inet_net_pton() alternative for IPv6

inet_net_pton() alternative for IPv6

[Ian Pilcher]

I am searching for the best way to parse both IPv4 and IPv6 CIDR-
formatted addresses.  I have found inet_net_pton(), but it only supports
IPv4 (AF_INET) addresses.

Needless to say, this is pretty disappointing in 2022.  Is there an
alternative API that I should be using, or am I stuck writing my own?

Thanks!

-- 
========================================================================
Google                                      Where SkyNet meets Idiocracy
========================================================================

Re: inet_net_pton() alternative for IPv6

[tomas]

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On Mon, Jul 04, 2022 at 01:07:59PM -0500, Ian Pilcher via Libc-help wrote:
> I am searching for the best way to parse both IPv4 and IPv6 CIDR-
> formatted addresses.  I have found inet_net_pton(), but it only supports
> IPv4 (AF_INET) addresses.

I never tried it, but this is what my version [1] of the libc docs say:

 -- Function: int inet_pton (int AF, const char *CP, void *BUF)

     Preliminary: | MT-Safe locale | AS-Safe | AC-Safe | *Note POSIX
     Safety Concepts::.

     This function converts an Internet address (either IPv4 or IPv6)
     from presentation (textual) to network (binary) format.  AF should
     be either ‘AF_INET’ or ‘AF_INET6’, as appropriate for the type of
     address being converted.  CP is a pointer to the input string, and
     BUF is a pointer to a buffer for the result.  It is the caller’s
     responsibility to make sure the buffer is large enough.

 -- Function: const char * inet_ntop (int AF, const void *CP, char *BUF,
          socklen_t LEN)

     Preliminary: | MT-Safe locale | AS-Safe | AC-Safe | *Note POSIX
     Safety Concepts::.

     This function converts an Internet address (either IPv4 or IPv6)
     from network (binary) to presentation (textual) form.  AF should be
     either ‘AF_INET’ or ‘AF_INET6’, as appropriate.  CP is a pointer to
     the address to be converted.  BUF should be a pointer to a buffer
     to hold the result, and LEN is the length of this buffer.  The
     return value from the function will be this buffer address.

so they seem to cover your needs?

> Needless to say, this is pretty disappointing in 2022.  Is there an
> alternative API that I should be using, or am I stuck writing my own?

C'm on. Be nice :)

Cheers

[1] This is ‘The GNU C Library Reference Manual’, for Version (Debian
   glibc-doc-reference 2.31-1) of the GNU C Library.

-- 
t

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Re: inet_net_pton() alternative for IPv6

[Ian Pilcher]

On 7/4/22 13:23, tomas@tuxteam.de wrote:
> I never tried it, but this is what my version [1] of the libc docs say:
> 
>   -- Function: int inet_pton (int AF, const char *CP, void *BUF)
> 
>       Preliminary: | MT-Safe locale | AS-Safe | AC-Safe | *Note POSIX
>       Safety Concepts::.
> 
>       This function converts an Internet address (either IPv4 or IPv6)
>       from presentation (textual) to network (binary) format.  AF should
>       be either ‘AF_INET’ or ‘AF_INET6’, as appropriate for the type of
>       address being converted.  CP is a pointer to the input string, and
>       BUF is a pointer to a buffer for the result.  It is the caller’s
>       responsibility to make sure the buffer is large enough.


You're looking at the wrong function.  inet_pton() does support IPv6;
inet_net_pton() does not (even though its interface is designed in a
way that it could accomodate it).

-- 
========================================================================
Google                                      Where SkyNet meets Idiocracy
========================================================================

Re: inet_net_pton() alternative for IPv6

[tomas]

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On Tue, Jul 05, 2022 at 06:58:00PM -0500, Ian Pilcher wrote:
> On 7/4/22 13:23, tomas@tuxteam.de wrote:
> > I never tried it, but this is what my version [1] of the libc docs say:
> > 
> >   -- Function: int inet_pton (int AF, const char *CP, void *BUF)
> > 
> >       Preliminary: | MT-Safe locale | AS-Safe | AC-Safe | *Note POSIX
> >       Safety Concepts::.
> > 
> >       This function converts an Internet address (either IPv4 or IPv6)
> >       from presentation (textual) to network (binary) format.  AF should
> >       be either ‘AF_INET’ or ‘AF_INET6’, as appropriate for the type of
> >       address being converted.  CP is a pointer to the input string, and
> >       BUF is a pointer to a buffer for the result.  It is the caller’s
> >       responsibility to make sure the buffer is large enough.
> 
> 
> You're looking at the wrong function.  inet_pton() does support IPv6;
> inet_net_pton() does not (even though its interface is designed in a
> way that it could accomodate it).

I see, thanks

> -- 
> ========================================================================
> Google                                      Where SkyNet meets Idiocracy
> ========================================================================

The irony is that you are posting from... gmail :)

Cheers
-- 
t

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Re: inet_net_pton() alternative for IPv6

[Florian Weimer]

* Ian Pilcher via Libc-help:

> I am searching for the best way to parse both IPv4 and IPv6 CIDR-
> formatted addresses.  I have found inet_net_pton(), but it only
> supports IPv4 (AF_INET) addresses.

There's inet_pton, or getaddrinfo AI_NUMERICHOST if you want to produce
a full socket address (with a port number as well).

Thanks,
Florian

Re: inet_net_pton() alternative for IPv6

[Ian Pilcher]

On 7/4/22 13:34, Florian Weimer wrote:
> There's inet_pton, or getaddrinfo AI_NUMERICHOST if you want to produce
> a full socket address (with a port number as well).

I just need to parse an IP address and prefix length or network address,
in CIDR format.  Unfortunately, inet_pton() won't parse the address
portion of a CIDR address, so it looks like I'm going to have to make a
zero-terminated copy of that part of the address, just so I can pass it
to inet_pton().

-- 
========================================================================
Google                                      Where SkyNet meets Idiocracy
========================================================================

Re: inet_net_pton() alternative for IPv6

[Florian Weimer]

* Ian Pilcher:

> On 7/4/22 13:34, Florian Weimer wrote:
>> There's inet_pton, or getaddrinfo AI_NUMERICHOST if you want to produce
>> a full socket address (with a port number as well).
>
> I just need to parse an IP address and prefix length or network address,
> in CIDR format.  Unfortunately, inet_pton() won't parse the address
> portion of a CIDR address, so it looks like I'm going to have to make a
> zero-terminated copy of that part of the address, just so I can pass it
> to inet_pton().

I guess that's just living with C strings. 8-/

We have the same issue with separating IPv6 addresses from their scope
IDs, and have an internal __inet_pton_length function, which is used to
avoid that copy.  But pretty much anything that operates on C strings
could also work with an explicit length, so there's really no good
reason to start exporting __inet_pton_length, I'm afraid.

Thanks,
Florian