CONTENTS

SYNOPSIS

DESCRIPTION

Sockets bound to the inet6 family utilize the following addressing structure:
struct sockaddr_in6 {
uint8_t sin6_len;
sa_family_tsin6_family;
in_port_t sin6_port;
uint32_t sin6_flowinfo;
struct in6_addr sin6_addr;
uint32_t sin6_scope_id;
};

Sockets may be created with the local address "::" (which is equal to IPv6 address 0:0:0:0:0:0:0:0) to affect "wildcard" matching on incoming messages.

The IPv6 specification defines scoped addresses, like link-local or site-local addresses. A scoped address is ambiguous to the kernel, if it is specified without a scope identifier. To manipulate scoped addresses properly from the userland, programs must use the advanced API defined in RFC2292. A compact description of the advanced API is available in ip6(4). If a scoped address is specified without an explicit scope, the kernel may raise an error. Note that scoped addresses are not for daily use at this moment, both from a specification and an implementation point of view.

The KAME implementation supports an extended numeric IPv6 address notation for link-local addresses, like "fe80::1%de0" to specify " fe80::1 on de0 interface ". This notation is supported by getaddrinfo(3) and getnameinfo(3). Some of normal userland programs, such as telnet(1) or ftp(1), are able to use this notation. With special programs like ping6(8), you can specify the outgoing interface by an extra command line option to disambiguate scoped addresses.

MIB Variables

Interaction between IPv4/v6 sockets

The behavior of AF_INET6 TCP/UDP socket is documented in RFC2553. Basically, it says this:

• A specific bind on an AF_INET6 socket ( bind 2 with an address specified) should accept IPv6 traffic to that address only.
• If you perform a wildcard bind on an AF_INET6 socket ( bind 2 to IPv6 address ::), and there is no wildcard bind AF_INET socket on that TCP/UDP port, IPv6 traffic as well as IPv4 traffic should be routed to that AF_INET6 socket. IPv4 traffic should be seen as if it came from an IPv6 address like ::ffff:10.1.1.1. This is called an IPv4 mapped address.
• If there are both a wildcard bind AF_INET socket and a wildcard bind AF_INET6 socket on one TCP/UDP port, they should behave separately. IPv4 traffic should be routed to the AF_INET socket and IPv6 should be routed to the AF_INET6 socket.

However, RFC2553 does not define the ordering constraint between calls to bind(2), nor how IPv4 TCP/UDP port numbers and IPv6 TCP/UDP port numbers relate to each other (should they be integrated or separated). Implemented behavior is very different from kernel to kernel. Therefore, it is unwise to rely too much upon the behavior of AF_INET6 wildcard bind sockets. It is recommended to listen to two sockets, one for AF_INET and another for AF_INET6, when you would like to accept both IPv4 and IPv6 traffic.

STANDARDS

HISTORY

BUGS