From 458aa8587e750e7b368e1a86208841a082242ce5 Mon Sep 17 00:00:00 2001

Message-Id: <458aa8587e750e7b368e1a86208841a082242ce5@dist-git>

From: Laine Stump <laine@laine.org>

Date: Thu, 13 Apr 2017 14:29:36 -0400

Subject: [PATCH] util: if setting admin MAC to 00:00:00:00:00:00 fails, try

 02:00:00:00:00:00

Some PF drivers allow setting the admin MAC (that is the MAC address

that the VF will be initialized to the next time the VF's driver is

loaded) to 00:00:00:00:00:00, and some don't. Multiple drivers

initialize the admin MACs to all 0, but don't allow setting it to that

very same value. It has been an uphill battle convincing the driver

people that it's reasonable to expect The argument that's used is

that an all 0 device MAC address on a device is invalid; however, from

an outsider's point of view, when the admin MAC is set to 0 at the

time the VF driver is loaded, the VF's MAC is *not* set to 0, but to a

random non-0 value. But that's beside the point - even if I could

convince one or two SRIOV driver maintainers to permit setting the

admin MAC to 0, there are still several other drivers.

So rather than fighting that losing battle, this patch checks for a

failure to set the admin MAC due to an all 0 value, and retries it

with 02:00:00:00:00:00. That won't result in a random value being set

in the VF MAC at next VF driver init, but that's okay, because we

always want to set a specific value anyway. Rather, the "almost 0"

setting makes it easy to visually detect from the output of "ip link

show" which VFs are currently in use and which are free.

Resolves: https://bugzilla.redhat.com/1442040 (RHEL 7.3.z)

Resolves: https://bugzilla.redhat.com/1415609 (RHEL 7.4)

(cherry picked from commit d5f4abefc231a71e21e33e0d2eb4da8f22552c70)

---

 src/util/virnetdev.c | 42 ++++++++++++++++++++++++++++++++++++++----

 1 file changed, 38 insertions(+), 4 deletions(-)

diff --git a/src/util/virnetdev.c b/src/util/virnetdev.c

index 4739f573a..0223877ff 100644

--- a/src/util/virnetdev.c

+++ b/src/util/virnetdev.c

@@ -1391,6 +1391,14 @@ virNetDevSysfsFile(char **pf_sysfs_device_link ATTRIBUTE_UNUSED,

 #if defined(__linux__) && defined(HAVE_LIBNL) && defined(IFLA_VF_MAX)

+static virMacAddr zeroMAC = { .addr = { 0, 0, 0, 0, 0, 0 } };

+

+/* if a net driver doesn't allow setting MAC to all 0, try setting

+ * to this (the only bit that is set is the "locally administered" bit")

+ */

+static virMacAddr altZeroMAC = { .addr = { 2, 0, 0, 0, 0, 0 } };

+

+

 static struct nla_policy ifla_vf_policy[IFLA_VF_MAX+1] = {

     [IFLA_VF_MAC]       = { .type = NLA_UNSPEC,

                             .maxlen = sizeof(struct ifla_vf_mac) },

@@ -1401,7 +1409,8 @@ static struct nla_policy ifla_vf_policy[IFLA_VF_MAX+1] = {

 static int

 virNetDevSetVfConfig(const char *ifname, int vf,

-                     const virMacAddr *macaddr, int vlanid)

+                     const virMacAddr *macaddr, int vlanid,

+                     bool *allowRetry)

 {

     int rc = -1;

     struct nlmsghdr *resp = NULL;

@@ -1478,7 +1487,15 @@ virNetDevSetVfConfig(const char *ifname, int vf,

         if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))

             goto malformed_resp;

-        if (err->error) {

+        /* 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 */

             char macstr[VIR_MAC_STRING_BUFLEN];

             virReportSystemError(-err->error,

@@ -1490,6 +1507,7 @@ virNetDevSetVfConfig(const char *ifname, int vf,

                                  vlanid,

                                  ifname ? ifname : "(unspecified)",

                                  vf);

+            *allowRetry = false; /* no use retrying */

             goto cleanup;

         }

         break;

@@ -2126,8 +2144,24 @@ virNetDevSetNetConfig(const char *linkdev, int vf,

          * guest or host). if there is a vlanTag to set, it will take

          * effect immediately though.

          */

-        if (virNetDevSetVfConfig(pfDevName, vf, adminMAC, vlanTag) < 0)

-            goto cleanup;

+        bool allowRetry = true;

+

+        if (virNetDevSetVfConfig(pfDevName, vf,

+                                 adminMAC, vlanTag, &allowRetry) < 0) {

+            /* allowRetry will still be true if the failure was due to

+             * trying to set the MAC address to all 0. In that case,

+             * we can retry with "altZeroMAC", which is just an all-0 MAC

+             * with the "locally administered" bit set.

+             */

+            if (!allowRetry)

+                goto cleanup;

+

+            allowRetry = false;

+            if (virNetDevSetVfConfig(pfDevName, vf,

+                                     &altZeroMAC, vlanTag, &allowRetry) < 0) {

+                goto cleanup;

+            }

+        }

     }

     ret = 0;

-- 

2.12.2