Date: Tue, 12 Jul 2011 15:14:03 +0400 From: "Alexander V. Chernikov" <melifaro@ipfw.ru> To: Garrett Cooper <yanegomi@gmail.com> Cc: freebsd-hackers@freebsd.org Subject: Re: [PATCH] Remove dead code in netstat from route.c Message-ID: <4E1C2C7B.5050109@ipfw.ru> In-Reply-To: <CAGH67wQDZ31Qc1Yd=wOBByPSSkj01MdEZa4dVBAP8wxe6s9o0g@mail.gmail.com> References: <CAGH67wS1EQFkmCKiv-VPrJFc_JXV5oTjfmht-anqbmpibJkMfQ@mail.gmail.com> <4E1BE6D8.60805@ipfw.ru> <CAGH67wQDZ31Qc1Yd=wOBByPSSkj01MdEZa4dVBAP8wxe6s9o0g@mail.gmail.com>
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On 12.07.2011 11:10, Garrett Cooper wrote: > On Mon, Jul 11, 2011 at 11:16 PM, Alexander V. Chernikov > <melifaro@ipfw.ru> wrote: >> Garrett Cooper wrote: >>> Hi, >>> While trying to determine how to print out routes via kvm for >>> net-snmp, I noticed that there's a chunk of code from the 4.4 BSD Lite >>> days that isn't executed in netstat as NewTree is always 0. The >>> following patch removes that dead code and gets the FreeBSD source for >>> netstat more in line with NetBSD and OpenBSD's copy. >>> Thanks! >> >> Hello! >> >> This code is still working (I've tested it several months ago). Using >> RT_DUMP sysctl gives us less information than KVM, but this is much more >> better way of requesting infromation: >> KVM heavily assumes RADIX rtee is used and simply implement walking the >> tree in userland (p_tree()) which is quite hackish. Since some dynamic >> routing software can change massive amounts of data at once (BGP session >> with full-view going up/down) or physical interface with several hundred >> vlans goes up/down - requesting routing data via KVM can lead to fully >> unexpected behaviour. Calling this on regular basis on net-snmp is not >> the best thing one can do. >> >> Additionally, there can be address families where RADIX is unnecessary >> complicated since only direct key match is required (MPLS, for example). >> Moving from RADIX implementation for such family will require a lot of >> 'if (af == AF_MPLS)' code in many base userland utilities since >> assumption that RADIX is used do exists in many places, unfortunately. >> >> Requesting routes via KVM is completely undocumented and kernel >> internals dependent way. From the other side, NET_RT_DUMP sysctl is >> documented in sysctl(3) and is used by all major routing software >> (quagga, bird,openbgp). It also brings us more RADIX-dependent which >> should be avoided. > > That's a compelling argument, but why is NewTree hardwired to 0 > then (apart from the fact that kvm works with non-live kernel images)? I don't know - It was too long ago :) Walking RADIX directly gives an advantage of accessing its internal fields like "refcount" and "use" values which we are get used to see in 'netstat -rn' output, for example. > Thanks, > -Garrett >
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