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- // Copyright 2010 The Go Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style
- // license that can be found in the LICENSE file.
- package net
- import (
- "context"
- "internal/nettrace"
- "syscall"
- "time"
- )
- // defaultTCPKeepAlive is a default constant value for TCPKeepAlive times
- // See golang.org/issue/31510
- const (
- defaultTCPKeepAlive = 15 * time.Second
- )
- // A Dialer contains options for connecting to an address.
- //
- // The zero value for each field is equivalent to dialing
- // without that option. Dialing with the zero value of Dialer
- // is therefore equivalent to just calling the Dial function.
- //
- // It is safe to call Dialer's methods concurrently.
- type Dialer struct {
- // Timeout is the maximum amount of time a dial will wait for
- // a connect to complete. If Deadline is also set, it may fail
- // earlier.
- //
- // The default is no timeout.
- //
- // When using TCP and dialing a host name with multiple IP
- // addresses, the timeout may be divided between them.
- //
- // With or without a timeout, the operating system may impose
- // its own earlier timeout. For instance, TCP timeouts are
- // often around 3 minutes.
- Timeout time.Duration
- // Deadline is the absolute point in time after which dials
- // will fail. If Timeout is set, it may fail earlier.
- // Zero means no deadline, or dependent on the operating system
- // as with the Timeout option.
- Deadline time.Time
- // LocalAddr is the local address to use when dialing an
- // address. The address must be of a compatible type for the
- // network being dialed.
- // If nil, a local address is automatically chosen.
- LocalAddr Addr
- // DualStack previously enabled RFC 6555 Fast Fallback
- // support, also known as "Happy Eyeballs", in which IPv4 is
- // tried soon if IPv6 appears to be misconfigured and
- // hanging.
- //
- // Deprecated: Fast Fallback is enabled by default. To
- // disable, set FallbackDelay to a negative value.
- DualStack bool
- // FallbackDelay specifies the length of time to wait before
- // spawning a RFC 6555 Fast Fallback connection. That is, this
- // is the amount of time to wait for IPv6 to succeed before
- // assuming that IPv6 is misconfigured and falling back to
- // IPv4.
- //
- // If zero, a default delay of 300ms is used.
- // A negative value disables Fast Fallback support.
- FallbackDelay time.Duration
- // KeepAlive specifies the interval between keep-alive
- // probes for an active network connection.
- // If zero, keep-alive probes are sent with a default value
- // (currently 15 seconds), if supported by the protocol and operating
- // system. Network protocols or operating systems that do
- // not support keep-alives ignore this field.
- // If negative, keep-alive probes are disabled.
- KeepAlive time.Duration
- // Resolver optionally specifies an alternate resolver to use.
- Resolver *Resolver
- // Cancel is an optional channel whose closure indicates that
- // the dial should be canceled. Not all types of dials support
- // cancellation.
- //
- // Deprecated: Use DialContext instead.
- Cancel <-chan struct{}
- // If Control is not nil, it is called after creating the network
- // connection but before actually dialing.
- //
- // Network and address parameters passed to Control method are not
- // necessarily the ones passed to Dial. For example, passing "tcp" to Dial
- // will cause the Control function to be called with "tcp4" or "tcp6".
- Control func(network, address string, c syscall.RawConn) error
- }
- func (d *Dialer) dualStack() bool { return d.FallbackDelay >= 0 }
- func minNonzeroTime(a, b time.Time) time.Time {
- if a.IsZero() {
- return b
- }
- if b.IsZero() || a.Before(b) {
- return a
- }
- return b
- }
- // deadline returns the earliest of:
- // - now+Timeout
- // - d.Deadline
- // - the context's deadline
- // Or zero, if none of Timeout, Deadline, or context's deadline is set.
- func (d *Dialer) deadline(ctx context.Context, now time.Time) (earliest time.Time) {
- if d.Timeout != 0 { // including negative, for historical reasons
- earliest = now.Add(d.Timeout)
- }
- if d, ok := ctx.Deadline(); ok {
- earliest = minNonzeroTime(earliest, d)
- }
- return minNonzeroTime(earliest, d.Deadline)
- }
- func (d *Dialer) resolver() *Resolver {
- if d.Resolver != nil {
- return d.Resolver
- }
- return DefaultResolver
- }
- // partialDeadline returns the deadline to use for a single address,
- // when multiple addresses are pending.
- func partialDeadline(now, deadline time.Time, addrsRemaining int) (time.Time, error) {
- if deadline.IsZero() {
- return deadline, nil
- }
- timeRemaining := deadline.Sub(now)
- if timeRemaining <= 0 {
- return time.Time{}, errTimeout
- }
- // Tentatively allocate equal time to each remaining address.
- timeout := timeRemaining / time.Duration(addrsRemaining)
- // If the time per address is too short, steal from the end of the list.
- const saneMinimum = 2 * time.Second
- if timeout < saneMinimum {
- if timeRemaining < saneMinimum {
- timeout = timeRemaining
- } else {
- timeout = saneMinimum
- }
- }
- return now.Add(timeout), nil
- }
- func (d *Dialer) fallbackDelay() time.Duration {
- if d.FallbackDelay > 0 {
- return d.FallbackDelay
- } else {
- return 300 * time.Millisecond
- }
- }
- func parseNetwork(ctx context.Context, network string, needsProto bool) (afnet string, proto int, err error) {
- i := last(network, ':')
- if i < 0 { // no colon
- switch network {
- case "tcp", "tcp4", "tcp6":
- case "udp", "udp4", "udp6":
- case "ip", "ip4", "ip6":
- if needsProto {
- return "", 0, UnknownNetworkError(network)
- }
- case "unix", "unixgram", "unixpacket":
- default:
- return "", 0, UnknownNetworkError(network)
- }
- return network, 0, nil
- }
- afnet = network[:i]
- switch afnet {
- case "ip", "ip4", "ip6":
- protostr := network[i+1:]
- proto, i, ok := dtoi(protostr)
- if !ok || i != len(protostr) {
- proto, err = lookupProtocol(ctx, protostr)
- if err != nil {
- return "", 0, err
- }
- }
- return afnet, proto, nil
- }
- return "", 0, UnknownNetworkError(network)
- }
- // resolveAddrList resolves addr using hint and returns a list of
- // addresses. The result contains at least one address when error is
- // nil.
- func (r *Resolver) resolveAddrList(ctx context.Context, op, network, addr string, hint Addr) (addrList, error) {
- afnet, _, err := parseNetwork(ctx, network, true)
- if err != nil {
- return nil, err
- }
- if op == "dial" && addr == "" {
- return nil, errMissingAddress
- }
- switch afnet {
- case "unix", "unixgram", "unixpacket":
- addr, err := ResolveUnixAddr(afnet, addr)
- if err != nil {
- return nil, err
- }
- if op == "dial" && hint != nil && addr.Network() != hint.Network() {
- return nil, &AddrError{Err: "mismatched local address type", Addr: hint.String()}
- }
- return addrList{addr}, nil
- }
- addrs, err := r.internetAddrList(ctx, afnet, addr)
- if err != nil || op != "dial" || hint == nil {
- return addrs, err
- }
- var (
- tcp *TCPAddr
- udp *UDPAddr
- ip *IPAddr
- wildcard bool
- )
- switch hint := hint.(type) {
- case *TCPAddr:
- tcp = hint
- wildcard = tcp.isWildcard()
- case *UDPAddr:
- udp = hint
- wildcard = udp.isWildcard()
- case *IPAddr:
- ip = hint
- wildcard = ip.isWildcard()
- }
- naddrs := addrs[:0]
- for _, addr := range addrs {
- if addr.Network() != hint.Network() {
- return nil, &AddrError{Err: "mismatched local address type", Addr: hint.String()}
- }
- switch addr := addr.(type) {
- case *TCPAddr:
- if !wildcard && !addr.isWildcard() && !addr.IP.matchAddrFamily(tcp.IP) {
- continue
- }
- naddrs = append(naddrs, addr)
- case *UDPAddr:
- if !wildcard && !addr.isWildcard() && !addr.IP.matchAddrFamily(udp.IP) {
- continue
- }
- naddrs = append(naddrs, addr)
- case *IPAddr:
- if !wildcard && !addr.isWildcard() && !addr.IP.matchAddrFamily(ip.IP) {
- continue
- }
- naddrs = append(naddrs, addr)
- }
- }
- if len(naddrs) == 0 {
- return nil, &AddrError{Err: errNoSuitableAddress.Error(), Addr: hint.String()}
- }
- return naddrs, nil
- }
- // Dial connects to the address on the named network.
- //
- // Known networks are "tcp", "tcp4" (IPv4-only), "tcp6" (IPv6-only),
- // "udp", "udp4" (IPv4-only), "udp6" (IPv6-only), "ip", "ip4"
- // (IPv4-only), "ip6" (IPv6-only), "unix", "unixgram" and
- // "unixpacket".
- //
- // For TCP and UDP networks, the address has the form "host:port".
- // The host must be a literal IP address, or a host name that can be
- // resolved to IP addresses.
- // The port must be a literal port number or a service name.
- // If the host is a literal IPv6 address it must be enclosed in square
- // brackets, as in "[2001:db8::1]:80" or "[fe80::1%zone]:80".
- // The zone specifies the scope of the literal IPv6 address as defined
- // in RFC 4007.
- // The functions JoinHostPort and SplitHostPort manipulate a pair of
- // host and port in this form.
- // When using TCP, and the host resolves to multiple IP addresses,
- // Dial will try each IP address in order until one succeeds.
- //
- // Examples:
- // Dial("tcp", "golang.org:http")
- // Dial("tcp", "192.0.2.1:http")
- // Dial("tcp", "198.51.100.1:80")
- // Dial("udp", "[2001:db8::1]:domain")
- // Dial("udp", "[fe80::1%lo0]:53")
- // Dial("tcp", ":80")
- //
- // For IP networks, the network must be "ip", "ip4" or "ip6" followed
- // by a colon and a literal protocol number or a protocol name, and
- // the address has the form "host". The host must be a literal IP
- // address or a literal IPv6 address with zone.
- // It depends on each operating system how the operating system
- // behaves with a non-well known protocol number such as "0" or "255".
- //
- // Examples:
- // Dial("ip4:1", "192.0.2.1")
- // Dial("ip6:ipv6-icmp", "2001:db8::1")
- // Dial("ip6:58", "fe80::1%lo0")
- //
- // For TCP, UDP and IP networks, if the host is empty or a literal
- // unspecified IP address, as in ":80", "0.0.0.0:80" or "[::]:80" for
- // TCP and UDP, "", "0.0.0.0" or "::" for IP, the local system is
- // assumed.
- //
- // For Unix networks, the address must be a file system path.
- func Dial(network, address string) (Conn, error) {
- var d Dialer
- return d.Dial(network, address)
- }
- // DialTimeout acts like Dial but takes a timeout.
- //
- // The timeout includes name resolution, if required.
- // When using TCP, and the host in the address parameter resolves to
- // multiple IP addresses, the timeout is spread over each consecutive
- // dial, such that each is given an appropriate fraction of the time
- // to connect.
- //
- // See func Dial for a description of the network and address
- // parameters.
- func DialTimeout(network, address string, timeout time.Duration) (Conn, error) {
- d := Dialer{Timeout: timeout}
- return d.Dial(network, address)
- }
- // sysDialer contains a Dial's parameters and configuration.
- type sysDialer struct {
- Dialer
- network, address string
- }
- // Dial connects to the address on the named network.
- //
- // See func Dial for a description of the network and address
- // parameters.
- //
- // Dial uses context.Background internally; to specify the context, use
- // DialContext.
- func (d *Dialer) Dial(network, address string) (Conn, error) {
- return d.DialContext(context.Background(), network, address)
- }
- // DialContext connects to the address on the named network using
- // the provided context.
- //
- // The provided Context must be non-nil. If the context expires before
- // the connection is complete, an error is returned. Once successfully
- // connected, any expiration of the context will not affect the
- // connection.
- //
- // When using TCP, and the host in the address parameter resolves to multiple
- // network addresses, any dial timeout (from d.Timeout or ctx) is spread
- // over each consecutive dial, such that each is given an appropriate
- // fraction of the time to connect.
- // For example, if a host has 4 IP addresses and the timeout is 1 minute,
- // the connect to each single address will be given 15 seconds to complete
- // before trying the next one.
- //
- // See func Dial for a description of the network and address
- // parameters.
- func (d *Dialer) DialContext(ctx context.Context, network, address string) (Conn, error) {
- if ctx == nil {
- panic("nil context")
- }
- deadline := d.deadline(ctx, time.Now())
- if !deadline.IsZero() {
- if d, ok := ctx.Deadline(); !ok || deadline.Before(d) {
- subCtx, cancel := context.WithDeadline(ctx, deadline)
- defer cancel()
- ctx = subCtx
- }
- }
- if oldCancel := d.Cancel; oldCancel != nil {
- subCtx, cancel := context.WithCancel(ctx)
- defer cancel()
- go func() {
- select {
- case <-oldCancel:
- cancel()
- case <-subCtx.Done():
- }
- }()
- ctx = subCtx
- }
- // Shadow the nettrace (if any) during resolve so Connect events don't fire for DNS lookups.
- resolveCtx := ctx
- if trace, _ := ctx.Value(nettrace.TraceKey{}).(*nettrace.Trace); trace != nil {
- shadow := *trace
- shadow.ConnectStart = nil
- shadow.ConnectDone = nil
- resolveCtx = context.WithValue(resolveCtx, nettrace.TraceKey{}, &shadow)
- }
- addrs, err := d.resolver().resolveAddrList(resolveCtx, "dial", network, address, d.LocalAddr)
- if err != nil {
- return nil, &OpError{Op: "dial", Net: network, Source: nil, Addr: nil, Err: err}
- }
- sd := &sysDialer{
- Dialer: *d,
- network: network,
- address: address,
- }
- var primaries, fallbacks addrList
- if d.dualStack() && network == "tcp" {
- primaries, fallbacks = addrs.partition(isIPv4)
- } else {
- primaries = addrs
- }
- var c Conn
- if len(fallbacks) > 0 {
- c, err = sd.dialParallel(ctx, primaries, fallbacks)
- } else {
- c, err = sd.dialSerial(ctx, primaries)
- }
- if err != nil {
- return nil, err
- }
- if tc, ok := c.(*TCPConn); ok && d.KeepAlive >= 0 {
- setKeepAlive(tc.fd, true)
- ka := d.KeepAlive
- if d.KeepAlive == 0 {
- ka = defaultTCPKeepAlive
- }
- setKeepAlivePeriod(tc.fd, ka)
- testHookSetKeepAlive(ka)
- }
- return c, nil
- }
- // dialParallel races two copies of dialSerial, giving the first a
- // head start. It returns the first established connection and
- // closes the others. Otherwise it returns an error from the first
- // primary address.
- func (sd *sysDialer) dialParallel(ctx context.Context, primaries, fallbacks addrList) (Conn, error) {
- if len(fallbacks) == 0 {
- return sd.dialSerial(ctx, primaries)
- }
- returned := make(chan struct{})
- defer close(returned)
- type dialResult struct {
- Conn
- error
- primary bool
- done bool
- }
- results := make(chan dialResult) // unbuffered
- startRacer := func(ctx context.Context, primary bool) {
- ras := primaries
- if !primary {
- ras = fallbacks
- }
- c, err := sd.dialSerial(ctx, ras)
- select {
- case results <- dialResult{Conn: c, error: err, primary: primary, done: true}:
- case <-returned:
- if c != nil {
- c.Close()
- }
- }
- }
- var primary, fallback dialResult
- // Start the main racer.
- primaryCtx, primaryCancel := context.WithCancel(ctx)
- defer primaryCancel()
- go startRacer(primaryCtx, true)
- // Start the timer for the fallback racer.
- fallbackTimer := time.NewTimer(sd.fallbackDelay())
- defer fallbackTimer.Stop()
- for {
- select {
- case <-fallbackTimer.C:
- fallbackCtx, fallbackCancel := context.WithCancel(ctx)
- defer fallbackCancel()
- go startRacer(fallbackCtx, false)
- case res := <-results:
- if res.error == nil {
- return res.Conn, nil
- }
- if res.primary {
- primary = res
- } else {
- fallback = res
- }
- if primary.done && fallback.done {
- return nil, primary.error
- }
- if res.primary && fallbackTimer.Stop() {
- // If we were able to stop the timer, that means it
- // was running (hadn't yet started the fallback), but
- // we just got an error on the primary path, so start
- // the fallback immediately (in 0 nanoseconds).
- fallbackTimer.Reset(0)
- }
- }
- }
- }
- // dialSerial connects to a list of addresses in sequence, returning
- // either the first successful connection, or the first error.
- func (sd *sysDialer) dialSerial(ctx context.Context, ras addrList) (Conn, error) {
- var firstErr error // The error from the first address is most relevant.
- for i, ra := range ras {
- select {
- case <-ctx.Done():
- return nil, &OpError{Op: "dial", Net: sd.network, Source: sd.LocalAddr, Addr: ra, Err: mapErr(ctx.Err())}
- default:
- }
- dialCtx := ctx
- if deadline, hasDeadline := ctx.Deadline(); hasDeadline {
- partialDeadline, err := partialDeadline(time.Now(), deadline, len(ras)-i)
- if err != nil {
- // Ran out of time.
- if firstErr == nil {
- firstErr = &OpError{Op: "dial", Net: sd.network, Source: sd.LocalAddr, Addr: ra, Err: err}
- }
- break
- }
- if partialDeadline.Before(deadline) {
- var cancel context.CancelFunc
- dialCtx, cancel = context.WithDeadline(ctx, partialDeadline)
- defer cancel()
- }
- }
- c, err := sd.dialSingle(dialCtx, ra)
- if err == nil {
- return c, nil
- }
- if firstErr == nil {
- firstErr = err
- }
- }
- if firstErr == nil {
- firstErr = &OpError{Op: "dial", Net: sd.network, Source: nil, Addr: nil, Err: errMissingAddress}
- }
- return nil, firstErr
- }
- // dialSingle attempts to establish and returns a single connection to
- // the destination address.
- func (sd *sysDialer) dialSingle(ctx context.Context, ra Addr) (c Conn, err error) {
- trace, _ := ctx.Value(nettrace.TraceKey{}).(*nettrace.Trace)
- if trace != nil {
- raStr := ra.String()
- if trace.ConnectStart != nil {
- trace.ConnectStart(sd.network, raStr)
- }
- if trace.ConnectDone != nil {
- defer func() { trace.ConnectDone(sd.network, raStr, err) }()
- }
- }
- la := sd.LocalAddr
- switch ra := ra.(type) {
- case *TCPAddr:
- la, _ := la.(*TCPAddr)
- c, err = sd.dialTCP(ctx, la, ra)
- case *UDPAddr:
- la, _ := la.(*UDPAddr)
- c, err = sd.dialUDP(ctx, la, ra)
- case *IPAddr:
- la, _ := la.(*IPAddr)
- c, err = sd.dialIP(ctx, la, ra)
- case *UnixAddr:
- la, _ := la.(*UnixAddr)
- c, err = sd.dialUnix(ctx, la, ra)
- default:
- return nil, &OpError{Op: "dial", Net: sd.network, Source: la, Addr: ra, Err: &AddrError{Err: "unexpected address type", Addr: sd.address}}
- }
- if err != nil {
- return nil, &OpError{Op: "dial", Net: sd.network, Source: la, Addr: ra, Err: err} // c is non-nil interface containing nil pointer
- }
- return c, nil
- }
- // ListenConfig contains options for listening to an address.
- type ListenConfig struct {
- // If Control is not nil, it is called after creating the network
- // connection but before binding it to the operating system.
- //
- // Network and address parameters passed to Control method are not
- // necessarily the ones passed to Listen. For example, passing "tcp" to
- // Listen will cause the Control function to be called with "tcp4" or "tcp6".
- Control func(network, address string, c syscall.RawConn) error
- // KeepAlive specifies the keep-alive period for network
- // connections accepted by this listener.
- // If zero, keep-alives are enabled if supported by the protocol
- // and operating system. Network protocols or operating systems
- // that do not support keep-alives ignore this field.
- // If negative, keep-alives are disabled.
- KeepAlive time.Duration
- }
- // Listen announces on the local network address.
- //
- // See func Listen for a description of the network and address
- // parameters.
- func (lc *ListenConfig) Listen(ctx context.Context, network, address string) (Listener, error) {
- addrs, err := DefaultResolver.resolveAddrList(ctx, "listen", network, address, nil)
- if err != nil {
- return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: nil, Err: err}
- }
- sl := &sysListener{
- ListenConfig: *lc,
- network: network,
- address: address,
- }
- var l Listener
- la := addrs.first(isIPv4)
- switch la := la.(type) {
- case *TCPAddr:
- l, err = sl.listenTCP(ctx, la)
- case *UnixAddr:
- l, err = sl.listenUnix(ctx, la)
- default:
- return nil, &OpError{Op: "listen", Net: sl.network, Source: nil, Addr: la, Err: &AddrError{Err: "unexpected address type", Addr: address}}
- }
- if err != nil {
- return nil, &OpError{Op: "listen", Net: sl.network, Source: nil, Addr: la, Err: err} // l is non-nil interface containing nil pointer
- }
- return l, nil
- }
- // ListenPacket announces on the local network address.
- //
- // See func ListenPacket for a description of the network and address
- // parameters.
- func (lc *ListenConfig) ListenPacket(ctx context.Context, network, address string) (PacketConn, error) {
- addrs, err := DefaultResolver.resolveAddrList(ctx, "listen", network, address, nil)
- if err != nil {
- return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: nil, Err: err}
- }
- sl := &sysListener{
- ListenConfig: *lc,
- network: network,
- address: address,
- }
- var c PacketConn
- la := addrs.first(isIPv4)
- switch la := la.(type) {
- case *UDPAddr:
- c, err = sl.listenUDP(ctx, la)
- case *IPAddr:
- c, err = sl.listenIP(ctx, la)
- case *UnixAddr:
- c, err = sl.listenUnixgram(ctx, la)
- default:
- return nil, &OpError{Op: "listen", Net: sl.network, Source: nil, Addr: la, Err: &AddrError{Err: "unexpected address type", Addr: address}}
- }
- if err != nil {
- return nil, &OpError{Op: "listen", Net: sl.network, Source: nil, Addr: la, Err: err} // c is non-nil interface containing nil pointer
- }
- return c, nil
- }
- // sysListener contains a Listen's parameters and configuration.
- type sysListener struct {
- ListenConfig
- network, address string
- }
- // Listen announces on the local network address.
- //
- // The network must be "tcp", "tcp4", "tcp6", "unix" or "unixpacket".
- //
- // For TCP networks, if the host in the address parameter is empty or
- // a literal unspecified IP address, Listen listens on all available
- // unicast and anycast IP addresses of the local system.
- // To only use IPv4, use network "tcp4".
- // The address can use a host name, but this is not recommended,
- // because it will create a listener for at most one of the host's IP
- // addresses.
- // If the port in the address parameter is empty or "0", as in
- // "127.0.0.1:" or "[::1]:0", a port number is automatically chosen.
- // The Addr method of Listener can be used to discover the chosen
- // port.
- //
- // See func Dial for a description of the network and address
- // parameters.
- //
- // Listen uses context.Background internally; to specify the context, use
- // ListenConfig.Listen.
- func Listen(network, address string) (Listener, error) {
- var lc ListenConfig
- return lc.Listen(context.Background(), network, address)
- }
- // ListenPacket announces on the local network address.
- //
- // The network must be "udp", "udp4", "udp6", "unixgram", or an IP
- // transport. The IP transports are "ip", "ip4", or "ip6" followed by
- // a colon and a literal protocol number or a protocol name, as in
- // "ip:1" or "ip:icmp".
- //
- // For UDP and IP networks, if the host in the address parameter is
- // empty or a literal unspecified IP address, ListenPacket listens on
- // all available IP addresses of the local system except multicast IP
- // addresses.
- // To only use IPv4, use network "udp4" or "ip4:proto".
- // The address can use a host name, but this is not recommended,
- // because it will create a listener for at most one of the host's IP
- // addresses.
- // If the port in the address parameter is empty or "0", as in
- // "127.0.0.1:" or "[::1]:0", a port number is automatically chosen.
- // The LocalAddr method of PacketConn can be used to discover the
- // chosen port.
- //
- // See func Dial for a description of the network and address
- // parameters.
- //
- // ListenPacket uses context.Background internally; to specify the context, use
- // ListenConfig.ListenPacket.
- func ListenPacket(network, address string) (PacketConn, error) {
- var lc ListenConfig
- return lc.ListenPacket(context.Background(), network, address)
- }
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