runqemu: Add network bridge support

Qemu supports attaching the virtual machine to an existing network
bridge interface via the qemu-bridge-helper program (as long as the
system is correctly configured to give the user permissions). Add
support for runqemu to do this also via the "bridge=<INTERFACE>"
argument. Note that for this to work correctly, the host
qemu-bridge-helper must be used, not the one that might have been built
by qemu-native. In order for qemu to correctly find this program, a
qemu-oe-bridge-helper program has been added to qemu-helper-native, and
runqemu will use this helper as the bridge helper. The helper will look
for the host qemu-bridge-helper first by looking in the
QEMU_BRIDGE_HELPER environment variable, then by search common paths
where the helper is installed.

(From OE-Core rev: 9e7b38c61c6b84b7f137c733ac5da9414025693d)

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/qemu/qemu-helper-native_1.0.bb

@@ -5,7 +5,10 @@ PR = "r1"
 
 LIC_FILES_CHKSUM = "file://${WORKDIR}/tunctl.c;endline=4;md5=ff3a09996bc5fff6bc5d4e0b4c28f999"
 
-SRC_URI = "file://tunctl.c"
+SRC_URI = "\
+    file://tunctl.c \
+    file://qemu-oe-bridge-helper \
+    "
 
 S = "${WORKDIR}"
 
@@ -18,6 +21,8 @@ do_compile() {
 do_install() {
 	install -d ${D}${bindir}
 	install tunctl ${D}${bindir}/
+
+    install -m 755 ${WORKDIR}/qemu-oe-bridge-helper ${D}${bindir}/
 }
 
 DEPENDS += "qemu-system-native"

meta/recipes-devtools/qemu/qemu-helper/qemu-oe-bridge-helper

@@ -0,0 +1,25 @@
+#! /bin/sh
+# Copyright 2020 Garmin Ltd. or its subsidiaries
+#
+# SPDX-License-Identifier: GPL-2.0
+#
+# Attempts to find and exec the host qemu-bridge-helper program
+
+# If the QEMU_BRIDGE_HELPER variable is set by the user, exec it.
+if [ -n "$QEMU_BRIDGE_HELPER" ]; then
+    exec "$QEMU_BRIDGE_HELPER" "$@"
+fi
+
+# Search common paths for the helper program
+BN="qemu-bridge-helper"
+PATHS="/usr/libexec/ /usr/lib/qemu/"
+
+for p in $PATHS; do
+    if [ -e "$p/$BN" ]; then
+        exec "$p/$BN" "$@"
+    fi
+done
+
+echo "$BN not found!" > /dev/stderr
+exit 1
+

scripts/runqemu

@@ -165,6 +165,7 @@ class BaseConfig(object):
         self.kvm_enabled = False
         self.vhost_enabled = False
         self.slirp_enabled = False
+        self.net_bridge = None
         self.nfs_instance = 0
         self.nfs_running = False
         self.serialconsole = False
@@ -485,6 +486,8 @@ class BaseConfig(object):
                 self.vhost_enabled = True
             elif arg == 'slirp':
                 self.slirp_enabled = True
+            elif arg.startswith('bridge='):
+                self.net_bridge = '%s' % arg[len('bridge='):]
             elif arg == 'snapshot':
                 self.snapshot = True
             elif arg == 'publicvnc':
@@ -802,7 +805,7 @@ class BaseConfig(object):
     def check_and_set(self):
         """Check configs sanity and set when needed"""
         self.validate_paths()
-        if not self.slirp_enabled:
+        if not self.slirp_enabled and not self.net_bridge:
             check_tun()
         # Check audio
         if self.audio_enabled:
@@ -1020,6 +1023,10 @@ class BaseConfig(object):
 
         self.nfs_running = True
 
+    def setup_net_bridge(self):
+        self.set('NETWORK_CMD', '-netdev bridge,br=%s,id=net0,helper=%s -device virtio-net-pci,netdev=net0 ' % (
+            self.net_bridge, os.path.join(self.bindir_native, 'qemu-oe-bridge-helper')))
+
     def setup_slirp(self):
         """Setup user networking"""
 
@@ -1161,7 +1168,9 @@ class BaseConfig(object):
         if sys.stdin.isatty():
             self.saved_stty = subprocess.check_output(("stty", "-g")).decode('utf-8').strip()
         self.network_device = self.get('QB_NETWORK_DEVICE') or self.network_device
-        if self.slirp_enabled:
+        if self.net_bridge:
+            self.setup_net_bridge()
+        elif self.slirp_enabled:
             self.setup_slirp()
         else:
             self.setup_tap()