go-gemini/server.go
2021-02-22 21:33:23 -05:00

374 lines
8.8 KiB
Go

package gemini
import (
"context"
"crypto/tls"
"errors"
"log"
"net"
"sync"
"time"
)
// A Server defines parameters for running a Gemini server. The zero value for
// Server is a valid configuration.
type Server struct {
// Addr optionally specifies the TCP address for the server to listen on,
// in the form "host:port". If empty, ":1965" (port 1965) is used.
// See net.Dial for details of the address format.
Addr string
// The Handler to invoke.
Handler Handler
// ReadTimeout is the maximum duration for reading the entire
// request.
//
// A ReadTimeout of zero means no timeout.
ReadTimeout time.Duration
// WriteTimeout is the maximum duration before timing out
// writes of the response.
//
// A WriteTimeout of zero means no timeout.
WriteTimeout time.Duration
// GetCertificate returns a TLS certificate based on the given
// hostname.
//
// If GetCertificate is nil or returns nil, then no certificate
// will be used and the connection will be aborted.
GetCertificate func(hostname string) (*tls.Certificate, error)
// ErrorLog specifies an optional logger for errors accepting connections,
// unexpected behavior from handlers, and underlying file system errors.
// If nil, logging is done via the log package's standard logger.
ErrorLog *log.Logger
listeners map[*net.Listener]context.CancelFunc
conns map[*net.Conn]context.CancelFunc
closed bool // true if Closed or Shutdown called
shutdown bool // true if Shutdown called
doneChan chan struct{}
mu sync.Mutex
}
func (srv *Server) isClosed() bool {
srv.mu.Lock()
defer srv.mu.Unlock()
return srv.closed
}
// done returns a channel that's closed when the server is closed and
// all listeners and connections are closed.
func (srv *Server) done() chan struct{} {
srv.mu.Lock()
defer srv.mu.Unlock()
return srv.doneLocked()
}
func (srv *Server) doneLocked() chan struct{} {
if srv.doneChan == nil {
srv.doneChan = make(chan struct{})
}
return srv.doneChan
}
// tryCloseDone closes srv.done() if the server is closed and
// there are no active listeners or connections.
func (srv *Server) tryCloseDone() {
srv.mu.Lock()
defer srv.mu.Unlock()
srv.tryCloseDoneLocked()
}
func (srv *Server) tryCloseDoneLocked() {
if !srv.closed {
return
}
if len(srv.listeners) == 0 && len(srv.conns) == 0 {
ch := srv.doneLocked()
select {
case <-ch:
default:
close(ch)
}
}
}
// Close immediately closes all active net.Listeners and connections.
// For a graceful shutdown, use Shutdown.
func (srv *Server) Close() error {
srv.mu.Lock()
{
if srv.closed {
srv.mu.Unlock()
return nil
}
srv.closed = true
srv.tryCloseDoneLocked()
// Close all active connections and listeners.
for _, cancel := range srv.listeners {
cancel()
}
for _, cancel := range srv.conns {
cancel()
}
}
srv.mu.Unlock()
select {
case <-srv.done():
return nil
}
}
// Shutdown gracefully shuts down the server without interrupting any
// active connections. Shutdown works by first closing all open listeners
// and then waiting indefinitely for connections to close.
// If the provided context expires before the shutdown is complete,
// Shutdown returns the context's error.
//
// When Shutdown is called, Serve and ListenAndServe immediately
// return an error. Make sure the program doesn't exit and waits instead for
// Shutdown to return.
//
// Once Shutdown has been called on a server, it may not be reused;
// future calls to methods such as Serve will return an error.
func (srv *Server) Shutdown(ctx context.Context) error {
srv.mu.Lock()
{
if srv.closed {
srv.mu.Unlock()
return nil
}
srv.closed = true
srv.shutdown = true
// Close all active listeners.
for _, cancel := range srv.listeners {
cancel()
}
}
srv.mu.Unlock()
// Wait for active connections to finish.
select {
case <-ctx.Done():
return ctx.Err()
case <-srv.done():
return nil
}
}
// ListenAndServe listens for requests at the server's configured address.
// ListenAndServe listens on the TCP network address srv.Addr and then calls
// Serve to handle requests on incoming connections.
//
// If srv.Addr is blank, ":1965" is used.
//
// ListenAndServe always returns a non-nil error.
// After Shutdown or Closed, the returned error is context.Canceled.
func (srv *Server) ListenAndServe(ctx context.Context) error {
if srv.isClosed() {
return context.Canceled
}
addr := srv.Addr
if addr == "" {
addr = ":1965"
}
l, err := net.Listen("tcp", addr)
if err != nil {
return err
}
l = tls.NewListener(l, &tls.Config{
ClientAuth: tls.RequestClientCert,
MinVersion: tls.VersionTLS12,
GetCertificate: srv.getCertificate,
})
return srv.Serve(ctx, l)
}
func (srv *Server) getCertificate(h *tls.ClientHelloInfo) (*tls.Certificate, error) {
if srv.GetCertificate == nil {
return nil, errors.New("gemini: GetCertificate is nil")
}
return srv.GetCertificate(h.ServerName)
}
func (srv *Server) trackListener(l *net.Listener, cancel context.CancelFunc) bool {
srv.mu.Lock()
defer srv.mu.Unlock()
if srv.closed {
return false
}
if srv.listeners == nil {
srv.listeners = make(map[*net.Listener]context.CancelFunc)
}
srv.listeners[l] = cancel
return true
}
func (srv *Server) deleteListener(l *net.Listener) {
srv.mu.Lock()
defer srv.mu.Unlock()
delete(srv.listeners, l)
}
// Serve accepts incoming connections on the Listener l, creating a new
// service goroutine for each. The service goroutines reads the request and
// then calls the appropriate Handler to reply to them. If the provided
// context expires, Serve closes l and returns the context's error.
//
// Serve always closes l and returns a non-nil error.
// After Shutdown or Close, the returned error is context.Canceled.
func (srv *Server) Serve(ctx context.Context, l net.Listener) error {
defer l.Close()
lnctx, cancel := context.WithCancel(ctx)
defer cancel()
if !srv.trackListener(&l, cancel) {
return context.Canceled
}
defer srv.tryCloseDone()
defer srv.deleteListener(&l)
errch := make(chan error, 1)
go func() {
errch <- srv.serve(ctx, l)
}()
select {
case <-lnctx.Done():
return lnctx.Err()
case err := <-errch:
return err
}
}
func (srv *Server) serve(ctx context.Context, l net.Listener) error {
var tempDelay time.Duration // how long to sleep on accept failure
for {
rw, err := l.Accept()
if err != nil {
// If this is a temporary error, sleep
if ne, ok := err.(net.Error); ok && ne.Temporary() {
if tempDelay == 0 {
tempDelay = 5 * time.Millisecond
} else {
tempDelay *= 2
}
if max := 1 * time.Second; tempDelay > max {
tempDelay = max
}
srv.logf("gemini: Accept error: %v; retrying in %v", err, tempDelay)
time.Sleep(tempDelay)
continue
}
return err
}
tempDelay = 0
go srv.ServeConn(ctx, rw)
}
}
func (srv *Server) trackConn(conn *net.Conn, cancel context.CancelFunc) bool {
srv.mu.Lock()
defer srv.mu.Unlock()
if srv.closed && !srv.shutdown {
return false
}
if srv.conns == nil {
srv.conns = make(map[*net.Conn]context.CancelFunc)
}
srv.conns[conn] = cancel
return true
}
func (srv *Server) deleteConn(conn *net.Conn) {
srv.mu.Lock()
defer srv.mu.Unlock()
delete(srv.conns, conn)
}
// ServeConn serves a Gemini response over the provided connection.
// It closes the connection when the response has been completed.
// If the provided context expires before the response has completed,
// ServeConn closes the connection and returns the context's error.
//
// Note that ServeConn can be used during a Shutdown.
func (srv *Server) ServeConn(ctx context.Context, conn net.Conn) error {
defer conn.Close()
ctx, cancel := context.WithCancel(ctx)
defer cancel()
if !srv.trackConn(&conn, cancel) {
return context.Canceled
}
defer srv.tryCloseDone()
defer srv.deleteConn(&conn)
if d := srv.ReadTimeout; d != 0 {
conn.SetReadDeadline(time.Now().Add(d))
}
if d := srv.WriteTimeout; d != 0 {
conn.SetWriteDeadline(time.Now().Add(d))
}
errch := make(chan error, 1)
go func() {
errch <- srv.serveConn(ctx, conn)
}()
select {
case <-ctx.Done():
return ctx.Err()
case err := <-errch:
return err
}
}
func (srv *Server) serveConn(ctx context.Context, conn net.Conn) error {
w := newResponseWriter(conn)
req, err := ReadRequest(conn)
if err != nil {
w.WriteHeader(StatusBadRequest, "Bad request")
return w.Flush()
}
// Store the TLS connection state
if tlsConn, ok := conn.(*tls.Conn); ok {
state := tlsConn.ConnectionState()
req.TLS = &state
req.Host = state.ServerName
}
// Store remote address
req.RemoteAddr = conn.RemoteAddr()
h := srv.Handler
if h == nil {
w.WriteHeader(StatusNotFound, "Not found")
return w.Flush()
}
h.ServeGemini(ctx, w, req)
return w.Flush()
}
func (srv *Server) logf(format string, args ...interface{}) {
if srv.ErrorLog != nil {
srv.ErrorLog.Printf(format, args...)
} else {
log.Printf(format, args...)
}
}