[tor-bugs] #16674 [Tor]: Allow FQDNs ending with a single '.' in our SOCKS host name checks.

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#16674: Allow FQDNs ending with a single '.' in our SOCKS host name checks.
-----------------------------+------------------------------------
 Reporter:  yawning          |          Owner:
     Type:  defect           |         Status:  new
 Priority:  normal           |      Milestone:  Tor: 0.2.7.x-final
Component:  Tor              |        Version:  Tor: 0.2.6.2-alpha
 Keywords:  tor-core, socks  |  Actual Points:
Parent ID:                   |         Points:
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 Brought up as part of #16430.  A single `.` is allowed by RFC 3986 ("URI
 Generic Syntax") in URIs to specify that a domain name is absolute rather
 than relative.  In practice not many sites use this, but right now since
 we unilaterally reject the syntax, it breaks things.

 Relevant portion of RFC 3986:
 {{{
    Such a name consists of a sequence of domain labels separated by ".",
    each domain label starting and ending with an alphanumeric character
    and possibly also containing "-" characters.  The rightmost domain
    label of a fully qualified domain name in DNS may be followed by a
    single "." and should be if it is necessary to distinguish between
    the complete domain name and some local domain.
 }}}

 RFC 1928 specifies that all `DOMAINNAME` type addresses are `fully-
 qualified domain name`(s), so I personally think that the `.` is
 redundant, but accepting it will increase compatibility, and being
 somewhat tolerant here is a good thing.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16674>
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