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|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<head>
<meta name="generator" content=
"HTML Tidy for FreeBSD (vers 7 December 2008), see www.w3.org">
<title>libcidr - Code Documentation</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="Generator" content="Codelibrary DTD DSSSL">
<style type="text/css" media="all">
@import "codelibrary-html.css";
</style>
</head>
<body>
<div class="geninfo">
<h1 id="geninfo">Summary</h1>
<p>libcidr is a library to make it easier to handle IP addresses and
blocks, and manipulate them in various ways.</p>
<p>The core of the library is a pair of functions that take a human
readable string and turn it into our internal representation of a CIDR
address block (<a href="#CIDR-FROM-STR">cidr_from_str()</a> ), and one
to take that internal representation and turn it into a human-readable
string (<a href="#CIDR-TO-STR">cidr_to_str()</a> ). There are a large
number of options for how to format that string, as well.</p>
<p>Additionally, there are functions to compare different CIDR blocks,
to determine if they're equal, or if one is contained within the
other. This functionality can be useful for writing access-control
code, or client-dependant configuration, or similar things. There are
functions to manipulate address blocks and determine attributes of
them, like network/broadcast addresses, the range of host addresses,
the number of available host addresses, etc. There are functions to
split a CIDR block into the two smaller blocks it contains, or to
derive the parent block that it is itself contained within. And there
are functions to translate to and from in_addr-type structures, which
the operating system commonly uses to represent addresses for handle
socket connections and so forth.</p>
<p>In short, just about anything you might do in a program with IP
addressing, whether referring to individual hosts, or to any sized
subnets, libcidr is designed to simplify handling. It's not a DNS
library, nor is it a socket abstraction layer. It's just a set of
functions for manipulating raw IP addresses in various ways.</p>
<p>The functions generally follow standard C conventions. They tend to
return 0 or a pointer when acting properly, and -1 or NULL when
something went wrong (unless the function usage suggests other
returns, of course, as in <a href=
"#CIDR-GET-PFLEN">cidr_get_pflen()</a> ). They set errno when
returning an error; the error codes each function can return are
documented with the function.</p>
<p>libcidr doesn't use any threading itself. It should, however, be
safe to use in any threaded program if used sensibly. Only a very few
functions use static strings, and those that do (<a href=
"#CIDR-VERSION">cidr_version()</a> and <a href=
"#CIDR-NUMADDR">cidr_numaddr()</a> and its related functions being the
only ones I can think of) tend to be constant strings as well, so they
wouldn't be changing. Of course, you don't want to <a href=
"#CIDR-FREE">cidr_free()</a> a <a href="#CIDR-ADDR">CIDR</a> in one
thread while you're still using it in another, but if you do, it's not
libcidr's fault.</p>
<p>For the current version or any extra information, see the libcidr
project homepage, at
<http://www.over-yonder.net/~fullermd/projects/libcidr>.</p>
<p>This reference manual is build using the codelibrary SGML DTD,
which is specifically designed for documenting libraries. See the
codelibrary homepage at
<http://www.over-yonder.net/~fullermd/projects/sgml/codelibrary>
for more details on it.</p>
</div>
<div class="contents">
<h1>Contents</h1>
<h2><a href="#datastructs">Data structures:</a></h2>
<ul>
<li class="listlist"><a href="#CIDR-ADDR">CIDR</a>
<em>(Internal)</em></li>
</ul>
<h2><a href="#functions">Functions:</a></h2>
<ul>
<li class="listlist"><a href=
"#CIDR-ADDR-BROADCAST">cidr_addr_broadcast()</a></li>
<li class="listlist"><a href=
"#CIDR-ADDR-HOSTMAX">cidr_addr_hostmax()</a></li>
<li class="listlist"><a href=
"#CIDR-ADDR-HOSTMIN">cidr_addr_hostmin()</a></li>
<li class="listlist"><a href=
"#CIDR-ADDR-NETWORK">cidr_addr_network()</a></li>
<li class="listlist"><a href="#CIDR-ALLOC">cidr_alloc()</a></li>
<li class="listlist"><a href=
"#CIDR-CONTAINS">cidr_contains()</a></li>
<li class="listlist"><a href="#CIDR-DUP">cidr_dup()</a></li>
<li class="listlist"><a href="#CIDR-EQUALS">cidr_equals()</a></li>
<li class="listlist"><a href="#CIDR-FREE">cidr_free()</a></li>
<li class="listlist"><a href=
"#CIDR-FROM-INADDR">cidr_from_inaddr()</a></li>
<li class="listlist"><a href=
"#CIDR-FROM-IN6ADDR">cidr_from_in6addr()</a></li>
<li class="listlist"><a href=
"#CIDR-FROM-STR">cidr_from_str()</a></li>
<li class="listlist"><a href=
"#CIDR-GET-ADDR">cidr_get_addr()</a></li>
<li class="listlist"><a href=
"#CIDR-GET-MASK">cidr_get_mask()</a></li>
<li class="listlist"><a href=
"#CIDR-GET-PFLEN">cidr_get_pflen()</a></li>
<li class="listlist"><a href=
"#CIDR-GET-PROTO">cidr_get_proto()</a></li>
<li class="listlist"><a href=
"#CIDR-IS-V4MAPPED">cidr_is_v4mapped()</a></li>
<li class="listlist"><a href=
"#CIDR-NET-SUBNETS">cidr_net_subnets()</a></li>
<li class="listlist"><a href=
"#CIDR-NET-SUPERNET">cidr_net_supernet()</a></li>
<li class="listlist"><a href="#CIDR-NUMADDR">cidr_numaddr()</a></li>
<li class="listlist"><a href=
"#CIDR-NUMADDR-PFLEN">cidr_numaddr_pflen()</a></li>
<li class="listlist"><a href="#CIDR-NUMHOST">cidr_numhost()</a></li>
<li class="listlist"><a href=
"#CIDR-NUMHOST-PFLEN">cidr_numhost_pflen()</a></li>
<li class="listlist"><a href=
"#CIDR-TO-INADDR">cidr_to_inaddr()</a></li>
<li class="listlist"><a href=
"#CIDR-TO-IN6ADDR">cidr_to_in6addr()</a></li>
<li class="listlist"><a href="#CIDR-TO-STR">cidr_to_str()</a></li>
<li class="listlist"><a href="#CIDR-VERSION">cidr_version()</a></li>
</ul>
</div>
<div class="datastructs">
<h1 id="datastructs">Data structures</h1>
<ul>
<li id="CIDR-ADDR">
<span class="structdef">CIDR: A single CIDR-format IP block</span>
<p><em class="privdata">This datatype is intended for internal use
only</em></p>
<ul>
<li>
<div class="note">
<p>Note:</p>
<p>Use the <a href="#CIDR-FREE">cidr_free()</a> function to
free the memory associated with this datatype, and the
<a href="#CIDR-ALLOC">cidr_alloc()</a> function to allocate
and initialize the structure.</p>
</div>
</li>
<li>Members:
<ul>
<li><span class="memberdef">int version:</span> The
structure version. This is reserved for future use, and put
in to hold its place at the start of the array.</li>
<li><span class="memberdef">uint8_t addr[16]:</span> The 16
octets that make up an IP address. For v6 addresses, all are
used. For v4 addresses, only the last 4 are really used. The
prior 2 octets are filled in with all-ones, so that the
internal representation matches the v4-compat IPv6
addressing block. This is useful when, for instance, using
<a href="#CIDR-TO-IN6ADDR">cidr_to_in6addr()</a> , in that
it gives you the expected result.</li>
<li><span class="memberdef">uint8_t mask[16]:</span> The 16
octets that make up an IP netmask. For v4 addresses, only
the last 4 are really used; the rest are intialized to
all-bits-one however, which is correct in spirit.</li>
<li><span class="memberdef">int proto:</span> The protocol
the address described is. Currently possible values are
CIDR_IPV4 and CIDR_IPV6. I think that's pretty
self-explanatory.</li>
</ul>
</li>
</ul>
</li>
</ul>
</div>
<div class="functions">
<h1 id="functions">Functions</h1>
<ul>
<li id="CIDR-ADDR-BROADCAST">
<span class="funcdef">cidr_addr_broadcast(): Find the broadcast
address</span>
<ul>
<li>Summary:
<p>Generate a <a href="#CIDR-ADDR">CIDR</a> structure
describing the broadcast address of the passed-in
netblock.</p>
<p>Note that using this with an IPv6 netblock is technically
asking for something that doesn't exist, since IPv6 doesn't
have subnet broadcast addresses. This function will still
return the all-1's address though, on the assumption that if
you're asking the question, it's the answer you want.</p>
<p>An additional somewhat specialized case is that of an IPv4
/31 or IPv6 /127. Depending on your interpretation and usage,
this is either a useless subnet since it only contains network
and broadcast and no hosts, or a subnet that holds 2 hosts
with neither network or broadcast address (commonly used for
point-to-point links). As a result, <a href=
"#CIDR-ADDR-BROADCAST">cidr_addr_broadcast()</a> and <a href=
"#CIDR-ADDR-NETWORK">cidr_addr_network()</a> will give answers
as if it were a host-less subnet, while <a href=
"#CIDR-ADDR-HOSTMAX">cidr_addr_hostmax()</a> and <a href=
"#CIDR-ADDR-HOSTMIN">cidr_addr_hostmin()</a> will answer as
though it were a 2-host subnet. It can be seen as a little
strange for <a href=
"#CIDR-ADDR-BROADCAST">cidr_addr_broadcast()</a> and <a href=
"#CIDR-ADDR-HOSTMAX">cidr_addr_hostmax()</a> to give the same
answer, but as above, libcidr assumes that if you ask the
question, you want the answer that makes sense in that
context.</p>
<p>Similar caveats apply to calling these on a v4 /32 or v6
/128. Ask a silly question, get a silly answer :)</p>
<p>The returned structure should be cleaned up using <a href=
"#CIDR-FREE">cidr_free()</a> .</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* addr:</span> A <a href="#CIDR-ADDR">CIDR</a> structure
describing an arbitrary netblock.</li>
</ul>
</li>
<li>Returns:
<p><a href="#CIDR-ADDR">CIDR</a> *</p>
<p>Returns a pointer to a <a href="#CIDR-ADDR">CIDR</a>
structure describing the broadcast address on success. Returns
NULL on failure.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>EFAULT</dt>
<dd>Given NULL</dd>
</dl>
</li>
<li>
<div class="note">
<p>Note:</p>
<p><a href=
"#CIDR-ADDR-BROADCAST">cidr_addr_broadcast()</a> can
also fail and set errno for any of the reasons listed
for <a href="#CIDR-ALLOC">cidr_alloc()</a> .</p>
</div>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-ADDR-HOSTMAX">
<span class="funcdef">cidr_addr_hostmax(): Find the highest host
address</span>
<ul>
<li>Summary:
<p>Generate a <a href="#CIDR-ADDR">CIDR</a> structure
describing the highest-numbered address available for a host
IP in the given netblock.</p>
<p>See the discussion under <a href=
"#CIDR-ADDR-BROADCAST">cidr_addr_broadcast()</a> concerning
near- amd maximal-prefix-length blocks for edge case
details.</p>
<p>The returned structure should be cleaned up using <a href=
"#CIDR-FREE">cidr_free()</a> .</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* addr:</span> A <a href="#CIDR-ADDR">CIDR</a> structure
describing an arbitrary netblock.</li>
</ul>
</li>
<li>Returns:
<p><a href="#CIDR-ADDR">CIDR</a> *</p>
<p>Returns a pointer to a <a href="#CIDR-ADDR">CIDR</a>
structure describing the max host address on success. Returns
NULL on failure.</p>
</li>
<li>Error codes:
<ul>
<li>
<div class="note">
<p>Note:</p>
<p><a href="#CIDR-ADDR-HOSTMAX">cidr_addr_hostmax()</a>
can fail and set errno for any of the reasons listed for
<a href="#CIDR-ADDR-BROADCAST">cidr_addr_broadcast()</a>
.</p>
</div>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-ADDR-HOSTMIN">
<span class="funcdef">cidr_addr_hostmin(): Find the lowest host
address</span>
<ul>
<li>Summary:
<p>Generate a <a href="#CIDR-ADDR">CIDR</a> structure
describing the lowest-numbered address available for a host IP
in the given netblock.</p>
<p>See the discussion under <a href=
"#CIDR-ADDR-BROADCAST">cidr_addr_broadcast()</a> concerning
near- amd maximal-prefix-length blocks for edge case
details.</p>
<p>The returned structure should be cleaned up using <a href=
"#CIDR-FREE">cidr_free()</a> .</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* addr:</span> A <a href="#CIDR-ADDR">CIDR</a> structure
describing an arbitrary netblock.</li>
</ul>
</li>
<li>Returns:
<p><a href="#CIDR-ADDR">CIDR</a> *</p>
<p>Returns a pointer to a <a href="#CIDR-ADDR">CIDR</a>
structure describing the min host address on success. Returns
NULL on failure.</p>
</li>
<li>Error codes:
<ul>
<li>
<div class="note">
<p>Note:</p>
<p><a href="#CIDR-ADDR-HOSTMIN">cidr_addr_hostmin()</a>
can fail and set errno for any of the reasons listed for
<a href="#CIDR-ADDR-NETWORK">cidr_addr_network()</a>
.</p>
</div>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-ADDR-NETWORK">
<span class="funcdef">cidr_addr_network(): Find the network
address</span>
<ul>
<li>Summary:
<p>Generate a <a href="#CIDR-ADDR">CIDR</a> structure
describing the network address of the passed-in netblock.</p>
<p>See the discussion under <a href=
"#CIDR-ADDR-BROADCAST">cidr_addr_broadcast()</a> concerning
near- amd maximal-prefix-length blocks for edge case
details.</p>
<p>The returned structure should be cleaned up using <a href=
"#CIDR-FREE">cidr_free()</a> .</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* addr:</span> A <a href="#CIDR-ADDR">CIDR</a> structure
describing an arbitrary netblock.</li>
</ul>
</li>
<li>Returns:
<p><a href="#CIDR-ADDR">CIDR</a> *</p>
<p>Returns a pointer to a <a href="#CIDR-ADDR">CIDR</a>
structure describing the network address on success. Returns
NULL on failure.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>EFAULT</dt>
<dd>Given NULL</dd>
</dl>
</li>
<li>
<div class="note">
<p>Note:</p>
<p><a href="#CIDR-ADDR-NETWORK">cidr_addr_network()</a>
can also fail and set errno for any of the reasons
listed for <a href="#CIDR-ALLOC">cidr_alloc()</a> .</p>
</div>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-ALLOC">
<span class="funcdef">cidr_alloc(): Create a <a href=
"#CIDR-ADDR">CIDR</a></span>
<ul>
<li>Summary:
<p>Allocate memory for a <a href="#CIDR-ADDR">CIDR</a>
structure and initialize the necessary pieces.</p>
<p>The returned structure should be cleaned up using <a href=
"#CIDR-FREE">cidr_free()</a> .</p>
<p>Note that you should probably never need to call this
function yourself; you'll generally get your <a href=
"#CIDR-ADDR">CIDR</a> structures as a return from a function
like <a href="#CIDR-FROM-STR">cidr_from_str()</a> or <a href=
"#CIDR-FROM-INADDR">cidr_from_inaddr()</a> .</p>
</li>
<li>Arguments:
<ul>
<li>None</li>
</ul>
</li>
<li>Returns:
<p><a href="#CIDR-ADDR">CIDR</a> *</p>
<p>Returns a pointer to an initialized <a href=
"#CIDR-ADDR">CIDR</a> structure on success. Returns NULL on
failure.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>ENOMEM</dt>
<dd><em class="funcname">malloc()</em> failed</dd>
</dl>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-CONTAINS">
<span class="funcdef">cidr_contains(): Compare netblocks</span>
<ul>
<li>Summary:
<p>This function is passed two <a href="#CIDR-ADDR">CIDR</a>
structures describing a pair of netblocks. It then determines
if the latter is wholly contained within the former.</p>
<p>A common use-case of this will generally involve the second
"block" actually being a host (/32 or /128) address, as when
you're implementing ACL's. But that's really just a specific
case of the second block being any other size; there's nothing
special or magical about it. As far as libcidr is concerned,
they're just two netblocks.</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* big:</span> The netblock which may (or may not) contain
the second arg.</li>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* little:</span> The netblock which may (or may not) be
contained within the first arg.</li>
</ul>
</li>
<li>Returns:
<p>int</p>
<p>Returns 0 if little is wholly contained within big. Returns
-1 if it's not, or if an error occured.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>0</dt>
<dd>No error (little not in big)</dd>
</dl>
</li>
<li>
<dl>
<dt>EFAULT</dt>
<dd>Passed NULL</dd>
</dl>
</li>
<li>
<dl>
<dt>EINVAL</dt>
<dd>Invalid argument</dd>
</dl>
</li>
<li>
<dl>
<dt>ENOENT</dt>
<dd>Internal error (shouldn't happen)</dd>
</dl>
</li>
<li>
<dl>
<dt>EPROTO</dt>
<dd>Protocols don't match</dd>
</dl>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-DUP">
<span class="funcdef">cidr_dup(): Duplicate a netblock</span>
<ul>
<li>Summary:
<p>Allocate a <a href="#CIDR-ADDR">CIDR</a> , and fill it in
with a duplicate of the information given.</p>
<p>The returned structure should be cleaned up using <a href=
"#CIDR-FREE">cidr_free()</a> .</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* src:</span> A <a href="#CIDR-ADDR">CIDR</a> structure to
be copied.</li>
</ul>
</li>
<li>Returns:
<p><a href="#CIDR-ADDR">CIDR</a> *</p>
<p>Returns a <a href="#CIDR-ADDR">CIDR</a> struct containing a
copy of src. Returns NULL on failure.</p>
</li>
<li>Error codes:
<ul>
<li>
<div class="note">
<p>Note:</p>
<p><a href="#CIDR-DUP">cidr_dup()</a> can fail and set
errno for any of the reasons listed for <a href=
"#CIDR-ALLOC">cidr_alloc()</a> .</p>
</div>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-EQUALS">
<span class="funcdef">cidr_equals(): Compare two blocks for
equality</span>
<ul>
<li>Summary:
<p>This function is passed two <a href="#CIDR-ADDR">CIDR</a>
structures describing a pair of netblocks. It checks to see if
they happen to describe the same netblock.</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* one:</span> One netblock.</li>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* two:</span> Another netblock.</li>
</ul>
</li>
<li>Returns:
<p>int</p>
<p>Returns 0 if the two <a href="#CIDR-ADDR">CIDR</a> structs
describe the same netblock. Returns -1 otherwise.</p>
</li>
</ul>
</li>
<li id="CIDR-FREE">
<span class="funcdef">cidr_free(): Free a <a href=
"#CIDR-ADDR">CIDR</a> structure.</span>
<ul>
<li>Summary:
<p>Takes a <a href="#CIDR-ADDR">CIDR</a> structure and
<em class="funcname">free()</em> 's all its component
parts.</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef"><a href="#CIDR-ADDR">CIDR</a> *
tofree:</span> A single <a href="#CIDR-ADDR">CIDR</a>
structure which has outlived its usefulness.</li>
</ul>
</li>
<li>Returns:
<p>void</p>
</li>
</ul>
</li>
<li id="CIDR-FROM-INADDR">
<span class="funcdef">cidr_from_inaddr(): Parse a struct
in_addr</span>
<ul>
<li>Summary:
<p>Takes a populated struct in_addr, as you'd get from
<em class="funcname">accept()</em> or <em class=
"funcname">getaddrinfo()</em> or similar functions. Parses it
out and generates a <a href="#CIDR-ADDR">CIDR</a> structure
based on it. Note that an in_addr only contains a host
address, so the netmask is initialized to all-1's (/32).</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const struct in_addr *
uaddr:</span> A populated struct in_addr, from whatever
source obtained.</li>
</ul>
</li>
<li>Returns:
<p><a href="#CIDR-ADDR">CIDR</a> *</p>
<p>Returns a pointer to a populated <a href=
"#CIDR-ADDR">CIDR</a> containing the address in the passed-in
struct in_addr. The netmask is initialized to all-1's, and the
protocol to IPv4. Use <a href="#CIDR-FREE">cidr_free()</a> to
free the structure when you're finished with it. Returns NULL
on error.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>EFAULT</dt>
<dd>Passed NULL</dd>
</dl>
</li>
<li>
<div class="note">
<p>Note:</p>
<p><a href="#CIDR-FROM-INADDR">cidr_from_inaddr()</a>
can also fail and set errno for any of the reasons
listed for <a href="#CIDR-ALLOC">cidr_alloc()</a> .</p>
</div>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-FROM-IN6ADDR">
<span class="funcdef">cidr_from_in6addr(): Parse a struct
in6_addr</span>
<ul>
<li>Summary:
<p>Takes a populated struct in6_addr, as you'd get from
<em class="funcname">accept()</em> or <em class=
"funcname">getaddrinfo()</em> or similar functions. Parses it
out and generates a <a href="#CIDR-ADDR">CIDR</a> structure
based on it. Note that a in6_addr only contains a host
address, so the netmask is initialized to all-1's (/128).</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const struct in6_addr *
uaddr:</span> A populated struct in6_addr, from whatever
source obtained.</li>
</ul>
</li>
<li>Returns:
<p><a href="#CIDR-ADDR">CIDR</a> *</p>
<p>Returns a pointer to a populated <a href=
"#CIDR-ADDR">CIDR</a> containing the address in the passed-in
struct in6_addr. The netmask is initialized to all-1's, and
the protocol to IPv6 (though it may contain an IPv4-mapped
address). Use <a href="#CIDR-FREE">cidr_free()</a> to free the
structure when you're finished with it. Returns NULL on
error.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>EFAULT</dt>
<dd>Passed NULL</dd>
</dl>
</li>
<li>
<div class="note">
<p>Note:</p>
<p><a href="#CIDR-FROM-INADDR">cidr_from_inaddr()</a>
can also fail and set errno for any of the reasons
listed for <a href="#CIDR-ALLOC">cidr_alloc()</a> .</p>
</div>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-FROM-STR">
<span class="funcdef">cidr_from_str(): Parse a human-readable
string</span>
<ul>
<li>Summary:
<p>Takes in a netblock description as a human-readable string,
and creates a <a href="#CIDR-ADDR">CIDR</a> structure from
it.</p>
<p>This is probably the most intricate function in the
library. It accepts addresses in "address/mask" format.
'address' is an IP address in valid written form. For IPv4,
it's 1 through 4 period-separated pieces, expressed in octal,
hex, or decimal, with the last octet being treated as an 8,
16, 24, or 32-bit quantity depending on whether there are 4,
3, 2, or 1 pieces given (respectively). Of course, you're nuts
for using that flexibility. For IPv6, it's nice and simple; 8
colon-separated double-octets, excepting that the last 4
octets can be expressed as a 4-piece dotted-decimal, like an
IPv4 address (the full flexibility of the IPv4 parsing engine
is not available, however; intentionally, though that may
change if necessary). 'mask' can be either a prefix length
(/0-/32 for IPv4, /0-/128 for IPv6), or a netmask written in
the standard form for the address family.</p>
<p>IPv6 addresses can be specified in fully expanded form, or
with ::-style contraction. IPv4-mapped IPv6 addresses
(::ffff:a.b.c.d), will be treated as IPv6 addresses. The mask
can be left off, in which case addresses are treated as host
addresses (/32 or /128, depending on address family).</p>
<p>Also, <a href="#CIDR-FROM-STR">cidr_from_str()</a> will
parse DNS PTR-record-style address formats. That is,
representations like "4.3.2.1.in-addr.arpa" for IPv4, and an
extremely long and annoying form ending in .ip6.arpa for IPv6.
<a href="#CIDR-FROM-STR">cidr_from_str()</a> also understands
the deprecated RFC1886 form of IPv6 PTR records, which ends in
.ip6.int, though <a href="#CIDR-TO-STR">cidr_to_str()</a> will
only generate the current RFC3152-style .ip6.arpa version.
Note also that while <a href="#CIDR-TO-STR">cidr_to_str()</a>
treats all addresses as host addresses when building the PTR
string (ignoring the netmask), <a href=
"#CIDR-FROM-STR">cidr_from_str()</a> will fill in the netmask
bits as appropriate for the string given; any octets (or
half-octets, in the IPv6 form) that are left off the beginning
will have their netmask bits set to 0.</p>
<p>It's not the intention of the author that this function
necessarily be able to decipher any possible address format.
However, the capabilities given should parse any rational
address specification, and many irrational ones (like hex/oct
and collapsed v4 addresses). The intention is rather to
support the ways the addresses and netmasks are commonly
written and read, so that a human-readable form can quickly be
transformed into a format that libcidr can then use in its
various ways, whether through comparing addresses with
functions like <a href="#CIDR-CONTAINS">cidr_contains()</a> ,
or generating references and stats about a netblock with
functions like <a href=
"#CIDR-ADDR-BROADCAST">cidr_addr_broadcast()</a> and <a href=
"#CIDR-NUMHOST">cidr_numhost()</a> , or simply spitting it out
in different human-readable forms with <a href=
"#CIDR-TO-STR">cidr_to_str()</a> .</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const char * addr:</span> A string
containing some human-readable IP block.</li>
</ul>
</li>
<li>Returns:
<p><a href="#CIDR-ADDR">CIDR</a> *</p>
<p>Returns a pointer to a populated <a href=
"#CIDR-ADDR">CIDR</a> describing (hopefully) the block you
talked about in the string. Use <a href=
"#CIDR-FREE">cidr_free()</a> to free the structure when you're
finished with it. Returns NULL on error.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>EFAULT</dt>
<dd>Passed NULL</dd>
</dl>
</li>
<li>
<dl>
<dt>EINVAL</dt>
<dd>Can't parse the input string</dd>
</dl>
</li>
<li>
<dl>
<dt>ENOENT</dt>
<dd>Internal error (shouldn't happen)</dd>
</dl>
</li>
<li>
<div class="note">
<p>Note:</p>
<p><a href="#CIDR-FROM-STR">cidr_from_str()</a> can also
fail and set errno for any of the reasons listed for
<a href="#CIDR-ALLOC">cidr_alloc()</a> or <a href=
"#CIDR-GET-PFLEN">cidr_get_pflen()</a> .</p>
</div>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-GET-ADDR">
<span class="funcdef">cidr_get_addr(): Return address bits</span>
<ul>
<li>Summary:
<p>Return the address bits which compose the address. This
should be used in preference to simply referencing inside the
<a href="#CIDR-ADDR">CIDR</a> manually in external code, since
the structure might change on you.</p>
<p>Generally, if you think you need to call this, you should
probably rethink what you're doing. Most of the time, one of
the formatted outputs from <a href=
"#CIDR-TO-STR">cidr_to_str()</a> or one of the manipulation
functions like <a href=
"#CIDR-ADDR-HOSTMIN">cidr_addr_hostmin()</a> is what you want.
Still, there are times when you're interesting in manipulating
the address by yourself as a bunch of binary bits (the
cidrcalc example program does this), so this function should
be used instead of groping around in the structure
manually.</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* addr:</span> An arbitrary netblock.</li>
</ul>
</li>
<li>Returns:
<p>uint8_t *</p>
<p>Returns a pointer to an 16-element array of uint8_t's
representing the address. This array must be <em class=
"funcname">free()</em> 'd when you're through with it. Returns
NULL on error.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>EFAULT</dt>
<dd>Passed NULL</dd>
</dl>
</li>
<li>
<dl>
<dt>ENOMEM</dt>
<dd><em class="funcname">malloc()</em> failed</dd>
</dl>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-GET-MASK">
<span class="funcdef">cidr_get_mask(): Return netmask bits</span>
<ul>
<li>Summary:
<p>Return the netmask bits which of the given netblock. This
should be used in preference to simply referencing inside the
<a href="#CIDR-ADDR">CIDR</a> manually in external code, since
the structure might change on you.</p>
<p>See further notes about the desirability of using this
function above in the notes for <a href=
"#CIDR-GET-ADDR">cidr_get_addr()</a> .</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* addr:</span> An arbitrary netblock.</li>
</ul>
</li>
<li>Returns:
<p>uint8_t *</p>
<p>Returns a pointer to an 16-element array of uint8_t's
representing the netmask. This array must be <em class=
"funcname">free()</em> 'd when you're through with it. Returns
NULL on error.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>EFAULT</dt>
<dd>Passed NULL</dd>
</dl>
</li>
<li>
<dl>
<dt>ENOMEM</dt>
<dd><em class="funcname">malloc()</em> failed</dd>
</dl>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-GET-PFLEN">
<span class="funcdef">cidr_get_pflen(): Network bits in the
netmask</span>
<ul>
<li>Summary:
<p>Poke around the netmask of the passed-in <a href=
"#CIDR-ADDR">CIDR</a> structure and determine how many bits
there are in the netmask, as appropriate to the address
family.</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* block:</span> An arbitrary netblock.</li>
</ul>
</li>
<li>Returns:
<p>int</p>
<p>Returns the number of network bits in the netmask (0-32 for
IPv4, 0-128 for IPv6). Returns -1 on error.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>EFAULT</dt>
<dd>Passed NULL</dd>
</dl>
</li>
<li>
<dl>
<dt>EINVAL</dt>
<dd>Invalid (non-contiguous) netmask</dd>
</dl>
</li>
<li>
<dl>
<dt>ENOENT</dt>
<dd>Internal error (shouldn't happen)</dd>
</dl>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-GET-PROTO">
<span class="funcdef">cidr_get_proto(): Find a netblock's protocol
family</span>
<ul>
<li>Summary:
<p>Returns the protocol family of an address using one of the
defined constants. The current choices are CIDR_IPV4 and
CIDR_IPV6.</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* addr:</span> An arbitrary netblock.</li>
</ul>
</li>
<li>Returns:
<p>int</p>
<p>Returns the address family of the given netblock.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>EFAULT</dt>
<dd>Passed NULL</dd>
</dl>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-IS-V4MAPPED">
<span class="funcdef">cidr_is_v4mapped(): Is address IPv4-mapped
IPv6 address?</span>
<ul>
<li>Summary:
<p>An IPv6 address may be in the network range reserved for
IPv4-mapped addresses. This function will tell you whether it
is or not. Note that an IPv4 <a href="#CIDR-ADDR">CIDR</a> is
NOT considered an IPv4-mapped address, and so will return
failure.</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* addr:</span> An arbitrary netblock.</li>
</ul>
</li>
<li>Returns:
<p>int</p>
<p>Returns 0 if the address is an IPv4-mapped IPv6 address.
Returns -1 otherwise.</p>
</li>
</ul>
</li>
<li id="CIDR-NET-SUBNETS">
<span class="funcdef">cidr_net_subnets(): Divide a netblock</span>
<ul>
<li>Summary:
<p>Take in a netblock, and derive the two netblocks which it
divides up into. Return them in an array.</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* addr:</span> The netblock to subdivide.</li>
</ul>
</li>
<li>Returns:
<p><a href="#CIDR-ADDR">CIDR</a> **</p>
<p>Returns a 2-element array of <a href="#CIDR-ADDR">CIDR</a>
structs, containing the two subnets of addr. Each of the
elements should be cleaned up with <a href=
"#CIDR-FREE">cidr_free()</a> , and the array itself then
cleaned up with <em class="funcname">free()</em> . Returns
NULL on failure.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>0</dt>
<dd>No error (already a /32 or /128)</dd>
</dl>
</li>
<li>
<dl>
<dt>EFAULT</dt>
<dd>Passed NULL argument</dd>
</dl>
</li>
<li>
<dl>
<dt>ENOMEM</dt>
<dd><em class="funcname">malloc()</em> failed</dd>
</dl>
</li>
<li>
<div class="note">
<p>Note:</p>
<p><a href="#CIDR-NET-SUBNETS">cidr_net_subnets()</a>
can also fail and set errno for any of the reasons
listed for <a href=
"#CIDR-ADDR-NETWORK">cidr_addr_network()</a> or <a href=
"#CIDR-DUP">cidr_dup()</a> .</p>
</div>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-NET-SUPERNET">
<span class="funcdef">cidr_net_supernet(): Undivide a
netblock</span>
<ul>
<li>Summary:
<p>Take in a netblock, and derive the parent netblock in which
it fits.</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* addr:</span> The netblock to find the parent of.</li>
</ul>
</li>
<li>Returns:
<p><a href="#CIDR-ADDR">CIDR</a> *</p>
<p>Returns a <a href="#CIDR-ADDR">CIDR</a> struct defining the
parent network of addr. Clean this up with <a href=
"#CIDR-FREE">cidr_free()</a> when you're finished with it.
Returns NULL on failure.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>0</dt>
<dd>No error (already a /0)</dd>
</dl>
</li>
<li>
<dl>
<dt>EFAULT</dt>
<dd>Passed NULL argument</dd>
</dl>
</li>
<li>
<div class="note">
<p>Note:</p>
<p><a href="#CIDR-NET-SUPERNET">cidr_net_supernet()</a>
can also fail and set errno for any of the reasons
listed for <a href="#CIDR-DUP">cidr_dup()</a> .</p>
</div>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-NUMADDR">
<span class="funcdef">cidr_numaddr(): Addresses in a
netblock</span>
<ul>
<li>Summary:
<p>Determine the total number of addresses in a netblock
(including the network and broadcast addresses).</p>
<p>This function returns a pointer to a pre-formatted string
because we're potentially returning a value up to 2**128. I
don't feel like trying to portably do 128-bit arithmetic. Do
you?</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* addr:</span> An arbitrary netblock.</li>
</ul>
</li>
<li>Returns:
<p>const char *</p>
<p>Returns a pointer to a string containing the number of
addresses in the netblock. Note that this is a static string;
it should not be overwritten, and doesn't need to be
<em class="funcname">free()</em> 'd. Make a copy if you want
to manipulate it. Returns NULL on error.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>EFAULT</dt>
<dd>Passed NULL</dd>
</dl>
</li>
<li>
<div class="note">
<p>Note:</p>
<p><a href="#CIDR-NUMADDR">cidr_numaddr()</a> can also
also fail and set errno for any of the reasons listed
for <a href=
"#CIDR-NUMADDR-PFLEN">cidr_numaddr_pflen()</a> .</p>
</div>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-NUMADDR-PFLEN">
<span class="funcdef">cidr_numaddr_pflen(): Addresses in a prefix
length</span>
<ul>
<li>Summary:
<p>Determine the total number of addresses in a netblock with
the given prefix length (including the network and broadcast
addresses).</p>
<p>Note that this takes an IPv6 prefix length; that is, 0-128.
If you're interested in an IPv4 address with a given prefix
length, add 96 to it when you call this function.</p>
<p>See the note in <a href="#CIDR-NUMADDR">cidr_numaddr()</a>
for why we're returning a string and not a number.</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">int pflen:</span> A prefix length
(0-128).</li>
</ul>
</li>
<li>Returns:
<p>const char *</p>
<p>Returns a pointer to a string containing the number of
addresses in the netblock. Note that this is a static string;
it should not be overwritten, and doesn't need to be
<em class="funcname">free()</em> 'd. Make a copy if you want
to manipulate it. Returns NULL on error.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>EINVAL</dt>
<dd>Invalid prefix length</dd>
</dl>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-NUMHOST">
<span class="funcdef">cidr_numhost(): Host addresses in a
netblock</span>
<ul>
<li>Summary:
<p>Determine the total number of host addresses in a netblock
(excluding the network and broadcast addresses).</p>
<p>See the note in <a href="#CIDR-NUMADDR">cidr_numaddr()</a>
for why we're returning a string and not a number.</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* addr:</span> An arbitrary netblock.</li>
</ul>
</li>
<li>Returns:
<p>const char *</p>
<p>Returns a pointer to a string containing the number of host
addresses in the netblock. Note that this is a static string;
it should not be overwritten, and doesn't need to be
<em class="funcname">free()</em> 'd. Make a copy if you want
to manipulate it. Returns NULL on error.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>EFAULT</dt>
<dd>Passed NULL</dd>
</dl>
</li>
<li>
<div class="note">
<p>Note:</p>
<p><a href="#CIDR-NUMHOST">cidr_numhost()</a> can also
also fail and set errno for any of the reasons listed
for <a href=
"#CIDR-NUMHOST-PFLEN">cidr_numhost_pflen()</a> .</p>
</div>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-NUMHOST-PFLEN">
<span class="funcdef">cidr_numhost_pflen(): Host addresses in a
prefix length</span>
<ul>
<li>Summary:
<p>Determine the total number of host addresses in a netblock
with the given prefix length (excluding the network and
broadcast addresses).</p>
<p>Note that this takes an IPv6 prefix length; that is, 0-128.
If you're interested in an IPv4 address with a given prefix
length, add 96 to it when you call this function.</p>
<p>See the note in <a href="#CIDR-NUMADDR">cidr_numaddr()</a>
for why we're returning a string and not a number.</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">int pflen:</span> A prefix length
(0-128).</li>
</ul>
</li>
<li>Returns:
<p>const char *</p>
<p>Returns a pointer to a string containing the number of host
addresses in the netblock. Note that this is a static string;
it should not be overwritten, and doesn't need to be
<em class="funcname">free()</em> 'd. Make a copy if you want
to manipulate it. Returns NULL on error.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>EINVAL</dt>
<dd>Invalid prefix length</dd>
</dl>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-TO-INADDR">
<span class="funcdef">cidr_to_inaddr(): Create a struct
in_addr</span>
<ul>
<li>Summary:
<p>Takes in a <a href="#CIDR-ADDR">CIDR</a> and creates a
struct in_addr from it. This struct can then be used in
<em class="funcname">connect()</em> or similar network-related
functions. If the users passes in a struct in_addr, it will be
filled in. Otherwise, one will be allocated and returned.</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* addr:</span> A <a href="#CIDR-ADDR">CIDR</a> structure
describing the host to be translated into a struct in_addr.
Note that the netmask is irrelevant and will be ignored.
<a href="#CIDR-TO-INADDR">cidr_to_inaddr()</a> supports only
IPv4 addresses, as the underlying structure only does.</li>
<li><span class="argdef">struct in_addr * uptr:</span> A
pointer to a pre-allocated struct in_addr, or NULL. If
non-NULL, the pointed-at structure will be filled in. If
NULL, a new structure will be allocated, filled in, and
returned.</li>
</ul>
</li>
<li>Returns:
<p>struct in_addr *</p>
<p>Returns a pointer to the filled-in struct in_addr. If the
user passed one in, this will just point to the same place and
can profitably be ignored. If the user passed in NULL, this
will point to the struct in_addr we allocated, which should be
<em class="funcname">free()</em> 'd by the user when they're
finished with it. Returns NULL on error.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>EFAULT</dt>
<dd>Passed NULL</dd>
</dl>
</li>
<li>
<dl>
<dt>ENOMEM</dt>
<dd><em class="funcname">malloc()</em> failed</dd>
</dl>
</li>
<li>
<dl>
<dt>EPROTOTYPE</dt>
<dd>Bad protocol type (must be IPv4)</dd>
</dl>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-TO-IN6ADDR">
<span class="funcdef">cidr_to_in6addr(): Create a struct
in6_addr</span>
<ul>
<li>Summary:
<p>Takes in a <a href="#CIDR-ADDR">CIDR</a> and creates a
struct in6_addr from it. This struct can then be used in
<em class="funcname">connect()</em> or similar network-related
functions. If the users passes in a struct in6_addr, it will
be filled in. Otherwise, one will be allocated and
returned.</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* addr:</span> A <a href="#CIDR-ADDR">CIDR</a> structure
describing the host to be translated into a struct in6_addr.
Note that the netmask is irrelevant and will be ignored.
<a href="#CIDR-TO-IN6ADDR">cidr_to_in6addr()</a> supports
both IPv4 and IPv6 addresses, as the underlying structure
does as well. IPv4 addresses are treated as v4-mapped IPv6
addresses.</li>
<li><span class="argdef">struct in6_addr * uptr:</span> A
pointer to a pre-allocated struct in6_addr, or NULL. If
non-NULL, the pointed-at structure will be filled in. If
NULL, a new structure will be allocated, filled in, and
returned.</li>
</ul>
</li>
<li>Returns:
<p>struct in6_addr *</p>
<p>Returns a pointer to the filled-in struct in6_addr. If the
user passed one in, this will just point to the same place and
can profitably be ignored. If the user passed in NULL, this
will point to the struct in6_addr we allocated, which should
be <em class="funcname">free()</em> 'd by the user when
they're finished with it. Returns NULL on error.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>EFAULT</dt>
<dd>Passed NULL</dd>
</dl>
</li>
<li>
<dl>
<dt>ENOMEM</dt>
<dd><em class="funcname">malloc()</em> failed</dd>
</dl>
</li>
<li>
<dl>
<dt>EPROTOTYPE</dt>
<dd>Bad protocol type (must be IPv4 or IPv6)</dd>
</dl>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-TO-STR">
<span class="funcdef">cidr_to_str(): Create a human-readable
netblock description</span>
<ul>
<li>Summary:
<p>Takes in a <a href="#CIDR-ADDR">CIDR</a> structure, and
generates up a human-readable string describing the netblock.
This function has a lot of flexibility, depending on the flags
passed to it. The default output is "address/pflen" form, with
the address in a reasonably compact form, and the prefix
length given numerically. Flags alter the output in various
ways, and are set as bitmasks, so they can be combined however
you wish. They can be used in any combination that makes
sense, and a large number of combinations that don't.</p>
<p>The current flags are:<br>
CIDR_NOFLAGS: A stand-in for when you just want the default
output<br>
CIDR_NOCOMPACT: Don't do ::-style IPv6 compaction<br>
CIDR_VERBOSE: Show leading 0's in octets [v6 only]<br>
CIDR_USEV6: Use IPv4-mapped address form for IPv4 addresses
(::ffff:a.b.c.d)<br>
CIDR_USEV4COMPAT: Use IPv4-compat form (::a.b.c.d) instead of
IPv4-mapped form (only meaningful in combination with
CIDR_USEV6)<br>
CIDR_NETMASK: Return a netmask in standard form after the
slash, instead of the prefix length. Note that the form of the
netmask can thus be altered by the various flags that alter
how the address is displayed.<br>
CIDR_ONLYADDR: Show only the address, without the
prefix/netmask<br>
CIDR_ONLYPFLEN: Show only the prefix length (or netmask, when
combined with CIDR_NETMASK), without the address.<br>
CIDR_WILDCARD: Show a Cisco-style wildcard mask instead of the
netmask (only meaningful in combination with CIDR_NETMASK)<br>
CIDR_FORCEV6: Forces treating the <a href=
"#CIDR-ADDR">CIDR</a> as an IPv6 address, no matter what it
really is. This doesn't do any conversion or translation; just
treats the raw data as if it were IPv6.<br>
CIDR_FORCEV4: Forces treating the <a href=
"#CIDR-ADDR">CIDR</a> as an IPv4 address, no matter what it
really is. This doesn't do any conversion or translation; just
treats the raw data as if it were IPv4.<br>
CIDR_REVERSE: Generates a .in-addr.arpa or .ip6.arpa-style PTR
record name for the given block. Note that this always treats
it solely as an address; the netmask is ignored. See some
notes in <a href="#CIDR-FROM-STR">cidr_from_str()</a> for
details of the asymmetric treatment of this form of address
representation relating to the netmask.</p>
<p>Many combinations can give somewhat surprising results, but
they should allow any of a host of manipulations to output
just the data you might be interested in. The "mkstr" test
program in the source tree is extremely useful for manual
testing of the various flags to see visually what they do, and
is a lot quicker than trying to code them all to test it out.
Use it to your advantage.</p>
</li>
<li>Arguments:
<ul>
<li><span class="argdef">const <a href="#CIDR-ADDR">CIDR</a>
* block:</span> The <a href="#CIDR-ADDR">CIDR</a> structure
to generate a string form of. The address family will be
autodetected.</li>
<li><span class="argdef">int flags:</span> A bitmask of the
various possible flags the function accepts.</li>
</ul>
</li>
<li>Returns:
<p>char *</p>
<p>Returns a pointer to a string containing the representation
of the network. Be sure to <em class="funcname">free()</em> it
when you're finished.</p>
</li>
<li>Error codes:
<ul>
<li>
<dl>
<dt>EINVAL</dt>
<dd>Invalid argument (bad block or flags)</dd>
</dl>
</li>
<li>
<dl>
<dt>ENOENT</dt>
<dd>Internal error (shouldn't happen)</dd>
</dl>
</li>
<li>
<dl>
<dt>ENOMEM</dt>
<dd><em class="funcname">malloc()</em> failed</dd>
</dl>
</li>
<li>
<div class="note">
<p>Note:</p>
<p><a href="#CIDR-TO-STR">cidr_to_str()</a> can also
fail and set errno for any of the reasons listed for
<a href="#CIDR-ALLOC">cidr_alloc()</a> or <a href=
"#CIDR-GET-PFLEN">cidr_get_pflen()</a> .</p>
</div>
</li>
</ul>
</li>
</ul>
</li>
<li id="CIDR-VERSION">
<span class="funcdef">cidr_version(): Library version</span>
<ul>
<li>Summary:
<p>Returns a static string describing the library release
version.</p>
</li>
<li>Arguments:
<ul>
<li>None</li>
</ul>
</li>
<li>Returns:
<p>const char *</p>
<p>Returns a pointer to a static string describing the library
version number. It shouldn't be overwritten or <em class=
"funcname">free()</em> 'd.</p>
</li>
</ul>
</li>
</ul>
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