From 8aa88a0bd318da123f540128281b468ac26ebecf Mon Sep 17 00:00:00 2001
From: Miek Gieben <miek@miek.nl>
Date: Fri, 25 Mar 2011 11:19:35 +0100
Subject: [PATCH] normalize errors

---
 dns.go      | 30 +++++++++++++++---------------
 edns.go     |  2 +-
 keygen.go   | 14 +++++++-------
 msg.go      | 15 +++++++++++++++
 resolver.go | 10 +---------
 tsig.go     | 12 ++++++------
 types.go    |  4 ++--
 xfr.go      | 12 ++++++------
 8 files changed, 53 insertions(+), 46 deletions(-)

diff --git a/dns.go b/dns.go
index a32e8c41..c09d3ee6 100644
--- a/dns.go
+++ b/dns.go
@@ -4,7 +4,7 @@
 // Extended and bugfixes by Miek Gieben
 
 // Package dns implements a full featured interface to the DNS.
-// The package allows full control over what is send out to the DNS. 
+// The package allows complete control over what is send out to the DNS. 
 //
 // Resource records are native types. They are not stored in wire format.
 // Basic usage pattern for creating a new resource record:
@@ -16,7 +16,8 @@
 // The package dns supports querying, incoming/outgoing Axfr/Ixfr, TSIG, EDNS0,
 // dynamic updates, notifies and DNSSEC validation/signing.
 //
-// Basic use pattern for creating a resolver:
+// Querying the DNS is done by using a Resolver structure. Basic use pattern for creating 
+// a resolver:
 //
 //      res := new(Resolver)
 //      res.Servers = []string{"127.0.0.1"} 
@@ -26,7 +27,7 @@
 //      m.Question[0] = Question{"miek.nl", TypeSOA, ClassINET}
 //      in, err := res.Query(m)
 //
-// 
+// Server side programming is also supported.
 // Basic use pattern for creating an UDP DNS server:
 //
 //      func handle(d *dns.Conn, i *dns.Msg) { /* handle request */ }
@@ -40,9 +41,8 @@
 //
 package dns
 
-// ErrShortWrite is defined in io, use that!
-
 import (
+        "io"
 	"os"
 	"net"
 	"strconv"
@@ -123,7 +123,7 @@ func (d *Conn) ReadMsg(m *Msg) os.Error {
 	in = in[:n]
 	ok := m.Unpack(in)
 	if !ok {
-		return &Error{Error: "Failed to unpack"}
+                return ErrUnpack
 	}
 	return nil
 }
@@ -133,7 +133,7 @@ func (d *Conn) ReadMsg(m *Msg) os.Error {
 func (d *Conn) WriteMsg(m *Msg) os.Error {
 	out, ok := m.Pack()
 	if !ok {
-		return &Error{Error: "Failed to pack"}
+		return ErrPack
 	}
 	_, err := d.Write(out)
 	if err != nil {
@@ -147,7 +147,7 @@ func (d *Conn) WriteMsg(m *Msg) os.Error {
 // reading that error is returned; otherwise err is nil.
 func (d *Conn) Read(p []byte) (n int, err os.Error) {
 	if d.UDP != nil && d.TCP != nil {
-		return 0, &Error{Error: "UDP and TCP or both non-nil"}
+		return 0, ErrConn
 	}
 	switch {
 	case d.UDP != nil:
@@ -160,7 +160,7 @@ func (d *Conn) Read(p []byte) (n int, err os.Error) {
 		d.Port = addr.(*net.UDPAddr).Port
 	case d.TCP != nil:
 		if len(p) < 1 {
-			return 0, &Error{Error: "Buffer too small to read"}
+			return 0, io.ErrShortBuffer
 		}
 		n, err = d.TCP.Read(p[0:2])
 		if err != nil || n != 2 {
@@ -170,10 +170,10 @@ func (d *Conn) Read(p []byte) (n int, err os.Error) {
 		d.Port = d.TCP.RemoteAddr().(*net.TCPAddr).Port
 		l, _ := unpackUint16(p[0:2], 0)
 		if l == 0 {
-			return 0, &Error{Error: "received nil msg length", Server: d.Addr}
+			return 0, ErrShortRead
 		}
 		if int(l) > len(p) {
-			return int(l), &Error{Error: "Buffer too small to read"}
+			return int(l), io.ErrShortBuffer
 		}
 		n, err = d.TCP.Read(p[:l])
 		if err != nil {
@@ -204,7 +204,7 @@ func (d *Conn) Read(p []byte) (n int, err os.Error) {
 // that error is returned; otherwise err is nil
 func (d *Conn) Write(p []byte) (n int, err os.Error) {
 	if d.UDP != nil && d.TCP != nil {
-		return 0, &Error{Error: "UDP and TCP or both non-nil"}
+		return 0, ErrConn
 	}
 
 	var attempts int
@@ -248,7 +248,7 @@ func (d *Conn) Write(p []byte) (n int, err os.Error) {
 				return n, err
 			}
 			if n != 2 {
-				return n, &Error{Error: "Write failure"}
+				return n, io.ErrShortWrite
 			}
 			n, err = d.TCP.Write(q)
 			if err != nil {
@@ -279,7 +279,7 @@ func (d *Conn) Write(p []byte) (n int, err os.Error) {
 // errors are returned in err; otherwise it is nil.
 func (d *Conn) Close() (err os.Error) {
 	if d.UDP != nil && d.TCP != nil {
-		return &Error{Error: "UDP and TCP or both non-nil"}
+		return ErrConn
 	}
 	switch {
 	case d.UDP != nil:
@@ -295,7 +295,7 @@ func (d *Conn) Close() (err os.Error) {
 func (d *Conn) SetTimeout() (err os.Error) {
 	var sec int64
 	if d.UDP != nil && d.TCP != nil {
-		return &Error{Error: "UDP and TCP or both non-nil"}
+		return ErrConn
 	}
 	sec = int64(d.Timeout)
 	if sec == 0 {
diff --git a/edns.go b/edns.go
index fd62021f..b56bd351 100644
--- a/edns.go
+++ b/edns.go
@@ -5,7 +5,7 @@ import (
 	"encoding/hex"
 )
 
-// EDNS0 Options
+// EDNS0 Option codes.
 const (
 	_              = iota
 	OptionCodeLLQ           // not used
diff --git a/keygen.go b/keygen.go
index ef1486a0..4afbe443 100644
--- a/keygen.go
+++ b/keygen.go
@@ -23,14 +23,14 @@ func (r *RR_DNSKEY) Generate(bits int) (PrivateKey, os.Error) {
 	switch r.Algorithm {
 	case AlgRSAMD5, AlgRSASHA1, AlgRSASHA256:
 		if bits < 512 || bits > 4096 {
-			return nil, &Error{Error: "Size not in range [512..4096]"}
+			return nil, ErrKeySize
 		}
 	case AlgRSASHA512:
 		if bits < 1024 || bits > 4096 {
-			return nil, &Error{Error: "Size not in range [1024..4096]"}
+			return nil, ErrKeySize
 		}
 	default:
-		return nil, &Error{Error: "Algorithm not recognized"}
+		return nil, ErrAlg
 	}
 
 	switch r.Algorithm {
@@ -100,12 +100,12 @@ func (k *RR_DNSKEY) ReadPrivateKey(q io.Reader) (PrivateKey, os.Error) {
 			switch left {
 			case "Private-key-format:":
 				if right != "v1.3" {
-					return nil, &Error{Error: "v1.3 supported"}
+					return nil, ErrPrivKey
 				}
 			case "Algorithm:":
 				a, _ := strconv.Atoi(right)
 				if a == 0 {
-					return nil, &Error{Error: "incorrect algorithm"}
+					return nil, ErrAlg
 				}
 				k.Algorithm = uint8(a)
 			case "Modulus:", "PublicExponent:", "PrivateExponent:", "Prime1:", "Prime2:":
@@ -140,13 +140,13 @@ func (k *RR_DNSKEY) ReadPrivateKey(q io.Reader) (PrivateKey, os.Error) {
 			case "Created:", "Publish:", "Activate:":
 				/* not used in Go (yet) */
 			default:
-				return nil, &Error{Error: "Private key file not recognized"}
+				return nil, ErrKey
 			}
 		}
 		line, _, err = r.ReadLine()
 	}
 	if ! k.setPublicKeyRSA(p.PublicKey.E, p.PublicKey.N) {
-                return nil, &Error{Error: "Failed to set public key"}
+                return nil, ErrKey
         }
 	return p, nil
 }
diff --git a/msg.go b/msg.go
index 0f589306..13e94393 100644
--- a/msg.go
+++ b/msg.go
@@ -27,6 +27,21 @@ import (
 	"encoding/hex"
 )
 
+var ErrUnpack os.Error = &Error{Error: "unpacking failed"}
+var ErrPack os.Error = &Error{Error: "packing failed"}
+var ErrId os.Error = &Error{Error: "id mismatch"}
+var ErrShortRead os.Error = &Error{Error: "short read"}
+var ErrConn os.Error = &Error{Error: "conn holds both UDP and TCP connection"}
+var ErrServ os.Error = &Error{Error: "no servers could be reached"}
+var ErrKey os.Error = &Error{Error: "bad key"}
+var ErrPrivKey os.Error = &Error{Error: "bad private key"}
+var ErrKeySize os.Error = &Error{Error: "bad key size"}
+var ErrAlg os.Error = &Error{Error: "bad algorithm"}
+var ErrTime os.Error = &Error{Error: "bad time"}
+var ErrSig os.Error = &Error{Error: "bad signature"}
+var ErrSigGen os.Error = &Error{Error: "bad signature generation"}
+var ErrXfrSoa os.Error = &Error{Error: "no SOA seen"}
+
 // A manually-unpacked version of (id, bits).
 // This is in its own struct for easy printing.
 type MsgHdr struct {
diff --git a/resolver.go b/resolver.go
index 830f5e40..b7c0ea42 100644
--- a/resolver.go
+++ b/resolver.go
@@ -12,14 +12,6 @@ import (
 	"time"
 )
 
-// Todo(MG) put in dns.go
-const ErrPack = "Failed to pack message"
-const ErrUnpack = ""
-const ErrServ = "No servers could be reached"
-const ErrTsigKey = ""
-const ErrTsigTime = ""
-const ErrTsig = ""
-
 type Resolver struct {
 	Servers  []string            // servers to use
 	Search   []string            // suffixes to append to local name
@@ -50,7 +42,7 @@ func (res *Resolver) QueryTsig(q *Msg, tsig *Tsig) (d *Msg, err os.Error) {
 
 	sending, ok := q.Pack()
 	if !ok {
-		return nil, &Error{Error: ErrPack}
+		return nil, ErrPack
 	}
 	if res.Mangle != nil {
 		sending = res.Mangle(sending)
diff --git a/tsig.go b/tsig.go
index 60800f2c..958d14e8 100644
--- a/tsig.go
+++ b/tsig.go
@@ -101,7 +101,7 @@ func (t *Tsig) Generate(msg []byte) ([]byte, os.Error) {
 	// Create TSIG and add it to the message.
 	q := new(Msg)
 	if !q.Unpack(msg) {
-		return nil, &Error{Error: "Failed to unpack"}
+		return nil, ErrUnpack
 	}
 
 	rr := new(RR_TSIG)
@@ -116,7 +116,7 @@ func (t *Tsig) Generate(msg []byte) ([]byte, os.Error) {
 	q.Extra = append(q.Extra, rr)
 	send, ok := q.Pack()
 	if !ok {
-		return send, &Error{Error: "Failed to pack"}
+		return send, ErrPack
 	}
 	return send, nil
 }
@@ -132,7 +132,7 @@ func (t *Tsig) Verify(msg []byte) (bool, os.Error) {
 	// Stipped the TSIG from the incoming msg
 	stripped, ok := stripTsig(msg)
 	if !ok {
-		return false, &Error{Error: "Failed to strip tsig"}
+		return false, ErrSigGen
 	}
 
 	buf, err := t.Buffer(stripped)
@@ -162,7 +162,7 @@ func (t *Tsig) Buffer(msg []byte) ([]byte, os.Error) {
 		macbuf = make([]byte, len(t.RequestMAC)) // reqmac should be twice as long
 		n, ok := packStruct(m, macbuf, 0)
 		if !ok {
-			return nil, &Error{Error: "Failed to pack request mac"}
+			return nil, ErrSigGen
 		}
 		macbuf = macbuf[:n]
 	}
@@ -174,7 +174,7 @@ func (t *Tsig) Buffer(msg []byte) ([]byte, os.Error) {
 		tsig.Fudge = t.Fudge
 		n, ok1 := packStruct(tsig, tsigvar, 0)
 		if !ok1 {
-			return nil, &Error{Error: "Failed to pack timers"}
+			return nil, ErrSigGen
 		}
 		tsigvar = tsigvar[:n]
 	} else {
@@ -190,7 +190,7 @@ func (t *Tsig) Buffer(msg []byte) ([]byte, os.Error) {
 		tsig.OtherData = ""
 		n, ok1 := packStruct(tsig, tsigvar, 0)
 		if !ok1 {
-			return nil, &Error{Error: "Failed to pack tsig variables"}
+			return nil, ErrSigGen
 		}
 		tsigvar = tsigvar[:n]
 	}
diff --git a/types.go b/types.go
index cdf3b620..d74cc12a 100644
--- a/types.go
+++ b/types.go
@@ -61,7 +61,7 @@ const (
 
 	TypeTKEY = 249
 	TypeTSIG = 250
-	// valid Question.qtype only
+	// valid Question.Qtype only
 	TypeIXFR  = 251
 	TypeAXFR  = 252
 	TypeMAILB = 253
@@ -73,7 +73,7 @@ const (
 	TypeTA  = 32768
 	TypeDLV = 32769
 
-	// valid Question.qclass
+	// valid Question.Qclass
 	ClassINET   = 1
 	ClassCSNET  = 2
 	ClassCHAOS  = 3
diff --git a/xfr.go b/xfr.go
index 12322489..f61e99d7 100644
--- a/xfr.go
+++ b/xfr.go
@@ -35,7 +35,7 @@ func (d *Conn) XfrRead(q *Msg, m chan Xfr) {
 	case TypeIXFR:
 		d.ixfrRead(q, m)
         default:
-                m <- Xfr{true, nil, &Error{Error: "Qtype not recognized"}}
+                m <- Xfr{true, nil, &Error{Error: "Xfr Qtype not recognized"}}
                 close(m)
 	}
 }
@@ -51,7 +51,7 @@ func (d *Conn) XfrWrite(q *Msg, m chan Xfr) {
 	case TypeIXFR:
 		//                d.ixfrWrite(q, m)
         default:
-                m <- Xfr{true, nil, &Error{Error: "Qtype not recognized"}}
+                m <- Xfr{true, nil, &Error{Error: "Xfr Qtype not recognized"}}
                 close(m)
 	}
 }
@@ -67,13 +67,13 @@ func (d *Conn) axfrRead(q *Msg, m chan Xfr) {
 			return
 		}
 		if in.Id != q.Id {
-			m <- Xfr{true, nil, &Error{Error: "Id mismatch"}}
+			m <- Xfr{true, nil, ErrId}
 			return
 		}
 
 		if first {
 			if !checkXfrSOA(in, true) {
-				m <- Xfr{true, nil, &Error{Error: "SOA not first record"}}
+				m <- Xfr{true, nil, ErrXfrSoa}
 				return
 			}
 			first = !first
@@ -152,7 +152,7 @@ func (d *Conn) ixfrRead(q *Msg, m chan Xfr) {
 			return
 		}
 		if in.Id != q.Id {
-			m <- Xfr{true, nil, &Error{Error: "Id mismatch"}}
+			m <- Xfr{true, nil, ErrId}
 			return
 		}
 
@@ -164,7 +164,7 @@ func (d *Conn) ixfrRead(q *Msg, m chan Xfr) {
 
 			// But still check if the returned answer is ok
 			if !checkXfrSOA(in, true) {
-				m <- Xfr{true, nil, &Error{Error: "SOA not first record"}}
+				m <- Xfr{true, nil, ErrXfrSoa}
 				return
 			}
 			// This serial is important