netif: fix kni failing to work problem when netif ports hot plugging

Even though netif ports hot plugging is unsafe in dpvs, the patch makes
kni devices function properly and correctly.

Signed-off-by: ywc689 <ywc689@163.com>

src/netif.c

@@ -2859,9 +2859,10 @@ static void kni_egress(struct netif_port *port)
 static void kni_egress_process(void)
 {
     struct netif_port *dev;
-    portid_t id;
+    portid_t id, total;
 
-    for (id = 0; id < g_nports; id++) {
+    total = netif_port_count();
+    for (id = 0; id < total; id++) {
         dev = netif_port_get(id);
         if (!dev)
             continue;
@@ -2881,14 +2882,15 @@ static void kni_ingress_process(void)
     struct rte_mbuf *mbufs[NETIF_MAX_PKT_BURST];
     struct netif_port *dev;
     uint16_t i, pkt_total, pkt_sent;
-    portid_t id;
+    portid_t id, total;
     lcoreid_t cid = rte_lcore_id();
 #ifdef CONFIG_KNI_VIRTIO_USER
     struct virtio_kni *virtio_kni;
     static unsigned seq = 0;
 #endif
 
-    for (id = 0; id < g_nports; id++) {
+    total = netif_port_count();
+    for (id = 0; id < total; id++) {
         dev = netif_port_get(id);
         if (!dev || !kni_dev_running(dev))
             continue;
@@ -3246,6 +3248,17 @@ static inline int port_name_alloc(portid_t pid, char *pname, size_t buflen)
 
 static inline portid_t netif_port_id_alloc(void)
 {
+    // The netif_port_id_alloc ensures the relation `g_nports == port_id_end` always stands,
+    // which means all ids in range [0, port_id_end) are assgined to ports.
+    portid_t pid;
+
+    if (port_id_end > g_nports) {
+        for (pid = port_id_end - 1; pid != 0; pid--) {
+            if (netif_port_get(pid) == NULL)
+                return pid;
+        }
+    }
+
     return port_id_end++;
 }