Bug#468801: libc6: RFC3484 scoping rules should only affect IPv6, not IPv4

[Aurelien Jarno <aurelien@aurel32.net>]

Remi Denis-Courmont a écrit :
> Package: libc6
> Version: 2.7-9
> Severity: normal
> Tags: patch
> 
> 
> 	Hello,
> 
> Rule 2 of the Destination Address Selection algorithm in RFC3484
> specifies:
> 
> | Rule 2:  Prefer matching scope.
> | If Scope(DA) = Scope(Source(DA)) and Scope(DB) <> Scope(Source(DB)),
> | then prefer DA.  Similarly, if Scope(DA) <> Scope(Source(DA)) and
> | Scope(DB) = Scope(Source(DB)), then prefer DB.
> 
> This rule makes lots of sense for IPv6 addresses - hosts should not try
> to use link-local destinations with global source addresses or
> vice-versa.
> 
> However, glibc extends this rule to IPv4 as well: private RFC1918 IPv4
> addresses are taken as a different scope from public IPv6 addresses.

Note that it is note a glibc extension. It is defined in the RFC3484:

|  IPv4 addresses are assigned scopes as follows.  IPv4 auto-
|  configuration addresses [9], which have the prefix 169.254/16, are
|  assigned link-local scope.  IPv4 private addresses [12], which have
|  the prefixes 10/8, 172.16/12, and 192.168/16, are assigned site-local
|  scope.  IPv4 loopback addresses [12, section 4.2.2.11], which have
|  the prefix 127/8, are assigned link-local scope (analogously to the
|  treatment of the IPv6 loopback address [11, section 4]).  Other IPv4
|  addresses are assigned global scope.

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