pool: Cleanup client read error logging.

This switches the code that examines read errors for timeout to use the
proper interface from the net package that is designed for that purpose
instead of digging into concrete types.

It also ensures clients that timeout without ever identifying themselves
have their uniquely-assigned extra nonce used as the id instead so the
log messages can be attributed to the ip of the offending clients.

Finally, it no longer logs an error when an io.EOF is encountered as
that is an expected condition when the client disconnects and is not an
actual error.

pool/client.go

@@ -183,6 +183,11 @@ func (c *Client) shutdown() {
 	id := c.id
 	c.mtx.RUnlock()
 
+	// Connections that never identify will not have an ID set, so use their
+	// uniquely-assigned extranonce in that case.
+	if id == "" {
+		id = c.extraNonce1
+	}
 	log.Tracef("%s connection terminated.", id)
 }
 
@@ -708,27 +713,21 @@ func (c *Client) read() {
 		data, err := c.reader.ReadBytes('\n')
 		if err != nil {
 			if errors.Is(err, io.EOF) {
-				log.Errorf("%s: EOF", id)
-				c.cancel()
-				return
-			}
-			var nErr *net.OpError
-			if !errors.As(err, &nErr) {
-				log.Errorf("%s: unable to read bytes: %v", id, err)
 				c.cancel()
 				return
 			}
-			if nErr.Op == "read" && nErr.Net == "tcp" {
-				switch {
-				case nErr.Timeout():
-					log.Errorf("%s: read timeout: %v", id, err)
-				case !nErr.Timeout():
-					log.Errorf("%s: read error: %v", id, err)
+			var nErr net.Error
+			if errors.As(err, &nErr) && nErr.Timeout() {
+				// Connections that never identify will not have an ID set, so
+				// use their uniquely-assigned extranonce in that case.
+				if id == "" {
+					id = c.extraNonce1
 				}
+				log.Errorf("%s: read timeout: %v", id, err)
 				c.cancel()
 				return
 			}
-			log.Errorf("unable to read bytes: %v %T", err, err)
+			log.Errorf("%s: unable to read bytes: %v (%[2]T)", id, err)
 			c.cancel()
 			return
 		}