Setting idletimeout in Go - go

Question

I have a function in go which is handling connections which are coming through tcp and handled via ssh. I am trying to set an idle timeout by creating struct in the connection function.
Use case - a customer should be able to make a connection and upload/download multiple files
Reference - IdleTimeout in tcp server
Function code:
type Conn struct {
net.Conn
idleTimeout time.Duration
}
func HandleConn(conn net.Conn) {
var err error
rAddr := conn.RemoteAddr()
session := shortuuid.New()
config := LoadSSHServerConfig(session)
blocklistItem := blocklist.GetBlockListItem(rAddr)
if blocklistItem.IsBlocked() {
conn.Close()
atomic.AddInt64(&stats.Stats.BlockedConnections, 1)
return
}
func (c *Conn) Read(b []byte) (int, error) {
err := c.Conn.SetReadDeadline(time.Now().Add(c.idleTimeout))
if err != nil {
return 0, err
}
return c.Conn.Read(b)
}
sConn, chans, reqs, err := ssh.NewServerConn(conn, config)
if err != nil {
if err == io.EOF {
log.Errorw("SSH: Handshaking was terminated", log.Fields{
"address": rAddr,
"error": err,
"session": session})
} else {
log.Errorw("SSH: Error on handshaking", log.Fields{
"address": rAddr,
"error": err,
"session": session})
}
atomic.AddInt64(&stats.Stats.AuthorizationFailed, 1)
return
}
log.Infow("connection accepted", log.Fields{
"user": sConn.User(),
})
if user, ok := users[session]; ok {
log.Infow("SSH: Connection accepted", log.Fields{
"user": user.LogFields(),
"clientVersion": string(sConn.ClientVersion())})
atomic.AddInt64(&stats.Stats.AuthorizationSucceeded, 1)
// The incoming Request channel must be serviced.
go ssh.DiscardRequests(reqs)
// Key ID: sConn.Permissions.Extensions["key-id"]
handleServerConn(user, chans)
log.Infow("connection finished", log.Fields{"user": user.LogFields()})
log.Infow("checking connections", log.Fields{
//"cc": Stats.AcceptedConnections,
"cc2": &stats.Stats.AcceptedConnections})
// Remove connection from local cache
delete(users, session)
} else {
log.Infow("user not found from memory", log.Fields{"username": sConn.User()})
}
}
This code is coming from the Listen function:
func Listen() {
listener, err := net.Listen("tcp", sshListen)
if err != nil {
panic(err)
}
if useProxyProtocol {
listener = &proxyproto.Listener{
Listener: listener,
ProxyHeaderTimeout: time.Second * 10,
}
}
for {
// Once a ServerConfig has been configured, connections can be accepted.
conn, err := listener.Accept()
if err != nil {
log.Errorw("SSH: Error accepting incoming connection", log.Fields{"error": err})
atomic.AddInt64(&stats.Stats.FailedConnections, 1)
continue
}
// Before use, a handshake must be performed on the incoming net.Conn.
// It must be handled in a separate goroutine,
// otherwise one user could easily block entire loop.
// For example, user could be asked to trust server key fingerprint and hangs.
go HandleConn(conn)
}
}
Is that even possible to set a deadline for only the connections which have been idle for 20 secinds (no upload/downloads).
EDIT 1 : Following #LiamKelly's suggestions, I have made the changes in the code. Now the code is like
type SshProxyConn struct {
net.Conn
idleTimeout time.Duration
}
func (c *SshProxyConn) Read(b []byte) (int, error) {
err := c.Conn.SetReadDeadline(time.Now().Add(c.idleTimeout))
if err != nil {
return 0, err
}
return c.Conn.Read(b)
}
func HandleConn(conn net.Conn) {
//lines of code as above
sshproxyconn := &SshProxyConn{nil, time.Second * 20}
Conn, chans, reqs, err := ssh.NewServerConn(sshproxyconn, config)
//lines of code
}
But now the issue is that SSH is not happening. I am getting the error "Connection closed" when I try to do ssh. Is it still waiting for "conn" variable in the function call?

Answer 1

Is that even possible to set a deadline for only the connections which have been idle for 20 [seconds]
Ok so first a general disclaimer, I am going to assume go-protoproxy implements the Conn interface as we would expected. Also as you hinted at before, I don't think you can put a a struct method inside another function (I also recommend renaming it something unique to prevent Conn vs net.Conn confusion).
type SshProxyConn struct {
net.Conn
idleTimeout time.Duration
}
func (c *SshProxyConn) Read(b []byte) (int, error) {
err := c.Conn.SetReadDeadline(time.Now().Add(c.idleTimeout))
if err != nil {
return 0, err
}
return c.Conn.Read(b)
}
func HandleConn(conn net.Conn) {
This makes is more clear what your primary issue is, which you passed the normal net.Conn to your SSH server, not your wrapper class. So
sConn, chans, reqs, err := ssh.NewServerConn(conn, config)
should be EDIT
sshproxyconn := &SshProxyConn{conn, time.Second * 20}
Conn, chans, reqs, err := ssh.NewServerConn(sshproxyconn , config)