Date: Sat, 18 Sep 2004 14:24:41 -0700 From: Brooks Davis <brooks@one-eyed-alien.net> To: Robert Watson <rwatson@FreeBSD.org> Cc: current@FreeBSD.org Subject: Re: 5.3-RELEASE TODO Message-ID: <20040918212441.GA22566@odin.ac.hmc.edu> In-Reply-To: <Pine.NEB.3.96L.1040918134100.91851A-100000@fledge.watson.org> References: <20040918171216.GA27533@odin.ac.hmc.edu> <Pine.NEB.3.96L.1040918134100.91851A-100000@fledge.watson.org>
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[-- Attachment #1 --] On Sat, Sep 18, 2004 at 01:42:24PM -0400, Robert Watson wrote: > > On Sat, 18 Sep 2004, Brooks Davis wrote: > > > > Have you tried seeing just how many addresses you can add before > > > getifaddrs() fails to return the complete list? 128k seems like a lot, > > > but I instrumente ifconf() locally a couple of weeks ago when I first > > > became aware of this problem, and discovered that even on my notebook > > > (which has a wireless card with one IP, and an unused ethernet card) that > > > I see moderately large buffers being read from user space: > > > > > > ifconf: 16384 space > > > > Those allocations don't seem to make any sense. The actual space > > required is quite small. All you do is copy one struct ifreq out for > > each address, plus one for each interface with no addresses. The base > > size of a struct ifreq is 32 bytes and it extends to 34 for IPv6 > > addresses. The maximum size allowed by the data types is 273 (for a 255 > > byte address). Since I think IPv6 are the largest addresses used in > > practice, MAXPHYS is probably not too bad, though it does put a new cap > > on the number of interfaces at ~4k. > > > > If we want to keep kernel allocations small and allow all the itnerfaces > > to be reliably reported, we probably need to go back to my origional > > plan where we loop repeatidly. I might do it differently by allocating > > up to MAXPHYS and only reallocating if we overflow. That would avoid > > doing it twice (or more) on normal machines while still being correct. > > I'm not too worried about theory, mostly about practice. I.e., if you add > a few thousand IP addresses to a tap device, does all go happily? After adding the missing sbuf_delete(), I was able to create 2000 aliases on a vlan. I think the current practical limit is ~4090. I'm working on a new version that initially caps the allocation at MAXPHYS and then retries if it doesn't have enough space. -- Brooks -- Any statement of the form "X is the one, true Y" is FALSE. PGP fingerprint 655D 519C 26A7 82E7 2529 9BF0 5D8E 8BE9 F238 1AD4 [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQFBTKeYXY6L6fI4GtQRAvqbAKCvG89aJbqr4eVviwwt8C6gGHpVTACgzZ0R iH1SPAj3HMgUUMsyfU3nMT8= =dJDW -----END PGP SIGNATURE-----
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