mirror of
https://github.com/soypat/lneto.git
synced 2026-08-06 07:53:41 +00:00
Pat Whittingslow
bd645b5e1e
* add mdns * define mdns.Client * fix some mdns stuff * refine dns package for use with mdns * remove Querier and Responder and replace with Client * add record setting methods on dns.record to reuse record buffer * protect against unbounded client answer growth * round off sharp mdns edges; reduce allocs * add mutlicast to stacks; add xnet tests for mdns * fix documentation on acceptmulticast field * mdns working
93 lines
2.1 KiB
Go
93 lines
2.1 KiB
Go
package internal
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import (
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"encoding/binary"
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"github.com/soypat/lneto"
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)
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func GetIPAddr(buf []byte) (src, dst []byte, id, ipEndOff uint16, err error) {
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b0 := buf[0]
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version := b0 >> 4
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switch version {
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case 4:
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ihl := b0 & 0xf
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ipEndOff = 4 * uint16(ihl)
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id = binary.BigEndian.Uint16(buf[4:6])
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src = buf[12:16]
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dst = buf[16:20]
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case 6:
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src = buf[8:24]
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dst = buf[24:40]
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ipEndOff = 40
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default:
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err = lneto.ErrUnsupported
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}
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return src, dst, id, ipEndOff, err
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}
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func SetIPAddrs(buf []byte, id uint16, src, dst []byte) (err error) {
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var dstaddr, srcaddr []byte
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version := buf[0] >> 4
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switch version {
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case 4:
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srcaddr = buf[12:16]
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dstaddr = buf[16:20]
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if id > 0 {
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binary.BigEndian.PutUint16(buf[4:6], id)
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}
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case 6:
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srcaddr = buf[8:24]
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dstaddr = buf[24:40]
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default:
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return lneto.ErrUnsupported
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}
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if src != nil && len(srcaddr) != len(src) {
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return lneto.ErrMismatchLen
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}
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if dst != nil && len(dstaddr) != len(dst) {
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return lneto.ErrMismatchLen
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}
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copy(srcaddr, src)
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copy(dstaddr, dst)
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return nil
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}
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// SetMulticast sets the IP destination to multicastAddr and derives the
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// Ethernet destination MAC from it. It supports IPv4 (RFC 1112 §6.4) and
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// IPv6 (RFC 2464 §7) multicast MAC mapping.
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func SetMulticast(ethernetCarrier []byte, ipOff int, multicastAddr []byte) (err error) {
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ip := ethernetCarrier[ipOff:]
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mac := ethernetCarrier[0:6]
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version := ip[0] >> 4
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switch version {
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case 4:
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if len(multicastAddr) != 4 {
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return lneto.ErrMismatchLen
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}
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copy(ip[16:20], multicastAddr)
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// IPv4 multicast MAC: 01:00:5e + low 23 bits of IP destination.
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mac[0] = 0x01
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mac[1] = 0x00
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mac[2] = 0x5e
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mac[3] = multicastAddr[1] & 0x7f
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mac[4] = multicastAddr[2]
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mac[5] = multicastAddr[3]
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case 6:
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if len(multicastAddr) != 16 {
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return lneto.ErrMismatchLen
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}
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copy(ip[24:40], multicastAddr)
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// IPv6 multicast MAC: 33:33 + last 4 bytes of IP destination.
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mac[0] = 0x33
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mac[1] = 0x33
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mac[2] = multicastAddr[12]
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mac[3] = multicastAddr[13]
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mac[4] = multicastAddr[14]
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mac[5] = multicastAddr[15]
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default:
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return lneto.ErrUnsupported
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}
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return nil
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}
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