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net/packet: documentation pass.

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Signed-off-by: David Anderson <danderson@tailscale.com>
This commit is contained in:
David Anderson
2020-11-10 22:26:00 -08:00
parent c2cc3acbaf
commit a38e28da07
6 changed files with 116 additions and 83 deletions
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23
net/packet/udp4.go
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@@ -6,23 +6,23 @@ package packet
import "encoding/binary"
// UDPHeader represents an UDP packet header.
// udpHeaderLength is the size of the UDP packet header, not including
// the outer IP header.
const udpHeaderLength = 8
// UDP4Header is an IPv4+UDP header.
type UDP4Header struct {
IP4Header
SrcPort uint16
DstPort uint16
}
const (
// udpHeaderLength is the size of the UDP packet header, not
// including the outer IP header.
udpHeaderLength = 8
)
func (UDP4Header) Len() int {
return ip4HeaderLength + udpHeaderLength
// Len implements Header.
func (h UDP4Header) Len() int {
return h.IP4Header.Len() + udpHeaderLength
}
// Marshal implements Header.
func (h UDP4Header) Marshal(buf []byte) error {
if len(buf) < h.Len() {
return errSmallBuffer
@@ -40,14 +40,15 @@ func (h UDP4Header) Marshal(buf []byte) error {
binary.BigEndian.PutUint16(buf[26:28], 0) // blank checksum
// UDP checksum with IP pseudo header.
h.IP4Header.MarshalPseudo(buf)
binary.BigEndian.PutUint16(buf[26:28], ipChecksum(buf[8:]))
h.IP4Header.marshalPseudo(buf)
binary.BigEndian.PutUint16(buf[26:28], ip4Checksum(buf[ip4PseudoHeaderOffset:]))
h.IP4Header.Marshal(buf)
return nil
}
// ToResponse implements Header.
func (h *UDP4Header) ToResponse() {
h.SrcPort, h.DstPort = h.DstPort, h.SrcPort
h.IP4Header.ToResponse()