[openvswitch] netlink: Implement & enable memory mapped netlink i/o

diff --git a/AUTHORS b/AUTHORS
index 76951e7..f48aa5d 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -22,6 +22,7 @@  Bryan Phillippe         bp@toroki.com
 Casey Barker            crbarker@google.com
 Chris Wright            chrisw@sous-sol.org
 Chuck Short             zulcss@ubuntu.com
+Cong Wang               amwang@redhat.com
 Damien Millescamps      damien.millescamps@6wind.com
 Dan Carpenter           dan.carpenter@oracle.com
 Dan Wendlandt           dan@nicira.com
diff --git a/lib/dpif-linux.c b/lib/dpif-linux.c
index 0442f77..1dcf321 100644
--- a/lib/dpif-linux.c
+++ b/lib/dpif-linux.c
@@ -495,7 +495,7 @@  dpif_linux_port_add__(struct dpif *dpif_, struct netdev *netdev,
     int error;
 
     if (dpif->epoll_fd >= 0) {
-        error = nl_sock_create(NETLINK_GENERIC, &sock);
+        error = nl_sock_create(NETLINK_GENERIC, &sock, true);
         if (error) {
             return error;
         }
@@ -765,7 +765,7 @@  dpif_linux_port_poll(const struct dpif *dpif_, char **devnamep)
         struct nl_sock *sock;
         int error;
 
-        error = nl_sock_create(NETLINK_GENERIC, &sock);
+        error = nl_sock_create(NETLINK_GENERIC, &sock, false);
         if (error) {
             return error;
         }
@@ -1265,7 +1265,7 @@  dpif_linux_recv_set__(struct dpif *dpif_, bool enable)
             uint32_t upcall_pid;
             int error;
 
-            error = nl_sock_create(NETLINK_GENERIC, &sock);
+            error = nl_sock_create(NETLINK_GENERIC, &sock, true);
             if (error) {
                 return error;
             }
diff --git a/lib/netdev-linux.c b/lib/netdev-linux.c
index ae0e5a0..ea39d22 100644
--- a/lib/netdev-linux.c
+++ b/lib/netdev-linux.c
@@ -478,7 +478,7 @@  netdev_linux_notify_sock(void)
     if (ovsthread_once_start(&once)) {
         int error;
 
-        error = nl_sock_create(NETLINK_ROUTE, &sock);
+        error = nl_sock_create(NETLINK_ROUTE, &sock, false);
         if (!error) {
             error = nl_sock_join_mcgroup(sock, RTNLGRP_LINK);
             if (error) {
diff --git a/lib/netlink-notifier.c b/lib/netlink-notifier.c
index 9aa185d..047ce75 100644
--- a/lib/netlink-notifier.c
+++ b/lib/netlink-notifier.c
@@ -109,7 +109,7 @@  nln_notifier_create(struct nln *nln, nln_notify_func *cb, void *aux)
         struct nl_sock *sock;
         int error;
 
-        error = nl_sock_create(nln->protocol, &sock);
+        error = nl_sock_create(nln->protocol, &sock, false);
         if (!error) {
             error = nl_sock_join_mcgroup(sock, nln->multicast_group);
         }
diff --git a/lib/netlink-protocol.h b/lib/netlink-protocol.h
index 3009fc5..1d18e22 100644
--- a/lib/netlink-protocol.h
+++ b/lib/netlink-protocol.h
@@ -145,6 +145,39 @@  enum {
 };
 
 #define CTRL_ATTR_OP_MAX (__CTRL_ATTR_OP_MAX - 1)
+
+#define NETLINK_RX_RING                6
+#define NETLINK_TX_RING                7
+
+struct nl_mmap_req {
+        unsigned int    nm_block_size;
+        unsigned int    nm_block_nr;
+        unsigned int    nm_frame_size;
+        unsigned int    nm_frame_nr;
+};
+
+struct nl_mmap_hdr {
+        unsigned int    nm_status;
+        unsigned int    nm_len;
+        __u32           nm_group;
+        /* credentials */
+        __u32           nm_pid;
+        __u32           nm_uid;
+        __u32           nm_gid;
+};
+
+enum nl_mmap_status {
+        NL_MMAP_STATUS_UNUSED,
+        NL_MMAP_STATUS_RESERVED,
+        NL_MMAP_STATUS_VALID,
+        NL_MMAP_STATUS_COPY,
+        NL_MMAP_STATUS_SKIP,
+};
+
+#define NL_MMAP_MSG_ALIGNMENT           NLMSG_ALIGNTO
+#define NL_MMAP_MSG_ALIGN(sz)           __ALIGN_KERNEL(sz, NL_MMAP_MSG_ALIGNMENT)
+#define NL_MMAP_HDRLEN                  NL_MMAP_MSG_ALIGN(sizeof(struct nl_mmap_hdr))
+
 #endif  /* !HAVE_NETLINK */
 
 /* These were introduced all together in 2.6.24. */
diff --git a/lib/netlink-socket.c b/lib/netlink-socket.c
index 3420503..7181dfc 100644
--- a/lib/netlink-socket.c
+++ b/lib/netlink-socket.c
@@ -21,6 +21,7 @@ 
 #include <stdlib.h>
 #include <sys/types.h>
 #include <sys/uio.h>
+#include <sys/mman.h>
 #include <unistd.h>
 #include "coverage.h"
 #include "dynamic-string.h"
@@ -40,7 +41,9 @@  VLOG_DEFINE_THIS_MODULE(netlink_socket);
 COVERAGE_DEFINE(netlink_overflow);
 COVERAGE_DEFINE(netlink_received);
 COVERAGE_DEFINE(netlink_recv_jumbo);
+COVERAGE_DEFINE(netlink_recv_mmap);
 COVERAGE_DEFINE(netlink_sent);
+COVERAGE_DEFINE(netlink_sent_mmap);
 
 /* Linux header file confusion causes this to be undefined. */
 #ifndef SOL_NETLINK
@@ -58,12 +61,22 @@  static void log_nlmsg(const char *function, int error,
 
 /* Netlink sockets. */
 
+struct nl_ring {
+    unsigned int head;
+    void *ring;
+};
+
 struct nl_sock {
     int fd;
     uint32_t next_seq;
     uint32_t pid;
     int protocol;
     unsigned int rcvbuf;        /* Receive buffer size (SO_RCVBUF). */
+    unsigned int frame_size;
+    unsigned int frame_nr;
+    size_t ring_size;
+    struct nl_ring tx_ring;
+    struct nl_ring rx_ring;
 };
 
 /* Compile-time limit on iovecs, so that we can allocate a maximum-size array
@@ -79,11 +92,51 @@  static int max_iovs;
 static int nl_pool_alloc(int protocol, struct nl_sock **sockp);
 static void nl_pool_release(struct nl_sock *);
 
+static int
+nl_sock_set_ring(struct nl_sock *sock)
+{
+    size_t block_size = 16 * getpagesize();
+    size_t ring_size;
+    void *ring;
+    struct nl_mmap_req req = {
+        .nm_block_size          = block_size,
+        .nm_block_nr            = 64,
+        .nm_frame_size          = 16384,
+    };
+
+    req.nm_frame_nr = req.nm_block_nr * block_size / req.nm_frame_size;
+
+    if (setsockopt(sock->fd, SOL_NETLINK, NETLINK_RX_RING, &req, sizeof(req)) < 0
+        || setsockopt(sock->fd, SOL_NETLINK, NETLINK_TX_RING, &req, sizeof(req)) < 0) {
+        VLOG_INFO("mmap netlink is not supported");
+        return 0;
+    }
+
+
+    ring_size = req.nm_block_nr * req.nm_block_size;
+    ring = mmap(NULL, 2 * ring_size, PROT_READ | PROT_WRITE,
+                MAP_SHARED, sock->fd, 0);
+    if (ring == MAP_FAILED) {
+        VLOG_ERR("netlink mmap: %s", ovs_strerror(errno));
+        return errno;
+    }
+
+    sock->frame_size = req.nm_frame_size;
+    sock->frame_nr = req.nm_frame_nr - 1;
+    sock->ring_size = ring_size;
+    sock->rx_ring.ring = ring;
+    sock->rx_ring.head = 0;
+    sock->tx_ring.ring = (char *) ring + ring_size;
+    sock->tx_ring.head = 0;
+
+    return 0;
+}
+
 /* Creates a new netlink socket for the given netlink 'protocol'
  * (NETLINK_ROUTE, NETLINK_GENERIC, ...).  Returns 0 and sets '*sockp' to the
  * new socket if successful, otherwise returns a positive errno value. */
 int
-nl_sock_create(int protocol, struct nl_sock **sockp)
+nl_sock_create(int protocol, struct nl_sock **sockp, bool use_mmap)
 {
     static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
     struct nl_sock *sock;
@@ -120,6 +173,7 @@  nl_sock_create(int protocol, struct nl_sock **sockp)
     }
     sock->protocol = protocol;
     sock->next_seq = 1;
+    sock->tx_ring.ring = sock->rx_ring.ring = NULL;
 
     rcvbuf = 1024 * 1024;
     if (setsockopt(sock->fd, SOL_SOCKET, SO_RCVBUFFORCE,
@@ -161,6 +215,11 @@  nl_sock_create(int protocol, struct nl_sock **sockp)
     }
     sock->pid = local.nl_pid;
 
+    if (use_mmap && (retval = nl_sock_set_ring(sock)) < 0) {
+        VLOG_ERR("failed to initialize memory mapped netlink socket");
+        goto error;
+    }
+
     *sockp = sock;
     return 0;
 
@@ -178,13 +237,19 @@  error:
     return retval;
 }
 
+static inline bool
+nl_sock_is_mapped(const struct nl_sock *sock)
+{
+   return sock->rx_ring.ring != NULL;
+}
+
 /* Creates a new netlink socket for the same protocol as 'src'.  Returns 0 and
  * sets '*sockp' to the new socket if successful, otherwise returns a positive
  * errno value.  */
 int
 nl_sock_clone(const struct nl_sock *src, struct nl_sock **sockp)
 {
-    return nl_sock_create(src->protocol, sockp);
+    return nl_sock_create(src->protocol, sockp, nl_sock_is_mapped(src));
 }
 
 /* Destroys netlink socket 'sock'. */
@@ -192,6 +257,9 @@  void
 nl_sock_destroy(struct nl_sock *sock)
 {
     if (sock) {
+        char *rx_ring = sock->rx_ring.ring;
+        if (rx_ring)
+            munmap(rx_ring, 2 * sock->ring_size);
         close(sock->fd);
         free(sock);
     }
@@ -242,6 +310,95 @@  nl_sock_leave_mcgroup(struct nl_sock *sock, unsigned int multicast_group)
     return 0;
 }
 
+enum ring_type {
+    RX_RING,
+    TX_RING,
+};
+
+static struct nl_ring *
+mmap_ring(struct nl_sock *sock, enum ring_type ring)
+{
+    return ring == RX_RING ? &sock->rx_ring : &sock->tx_ring;
+}
+
+static struct nl_mmap_hdr *
+mmap_frame(struct nl_sock *sock, enum ring_type ring)
+{
+    struct nl_ring *r = mmap_ring(sock, ring);
+    char *start = r->ring;
+
+    return (struct nl_mmap_hdr *)(start + r->head * sock->frame_size);
+}
+
+static void
+mmap_advance_ring(struct nl_sock *sock, enum ring_type ring)
+{
+    struct nl_ring *r = mmap_ring(sock, ring);
+
+    if (r->head != sock->frame_nr) {
+        r->head++;
+    } else {
+        r->head = 0;
+    }
+}
+
+static int
+nl_sock_send_linear(struct nl_sock *sock, const struct ofpbuf *msg,
+                    bool wait)
+{
+    int retval, error;
+
+    do {
+        retval = send(sock->fd, msg->data, msg->size, wait ? 0 : MSG_DONTWAIT);
+        error = retval < 0 ? errno : 0;
+    } while (error == EINTR);
+
+    return error;
+}
+
+static int
+nl_sock_send_mmap(struct nl_sock *sock, const struct ofpbuf *msg,
+                  bool wait)
+{
+    struct nl_mmap_hdr *hdr;
+    struct sockaddr_nl addr = {
+        .nl_family      = AF_NETLINK,
+    };
+    int retval, error;
+
+    if ((msg->size + NL_MMAP_HDRLEN) > sock->frame_size)
+        return nl_sock_send_linear(sock, msg, wait);
+
+    hdr = mmap_frame(sock, TX_RING);
+
+    if (hdr->nm_status != NL_MMAP_STATUS_UNUSED) {
+        /* No frame available. Block? */
+        if (wait) {
+            nl_sock_wait(sock, POLLOUT | POLLERR);
+            poll_block();
+        } else {
+            return EAGAIN;
+        }
+    }
+
+    memcpy((char *) hdr + NL_MMAP_HDRLEN, msg->data, msg->size);
+    hdr->nm_len     = msg->size;
+    hdr->nm_status  = NL_MMAP_STATUS_VALID;
+
+    mmap_advance_ring(sock, TX_RING);
+
+    do {
+        retval = sendto(sock->fd, NULL, 0, 0, (struct sockaddr *)&addr, sizeof(addr));
+        error = retval < 0 ? errno : 0;
+    } while (error == EINTR);
+
+    if (!error) {
+        COVERAGE_INC(netlink_sent_mmap);
+    }
+
+    return error;
+}
+
 static int
 nl_sock_send__(struct nl_sock *sock, const struct ofpbuf *msg,
                uint32_t nlmsg_seq, bool wait)
@@ -252,11 +409,13 @@  nl_sock_send__(struct nl_sock *sock, const struct ofpbuf *msg,
     nlmsg->nlmsg_len = msg->size;
     nlmsg->nlmsg_seq = nlmsg_seq;
     nlmsg->nlmsg_pid = sock->pid;
-    do {
-        int retval;
-        retval = send(sock->fd, msg->data, msg->size, wait ? 0 : MSG_DONTWAIT);
-        error = retval < 0 ? errno : 0;
-    } while (error == EINTR);
+
+    if (sock->tx_ring.ring) {
+        error = nl_sock_send_mmap(sock, msg, wait);
+    } else {
+        error = nl_sock_send_linear(sock, msg, wait);
+    }
+
     log_nlmsg(__func__, error, msg->data, msg->size, sock->protocol);
     if (!error) {
         COVERAGE_INC(netlink_sent);
@@ -297,26 +456,17 @@  nl_sock_send_seq(struct nl_sock *sock, const struct ofpbuf *msg,
 }
 
 static int
-nl_sock_recv__(struct nl_sock *sock, struct ofpbuf *buf, bool wait)
+nl_sock_recvmsg(struct nl_sock *sock, struct ofpbuf *buf, bool wait,
+                uint8_t *tail, size_t taillen)
 {
-    /* We can't accurately predict the size of the data to be received.  The
-     * caller is supposed to have allocated enough space in 'buf' to handle the
-     * "typical" case.  To handle exceptions, we make available enough space in
-     * 'tail' to allow Netlink messages to be up to 64 kB long (a reasonable
-     * figure since that's the maximum length of a Netlink attribute). */
-    struct nlmsghdr *nlmsghdr;
-    uint8_t tail[65536];
     struct iovec iov[2];
     struct msghdr msg;
-    ssize_t retval;
-
-    ovs_assert(buf->allocated >= sizeof *nlmsghdr);
-    ofpbuf_clear(buf);
+    int retval;
 
     iov[0].iov_base = buf->base;
     iov[0].iov_len = buf->allocated;
     iov[1].iov_base = tail;
-    iov[1].iov_len = sizeof tail;
+    iov[1].iov_len = taillen;
 
     memset(&msg, 0, sizeof msg);
     msg.msg_iov = iov;
@@ -342,21 +492,97 @@  nl_sock_recv__(struct nl_sock *sock, struct ofpbuf *buf, bool wait)
         return E2BIG;
     }
 
-    nlmsghdr = buf->data;
-    if (retval < sizeof *nlmsghdr
-        || nlmsghdr->nlmsg_len < sizeof *nlmsghdr
-        || nlmsghdr->nlmsg_len > retval) {
-        VLOG_ERR_RL(&rl, "received invalid nlmsg (%zd bytes < %zu)",
-                    retval, sizeof *nlmsghdr);
-        return EPROTO;
-    }
-
     buf->size = MIN(retval, buf->allocated);
     if (retval > buf->allocated) {
         COVERAGE_INC(netlink_recv_jumbo);
         ofpbuf_put(buf, tail, retval - buf->allocated);
     }
 
+    return 0;
+}
+
+static int
+nl_sock_recv_mmap(struct nl_sock *sock, struct ofpbuf *buf, bool wait,
+                  uint8_t *tail, size_t taillen)
+{
+    struct nl_mmap_hdr *hdr;
+    int retval = 0;
+
+restart:
+    hdr = mmap_frame(sock, RX_RING);
+
+    switch (hdr->nm_status) {
+    case NL_MMAP_STATUS_VALID:
+        if (hdr->nm_len == 0) {
+            /* error occured while constructing message */
+            hdr->nm_status = NL_MMAP_STATUS_UNUSED;
+            mmap_advance_ring(sock, RX_RING);
+            goto restart;
+        }
+
+        ofpbuf_put(buf, (char *) hdr + NL_MMAP_HDRLEN, hdr->nm_len);
+        COVERAGE_INC(netlink_recv_mmap);
+        break;
+
+    case NL_MMAP_STATUS_COPY:
+        retval = nl_sock_recvmsg(sock, buf, MSG_DONTWAIT, tail, taillen);
+        if (retval) {
+            return retval;
+        }
+        break;
+
+    case NL_MMAP_STATUS_UNUSED:
+    case NL_MMAP_STATUS_RESERVED:
+    default:
+        if (wait) {
+            nl_sock_wait(sock, POLLIN | POLLERR);
+            poll_block();
+            goto restart;
+        }
+
+        return EAGAIN;
+    }
+
+    hdr->nm_status = NL_MMAP_STATUS_UNUSED;
+    mmap_advance_ring(sock, RX_RING);
+
+    return retval;
+}
+
+static int
+nl_sock_recv__(struct nl_sock *sock, struct ofpbuf *buf, bool wait)
+{
+    /* We can't accurately predict the size of the data to be received.  The
+     * caller is supposed to have allocated enough space in 'buf' to handle the
+     * "typical" case.  To handle exceptions, we make available enough space in
+     * 'tail' to allow Netlink messages to be up to 64 kB long (a reasonable
+     * figure since that's the maximum length of a Netlink attribute). */
+    struct nlmsghdr *nlmsghdr;
+    uint8_t tail[65536];
+    int retval;
+
+    ovs_assert(buf->allocated >= sizeof *nlmsghdr);
+    ofpbuf_clear(buf);
+
+    if (sock->rx_ring.ring) {
+        retval = nl_sock_recv_mmap(sock, buf, wait, tail, sizeof(tail));
+    } else {
+        retval = nl_sock_recvmsg(sock, buf, wait, tail, sizeof(tail));
+    }
+
+    if (retval) {
+        return retval;
+    }
+
+    nlmsghdr = buf->data;
+    if (buf->size < sizeof *nlmsghdr
+        || nlmsghdr->nlmsg_len < sizeof *nlmsghdr
+        || nlmsghdr->nlmsg_len > buf->size) {
+        VLOG_ERR_RL(&rl, "received invalid nlmsg (%zd bytes < %zu)",
+                    buf->size, sizeof *nlmsghdr);
+        return EPROTO;
+    }
+
     log_nlmsg(__func__, 0, buf->data, buf->size, sock->protocol);
     COVERAGE_INC(netlink_received);
 
@@ -892,7 +1118,7 @@  do_lookup_genl_family(const char *name, struct nlattr **attrs,
     int error;
 
     *replyp = NULL;
-    error = nl_sock_create(NETLINK_GENERIC, &sock);
+    error = nl_sock_create(NETLINK_GENERIC, &sock, false);
     if (error) {
         return error;
     }
@@ -1028,7 +1254,7 @@  nl_pool_alloc(int protocol, struct nl_sock **sockp)
         *sockp = sock;
         return 0;
     } else {
-        return nl_sock_create(protocol, sockp);
+        return nl_sock_create(protocol, sockp, true);
     }
 }
 
diff --git a/lib/netlink-socket.h b/lib/netlink-socket.h
index 18db417..c85fd64 100644
--- a/lib/netlink-socket.h
+++ b/lib/netlink-socket.h
@@ -50,7 +50,7 @@  struct nl_sock;
 #endif
 
 /* Netlink sockets. */
-int nl_sock_create(int protocol, struct nl_sock **);
+int nl_sock_create(int protocol, struct nl_sock **, bool);
 int nl_sock_clone(const struct nl_sock *, struct nl_sock **);
 void nl_sock_destroy(struct nl_sock *);
 
diff --git a/utilities/nlmon.c b/utilities/nlmon.c
index 99b060c..cc6bc68 100644
--- a/utilities/nlmon.c
+++ b/utilities/nlmon.c
@@ -47,7 +47,7 @@  main(int argc OVS_UNUSED, char *argv[])
     set_program_name(argv[0]);
     vlog_set_levels(NULL, VLF_ANY_FACILITY, VLL_DBG);
 
-    error = nl_sock_create(NETLINK_ROUTE, &sock);
+    error = nl_sock_create(NETLINK_ROUTE, &sock, true);
     if (error) {
         ovs_fatal(error, "could not create rtnetlink socket");
     }