Date: Thu, 10 May 2018 20:19:16 -0700 (PDT) From: "Rodney W. Grimes" <freebsd@pdx.rh.CN85.dnsmgr.net> To: =?UTF-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no> Cc: rgrimes@freebsd.org, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r333476 - head/sys/net Message-ID: <201805110319.w4B3JGBv073462@pdx.rh.CN85.dnsmgr.net> In-Reply-To: <86h8nfvtbk.fsf@next.des.no>
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[ Charset UTF-8 unsupported, converting... ] > "Rodney W. Grimes" <freebsd@pdx.rh.CN85.dnsmgr.net> writes: > > I do no need or want these routes created by this mechanism on my > > FreeBSD based routers, they only ever existed originally to use the > > MTU of the lo0 interface for things that wrongly open an IP address of > > an interface rather than 127.0.0.1. > > I'm not sure I understand enough of this to make an informed decision. > Are you saying they serve no practical purpose ever on current systems? > > These are the entries that route all traffic to any of our own addresses > over lo0, right? Like the bottom four here? Correct. > des@hive ~% netstat -4rn | grep -w lo0 > 127.0.0.1 link#2 UH lo0 > 192.168.144.15 link#1 UHS lo0 > 192.168.144.16 link#1 UHS lo0 > 192.168.144.19 link#1 UHS lo0 > 192.168.144.30 link#1 UHS lo0 > > I'm going to try a kernel with that code #ifdefed out... We did this back in the day so if you make a connection to your own IP (your 4 addresses above) then you use the MTU of lo0, which is usually 16k, instead of the MTU of the interface, which is usually 1500, or back in the day of SLIP was often 296. Eugene Grosbein says there is some use case for it where he has lots of tunX devices, but I just can not seem to understand why or what it is that he is doing that requires these routes. IIRC Linux has never had these routes. If you go back in the history of svn and read whey this was originally added it was to compensate for the fact that you lost the /etc/rc installed route if you did an if down/up, which is actually expected behavior, you loose ALL routes associtated with the IP of an interface if you down it. The CURRENT code makes it possible for you to ping the IP of a DOWNED interface due to this now silly lo0 route, just more demonstration of how wrong this idea is. This was caused by the addition of pinning these routes so that they stay in effect even when you down the interface. -- Rod Grimes rgrimes@freebsd.org
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