net/netmap.c

/*
 * netmap access for qemu
 *
 * Copyright (c) 2012-2013 Luigi Rizzo
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */


#include <sys/ioctl.h>
#include <net/if.h>
#include <sys/mman.h>
#include <stdint.h>
#include <net/netmap.h>
#include <net/netmap_user.h>

#include "net/net.h"
#include "clients.h"
#include "sysemu/sysemu.h"
#include "qemu/error-report.h"
#include "qemu/iov.h"

/* Private netmap device info. */
typedef struct NetmapPriv {
    int                 fd;
    size_t              memsize;
    void                *mem;
    struct netmap_if    *nifp;
    struct netmap_ring  *rx;
    struct netmap_ring  *tx;
    char                fdname[PATH_MAX];        /* Normally "/dev/netmap". */
    char                ifname[IFNAMSIZ];
} NetmapPriv;

typedef struct NetmapState {
    NetClientState      nc;
    NetmapPriv          me;
    bool                read_poll;
    bool                write_poll;
    struct iovec        iov[IOV_MAX];
} NetmapState;

#define D(format, ...)                                          \
    do {                                                        \
        struct timeval __xxts;                                  \
        gettimeofday(&__xxts, NULL);                            \
        printf("%03d.%06d %s [%d] " format "\n",                \
                (int)__xxts.tv_sec % 1000, (int)__xxts.tv_usec, \
                __func__, __LINE__, ##__VA_ARGS__);         \
    } while (0)

/* Rate limited version of "D", lps indicates how many per second */
#define RD(lps, format, ...)                                    \
    do {                                                        \
        static int t0, __cnt;                                   \
        struct timeval __xxts;                                  \
        gettimeofday(&__xxts, NULL);                            \
        if (t0 != __xxts.tv_sec) {                              \
            t0 = __xxts.tv_sec;                                 \
            __cnt = 0;                                          \
        }                                                       \
        if (__cnt++ < lps) {                                    \
            D(format, ##__VA_ARGS__);                           \
        }                                                       \
    } while (0)


#ifndef __FreeBSD__
#define pkt_copy bcopy
#else
/* A fast copy routine only for multiples of 64 bytes, non overlapped. */
static inline void
pkt_copy(const void *_src, void *_dst, int l)
{
    const uint64_t *src = _src;
    uint64_t *dst = _dst;
    if (unlikely(l >= 1024)) {
        bcopy(src, dst, l);
        return;
    }
    for (; l > 0; l -= 64) {
        *dst++ = *src++;
        *dst++ = *src++;
        *dst++ = *src++;
        *dst++ = *src++;
        *dst++ = *src++;
        *dst++ = *src++;
        *dst++ = *src++;
        *dst++ = *src++;
    }
}
#endif /* __FreeBSD__ */

/*
 * Open a netmap device. We assume there is only one queue
 * (which is the case for the VALE bridge).
 */
static int netmap_open(NetmapPriv *me)
{
    int fd;
    int err;
    size_t l;
    struct nmreq req;

    me->fd = fd = open(me->fdname, O_RDWR);
    if (fd < 0) {
        error_report("Unable to open netmap device '%s' (%s)",
                        me->fdname, strerror(errno));
        return -1;
    }
    memset(&req, 0, sizeof(req));
    pstrcpy(req.nr_name, sizeof(req.nr_name), me->ifname);
    req.nr_ringid = NETMAP_NO_TX_POLL;
    req.nr_version = NETMAP_API;
    err = ioctl(fd, NIOCREGIF, &req);
    if (err) {
        error_report("Unable to register %s: %s", me->ifname, strerror(errno));
        goto error;
    }
    l = me->memsize = req.nr_memsize;

    me->mem = mmap(0, l, PROT_WRITE | PROT_READ, MAP_SHARED, fd, 0);
    if (me->mem == MAP_FAILED) {
        error_report("Unable to mmap netmap shared memory: %s",
                        strerror(errno));
        me->mem = NULL;
        goto error;
    }

    me->nifp = NETMAP_IF(me->mem, req.nr_offset);
    me->tx = NETMAP_TXRING(me->nifp, 0);
    me->rx = NETMAP_RXRING(me->nifp, 0);
    return 0;

error:
    close(me->fd);
    return -1;
}

/* Tell the event-loop if the netmap backend can send packets
   to the frontend. */
static int netmap_can_send(void *opaque)
{
    NetmapState *s = opaque;

    return qemu_can_send_packet(&s->nc);
}

static void netmap_send(void *opaque);
static void netmap_writable(void *opaque);

/* Set the event-loop handlers for the netmap backend. */
static void netmap_update_fd_handler(NetmapState *s)
{
    qemu_set_fd_handler2(s->me.fd,
                         s->read_poll  ? netmap_can_send : NULL,
                         s->read_poll  ? netmap_send     : NULL,
                         s->write_poll ? netmap_writable : NULL,
                         s);
}

/* Update the read handler. */
static void netmap_read_poll(NetmapState *s, bool enable)
{
    if (s->read_poll != enable) { /* Do nothing if not changed. */
        s->read_poll = enable;
        netmap_update_fd_handler(s);
    }
}

/* Update the write handler. */
static void netmap_write_poll(NetmapState *s, bool enable)
{
    if (s->write_poll != enable) {
        s->write_poll = enable;
        netmap_update_fd_handler(s);
    }
}

static void netmap_poll(NetClientState *nc, bool enable)
{
    NetmapState *s = DO_UPCAST(NetmapState, nc, nc);

    if (s->read_poll != enable || s->write_poll != enable) {
        s->read_poll = enable;
        s->read_poll = enable;
        netmap_update_fd_handler(s);
    }
}

/*
 * The fd_write() callback, invoked if the fd is marked as
 * writable after a poll. Unregister the handler and flush any
 * buffered packets.
 */
static void netmap_writable(void *opaque)
{
    NetmapState *s = opaque;

    netmap_write_poll(s, false);
    qemu_flush_queued_packets(&s->nc);
}

static ssize_t netmap_receive(NetClientState *nc,
      const uint8_t *buf, size_t size)
{
    NetmapState *s = DO_UPCAST(NetmapState, nc, nc);
    struct netmap_ring *ring = s->me.tx;
    uint32_t i;
    uint32_t idx;
    uint8_t *dst;

    if (unlikely(!ring)) {
        /* Drop. */
        return size;
    }

    if (unlikely(size > ring->nr_buf_size)) {
        RD(5, "[netmap_receive] drop packet of size %d > %d\n",
                                    (int)size, ring->nr_buf_size);
        return size;
    }

    if (ring->avail == 0) {
        /* No available slots in the netmap TX ring. */
        netmap_write_poll(s, true);
        return 0;
    }

    i = ring->cur;
    idx = ring->slot[i].buf_idx;
    dst = (uint8_t *)NETMAP_BUF(ring, idx);

    ring->slot[i].len = size;
    ring->slot[i].flags = 0;
    pkt_copy(buf, dst, size);
    ring->cur = NETMAP_RING_NEXT(ring, i);
    ring->avail--;
    ioctl(s->me.fd, NIOCTXSYNC, NULL);

    return size;
}

static ssize_t netmap_receive_iov(NetClientState *nc,
                    const struct iovec *iov, int iovcnt)
{
    NetmapState *s = DO_UPCAST(NetmapState, nc, nc);
    struct netmap_ring *ring = s->me.tx;
    uint32_t last;
    uint32_t idx;
    uint8_t *dst;
    int j;
    uint32_t i;
    uint32_t avail;

    if (unlikely(!ring)) {
        /* Drop the packet. */
        return iov_size(iov, iovcnt);
    }

    i = ring->cur;
    avail = ring->avail;

    if (avail < iovcnt) {
        /* Not enough netmap slots. */
        netmap_write_poll(s, true);
        return 0;
    }

    for (j = 0; j < iovcnt; j++) {
        int iov_frag_size = iov[j].iov_len;
        int offset = 0;
        int nm_frag_size;

        /* Split each iovec fragment over more netmap slots, if
           necessary. */
        while (iov_frag_size) {
            nm_frag_size = MIN(iov_frag_size, ring->nr_buf_size);

            if (unlikely(avail == 0)) {
                /* We run out of netmap slots while splitting the
                   iovec fragments. */
                netmap_write_poll(s, true);
                return 0;
            }

            idx = ring->slot[i].buf_idx;
            dst = (uint8_t *)NETMAP_BUF(ring, idx);

            ring->slot[i].len = nm_frag_size;
            ring->slot[i].flags = NS_MOREFRAG;
            pkt_copy(iov[j].iov_base + offset, dst, nm_frag_size);

            last = i;
            i = NETMAP_RING_NEXT(ring, i);
            avail--;

            offset += nm_frag_size;
            iov_frag_size -= nm_frag_size;
        }
    }
    /* The last slot must not have NS_MOREFRAG set. */
    ring->slot[last].flags &= ~NS_MOREFRAG;

    /* Now update ring->cur and ring->avail. */
    ring->cur = i;
    ring->avail = avail;

    ioctl(s->me.fd, NIOCTXSYNC, NULL);

    return iov_size(iov, iovcnt);
}

/* Complete a previous send (backend --> guest) and enable the
   fd_read callback. */
static void netmap_send_completed(NetClientState *nc, ssize_t len)
{
    NetmapState *s = DO_UPCAST(NetmapState, nc, nc);

    netmap_read_poll(s, true);
}

static void netmap_send(void *opaque)
{
    NetmapState *s = opaque;
    struct netmap_ring *ring = s->me.rx;

    /* Keep sending while there are available packets into the netmap
       RX ring and the forwarding path towards the peer is open. */
    while (ring->avail > 0 && qemu_can_send_packet(&s->nc)) {
        uint32_t i;
        uint32_t idx;
        bool morefrag;
        int iovcnt = 0;
        int iovsize;

        do {
            i = ring->cur;
            idx = ring->slot[i].buf_idx;
            morefrag = (ring->slot[i].flags & NS_MOREFRAG);
            s->iov[iovcnt].iov_base = (u_char *)NETMAP_BUF(ring, idx);
            s->iov[iovcnt].iov_len = ring->slot[i].len;
            iovcnt++;

            ring->cur = NETMAP_RING_NEXT(ring, i);
            ring->avail--;
        } while (ring->avail && morefrag);

        if (unlikely(!ring->avail && morefrag)) {
            RD(5, "[netmap_send] ran out of slots, with a pending"
                   "incomplete packet\n");
        }

        iovsize = qemu_sendv_packet_async(&s->nc, s->iov, iovcnt,
                                            netmap_send_completed);

        if (iovsize == 0) {
            /* The peer does not receive anymore. Packet is queued, stop
             * reading from the backend until netmap_send_completed()
             */
            netmap_read_poll(s, false);
            break;
        }
    }
}

/* Flush and close. */
static void netmap_cleanup(NetClientState *nc)
{
    NetmapState *s = DO_UPCAST(NetmapState, nc, nc);

    qemu_purge_queued_packets(nc);

    netmap_poll(nc, false);
    munmap(s->me.mem, s->me.memsize);
    close(s->me.fd);

    s->me.fd = -1;
}


/* NetClientInfo methods */
static NetClientInfo net_netmap_info = {
    .type = NET_CLIENT_OPTIONS_KIND_NETMAP,
    .size = sizeof(NetmapState),
    .receive = netmap_receive,
    .receive_iov = netmap_receive_iov,
    .poll = netmap_poll,
    .cleanup = netmap_cleanup,
};

/* The exported init function
 *
 * ... -net netmap,ifname="..."
 */
int net_init_netmap(const NetClientOptions *opts,
        const char *name, NetClientState *peer)
{
    const NetdevNetmapOptions *netmap_opts = opts->netmap;
    NetClientState *nc;
    NetmapPriv me;
    NetmapState *s;

    pstrcpy(me.fdname, sizeof(me.fdname),
        netmap_opts->has_devname ? netmap_opts->devname : "/dev/netmap");
    /* Set default name for the port if not supplied. */
    pstrcpy(me.ifname, sizeof(me.ifname), netmap_opts->ifname);
    if (netmap_open(&me)) {
        return -1;
    }
    /* Create the object. */
    nc = qemu_new_net_client(&net_netmap_info, peer, "netmap", name);
    s = DO_UPCAST(NetmapState, nc, nc);
    s->me = me;
    netmap_read_poll(s, true); /* Initially only poll for reads. */

    return 0;
}