Add connection attributes

README.md

@@ -393,6 +393,15 @@ Default:        0
 
 I/O write timeout. The value must be a decimal number with a unit suffix (*"ms"*, *"s"*, *"m"*, *"h"*), such as *"30s"*, *"0.5m"* or *"1m30s"*.
 
+##### `connectionAttributes`
+
+```
+Type:           comma-delimited string of user-defined "key:value" pairs
+Valid Values:   (<name1>:<value1>,<name2>:<value2>,...)
+Default:        none
+```
+
+[Connection attributes](https://dev.mysql.com/doc/refman/8.0/en/performance-schema-connection-attribute-tables.html) are key-value pairs that application programs can pass to the server at connect time.
 
 ##### System Variables
 

const.go

@@ -8,12 +8,23 @@
 
 package mysql
 
+import "runtime"
+
 const (
 	defaultAuthPlugin       = "mysql_native_password"
 	defaultMaxAllowedPacket = 4 << 20 // 4 MiB
 	minProtocolVersion      = 10
 	maxPacketSize           = 1<<24 - 1
 	timeFormat              = "2006-01-02 15:04:05.999999"
+
+	// Connection attributes
+	// See https://dev.mysql.com/doc/refman/8.0/en/performance-schema-connection-attribute-tables.html#performance-schema-connection-attributes-available
+	connAttrClientName      = "_client_name"
+	connAttrClientNameValue = "GO-MySQL-Driver"
+	connAttrOS              = "_os"
+	connAttrOSValue         = runtime.GOOS
+	connAttrPlatform        = "_platform"
+	connAttrPlatformValue   = runtime.GOARCH
 )
 
 // MySQL constants documentation:

driver_test.go

@@ -3209,3 +3209,58 @@ func TestConnectorTimeoutsWatchCancel(t *testing.T) {
 		t.Errorf("connection not closed")
 	}
 }
+
+func TestConnectionAttributes(t *testing.T) {
+	if !available {
+		t.Skipf("MySQL server not running on %s", netAddr)
+	}
+
+	attr1 := "attr1"
+	value1 := "value1"
+	attr2 := "foo"
+	value2 := "boo"
+	dsn += fmt.Sprintf("&connectionAttributes=%s:%s,%s:%s", attr1, value1, attr2, value2)
+
+	var db *sql.DB
+	if _, err := ParseDSN(dsn); err != errInvalidDSNUnsafeCollation {
+		db, err = sql.Open("mysql", dsn)
+		if err != nil {
+			t.Fatalf("error connecting: %s", err.Error())
+		}
+		defer db.Close()
+	}
+
+	dbt := &DBTest{t, db}
+
+	var version string
+	if err := dbt.db.QueryRow("SELECT @@version").Scan(&version); err != nil {
+		dbt.Fatalf("%s", err.Error())
+	}
+	if strings.Contains(strings.ToLower(version), "mariadb") {
+		t.Skip(`TODO: Support adding connection attributes in MariaDB`)
+	}
+
+	var attrValue string
+	queryString := "SELECT ATTR_VALUE FROM performance_schema.session_account_connect_attrs WHERE PROCESSLIST_ID = CONNECTION_ID() and ATTR_NAME = ?"
+	rows := dbt.mustQuery(queryString, connAttrClientName)
+	if rows.Next() {
+		rows.Scan(&attrValue)
+		if attrValue != connAttrClientNameValue {
+			dbt.Errorf("expected %q, got %q", connAttrClientNameValue, attrValue)
+		}
+	} else {
+		dbt.Errorf("no data")
+	}
+	rows.Close()
+
+	rows = dbt.mustQuery(queryString, attr2)
+	if rows.Next() {
+		rows.Scan(&attrValue)
+		if attrValue != value2 {
+			dbt.Errorf("expected %q, got %q", value2, attrValue)
+		}
+	} else {
+		dbt.Errorf("no data")
+	}
+	rows.Close()
+}

dsn.go

@@ -34,22 +34,23 @@ var (
 // If a new Config is created instead of being parsed from a DSN string,
 // the NewConfig function should be used, which sets default values.
 type Config struct {
-	User             string            // Username
-	Passwd           string            // Password (requires User)
-	Net              string            // Network type
-	Addr             string            // Network address (requires Net)
-	DBName           string            // Database name
-	Params           map[string]string // Connection parameters
-	Collation        string            // Connection collation
-	Loc              *time.Location    // Location for time.Time values
-	MaxAllowedPacket int               // Max packet size allowed
-	ServerPubKey     string            // Server public key name
-	pubKey           *rsa.PublicKey    // Server public key
-	TLSConfig        string            // TLS configuration name
-	TLS              *tls.Config       // TLS configuration, its priority is higher than TLSConfig
-	Timeout          time.Duration     // Dial timeout
-	ReadTimeout      time.Duration     // I/O read timeout
-	WriteTimeout     time.Duration     // I/O write timeout
+	User                 string            // Username
+	Passwd               string            // Password (requires User)
+	Net                  string            // Network type
+	Addr                 string            // Network address (requires Net)
+	DBName               string            // Database name
+	Params               map[string]string // Connection parameters
+	Collation            string            // Connection collation
+	Loc                  *time.Location    // Location for time.Time values
+	MaxAllowedPacket     int               // Max packet size allowed
+	ServerPubKey         string            // Server public key name
+	pubKey               *rsa.PublicKey    // Server public key
+	TLSConfig            string            // TLS configuration name
+	TLS                  *tls.Config       // TLS configuration, its priority is higher than TLSConfig
+	Timeout              time.Duration     // Dial timeout
+	ReadTimeout          time.Duration     // I/O read timeout
+	WriteTimeout         time.Duration     // I/O write timeout
+	ConnectionAttributes string            // Connection Attributes, comma-delimited string of user-defined "key:value" pairs
 
 	AllowAllFiles            bool // Allow all files to be used with LOAD DATA LOCAL INFILE
 	AllowCleartextPasswords  bool // Allows the cleartext client side plugin
@@ -554,6 +555,11 @@ func parseDSNParams(cfg *Config, params string) (err error) {
 			if err != nil {
 				return
 			}
+
+		// Connection attributes
+		case "connectionAttributes":
+			cfg.ConnectionAttributes = value
+
 		default:
 			// lazy init
 			if cfg.Params == nil {

packets.go

@@ -18,6 +18,7 @@ import (
 	"fmt"
 	"io"
 	"math"
+	"strings"
 	"time"
 )
 
@@ -285,6 +286,7 @@ func (mc *mysqlConn) writeHandshakeResponsePacket(authResp []byte, plugin string
 		clientLocalFiles |
 		clientPluginAuth |
 		clientMultiResults |
+		clientConnectAttrs |
 		mc.flags&clientLongFlag
 
 	if mc.cfg.ClientFoundRows {
@@ -318,6 +320,30 @@ func (mc *mysqlConn) writeHandshakeResponsePacket(authResp []byte, plugin string
 		pktLen += n + 1
 	}
 
+	connAttrsBuf := make([]byte, 0, 100)
+
+	// default connection attributes
+	connAttrsBuf = appendLengthEncodedString(connAttrsBuf, connAttrClientName)
+	connAttrsBuf = appendLengthEncodedString(connAttrsBuf, connAttrClientNameValue)
+	connAttrsBuf = appendLengthEncodedString(connAttrsBuf, connAttrOS)
+	connAttrsBuf = appendLengthEncodedString(connAttrsBuf, connAttrOSValue)
+	connAttrsBuf = appendLengthEncodedString(connAttrsBuf, connAttrPlatform)
+	connAttrsBuf = appendLengthEncodedString(connAttrsBuf, connAttrPlatformValue)
+
+	// user-defined connection attributes
+	for _, connAttr := range strings.Split(mc.cfg.ConnectionAttributes, ",") {
+		attr := strings.Split(connAttr, ":")
+		if len(attr) != 2 {
+			continue
+		}
+		for _, v := range attr {
+			connAttrsBuf = appendLengthEncodedString(connAttrsBuf, v)
+		}
+	}
+
+	// 1 byte to store length of all key-values
+	pktLen += len(connAttrsBuf) + 1
+
 	// Calculate packet length and get buffer with that size
 	data, err := mc.buf.takeSmallBuffer(pktLen + 4)
 	if err != nil {
@@ -394,6 +420,11 @@ func (mc *mysqlConn) writeHandshakeResponsePacket(authResp []byte, plugin string
 	data[pos] = 0x00
 	pos++
 
+	// Connection Attributes
+	data[pos] = byte(len(connAttrsBuf))
+	pos++
+	pos += copy(data[pos:], connAttrsBuf)
+
 	// Send Auth packet
 	return mc.writePacket(data[:pos])
 }

utils.go

@@ -616,6 +616,11 @@ func appendLengthEncodedInteger(b []byte, n uint64) []byte {
 		byte(n>>32), byte(n>>40), byte(n>>48), byte(n>>56))
 }
 
+func appendLengthEncodedString(b []byte, s string) []byte {
+	b = appendLengthEncodedInteger(b, uint64(len(s)))
+	return append(b, s...)
+}
+
 // reserveBuffer checks cap(buf) and expand buffer to len(buf) + appendSize.
 // If cap(buf) is not enough, reallocate new buffer.
 func reserveBuffer(buf []byte, appendSize int) []byte {