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add support for SO_REUSEPORT #89

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add support for SO_REUSEPORT #89

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9 changes: 5 additions & 4 deletions connection.go
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,8 @@ import (

"golang.org/x/net/ipv4"
"golang.org/x/net/ipv6"

reuse "github.com/libp2p/go-reuseport"
)

var (
Expand All @@ -19,8 +21,7 @@ var (
Port: 5353,
}
mdnsWildcardAddrIPv6 = &net.UDPAddr{
IP: net.ParseIP("ff02::"),
// IP: net.ParseIP("fd00::12d3:26e7:48db:e7d"),
IP: net.ParseIP("ff02::"),
Port: 5353,
}

Expand All @@ -36,7 +37,7 @@ var (
)

func joinUdp6Multicast(interfaces []net.Interface) (*ipv6.PacketConn, error) {
udpConn, err := net.ListenUDP("udp6", mdnsWildcardAddrIPv6)
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Why we need SO_REUSEPORT? For multicast address, SO_REUSEPORT is the same as SO_REUSEADDR which was already set by default when you call net.ListenUDP.

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On the Debian Linux system I am running this on, I have a few other mdns services. When starting a service using this library net.ListenUDP would fail due to the port already being in use.

After switching it to use SO_REUSEPORT to be inline with all the other mDNS services I was able to successfully run it with the other services at the same time without issue. [1,2]

It is my understanding that SO_REUSEPORT is not needed if all the services are part of the same program (PID), but if they are not; SO_REUSEPORT is required to tell the kernel it is ok for different processes to share the same address/port. Which is required for mDNS.

[1] https://github.com/udp-redux/udp-broadcast-relay-redux/blob/master/main.c#L382
[2] https://github.com/lathiat/avahi/blob/d1e71b320d96d0f213ecb0885c8313039a09f693/avahi-core/socket.c#L178

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Thanks @lanrat for the details. After some digging and exercises, I agree that set both SO_REUSEADDR and SO_REUSEPORT is better than just setting SO_REUSEADDR.
I think the reason net.LIstenUDP failed in your env is some other mdns services running only enabled SO_REUSEPORT.

"It is my understanding that SO_REUSEPORT is not needed if all the services are part of the same program (PID), but if they are not; SO_REUSEPORT is required to tell the kernel it is ok for different processes to share the same address/port. Which is required for mDNS."
-> I don't agree with above comments. Based on my test, SO_REUSEADDR works quite well for multiple processes for mDNS.

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"It is my understanding that SO_REUSEPORT is not needed if all the services are part of the same program (PID), but if they are not; SO_REUSEPORT is required to tell the kernel it is ok for different processes to share the same address/port. Which is required for mDNS."
-> I don't agree with above comments. Based on my test, SO_REUSEADDR works quite well for multiple processes for mDNS.

This comment was based on the results of the limited testing I did, so I could very well be wrong here. I'll research this a bit more to fully understand what's going on.

Either way, adding SO_REUSEPORT does appear to fix the problem as I'm running 5+ mdns services on the same host.

udpConn, err := reuse.ListenPacket("udp6", mdnsWildcardAddrIPv6.String())
if err != nil {
return nil, err
}
Expand Down Expand Up @@ -66,7 +67,7 @@ func joinUdp6Multicast(interfaces []net.Interface) (*ipv6.PacketConn, error) {
}

func joinUdp4Multicast(interfaces []net.Interface) (*ipv4.PacketConn, error) {
udpConn, err := net.ListenUDP("udp4", mdnsWildcardAddrIPv4)
udpConn, err := reuse.ListenPacket("udp4", mdnsWildcardAddrIPv4.String())
if err != nil {
// log.Printf("[ERR] bonjour: Failed to bind to udp4 mutlicast: %v", err)
return nil, err
Expand Down
1 change: 1 addition & 0 deletions go.mod
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ go 1.13

require (
github.com/cenkalti/backoff v2.2.1+incompatible
github.com/libp2p/go-reuseport v0.0.2
github.com/miekg/dns v1.1.41
github.com/pkg/errors v0.9.1
golang.org/x/net v0.0.0-20210423184538-5f58ad60dda6
Expand Down
14 changes: 14 additions & 0 deletions go.sum
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Open in desktop
Original file line number Diff line number Diff line change
@@ -1,14 +1,24 @@
github.com/cenkalti/backoff v2.2.1+incompatible h1:tNowT99t7UNflLxfYYSlKYsBpXdEet03Pg2g16Swow4=
github.com/cenkalti/backoff v2.2.1+incompatible/go.mod h1:90ReRw6GdpyfrHakVjL/QHaoyV4aDUVVkXQJJJ3NXXM=
github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/libp2p/go-reuseport v0.0.2 h1:XSG94b1FJfGA01BUrT82imejHQyTxO4jEWqheyCXYvU=
github.com/libp2p/go-reuseport v0.0.2/go.mod h1:SPD+5RwGC7rcnzngoYC86GjPzjSywuQyMVAheVBD9nQ=
github.com/miekg/dns v1.1.41 h1:WMszZWJG0XmzbK9FEmzH2TVcqYzFesusSIB41b8KHxY=
github.com/miekg/dns v1.1.41/go.mod h1:p6aan82bvRIyn+zDIv9xYNUpwa73JcSh9BKwknJysuI=
github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
github.com/stretchr/testify v1.5.1 h1:nOGnQDM7FYENwehXlg/kFVnos3rEvtKTjRvOWSzb6H4=
github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
golang.org/x/net v0.0.0-20210423184538-5f58ad60dda6 h1:0PC75Fz/kyMGhL0e1QnypqK2kQMqKt9csD1GnMJR+Zk=
golang.org/x/net v0.0.0-20210423184538-5f58ad60dda6/go.mod h1:OJAsFXCWl8Ukc7SiCT/9KSuxbyM7479/AVlXFRxuMCk=
golang.org/x/sync v0.0.0-20210220032951-036812b2e83c h1:5KslGYwFpkhGh+Q16bwMP3cOontH8FOep7tGV86Y7SQ=
golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sys v0.0.0-20190228124157-a34e9553db1e/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20210303074136-134d130e1a04/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20210423082822-04245dca01da/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
Expand All @@ -18,3 +28,7 @@ golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9sn
golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=