Add cap reduction support to enable use as SUID

[qemu.git] / net / tap.c

/*
 * QEMU System Emulator
 *
 * Copyright (c) 2003-2008 Fabrice Bellard
 * Copyright (c) 2009 Red Hat, Inc.
 *
 * 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 "net/tap.h"

#include "config-host.h"

#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <net/if.h>

#include "net.h"
#include "sysemu.h"
#include "qemu-char.h"
#include "qemu-common.h"
#include "qemu-error.h"

#include "net/tap-linux.h"

#include "hw/vhost_net.h"

/* Maximum GSO packet size (64k) plus plenty of room for
 * the ethernet and virtio_net headers
 */
#define TAP_BUFSIZE (4096 + 65536)

typedef struct TAPState {
    VLANClientState nc;
    int fd;
    char down_script[1024];
    char down_script_arg[128];
    uint8_t buf[TAP_BUFSIZE];
    unsigned int read_poll : 1;
    unsigned int write_poll : 1;
    unsigned int using_vnet_hdr : 1;
    unsigned int has_ufo: 1;
    VHostNetState *vhost_net;
    unsigned host_vnet_hdr_len;
} TAPState;

static int launch_script(const char *setup_script, const char *ifname, int fd);

static int tap_can_send(void *opaque);
static void tap_send(void *opaque);
static void tap_writable(void *opaque);

static void tap_update_fd_handler(TAPState *s)
{
    qemu_set_fd_handler2(s->fd,
                         s->read_poll  ? tap_can_send : NULL,
                         s->read_poll  ? tap_send     : NULL,
                         s->write_poll ? tap_writable : NULL,
                         s);
}

static void tap_read_poll(TAPState *s, int enable)
{
    s->read_poll = !!enable;
    tap_update_fd_handler(s);
}

static void tap_write_poll(TAPState *s, int enable)
{
    s->write_poll = !!enable;
    tap_update_fd_handler(s);
}

static void tap_writable(void *opaque)
{
    TAPState *s = opaque;

    tap_write_poll(s, 0);

    qemu_flush_queued_packets(&s->nc);
}

static ssize_t tap_write_packet(TAPState *s, const struct iovec *iov, int iovcnt)
{
    ssize_t len;

    do {
        len = writev(s->fd, iov, iovcnt);
    } while (len == -1 && errno == EINTR);

    if (len == -1 && errno == EAGAIN) {
        tap_write_poll(s, 1);
        return 0;
    }

    return len;
}

static ssize_t tap_receive_iov(VLANClientState *nc, const struct iovec *iov,
                               int iovcnt)
{
    TAPState *s = DO_UPCAST(TAPState, nc, nc);
    const struct iovec *iovp = iov;
    struct iovec iov_copy[iovcnt + 1];
    struct virtio_net_hdr_mrg_rxbuf hdr = { };

    if (s->host_vnet_hdr_len && !s->using_vnet_hdr) {
        iov_copy[0].iov_base = &hdr;
        iov_copy[0].iov_len =  s->host_vnet_hdr_len;
        memcpy(&iov_copy[1], iov, iovcnt * sizeof(*iov));
        iovp = iov_copy;
        iovcnt++;
    }

    return tap_write_packet(s, iovp, iovcnt);
}

static ssize_t tap_receive_raw(VLANClientState *nc, const uint8_t *buf, size_t size)
{
    TAPState *s = DO_UPCAST(TAPState, nc, nc);
    struct iovec iov[2];
    int iovcnt = 0;
    struct virtio_net_hdr_mrg_rxbuf hdr = { };

    if (s->host_vnet_hdr_len) {
        iov[iovcnt].iov_base = &hdr;
        iov[iovcnt].iov_len  = s->host_vnet_hdr_len;
        iovcnt++;
    }

    iov[iovcnt].iov_base = (char *)buf;
    iov[iovcnt].iov_len  = size;
    iovcnt++;

    return tap_write_packet(s, iov, iovcnt);
}

static ssize_t tap_receive(VLANClientState *nc, const uint8_t *buf, size_t size)
{
    TAPState *s = DO_UPCAST(TAPState, nc, nc);
    struct iovec iov[1];

    if (s->host_vnet_hdr_len && !s->using_vnet_hdr) {
        return tap_receive_raw(nc, buf, size);
    }

    iov[0].iov_base = (char *)buf;
    iov[0].iov_len  = size;

    return tap_write_packet(s, iov, 1);
}

static int tap_can_send(void *opaque)
{
    TAPState *s = opaque;

    return qemu_can_send_packet(&s->nc);
}

#ifndef __sun__
ssize_t tap_read_packet(int tapfd, uint8_t *buf, int maxlen)
{
    return read(tapfd, buf, maxlen);
}
#endif

static void tap_send_completed(VLANClientState *nc, ssize_t len)
{
    TAPState *s = DO_UPCAST(TAPState, nc, nc);
    tap_read_poll(s, 1);
}

static void tap_send(void *opaque)
{
    TAPState *s = opaque;
    int size;

    do {
        uint8_t *buf = s->buf;

        size = tap_read_packet(s->fd, s->buf, sizeof(s->buf));
        if (size <= 0) {
            break;
        }

        if (s->host_vnet_hdr_len && !s->using_vnet_hdr) {
            buf  += s->host_vnet_hdr_len;
            size -= s->host_vnet_hdr_len;
        }

        size = qemu_send_packet_async(&s->nc, buf, size, tap_send_completed);
        if (size == 0) {
            tap_read_poll(s, 0);
        }
    } while (size > 0 && qemu_can_send_packet(&s->nc));
}

int tap_has_ufo(VLANClientState *nc)
{
    TAPState *s = DO_UPCAST(TAPState, nc, nc);

    assert(nc->info->type == NET_CLIENT_TYPE_TAP);

    return s->has_ufo;
}

int tap_has_vnet_hdr(VLANClientState *nc)
{
    TAPState *s = DO_UPCAST(TAPState, nc, nc);

    assert(nc->info->type == NET_CLIENT_TYPE_TAP);

    return !!s->host_vnet_hdr_len;
}

int tap_has_vnet_hdr_len(VLANClientState *nc, int len)
{
    TAPState *s = DO_UPCAST(TAPState, nc, nc);

    assert(nc->info->type == NET_CLIENT_TYPE_TAP);

    return tap_probe_vnet_hdr_len(s->fd, len);
}

void tap_set_vnet_hdr_len(VLANClientState *nc, int len)
{
    TAPState *s = DO_UPCAST(TAPState, nc, nc);

    assert(nc->info->type == NET_CLIENT_TYPE_TAP);
    assert(len == sizeof(struct virtio_net_hdr_mrg_rxbuf) ||
           len == sizeof(struct virtio_net_hdr));

    tap_fd_set_vnet_hdr_len(s->fd, len);
    s->host_vnet_hdr_len = len;
}

void tap_using_vnet_hdr(VLANClientState *nc, int using_vnet_hdr)
{
    TAPState *s = DO_UPCAST(TAPState, nc, nc);

    using_vnet_hdr = using_vnet_hdr != 0;

    assert(nc->info->type == NET_CLIENT_TYPE_TAP);
    assert(!!s->host_vnet_hdr_len == using_vnet_hdr);

    s->using_vnet_hdr = using_vnet_hdr;
}

void tap_set_offload(VLANClientState *nc, int csum, int tso4,
                     int tso6, int ecn, int ufo)
{
    TAPState *s = DO_UPCAST(TAPState, nc, nc);
    if (s->fd < 0) {
        return;
    }

    tap_fd_set_offload(s->fd, csum, tso4, tso6, ecn, ufo);
}

static void tap_cleanup(VLANClientState *nc)
{
    TAPState *s = DO_UPCAST(TAPState, nc, nc);

    if (s->vhost_net) {
        vhost_net_cleanup(s->vhost_net);
        s->vhost_net = NULL;
    }

    qemu_purge_queued_packets(nc);

    if (s->down_script[0])
        launch_script(s->down_script, s->down_script_arg, s->fd);

    tap_read_poll(s, 0);
    tap_write_poll(s, 0);
    close(s->fd);
    s->fd = -1;
}

static void tap_poll(VLANClientState *nc, bool enable)
{
    TAPState *s = DO_UPCAST(TAPState, nc, nc);
    tap_read_poll(s, enable);
    tap_write_poll(s, enable);
}

int tap_get_fd(VLANClientState *nc)
{
    TAPState *s = DO_UPCAST(TAPState, nc, nc);
    assert(nc->info->type == NET_CLIENT_TYPE_TAP);
    return s->fd;
}

/* fd support */

static NetClientInfo net_tap_info = {
    .type = NET_CLIENT_TYPE_TAP,
    .size = sizeof(TAPState),
    .receive = tap_receive,
    .receive_raw = tap_receive_raw,
    .receive_iov = tap_receive_iov,
    .poll = tap_poll,
    .cleanup = tap_cleanup,
};

static TAPState *net_tap_fd_init(VLANState *vlan,
                                 const char *model,
                                 const char *name,
                                 int fd,
                                 int vnet_hdr)
{
    VLANClientState *nc;
    TAPState *s;

    nc = qemu_new_net_client(&net_tap_info, vlan, NULL, model, name);

    s = DO_UPCAST(TAPState, nc, nc);

    s->fd = fd;
    s->host_vnet_hdr_len = vnet_hdr ? sizeof(struct virtio_net_hdr) : 0;
    s->using_vnet_hdr = 0;
    s->has_ufo = tap_probe_has_ufo(s->fd);
    tap_set_offload(&s->nc, 0, 0, 0, 0, 0);
    tap_read_poll(s, 1);
    s->vhost_net = NULL;
    return s;
}

static int launch_script(const char *setup_script, const char *ifname, int fd)
{
    int pid, status;
    char *args[3];
    char **parg;

    /* try to launch network script */
    pid = fork();
    if (pid == 0) {
        int open_max = sysconf(_SC_OPEN_MAX), i;

        for (i = 0; i < open_max; i++) {
            if (i != STDIN_FILENO &&
                i != STDOUT_FILENO &&
                i != STDERR_FILENO &&
                i != fd) {
                close(i);
            }
        }
        parg = args;
        *parg++ = (char *)setup_script;
        *parg++ = (char *)ifname;
        *parg = NULL;
        execv(setup_script, args);
        _exit(1);
    } else if (pid > 0) {
        while (waitpid(pid, &status, 0) != pid) {
            /* loop */
        }

        if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
            return 0;
        }
    }
    fprintf(stderr, "%s: could not launch network script\n", setup_script);
    return -1;
}

static int net_tap_init(QemuOpts *opts, int *vnet_hdr)
{
    int fd, vnet_hdr_required;
    char ifname[128] = {0,};
    const char *setup_script;

    if (qemu_opt_get(opts, "ifname")) {
        pstrcpy(ifname, sizeof(ifname), qemu_opt_get(opts, "ifname"));
    }

    *vnet_hdr = qemu_opt_get_bool(opts, "vnet_hdr", 1);
    if (qemu_opt_get(opts, "vnet_hdr")) {
        vnet_hdr_required = *vnet_hdr;
    } else {
        vnet_hdr_required = 0;
    }

    TFR(fd = tap_open(ifname, sizeof(ifname), vnet_hdr, vnet_hdr_required));
    if (fd < 0) {
        return -1;
    }

    setup_script = qemu_opt_get(opts, "script");
    if (setup_script &&
        setup_script[0] != '\0' &&
        strcmp(setup_script, "no") != 0 &&
        launch_script(setup_script, ifname, fd)) {
        close(fd);
        return -1;
    }

    qemu_opt_set(opts, "ifname", ifname);

    return fd;
}

int net_init_tap(QemuOpts *opts, Monitor *mon, const char *name, VLANState *vlan)
{
    TAPState *s;
    int fd, vnet_hdr = 0;

    if (qemu_opt_get(opts, "fd")) {
        if (qemu_opt_get(opts, "ifname") ||
            qemu_opt_get(opts, "script") ||
            qemu_opt_get(opts, "downscript") ||
            qemu_opt_get(opts, "vnet_hdr")) {
            error_report("ifname=, script=, downscript= and vnet_hdr= is invalid with fd=");
            return -1;
        }

        fd = net_handle_fd_param(mon, qemu_opt_get(opts, "fd"));
        if (fd == -1) {
            return -1;
        }

        fcntl(fd, F_SETFL, O_NONBLOCK);

        vnet_hdr = tap_probe_vnet_hdr(fd);
    } else {
        if (!qemu_opt_get(opts, "script")) {
            qemu_opt_set(opts, "script", DEFAULT_NETWORK_SCRIPT);
        }

        if (!qemu_opt_get(opts, "downscript")) {
            qemu_opt_set(opts, "downscript", DEFAULT_NETWORK_DOWN_SCRIPT);
        }

        fd = net_tap_init(opts, &vnet_hdr);
        if (fd == -1) {
            return -1;
        }
    }

    s = net_tap_fd_init(vlan, "tap", name, fd, vnet_hdr);
    if (!s) {
        close(fd);
        return -1;
    }

    if (tap_set_sndbuf(s->fd, opts) < 0) {
        return -1;
    }

    if (qemu_opt_get(opts, "fd")) {
        snprintf(s->nc.info_str, sizeof(s->nc.info_str), "fd=%d", fd);
    } else {
        const char *ifname, *script, *downscript;

        ifname     = qemu_opt_get(opts, "ifname");
        script     = qemu_opt_get(opts, "script");
        downscript = qemu_opt_get(opts, "downscript");

        snprintf(s->nc.info_str, sizeof(s->nc.info_str),
                 "ifname=%s,script=%s,downscript=%s",
                 ifname, script, downscript);

        if (strcmp(downscript, "no") != 0) {
            snprintf(s->down_script, sizeof(s->down_script), "%s", downscript);
            snprintf(s->down_script_arg, sizeof(s->down_script_arg), "%s", ifname);
        }
    }

    if (qemu_opt_get_bool(opts, "vhost", !!qemu_opt_get(opts, "vhostfd") ||
                          qemu_opt_get_bool(opts, "vhostforce", false))) {
        int vhostfd, r;
        bool force = qemu_opt_get_bool(opts, "vhostforce", false);
        if (qemu_opt_get(opts, "vhostfd")) {
            r = net_handle_fd_param(mon, qemu_opt_get(opts, "vhostfd"));
            if (r == -1) {
                return -1;
            }
            vhostfd = r;
        } else {
            vhostfd = -1;
        }
        s->vhost_net = vhost_net_init(&s->nc, vhostfd, force);
        if (!s->vhost_net) {
            error_report("vhost-net requested but could not be initialized");
            return -1;
        }
    } else if (qemu_opt_get(opts, "vhostfd")) {
        error_report("vhostfd= is not valid without vhost");
        return -1;
    }

    return 0;
}

VHostNetState *tap_get_vhost_net(VLANClientState *nc)
{
    TAPState *s = DO_UPCAST(TAPState, nc, nc);
    assert(nc->info->type == NET_CLIENT_TYPE_TAP);
    return s->vhost_net;
}