bgp: support specifying next hop for neighbor

neighbor_add method takes 'next_hop' parameter. If not specified, like
before, host's ip connected to the neighbor is used as a next hop.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

ryu/services/protocols/bgp/bgpspeaker.py

@@ -50,6 +50,7 @@
 from ryu.services.protocols.bgp.rtconf.neighbors import DEFAULT_CAP_MBGP_IPV4
 from ryu.services.protocols.bgp.rtconf.neighbors import DEFAULT_CAP_MBGP_VPNV4
 from ryu.services.protocols.bgp.rtconf.neighbors import DEFAULT_CAP_MBGP_VPNV6
+from ryu.services.protocols.bgp.rtconf.neighbors import PEER_NEXT_HOP
 from ryu.services.protocols.bgp.application import RyuBGPSpeaker
 
 
@@ -165,7 +166,8 @@ def shutdown(self):
     def neighbor_add(self, address, remote_as,
                      enable_ipv4=DEFAULT_CAP_MBGP_IPV4,
                      enable_vpnv4=DEFAULT_CAP_MBGP_VPNV4,
-                     enable_vpnv6=DEFAULT_CAP_MBGP_VPNV6):
+                     enable_vpnv6=DEFAULT_CAP_MBGP_VPNV6,
+                     next_hop=None):
         """ This method registers a new neighbor. The BGP speaker tries to
         establish a bgp session with the peer (accepts a connection
         from the peer and also tries to connect to it).
@@ -186,10 +188,13 @@ def neighbor_add(self, address, remote_as,
         ``enable_vpnv6`` enables VPNv6 address family for this
         neighbor. The default is False.
 
+        ``next_hop`` specifies the next hop IP address. If not
+        specified, host's ip address to access to a peer is used.
         """
         bgp_neighbor = {}
         bgp_neighbor[neighbors.IP_ADDRESS] = address
         bgp_neighbor[neighbors.REMOTE_AS] = remote_as
+        bgp_neighbor[PEER_NEXT_HOP] = next_hop
         # v6 advertizement is available with only v6 peering
         if netaddr.valid_ipv4(address):
             bgp_neighbor[CAP_MBGP_IPV4] = enable_ipv4

ryu/services/protocols/bgp/peer.py

@@ -590,7 +590,10 @@ def _session_next_hop(self, route_family):
         point/local ip address.
         """
         # By default we use BGPS's interface IP with this peer as next_hop.
-        next_hop = self.host_bind_ip
+        if self._neigh_conf.next_hop:
+            next_hop = self._neigh_conf.next_hop
+        else:
+            next_hop = self.host_bind_ip
         if route_family == RF_IPv6_VPN:
             # Next hop ipv4_mapped ipv6
             def _ipv4_mapped_ipv6(ipv4):

ryu/services/protocols/bgp/rtconf/neighbors.py

@@ -71,6 +71,7 @@
 CHANGES = 'changes'
 LOCAL_ADDRESS = 'local_address'
 LOCAL_PORT = 'local_port'
+PEER_NEXT_HOP = 'next_hop'
 
 # Default value constants.
 DEFAULT_CAP_GR_NULL = True
@@ -132,6 +133,14 @@ def validate_local_address(ip_address):
     return str(netaddr.IPAddress(ip_address))
 
 
+@validate(name=PEER_NEXT_HOP)
+def validate_next_hop(ip_address):
+    if not valid_ip_address(ip_address):
+        raise ConfigValueError(desc='Invalid next_hop ip_address: %s' %
+                               ip_address)
+    return str(netaddr.IPAddress(ip_address))
+
+
 @validate(name=LOCAL_PORT)
 def validate_local_port(port):
     if not isinstance(port, (int, long)):
@@ -164,7 +173,8 @@ class NeighborConf(ConfWithId, ConfWithStats):
                                    CAP_RTC, RTC_AS, HOLD_TIME,
                                    ENABLED, MULTI_EXIT_DISC, MAX_PREFIXES,
                                    ADVERTISE_PEER_AS, SITE_OF_ORIGINS,
-                                   LOCAL_ADDRESS, LOCAL_PORT])
+                                   LOCAL_ADDRESS, LOCAL_PORT,
+                                   PEER_NEXT_HOP])
 
     def __init__(self, **kwargs):
         super(NeighborConf, self).__init__(**kwargs)
@@ -213,6 +223,9 @@ def _init_opt_settings(self, **kwargs):
         self._settings[LOCAL_PORT] = compute_optional_conf(
             LOCAL_PORT, None, **kwargs)
 
+        self._settings[PEER_NEXT_HOP] = compute_optional_conf(
+            PEER_NEXT_HOP, None, **kwargs)
+
         # RTC configurations.
         self._settings[CAP_RTC] = \
             compute_optional_conf(CAP_RTC, DEFAULT_CAP_RTC, **kwargs)
@@ -265,6 +278,10 @@ def host_bind_ip(self):
     def host_bind_port(self):
         return self._settings[LOCAL_PORT]
 
+    @property
+    def next_hop(self):
+        return self._settings[PEER_NEXT_HOP]
+
     # =========================================================================
     # Optional attributes with valid defaults.
     # =========================================================================