Re: [libvirt] [PATCH 2/4] Try harder to send RPC error message back to client

When failing to serialize the normal RPC reply, try harder to send a error message back to the client, instead of immediately closing the connection. * daemon/dispatch.c: Improve error messages when RPC reply can not be sent --- daemon/dispatch.c | 47 +++++++++++++++++++++++++++++------------------ 1 files changed, 29 insertions(+), 18 deletions(-) diff --git a/daemon/dispatch.c b/daemon/dispatch.c index d6c2eb1..22eef36 100644 --- a/daemon/dispatch.c +++ b/daemon/dispatch.c @@ -548,7 +548,8 @@ remoteDispatchClientCall (struct qemud_server *server, if (remoteEncodeClientMessageHeader(msg) < 0) { xdr_free (data->ret_filter, (char*)&ret); - goto fatal_error; + remoteDispatchFormatError(&rerr, "%s", _("failed to serialize reply header")); + goto xdr_hdr_error; } @@ -558,22 +559,30 @@ remoteDispatchClientCall (struct qemud_server *server, msg->bufferLength, XDR_ENCODE); - if (xdr_setpos(&xdr, msg->bufferOffset) == 0) - goto xdr_error; + if (xdr_setpos(&xdr, msg->bufferOffset) == 0) { + remoteDispatchFormatError(&rerr, "%s", _("failed to change XDR reply offset")); + goto xdr_error; + } /* If OK, serialise return structure, if error serialise error. */ /* Serialise reply data */ - if (!((data->ret_filter) (&xdr, &ret))) + if (!((data->ret_filter) (&xdr, &ret))) { + remoteDispatchFormatError(&rerr, "%s", _("failed to serialize reply payload (probable message size limit)")); goto xdr_error; + } /* Update the length word. */ msg->bufferOffset += xdr_getpos (&xdr); len = msg->bufferOffset; - if (xdr_setpos (&xdr, 0) == 0) + if (xdr_setpos (&xdr, 0) == 0) { + remoteDispatchFormatError(&rerr, "%s", _("failed to change XDR reply offset")); goto xdr_error; + } - if (!xdr_u_int (&xdr, &len)) + if (!xdr_u_int (&xdr, &len)) { + remoteDispatchFormatError(&rerr, "%s", _("failed to update reply length header")); goto xdr_error; + } xdr_destroy (&xdr); xdr_free (data->ret_filter, (char*)&ret); @@ -588,25 +597,27 @@ remoteDispatchClientCall (struct qemud_server *server, return 0; +xdr_error: + /* Bad stuff serializing reply. Try to send a little info + * back to client to assist in bug reporting/diagnosis */ + xdr_free (data->ret_filter, (char*)&ret); + xdr_destroy (&xdr); + /* fallthrough */ + +xdr_hdr_error: + VIR_WARN("Failed to serialize reply for program '%d' proc '%d' as XDR", + msg->hdr.prog, msg->hdr.proc); + /* fallthrough */ + rpc_error: - /* Semi-bad stuff happened, we can still try to send back - * an RPC error message to client */ + /* Bad stuff (de-)serializing message, but we have an + * RPC error message we can send back to the client */ rv = remoteSerializeReplyError(client, &rerr, &msg->hdr); if (rv >= 0) VIR_FREE(msg); return rv; - -xdr_error: - /* Seriously bad stuff happened, so we'll kill off this client - and not send back any RPC error */ - xdr_free (data->ret_filter, (char*)&ret); - xdr_destroy (&xdr); -fatal_error: - VIR_WARN("Failed to serialize reply for program '%d' proc '%d' as XDR", - msg->hdr.prog, msg->hdr.proc); - return -1; }