Re: [libvirt] [PATCH] qemu: enable direct migration over IPv6
On 02/25/2013 07:15 AM, Ján Tomko wrote:
Use virURIParse in qemuMigrationPrepareDirect to allow parsing
IPv6 addresses, which would cause an 'incorrect :port' error message
before.
To be able to migrate over IPv6, QEMU needs to listen on [::] instead
of 0.0.0.0. This patch adds a call to getaddrinfo and sets the listen
address based on the result.
It also uses the same listen address for the NBD server.
This will break migration if a hostname does not resolve to the same
address family on both sides.
Bug: https://bugzilla.redhat.com/show_bug.cgi?id=846013
---
Diff to V1:
* initialize uri_str
* reuse STRSKIP("tcp:") result instead of doing strlen on it
* print a warning instead of failing when the hostname can't be resolved
Diff to V2:
* freeaddrinfo
* separate the listen address to allow reuse in qemuMigrationStartNBDServer
src/qemu/qemu_migration.c | 77 ++++++++++++++++++++++++++++++++++++-----------
1 file changed, 59 insertions(+), 18 deletions(-)
diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index cae58fa..ff9b959 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -22,7 +22,10 @@
#include <config.h>
+#include <netdb.h>
+#include <sys/socket.h>
#include <sys/time.h>
+#include <sys/types.h>
You rarely ever need <sys/types.h> - most types in that header are
guaranteed to be provided by any other standard header that has an
interface using that type; or put another way, POSIX says that inclusion
of other headers may drag in <sys/types.h>, and we have already been
relying on that reliably happening. The other two additions are
important, though.
@@ -2292,9 +2296,14 @@ qemuMigrationPrepareDirect(virQEMUDriverPtr driver,
static int port = 0;
int this_port;
char *hostname = NULL;
+ char listenAddr[8];
char migrateFrom [64];
As long as you are touching this, remove the space before [64]. Then
again, 64 was a magic number; a much safer approach would have been
char migrateFrom[sizeof("tcp:0.0.0.0:") + INT_BUFSIZE_BOUND(int)];
(using gnulib's "intprops.h"), or even getting rid of the stack-alloc
temporary (see below for thoughts about using virBufferPtr instead)
+ if (getaddrinfo(hostname, NULL, NULL, &info)) {
+ VIR_WARN("unable to get address info for %s, defaulting to IPv4",
+ hostname);
Would it be nice to include the gai_strerror() reason for why
getaddrinfo() failed?
+ } else {
+ ipv6 = info->ai_family == AF_INET6;
+ freeaddrinfo(info);
+ }
+
if (*uri_out)
VIR_DEBUG("Generated uri_out=%s", *uri_out);
- /* QEMU will be started with -incoming tcp:0.0.0.0:port */
- snprintf(migrateFrom, sizeof(migrateFrom), "tcp:0.0.0.0:%d", this_port);
+ /* QEMU will be started with -incoming tcp:0.0.0.0:port
+ * or -incoming tcp:[::]:port for IPv6 */
+ if (ipv6)
+ snprintf(listenAddr, sizeof(listenAddr), "[::]");
+ else
+ snprintf(listenAddr, sizeof(listenAddr), "0.0.0.0");
Eww. Even though this is safe (because you sized listenAddr big
enough), I'd rather see:
const char *listenAddr;
if (ipv6)
listenAddr = "[::]";
else
listenAddr = "0.0.0.0";
+
+ snprintf(migrateFrom, sizeof(migrateFrom),
+ "tcp:%s:%d", listenAddr, this_port);
And while this snprintf was pre-existing and also happens to be large
enough, I can't help but think it would be nicer to pass a virBufferPtr
instead of a const char * to qemuMigrationPrepareAny, although that
would mean more refactoring done in an independent patch.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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