[ovs-dev] Why updating ports upon ofproto_port_add?

[Min Chen]

Hi all,

I am reading source code of Open vSwitch 1.4.0. I have a question on
updating ports immediately upon ofproto_port_add

I searched this mailing list and I found Ben's
comment<http://openvswitch.org/pipermail/dev/2011-May/008561.html>on
updating ports after port_add. Ben wrote "I don't see a reason to
defer
this." But what dose update_port do?

ofproto.c
1103 int
1104 ofproto_port_add(struct ofproto *ofproto, struct netdev *netdev,
1105                  uint16_t *ofp_portp)
1106 {
1107     uint16_t ofp_port;
1108     int error;
1109
1110     error = ofproto->ofproto_class->port_add(ofproto, netdev,
&ofp_port);
1111     if (!error) {
1112         update_port(ofproto, netdev_get_name(netdev));
1113     }
1114     if (ofp_portp) {
1115         *ofp_portp = error ? OFPP_NONE : ofp_port;
1116     }
1117     return error;
1118 }

Since netdev is opened before calling ofproto_port_add, why it's opened
again in update_port:

ofproto.c
1492     netdev = (!ofproto_port_query_by_name(ofproto, name, &ofproto_port)
1493               ? ofport_open(&ofproto_port, &opp)
1494               : NULL);

There are comments inside this update_port. But still I can't figure out
what this function does. Can anyone explain a bit to me? Thanks.
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