Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Support dig based unicast requests #178

Merged
merged 1 commit into from
Feb 9, 2024
Merged

Support dig based unicast requests #178

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
44 changes: 36 additions & 8 deletions conn.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
package mdns

import (
"bytes"
"context"
"errors"
"fmt"
Expand Down Expand Up @@ -265,24 +266,36 @@ func Server(
if err := multicastPktConnV4.SetControlMessage(ipv4.FlagInterface, true); err != nil {
c.log.Warnf("failed to SetControlMessage(ipv4.FlagInterface) on multicast IPv4 PacketConn %v", err)
}
if err := multicastPktConnV4.SetControlMessage(ipv4.FlagDst, true); err != nil {
c.log.Warnf("failed to SetControlMessage(ipv4.FlagDst) on multicast IPv4 PacketConn %v", err)
}
c.multicastPktConnV4 = ipPacketConn4{multicastPktConnV4, log}
}
if multicastPktConnV6 != nil {
if err := multicastPktConnV6.SetControlMessage(ipv6.FlagInterface, true); err != nil {
c.log.Warnf("failed to SetControlMessage(ipv6.FlagInterface) on multicast IPv6 PacketConn %v", err)
}
if err := multicastPktConnV6.SetControlMessage(ipv6.FlagDst, true); err != nil {
c.log.Warnf("failed to SetControlMessage(ipv6.FlagInterface) on multicast IPv6 PacketConn %v", err)
}
c.multicastPktConnV6 = ipPacketConn6{multicastPktConnV6, log}
}
if unicastPktConnV4 != nil {
if err := unicastPktConnV4.SetControlMessage(ipv4.FlagInterface, true); err != nil {
c.log.Warnf("failed to SetControlMessage(ipv4.FlagInterface) on unicast IPv4 PacketConn %v", err)
}
if err := unicastPktConnV4.SetControlMessage(ipv4.FlagDst, true); err != nil {
c.log.Warnf("failed to SetControlMessage(ipv4.FlagInterface) on unicast IPv4 PacketConn %v", err)
}
c.unicastPktConnV4 = ipPacketConn4{unicastPktConnV4, log}
}
if unicastPktConnV6 != nil {
if err := unicastPktConnV6.SetControlMessage(ipv6.FlagInterface, true); err != nil {
c.log.Warnf("failed to SetControlMessage(ipv6.FlagInterface) on unicast IPv6 PacketConn %v", err)
}
if err := unicastPktConnV6.SetControlMessage(ipv6.FlagDst, true); err != nil {
c.log.Warnf("failed to SetControlMessage(ipv6.FlagInterface) on unicast IPv6 PacketConn %v", err)
}
c.unicastPktConnV6 = ipPacketConn6{unicastPktConnV6, log}
}

Expand Down Expand Up @@ -624,14 +637,15 @@ func (c *Conn) writeToSocket(ifIndex int, b []byte, hasLoopbackData bool, wType
}
}

func createAnswer(name string, addr net.IP) (dnsmessage.Message, error) {
func createAnswer(id uint16, name string, addr net.IP) (dnsmessage.Message, error) {
packedName, err := dnsmessage.NewName(name)
if err != nil {
return dnsmessage.Message{}, err
}

msg := dnsmessage.Message{
Header: dnsmessage.Header{
ID: id,
Response: true,
Authoritative: true,
},
Expand Down Expand Up @@ -669,8 +683,8 @@ func createAnswer(name string, addr net.IP) (dnsmessage.Message, error) {
return msg, nil
}

func (c *Conn) sendAnswer(name string, ifIndex int, result net.IP, dst *net.UDPAddr) {
answer, err := createAnswer(name, result)
func (c *Conn) sendAnswer(queryID uint16, name string, ifIndex int, result net.IP, dst *net.UDPAddr) {
answer, err := createAnswer(queryID, name, result)
if err != nil {
c.log.Warnf("failed to create mDNS answer %v", err)
return
Expand All @@ -687,6 +701,7 @@ func (c *Conn) sendAnswer(name string, ifIndex int, result net.IP, dst *net.UDPA

type ipControlMessage struct {
IfIndex int
Dst net.IP
}

type ipPacketConn interface {
Expand All @@ -705,7 +720,7 @@ func (c ipPacketConn4) ReadFrom(b []byte) (n int, cm *ipControlMessage, src net.
if err != nil || cm4 == nil {
return n, nil, src, err
}
return n, &ipControlMessage{IfIndex: cm4.IfIndex}, src, err
return n, &ipControlMessage{IfIndex: cm4.IfIndex, Dst: cm4.Dst}, src, err
}

func (c ipPacketConn4) WriteTo(b []byte, via *net.Interface, cm *ipControlMessage, dst net.Addr) (n int, err error) {
Expand Down Expand Up @@ -736,7 +751,7 @@ func (c ipPacketConn6) ReadFrom(b []byte) (n int, cm *ipControlMessage, src net.
if err != nil || cm6 == nil {
return n, nil, src, err
}
return n, &ipControlMessage{IfIndex: cm6.IfIndex}, src, err
return n, &ipControlMessage{IfIndex: cm6.IfIndex, Dst: cm6.Dst}, src, err
}

func (c ipPacketConn6) WriteTo(b []byte, via *net.Interface, cm *ipControlMessage, dst net.Addr) (n int, err error) {
Expand Down Expand Up @@ -773,8 +788,10 @@ func (c *Conn) readLoop(name string, pktConn ipPacketConn, inboundBufferSize int
c.log.Debugf("got read on %s from %s", name, src)

var ifIndex int
var pktDst net.IP
if cm != nil {
ifIndex = cm.IfIndex
pktDst = cm.Dst
}
srcAddr, ok := src.(*net.UDPAddr)
if !ok {
Expand All @@ -783,7 +800,8 @@ func (c *Conn) readLoop(name string, pktConn ipPacketConn, inboundBufferSize int
}

func() {
if _, err := p.Start(b[:n]); err != nil {
header, err := p.Start(b[:n])
if err != nil {
c.log.Warnf("failed to parse mDNS packet %v", err)
return
}
Expand All @@ -801,7 +819,17 @@ func (c *Conn) readLoop(name string, pktConn ipPacketConn, inboundBufferSize int
continue
}

shouldUnicastResponse := (q.Class & (1 << 15)) != 0
// https://datatracker.ietf.org/doc/html/rfc6762#section-6
// The destination UDP port in all Multicast DNS responses MUST be 5353,
// and the destination address MUST be the mDNS IPv4 link-local
// multicast address 224.0.0.251 or its IPv6 equivalent FF02::FB, except
// when generating a reply to a query that explicitly requested a
// unicast response
shouldUnicastResponse :=
(q.Class&(1<<15)) != 0 || // via the unicast-response bit
srcAddr.Port != 5353 || // by virtue of being a legacy query (Section 6.7), or
(len(pktDst) != 0 && !(bytes.Equal(pktDst, c.dstAddr4.IP) || // by virtue of being a direct unicast query
bytes.Equal(pktDst, c.dstAddr6.IP)))
var dst *net.UDPAddr
if shouldUnicastResponse {
dst = srcAddr
Expand Down Expand Up @@ -883,7 +911,7 @@ func (c *Conn) readLoop(name string, pktConn ipPacketConn, inboundBufferSize int
continue
}
}
c.sendAnswer(q.Name.String(), ifIndex, localAddress, dst)
c.sendAnswer(header.ID, q.Name.String(), ifIndex, localAddress, dst)
}
}
}
Expand Down
12 changes: 2 additions & 10 deletions conn_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -659,23 +659,15 @@ func TestResourceParsing(t *testing.T) {
name := "test-server."

t.Run("A Record", func(t *testing.T) {
answer, err := createAnswer(name, net.IP{127, 0, 0, 1})
answer, err := createAnswer(1, name, net.IP{127, 0, 0, 1})
if err != nil {
t.Fatal(err)
}
lookForIP(answer, []byte{127, 0, 0, 1}, t)
})

t.Run("AAAA Record", func(t *testing.T) {
// because it's compatible
answer, err := createAnswer(name, net.ParseIP("127.0.0.1"))
if err != nil {
t.Fatal(err)
}
// this is wrong...?
lookForIP(answer, []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 255, 255, 127, 0, 0, 1}, t)

answer, err = createAnswer(name, net.ParseIP("::1"))
answer, err := createAnswer(1, name, net.ParseIP("::1"))
if err != nil {
t.Fatal(err)
}
Expand Down