IPV4 to IPV6: Socket

<pre>C++ Internet Protocol and Socket Address Classes

Document Number: TBD
Date:   TBD
Author:   Aleksandar Fabijanic <alex AT pocoproject.org>
   Günter Obiltschnig <guenter.obiltschnig AT appinf.com>

Content

1. Revision History

2. Motivation and Scope

3. IP Address
 3.1. Usage Examples
  3.1.1. IPv4
  3.1.2. IPv6
 3.2. Header <ip_address> synopsis

5. Socket Address
 5.1. Usage Examples
 5.2. Header <socket_address> synopsis

6. Conclusion

7. Acknowledgments

1. Revision History

- Oct 10 2012: created

2. Motivation and Scope

Given the pervasiveness of networking and Internet, there is a
pressing need for standard networking support in C++ language.
This proposal addresses the concerns of IP and socket addresses;
it is aimed to be one of the fundamental building blocks and
steps toward the Standard C++ Network Library goal.

This proposal is based on IP and socket address implementations
in the Net library in C++ Portable Components (POCO) [6] framework.
POCO framework has been open sourced in 2005 by its principal
sponsor (Applied Informatics Software Engineering GmbH) and is
currently licensed under Boost Software License and used in
production by numerous commercial entities as well as other
open source projects [7].

The scope of the proposal is description of functionality,
interfaces and usage examples for a set of classes providing
functionality to store and manipulate Internet Protocol
(IPv4 and v6) as well as socket (IP address + port) addresses.

3. IP Address

The ip_address class represents an Internet Protocol host
address. The address can belong to either IPv4 or IPv6 
(if the target platform supports it) address family.

Relational operators (==, !=, <, <=, >, >=) are supported. 
Notably, an IPv4 address is never equal to an IPv6 
address, even if the IPv6 address is IPv4 compatible and 
the addresses are logically the same.

For underlying IP address bit manipulation, bitwise operators
(&, |, ^, ~) are supported.

3.1 Usage Examples

3.1.1. IPv4:

ip_address ia("127.0.0.1");
assert (ia.family() == ip_address::ipv4);
assert (ia.to_string() == "127.0.0.1");
assert (ip.is_loopback());

ip_address addr("10.0.0.51");
ip_address mask(24, ip_address::ipv4);
assert(mask.prefix_len() == 24);

ip_address net = addr & mask;
assert(net.to_string() == "10.0.0.0");

ip_address host("0.0.0.51");
assert((net | host) == addr);
assert((~mask).to_string() == "0.0.0.255");

3.1.2. IPv6

ip_address ia("1080:0:0:0:8:600:200a:425c");
assert (ia.family() == ip_address::ipv6);
assert (ia.to_string() == "1080::8:600:200a:425c");

ip_address ia(62, ip_address::ipv6);
assert(ia.to_string() == "ffff:ffff:ffff:fffc::");

3.2. Header <ip_address> synopsis

namespace std {
namespace net {

typedef int socklen_t;

class ip_address {
public:
typedef std::vector<IPAddress> list;

enum family
/// Possible address families for IP addresses.
{
 ipv4
#ifdef _STD_HAVE_IPv6
 ,ipv6
#endif
};
 
ip_address();
 /// Creates a wildcard (zero) IPv4 ip_address.

ip_address(const ip_address& addr);
 /// Creates an ip_address by copying another one.

explicit IPAddress(family family);
 /// Creates a wildcard (zero) ip_address for the given address family.

explicit ip_address(const std::string& addr);
 /// Creates an IPAddress from the string containing
 /// an IP address in presentation format (dotted decimal
 /// for IPv4, hex string for IPv6).
 /// Depending on the format of addr, IPv4 or an IPv6 address is 
 /// created. See to_string() for details on the supported formats.
 /// Throws std::runtime_exception if the address cannot be parsed.

ip_address(const std::string& addr, Family family);
 /// Creates an ip_address from the string containing
 /// an IP address in presentation format (dotted decimal
 /// for IPv4, hex string for IPv6).

ip_address(const void* addr, socklen_t length);
 /// Creates an IPAddress from a native internet address.
 /// A pointer to an in_addr or an in6_addr structure may be passed.

ip_address(const void* addr, socklen_t length, uint32_t scope);
 /// Creates an IPAddress from a native internet address.
 /// A pointer to a in_addr or a in6_addr structure may be 
 /// passed. Additionally, for an IPv6 address, a scope ID
 /// may be specified. The scope ID will be ignored if an IPv4
 /// address is specified.

ip_address(uint32_t prefix, family family);
 /// Creates an ip_address mask with the given length of prefix.

ip_address(const struct sockaddr& sockaddr);
 /// Creates an ip_address from sockaddr structure.

~ip_address();
 /// Destroys the IPAddress.

ip_address& operator = (const ip_address& addr);
 /// Assigns an IPAddress.
  
void swap(ip_address& address);
 /// Swaps the IPAddress with another one.
  
family family() const;
 /// Returns the address family (ipv4 or ipv6) of the address.

uint32_t scope() const;
 /// Returns the IPv6 scope identifier of the address. Returns 0 if
 /// the address is an IPv4 address, or the address is an
 /// IPv6 address but does not have a scope identifier.

std::string to_string() const;
 /// Returns a string containing a representation of the address
 /// in presentation format.
 /// For IPv4 addresses the result will be in dotted-decimal (d.d.d.d) notation.
 /// The preferred form is x:x:x:x:x:x:x:x, where the 'x's are the hexadecimal 
 /// values of the eight 16-bit pieces of the address. This is the full form.
 /// Example: 1080:0:0:0:8:600:200a:425c
 /// It is not necessary to write the leading zeros in an individual field. 
 /// However, there must be at least one numeral in every field, except as 
 /// described below.
 /// It is common for IPv6 addresses to contain long strings of zero bits. 
 /// In order to make writing addresses containing zero bits easier, a special
  /// syntax is  available to compress the zeros. The use of "::" indicates multiple
 /// groups of 16-bits of zeros. 
 /// The "::" can only appear once in an address. The "::" can also be used to 
 /// compress the leading and/or trailing zeros in an address. 
 /// Example: 1080::8:600:200a:425c
 /// For dealing with IPv4 compatible addresses in a mixed environment,
 /// a special syntax is available: x:x:x:x:x:x:d.d.d.d, where the 'x's are the 
 /// hexadecimal values of the six high-order 16-bit pieces of the address, 
 /// and the 'd's are the decimal values of the four low-order 8-bit pieces of the 
 /// standard IPv4 representation address. Example: ::ffff:192.168.1.120
 /// If an IPv6 address contains a non-zero scope identifier, it is added
 /// to the string, delimited by a percent character. On Windows platforms,
 /// the numeric value (which specifies an interface index) is directly
 /// appended. On Unix platforms, the name of the interface corresponding
 /// to the index (interpretation of the scope identifier) is added.

bool is_wildcard() const;
 /// Returns true iff the address is a wildcard (all zero) address.
  
bool is_broadcast() const;
 /// Returns true iff the address is a broadcast address.
 /// Only IPv4 addresses can be broadcast addresses. In a broadcast
 /// address, all bits are one. For an IPv6 address, returns always false.
 
bool is_loopback() const;
 /// Returns true iff the address is a loopback address.
 /// For IPv4, the loopback address is 127.0.0.1.
 /// For IPv6, the loopback address is ::1.
 
bool is_multicast() const;
 /// Returns true iff the address is a multicast address.
 /// IPv4 multicast addresses are in the
 /// 224.0.0.0 to 239.255.255.255 range
 /// (the first four bits have the value 1110).
 /// IPv6 multicast addresses are in the
 /// FFxx:x:x:x:x:x:x:x range.
  
bool is_unicast() const;
 /// Returns true iff the address is a unicast address.
 /// An address is unicast if it is neither a wildcard,
 /// broadcast or multicast address.
  
bool is_link_local() const;
 /// Returns true iff the address is a link local unicast address.
 /// IPv4 link local addresses are in the 169.254.0.0/16 range,
 /// according to RFC 3927.
 /// IPv6 link local addresses have 1111 1110 10 as the first
 /// 10 bits, followed by 54 zeros.
  
bool is_site_local() const;
 /// Returns true iff the address is a site local unicast address.
 /// IPv4 site local addresses are in on of the 10.0.0.0/24,
 /// 192.168.0.0/16 or 172.16.0.0 to 172.31.255.255 ranges.
 /// Originally, IPv6 site-local addresses had FEC0/10 (1111 1110 11) 
 /// prefix (RFC 4291), followed by 38 zeros. Interfaces using  
 /// this mask are supported, but obsolete; RFC 4193 [3] prescribes
 /// fc00::/7 (1111 110) as local unicast prefix.
  
bool is_ipv4_compatible() const;
 /// Returns true iff the address is IPv4 compatible.
 /// For IPv4 addresses, this is always true.
 /// For IPv6, the address must be in the ::x:x range (the
 /// first 96 bits are zero).

bool is_ipv4_mapped() const;
 /// Returns true iff the address is an IPv4 mapped IPv6 address.
 /// For IPv4 addresses, this is always true.
 /// For IPv6, the address must be in the ::FFFF:x:x range.
 
bool is_well_known_mcast() const;
 /// Returns true iff the address is a well-known multicast address.
 /// For IPv4, well-known multicast addresses are in the 224.0.0.0/8 range.
 /// For IPv6, well-known multicast addresses are in the 
 /// FF0x:x:x:x:x:x:x:x range.
 
bool is_node_local_mcast() const;
 /// Returns true iff the address is a node-local multicast address.
 /// IPv4 does not support node-local addresses, thus the result is
 /// always false for an IPv4 address.
 /// For IPv6, node-local multicast addresses are in the
 /// FFx1:x:x:x:x:x:x:x range.
 
bool is_link_local_mcast() const;
 /// Returns true iff the address is a link-local multicast address.
 /// For IPv4, link-local multicast addresses are in the
 /// 224.0.0.0/24 range. Note that this overlaps with the range for well-known
 /// multicast addresses.
 /// For IPv6, link-local multicast addresses are in the
 /// FFx2:x:x:x:x:x:x:x range.

bool is_site_local_mcast() const;
 /// Returns true iff the address is a site-local multicast address.
 /// For IPv4, site local multicast addresses are in the 239.255.0.0/16 range.
 /// For IPv6, site-local multicast addresses are in the
 /// FFx5:x:x:x:x:x:x:x range.

bool is_org_local_mcast() const;
 /// Returns true iff the address is a organization-local multicast address.
 /// For IPv4, organization-local multicast addresses are in the
 /// 239.192.0.0/16 range.
 /// For IPv6, organization-local multicast addresses are in the
 /// FFx8:x:x:x:x:x:x:x range.

bool is_global_mcast() const;
 /// Returns true iff the address is a global multicast address.
 /// For IPv4, global multicast addresses are in the 
 /// 224.0.1.0 to 238.255.255.255 range.
 /// For IPv6, global multicast addresses are in the
 /// FFxF:x:x:x:x:x:x:x range.
 
bool operator == (const ip_address& addr) const;
 /// Returns true if IP addresses are equal.

bool operator != (const ip_address& addr) const;
 /// Returns true if IP addresses are not equal.

bool operator <  (const ip_address& addr) const;
 /// Returns true if this IP address is lesser than addr.

bool operator <= (const ip_address& addr) const;
 /// Returns true if this IP address is lesser than or equal to addr.

bool operator >  (const ip_address& addr) const
 /// Returns true if this IP address is greater than addr.

bool operator >= (const ip_address& addr) const;
 /// Returns true if this IP address is greater than or equal to addr.

ip_address operator & (const ip_address& addr) const;
 /// Performs a bitwise ANd operation and returns result.

ip_address operator | (const ip_address& addr) const;
 /// Performs a bitwise OR operation and returns result.

ip_address operator ^ (const ip_address& addr) const;
 /// Performs a bitwise XOR operation and returns result.

ip_address operator ~ () const;
 /// Performs a bitwise NOT operation on this IP address and returns result.
  
socklen_t length() const;
 /// Returns the length in bytes of the internal socket address structure. 
  
const void* addr() const;
 /// Returns the internal address structure.
  
uint32_t af() const;
 /// Returns the address family (AF_INET or AF_INET6) of the address.

unit32_t prefix_len() const;
 /// Returns the prefix length.
  
void mask(const ip_address& mask);
 /// Masks the IP address using the given netmask, which is usually
 /// a IPv4 subnet mask. Only supported for IPv4 addresses.
 /// The new address is (address & mask).
  
void mask(const ip_address& mask, const ip_address& set);
 /// Masks the IP address using the given netmask, which is usually
 /// a IPv4 subnet mask. Only supported for IPv4 addresses.
 /// The new address is (address & mask) | (set & ~mask).
  
static ip_address assign(const std::string& addr);
 /// Creates an IPAddress from the string containing
 /// an IP address in presentation format (dotted decimal
 /// for IPv4, hex string for IPv6).
 /// Depending on the format of addr, either an IPv4 or
 /// an IPv6 address is created.
 /// See to_string() for details on the supported formats.
 /// Throws std::runtime_exception if the address cannot be parsed.

static bool try_assign(const std::string& addr, IPAddress& result);
 /// Tries to interpret the given address string as an
 /// IP address in presentation format (dotted decimal
 /// for IPv4, hex string for IPv6).
 /// Returns true and stores the IPAddress in result if the
 /// string contains a valid address.
 /// Returns false and leaves result unchanged otherwise.

static IPAddress wildcard(Family family = ipv4);
 /// Returns a wildcard IPv4 or IPv6 address.
  
static IPAddress broadcast();
 /// Returns a broadcast IPv4 address (255.255.255.255).
};
}} // namespace std::net

4. Socket Address

This class represents an internet (IP) endpoint/socket address. The address
can belong either to the IPv4 or the IPv6 address family and consists of a
host IP  address and a port number.

4.1 Usage Examples

socket_address wild;
assert (wild.host().is_wildcard());
assert (wild.port() == 0);

socket_address sa1("192.168.1.100", 100);
assert (sa1.host().to_string() == "192.168.1.100");
assert (sa1.port() == 100);

socket_address sa2("192.168.1.100", "100");
assert (sa2.host().to_string() == "192.168.1.100");
assert (sa2.port() == 100);

socket_address sa3("192.168.1.100", "ftp");
assert (sa3.host().to_string() == "192.168.1.100");
assert (sa3.port() == 21);

socket_address sa4("www.appinf.com", 80);
assert (sa4.host().toString() == "50.57.108.29");
assert (sa4.port() == 80);

4.2 Header <socket_address> synopsis

namespace std {
namespace net {
class socket_address
 /// This class represents an (IP) socket address.
 /// The address can belong either to the IPv4 or the IPv6 address
 /// family and consists of a host address and a port number.
{
public:
socket_address();
 /// Creates a wildcard (all zero) IPv4 socket_address.

socket_address(const ip_address& host, uint_16t port);
 /// Creates a socket_address from an IP address and a port number.

socket_address(const std::string& host, uint_16t port);
 /// Creates a socket_address from an IP address and a port number.
 /// The IP address must either be a domain name, or it must
 /// be in dotted decimal (IPv4) or hex string (IPv6) format.

socket_address(const std::string& host, const std::string& port);
 /// Creates a socket_address from an IP address and a
 /// service name or port number.
 /// The IP address must either be a domain name, or it must
 /// be in dotted decimal (IPv4) or hex string (IPv6) format.
 /// The given port must either be a decimal port number, or
 /// a service name (as typically returned in struct servent
 /// by the getservbyname() call.

explicit socket_address(const std::string& host_and_port);
 /// Creates a socket_address from an IP address or host name and a
 /// port number/service name. Host name/address and port number
 /// must be separated by a colon. In case of an IPv6 address, the
 /// address part must be enclosed in brackets.
 /// 
 /// Examples:
 ///     192.168.1.10:80
 ///     [::ffff:192.168.1.120]:2040
 ///     www.appinf.com:8080

socket_address(const socket_address& addr);
 /// Creates a socket_address by copying another one.

socket_address(const struct sockaddr* addr, socklen_t length);
 /// Creates a socket_address from a native socket address.

~socket_address();
 /// Destroys the socket_address.

socket_address& operator = (const socket_address& addr);
 /// Assigns another socket_address.

void swap(socket_address& addr);
 /// Swaps the socket_address with another one.

ip_address host() const;
 /// Returns the host IP address.

uint_16t port() const;
 /// Returns the port number.

socklen_t length() const;
 /// Returns the length of the internal native socket address.

const struct sockaddr* addr() const;
 /// Returns a pointer to the internal native socket address.

uint32_t af() const;
 /// Returns the address family (AF_INET or AF_INET6) of the address.

std::string to_string() const;
 /// Returns a string representation of the address.

ip_address::family family() const;
 /// Returns the address family of the host's address.

bool operator < (const socket_address& addr) const;
 /// Less than operator.

bool operator == (const socket_address& addr) const;
 /// Equal operator.

bool operator != (const socket_address& addr) const;
 /// Not equal operator.

};
}} // namespace std::net

6. Conclusion

Class interfaces for IP and socket address as well as rationale for their 
introduction in C++ Standard and usage examples were described in this 
proposal. This proposal is one of the starting points and building blocks 
for C++ Standard Networking Library. Implementation of the described 
functionality is currently available in POCO framework [6]; the 
implementation differs in naming scheme from this proposal. Given a 
positive feedback on the proposal, implementation  will be available 
in the near future as a standalone implementation in standard-compliant 
naming convention, with accompanying tests and code examples.

7. Acknowledgements

POCO original author (Günter Obiltschnig)
POCO project contributors and users

References

[1] RFC 791
[2] RFC 2460
[3] RFC 4193
[4] RFC 3513
[5] RFC 3879
[6] C++ Portable Components: http://pocoproject.org
[7] List of known POCO users: http://pocoproject.org/forum/viewtopic.php?f=11&t=3826

C++ Internet Protocol and Socket Address Classes

C++ Internet Protocol and Socket Address Classes Document Number: TBD Date: TBD Author: Aleksandar Fabijanic <alex AT pocoproject.or...

C++ Internet Protocol and Socket Address Classes

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