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);
}
}
}