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package dhcp6opts
import (
"io"
"net"
"time"
"github.com/mdlayher/dhcp6"
"github.com/mdlayher/dhcp6/internal/buffer"
)
// IAPrefix represents an Identity Association Prefix, as defined in RFC 3633,
// Section 10.
//
// Routers may use identity association prefixes (IAPrefixes) to request IPv6
// prefixes to assign individual address to IPv6 clients, using the lifetimes
// specified in the preferred lifetime and valid lifetime fields. Multiple
// IAPrefixes may be present in a single DHCP request, but only enscapsulated
// within an IAPD's options.
type IAPrefix struct {
// PreferredLifetime specifies the preferred lifetime of an IPv6 prefix.
// When the preferred lifetime of a prefix expires, the prefix becomes
// deprecated, and addresses from the prefix should not be used in new
// communications.
//
// The preferred lifetime of a prefix must not be greater than its valid
// lifetime.
PreferredLifetime time.Duration
// ValidLifetime specifies the valid lifetime of an IPv6 prefix. When the
// valid lifetime of a prefix expires, addresses from the prefix the address
// should not be used for any further communication.
//
// The valid lifetime of a prefix must be greater than its preferred
// lifetime.
ValidLifetime time.Duration
// PrefixLength specifies the length in bits of an IPv6 address prefix, such
// as 32, 64, etc.
PrefixLength uint8
// Prefix specifies the IPv6 address prefix from which IPv6 addresses can
// be allocated.
Prefix net.IP
// Options specifies a map of DHCP options specific to this IAPrefix.
// Its methods can be used to retrieve data from an incoming IAPrefix, or
// send data with an outgoing IAPrefix.
Options dhcp6.Options
}
// NewIAPrefix creates a new IAPrefix from preferred and valid lifetime
// durations, an IPv6 prefix length, an IPv6 prefix, and an optional Options
// map.
//
// The preferred lifetime duration must be less than the valid lifetime
// duration. The IPv6 prefix must be exactly 16 bytes, the correct length
// for an IPv6 address. Failure to meet either of these conditions will result
// in an error. If an Options map is not specified, a new one will be
// allocated.
func NewIAPrefix(preferred time.Duration, valid time.Duration, prefixLength uint8, prefix net.IP, options dhcp6.Options) (*IAPrefix, error) {
// Preferred lifetime must always be less than valid lifetime.
if preferred > valid {
return nil, ErrInvalidLifetimes
}
// From documentation: If ip is not an IPv4 address, To4 returns nil.
if prefix.To4() != nil {
return nil, ErrInvalidIP
}
// If no options set, make empty map
if options == nil {
options = make(dhcp6.Options)
}
return &IAPrefix{
PreferredLifetime: preferred,
ValidLifetime: valid,
PrefixLength: prefixLength,
Prefix: prefix,
Options: options,
}, nil
}
// MarshalBinary allocates a byte slice containing the data from a IAPrefix.
func (i *IAPrefix) MarshalBinary() ([]byte, error) {
// 4 bytes: preferred lifetime
// 4 bytes: valid lifetime
// 1 byte : prefix length
// 16 bytes: IPv6 prefix
// N bytes: options
b := buffer.New(nil)
b.Write32(uint32(i.PreferredLifetime / time.Second))
b.Write32(uint32(i.ValidLifetime / time.Second))
b.Write8(i.PrefixLength)
copy(b.WriteN(net.IPv6len), i.Prefix)
opts, err := i.Options.MarshalBinary()
if err != nil {
return nil, err
}
b.WriteBytes(opts)
return b.Data(), nil
}
// UnmarshalBinary unmarshals a raw byte slice into a IAPrefix.
//
// If the byte slice does not contain enough data to form a valid IAPrefix,
// io.ErrUnexpectedEOF is returned. If the preferred lifetime value in the
// byte slice is less than the valid lifetime, ErrInvalidLifetimes is
// returned.
func (i *IAPrefix) UnmarshalBinary(p []byte) error {
b := buffer.New(p)
// IAPrefix must at least contain lifetimes, prefix length, and prefix
if b.Len() < 25 {
return io.ErrUnexpectedEOF
}
i.PreferredLifetime = time.Duration(b.Read32()) * time.Second
i.ValidLifetime = time.Duration(b.Read32()) * time.Second
// Preferred lifetime must always be less than valid lifetime.
if i.PreferredLifetime > i.ValidLifetime {
return ErrInvalidLifetimes
}
i.PrefixLength = b.Read8()
i.Prefix = make(net.IP, net.IPv6len)
copy(i.Prefix, b.Consume(net.IPv6len))
return (&i.Options).UnmarshalBinary(b.Remaining())
}
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