On Sat, Sep 03, 2011 at 07:26:08PM +0200, kaber@xxxxxxxxx wrote: > From: Patrick McHardy <kaber@xxxxxxxxx> > > Add support for memory mapped sendmsg() to netlink. Userspace queued to > be processed frames into the TX ring and invokes sendmsg with > msg.iov.iov_base = NULL to trigger processing of all pending messages. > > Since the kernel usually performs full message validation before beginning > processing, userspace must be prevented from modifying the message > contents while the kernel is processing them. In order to do so, the > frames contents are copied to an allocated skb in case the the ring is > mapped more than once or the file descriptor is shared (f.i. through > AF_UNIX file descriptor passing). > > Otherwise an skb without a data area is allocated, the data pointer set > to point to the data area of the ring frame and the skb is processed. > Once the skb is freed, the destructor releases the frame back to userspace > by setting the status to NL_MMAP_STATUS_UNUSED. Is this protected from threads? Like: one thread waits on sendmsg() and another (same process) changes the buffer. Best Regards, Michał Mirosław -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
