Archipelago » qemu

/*

 * QEMU Bridge Helper

 *

 * Copyright IBM, Corp. 2011

 *

 * Authors:

 * Anthony Liguori   <aliguori@us.ibm.com>

 * Richa Marwaha     <rmarwah@linux.vnet.ibm.com>

 * Corey Bryant      <coreyb@linux.vnet.ibm.com>

 *

 * This work is licensed under the terms of the GNU GPL, version 2.  See

 * the COPYING file in the top-level directory.

 *

 */

#include "config-host.h"

#include <stdio.h>

#include <errno.h>

#include <fcntl.h>

#include <unistd.h>

#include <string.h>

#include <stdlib.h>

#include <stdbool.h>

#include <ctype.h>

#include <sys/types.h>

#include <sys/ioctl.h>

#include <sys/socket.h>

#include <sys/un.h>

#include <sys/prctl.h>

#include <net/if.h>

#include <linux/sockios.h>

#include "net/tap-linux.h"

static void usage(void)

{

    fprintf(stderr,

            "Usage: qemu-bridge-helper [--use-vnet] --br=bridge --fd=unixfd\n");

}

static bool has_vnet_hdr(int fd)

{

    unsigned int features = 0;

    if (ioctl(fd, TUNGETFEATURES, &features) == -1) {

        return false;

    }

    if (!(features & IFF_VNET_HDR)) {

        return false;

    }

    return true;

}

static void prep_ifreq(struct ifreq *ifr, const char *ifname)

{

    memset(ifr, 0, sizeof(*ifr));

    snprintf(ifr->ifr_name, IFNAMSIZ, "%s", ifname);

}

static int send_fd(int c, int fd)

{

    char msgbuf[CMSG_SPACE(sizeof(fd))];

    struct msghdr msg = {

        .msg_control = msgbuf,

        .msg_controllen = sizeof(msgbuf),

    };

    struct cmsghdr *cmsg;

    struct iovec iov;

    char req[1] = { 0x00 };

    cmsg = CMSG_FIRSTHDR(&msg);

    cmsg->cmsg_level = SOL_SOCKET;

    cmsg->cmsg_type = SCM_RIGHTS;

    cmsg->cmsg_len = CMSG_LEN(sizeof(fd));

    msg.msg_controllen = cmsg->cmsg_len;

    iov.iov_base = req;

    iov.iov_len = sizeof(req);

    msg.msg_iov = &iov;

    msg.msg_iovlen = 1;

    memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd));

    return sendmsg(c, &msg, 0);

}

int main(int argc, char **argv)

{

    struct ifreq ifr;

    int fd, ctlfd, unixfd = -1;

    int use_vnet = 0;

    int mtu;

    const char *bridge = NULL;

    char iface[IFNAMSIZ];

    int index;

    int ret = EXIT_SUCCESS;

    /* parse arguments */

    for (index = 1; index < argc; index++) {

        if (strcmp(argv[index], "--use-vnet") == 0) {

            use_vnet = 1;

        } else if (strncmp(argv[index], "--br=", 5) == 0) {

            bridge = &argv[index][5];

        } else if (strncmp(argv[index], "--fd=", 5) == 0) {

            unixfd = atoi(&argv[index][5]);

        } else {

            usage();

            return EXIT_FAILURE;

        }

    }

    if (bridge == NULL || unixfd == -1) {

        usage();

        return EXIT_FAILURE;

    }

    /* open a socket to use to control the network interfaces */

    ctlfd = socket(AF_INET, SOCK_STREAM, 0);

    if (ctlfd == -1) {

        fprintf(stderr, "failed to open control socket: %s\n", strerror(errno));

        ret = EXIT_FAILURE;

        goto cleanup;

    }

    /* open the tap device */

    fd = open("/dev/net/tun", O_RDWR);

    if (fd == -1) {

        fprintf(stderr, "failed to open /dev/net/tun: %s\n", strerror(errno));

        ret = EXIT_FAILURE;

        goto cleanup;

    }

    /* request a tap device, disable PI, and add vnet header support if

     * requested and it's available. */

    prep_ifreq(&ifr, "tap%d");

    ifr.ifr_flags = IFF_TAP|IFF_NO_PI;

    if (use_vnet && has_vnet_hdr(fd)) {

        ifr.ifr_flags |= IFF_VNET_HDR;

    }

    if (ioctl(fd, TUNSETIFF, &ifr) == -1) {

        fprintf(stderr, "failed to create tun device: %s\n", strerror(errno));

        ret = EXIT_FAILURE;

        goto cleanup;

    }

    /* save tap device name */

    snprintf(iface, sizeof(iface), "%s", ifr.ifr_name);

    /* get the mtu of the bridge */

    prep_ifreq(&ifr, bridge);

    if (ioctl(ctlfd, SIOCGIFMTU, &ifr) == -1) {

        fprintf(stderr, "failed to get mtu of bridge `%s': %s\n",

                bridge, strerror(errno));

        ret = EXIT_FAILURE;

        goto cleanup;

    }

    /* save mtu */

    mtu = ifr.ifr_mtu;

    /* set the mtu of the interface based on the bridge */

    prep_ifreq(&ifr, iface);

    ifr.ifr_mtu = mtu;

    if (ioctl(ctlfd, SIOCSIFMTU, &ifr) == -1) {

        fprintf(stderr, "failed to set mtu of device `%s' to %d: %s\n",

                iface, mtu, strerror(errno));

        ret = EXIT_FAILURE;

        goto cleanup;

    }

    /* add the interface to the bridge */

    prep_ifreq(&ifr, bridge);

    ifr.ifr_ifindex = if_nametoindex(iface);

    if (ioctl(ctlfd, SIOCBRADDIF, &ifr) == -1) {

        fprintf(stderr, "failed to add interface `%s' to bridge `%s': %s\n",

                iface, bridge, strerror(errno));

        ret = EXIT_FAILURE;

        goto cleanup;

    }

    /* bring the interface up */

    prep_ifreq(&ifr, iface);

    if (ioctl(ctlfd, SIOCGIFFLAGS, &ifr) == -1) {

        fprintf(stderr, "failed to get interface flags for `%s': %s\n",

                iface, strerror(errno));

        ret = EXIT_FAILURE;

        goto cleanup;

    }

    ifr.ifr_flags |= IFF_UP;

    if (ioctl(ctlfd, SIOCSIFFLAGS, &ifr) == -1) {

        fprintf(stderr, "failed to bring up interface `%s': %s\n",

                iface, strerror(errno));

        ret = EXIT_FAILURE;

        goto cleanup;

    }

    /* write fd to the domain socket */

    if (send_fd(unixfd, fd) == -1) {

        fprintf(stderr, "failed to write fd to unix socket: %s\n",

                strerror(errno));

        ret = EXIT_FAILURE;

        goto cleanup;

    }

    /* ... */

    /* profit! */

cleanup:

    return ret;

}