IPv6 Patch

dormando dormando at rydia.net
Thu Jan 31 22:03:56 UTC 2008

Brian Aker wrote:
> Hi!
> On Jan 30, 2008, at 12:03 PM, Tomash Brechko wrote:
>> The DNS fear is stretched too far.  You are basically saying that one
>> should never ever bind to site-local address because there's a
>> possibility that it is visible form the outside, and is not protected
> Because bad setups never occur with DNS? A sysadmin never binds a public 
> address to an internal and external device, not realizing that is some 
> program comes along it will be exposed to the outside world?
> Memcached has no password protection, so doesn't it make sense to have 
> an ounce more protection? (and it is not like memcached is designed to 
> be a mutli-listener... and getaddrinfo() returns even junk like AF_UNIX 
> on older glibc).
> I can patch it to bail on multi available, but that will cause older 
> glibc() to toss any binding (and the FreeBSD 4.x guys will be submitting 
> a patch later to just ignore all all entries past the first when they 
> hit this problem).


getaddrinfo() returns a list.
If you're setting the AI_ADDRCONFIG flag it'll at least only return 
addresses which are available on the interface (ipv6 only, etc).

But if a hostname returns multiple addresses (getaddrinfo(NULL, ...)) 
and the host might be a dedicated server with a private net, it'll bind 
to both the public address and private address?

I'm not entirely clear on the conditions where getaddrinfo would suggest 
you bind to both a public and a private address, unless you're binding 
to INADDR_ANY, which I _believe_ is the present default for memcached, 
and will certainly bind to any public IP if it exists.

Could someone perhaps clear it up a bit? Is this identical or different 
to the present IPv4 default behavior, and if this is going to be 
different, we might need a new option to accomodate. IE; if someone 
wants to bind to a private-network in IPv4 land, they presently use -l, 
but if you're binding by hostname in IPv6, it makes sense (to me) to 
continue to allow someone to select a private address.

Unless I'm completely off here :P


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