mirror of
https://github.com/octoleo/syncthing.git
synced 2024-11-08 22:31:04 +00:00
Send external announcements
This commit is contained in:
Jakob Borg
parent
8e65d36691
commit
e48222ada0
@ -4,31 +4,75 @@ served by something more standardized, such as mDNS / DNS-SD. In practice, this
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was much easier and quicker to get up and running.
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The mode of operation is to periodically (currently once every 30 seconds)
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transmit a broadcast UDP packet to the well known port number 21025. The packet
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has the following format:
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broadcast an Announcement packet to UDP port 21025. The packet has the
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following format:
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Magic Number |
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| Magic Number (0x20121025) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Port Number | Length of NodeID |
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| Port Number | Reserved |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Length of NodeID |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/ /
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\ NodeID (variable length) \
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/ /
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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This is the XDR encoding of:
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struct Announcement {
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unsigned int Magic;
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unsigned short Port;
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string NodeID<>;
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}
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(Hence NodeID is padded to a multiple of 32 bits)
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The sending node's address is not encoded -- it is taken to be the source
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address of the announcement. Every time such a packet is received, a local
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table that maps NodeID to Address is updated. When the local node wants to
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connect to another node with the address specification 'dynamic', this table is
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consulted.
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For external discovery, an identical packet is sent every 30 minutes to the
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external discovery server. The server keeps information for up to 60 minutes.
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To query the server, and UDP packet with the format below is sent.
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Magic Number (0x19760309) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Length of NodeID |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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/ /
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\ NodeID (variable length) \
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/ /
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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This is the XDR encoding of:
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struct Announcement {
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unsigned int Magic;
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string NodeID<>;
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}
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(Hence NodeID is padded to a multiple of 32 bits)
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It is answered with an announcement packet for the queried node ID if the
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information is available. There is no answer for queries about unknown nodes. A
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reasonable timeout is recommended instead. (This, combined with server side
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rate limits for packets per source IP and queries per node ID, prevents the
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server from being used as an amplifier in a DDoS attack.)
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*/
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package discover
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import (
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"encoding/binary"
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"errors"
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"fmt"
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"log"
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"net"
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@ -36,14 +80,34 @@ import (
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"time"
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)
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const (
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AnnouncementPort = 21025
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AnnouncementMagic = 0x20121025
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QueryMagic = 0x19760309
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)
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var (
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errBadMagic = errors.New("bad magic")
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errFormat = errors.New("incorrect packet format")
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)
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type Discoverer struct {
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MyID string
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ListenPort int
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BroadcastIntv time.Duration
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ExtListenPort int
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ExtBroadcastIntv time.Duration
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conn *net.UDPConn
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registry map[string]string
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registryLock sync.RWMutex
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extServer string
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}
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type packet struct {
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magic uint32 // AnnouncementMagic or QueryMagic
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port uint16 // unset if magic == QueryMagic
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id string
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}
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// We tolerate a certain amount of errors because we might be running in
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@ -51,8 +115,8 @@ type Discoverer struct {
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// When we hit this many errors in succession, we stop.
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const maxErrors = 30
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func NewDiscoverer(id string, port int) (*Discoverer, error) {
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local4 := &net.UDPAddr{IP: net.IP{0, 0, 0, 0}, Port: 21025}
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func NewDiscoverer(id string, port int, extPort int, extServer string) (*Discoverer, error) {
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local4 := &net.UDPAddr{IP: net.IP{0, 0, 0, 0}, Port: AnnouncementPort}
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conn, err := net.ListenUDP("udp4", local4)
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if err != nil {
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return nil, err
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@ -62,39 +126,60 @@ func NewDiscoverer(id string, port int) (*Discoverer, error) {
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MyID: id,
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ListenPort: port,
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BroadcastIntv: 30 * time.Second,
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ExtListenPort: extPort,
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ExtBroadcastIntv: 1800 * time.Second,
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conn: conn,
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registry: make(map[string]string),
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extServer: extServer,
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}
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go disc.sendAnnouncements()
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go disc.recvAnnouncements()
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if disc.ListenPort > 0 {
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disc.sendAnnouncements()
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}
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if len(disc.extServer) > 0 && disc.ExtListenPort > 0 {
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disc.sendExtAnnouncements()
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}
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return disc, nil
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}
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func (d *Discoverer) sendAnnouncements() {
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remote4 := &net.UDPAddr{IP: net.IP{255, 255, 255, 255}, Port: 21025}
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remote4 := &net.UDPAddr{IP: net.IP{255, 255, 255, 255}, Port: AnnouncementPort}
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idbs := []byte(d.MyID)
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buf := make([]byte, 4+4+4+len(idbs))
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buf := encodePacket(packet{AnnouncementMagic, uint16(d.ListenPort), d.MyID})
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go d.writeAnnouncements(buf, remote4, d.BroadcastIntv)
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}
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binary.BigEndian.PutUint32(buf, uint32(0x121025))
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binary.BigEndian.PutUint16(buf[4:], uint16(d.ListenPort))
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binary.BigEndian.PutUint16(buf[6:], uint16(len(idbs)))
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copy(buf[8:], idbs)
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func (d *Discoverer) sendExtAnnouncements() {
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extIPs, err := net.LookupIP(d.extServer)
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if err != nil {
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log.Printf("discover/external: %v; no external announcements", err)
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return
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}
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buf := encodePacket(packet{AnnouncementMagic, uint16(d.ExtListenPort), d.MyID})
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for _, extIP := range extIPs {
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remote4 := &net.UDPAddr{IP: extIP, Port: AnnouncementPort}
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go d.writeAnnouncements(buf, remote4, d.ExtBroadcastIntv)
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}
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}
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func (d *Discoverer) writeAnnouncements(buf []byte, remote *net.UDPAddr, intv time.Duration) {
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var errCounter = 0
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var err error
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for errCounter < maxErrors {
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_, _, err = d.conn.WriteMsgUDP(buf, nil, remote4)
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_, _, err = d.conn.WriteMsgUDP(buf, nil, remote)
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if err != nil {
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errCounter++
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} else {
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errCounter = 0
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}
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time.Sleep(d.BroadcastIntv)
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time.Sleep(intv)
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}
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log.Println("discover/write: stopping due to too many errors:", err)
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log.Println("discover/write: %v: stopping due to too many errors:", remote, err)
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}
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func (d *Discoverer) recvAnnouncements() {
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@ -102,26 +187,27 @@ func (d *Discoverer) recvAnnouncements() {
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var errCounter = 0
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var err error
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for errCounter < maxErrors {
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_, addr, err := d.conn.ReadFromUDP(buf)
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n, addr, err := d.conn.ReadFromUDP(buf)
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if err != nil {
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errCounter++
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time.Sleep(time.Second)
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continue
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}
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errCounter = 0
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magic := binary.BigEndian.Uint32(buf)
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if magic != 0x121025 {
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pkt, err := decodePacket(buf[:n])
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if err != nil || pkt.magic != AnnouncementMagic {
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errCounter++
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time.Sleep(time.Second)
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continue
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}
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port := binary.BigEndian.Uint16(buf[4:])
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l := binary.BigEndian.Uint16(buf[6:])
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idbs := buf[8 : l+8]
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id := string(idbs)
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if id != d.MyID {
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nodeAddr := fmt.Sprintf("%s:%d", addr.IP.String(), port)
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errCounter = 0
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if pkt.id != d.MyID {
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nodeAddr := fmt.Sprintf("%s:%d", addr.IP.String(), pkt.port)
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d.registryLock.Lock()
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if d.registry[id] != nodeAddr {
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d.registry[id] = nodeAddr
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if d.registry[pkt.id] != nodeAddr {
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d.registry[pkt.id] = nodeAddr
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}
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d.registryLock.Unlock()
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}
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@ -135,3 +221,87 @@ func (d *Discoverer) Lookup(node string) (string, bool) {
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addr, ok := d.registry[node]
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return addr, ok
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}
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func encodePacket(pkt packet) []byte {
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var idbs = []byte(pkt.id)
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var l = len(idbs) + pad(len(idbs)) + 4 + 4
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if pkt.magic == AnnouncementMagic {
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l += 4
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}
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var buf = make([]byte, l)
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var offset = 0
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binary.BigEndian.PutUint32(buf[offset:], pkt.magic)
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offset += 4
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if pkt.magic == AnnouncementMagic {
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binary.BigEndian.PutUint16(buf[offset:], uint16(pkt.port))
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offset += 4
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}
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binary.BigEndian.PutUint32(buf[offset:], uint32(len(idbs)))
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offset += 4
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copy(buf[offset:], idbs)
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return buf
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}
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func decodePacket(buf []byte) (*packet, error) {
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var p packet
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var offset int
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if len(buf) < 4 {
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// short packet
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return nil, errFormat
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}
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p.magic = binary.BigEndian.Uint32(buf[offset:])
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offset += 4
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if p.magic != AnnouncementMagic && p.magic != QueryMagic {
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return nil, errBadMagic
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}
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if p.magic == AnnouncementMagic {
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if len(buf) < offset+4 {
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// short packet
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return nil, errFormat
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}
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p.port = binary.BigEndian.Uint16(buf[offset:])
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offset += 2
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reserved := binary.BigEndian.Uint16(buf[offset:])
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if reserved != 0 {
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return nil, errFormat
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}
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offset += 2
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}
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if len(buf) < offset+4 {
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// short packet
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return nil, errFormat
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}
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l := binary.BigEndian.Uint32(buf[offset:])
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offset += 4
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if len(buf) < offset+int(l)+pad(int(l)) {
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// short packet
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return nil, errFormat
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}
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idbs := buf[offset : offset+int(l)]
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p.id = string(idbs)
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offset += int(l) + pad(int(l))
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if len(buf[offset:]) > 0 {
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// extra data
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return nil, errFormat
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}
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return &p, nil
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}
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func pad(l int) int {
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d := l % 4
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if d == 0 {
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return 0
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}
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return 4 - d
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}
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111
discover/discover_test.go
Normal file
111
discover/discover_test.go
Normal file
@ -0,0 +1,111 @@
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package discover
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import (
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"bytes"
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"reflect"
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"testing"
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)
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var testdata = []struct {
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data []byte
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packet *packet
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err error
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}{
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{
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[]byte{0x20, 0x12, 0x10, 0x25,
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0x12, 0x34, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x05,
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0x68, 0x65, 0x6c, 0x6c, 0x6f, 0x00, 0x00, 0x00},
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&packet{
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magic: 0x20121025,
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port: 0x1234,
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id: "hello",
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},
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nil,
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},
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{
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[]byte{0x20, 0x12, 0x10, 0x25,
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0x34, 0x56, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x08,
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0x68, 0x65, 0x6c, 0x6c, 0x6f, 0x21, 0x21, 0x21},
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&packet{
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magic: 0x20121025,
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port: 0x3456,
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id: "hello!!!",
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},
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nil,
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},
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{
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[]byte{0x19, 0x76, 0x03, 0x09,
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0x00, 0x00, 0x00, 0x06,
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0x68, 0x65, 0x6c, 0x6c, 0x6f, 0x21, 0x00, 0x00},
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&packet{
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magic: 0x19760309,
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id: "hello!",
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},
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nil,
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},
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{
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[]byte{0x20, 0x12, 0x10, 0x25,
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0x12, 0x34, 0x12, 0x34, // reserved bits not set to zero
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0x00, 0x00, 0x00, 0x06,
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0x68, 0x65, 0x6c, 0x6c, 0x6f, 0x21, 0x00, 0x00},
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nil,
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errFormat,
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},
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{
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[]byte{0x20, 0x12, 0x10, 0x25,
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0x12, 0x34, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x06,
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0x68, 0x65, 0x6c, 0x6c, 0x6f, 0x21}, // missing padding
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nil,
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errFormat,
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},
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{
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[]byte{0x19, 0x77, 0x03, 0x09, // incorrect magic
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0x00, 0x00, 0x00, 0x06,
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0x68, 0x65, 0x6c, 0x6c, 0x6f, 0x21, 0x00, 0x00},
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nil,
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errBadMagic,
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},
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{
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[]byte{0x19, 0x76, 0x03, 0x09,
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0x6c, 0x6c, 0x6c, 0x6c, // length exceeds packet size
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0x68, 0x65, 0x6c, 0x6c, 0x6f, 0x21, 0x00, 0x00},
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nil,
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errFormat,
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},
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{
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[]byte{0x19, 0x76, 0x03, 0x09,
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0x00, 0x00, 0x00, 0x06,
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0x68, 0x65, 0x6c, 0x6c, 0x6f, 0x21, 0x00, 0x00,
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0x23}, // extra data at the end
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nil,
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errFormat,
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},
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}
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func TestDecodePacket(t *testing.T) {
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for i, test := range testdata {
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p, err := decodePacket(test.data)
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if err != test.err {
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t.Errorf("%d: unexpected error %v", i, err)
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} else {
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if !reflect.DeepEqual(p, test.packet) {
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t.Errorf("%d: incorrect packet\n%v\n%v", i, test.packet, p)
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}
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}
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}
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}
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func TestEncodePacket(t *testing.T) {
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for i, test := range testdata {
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if test.err != nil {
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continue
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}
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buf := encodePacket(*test.packet)
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if bytes.Compare(buf, test.data) != 0 {
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t.Errorf("%d: incorrect encoded packet\n% x\n% 0x", i, test.data, buf)
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}
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}
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}
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34
main.go
34
main.go
@ -23,11 +23,12 @@ import (
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type Options struct {
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ConfDir string `short:"c" long:"cfg" description:"Configuration directory" default:"~/.syncthing" value-name:"DIR"`
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Listen string `short:"l" long:"listen" description:"Listen address" default:":22000" value-name:"ADDR"`
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ReadOnly bool `long:"ro" description:"Repository is read only"`
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Delete bool `long:"delete" description:"Delete files from repo when deleted from cluster"`
|
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ReadOnly bool `short:"r" long:"ro" description:"Repository is read only"`
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Delete bool `short:"d" long:"delete" description:"Delete files from repo when deleted from cluster"`
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NoSymlinks bool `long:"no-symlinks" description:"Don't follow first level symlinks in the repo"`
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ScanInterval time.Duration `long:"scan-intv" description:"Repository scan interval" default:"60s" value-name:"INTV"`
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ConnInterval time.Duration `long:"conn-intv" description:"Node reconnect interval" default:"60s" value-name:"INTV"`
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Discovery DiscoveryOptions `group:"Discovery Options"`
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Debug DebugOptions `group:"Debugging Options"`
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}
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@ -35,7 +36,14 @@ type DebugOptions struct {
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TraceFile bool `long:"trace-file"`
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TraceNet bool `long:"trace-net"`
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TraceIdx bool `long:"trace-idx"`
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Profiler string `long:"profiler"`
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Profiler string `long:"profiler" value-name:"ADDR"`
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}
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type DiscoveryOptions struct {
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ExternalServer string `long:"ext-server" description:"External discovery server" value-name:"NAME" default:"syncthing.nym.se"`
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ExternalPort int `short:"e" long:"ext-port" description:"External listen port" value-name:"PORT" default:"22000"`
|
||||
NoExternalDiscovery bool `short:"n" long:"no-ext-announce" description:"Do not announce presence externally"`
|
||||
NoLocalDiscovery bool `short:"N" long:"no-local-announce" description:"Do not announce presence locally"`
|
||||
}
|
||||
|
||||
var opts Options
|
||||
@ -206,8 +214,6 @@ listen:
|
||||
continue listen
|
||||
}
|
||||
}
|
||||
|
||||
warnln("Connect from unknown node", remoteID)
|
||||
conn.Close()
|
||||
}
|
||||
}
|
||||
@ -217,10 +223,22 @@ func connect(myID string, addr string, nodeAddrs map[string][]string, m *Model,
|
||||
fatalErr(err)
|
||||
port, _ := strconv.Atoi(portstr)
|
||||
|
||||
infoln("Starting local discovery")
|
||||
disc, err := discover.NewDiscoverer(myID, port)
|
||||
if opts.Discovery.NoLocalDiscovery {
|
||||
port = -1
|
||||
} else {
|
||||
infoln("Sending local discovery announcements")
|
||||
}
|
||||
|
||||
if opts.Discovery.NoExternalDiscovery {
|
||||
opts.Discovery.ExternalPort = -1
|
||||
} else {
|
||||
infoln("Sending external discovery announcements")
|
||||
}
|
||||
|
||||
disc, err := discover.NewDiscoverer(myID, port, opts.Discovery.ExternalPort, opts.Discovery.ExternalServer)
|
||||
|
||||
if err != nil {
|
||||
warnln("No local discovery possible")
|
||||
warnf("No discovery possible (%v)", err)
|
||||
}
|
||||
|
||||
for {
|
||||
|
||||
Loading…
Reference in New Issue
Block a user