On Sat, Nov 30, 2013 at 01:27:33PM +0100, Thomas Graf wrote:

Based on the initial patch by Cong Wang posted a couple of months
ago.

This is the user space counterpart needed for the kernel patch
'[PATCH net-next 3/8] openvswitch: Enable memory mapped Netlink i/o'

Allows the kernel to construct Netlink messages on memory mapped
buffers and thus avoids copying. The functionality is enabled on
sockets used for unicast traffic.

Further optimizations are possible by avoiding the copy into the
ofpbuf after reading.

Signed-off-by: Thomas Graf <redacted>

Clang reports:

    ../lib/netlink-socket.c:330:12: error: cast from 'char *' to 'struct nl_mmap_hdr *' increases required alignment from 1 to 4 [-Werror,-Wcast-align]
        return (struct nl_mmap_hdr *)(start + r->head * sock->frame_size);
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    ../lib/netlink-socket.c:369:22: error: implicit declaration of function '__ALIGN_KERNEL' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
    -> sock->frame_size)
                         ^
    ../lib/netlink-protocol.h:213:26: note: expanded from macro 'NL_MMAP_HDRLEN'
    #define NL_MMAP_HDRLEN                  NL_MMAP_MSG_ALIGN(sizeof(struct nl_mmap_hdr))
                                            ^
    ../lib/netlink-protocol.h:212:32: note: expanded from macro 'NL_MMAP_MSG_ALIGN'
    #define NL_MMAP_MSG_ALIGN(sz)           __ALIGN_KERNEL(sz, NL_MMAP_MSG_ALIGNMENT)
                                            ^
GCC reports:

    ../lib/netlink-socket.c: In function 'nl_sock_send_mmap':
    ../lib/netlink-socket.c:369:5: error: implicit declaration of function '__ALIGN_KERNEL' [-Werror=implicit-function-declaration]
    cc1: all warnings being treated as errors

Thanks,

Ben.