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Re: [libvirt] [PATCH 6/8] Add client side support for FD passing



On 10/21/2011 06:55 AM, Daniel P. Berrange wrote:
From: "Daniel P. Berrange"<berrange redhat com>

Extend the RPC client code to allow file descriptors to be sent
to the server with calls, and received back with replies.

* src/remote/remote_driver.c: Stub extra args
* src/libvirt_private.syms, src/rpc/virnetclient.c,
   src/rpc/virnetclient.h, src/rpc/virnetclientprogram.c,
   src/rpc/virnetclientprogram.h: Extend APIs to allow
   FD passing
---
  src/libvirt_private.syms      |    4 +++
  src/remote/remote_driver.c    |    1 +
  src/rpc/virnetclient.c        |   25 +++++++++++++++++++++++
  src/rpc/virnetclient.h        |    2 +
  src/rpc/virnetclientprogram.c |   44 +++++++++++++++++++++++++++++++++++++++-
  src/rpc/virnetclientprogram.h |    4 +++
  6 files changed, 78 insertions(+), 2 deletions(-)


+bool virNetClientHasPassFD(virNetClientPtr client)
+{
+    int hasPassFD;

s/int/bool/

+    virNetClientLock(client);
+    hasPassFD = virNetSocketHasPassFD(client->sock);
+    virNetClientUnlock(client);
+    return hasPassFD;

so that your return value matches the signature off the bat.

@@ -697,6 +708,15 @@ virNetClientCallDispatch(virNetClientPtr client)
      case VIR_NET_REPLY: /* Normal RPC replies */
          return virNetClientCallDispatchReply(client);

+    case VIR_NET_REPLY_WITH_FDS: /* Normal RPC replies with FDs */
+        if (virNetMessageDecodeNumFDs(&client->msg)<  0)
+            return -1;
+        for (i = 0 ; i<  client->msg.nfds ; i++) {
+            if ((client->msg.fds[i] = virNetSocketRecvFD(client->sock))<  0)

You do realize that gnulib's sendfd/recvfd pass a single byte alongside each out-of-band fd (since passing fds with 0-byte messages isn't portable). It looks like you were careful to ensure that fds are only sent and received in between complete messages; so hopefully we don't ever run into any problems where the extra byte payloads gets interleaved with real rpc traffic, since that could cause confusion on the current state of bytes going between endpoints. Is encryption ever used on UNIX sockets, or is that only for TCP connections?

@@ -278,13 +285,30 @@ int virNetClientProgramCall(virNetClientProgramPtr prog,
      msg->header.prog = prog->program;
      msg->header.vers = prog->version;
      msg->header.status = VIR_NET_OK;
-    msg->header.type = VIR_NET_CALL;
+    msg->header.type = noutfds ? VIR_NET_CALL_WITH_FDS : VIR_NET_CALL;
      msg->header.serial = serial;
      msg->header.proc = proc;
+    msg->nfds = noutfds;
+    if (VIR_ALLOC_N(msg->fds, msg->nfds)<  0) {
+        virReportOOMError();
+        goto error;
+    }
+    for (i = 0 ; i<  msg->nfds ; i++) {
+        if ((msg->fds[i] = dup(outfds[i]))<  0) {

Should we be using fcntl(outfds[i], F_DUP_CLOEXEC, 0) here, so that the dups don't leak out of this process?

ACK with nits fixed.

--
Eric Blake   eblake redhat com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org


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