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https://github.com/mjl-/mox.git
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94 lines
3 KiB
Go
94 lines
3 KiB
Go
package smtpclient
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import (
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"context"
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"fmt"
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"log/slog"
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"net"
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"time"
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"github.com/mjl-/mox/dns"
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"github.com/mjl-/mox/mlog"
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)
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// DialHook can be used during tests to override the regular dialer from being used.
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var DialHook func(ctx context.Context, dialer Dialer, timeout time.Duration, addr string, laddr net.Addr) (net.Conn, error)
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func dial(ctx context.Context, dialer Dialer, timeout time.Duration, addr string, laddr net.Addr) (net.Conn, error) {
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// todo: see if we can remove this function and DialHook in favor of the Dialer interface.
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if DialHook != nil {
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return DialHook(ctx, dialer, timeout, addr, laddr)
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}
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// If this is a net.Dialer, use its settings and add the timeout and localaddr.
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// This is the typical case, but SOCKS5 support can use a different dialer.
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if d, ok := dialer.(*net.Dialer); ok {
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nd := *d
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nd.Timeout = timeout
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nd.LocalAddr = laddr
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return nd.DialContext(ctx, "tcp", addr)
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}
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return dialer.DialContext(ctx, "tcp", addr)
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}
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// Dialer is used to dial mail servers, an interface to facilitate testing.
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type Dialer interface {
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DialContext(ctx context.Context, network, addr string) (c net.Conn, err error)
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}
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// Dial connects to host by dialing ips, taking previous attempts in dialedIPs into
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// accounts (for greylisting, blocklisting and ipv4/ipv6).
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//
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// If the previous attempt used IPv4, this attempt will use IPv6 (useful in case
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// one of the IPs is in a DNSBL).
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//
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// The second attempt for an address family we prefer the same IP as earlier, to
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// increase our chances if remote is doing greylisting.
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//
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// Dial updates dialedIPs, callers may want to save it so it can be taken into
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// account for future delivery attempts.
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//
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// The first matching protocol family from localIPs is set for the local side
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// of the TCP connection.
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func Dial(ctx context.Context, elog *slog.Logger, dialer Dialer, host dns.IPDomain, ips []net.IP, port int, dialedIPs map[string][]net.IP, localIPs []net.IP) (conn net.Conn, ip net.IP, rerr error) {
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log := mlog.New("smtpclient", elog)
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timeout := 30 * time.Second
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if deadline, ok := ctx.Deadline(); ok && len(ips) > 0 {
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timeout = time.Until(deadline) / time.Duration(len(ips))
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}
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var lastErr error
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var lastIP net.IP
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for _, ip := range ips {
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addr := net.JoinHostPort(ip.String(), fmt.Sprintf("%d", port))
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log.Debug("dialing host", slog.String("addr", addr))
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var laddr net.Addr
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for _, lip := range localIPs {
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ipIs4 := ip.To4() != nil
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lipIs4 := lip.To4() != nil
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if ipIs4 == lipIs4 {
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laddr = &net.TCPAddr{IP: lip}
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break
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}
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}
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conn, err := dial(ctx, dialer, timeout, addr, laddr)
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if err == nil {
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log.Debug("connected to host",
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slog.Any("host", host),
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slog.String("addr", addr),
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slog.Any("laddr", laddr))
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name := host.String()
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dialedIPs[name] = append(dialedIPs[name], ip)
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return conn, ip, nil
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}
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log.Debugx("connection attempt", err,
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slog.Any("host", host),
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slog.String("addr", addr),
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slog.Any("laddr", laddr))
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lastErr = err
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lastIP = ip
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}
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// todo: possibly return all errors joined?
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return nil, lastIP, lastErr
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}
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