Date: Tue, 2 Sep 2003 23:07:30 +0100 From: Bruce M Simpson <bms@spc.org> To: freebsd-net@freebsd.org Subject: Problems with if_gre Message-ID: <20030902220730.GL1417@spc.org>
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Hi all,
First of all apologies for the length of this mail - it is quite voluminous
as I'm trying to pack in all required information.
I don't seem to be able to achieve an end-to-end path between my Cisco
2520 and my laptop running FreeBSD 5.1-RELEASE using the GRE tunneling
protocol. Before I delve in and start touching code, I wanted to run this
all by you first.
I've had some weird problems with if_gre not getting the route correct
if interface parameters aren't configured in a strict order (inner tunnel
addresses *first*, outer addresses *last). I've observed behaviour such
as the GRE tunneling code ARPing out for addresses that are already in
the routing table.
Right now I'd just like for these two machines to talk to each other
over GRE. There is no problem with end-to-end IP connectivity -both are
on the same ethernet switch, no vlanning is in use, and ntpd on the FreeBSD
machine is pointed at the Cisco which is in turn getting its ntpd updates
from a public NTP server in the wider Internet.
saboteur:/tftpboot % uname -a
FreeBSD saboteur.dek.spc.org 5.1-RELEASE FreeBSD 5.1-RELEASE #4: Wed Aug 20 07:43:54 BST 2003 root@saboteur.dek.spc.org:/usr/src/sys/i386/compile/SABOTEUR i386
bms-gre-eth0#sho ver
Cisco Internetwork Operating System Software
IOS (tm) 2500 Software (C2500-IS-L), Version 12.0(27), RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2003 by cisco Systems, Inc.
Compiled Mon 09-Jun-03 21:39 by srani
Image text-base: 0x0303E2B8, data-base: 0x00001000
...
Say I do this:
17 22:33 s ifconfig gre0 create
18 22:33 s ifconfig gre0 172.16.1.2/30 172.16.1.1
19 22:33 ifconfig -a
20 22:33 s ifconfig gre0 tunnel saboteur bms-gre-eth0j
21 22:33 ifconfig -a
22 22:33 s tcpdump -i gre0
Then I do this:
bms-gre-eth0#sho run
Building configuration...
...
interface Tunnel0
ip address 172.16.1.1 255.255.255.252
no ip directed-broadcast
tunnel source Ethernet0
tunnel destination saboteur
...
ip classless
...
bms-gre-eth0#sho ip ro
...
172.16.0.0/30 is subnetted, 1 subnets
C 172.16.1.0 is directly connected, Tunnel0
bms-gre-eth0#sho ip arp
Protocol Address Age (min) Hardware Addr Type Interface
...
Internet saboteur 10 0004.765e.ec7d ARPA Ethernet0
I see the packets in tcpdump on saboteur:
saboteur:/tftpboot % s tcpdump -i gre0
tcpdump: listening on gre0
22:40:18.871918 172.16.1.1 > 172.16.1.2: icmp: echo request
22:40:18.871957 172.16.1.2 > 172.16.1.1: icmp: echo reply
22:40:20.869234 172.16.1.1 > 172.16.1.2: icmp: echo request
22:40:20.869270 172.16.1.2 > 172.16.1.1: icmp: echo reply
But...
bms-gre-eth0#ping 172.16.1.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.1.2, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
Most perplexing. If I look at:
saboteur:/tftpboot % netstat -r
Routing tables
...
bms-gre-eth0 00:50:54:80:06:98 UHLW 1 86 xl0 323
...
172.16.1.1 172.16.1.2 UH 0 15 gre0
Bizarro. Both routing tables look fine.
Now let's try pinging the Cisco from the FreeBSD machine.
saboteur:/tftpboot % ping 172.16.1.1
PING 172.16.1.1 (172.16.1.1): 56 data bytes
saboteur:~ % s tcpdump -i xl0 -p -e ip proto gre
tcpdump: listening on xl0
22:56:12.558538 0:4:76:5e:ec:7d 0:2:b3:8d:23:e4 0800 122: saboteur > bms-eth-gre0: gre 172.16.1.2 > 172.16.1.1: icmp: echo request
So far so good, but no reply.
bms-gre-eth0#show int tunnel0
Tunnel0 is up, line protocol is up
Hardware is Tunnel
Internet address is 172.16.1.1/30
MTU 1514 bytes, BW 9 Kbit, DLY 500000 usec, rely 255/255, load 1/255
Encapsulation TUNNEL, loopback not set, keepalive set (10 sec)
Tunnel source XX.XX.XX.XX (Ethernet0), destination YY.YY.YY.YY
Tunnel protocol/transport GRE/IP, key disabled, sequencing disabled
Checksumming of packets disabled, fast tunneling enabled
Last input 00:18:41, output 00:17:56, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 1
Queueing strategy: fifo
Output queue 0/0 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
28 packets output, 8668 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
YY.YY.YY.YY is saboteur's IP.
saboteur:/tftpboot % ifconfig gre0
gre0: flags=9051<UP,POINTOPOINT,RUNNING,LINK0,MULTICAST> mtu 1476
inet 172.16.1.2 --> 172.16.1.1 netmask 0xfffffffc
What's going on? None of the additional RFC 1701 options are in use. This
is just plain old vanilla GRE. Turning off RXCSUM/TXCSUM on the xl0 I'm
using doesn't have any effect.
Any ideas?
BMS
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