Messages in this thread | | | Subject | Re: Default gateways, dead gateway detection | From | Jim Dennis <> | Date | 24 Mar 1998 08:55:35 -0800 |
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What ever happened to this?
Chel van Gennip <linux@vangennip.nl> writes: > Tests show Linux TCP/IP does not conform the host requirements: > > RFC 1122:Requirements for Internet Hosts -- Communication Layers > When there is no route cache entry for the destination host > address (and the destination is not on the connected > network), the IP layer MUST pick a gateway from its list of > "default" gateways. The IP layer MUST support multiple > default gateways. > > When I check the code (route.h and route.c) I see there are > some performance problems if we want to confirm to this > requirement. The current code is fast, even with al large > number of routing table entry's, but there is no detection for > dead gateway's or even dead default gateway's. > > If we look at a routing table: > Destination Gateway Genmask Flags Metric Ref Use Iface > 192.1.1.0 0.0.0.0 255.255.255.0 U 0 0 37 eth0 > 127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 13 lo > 0.0.0.0 192.1.1.253 0.0.0.0 UG 0 0 0 eth0 > 0.0.0.0 192.1.1.254 0.0.0.0 UG 0 0 0 eth0 > > Linux will never use 192.1.1.254, even if 192.1.1.253 is dead. > > Wat could be done is to reorder routing table entry's with the exact same > destination whenever a gateway is dead (or at least verry quiet). > This can be done outside of the normal "fast" path so performance effects > are minimal. I think the resulting effect is enough. In this example if > there are no responses from 192.1.1.253, the table is re-aranged to: > > Destination Gateway Genmask Flags Metric Ref Use Iface > 192.1.1.0 0.0.0.0 255.255.255.0 U 0 0 37 eth0 > 127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 13 lo > 0.0.0.0 192.1.1.254 0.0.0.0 UG 0 0 0 eth0 > 0.0.0.0 192.1.1.253 0.0.0.0 UG 0 0 0 eth0 > and connections will use gw 192.1.1.254 instead of 192.1.1.253. > Chel
Was it ever fixed in 2.0.xx? Is it fixed (or obviated) in 2.1.x?
-- Jim Dennis (800) 938-4078 consulting@starshine.org Proprietor, Starshine Technical Services: http://www.starshine.org PGP 1024/2ABF03B1 Jim Dennis <jim@starshine.org> Key fingerprint = 2524E3FEF0922A84 A27BDEDB38EBB95A
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