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[libvirt] [RFC][PATCH] LXC allow a container to have ethN named interfaces



Note that this patch is not mature yet and still proof-
of-concept prototype, although it actually works.

Current implementation of lxc driver creates vethN named
interface(s) in the host and passes as it is to a container.
The reason why it doesn't use ethN is due to the limitation
that one namespace cannot have multiple iterfaces that have
an identical name so that we give up creating ethN named
interface in the host for the container.

However, we should be able to allow the container to have
ethN by changing the name after clone(CLONE_NEWNET) in
controller.

To this end, this patch extends --veth argument of
controller to be able to have two names; one is the name
of a created veth, and the other is a new name. The format
is:

  --veth veth1,eth0 --veth veth3,eth1 ...

where veth1 is old name and eth0 is new one. The implementation
also allows a single name, in that case, controller does not
do nothing for the interface, which is the original behavior.

The numbering of the new names is simply ascending order
from zero. So if there is one interface, its name will
be eth0.
---
 src/lxc/lxc_container.c  |   23 ++++++++++++++++++-----
 src/lxc/lxc_container.h  |    1 +
 src/lxc/lxc_controller.c |   30 ++++++++++++++++++++++++++++--
 src/lxc/lxc_driver.c     |   30 +++++++++++++++++++++++++-----
 src/lxc/veth.c           |   20 ++++++++++++++++++++
 src/lxc/veth.h           |    1 +
 6 files changed, 93 insertions(+), 12 deletions(-)

diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
index f4381e7..f065788 100644
--- a/src/lxc/lxc_container.c
+++ b/src/lxc/lxc_container.c
@@ -84,6 +84,7 @@ struct __lxc_child_argv {
     virDomainDefPtr config;
     unsigned int nveths;
     char **veths;
+    char **newveths;
     int monitor;
     char *ttyPath;
 };
@@ -233,14 +234,23 @@ static int lxcContainerWaitForContinue(int control)
  * Returns 0 on success or nonzero in case of error
  */
 static int lxcContainerEnableInterfaces(unsigned int nveths,
-                                        char **veths)
+                                        char **veths, char **newveths)
 {
     int rc = 0;
     unsigned int i;
 
     for (i = 0 ; i < nveths ; i++) {
-        DEBUG("Enabling %s", veths[i]);
-        rc =  vethInterfaceUpOrDown(veths[i], 1);
+        char *veth = veths[i];
+        if (newveths[i] && !STREQ(veths[i], newveths[i])) {
+            DEBUG("changing %s", veths[i]);
+            rc = setInterfaceName(veths[i], newveths[i]);
+            if (0 != rc) {
+                goto error_out;
+            }
+            veth = newveths[i];
+        }
+        DEBUG("Enabling %s", veth);
+        rc =  vethInterfaceUpOrDown(veth, 1);
         if (0 != rc) {
             goto error_out;
         }
@@ -758,7 +768,9 @@ static int lxcContainerChild( void *data )
         return -1;
 
     /* enable interfaces */
-    if (lxcContainerEnableInterfaces(argv->nveths, argv->veths) < 0)
+    if (lxcContainerEnableInterfaces(argv->nveths,
+                                     argv->veths,
+                                     argv->newveths) < 0)
         return -1;
 
     /* drop a set of root capabilities */
@@ -786,6 +798,7 @@ static int userns_supported(void)
 int lxcContainerStart(virDomainDefPtr def,
                       unsigned int nveths,
                       char **veths,
+                      char **newveths,
                       int control,
                       char *ttyPath)
 {
@@ -793,7 +806,7 @@ int lxcContainerStart(virDomainDefPtr def,
     int flags;
     int stacksize = getpagesize() * 4;
     char *stack, *stacktop;
-    lxc_child_argv_t args = { def, nveths, veths, control, ttyPath };
+    lxc_child_argv_t args = { def, nveths, veths, newveths, control, ttyPath };
 
     /* allocate a stack for the container */
     if (VIR_ALLOC_N(stack, stacksize) < 0) {
diff --git a/src/lxc/lxc_container.h b/src/lxc/lxc_container.h
index a1dd5a1..d796380 100644
--- a/src/lxc/lxc_container.h
+++ b/src/lxc/lxc_container.h
@@ -49,6 +49,7 @@ int lxcContainerSendContinue(int control);
 int lxcContainerStart(virDomainDefPtr def,
                       unsigned int nveths,
                       char **veths,
+                      char **newveths,
                       int control,
                       char *ttyPath);
 
diff --git a/src/lxc/lxc_controller.c b/src/lxc/lxc_controller.c
index 545f718..75dd73a 100644
--- a/src/lxc/lxc_controller.c
+++ b/src/lxc/lxc_controller.c
@@ -493,6 +493,7 @@ static int
 lxcControllerRun(virDomainDefPtr def,
                  unsigned int nveths,
                  char **veths,
+                 char **newveths,
                  int monitor,
                  int client,
                  int appPty)
@@ -603,6 +604,7 @@ lxcControllerRun(virDomainDefPtr def,
     if ((container = lxcContainerStart(def,
                                        nveths,
                                        veths,
+                                       newveths,
                                        control[1],
                                        containerPtyPath)) < 0)
         goto cleanup;
@@ -649,6 +651,7 @@ int main(int argc, char *argv[])
     char *name = NULL;
     int nveths = 0;
     char **veths = NULL;
+    char **newveths = NULL;
     int monitor = -1;
     int appPty = -1;
     int bg = 0;
@@ -691,10 +694,33 @@ int main(int argc, char *argv[])
                 virReportOOMError(NULL);
                 goto cleanup;
             }
-            if ((veths[nveths++] = strdup(optarg)) == NULL) {
+            if (VIR_REALLOC_N(newveths, nveths+1) < 0) {
                 virReportOOMError(NULL);
                 goto cleanup;
             }
+            {
+                char *sep = strchr(optarg, ',');
+                if (sep) {
+                    *sep = '\0';
+                    sep++;
+                    if ((veths[nveths] = strdup(optarg)) == NULL) {
+                        virReportOOMError(NULL);
+                        goto cleanup;
+                    }
+                    if ((newveths[nveths] = strdup(sep)) == NULL) {
+                        virReportOOMError(NULL);
+                        goto cleanup;
+                    }
+                    nveths++;
+                } else {
+                    if ((veths[nveths] = strdup(optarg)) == NULL) {
+                        virReportOOMError(NULL);
+                        goto cleanup;
+                    }
+                    newveths[nveths] = NULL;
+                    nveths++;
+                }
+            }
             break;
 
         case 'c':
@@ -803,7 +829,7 @@ int main(int argc, char *argv[])
         goto cleanup;
     }
 
-    rc = lxcControllerRun(def, nveths, veths, monitor, client, appPty);
+    rc = lxcControllerRun(def, nveths, veths, newveths, monitor, client, appPty);
 
 
 cleanup:
diff --git a/src/lxc/lxc_driver.c b/src/lxc/lxc_driver.c
index 4f0787b..1323cff 100644
--- a/src/lxc/lxc_driver.c
+++ b/src/lxc/lxc_driver.c
@@ -693,13 +693,15 @@ static int lxcVMCleanup(virConnectPtr conn,
 static int lxcSetupInterfaces(virConnectPtr conn,
                               virDomainDefPtr def,
                               unsigned int *nveths,
-                              char ***veths)
+                              char ***veths,
+                              char ***newveths)
 {
     int rc = -1, i;
     char *bridge = NULL;
     char parentVeth[PATH_MAX] = "";
     char containerVeth[PATH_MAX] = "";
     brControl *brctl = NULL;
+    char *newveth;
 
     if (brInit(&brctl) != 0)
         return -1;
@@ -744,10 +746,20 @@ static int lxcSetupInterfaces(virConnectPtr conn,
         if (NULL == def->nets[i]->ifname) {
             def->nets[i]->ifname = strdup(parentVeth);
         }
+
         if (VIR_REALLOC_N(*veths, (*nveths)+1) < 0)
             goto error_exit;
-        if (((*veths)[(*nveths)++] = strdup(containerVeth)) == NULL)
+        if (VIR_REALLOC_N(*newveths, (*nveths)+1) < 0)
+            goto error_exit;
+
+        if (((*veths)[*nveths] = strdup(containerVeth)) == NULL)
+            goto error_exit;
+        if (virAsprintf(&newveth, "eth%d", i) < 0)
             goto error_exit;
+        if (((*newveths)[*nveths] = strdup(newveth)) == NULL)
+            goto error_exit;
+        (*nveths)++;
+        VIR_FREE(newveth);
 
         if (NULL == def->nets[i]->ifname) {
             lxcError(NULL, NULL, VIR_ERR_INTERNAL_ERROR,
@@ -906,6 +918,7 @@ static int lxcControllerStart(virConnectPtr conn,
                               virDomainObjPtr vm,
                               int nveths,
                               char **veths,
+                              char **newveths,
                               int appPty,
                               int logfd)
 {
@@ -1029,7 +1042,13 @@ static int lxcControllerStart(virConnectPtr conn,
 
     for (i = 0 ; i < nveths ; i++) {
         ADD_ARG_LIT("--veth");
-        ADD_ARG_LIT(veths[i]);
+        if (newveths[i]) {
+            if (virAsprintf(&tmp, "%s,%s", veths[i], newveths[i]) < 0)
+                goto no_memory;
+            ADD_ARG_LIT(tmp);
+        } else {
+            ADD_ARG_LIT(veths[i]);
+        }
     }
 
     ADD_ARG(NULL);
@@ -1107,6 +1126,7 @@ static int lxcVmStart(virConnectPtr conn,
     int logfd = -1;
     unsigned int nveths = 0;
     char **veths = NULL;
+    char **newveths = NULL;
 
     if ((r = virFileMakePath(driver->logDir)) < 0) {
         virReportSystemError(conn, r,
@@ -1135,7 +1155,7 @@ static int lxcVmStart(virConnectPtr conn,
         VIR_FREE(parentTtyPath);
     }
 
-    if (lxcSetupInterfaces(conn, vm->def, &nveths, &veths) != 0)
+    if (lxcSetupInterfaces(conn, vm->def, &nveths, &veths, &newveths) != 0)
         goto cleanup;
 
     /* Persist the live configuration now we have veth & tty info */
@@ -1152,7 +1172,7 @@ static int lxcVmStart(virConnectPtr conn,
 
     if (lxcControllerStart(conn,
                            vm,
-                           nveths, veths,
+                           nveths, veths, newveths,
                            parentTty, logfd) < 0)
         goto cleanup;
 
diff --git a/src/lxc/veth.c b/src/lxc/veth.c
index b15df8d..fbd1195 100644
--- a/src/lxc/veth.c
+++ b/src/lxc/veth.c
@@ -247,3 +247,23 @@ int setMacAddr(const char* iface, const char* macaddr)
 error_out:
     return rc;
 }
+
+int setInterfaceName(const char* iface, const char* new)
+{
+    int rc = -1;
+    const char *argv[] = {
+        "ip", "link", "set", iface, "name", new, NULL
+    };
+    int cmdResult;
+
+    if (NULL == iface || NULL == new) {
+        goto error_out;
+    }
+
+    rc = virRun(NULL, argv, &cmdResult);
+    if (0 == rc)
+        rc = cmdResult;
+
+error_out:
+    return rc;
+}
diff --git a/src/lxc/veth.h b/src/lxc/veth.h
index 8f2f514..8075a5e 100644
--- a/src/lxc/veth.h
+++ b/src/lxc/veth.h
@@ -21,5 +21,6 @@ int vethDelete(const char* veth);
 int vethInterfaceUpOrDown(const char* veth, int upOrDown);
 int moveInterfaceToNetNs(const char *iface, int pidInNs);
 int setMacAddr(const char* iface, const char* macaddr);
+int setInterfaceName(const char* iface, const char* new);
 
 #endif /* VETH_H */
-- 
1.6.2.5


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