From 7cd0911e1a6c1b1cfe57c6e375077c689424a009 Mon Sep 17 00:00:00 2001 From: Laine Stump Date: Mon, 26 Aug 2019 00:24:34 -0400 Subject: [PATCH] qemu: support unmanaged target tap dev for MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit If managed='no', then the tap device must already exist, and setting of MAC address and online status (IFF_UP) is skipped. NB: we still set IFF_VNET_HDR and IFF_MULTI_QUEUE as appropriate, because those bits must be properly set in the TUNSETIFF we use to set the tap device name of the handle we've opened - if IFF_VNET_HDR has not been set and we set it the request will be honored even when running libvirtd unprivileged; if IFF_MULTI_QUEUE is requested to be different than how it was created, that will result in an error from the kernel. This means that you don't need to pay attention to IFF_VNET_HDR when creating the tap devices, but you *do* need to set IFF_MULTI_QUEUE if you're going to use multiple queues for your tap device. NB2: /dev/vhost-net normally has permissions 600, so it can't be opened by an unprivileged process. This would normally cause a warning message when using a virtio net device from an unprivileged libvirtd. I've found that setting the permissions for /dev/vhost-net permits unprivileged libvirtd to use vhost-net for virtio devices, but have no idea what sort of security implications that has. I haven't changed libvrit's code to avoid *attempting* to open /dev/vhost-net - if you are concerned about the security of opening up permissions of /dev/vhost-net (probably a good idea at least until we ask someone who knows about the code) then add to the interface definition and you'll avoid the warning message. Note that virNetDevTapCreate() is the correct function to call in the case of an existing device, because the same ioctl() that creates a new tap device will also open an existing tap device. Resolves: https://bugzilla.redhat.com/1723367 (partially) Signed-off-by: Laine Stump Reviewed-by: Daniel P. Berrangé --- src/qemu/qemu_interface.c | 69 ++++++++++++------- src/qemu/qemu_process.c | 2 +- src/util/virnetdev.h | 2 +- .../net-eth-unmanaged-tap.args | 32 +++++++++ tests/qemuxml2argvmock.c | 16 ++++- tests/qemuxml2argvtest.c | 1 + 6 files changed, 92 insertions(+), 30 deletions(-) create mode 100644 tests/qemuxml2argvdata/net-eth-unmanaged-tap.args diff --git a/src/qemu/qemu_interface.c b/src/qemu/qemu_interface.c index ad1755dd6a..b82a62f7d3 100644 --- a/src/qemu/qemu_interface.c +++ b/src/qemu/qemu_interface.c @@ -428,36 +428,53 @@ qemuInterfaceEthernetConnect(virDomainDefPtr def, if (virDomainNetIsVirtioModel(net)) tap_create_flags |= VIR_NETDEV_TAP_CREATE_VNET_HDR; - if (!net->ifname || - STRPREFIX(net->ifname, VIR_NET_GENERATED_TAP_PREFIX) || - strchr(net->ifname, '%')) { - VIR_FREE(net->ifname); - if (VIR_STRDUP(net->ifname, VIR_NET_GENERATED_TAP_PREFIX "%d") < 0) + if (net->managed_tap == VIR_TRISTATE_BOOL_NO) { + if (!net->ifname) { + virReportError(VIR_ERR_INTERNAL_ERROR, "%s", + _("target dev must be supplied when managed='no'")); goto cleanup; - /* avoid exposing vnet%d in getXMLDesc or error outputs */ - template_ifname = true; - } - if (virNetDevTapCreate(&net->ifname, tunpath, tapfd, tapfdSize, - tap_create_flags) < 0) { - goto cleanup; - } + } + if (virNetDevExists(net->ifname) != 1) { + virReportError(VIR_ERR_INTERNAL_ERROR, "%s", + _("target managed='no' but specified dev doesn't exist")); + goto cleanup; + } + if (virNetDevTapCreate(&net->ifname, tunpath, tapfd, tapfdSize, + tap_create_flags) < 0) { + goto cleanup; + } + } else { + if (!net->ifname || + STRPREFIX(net->ifname, VIR_NET_GENERATED_TAP_PREFIX) || + strchr(net->ifname, '%')) { + VIR_FREE(net->ifname); + if (VIR_STRDUP(net->ifname, VIR_NET_GENERATED_TAP_PREFIX "%d") < 0) + goto cleanup; + /* avoid exposing vnet%d in getXMLDesc or error outputs */ + template_ifname = true; + } + if (virNetDevTapCreate(&net->ifname, tunpath, tapfd, tapfdSize, + tap_create_flags) < 0) { + goto cleanup; + } - /* The tap device's MAC address cannot match the MAC address - * used by the guest. This results in "received packet on - * vnetX with own address as source address" error logs from - * the kernel. - */ - virMacAddrSet(&tapmac, &net->mac); - if (tapmac.addr[0] == 0xFE) - tapmac.addr[0] = 0xFA; - else - tapmac.addr[0] = 0xFE; + /* The tap device's MAC address cannot match the MAC address + * used by the guest. This results in "received packet on + * vnetX with own address as source address" error logs from + * the kernel. + */ + virMacAddrSet(&tapmac, &net->mac); + if (tapmac.addr[0] == 0xFE) + tapmac.addr[0] = 0xFA; + else + tapmac.addr[0] = 0xFE; - if (virNetDevSetMAC(net->ifname, &tapmac) < 0) - goto cleanup; + if (virNetDevSetMAC(net->ifname, &tapmac) < 0) + goto cleanup; - if (virNetDevSetOnline(net->ifname, true) < 0) - goto cleanup; + if (virNetDevSetOnline(net->ifname, true) < 0) + goto cleanup; + } if (net->script && virNetDevRunEthernetScript(net->ifname, net->script) < 0) diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c index 6a261786f9..955ba4de4c 100644 --- a/src/qemu/qemu_process.c +++ b/src/qemu/qemu_process.c @@ -7559,7 +7559,7 @@ void qemuProcessStop(virQEMUDriverPtr driver, cfg->stateDir)); break; case VIR_DOMAIN_NET_TYPE_ETHERNET: - if (net->ifname) { + if (net->managed_tap != VIR_TRISTATE_BOOL_NO && net->ifname) { ignore_value(virNetDevTapDelete(net->ifname, net->backend.tap)); VIR_FREE(net->ifname); } diff --git a/src/util/virnetdev.h b/src/util/virnetdev.h index 563b218227..6ff98487cb 100644 --- a/src/util/virnetdev.h +++ b/src/util/virnetdev.h @@ -150,7 +150,7 @@ int virNetDevSetupControl(const char *ifname, ATTRIBUTE_RETURN_CHECK; int virNetDevExists(const char *brname) - ATTRIBUTE_NONNULL(1) ATTRIBUTE_RETURN_CHECK; + ATTRIBUTE_NONNULL(1) ATTRIBUTE_RETURN_CHECK ATTRIBUTE_NOINLINE; int virNetDevSetOnline(const char *ifname, bool online) diff --git a/tests/qemuxml2argvdata/net-eth-unmanaged-tap.args b/tests/qemuxml2argvdata/net-eth-unmanaged-tap.args new file mode 100644 index 0000000000..2bb99e96da --- /dev/null +++ b/tests/qemuxml2argvdata/net-eth-unmanaged-tap.args @@ -0,0 +1,32 @@ +LC_ALL=C \ +PATH=/bin \ +HOME=/tmp/lib/domain--1-QEMUGuest1 \ +USER=test \ +LOGNAME=test \ +XDG_DATA_HOME=/tmp/lib/domain--1-QEMUGuest1/.local/share \ +XDG_CACHE_HOME=/tmp/lib/domain--1-QEMUGuest1/.cache \ +XDG_CONFIG_HOME=/tmp/lib/domain--1-QEMUGuest1/.config \ +QEMU_AUDIO_DRV=none \ +/usr/bin/qemu-system-i686 \ +-name QEMUGuest1 \ +-S \ +-machine pc,accel=tcg,usb=off,dump-guest-core=off \ +-m 214 \ +-realtime mlock=off \ +-smp 1,sockets=1,cores=1,threads=1 \ +-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \ +-display none \ +-no-user-config \ +-nodefaults \ +-chardev socket,id=charmonitor,path=/tmp/lib/domain--1-QEMUGuest1/monitor.sock,\ +server,nowait \ +-mon chardev=charmonitor,id=monitor,mode=control \ +-rtc base=utc \ +-no-shutdown \ +-no-acpi \ +-usb \ +-drive file=/dev/HostVG/QEMUGuest1,format=raw,if=none,id=drive-ide0-0-0 \ +-device ide-hd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1 \ +-netdev tap,fd=3,id=hostnet0,vhost=on,vhostfd=44 \ +-device virtio-net-pci,netdev=hostnet0,id=net0,mac=fe:11:22:33:44:55,bus=pci.0,\ +addr=0x3 diff --git a/tests/qemuxml2argvmock.c b/tests/qemuxml2argvmock.c index 3f0c1c3fef..a386dd17be 100644 --- a/tests/qemuxml2argvmock.c +++ b/tests/qemuxml2argvmock.c @@ -149,8 +149,12 @@ virNetDevTapCreate(char **ifname, for (i = 0; i < tapfdSize; i++) tapfd[i] = STDERR_FILENO + 1 + i; - VIR_FREE(*ifname); - return VIR_STRDUP(*ifname, "vnet0"); + if (STREQ_NULLABLE(*ifname, "mytap0")) { + return 0; + } else { + VIR_FREE(*ifname); + return VIR_STRDUP(*ifname, "vnet0"); + } } int @@ -160,6 +164,14 @@ virNetDevSetMAC(const char *ifname ATTRIBUTE_UNUSED, return 0; } + +int +virNetDevExists(const char *ifname) +{ + return STREQ_NULLABLE(ifname, "mytap0"); +} + + int virNetDevIPAddrAdd(const char *ifname ATTRIBUTE_UNUSED, virSocketAddr *addr ATTRIBUTE_UNUSED, virSocketAddr *peer ATTRIBUTE_UNUSED, diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c index 5af74ef9be..1f2ae5958a 100644 --- a/tests/qemuxml2argvtest.c +++ b/tests/qemuxml2argvtest.c @@ -1318,6 +1318,7 @@ mymain(void) DO_TEST("net-eth-ifname", NONE); DO_TEST("net-eth-names", NONE); DO_TEST("net-eth-hostip", NONE); + DO_TEST("net-eth-unmanaged-tap", NONE); DO_TEST("net-client", NONE); DO_TEST("net-server", NONE); DO_TEST("net-many-models", NONE); -- GitLab