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[libvirt] [RFC PATCH] Set and reset MAC for PASSTHROUGH mode



Hi to all,

there is a problem present in libvirt that when a PASSTHROUGH mode DIRECT NIC connection is made the MAC address of the NIC is not automatically set
and reset to the configured VM MAC and back again.

The attached patch fixes this problem by setting and resetting the MAC
while remembering the previous setting while the VM is running.
This also works if libvirtd is restarted while the VM is running.

The storing of the previous MAC address is done in a link ( currently in /tmp,
but should probably go into /var/run somewhere ).
Why a link ? It only uses one inode, no need to waste a whole data block
for 16 bytes or less. It's also more readable by simply looking at it with 'ls -l'.

Best regards

Dirk

Signed-off-by: Dirk Herrendoerfer <d.herrendoerfer at herrendoerfer.name>

diff --git a/src/libvirt_macvtap.syms b/src/libvirt_macvtap.syms
index b48565b..0520cb5 100644
--- a/src/libvirt_macvtap.syms
+++ b/src/libvirt_macvtap.syms
@@ -6,5 +6,7 @@
 # macvtap.h
 delMacvtap;
 openMacvtapTap;
+get_macaddr;
+set_macaddr;
 vpAssociatePortProfileId;
 vpDisassociatePortProfileId;
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index ef2d002..4cddbba 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -118,6 +118,7 @@ qemuPhysIfaceConnect(virDomainDefPtr def,
     int rc;
 #if WITH_MACVTAP
     char *res_ifname = NULL;
+    unsigned char old_macaddr[6];
     int vnet_hdr = 0;
     int err;

@@ -125,6 +126,53 @@ qemuPhysIfaceConnect(virDomainDefPtr def,
         net->model && STREQ(net->model, "virtio"))
         vnet_hdr = 1;

+    /** Note: When using PASSTHROUGH mode with MACVTAP devices the link
+     * devices's MAC address must be set to the VMs MAC address. In
+     * order to not confuse the first switch or bridge in line this MAC
+     * address must be reset when the VM is shut down.
+     * This is especially important when using SRIOV capable cards that
+     * emulate their switch in firmware.
+     */
+ if ( net->data.direct.mode == VIR_DOMAIN_NETDEV_MACVTAP_MODE_PASSTHRU ) {
+	rc = get_macaddr(&old_macaddr, 6, net->data.direct.linkdev);
+        if (rc) {
+            virReportSystemError(rc,
+                                 _("Getting MAC address from '%s' "
+ "to '%02x:%02x:%02x:%02x:%02x:%02x' failed."),
+                                 net->data.direct.linkdev,
+ old_macaddr[0],old_macaddr[1],old_macaddr[2], + old_macaddr[3],old_macaddr[4],old_macaddr[5]);
+        } else {
+            char oldmacname[256], newmacname[256];
+
+            sprintf(oldmacname,"%02x:%02x:%02x:%02x:%02x:%02x",
+                    old_macaddr[0],old_macaddr[1],old_macaddr[2],
+                    old_macaddr[3],old_macaddr[4],old_macaddr[5]);
+
+            sprintf(newmacname,"/tmp/%s %02x:%02x:%02x:%02x:%02x:%02x",
+                    net->data.direct.linkdev,
+                    net->mac[0],net->mac[1],net->mac[2],
+                    net->mac[3],net->mac[4],net->mac[5]);
+
+	    rc = symlink (oldmacname, newmacname);
+            if (rc) {
+                virReportSystemError(rc,
+ _("MAC link file creation failed for %s."),
+                                     net->data.direct.linkdev);
+            }
+        }
+
+	rc = set_macaddr(net->mac, 6, net->data.direct.linkdev);
+        if (rc) {
+            virReportSystemError(rc,
+                                 _("Setting MAC address on  '%s' to "
+ "'%02x:%02x:%02x:%02x:%02x:%02x' failed."),
+                                 net->data.direct.linkdev,
+                                 net->mac[0],net->mac[1],net->mac[2],
+                                 net->mac[3],net->mac[4],net->mac[5]);
+        }
+    }
+
rc = openMacvtapTap(net->ifname, net->mac, net- >data.direct.linkdev,
                         net->data.direct.mode, vnet_hdr, def->uuid,
&net->data.direct.virtPortProfile, &res_ifname,
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 1efe024..127acb8 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -2663,6 +2663,51 @@ void qemuProcessStop(struct qemud_driver *driver,
         if (net->type == VIR_DOMAIN_NET_TYPE_DIRECT) {
delMacvtap(net->ifname, net->mac, net- >data.direct.linkdev,
                        &net->data.direct.virtPortProfile);
+
+ if ( net->data.direct.mode == VIR_DOMAIN_NETDEV_MACVTAP_MODE_PASSTHRU ) {
+                char newmacname[256], linkdata[64];
+                unsigned int old_macaddr[6];
+
+ sprintf(newmacname,"/tmp/%s %02x:%02x:%02x:%02x:%02x: %02x",
+                        net->data.direct.linkdev,
+                        net->mac[0],net->mac[1],net->mac[2],
+                        net->mac[3],net->mac[4],net->mac[5]);
+
+                ret = readlink (newmacname, linkdata, 64);
+                if ( ret == 17 ) {
+                    linkdata[17] = 0;
+
+                    ret = sscanf(linkdata,"%x:%x:%x:%x:%x:%x",
+ &old_macaddr[0],&old_macaddr[1],&old_macaddr[2], + &old_macaddr[3],&old_macaddr[4],&old_macaddr[5]);
+                    if ( ret == 6 ) {
+                        unsigned char oldmac[6];
+			oldmac[0] = (unsigned char)(old_macaddr[0] & 0xFF) ;
+			oldmac[1] = (unsigned char)(old_macaddr[1] & 0xFF) ;
+			oldmac[2] = (unsigned char)(old_macaddr[2] & 0xFF) ;
+			oldmac[3] = (unsigned char)(old_macaddr[3] & 0xFF) ;
+			oldmac[4] = (unsigned char)(old_macaddr[4] & 0xFF) ;
+			oldmac[5] = (unsigned char)(old_macaddr[5] & 0xFF) ;
+
+                        VIR_WARN(("Resetting MAC address on '%s' "
+ "to '%02x:%02x:%02x:%02x:%02x: %02x'."),
+                                  net->data.direct.linkdev,
+                                  oldmac[0],oldmac[1],oldmac[2],
+                                  oldmac[3],oldmac[4],oldmac[5]);
+ /*reset mac and remove link file-ignore restults*/ + ret = set_macaddr(oldmac, 6, net- >data.direct.linkdev);
+			ret = unlink(newmacname);
+                    } else {
+                        VIR_WARN(("Scanning MAC address from '%s' "
+                                  "failed ! Got %i values."),
+                                  linkdata, ret);
+                    }
+                } else {
+                    VIR_WARN(("Reading MAC address from '%s' failed ! "
+                              "Got %i bytes."),
+                              newmacname, ret);
+                }
+            }
             VIR_FREE(net->ifname);
         }
     }
diff --git a/src/util/macvtap.c b/src/util/macvtap.c
index 068638e..1026a84 100644
--- a/src/util/macvtap.c
+++ b/src/util/macvtap.c
@@ -191,6 +191,155 @@ err_exit:

 # if WITH_MACVTAP

+/**
+ * get_macaddr:
+ * Get the MAC address of a network device
+ *
+ * @macaddress: Pointer where the MAC address will be stored
+ * @macaddrsize: Size of the MAC address.
+ * @srcdev: The interface name of the NIC to get the MAC from
+ *
+ * Returns zero in case of success,
+ * negative value otherwise with error reported.
+ *
+ */
+int
+get_macaddr(const unsigned char *macaddress, int macaddrsize,
+            const char *srcdev )
+{
+    int sockfd;
+    int io;
+    char buffer[1024];
+    struct ifreq ifr;
+
+    strcpy(ifr.ifr_name, srcdev);
+
+    sockfd = socket(AF_INET, SOCK_STREAM, 0);
+    if(sockfd < 0){
+        return -1;
+    }
+
+    io = ioctl(sockfd, SIOCGIFHWADDR, (char *)&ifr);
+    if(io < 0){
+        return -1;
+    }
+
+    bcopy( ifr.ifr_ifru.ifru_hwaddr.sa_data, macaddress, macaddrsize);
+
+    return 0;
+}
+
+/**
+ * Set_macaddr:
+ * Set the MAC address of a network device
+ *
+ * @macaddress: MAC address to assign to the NIC
+ * @macaddrsize: Size of the MAC address.
+ * @srcdev: The interface name of the NIC
+ *
+ * Returns zero in case of success,
+ * negative value otherwise with error reported.
+ *
+ */
+int
+set_macaddr(const unsigned char *macaddress, int macaddrsize,
+            const char *srcdev )
+{
+    int rc = 0;
+    struct nlmsghdr *resp;
+    struct nlmsgerr *err;
+    struct ifinfomsg ifinfo = { .ifi_family = AF_UNSPEC };
+    int ifindex;
+    unsigned char *recvbuf = NULL;
+    unsigned int recvbuflen;
+    struct nl_msg *nl_msg;
+    struct nlattr *linkinfo;
+
+    if (ifaceGetIndex(true, srcdev, &ifindex) != 0)
+        return -1;
+
+    nl_msg = nlmsg_alloc_simple(RTM_SETLINK, NLM_F_REQUEST);
+
+    if (!nl_msg) {
+        virReportOOMError();
+        return -1;
+    }
+
+ if (nlmsg_append(nl_msg, &ifinfo, sizeof(ifinfo), NLMSG_ALIGNTO) < 0)
+        goto buffer_too_small;
+
+    if (nla_put_u32(nl_msg, IFLA_LINK, ifindex) < 0)
+        goto buffer_too_small;
+
+    if (nla_put(nl_msg, IFLA_ADDRESS, macaddrsize, macaddress) < 0)
+        goto buffer_too_small;
+
+    if (srcdev &&
+        nla_put(nl_msg, IFLA_IFNAME, strlen(srcdev)+1, srcdev) < 0)
+        goto buffer_too_small;
+
+    if (nlComm(nl_msg, &recvbuf, &recvbuflen, 0) < 0) {
+        rc = -1;
+        goto err_exit;
+    }
+
+    if (recvbuflen < NLMSG_LENGTH(0) || recvbuf == NULL)
+        goto malformed_resp;
+
+    resp = (struct nlmsghdr *)recvbuf;
+
+    switch (resp->nlmsg_type) {
+    case NLMSG_ERROR:
+        err = (struct nlmsgerr *)NLMSG_DATA(resp);
+        if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
+            goto malformed_resp;
+
+        switch (err->error) {
+
+        case 0:
+            break;
+
+        case -EEXIST:
+            rc = -1;
+            break;
+
+        default:
+            macvtapError(VIR_ERR_INTERNAL_ERROR, "%s",
+                         _("error setting device mac address"));
+            rc = -1;
+        }
+        break;
+
+    case NLMSG_DONE:
+        break;
+
+    default:
+        goto malformed_resp;
+    }
+
+err_exit:
+    nlmsg_free(nl_msg);
+
+    VIR_FREE(recvbuf);
+
+    return rc;
+
+malformed_resp:
+    nlmsg_free(nl_msg);
+
+    macvtapError(VIR_ERR_INTERNAL_ERROR, "%s",
+                 _("malformed netlink response message"));
+    VIR_FREE(recvbuf);
+    return -1;
+
+buffer_too_small:
+    nlmsg_free(nl_msg);
+
+    macvtapError(VIR_ERR_INTERNAL_ERROR, "%s",
+                 _("allocated netlink buffer is too small"));
+    return -1;
+}
+
 static int
 link_add(const char *type,
          const unsigned char *macaddress, int macaddrsize,
diff --git a/src/util/macvtap.h b/src/util/macvtap.h
index a1383c4..d71546a 100644
--- a/src/util/macvtap.h
+++ b/src/util/macvtap.h
@@ -75,6 +75,12 @@ enum virVMOperationType {

 #  include "internal.h"

+int get_macaddr(const unsigned char *macaddress, int macaddrsize,
+            const char *srcdev );
+
+int set_macaddr(const unsigned char *macaddress, int macaddrsize,
+            const char *srcdev );
+
 int openMacvtapTap(const char *ifname,
                    const unsigned char *macaddress,
                    const char *linkdev,


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