.142.82.1 41.142.82.37 UGH 1 0 tun0
192.168.254.1 192.168.254.2 UH 0 3 gre0
194.31.137.64 194.31.137.70 UH 1 0 tun1
194.31.154.148 194.31.137.64 UGS 0 0 tun1
GRE traffic (generated by ping -S 192.168.254.2 192.168.254.1) is routed
via tun0
[root@fw ~]# tcpdump -ni tun0 proto gre
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on tun0, link-type NULL (BSD loopback), capture size 96 bytes
23:14:58.700415 IP 194.31.137.70 > 194.31.154.148: GREv0, length 88: IP
192.168.254.2 > 192.168.254.1: ICMP echo request, id 61956, seq 777,
length 64
ICMP traffic (generated by ping -S 194.31.137.70 194.31.154.148) is
routed via tun1
[root@fw ~]# tcpdump -ni tun1 icmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on tun1, link-type NULL (BSD loopback), capture size 96 bytes
23:15:50.328470 IP 194.31.137.70 > 196.31.154.148: ICMP echo request, id
10757, seq 14, length 64
23:15:50.340888 IP 196.31.154.148 > 194.31.137.70: ICMP echo reply, id
10757, seq 14, length 64
Routing table:
Destination Gateway Flags Refs Use Netif Expire
default 41.142.82.1 UGS 1 1365 tun0
41.142.82.1 41.142.82.37 UGH 1 0 tun0
194.31.137.64 194.31.137.70 UH 1 0 tun1
194.31.154.148 194.31.137.64 UGS 0 0 tun1
If I change the host route
194.31.154.148 194.31.137.64 UGS 0 0 tun1
to a subnet route
194.31.154.0/24 194.31.137.64 UGS 0 0 tun1
everything works as expected and GRE traffic exits via tun1
--
Regards,
Todor Genov
Systems Operations
Verizon Business South Africa (Pty) Ltd
todor.genov@za.verizonbusiness.com
Tel: +27 11 235 6500
Fax: 086 692 0543
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