broker: Allow ports to be re-used

The kernel requires each L2TPv3 tunnel to have it's own socket. Since we
would like to have all connections go through the same port we need to
allow port reusal.

Signed-off-by: Felix Kaechele <felix@kaechele.ca>

broker/src/tunneldigger_broker/network.py

@@ -9,9 +9,6 @@
 
 from . import protocol
 
-# Socket options.
-SO_BINDTODEVICE = 25
-
 # Logger.
 logger = logging.getLogger("tunneldigger.network")
 
@@ -35,8 +32,9 @@ def __init__(self, address, interface):
         """
 
         self.socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
+        self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_BINDTODEVICE, interface.encode('utf-8'))
         self.socket.bind(address)
-        self.socket.setsockopt(socket.SOL_SOCKET, SO_BINDTODEVICE, interface.encode('utf-8'))
 
         self.address = address
         self.interface = interface