mirror of
https://github.com/soypat/lneto.git
synced 2026-08-14 11:53:43 +00:00
Pat Whittingslow
7d5830d7ab
* begin adding udp.MuxHandler * add udp MuxHandlerSIMO/MIMO * add tcp rx shutdown * icmpv6 client * icmpv6 Client shared NDP/Echo preparation * icmpv6 client ndp/echo split * icmpv6 client ndp/echo split done * icmpv6 adjustments * add dhcpv6 stubs * dhcpv4 preliminary revision * add dns.NextLabel * dns label name tweaks * dns begin work on TCP client * add dnstcp package * apply gofmt changes * add udp mux tests * clean up, remove StackBig for now * remove dnstcp so as to merged confident parts and we continue dnstcp work elsewhere
85 lines
2.5 KiB
Go
85 lines
2.5 KiB
Go
package dhcpv6
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import (
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"encoding/binary"
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"io"
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"github.com/soypat/lneto"
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)
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// NewFrame returns a Frame backed by buf.
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// Returns an error if buf is shorter than [OptionsOffset] bytes.
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func NewFrame(buf []byte) (Frame, error) {
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if len(buf) < OptionsOffset {
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return Frame{}, lneto.ErrTruncatedFrame
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}
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return Frame{buf: buf}, nil
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}
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// Frame encapsulates the raw bytes of a DHCPv6 client-server message (RFC 8415 §8)
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// and provides methods for accessing and modifying its fields.
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//
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// Layout:
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//
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// Byte 0: msg-type
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// Bytes 1-3: transaction-id (24-bit big-endian)
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// Bytes 4+: options (code(2) + length(2) + data)
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type Frame struct {
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buf []byte
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}
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// MsgType returns the message type field.
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func (frm Frame) MsgType() MsgType { return MsgType(frm.buf[0]) }
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// SetMsgType sets the message type field.
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func (frm Frame) SetMsgType(t MsgType) { frm.buf[0] = byte(t) }
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// TransactionID returns the 24-bit transaction ID as a uint32 (upper byte is always zero).
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func (frm Frame) TransactionID() uint32 {
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return uint32(frm.buf[1])<<16 | uint32(frm.buf[2])<<8 | uint32(frm.buf[3])
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}
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// SetTransactionID writes the lower 24 bits of id into bytes 1–3.
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func (frm Frame) SetTransactionID(id uint32) {
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frm.buf[1] = byte(id >> 16)
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frm.buf[2] = byte(id >> 8)
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frm.buf[3] = byte(id)
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}
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// Options returns the options section of the frame (bytes from [OptionsOffset] onward).
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func (frm Frame) Options() []byte { return frm.buf[OptionsOffset:] }
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// ForEachOption iterates over all DHCPv6 options in the frame's options section.
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// Each option is passed to fn as (byteOffset, optionCode, optionData).
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// Iteration stops early if fn returns [io.EOF]; any other non-nil error is returned directly.
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// If fn is nil, the function only validates the structure.
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func (frm Frame) ForEachOption(fn func(off int, code OptCode, data []byte) error) error {
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buf := frm.buf
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ptr := OptionsOffset
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for ptr+4 <= len(buf) {
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code := OptCode(binary.BigEndian.Uint16(buf[ptr:]))
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optlen := int(binary.BigEndian.Uint16(buf[ptr+2:]))
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if ptr+4+optlen > len(buf) {
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return lneto.ErrInvalidLengthField
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}
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if fn != nil {
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err := fn(ptr, code, buf[ptr+4:ptr+4+optlen])
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if err == io.EOF {
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return nil
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}
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if err != nil {
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return err
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}
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}
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ptr += 4 + optlen
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}
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if ptr != len(buf) {
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// 1–3 trailing bytes that cannot form a valid option header.
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return lneto.ErrTruncatedFrame
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}
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return nil
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}
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// ValidateSize validates the structure of the options section without invoking a callback.
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func (frm Frame) ValidateSize() error { return frm.ForEachOption(nil) }
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