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Message-ID: <4F2C01D5.5060902@earthlink.net> Date: Fri, 03 Feb 2012 10:48:37 -0500 From: Stephen Clark <sclark46@...thlink.net> To: Eric Dumazet <eric.dumazet@...il.com> CC: Linux Kernel Network Developers <netdev@...r.kernel.org> Subject: Re: route cache flush?? On 02/03/2012 10:05 AM, Eric Dumazet wrote: > Le vendredi 03 février 2012 à 09:59 -0500, Stephen Clark a écrit : > >> Hello, >> >> I have been beating my head against the wall for 2 days trying to >> figure why when I change a route and do a "ip route flush cache" >> it still takes up to a minute for packets to start using the new >> route. >> >> Is there a step I am missing? >> >> kernel is 2.6.32 >> >> > Nothing comes to mind, please share more information ? > > Sure I have a box "A" with 2 interfaces ips 2.2.2.1 and 3.3.3.1 going to another box "B" that has 3 nics 2.2.2.254 3.3.3.254 and 1.1.1.254 there is a third box "C" with ip 1.1.1.1. Box B is to simulate the net. I have 2 vpns on box A going to box C. The default rt on A is 2.2.2.254. If I don't do anything else routing wise esp packet originated on 1.1.1.1 come 3.3.3.1 on box A but the response packet from 3.3.3.1 goes out the default route. This works OK in the lab but in the field the isps generally drop packet that have a source address that doesn't match their subnet. So I have found on the net how to set up a simple rule to route packets with src address 3.3.3.1 back out that interface. $ ip r s 2.2.2.0/24 dev eth1 proto kernel scope link src 2.2.2.1 3.3.3.0/24 dev eth2 proto kernel scope link src 3.3.3.1 10.0.128.0/17 dev eth0 proto kernel scope link src 10.0.133.22 default via 2.2.2.254 dev eth1 L703103:~ $ ip r s table second default via 3.3.3.254 dev eth2 src 3.3.3.1 L703103:~ $ ip rule list 0: from all lookup local 200: from 3.3.3.1 lookup second 32766: from all lookup main 32767: from all lookup default So I run a script to disable the src route an flush the cache.$ date;sudo /usr/local/pgsql/storeproc/programs/src_rt_off.sh Fri Feb 3 10:20:16 EST 2012 --- notice the time. ++ id -un + '[' root '!=' root ']' + /sbin/ip route delete default table second + /sbin/ip rule delete table second + /sbin/ip route flush cache + /sbin/ip rule list 0: from all lookup local 32766: from all lookup main 32767: from all lookup default This is a tcpdump of the interface with 3.3.3.1 ip address - I ran the script at 10:20:16 Notice how long before response quit going out this interface and switch to the default route. I see similar behavior when I reinstall the src route and flush the cache. 10:20:19.102448 IP 3.3.3.1 > 1.1.1.1: ESP(spi=0x05690af9,seq=0x24e), length 116 10:20:19.103221 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x24e), length 116 10:20:19.498523 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x24f), length 116 10:20:19.498701 IP 3.3.3.1 > 1.1.1.1: ESP(spi=0x05690af9,seq=0x24f), length 116 10:20:30.704175 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x250), length 116 10:20:30.704357 IP 3.3.3.1 > 1.1.1.1: ESP(spi=0x05690af9,seq=0x250), length 116 10:20:34.217349 IP 3.3.3.1 > 1.1.1.1: ESP(spi=0x05690af9,seq=0x251), length 116 10:20:34.218150 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x251), length 116 10:20:34.333011 IP 3.3.3.1 > 1.1.1.1: ESP(spi=0x05690af9,seq=0x252), length 116 10:20:34.333795 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x252), length 116 10:20:40.826996 IP 3.3.3.1 > 1.1.1.1: ESP(spi=0x05690af9,seq=0x253), length 116 10:20:40.827775 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x253), length 116 10:20:41.412308 IP 3.3.3.1 > 1.1.1.1: ESP(spi=0x05690af9,seq=0x254), length 116 10:20:41.413081 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x254), length 116 10:20:41.910528 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x255), length 116 10:20:41.910711 IP 3.3.3.1 > 1.1.1.1: ESP(spi=0x05690af9,seq=0x255), length 116 10:20:42.413504 IP 3.3.3.1 > 1.1.1.1: ESP(spi=0x05690af9,seq=0x256), length 116 10:20:42.414260 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x256), length 116 10:20:43.413755 IP 3.3.3.1 > 1.1.1.1: ESP(spi=0x05690af9,seq=0x257), length 116 10:20:43.414510 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x257), length 116 10:20:44.413807 IP 3.3.3.1 > 1.1.1.1: ESP(spi=0x05690af9,seq=0x258), length 116 10:20:44.414560 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x258), length 116 10:20:49.468466 IP 3.3.3.1 > 1.1.1.1: ESP(spi=0x05690af9,seq=0x259), length 116 10:20:49.469267 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x259), length 116 10:20:49.576539 IP 3.3.3.1 > 1.1.1.1: ESP(spi=0x05690af9,seq=0x25a), length 116 10:20:49.577318 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x25a), length 116 10:20:53.116021 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x25b), length 116 10:20:53.116196 IP 3.3.3.1 > 1.1.1.1: ESP(spi=0x05690af9,seq=0x25b), length 116 10:21:04.320972 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x25c), length 116<<<<<<< 10:21:04.720342 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x25d), length 116 10:21:04.808653 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x25e), length 116 10:21:08.422372 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x25f), length 116 10:21:09.423730 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x260), length 116 10:21:10.424971 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x261), length 116 10:21:11.425469 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x262), length 116 10:21:15.525572 IP 1.1.1.1 > 3.3.3.1: ESP(spi=0x021bd1a9,seq=0x263), length 116 -- "They that give up essential liberty to obtain temporary safety, deserve neither liberty nor safety." 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