SmartNIC DPUs may not expose some privileged eswitch operations to the hypervisor hosts. For example, this happens with Bluefield devices running in the ECPF (default) mode for security reasons. While VF MAC address programming is possible via an RTM_SETLINK operation, trying to set a VLAN ID in the same operation will fail with EPERM. The equivalent ip link commands below provide an illustration: 1. This works: sudo ip link set enp130s0f0 vf 2 mac de:ad:be:ef:ca:fe 2. Setting (or clearing) a VLAN fails with EPERM: sudo ip link set enp130s0f0 vf 2 vlan 0 RTNETLINK answers: Operation not permitted 3. This is what Libvirt attempts to do today (when trying to clear a VF VLAN at the same time as programming a VF MAC). sudo ip link set enp130s0f0 vf 2 vlan 0 mac de:ad:be:ef:ca:fe RTNETLINK answers: Operation not permitted If setting an explicit VLAN ID results in an EPERM, clearing a VLAN (setting a VLAN ID to 0) can be handled gracefully by ignoring the EPERM error with the rationale being that if we cannot set this state in the first place, we cannot clear it either. Thus, virNetDevSetVfConfig is split into two distinct functions. If clearing a VLAN ID fails with EPERM, the error is simply ignored. Both new functions rely virNetDevSendVfSetLinkRequest that implements common functionality related to formatting a request, sending it and handling error conditions and returns 0 or an error since in both cases the payload is either NLMSG_DONE (no error) or NLMSG_ERROR where an error message is needed by the caller to handle known cases appropriately. This function allows the conditional code to be unit tested. An alternative to this could be providing a higher level control plane mechanism that would provide metadata about a device being remotely managed in which case Libvirt would avoid trying to set or clear a VLAN ID. This would be more complicated since other software (like Nova in the OpenStack case) would have to annotate every guest device with an attribute indicating whether a device is remotely managed or not based on operator provided configuration so that Libvirt can act on this and avoid VLAN programming. Signed-off-by: Dmitrii Shcherbakov <dmitrii.shcherbakov(a)canonical.com&gt; --- NEWS.rst | 9 ++ src/libvirt_private.syms | 7 ++ src/util/virnetdev.c | 196 +++++++++++++++++++++------------- src/util/virnetdevpriv.h | 44 ++++++++ tests/virnetdevtest.c | 222 ++++++++++++++++++++++++++++++++++++++- 5 files changed, 405 insertions(+), 73 deletions(-) create mode 100644 src/util/virnetdevpriv.h diff --git a/NEWS.rst b/NEWS.rst index a71b84c363..d1702d95d5 100644 --- a/NEWS.rst +++ b/NEWS.rst @@ -30,6 +30,15 @@ v7.10.0 (unreleased) Libvirt is now able to report interface information from the guest's perspective (using guest agent). + * virnetdev: Ignore EPERM on attempts to clear VF VLAN ID + + Libvirt will now ignore EPERM errors on attempts to clear a VLAN ID as + SmartNIC DPUs do not expose VLAN programming capabilities to the + hypervisor host. Libvirt tries to clear a VLAN in the same operation + as setting a MAC address for VIR_DOMAIN_NET_TYPE_HOSTDEV devices which + is now split into two distinct operations. EPERM errors received while + trying to program a non-zero VLAN ID will still cause errors. + * **Bug fixes** diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms index 9ee8fda25f..4b8e3e2b15 100644 --- a/src/libvirt_private.syms +++ b/src/libvirt_private.syms @@ -2851,6 +2851,13 @@ virNetDevOpenvswitchSetTimeout; virNetDevOpenvswitchUpdateVlan; +#util/virnetdevpriv.h +virNetDevSendVfSetLinkRequest; +virNetDevSetVfConfig; +virNetDevSetVfMac; +virNetDevSetVfVlan; + + # util/virnetdevtap.h virNetDevTapAttachBridge; virNetDevTapCreate; diff --git a/src/util/virnetdev.c b/src/util/virnetdev.c index 58f7360a0f..5daec532b4 100644 --- a/src/util/virnetdev.c +++ b/src/util/virnetdev.c @@ -19,7 +19,9 @@ #include <config.h> #include <math.h> -#include "virnetdev.h" +#define LIBVIRT_VIRNETDEVPRIV_H_ALLOW + +#include "virnetdevpriv.h" #include "viralloc.h" #include "virnetlink.h" #include "virmacaddr.h" @@ -1527,16 +1529,12 @@ static struct nla_policy ifla_vfstats_policy[IFLA_VF_STATS_MAX+1] = { [IFLA_VF_STATS_MULTICAST] = { .type = NLA_U64 }, }; - -static int -virNetDevSetVfConfig(const char *ifname, int vf, - const virMacAddr *macaddr, int vlanid, - bool *allowRetry) +int +virNetDevSendVfSetLinkRequest(const char *ifname, int vfInfoType, + const void *payload, const size_t payloadLen) { - int rc = -1; - char macstr[VIR_MAC_STRING_BUFLEN]; g_autofree struct nlmsghdr *resp = NULL; - struct nlmsgerr *err; + struct nlmsgerr *err = NULL; unsigned int recvbuflen = 0; struct nl_msg *nl_msg; struct nlattr *vfinfolist, *vfinfo; @@ -1544,9 +1542,11 @@ virNetDevSetVfConfig(const char *ifname, int vf, .ifi_family = AF_UNSPEC, .ifi_index = -1, }; + int rc = 0; - if (!macaddr && vlanid < 0) + if (payload == NULL || payloadLen == 0) { return -1; + } nl_msg = virNetlinkMsgNew(RTM_SETLINK, NLM_F_REQUEST); @@ -1564,30 +1564,8 @@ virNetDevSetVfConfig(const char *ifname, int vf, if (!(vfinfo = nla_nest_start(nl_msg, IFLA_VF_INFO))) goto buffer_too_small; - if (macaddr) { - struct ifla_vf_mac ifla_vf_mac = { - .vf = vf, - .mac = { 0, }, - }; - - virMacAddrGetRaw(macaddr, ifla_vf_mac.mac); - - if (nla_put(nl_msg, IFLA_VF_MAC, sizeof(ifla_vf_mac), - &ifla_vf_mac) < 0) - goto buffer_too_small; - } - - if (vlanid >= 0) { - struct ifla_vf_vlan ifla_vf_vlan = { - .vf = vf, - .vlan = vlanid, - .qos = 0, - }; - - if (nla_put(nl_msg, IFLA_VF_VLAN, sizeof(ifla_vf_vlan), - &ifla_vf_vlan) < 0) - goto buffer_too_small; - } + if (nla_put(nl_msg, vfInfoType, payloadLen, payload) < 0) + goto buffer_too_small; nla_nest_end(nl_msg, vfinfo); nla_nest_end(nl_msg, vfinfolist); @@ -1600,48 +1578,20 @@ virNetDevSetVfConfig(const char *ifname, int vf, goto malformed_resp; switch (resp->nlmsg_type) { - case NLMSG_ERROR: - err = (struct nlmsgerr *)NLMSG_DATA(resp); - if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err))) + case NLMSG_ERROR: + err = (struct nlmsgerr *)NLMSG_DATA(resp); + if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err))) + goto malformed_resp; + rc = err->error; + break; + case NLMSG_DONE: + rc = 0; + break; + default: goto malformed_resp; - - /* if allowRetry is true and the error was EINVAL, then - * silently return a failure so the caller can retry with a - * different MAC address - */ - if (err->error == -EINVAL && *allowRetry && - macaddr && !virMacAddrCmp(macaddr, &zeroMAC)) { - goto cleanup; - } else if (err->error) { - /* other errors are permanent */ - virReportSystemError(-err->error, - _("Cannot set interface MAC/vlanid to %s/%d " - "for ifname %s vf %d"), - (macaddr - ? virMacAddrFormat(macaddr, macstr) - : "(unchanged)"), - vlanid, - ifname ? ifname : "(unspecified)", - vf); - *allowRetry = false; /* no use retrying */ - goto cleanup; - } - break; - - case NLMSG_DONE: - break; - - default: - goto malformed_resp; } - rc = 0; cleanup: - VIR_DEBUG("RTM_SETLINK %s vf %d MAC=%s vlanid=%d - %s", - ifname, vf, - macaddr ? virMacAddrFormat(macaddr, macstr) : "(unchanged)", - vlanid, rc < 0 ? "Fail" : "Success"); - nlmsg_free(nl_msg); return rc; @@ -1656,6 +1606,108 @@ virNetDevSetVfConfig(const char *ifname, int vf, goto cleanup; } +int +virNetDevSetVfVlan(const char *ifname, int vf, int vlanid) +{ + int rc = -1; + int requestError = 0; + + struct ifla_vf_vlan ifla_vf_vlan = { + .vf = vf, + .vlan = vlanid, + .qos = 0, + }; + + /* VLAN ids 0 and 4095 are reserved per 802.1Q but are valid values. */ + if (vlanid < 0 || vlanid > 4095) + return -1; + + requestError = virNetDevSendVfSetLinkRequest(ifname, IFLA_VF_VLAN, + &ifla_vf_vlan, sizeof(ifla_vf_vlan)); + + /* If vlanid is 0 - we are attempting to clear an existing VLAN id. + * An EPERM received at this stage is an indicator that the embedded + * switch is not exposed to this host and the network driver is not + * able to set a VLAN for a VF. */ + if (requestError == -EPERM && vlanid == 0) { + rc = 0; + } else if (requestError) { + virReportSystemError(-requestError, + _("Cannot set interface vlanid to %d " + "for ifname %s vf %d"), + vlanid, ifname ? ifname : "(unspecified)", vf); + rc = -1; + } else { + rc = 0; + } + VIR_DEBUG("RTM_SETLINK %s vf %d vlanid=%d - %s", + ifname, vf, + vlanid, rc < 0 ? "Fail" : "Success"); + return rc; +} + +int +virNetDevSetVfMac(const char *ifname, int vf, + const virMacAddr *macaddr, + bool *allowRetry) +{ + int rc = 0; + int requestError = 0; + char macstr[VIR_MAC_STRING_BUFLEN]; + + struct ifla_vf_mac ifla_vf_mac = { + .vf = vf, + .mac = { 0, }, + }; + + if (macaddr == NULL || allowRetry == NULL) + return -1; + + virMacAddrGetRaw(macaddr, ifla_vf_mac.mac); + + requestError = virNetDevSendVfSetLinkRequest(ifname, IFLA_VF_MAC, + &ifla_vf_mac, sizeof(ifla_vf_mac)); + /* if allowRetry is true and the error was EINVAL, then + * silently return a failure so the caller can retry with a + * different MAC address. */ + if (requestError == -EINVAL && *allowRetry && !virMacAddrCmp(macaddr, &zeroMAC)) { + rc = -2; + } else if (requestError) { + /* other errors are permanent */ + virReportSystemError(-requestError, + _("Cannot set interface MAC to %s " + "for ifname %s vf %d"), + (macaddr + ? virMacAddrFormat(macaddr, macstr) + : "(unchanged)"), + ifname ? ifname : "(unspecified)", + vf); + *allowRetry = false; /* no use retrying */ + rc = -1; + } else { + rc = 0; + } + VIR_DEBUG("RTM_SETLINK %s vf %d MAC=%s - %s", + ifname, vf, + macaddr ? virMacAddrFormat(macaddr, macstr) : "(unchanged)", + rc < 0 ? "Fail" : "Success"); + return rc; +} + +int +virNetDevSetVfConfig(const char *ifname, int vf, + const virMacAddr *macaddr, int vlanid, + bool *allowRetry) +{ + int rc = 0; + if ((rc = virNetDevSetVfMac(ifname, vf, macaddr, allowRetry)) < 0) { + return rc; + } else if ((rc = virNetDevSetVfVlan(ifname, vf, vlanid)) < 0) { + return rc; + } + return rc; +} + /** * virNetDevParseVfInfo: * Get the VF interface information from kernel by netlink, To make netlink diff --git a/src/util/virnetdevpriv.h b/src/util/virnetdevpriv.h new file mode 100644 index 0000000000..7990bf5269 --- /dev/null +++ b/src/util/virnetdevpriv.h @@ -0,0 +1,44 @@ +/* + * virnetdevpriv.h: private virnetdev header for unit testing + * + * Copyright (C) 2021 Canonical Ltd. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; If not, see + * <http://www.gnu.org/licenses/>;. + */ + +#ifndef LIBVIRT_VIRNETDEVPRIV_H_ALLOW +# error "virnetdevpriv.h may only be included by virnetdev.c or test suites" +#endif /* LIBVIRT_VIRNETDEVPRIV_H_ALLOW */ + +#pragma once + +#include "virnetdev.h" + +int +virNetDevSendVfSetLinkRequest(const char *ifname, int vfInfoType, + const void *payload, const size_t payloadLen); + +int +virNetDevSetVfVlan(const char *ifname, int vf, int vlanid); + +int +virNetDevSetVfMac(const char *ifname, int vf, + const virMacAddr *macaddr, + bool *allowRetry); + +int +virNetDevSetVfConfig(const char *ifname, int vf, + const virMacAddr *macaddr, int vlanid, + bool *allowRetry); diff --git a/tests/virnetdevtest.c b/tests/virnetdevtest.c index aadbeb1ef4..bdaa94e83c 100644 --- a/tests/virnetdevtest.c +++ b/tests/virnetdevtest.c @@ -18,11 +18,17 @@ #include <config.h> +#include "internal.h" #include "testutils.h" +#include "virnetlink.h" + +#define LIBVIRT_VIRNETDEVPRIV_H_ALLOW + #ifdef __linux__ -# include "virnetdev.h" +# include "virmock.h" +# include "virnetdevpriv.h" # define VIR_FROM_THIS VIR_FROM_NONE @@ -59,6 +65,211 @@ testVirNetDevGetLinkInfo(const void *opaque) return 0; } +int +(*real_virNetDevSendVfSetLinkRequest)(const char *ifname, int vfInfoType, + const void *payload, const size_t payloadLen); + +int +(*real_virNetDevSetVfMac)(const char *ifname, int vf, const virMacAddr *macaddr, bool *allowRetry); + +int +(*real_virNetDevSetVfVlan)(const char *ifname, int vf, int vlanid); + +static void +init_syms(void) +{ + VIR_MOCK_REAL_INIT(virNetDevSendVfSetLinkRequest); + VIR_MOCK_REAL_INIT(virNetDevSetVfMac); + VIR_MOCK_REAL_INIT(virNetDevSetVfVlan); +} + +int +virNetDevSetVfMac(const char *ifname, int vf, + const virMacAddr *macaddr, + bool *allowRetry) +{ + init_syms(); + + if (STREQ_NULLABLE(ifname, "fakeiface-macerror")) { + return -1; + } else if (STREQ_NULLABLE(ifname, "fakeiface-altmacerror")) { + return -2; + } else if (STREQ_NULLABLE(ifname, "fakeiface-macerror-novlanerror")) { + return -1; + } else if (STREQ_NULLABLE(ifname, "fakeiface-macerror-vlanerror")) { + return -1; + } else if (STREQ_NULLABLE(ifname, "fakeiface-nomacerror-novlanerror")) { + return 0; + } + return real_virNetDevSetVfMac(ifname, vf, macaddr, allowRetry); +} + +int +virNetDevSetVfVlan(const char *ifname, int vf, int vlanid) +{ + init_syms(); + + if (STREQ_NULLABLE(ifname, "fakeiface-macerror-vlanerror")) { + return -1; + } else if (STREQ_NULLABLE(ifname, "fakeiface-macerror-novlanerror")) { + return 0; + } else if (STREQ_NULLABLE(ifname, "fakeiface-nomacerror-novlanerror")) { + return 0; + } + return real_virNetDevSetVfVlan(ifname, vf, vlanid); +} + +int +virNetDevSendVfSetLinkRequest(const char *ifname, int vfInfoType, + const void *payload, const size_t payloadLen) +{ + init_syms(); + + if (STREQ_NULLABLE(ifname, "fakeiface-eperm")) { + return -EPERM; + } else if (STREQ_NULLABLE(ifname, "fakeiface-eagain")) { + return -EAGAIN; + } else if (STREQ_NULLABLE(ifname, "fakeiface-einval")) { + return -EINVAL; + } else if (STREQ_NULLABLE(ifname, "fakeiface-ok")) { + return 0; + } + return real_virNetDevSendVfSetLinkRequest(ifname, vfInfoType, payload, payloadLen); +} + +static int +testVirNetDevSetVfMac(const void *opaque G_GNUC_UNUSED) +{ + struct testCase { + const char *ifname; + const int vf_num; + const virMacAddr macaddr; + bool allow_retry; + const int rc; + }; + size_t i = 0; + int rc = 0; + struct testCase testCases[] = { + { .ifname = "fakeiface-ok", .vf_num = 1, + .macaddr = { .addr = { 0, 0, 0, 0, 0, 0 } }, .allow_retry = false, .rc = 0 }, + { .ifname = "fakeiface-ok", .vf_num = 2, + .macaddr = { .addr = { 0, 0, 0, 7, 7, 7 } }, .allow_retry = false, .rc = 0 }, + { .ifname = "fakeiface-ok", .vf_num = 3, + .macaddr = { .addr = { 0, 0, 0, 0, 0, 0 } }, .allow_retry = true, .rc = 0 }, + { .ifname = "fakeiface-ok", .vf_num = 4, + .macaddr = { .addr = { 0, 0, 0, 7, 7, 7 } }, .allow_retry = true, .rc = 0 }, + { .ifname = "fakeiface-eperm", .vf_num = 5, + .macaddr = { .addr = { 0, 0, 0, 0, 0, 0 } }, .allow_retry = false, .rc = -1 }, + { .ifname = "fakeiface-einval", .vf_num = 6, + .macaddr = { .addr = { 0, 0, 0, 0, 0, 0 } }, .allow_retry = false, .rc = -1 }, + { .ifname = "fakeiface-einval", .vf_num = 7, + .macaddr = { .addr = { 0, 0, 0, 0, 0, 0 } }, .allow_retry = true, .rc = -2 }, + { .ifname = "fakeiface-einval", .vf_num = 8, + .macaddr = { .addr = { 0, 0, 0, 7, 7, 7 } }, .allow_retry = false, .rc = -1 }, + { .ifname = "fakeiface-einval", .vf_num = 9, + .macaddr = { .addr = { 0, 0, 0, 7, 7, 7 } }, .allow_retry = true, .rc = -1 }, + }; + + for (i = 0; i < sizeof(testCases) / sizeof(struct testCase); ++i) { + rc = virNetDevSetVfMac(testCases[i].ifname, testCases[i].vf_num, + &testCases[i].macaddr, &testCases[i].allow_retry); + if (rc != testCases[i].rc) { + return -1; + } + } + return 0; +} + +static int +testVirNetDevSetVfMissingMac(const void *opaque G_GNUC_UNUSED) +{ + bool allowRetry = false; + /* NULL MAC pointer. */ + if (virNetDevSetVfMac("fakeiface-ok", 1, NULL, &allowRetry) != -1) { + return -1; + } + allowRetry = true; + if (virNetDevSetVfMac("fakeiface-ok", 1, NULL, &allowRetry) != -1) { + return -1; + } + return 0; +} + +static int +testVirNetDevSetVfVlan(const void *opaque G_GNUC_UNUSED) +{ + struct testCase { + const char *ifname; + const int vf_num; + const int vlan_id; + const int rc; + }; + size_t i = 0; + int rc = 0; + const struct testCase testCases[] = { + /* VLAN ID is out of range of valid values (0-4095). */ + { .ifname = "enxdeadbeefcafe", .vf_num = 1, .vlan_id = 4096, .rc = -1 }, + { .ifname = "enxdeadbeefcafe", .vf_num = 1, .vlan_id = -1, .rc = -1 }, + /* Requests with vlan id 0 (trying to clear a VLAN that return EPERM should + * not result in an error. They simply need to be ignored because it may + * indicate that the NIC switch functionality is not exposed to the host. */ + { .ifname = "fakeiface-eperm", .vf_num = 1, .vlan_id = 0, .rc = 0 }, + /* Requests with vlan id 0 with an error output different from EPERM are failures. */ + { .ifname = "fakeiface-eagain", .vf_num = 1, .vlan_id = 0, .rc = -1 }, + /* Successful requests with vlan id 0 need to have a zero return code. */ + { .ifname = "fakeiface-ok", .vf_num = 1, .vlan_id = 0, .rc = 0 }, + /* Requests with a non-zero VLAN ID that result in an EPERM need to result in failures. + * failures. */ + { .ifname = "fakeiface-eperm", .vf_num = 1, .vlan_id = 42, .rc = -1 }, + /* Requests with a non-zero VLAN ID that result in some other errors need to result in + * failures. */ + { .ifname = "fakeiface-eagain", .vf_num = 1, .vlan_id = 42, .rc = -1 }, + /* Successful requests with a non-zero VLAN ID */ + { .ifname = "fakeiface-ok", .vf_num = 1, .vlan_id = 42, .rc = 0 }, + }; + + for (i = 0; i < sizeof(testCases) / sizeof(struct testCase); ++i) { + rc = virNetDevSetVfVlan(testCases[i].ifname, testCases[i].vf_num, testCases[i].vlan_id); + if (rc != testCases[i].rc) { + return -1; + } + } + + return 0; +} + +static int +testVirNetDevSetVfConfig(const void *opaque G_GNUC_UNUSED) +{ + struct testCase { + const char *ifname; + const int rc; + }; + int rc = 0; + size_t i = 0; + /* Nested functions are mocked so dummy values are used. */ + const virMacAddr mac = { .addr = { 0xDE, 0xAD, 0xBE, 0xEF, 0xCA, 0xFE }}; + const int vfNum = 1; + const int vlanid = 0; + bool *allowRetry = NULL; + + const struct testCase testCases[] = { + { .ifname = "fakeiface-macerror", .rc = -1 }, + { .ifname = "fakeiface-altmacerror", .rc = -2 }, + { .ifname = "fakeiface-macerror-novlanerror", .rc = -1 }, + { .ifname = "fakeiface-macerror-vlanerror", .rc = -1 }, + { .ifname = "fakeiface-nomacerror-novlanerror", .rc = 0 }, + }; + + for (i = 0; i < sizeof(testCases) / sizeof(struct testCase); ++i) { + rc = virNetDevSetVfConfig(testCases[i].ifname, vfNum, &mac, vlanid, allowRetry); + if (rc != testCases[i].rc) { + return -1; + } + } + return 0; +} + static int mymain(void) { @@ -76,6 +287,15 @@ mymain(void) DO_TEST_LINK("lo", VIR_NETDEV_IF_STATE_UNKNOWN, 0); DO_TEST_LINK("eth0-broken", VIR_NETDEV_IF_STATE_DOWN, 0); + if (virTestRun("Set VF MAC", testVirNetDevSetVfMac, NULL) < 0) + ret = -1; + if (virTestRun("Set VF MAC: missing MAC pointer", testVirNetDevSetVfMissingMac, NULL) < 0) + ret = -1; + if (virTestRun("Set VF VLAN", testVirNetDevSetVfVlan, NULL) < 0) + ret = -1; + if (virTestRun("Set VF Config", testVirNetDevSetVfConfig, NULL) < 0) + ret = -1; + return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE; } -- 2.32.0

Hi Laine, This is less effective than mocking netlink messages, however, even with netlink messages responses would depend on providing the right argument to trigger the right mock. Even this testing was useful because I managed to make a mistake while reworking one of the if statements and those tests at least trigger the conditionals that check error codes. As far as ideas go: 1. I could suggest returning the requestError coming from virNetDevSendVfSetLinkRequest - so if there is a mistake in the mock argument, the resulting error will be different from the one expected in a test since there won't be a netdev on a system with a test name and the real implementation of virNetDevSendVfSetLinkRequest will be called. 2. Utilize netdevsim https://github.com/torvalds/linux/blob/v5.15/drivers/net/netdevsim/netdev... Downsides: * having to load the right kernel module (testing in docker containers makes it difficult - I don't see any infrastructure in the current test framework to do that); * cannot test the EPERM case since nsim_set_vf_vlan does not return it (it actually allows setting a VLAN for a simulated VF). On the plus side, this doesn't require mocking netlink messages and utilizes the netlink message sending/receiving infrastructure in Libvirt in full. 3. Introduce netlink message mocking. There will be some boilerplate to generate kernel-like responses or at least partial messages that contain an error or lack thereof (NLMSG_DONE, NLMSG_ERROR). I'll start with (1) for now but I am open to discussing other approaches further. I am certainly interested in having this tested on every build so that it doesn't break for everybody else down the road. Best Regards, Dmitrii Shcherbakov LP/oftc: dmitriis On Wed, Nov 17, 2021 at 3:43 AM Laine Stump <laine(a)redhat.com&gt; wrote: