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client.go
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client.go
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// Simple Syslog Server that
// supports UDP, TCP and TLS.
//
// Marcel Gebhardt
// April 2018
package syslog
import (
"crypto/tls"
"errors"
"fmt"
"net"
"os"
"time"
"runtime"
)
// ConnectionType defines wheather to connect via UDP or TCP (or TLS)
type ConnectionType string
const (
// ConnectionUDP connects via UDP
ConnectionUDP ConnectionType = "udp"
// ConnectionTCP connects via TCP
ConnectionTCP ConnectionType = "tcp"
// ConnectionTLS connects via TLS
ConnectionTLS ConnectionType = "tls"
)
const (
// DefaultHostname will be used if hostname could not be determined
DefaultHostname string = "unknown"
// DefaultIP will be used if ip could not be determined
DefaultIP string = ""
)
// Client holds a connection to a specified address
type Client struct {
Hostname string // Hostname of the system
IP string // IP of the system
Rfc3164 bool // rfc standard for length reduction
Rfc5424 bool // rfc standard for length reduction
Rfc3339 bool // use rfc3339 instead of stamp for time format
MaxLength int // max syslog length
NoPrio bool // do not add <prio> Prefix
HostnameOnly bool // Only use hostname in syslog header instead of hostname ip combination
conn net.Conn // connection to the syslog server
bytesSent int64
maxBytes int64
}
// NewClient initializes a new server connection.
// Examples:
// - NewClient(ConnectionUDP, "172.0.0.1:514")
// - NewClient(ConnectionTCP, ":514")
// - NewClient(ConnectionTLS, "172.0.0.1:514")
func NewClient(connectionType ConnectionType, address string, tlsconfig *tls.Config) (*Client, error) {
// Validate data
if connectionType != ConnectionUDP && connectionType != ConnectionTCP && connectionType != ConnectionTLS {
return nil, fmt.Errorf("unknown connection type '%s'", connectionType)
}
var (
conn net.Conn
err error
)
// connect via udp / tcp / tls
if connectionType == ConnectionTLS {
conn, err = tls.Dial(string(ConnectionTCP), address, tlsconfig)
} else {
conn, err = net.Dial(string(connectionType), address)
}
if err != nil {
return nil, err
}
// get hostname and ip of system
hostname, err := os.Hostname()
if err != nil {
hostname = DefaultHostname
}
ip, _, err := net.SplitHostPort(conn.LocalAddr().String())
if err != nil {
ip = DefaultIP
}
// return the server
return &Client{
Hostname: hostname,
IP: ip,
conn: conn,
}, nil
}
// TooManyBytesSentErr will be returned, if a message could not be sent
// because of a hard limit of bytes to be send.
var TooManyBytesSentErr = errors.New("too many bytes sent")
// Send sends a syslog message with a specified priority.
// Examples:
// - Send("foo", LOG_LOCAL0|LOG_NOTICE)
// - Send("bar", LOG_DAEMON|LOG_DEBUG)
func (client *Client) Send(message string, priority Priority) error {
if client.maxBytes != 0 && client.bytesSent > client.maxBytes {
return TooManyBytesSentErr
}
var timestamp string
var tm time.Time
if runtime.GOOS != "windows" {
var cstSh, _ = time.LoadLocation("Asia/Shanghai") //上海
tm = time.Now().In(cstSh)
} else { // Unix-like
var cstSh = time.FixedZone("CST", 8*3600) // 东八
tm = time.Now().In(cstSh)
}
if client.Rfc3339 {
timestamp = tm.Format(time.RFC3339)
} else {
timestamp = tm.Format(time.Stamp)
}
var hostnameCombi = client.Hostname
if !client.HostnameOnly {
hostnameCombi = fmt.Sprintf("%s/%s", client.Hostname, client.IP)
}
var header string
if client.NoPrio {
header = fmt.Sprintf("%s %s", timestamp, hostnameCombi)
} else {
header = fmt.Sprintf("<%d>%s %s", int(priority), timestamp, hostnameCombi)
}
// RFC length reduction
length := len(message)
if client.Rfc3164 && length > 1024 {
message = fmt.Sprintf("%s...", message[:1021])
} else if client.Rfc5424 && length > 2048 {
message = fmt.Sprintf("%s...", message[:2045])
} else if client.MaxLength > 3 && length > client.MaxLength {
message = fmt.Sprintf("%s...", message[:client.MaxLength-3])
}
// Send message
n, err := fmt.Fprintf(client.conn, "%s %s", header, message)
client.bytesSent += int64(n)
return err
}
// SendRaw sends a syslog message without adding syslog header.
// Examples:
// - SendRaw("foo")
// - SendRaw("bar")
func (client *Client) SendRaw(message string) error {
if client.maxBytes != 0 && client.bytesSent > client.maxBytes {
return TooManyBytesSentErr
}
// RFC length reduction
length := len(message)
if client.Rfc3164 && length > 1024 {
message = fmt.Sprintf("%s...", message[:1021])
} else if client.Rfc5424 && length > 2048 {
message = fmt.Sprintf("%s...", message[:2045])
} else if client.MaxLength > 3 && length > client.MaxLength {
message = fmt.Sprintf("%s...", message[:client.MaxLength-3])
}
// Send message
n, err := fmt.Fprint(client.conn, message)
client.bytesSent += int64(n)
return err
}
// Close closes the server connection gracefully.
func (client *Client) Close() error {
return client.conn.Close()
}
// SetMaxBytes sets the maximum bytes that will be sent to rsyslog (approximately)
func (client *Client) SetMaxBytes(i int64) {
client.maxBytes = i
}