Re: Nmap's nc version fails to correctly do IPv4 fallback

[Daniel Miller <bonsaiviking () gmail com>]

Quanah,

Thank you for bringing this up. We previously debated this issue and were
on the brink of accepting a patch to implement this sort of fallback in
December 2013 [1]. I'm not really sure what happened there, but I will look
into it and see if we can get this implemented for the next release.

As obvious workarounds, you can explicitly request IPv6 or IPv4 with the -6
or -4 options respectively or use explicit numeric addresses.

Dan

[1] http://seclists.org/nmap-dev/2013/q4/269

On Tue, Nov 18, 2014 at 12:51 PM, Quanah Gibson-Mount <quanah () zimbra com>
wrote:

> Unlike the OpenBSD "nc", the version from nmap fails to correctly fall
> back to ipv4 if it is unable to connect to the ipv6 address of a system.
>
> Using OpenBSD "nc":
>
> [zimbra@zre-ldap003 ~]$ nc -v localhost 7171
> nc: connect to localhost port 7171 (tcp) failed: Connection refused
> Connection to localhost 7171 port [tcp/*] succeeded!
>
> Using nmap's nc:
> nc: connect to localhost port 7171 (tcp) failed: Connection refused
>
> And then no fallback.  This is problematic in particular with "localhost",
> where most systems now have:
>
> 127.0.0.1   localhost localhost.localdomain localhost4
> localhost4.localdomain4
> ::1         localhost localhost.localdomain localhost6
> localhost6.localdomain6
>
> --Quanah
>
> --
> Quanah Gibson-Mount
> Platform Architect
> Zimbra, Inc
> --------------------
> Zimbra ::  the leader in open source messaging and collaboration
>
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