Fixed port overwrite issue on kernels without ipv6

Fixed an issue in CreateBind for Linux:
If ipv6 was not supported the error code would be
correctly identified as EAFNOSUPPORT and ipv4 binding attempted.
However the port would be set to 0,
which results in the subsequent create4 call requesting
a random port rather than the one provided to CreateBind.

This issue was identified by:
Kent Friis <leeloored@gmx.com>

diff --git a/conn_linux.go b/conn_linux.go
index db0e3a645c9e411c3c4793aa42902c9d1ba4ae5e..08499206adc50a2e996c510137794b314ac1691f 100644 (file)
--- a/conn_linux.go
+++ b/conn_linux.go
@@ -27,6 +27,10 @@ import (
        "unsafe"
 )
 
+const (
+       FD_ERR = -1
+)
+
 type IPv4Source struct {
        src     [4]byte
        ifindex int32
@@ -126,6 +130,7 @@ func createNetlinkRouteSocket() (int, error) {
 func CreateBind(port uint16, device *Device) (*NativeBind, uint16, error) {
        var err error
        var bind NativeBind
+       var newPort uint16
 
        bind.netlinkSock, err = createNetlinkRouteSocket()
        if err != nil {
@@ -139,18 +144,35 @@ func CreateBind(port uint16, device *Device) (*NativeBind, uint16, error) {
 
        go bind.routineRouteListener(device)
 
-       bind.sock6, port, err = create6(port)
-       if err != nil && err != syscall.EAFNOSUPPORT {
-               bind.netlinkCancel.Cancel()
-               return nil, 0, err
+       // attempt ipv6 bind, update port if succesful
+
+       bind.sock6, newPort, err = create6(port)
+       if err != nil {
+               if err != syscall.EAFNOSUPPORT {
+                       bind.netlinkCancel.Cancel()
+                       return nil, 0, err
+               }
+       } else {
+               port = newPort
        }
 
-       bind.sock4, port, err = create4(port)
-       if err != nil && err != syscall.EAFNOSUPPORT {
-               bind.netlinkCancel.Cancel()
-               unix.Close(bind.sock6)
-               return nil, 0, err
+       // attempt ipv4 bind, update port if succesful
+
+       bind.sock4, newPort, err = create4(port)
+       if err != nil {
+               if err != syscall.EAFNOSUPPORT {
+                       bind.netlinkCancel.Cancel()
+                       unix.Close(bind.sock6)
+                       return nil, 0, err
+               }
+       } else {
+               port = newPort
        }
+
+       if bind.sock4 == FD_ERR && bind.sock6 == FD_ERR {
+               return nil, 0, errors.New("ipv4 and ipv6 not supported")
+       }
+
        return &bind, port, nil
 }
 
@@ -334,7 +356,7 @@ func create4(port uint16) (int, uint16, error) {
        )
 
        if err != nil {
-               return -1, 0, err
+               return FD_ERR, 0, err
        }
 
        addr := unix.SockaddrInet4{
@@ -365,7 +387,7 @@ func create4(port uint16) (int, uint16, error) {
                return unix.Bind(fd, &addr)
        }(); err != nil {
                unix.Close(fd)
-               return -1, 0, err
+               return FD_ERR, 0, err
        }
 
        return fd, uint16(addr.Port), err
@@ -382,7 +404,7 @@ func create6(port uint16) (int, uint16, error) {
        )
 
        if err != nil {
-               return -1, 0, err
+               return FD_ERR, 0, err
        }
 
        // set sockopts and bind
@@ -424,7 +446,7 @@ func create6(port uint16) (int, uint16, error) {
 
        }(); err != nil {
                unix.Close(fd)
-               return -1, 0, err
+               return FD_ERR, 0, err
        }
 
        return fd, uint16(addr.Port), err