OVS 派OFPT_PORT_STATUS 流程

依据openflow合约[OFP1.0-38]，当从物理端口ovs datapath 添加，改动或者删除的时候。都会先运行详细动作。然后通过ofp_port_status异步消息告知Controller，比方当我们运行 ovs-vsctl add-port br0 eth0 之类的命令后，就会更新ovsdb数据库。某一个轮询时全局变量 reconfiguring
变为true，从而会又一次配置这个ovs。

if (reconfiguring) {
		// cfg 条目能够追踪到ovsdb中某个配置发生改变
        if (cfg) {
            if (!reconf_txn) {
                reconf_txn = ovsdb_idl_txn_create(idl);
            }
	// 又一次配置每一个cfg，核心入口
            if (bridge_reconfigure_continue(cfg)) {
                ovsrec_open_vswitch_set_cur_cfg(cfg, cfg->next_cfg);
            }
        } else {
            bridge_reconfigure_continue(&null_cfg);
        }
    }

接下来详细运行配置：

static bool
bridge_reconfigure_continue(const struct ovsrec_open_vswitch *ovs_cfg)
{
    struct sockaddr_in *managers;
    int sflow_bridge_number;
    size_t n_managers;
    struct bridge *br;
    bool done;

    assert(reconfiguring);
	// reconfigure首先要做的就是先删除旧端口，而后依据配置构建新端口
    done = bridge_reconfigure_ofp();

    /* Complete the configuration. */
    sflow_bridge_number = 0;
    collect_in_band_managers(ovs_cfg, &managers, &n_managers);
    HMAP_FOR_EACH (br, node, &all_bridges) {
        struct port *port;

        /* We need the datapath ID early to allow LACP ports to use it as the
         * default system ID. */
        bridge_configure_datapath_id(br);

        HMAP_FOR_EACH (port, hmap_node, &br->ports) {
            struct iface *iface;

            port_configure(port);

            LIST_FOR_EACH (iface, port_elem, &port->ifaces) {
                iface_configure_cfm(iface);
                iface_configure_qos(iface, port->cfg->qos);
                iface_set_mac(iface);
            }
        }
        bridge_configure_mirrors(br);
        bridge_configure_flow_eviction_threshold(br);
        bridge_configure_forward_bpdu(br);
        bridge_configure_mac_idle_time(br);
        bridge_configure_remotes(br, managers, n_managers);
        bridge_configure_netflow(br);
        bridge_configure_sflow(br, &sflow_bridge_number);
        bridge_configure_stp(br);
        bridge_configure_tables(br);
    }
    free(managers);

    if (done) {
        /* ovs-vswitchd has completed initialization, so allow the process that
         * forked us to exit successfully. */
        daemonize_complete();
        reconfiguring = false;

        VLOG_INFO("%s (Open vSwitch) %s", program_name, VERSION);
    }

    return done;
}

这里先删除全部的port，再加入：

static bool
bridge_reconfigure_ofp(void)
{
    long long int deadline;
    struct bridge *br;

    time_refresh();
    deadline = time_msec() + OFP_PORT_ACTION_WINDOW;

    /* The kernel will reject any attempt to add a given port to a datapath if
     * that port already belongs to a different datapath, so we must do all
     * port deletions before any port additions. */
    HMAP_FOR_EACH (br, node, &all_bridges) {
        struct ofpp_garbage *garbage, *next;

        LIST_FOR_EACH_SAFE (garbage, next, list_node, &br->ofpp_garbage) {
            /* It's a bit dangerous to call bridge_run_fast() here as ofproto's
             * internal datastructures may not be consistent.  Eventually, when
             * port additions and deletions are cheaper, these calls should be
             * removed. */
            bridge_run_fast();
            ofproto_port_del(br->ofproto, garbage->ofp_port);
            list_remove(&garbage->list_node);
            free(garbage);

            time_refresh();
            if (time_msec() >= deadline) {
                return false;
            }
            bridge_run_fast();
        }
    }

    HMAP_FOR_EACH (br, node, &all_bridges) {
        struct if_cfg *if_cfg, *next;

        HMAP_FOR_EACH_SAFE (if_cfg, next, hmap_node, &br->if_cfg_todo) {
			//这里是核心，在我们的ovs bridge上添加一个接口
            iface_create(br, if_cfg, -1);
            time_refresh();
            if (time_msec() >= deadline) {
                return false;
            }
        }
    }

    return true;
}

依据配置 if_cfg 给br添加一个interface，假设指定的openflowport号是负数。 则表示自己主动分配：

static bool
iface_create(struct bridge *br, struct if_cfg *if_cfg, int ofp_port)
{
    const struct ovsrec_interface *iface_cfg = if_cfg->cfg;
    const struct ovsrec_port *port_cfg = if_cfg->parent;

    struct netdev *netdev;
    struct iface *iface;
    struct port *port;
    int error;

    /* Get rid of 'if_cfg' itself.  We already copied out the interesting
     * bits. */
    hmap_remove(&br->if_cfg_todo, &if_cfg->hmap_node);
    free(if_cfg);

    /* Do the bits that can fail up front.
     *
     * It's a bit dangerous to call bridge_run_fast() here as ofproto's
     * internal datastructures may not be consistent.  Eventually, when port
     * additions and deletions are cheaper, these calls should be removed. */
    bridge_run_fast();
    assert(!iface_lookup(br, iface_cfg->name));
    error = iface_do_create(br, iface_cfg, port_cfg, &ofp_port, &netdev);
    bridge_run_fast();
    if (error) {
        iface_clear_db_record(iface_cfg);
        return false;
    }

    /* Get or create the port structure. */
    port = port_lookup(br, port_cfg->name);
    if (!port) {
        port = port_create(br, port_cfg);
    }

    /* Create the iface structure. */
    iface = xzalloc(sizeof *iface);
    list_push_back(&port->ifaces, &iface->port_elem);
    hmap_insert(&br->iface_by_name, &iface->name_node,
                hash_string(iface_cfg->name, 0));
    iface->port = port;
    iface->name = xstrdup(iface_cfg->name);
    iface->ofp_port = -1;
    iface->netdev = netdev;
    iface->type = iface_get_type(iface_cfg, br->cfg);
    iface->cfg = iface_cfg;

    iface_set_ofp_port(iface, ofp_port);

    /* Populate initial status in database. */
    iface_refresh_stats(iface);
    iface_refresh_status(iface);

    /* Add bond fake iface if necessary. */
    if (port_is_bond_fake_iface(port)) {
        struct ofproto_port ofproto_port;

        if (ofproto_port_query_by_name(br->ofproto, port->name,
                                       &ofproto_port)) {
            struct netdev *netdev;
            int error;

            error = netdev_open(port->name, "internal", &netdev);
            if (!error) {
				// 将这个网络设备增加到我们的openflow switch中
                ofproto_port_add(br->ofproto, netdev, NULL);
                netdev_close(netdev);
            } else {
                VLOG_WARN("could not open network device %s (%s)",
                          port->name, strerror(error));
            }
        } else {
            /* Already exists, nothing to do. */
            ofproto_port_destroy(&ofproto_port);
        }
    }

    return true;
}

调用ofproto(openflow sw接口)详细实现的port_add方法：

int
ofproto_port_add(struct ofproto *ofproto, struct netdev *netdev,
                 uint16_t *ofp_portp)
{
    uint16_t ofp_port;
    int error;

    error = ofproto->ofproto_class->port_add(ofproto, netdev, &ofp_port);
	// 看 dpif_linux_class 的详细实现
    if (!error) {
		// 更新我们的openflow交换机(即ofproto)
        update_port(ofproto, netdev_get_name(netdev));
    }
    if (ofp_portp) {
        *ofp_portp = error ? OFPP_NONE : ofp_port;
    }
    return error;
}

static void
update_port(struct ofproto *ofproto, const char *name)
{
    struct ofproto_port ofproto_port;
    struct ofputil_phy_port pp;
    struct netdev *netdev;
    struct ofport *port;

    COVERAGE_INC(ofproto_update_port);

    /* Fetch 'name''s location and properties from the datapath. */
    netdev = (!ofproto_port_query_by_name(ofproto, name, &ofproto_port)
              ? ofport_open(ofproto, &ofproto_port, &pp)
              : NULL);
    if (netdev) {
        port = ofproto_get_port(ofproto, ofproto_port.ofp_port);
        if (port && !strcmp(netdev_get_name(port->netdev), name)) {
            struct netdev *old_netdev = port->netdev;

            /* 'name' hasn't changed location.  Any properties changed? */
            if (!ofport_equal(&port->pp, &pp)) {
                ofport_modified(port, &pp);
            }

            update_mtu(ofproto, port);

            /* Install the newly opened netdev in case it has changed.
             * Don't close the old netdev yet in case port_modified has to
             * remove a retained reference to it.*/
            port->netdev = netdev;
            port->change_seq = netdev_change_seq(netdev);

            if (port->ofproto->ofproto_class->port_modified) {
                port->ofproto->ofproto_class->port_modified(port);
            }

            netdev_close(old_netdev);
        } else {
            /* If 'port' is nonnull then its name differs from 'name' and thus
             * we should delete it.  If we think there's a port named 'name'
             * then its port number must be wrong now so delete it too. */
            if (port) {
                ofport_remove(port);
            }
            ofport_remove_with_name(ofproto, name);
			// 看这里
            ofport_install(ofproto, netdev, &pp);
        }
    } else {
        /* Any port named 'name' is gone now. */
        ofport_remove_with_name(ofproto, name);
    }
    ofproto_port_destroy(&ofproto_port);
}

static void
ofport_install(struct ofproto *p,
               struct netdev *netdev, const struct ofputil_phy_port *pp)
{
    const char *netdev_name = netdev_get_name(netdev);
    struct ofport *ofport;
    int error;

    /* Create ofport. */
    ofport = p->ofproto_class->port_alloc();
    if (!ofport) {
        error = ENOMEM;
        goto error;
    }
    ofport->ofproto = p;
    ofport->netdev = netdev;
    ofport->change_seq = netdev_change_seq(netdev);
    ofport->pp = *pp;
    ofport->ofp_port = pp->port_no;

    /* Add port to 'p'. */
    hmap_insert(&p->ports, &ofport->hmap_node, hash_int(ofport->ofp_port, 0));
    shash_add(&p->port_by_name, netdev_name, ofport);

    update_mtu(p, ofport);

    /* Let the ofproto_class initialize its private data. */
    error = p->ofproto_class->port_construct(ofport);
    if (error) {
        goto error;
    }
	// 更新操作完毕后。发送通知消息到Controller
    connmgr_send_port_status(p->connmgr, pp, OFPPR_ADD);
    return;

error:
    VLOG_WARN_RL(&rl, "%s: could not add port %s (%s)",
                 p->name, netdev_name, strerror(error));
    if (ofport) {
        ofport_destroy__(ofport);
    } else {
        netdev_close(netdev);
    }
}

发送port_status 和端口改变原因到SDN Controller：

void
connmgr_send_port_status(struct connmgr *mgr,
                         const struct ofputil_phy_port *pp, uint8_t reason)
{
    /* XXX Should limit the number of queued port status change messages. */
    struct ofputil_port_status ps;
    struct ofconn *ofconn;

    ps.reason = reason;
    ps.desc = *pp;
    LIST_FOR_EACH (ofconn, node, &mgr->all_conns) {
        if (ofconn_receives_async_msg(ofconn, OAM_PORT_STATUS, reason)) {
            struct ofpbuf *msg;

            msg = ofputil_encode_port_status(&ps, ofconn->protocol);
            ofconn_send(ofconn, msg, NULL);
        }
    }
}

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