log

README

log

log enables query logging.

Syntax

log

• With no arguments, a query log entry is written to query.log in the common log format for all requests

log FILE

• FILE is the log file to create (or append to).

log [NAME] FILE [FORMAT]

• NAME is the name to match in order to be logged
• FILE is the log file to create (or append to)
• FORMAT is the log format to use (default is Common Log Format)

You can further specify the class of responses that get logged:

log [NAME] FILE [FORMAT] {
    class [success|denial|error|all]
}

Here success denial and error denotes the class of responses that should be logged. The classes have the following meaning:

• success: successful response
• denial: either NXDOMAIN or NODATA (name exists, type does not)
• error: SERVFAIL, NOTIMP, REFUSED, etc. Any that indicated the remove server is not willing to resolve the request.
• all: the default is nothing is specified.

If no class is specified it defaults to all.

Log File

The log file can be any filename. It could also be stdout or stderr to write the log to the console, or syslog to write to the system log (except on Windows). If the log file does not exist beforehand, CoreDNS will create it before appending to it.

Log Format

You can specify a custom log format with any placeholder values. Log supports both request and response placeholders.

The following place holders are supported:

• {type}: qtype of the request.
• {name}: qname of the request.
• {class}: qclass of the request.
• {proto}: protocol used (tcp or udp).
• {when}: time of the query.
• {remote}: client's IP address.
• {port}: client's port.
• {rcode}: response RCODE.
• {size}: response size.
• {duration}: response duration.
• {>bufsize}: the EDNS0 buffer size advertized by the client.
• {>do}: is the EDNS0 DO (DNSSEC OK) bit set.
• {>id}: query ID
• {>opcode}: query OPCODE

The default Common Log Format is:

`{remote} - [{when}] "{type} {class} {name} {proto} {>do} {>bufsize}" {rcode} {size} {duration}`

Examples

Log all requests to a file:

log /var/log/query.log

Custom log format:

log . ../query.log "{proto} Request: {name} {type} {>id}"

Only log denials for example.org (and below to a file)

log example.org example-query-log {
    class denial
}

Documentation

Overview

Package log implements basic but useful request (access) logging middleware.

Index

• Constants
• type Logger
  • func (l Logger) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error)
• type Rule

Constants

const (
	// DefaultLogFilename is the default log filename.
	DefaultLogFilename = "query.log"
	// CommonLogFormat is the common log format.
	CommonLogFormat = `{remote} ` + CommonLogEmptyValue + ` [{when}] "{type} {class} {name} {proto} {>do} {>bufsize}" {rcode} {size} {duration}`
	// CommonLogEmptyValue is the common empty log value.
	CommonLogEmptyValue = "-"
	// CombinedLogFormat is the combined log format.
	CombinedLogFormat = CommonLogFormat + ` "{>opcode}"`
	// DefaultLogFormat is the default log format.
	DefaultLogFormat = CommonLogFormat
)

Types

type Logger

type Logger struct {
	Next      middleware.Handler
	Rules     []Rule
	ErrorFunc func(dns.ResponseWriter, *dns.Msg, int) // failover error handler
}

Logger is a basic request logging middleware.

func (Logger) ServeDNS

func (l Logger) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error)

ServeDNS implements the middleware.Handler interface.

type Rule

type Rule struct {
	NameScope  string
	Class      response.Class
	OutputFile string
	Format     string
	Log        *log.Logger
}

Rule configures the logging middleware.