device: receive: do not exit immediately on transient UDP receive errors

Some users report seeing lines like:

> Routine: receive incoming IPv4 - stopped

Popping up unexpectedly. Let's sleep and try again before failing, and
also log the error, and perhaps we'll eventually understand this
situation better in future versions.

Because we have to distinguish between the socket being closed
explicitly and whatever error this is, we bump the module to require Go
1.16.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

conn/conn_linux.go

@@ -204,7 +204,7 @@ func (bind *nativeBind) ReceiveIPv6(buff []byte) (int, Endpoint, error) {
 
 	var end NativeEndpoint
 	if bind.sock6 == -1 {
-		return 0, nil, syscall.EAFNOSUPPORT
+		return 0, nil, net.ErrClosed
 	}
 	n, err := receive6(
 		bind.sock6,
@@ -220,7 +220,7 @@ func (bind *nativeBind) ReceiveIPv4(buff []byte) (int, Endpoint, error) {
 
 	var end NativeEndpoint
 	if bind.sock4 == -1 {
-		return 0, nil, syscall.EAFNOSUPPORT
+		return 0, nil, net.ErrClosed
 	}
 	n, err := receive4(
 		bind.sock4,
@@ -237,12 +237,12 @@ func (bind *nativeBind) Send(buff []byte, end Endpoint) error {
 	nend := end.(*NativeEndpoint)
 	if !nend.isV6 {
 		if bind.sock4 == -1 {
-			return syscall.EAFNOSUPPORT
+			return net.ErrClosed
 		}
 		return send4(bind.sock4, nend, buff)
 	} else {
 		if bind.sock6 == -1 {
-			return syscall.EAFNOSUPPORT
+			return net.ErrClosed
 		}
 		return send6(bind.sock6, nend, buff)
 	}

device/receive.go

@@ -8,6 +8,7 @@ package device
 import (
 	"bytes"
 	"encoding/binary"
+	"errors"
 	"net"
 	"strconv"
 	"sync"
@@ -17,6 +18,7 @@ import (
 	"golang.org/x/crypto/chacha20poly1305"
 	"golang.org/x/net/ipv4"
 	"golang.org/x/net/ipv6"
+
 	"golang.zx2c4.com/wireguard/conn"
 )
 
@@ -120,12 +122,10 @@ func (device *Device) RoutineReceiveIncoming(IP int, bind conn.Bind) {
 		err         error
 		size        int
 		endpoint    conn.Endpoint
+		deathSpiral int
 	)
 
 	for {
-
-		// read next datagram
-
 		switch IP {
 		case ipv4.Version:
 			size, endpoint, err = bind.ReceiveIPv4(buffer[:])
@@ -137,8 +137,18 @@ func (device *Device) RoutineReceiveIncoming(IP int, bind conn.Bind) {
 
 		if err != nil {
 			device.PutMessageBuffer(buffer)
+			if errors.Is(err, net.ErrClosed) {
 				return
 			}
+			device.log.Error.Printf("Failed to receive packet: %v", err)
+			if deathSpiral < 10 {
+				deathSpiral++
+				time.Sleep(time.Second / 3)
+				continue
+			}
+			return
+		}
+		deathSpiral = 0
 
 		if size < MinMessageSize {
 			continue

go.mod

@@ -1,9 +1,9 @@
 module golang.zx2c4.com/wireguard
 
-go 1.14
+go 1.16
 
 require (
-	golang.org/x/crypto v0.0.0-20201124201722-c8d3bf9c5392
+	golang.org/x/crypto v0.0.0-20201221181555-eec23a3978ad
-	golang.org/x/net v0.0.0-20201110031124-69a78807bb2b
+	golang.org/x/net v0.0.0-20201224014010-6772e930b67b
-	golang.org/x/sys v0.0.0-20201126233918-771906719818
+	golang.org/x/sys v0.0.0-20210105210732-16f7687f5001
 )

go.sum

@@ -1,17 +1,16 @@
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
+golang.org/x/crypto v0.0.0-20201221181555-eec23a3978ad h1:DN0cp81fZ3njFcrLCytUHRSUkqBjfTo4Tx9RJTWs0EY=
-golang.org/x/crypto v0.0.0-20201124201722-c8d3bf9c5392 h1:xYJJ3S178yv++9zXV/hnr29plCAGO9vAFG9dorqaFQc=
+golang.org/x/crypto v0.0.0-20201221181555-eec23a3978ad/go.mod h1:jdWPYTVW3xRLrWPugEBEK3UY2ZEsg3UU495nc5E+M+I=
-golang.org/x/crypto v0.0.0-20201124201722-c8d3bf9c5392/go.mod h1:jdWPYTVW3xRLrWPugEBEK3UY2ZEsg3UU495nc5E+M+I=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/net v0.0.0-20201110031124-69a78807bb2b h1:uwuIcX0g4Yl1NC5XAz37xsr2lTtcqevgzYNVt49waME=
+golang.org/x/net v0.0.0-20201224014010-6772e930b67b h1:iFwSg7t5GZmB/Q5TjiEAsdoLDrdJRC1RiF2WhuV29Qw=
-golang.org/x/net v0.0.0-20201110031124-69a78807bb2b/go.mod h1:sp8m0HH+o8qH0wwXwYZr8TS3Oi6o0r6Gce1SSxlDquU=
+golang.org/x/net v0.0.0-20201224014010-6772e930b67b/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191026070338-33540a1f6037/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20201126233918-771906719818 h1:f1CIuDlJhwANEC2MM87MBEVMr3jl5bifgsfj90XAF9c=
+golang.org/x/sys v0.0.0-20210105210732-16f7687f5001 h1:/dSxr6gT0FNI1MO5WLJo8mTmItROeOKTkDn+7OwWBos=
-golang.org/x/sys v0.0.0-20201126233918-771906719818/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210105210732-16f7687f5001/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/term v0.0.0-20201117132131-f5c789dd3221/go.mod h1:Nr5EML6q2oocZ2LXRh80K7BxOlk5/8JxuGnuhpl+muw=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=