Messages in this thread |  | | Date | Sun, 13 May 2001 23:26:23 +0300 (EEST) | From | Pekka Savola <> | Subject | Re: IPv6: the same address can be added multiple times |
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On Sun, 13 May 2001 kuznet@ms2.inr.ac.ru wrote: > Hello! > > > It appears you can add _exactly_ same IPv6 address on an interface many > > times: > > Yes. BTW, look here: > > kuznet@dust:~ # ip -6 a ls sit0 > 7: sit0@NONE: <NOARP,UP> mtu 1480 qdisc noqueue > inet6 ::127.0.0.1/96 scope host > inet6 ::193.233.7.100/96 scope global > inet6 ::193.233.7.100/96 scope global > > I have two equal addresses inherited from one IPv4 address > on two interfaces. Nothing illegal.
Heh, I doubt there's an RFC that says "you MUST not be able to add the same address twice to an interface". I think it's kind of taken for granted. ;-)
But it still looks dirty. Also, it's easier to add it many times by mistake; IPv4 addresses do not allow this. And as you have to remove them N times too, this may create even more confusion.
> > It looks like a check or two in kernel is missing, or is there some > > reasoning to this behaviour? > > Well, it is one of well defined approaches (unlike KAME's one). > Alternative is to implement full set of options NLM_F_* like used > in IPv4 routing to block undefined cases. In IPv6 flags are hardwired > to NLM_F_CREATE|NLM_F_APPEND both for addresses and routes.
Well, I can't really formulate an expert opinion as I'm not intimate how this works on Linux, but I think KAME adds addresses to a structure where duplicates aren't possible.
Also, what would be the other well defined approaches? Quickly I can think of only two, if "only one same address" isn't possible: 1) never allow any address to be added at all 2) no significant restrictions (==this)
I don't think the former is what people want either ;-)
Please Cc:. -- Pekka Savola "Tell me of difficulties surmounted, Netcore Oy not those you stumble over and fall" Systems. Networks. Security. -- Robert Jordan: A Crown of Swords
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