Date: Thu, 16 Sep 2010 18:00:53 +0400 From: Vladimir Grigorov <vl.varlog@gmail.com> To: freebsd-net@freebsd.org Subject: Strange FreeBSD behavior when trying to forward beetween ipsec crypted gif's. May be a problem with ICMP unreach packets at all Message-ID: <273436110.20100916180053@gmail.com>
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Greetings all. I have strange problems related to passage icmp need-frag packets, and, as = result, all packets with packets length greater than output gif MTU. Network diagram: [HostA] -- (mtu 1500) --- [FW1] --- ipsec gif mtu 1280 <-gif1 -- [FW2] - gi= f0 -> ipsec gif mtu 6100 - [FW3] -(mtu 1500) - [HostB] All FW's - Freebsd hosts HostA - freebsd host HostB - Cisco 3750e switch in L3 mode HostA can reach HostB and vice versa. Ping with length above 1280 works fin= e (pmtu =3D 1280). Ping with len=3D1281 without df bit also work fine. But = ping with mtu 1281 fails.=20 Question: Why FW2 does not send ICMP need-fragment-but-DF-set message to Ho= stB ?=20 I try to permit icmp from all interfaces on FW2, explicit send unreachable = packet for all ip packets from defined source ip - nothing happens. I see i= ncreased packets counts related my source ip, but cant see responce icmps w= ith unreachable code uname -a FreeBSD fw2-mru.astrum-nival.com 8.0-RELEASE-p3 FreeBSD 8.0-RELEASE-p3 #3: = Thu Jul 1 18:24:35 MSD 2010 root@fw2-mru.astrum-nival.com:/usr/obj/usr= /src/sys/gw amd64 ifconfig gif0 gif0: flags=3D8051<UP,POINTOPOINT,RUNNING,MULTICAST> metric 0 mtu 6100 tunnel inet 217.69.143.28 --> 217.69.143.57 inet 10.192.224.5 --> 10.192.224.6 netmask 0xfffffffc=20 options=3D1<ACCEPT_REV_ETHIP_VER> ifconfig gif1 gif1: flags=3D8051<UP,POINTOPOINT,RUNNING,MULTICAST> metric 0 mtu 1280 tunnel inet 217.69.143.28 --> 88.212.205.166 inet 10.160.192.6 --> 10.160.192.5 netmask 0xfffffffc=20 options=3D1<ACCEPT_REV_ETHIP_VER> netstat -nr | grep 192.168.224 192.168.224.0/22 10.192.224.6 UG1 0 36031303 gif0 netstat -nr | grep 192.168.160. 192.168.160.0/24 10.160.192.5 UG1 0 10969867 gif1 # ipfw show 00006 10 6505 allow icmp from any to 192.168.225.1 via= gif0 00100 10524445 1225052712 allow ip from any to any via lo0 00200 0 0 deny ip from any to 127.0.0.0/8 00300 0 0 deny ip from 127.0.0.0/8 to any 00305 2054 433651 allow icmp from any to any via gif0 icmp= types 3,11 00306 0 0 allow icmp from any to 192.168.225.1 via= gif0 00310 6960 575159 nat 220 ip from table(10) to any via vla= n220 00315 1198 70832 deny ip from not me to 192.168.66.0/23 o= ut xmit vlan220 00320 6512 1611912 nat 220 ip from 192.168.66.0/23 to 192.1= 68.13.199 in recv vlan220 00400 114560294 8963623578 nat 123 ip from 192.168.196.0/24 to any = out via vlan506 00402 36831424 2199804860 nat 123 ip from 192.168.193.0/24 to any = out via vlan506 00403 153380 9265905 nat 123 ip from 192.168.197.0/24 to any = out via vlan506 00500 0 0 nat 123 ip from any to 195.211.130.9 in = via vlan506 00501 147593882 174870597871 nat 123 ip from any to 195.211.130.9 in = via vlan500 01100 0 0 allow tcp from table(21) to table(23) ds= t-port 29000 01110 0 0 deny tcp from table(22) to table(23) dst= -port 29000 01120 3 144 deny tcp from table(20) to table(23) dst= -port 29000 65530 589120438508 133855063718386 allow ip from any to any 65535 0 0 deny ip from any to any try to ping from cisco: c3750e.gldn#ping 192.168.160.248 source 192.168.225.1 repea 5 size 1281 df Type escape sequence to abort. Sending 5, 1281-byte ICMP Echos to 192.168.160.248, timeout is 2 seconds: Packet sent with a source address of 192.168.225.1=20 Packet sent with the DF bit set ..... Success rate is 0 percent (0/5) tcpdump on gif0 (large mtu before small mtu gif) [root@fw2-mru ~]# tcpdump -i gif0 -vvv -n host 192.168.225.1=20 tcpdump: listening on gif0, link-type NULL (BSD loopback), capture size 96 = bytes 17:55:54.006210 IP (tos 0x0, ttl 254, id 805, offset 0, flags [DF], proto I= CMP (1), length 1281) 192.168.225.1 > 192.168.160.248: ICMP echo request, id 161, seq 0, leng= th 1261 17:55:56.013039 IP (tos 0x0, ttl 254, id 806, offset 0, flags [DF], proto I= CMP (1), length 1281) 192.168.225.1 > 192.168.160.248: ICMP echo request, id 161, seq 1, leng= th 1261 17:55:58.015870 IP (tos 0x0, ttl 254, id 807, offset 0, flags [DF], proto I= CMP (1), length 1281) 192.168.225.1 > 192.168.160.248: ICMP echo request, id 161, seq 2, leng= th 1261 17:56:00.020833 IP (tos 0x0, ttl 254, id 808, offset 0, flags [DF], proto I= CMP (1), length 1281) 192.168.225.1 > 192.168.160.248: ICMP echo request, id 161, seq 3, leng= th 1261 17:56:02.027756 IP (tos 0x0, ttl 254, id 809, offset 0, flags [DF], proto I= CMP (1), length 1281) 192.168.225.1 > 192.168.160.248: ICMP echo request, id 161, seq 4, leng= th 1261 ^C 5 packets captured 99753 packets received by filter 0 packets dropped by kernel tcpdump on gif1 (small mtu on route to destination) (nothing) but if i omit df on cisco: [root@fw2-mru ~]# tcpdump -i gif1 -vvv -n host 192.168.225.1=20 tcpdump: listening on gif1, link-type NULL (BSD loopback), capture size 96 = bytes 17:59:03.083053 IP (tos 0x0, ttl 253, id 815, offset 0, flags [+], proto IC= MP (1), length 1276) 192.168.225.1 > 192.168.160.248: ICMP echo request, id 163, seq 0, leng= th 1256 17:59:03.083147 IP (tos 0x0, ttl 253, id 815, offset 1256, flags [none], pr= oto ICMP (1), length 25) 192.168.225.1 > 192.168.160.248: icmp 17:59:03.090882 IP (tos 0x0, ttl 253, id 816, offset 0, flags [+], proto IC= MP (1), length 1276) 192.168.225.1 > 192.168.160.248: ICMP echo request, id 163, seq 1, leng= th 1256 17:59:03.090976 IP (tos 0x0, ttl 253, id 816, offset 1256, flags [none], pr= oto ICMP (1), length 25) 192.168.225.1 > 192.168.160.248: icmp 17:59:03.097254 IP (tos 0x0, ttl 253, id 817, offset 0, flags [+], proto IC= MP (1), length 1276) 192.168.225.1 > 192.168.160.248: ICMP echo request, id 163, seq 2, leng= th 1256 17:59:03.097346 IP (tos 0x0, ttl 253, id 817, offset 1256, flags [none], pr= oto ICMP (1), length 25) 192.168.225.1 > 192.168.160.248: icmp 17:59:03.105749 IP (tos 0x0, ttl 253, id 818, offset 0, flags [+], proto IC= MP (1), length 1276) 192.168.225.1 > 192.168.160.248: ICMP echo request, id 163, seq 3, leng= th 1256 17:59:03.105844 IP (tos 0x0, ttl 253, id 818, offset 1256, flags [none], pr= oto ICMP (1), length 25) 192.168.225.1 > 192.168.160.248: icmp 17:59:03.115617 IP (tos 0x0, ttl 253, id 819, offset 0, flags [+], proto IC= MP (1), length 1276) 192.168.225.1 > 192.168.160.248: ICMP echo request, id 163, seq 4, leng= th 1256 17:59:03.115707 IP (tos 0x0, ttl 253, id 819, offset 1256, flags [none], pr= oto ICMP (1), length 25) 192.168.225.1 > 192.168.160.248: icmp e.g. destination reachable, fragmentation work, routes symmetrical. any comments ? --=20 =D1 =F3=E2=E0=E6=E5=ED=E8=E5=EC, Vladimir mailto:vl.varlog@gmail.com
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