Re: [Qemu-devel] [PATCH v2] ifname=xxx for -netdev bridge

[Alexandre Kandalintsev <spam@messir.net>]

Eric Blake <eblake@redhat.com> wrote:
> You also need to add a line documenting this field:
> 
> # @ifname: #optional Set the interface name that will be used (since
> 1.5).

Done. I also added an example with -netdev and -device
(seems this question is not covered in docs).


Signed-off-by: Alexandre Kandalintsev <spam@messir.net>
---
 include/net/net.h    |  1 +
 net/tap.c            | 25 ++++++++++++++++---------
 qapi-schema.json     |  1 +
 qemu-bridge-helper.c | 12 ++++++++++--
 qemu-options.hx      | 18 ++++++++++++++++--
 5 files changed, 44 insertions(+), 13 deletions(-)

diff --git a/include/net/net.h b/include/net/net.h
index cb049a1..4b25eb5 100644
--- a/include/net/net.h
+++ b/include/net/net.h
@@ -172,6 +172,7 @@ NetClientState *net_hub_port_find(int hub_id);
 #define DEFAULT_NETWORK_DOWN_SCRIPT "/etc/qemu-ifdown"
 #define DEFAULT_BRIDGE_HELPER CONFIG_QEMU_HELPERDIR "/qemu-bridge-helper"
 #define DEFAULT_BRIDGE_INTERFACE "br0"
+#define DEFAULT_BRIDGE_IFNAME "tap%d"
 
 void qdev_set_nic_properties(DeviceState *dev, NICInfo *nd);
 
diff --git a/net/tap.c b/net/tap.c
index ce79699..d1d5b6a 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -424,11 +424,11 @@ static int recv_fd(int c)
     return len;
 }
 
-static int net_bridge_run_helper(const char *helper, const char *bridge)
+static int net_bridge_run_helper(const char *helper, const char *bridge, const char *ifname)
 {
     sigset_t oldmask, mask;
     int pid, status;
-    char *args[5];
+    char *args[6];
     char **parg;
     int sv[2];
 
@@ -446,6 +446,7 @@ static int net_bridge_run_helper(const char *helper, const char *bridge)
         int open_max = sysconf(_SC_OPEN_MAX), i;
         char fd_buf[6+10];
         char br_buf[6+IFNAMSIZ] = {0};
+        char ifname_buf[9+IFNAMSIZ] = {0};
         char helper_cmd[PATH_MAX + sizeof(fd_buf) + sizeof(br_buf) + 15];
 
         for (i = 0; i < open_max; i++) {
@@ -459,6 +460,10 @@ static int net_bridge_run_helper(const char *helper, const char *bridge)
 
         snprintf(fd_buf, sizeof(fd_buf), "%s%d", "--fd=", sv[1]);
 
+        if (ifname) {
+          snprintf(ifname_buf, sizeof(ifname_buf), "%s%s", "--ifname=", ifname);
+        }
+
         if (strrchr(helper, ' ') || strrchr(helper, '\t')) {
             /* assume helper is a command */
 
@@ -466,8 +471,8 @@ static int net_bridge_run_helper(const char *helper, const char *bridge)
                 snprintf(br_buf, sizeof(br_buf), "%s%s", "--br=", bridge);
             }
 
-            snprintf(helper_cmd, sizeof(helper_cmd), "%s %s %s %s",
-                     helper, "--use-vnet", fd_buf, br_buf);
+            snprintf(helper_cmd, sizeof(helper_cmd), "%s %s %s %s %s",
+                     helper, "--use-vnet", fd_buf, br_buf, ifname_buf);
 
             parg = args;
             *parg++ = (char *)"sh";
@@ -486,6 +491,7 @@ static int net_bridge_run_helper(const char *helper, const char *bridge)
             *parg++ = (char *)"--use-vnet";
             *parg++ = fd_buf;
             *parg++ = br_buf;
+            *parg++ = ifname_buf;
             *parg++ = NULL;
 
             execv(helper, args);
@@ -524,7 +530,7 @@ int net_init_bridge(const NetClientOptions *opts, const char *name,
                     NetClientState *peer)
 {
     const NetdevBridgeOptions *bridge;
-    const char *helper, *br;
+    const char *helper, *br, *ifname;
 
     TAPState *s;
     int fd, vnet_hdr;
@@ -534,8 +540,9 @@ int net_init_bridge(const NetClientOptions *opts, const char *name,
 
     helper = bridge->has_helper ? bridge->helper : DEFAULT_BRIDGE_HELPER;
     br     = bridge->has_br     ? bridge->br     : DEFAULT_BRIDGE_INTERFACE;
+    ifname = bridge->has_ifname ? bridge->ifname : DEFAULT_BRIDGE_IFNAME;
 
-    fd = net_bridge_run_helper(helper, br);
+    fd = net_bridge_run_helper(helper, br, ifname);
     if (fd == -1) {
         return -1;
     }
@@ -686,11 +693,12 @@ int net_init_tap(const NetClientOptions *opts, const char *name,
     const char *script = NULL; /* suppress wrong "uninit'd use" gcc warning */
     const char *downscript = NULL;
     const char *vhostfdname;
+    const char *br;
     char ifname[128];
 
     assert(opts->kind == NET_CLIENT_OPTIONS_KIND_TAP);
     tap = opts->tap;
-    queues = tap->has_queues ? tap->queues : 1;
+    queues      = tap->has_queues  ? tap->queues  : 1;
     vhostfdname = tap->has_vhostfd ? tap->vhostfd : NULL;
 
     /* QEMU vlans does not support multiqueue tap, in this case peer is set.
@@ -775,8 +783,7 @@ int net_init_tap(const NetClientOptions *opts, const char *name,
                          "queues=, and fds= are invalid with helper=");
             return -1;
         }
-
-        fd = net_bridge_run_helper(tap->helper, DEFAULT_BRIDGE_INTERFACE);
+        fd = net_bridge_run_helper(tap->helper, DEFAULT_BRIDGE_INTERFACE, NULL);
         if (fd == -1) {
             return -1;
         }
diff --git a/qapi-schema.json b/qapi-schema.json
index 088f4e1..be2373a 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -2676,6 +2676,7 @@
 { 'type': 'NetdevBridgeOptions',
   'data': {
     '*br':     'str',
+    '*ifname': 'str',
     '*helper': 'str' } }
 
 ##
diff --git a/qemu-bridge-helper.c b/qemu-bridge-helper.c
index 287bfd5..39486b1 100644
--- a/qemu-bridge-helper.c
+++ b/qemu-bridge-helper.c
@@ -67,7 +67,7 @@ typedef QSIMPLEQ_HEAD(ACLList, ACLRule) ACLList;
 static void usage(void)
 {
     fprintf(stderr,
-            "Usage: qemu-bridge-helper [--use-vnet] --br=bridge --fd=unixfd\n");
+            "Usage: qemu-bridge-helper [--use-vnet] [--ifname=name] --br=bridge --fd=unixfd\n");
 }
 
 static int parse_acl_file(const char *filename, ACLList *acl_list)
@@ -233,6 +233,7 @@ int main(int argc, char **argv)
     int use_vnet = 0;
     int mtu;
     const char *bridge = NULL;
+    const char *ifname = NULL;
     char iface[IFNAMSIZ];
     int index;
     ACLRule *acl_rule;
@@ -259,6 +260,8 @@ int main(int argc, char **argv)
             bridge = &argv[index][5];
         } else if (strncmp(argv[index], "--fd=", 5) == 0) {
             unixfd = atoi(&argv[index][5]);
+        } else if (strncmp(argv[index], "--ifname=", 9) == 0) {
+            ifname = &argv[index][9];
         } else {
             usage();
             return EXIT_FAILURE;
@@ -330,7 +333,12 @@ int main(int argc, char **argv)
 
     /* request a tap device, disable PI, and add vnet header support if
      * requested and it's available. */
-    prep_ifreq(&ifr, "tap%d");
+    if (ifname) {
+      /* prep_ifreq will truncate the name if it is too long */
+      prep_ifreq(&ifr, ifname);
+    } else {
+      prep_ifreq(&ifr, "tap%d");
+    }
     ifr.ifr_flags = IFF_TAP|IFF_NO_PI;
     if (use_vnet && has_vnet_hdr(fd)) {
         ifr.ifr_flags |= IFF_VNET_HDR;
diff --git a/qemu-options.hx b/qemu-options.hx
index d7afeab..dd49c6c 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1379,7 +1379,7 @@ DEF("net", HAS_ARG, QEMU_OPTION_net,
     "                use vhostforce=on to force vhost on for non-MSIX virtio guests\n"
     "                use 'vhostfd=h' to connect to an already opened vhost net device\n"
     "                use 'vhostfds=x:y:...:z to connect to multiple already opened vhost net devices\n"
-    "-net bridge[,vlan=n][,name=str][,br=bridge][,helper=helper]\n"
+    "-net bridge[,vlan=n][,name=str][,br=bridge][,helper=helper][,ifname=ifname]\n"
     "                connects a host TAP network interface to a host bridge device 'br'\n"
     "                (default=" DEFAULT_BRIDGE_INTERFACE ") using the program 'helper'\n"
     "                (default=" DEFAULT_BRIDGE_HELPER ")\n"
@@ -1621,7 +1621,7 @@ qemu-system-i386 linux.img \
                  -net nic -net tap,"helper=/usr/local/libexec/qemu-bridge-helper"
 @end example
 
-@item -netdev bridge,id=@var{id}[,br=@var{bridge}][,helper=@var{helper}]
+@item -netdev bridge,id=@var{id}[,br=@var{bridge}][,helper=@var{helper}][,ifname=@var{ifname}]
 @item -net bridge[,vlan=@var{n}][,name=@var{name}][,br=@var{bridge}][,helper=@var{helper}]
 Connect a host TAP network interface to a host bridge device.
 
@@ -1630,6 +1630,10 @@ attach it to the bridge. The default network helper executable is
 @file{/usr/local/libexec/qemu-bridge-helper} and the default bridge
 device is @file{br0}.
 
+The name of the host tap interface can be changed by @var{ifname} parameter.
+The default value is @file{tapX} where X is a number. The parameter --ifname
+will be passed to the helper if this option is used.
+
 Examples:
 
 @example
@@ -1644,6 +1648,16 @@ qemu-system-i386 linux.img -net bridge -net nic,model=virtio
 qemu-system-i386 linux.img -net bridge,br=qemubr0 -net nic,model=virtio
 @end example
 
+@example
+# Create two virtual interfaces, put them into different bridges
+# and give interfaces meaningful names.
+# PS intbr and extbr should be allowed in /etc/qemu/bridge.conf
+qemu-system-x86_64 --enable-kvm -m 512 -name virt \
+-device e1000,mac=52:54:DB:22:F9:7D,netdev=extbr -netdev bridge,id=extbr,br=extbr,ifname=virt_ext \
+-device e1000,mac=52:54:AC:8C:B6:6D,netdev=intbr -netdev bridge,id=intbr,br=intbr,ifname=virt_int \
+-drive file=/home/virtuals/virt.raw,if=virtio
+@end example
+
 @item -netdev socket,id=@var{id}[,fd=@var{h}][,listen=[@var{host}]:@var{port}][,connect=@var{host}:@var{port}]
 @item -net socket[,vlan=@var{n}][,name=@var{name}][,fd=@var{h}] [,listen=[@var{host}]:@var{port}][,connect=@var{host}:@var{port}]
 
-- 
1.8.2


--
Alexandre Kandalintsev