net: refactor tap initialization

Re-factor things so that there is only one call site for
net_tap_fd_init().

Two concerns about the QemuOpts usage here - firstly, we set the script
arguments to their default value and, secondly, we set the ifname value
to the name allocated by the kernel if none is supplied. Are we okay
with such things ending up in writeconfig output?
Signed-off-by: NMark McLoughlin <markmc@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

net.c

@@ -1490,7 +1490,6 @@ static TAPState *net_tap_fd_init(VLANState *vlan,
                                  tap_receive, tap_receive_iov,
                                  tap_cleanup, s);
     tap_read_poll(s, 1);
-    snprintf(s->vc->info_str, sizeof(s->vc->info_str), "fd=%d", fd);
     return s;
 }
 
@@ -1739,38 +1738,34 @@ static int launch_script(const char *setup_script, const char *ifname, int fd)
     return -1;
 }
 
-static TAPState *net_tap_init(VLANState *vlan, const char *model,
-                              const char *name, const char *ifname1,
-                              const char *setup_script, const char *down_script)
+static int net_tap_init(QemuOpts *opts, int *vnet_hdr)
 {
-    TAPState *s;
-    int fd, vnet_hdr;
-    char ifname[128];
+    int fd;
+    char ifname[128] = {0,};
+    const char *setup_script;
 
-    if (ifname1 != NULL)
-        pstrcpy(ifname, sizeof(ifname), ifname1);
-    else
-        ifname[0] = '\0';
-    vnet_hdr = 0;
-    TFR(fd = tap_open(ifname, sizeof(ifname), &vnet_hdr));
-    if (fd < 0)
-        return NULL;
+    if (qemu_opt_get(opts, "ifname")) {
+        pstrcpy(ifname, sizeof(ifname), qemu_opt_get(opts, "ifname"));
+    }
 
-    if (!setup_script || !strcmp(setup_script, "no"))
-        setup_script = "";
-    if (setup_script[0] != '\0' &&
-        launch_script(setup_script, ifname, fd)) {
-        return NULL;
+    *vnet_hdr = 0;
+    TFR(fd = tap_open(ifname, sizeof(ifname), vnet_hdr));
+    if (fd < 0) {
+        return -1;
     }
-    s = net_tap_fd_init(vlan, model, name, fd, vnet_hdr);
-    snprintf(s->vc->info_str, sizeof(s->vc->info_str),
-             "ifname=%s,script=%s,downscript=%s",
-             ifname, setup_script, down_script);
-    if (down_script && strcmp(down_script, "no")) {
-        snprintf(s->down_script, sizeof(s->down_script), "%s", down_script);
-        snprintf(s->down_script_arg, sizeof(s->down_script_arg), "%s", ifname);
+
+    setup_script = qemu_opt_get(opts, "script");
+    if (setup_script &&
+        setup_script[0] != '\0' &&
+        strcmp(setup_script, "no") != 0 &&
+        launch_script(setup_script, ifname, fd)) {
+        close(fd);
+        return -1;
     }
-    return s;
+
+    qemu_opt_set(opts, "ifname", ifname);
+
+    return fd;
 }
 
 #endif /* !_WIN32 */
@@ -2698,10 +2693,9 @@ static int net_init_tap(QemuOpts *opts,
                         VLANState *vlan)
 {
     TAPState *s;
+    int fd, vnet_hdr;
 
     if (qemu_opt_get(opts, "fd")) {
-        int fd;
-
         if (qemu_opt_get(opts, "ifname") ||
             qemu_opt_get(opts, "script") ||
             qemu_opt_get(opts, "downscript")) {
@@ -2716,28 +2710,22 @@ static int net_init_tap(QemuOpts *opts,
 
         fcntl(fd, F_SETFL, O_NONBLOCK);
 
-        s = net_tap_fd_init(vlan, "tap", name, fd, tap_probe_vnet_hdr(fd));
-        if (!s) {
-            close(fd);
-        }
+        vnet_hdr = tap_probe_vnet_hdr(fd);
     } else {
-        const char *ifname, *script, *downscript;
-
-        ifname     = qemu_opt_get(opts, "ifname");
-        script     = qemu_opt_get(opts, "script");
-        downscript = qemu_opt_get(opts, "downscript");
-
-        if (!script) {
-            script = DEFAULT_NETWORK_SCRIPT;
+        if (!qemu_opt_get(opts, "script")) {
+            qemu_opt_set(opts, "script", DEFAULT_NETWORK_SCRIPT);
         }
-        if (!downscript) {
-            downscript = DEFAULT_NETWORK_DOWN_SCRIPT;
+
+        if (!qemu_opt_get(opts, "downscript")) {
+            qemu_opt_set(opts, "downscript", DEFAULT_NETWORK_DOWN_SCRIPT);
         }
 
-        s = net_tap_init(vlan, "tap", name, ifname, script, downscript);
+        fd = net_tap_init(opts, &vnet_hdr);
     }
 
+    s = net_tap_fd_init(vlan, "tap", name, fd, vnet_hdr);
     if (!s) {
+        close(fd);
         return -1;
     }
 
@@ -2745,6 +2733,25 @@ static int net_init_tap(QemuOpts *opts,
         return -1;
     }
 
+    if (qemu_opt_get(opts, "fd")) {
+        snprintf(s->vc->info_str, sizeof(s->vc->info_str), "fd=%d", fd);
+    } else {
+        const char *ifname, *script, *downscript;
+
+        ifname     = qemu_opt_get(opts, "ifname");
+        script     = qemu_opt_get(opts, "script");
+        downscript = qemu_opt_get(opts, "downscript");
+
+        snprintf(s->vc->info_str, sizeof(s->vc->info_str),
+                 "ifname=%s,script=%s,downscript=%s",
+                 ifname, script, downscript);
+
+        if (strcmp(downscript, "no") != 0) {
+            snprintf(s->down_script, sizeof(s->down_script), "%s", downscript);
+            snprintf(s->down_script_arg, sizeof(s->down_script_arg), "%s", ifname);
+        }
+    }
+
     if (vlan) {
         vlan->nb_host_devs++;
     }