From 1723d6b1cfe6572881f578bce3aa25185b81b148 Mon Sep 17 00:00:00 2001 From: "Daniel P. Berrange" Date: Fri, 22 Dec 2017 11:04:30 +0000 Subject: sockets: allow SocketAddress 'fd' to reference numeric file descriptors MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The SocketAddress 'fd' kind accepts the name of a file descriptor passed to the monitor with the 'getfd' command. This makes it impossible to use the 'fd' kind in cases where a monitor is not available. This can apply in handling command line argv at startup, or simply if internal code wants to use SocketAddress and pass a numeric FD it has acquired from elsewhere. Fortunately the 'getfd' command mandated that the FD names must not start with a leading digit. We can thus safely extend semantics of the SocketAddress 'fd' kind, to allow a purely numeric name to reference an file descriptor that QEMU already has open. There will be restrictions on when each kind can be used. In codepaths where we are handling a monitor command (ie cur_mon != NULL), we will only support use of named file descriptors as before. Use of FD numbers is still not permitted for monitor commands. In codepaths where we are not handling a monitor command (ie cur_mon == NULL), we will not support named file descriptors. Instead we can reference FD numers explicitly. This allows the app spawning QEMU to intentionally "leak" a pre-opened socket to QEMU and reference that in a SocketAddress definition, or for code inside QEMU to pass pre-opened FDs around. Reviewed-by: Eric Blake Reviewed-by: Marc-André Lureau Signed-off-by: Daniel P. Berrange --- qapi/sockets.json | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'qapi') diff --git a/qapi/sockets.json b/qapi/sockets.json index ac022c6ad0..fc81d8d5e8 100644 --- a/qapi/sockets.json +++ b/qapi/sockets.json @@ -123,6 +123,13 @@ # # @unix: Unix domain socket # +# @vsock: VMCI address +# +# @fd: decimal is for file descriptor number, otherwise a file descriptor name. +# Named file descriptors are permitted in monitor commands, in combination +# with the 'getfd' command. Decimal file descriptors are permitted at +# startup or other contexts where no monitor context is active. +# # Since: 2.9 ## { 'enum': 'SocketAddressType', -- cgit v1.2.1