Add support for connection attributes.

This sets attribute _client_name with the value "Go MySQL Driver"
Also sets _os, _platform, _pid and program_name by default.

Author: dveeden

AUTHORS

@@ -15,6 +15,7 @@ Aaron Hopkins <go-sql-driver at die.net>
 Arne Hormann <arnehormann at gmail.com>
 Carlos Nieto <jose.carlos at menteslibres.net>
 Chris Moos <chris at tech9computers.com>
+Daniël van Eeden <daniel.van.eeden at myname.nl>
 DisposaBoy <disposaboy at dby.me>
 Frederick Mayle <frederickmayle at gmail.com>
 Gustavo Kristic <gkristic at gmail.com>

driver.go

@@ -20,6 +20,8 @@ import (
 	"database/sql"
 	"database/sql/driver"
 	"net"
+        "os"
+        "strconv"
 )
 
 // This struct is exported to make the driver directly accessible.
@@ -30,6 +32,8 @@ type MySQLDriver struct{}
 // Custom dial functions must be registered with RegisterDial
 type DialFunc func(addr string) (net.Conn, error)
 
+var pid string
+
 var dials map[string]DialFunc
 
 // RegisterDial registers a custom dial function. It can then be used by the
@@ -145,5 +149,6 @@ func (d MySQLDriver) Open(dsn string) (driver.Conn, error) {
 }
 
 func init() {
+	pid = strconv.Itoa(os.Getpid())
 	sql.Register("mysql", &MySQLDriver{})
 }

packets.go

@@ -16,6 +16,9 @@ import (
 	"fmt"
 	"io"
 	"math"
+        "os"
+	"path"
+	"runtime"
 	"time"
 )
 
@@ -219,6 +222,7 @@ func (mc *mysqlConn) writeAuthPacket(cipher []byte) error {
 		clientTransactions |
 		clientLocalFiles |
 		clientPluginAuth |
+		clientConnectAttrs |
 		mc.flags&clientLongFlag
 
 	if mc.cfg.clientFoundRows {
@@ -233,7 +237,23 @@ func (mc *mysqlConn) writeAuthPacket(cipher []byte) error {
 	// User Password
 	scrambleBuff := scramblePassword(cipher, []byte(mc.cfg.passwd))
 
+	attrs := map[string]string {
+	    "_os":          runtime.GOOS,
+	    "_client_name": "Go-MySQL-Driver",
+	    "_pid":         pid,
+	    "_platform":    runtime.GOARCH,
+	    "program_name": path.Base(os.Args[0]),
+        }
+
+	attrlen := 0
+	for attrname, attrvalue := range attrs {
+		attrlen += len(attrname) + len(attrvalue)
+		// one byte to store attrname length and one byte to store attrvalue length
+		attrlen += 2
+	}
+
 	pktLen := 4 + 4 + 1 + 23 + len(mc.cfg.user) + 1 + 1 + len(scrambleBuff) + 21 + 1
+	pktLen += attrlen + 1 // one byte to store the total length of attrs
 
 	// To specify a db name
 	if n := len(mc.cfg.dbname); n > 0 {
@@ -305,6 +325,19 @@ func (mc *mysqlConn) writeAuthPacket(cipher []byte) error {
 	// Assume native client during response
 	pos += copy(data[pos:], "mysql_native_password")
 	data[pos] = 0x00
+        pos++
+
+	// Connection attributes
+	data[pos] = byte(attrlen)
+	pos++
+
+	for attrname, attrvalue := range attrs {
+		data[pos] = byte(len(attrname))
+		pos += 1 + copy(data[pos+1:], attrname)
+
+		data[pos] = byte(len(attrvalue))
+		pos += 1 + copy(data[pos+1:], attrvalue)
+	}
 
 	// Send Auth packet
 	return mc.writePacket(data)