qemu/net/tap-linux.c
Michael S. Tsirkin f157ed202e tap: safe sndbuf default
With current sndbuf default value, a blocked
target guest can prevent another guest from
transmitting any packets. While current
sndbuf value (1M) is reported to help some
UDP based workloads, the default should
be safe (0).

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2011-02-01 16:50:44 -06:00

196 lines
5.4 KiB
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 "net/tap-linux.h"
#include <net/if.h>
#include <sys/ioctl.h>
#include "sysemu.h"
#include "qemu-common.h"
#include "qemu-error.h"
#define PATH_NET_TUN "/dev/net/tun"
int tap_open(char *ifname, int ifname_size, int *vnet_hdr, int vnet_hdr_required)
{
struct ifreq ifr;
int fd, ret;
TFR(fd = open(PATH_NET_TUN, O_RDWR));
if (fd < 0) {
error_report("could not open %s: %m", PATH_NET_TUN);
return -1;
}
memset(&ifr, 0, sizeof(ifr));
ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
if (*vnet_hdr) {
unsigned int features;
if (ioctl(fd, TUNGETFEATURES, &features) == 0 &&
features & IFF_VNET_HDR) {
*vnet_hdr = 1;
ifr.ifr_flags |= IFF_VNET_HDR;
} else {
*vnet_hdr = 0;
}
if (vnet_hdr_required && !*vnet_hdr) {
error_report("vnet_hdr=1 requested, but no kernel "
"support for IFF_VNET_HDR available");
close(fd);
return -1;
}
}
if (ifname[0] != '\0')
pstrcpy(ifr.ifr_name, IFNAMSIZ, ifname);
else
pstrcpy(ifr.ifr_name, IFNAMSIZ, "tap%d");
ret = ioctl(fd, TUNSETIFF, (void *) &ifr);
if (ret != 0) {
error_report("could not configure %s (%s): %m", PATH_NET_TUN, ifr.ifr_name);
close(fd);
return -1;
}
pstrcpy(ifname, ifname_size, ifr.ifr_name);
fcntl(fd, F_SETFL, O_NONBLOCK);
return fd;
}
/* sndbuf implements a kind of flow control for tap.
* Unfortunately when it's enabled, and packets are sent
* to other guests on the same host, the receiver
* can lock up the transmitter indefinitely.
*
* To avoid packet loss, sndbuf should be set to a value lower than the tx
* queue capacity of any destination network interface.
* Ethernet NICs generally have txqueuelen=1000, so 1Mb is
* a good value, given a 1500 byte MTU.
*/
#define TAP_DEFAULT_SNDBUF 0
int tap_set_sndbuf(int fd, QemuOpts *opts)
{
int sndbuf;
sndbuf = qemu_opt_get_size(opts, "sndbuf", TAP_DEFAULT_SNDBUF);
if (!sndbuf) {
sndbuf = INT_MAX;
}
if (ioctl(fd, TUNSETSNDBUF, &sndbuf) == -1 && qemu_opt_get(opts, "sndbuf")) {
error_report("TUNSETSNDBUF ioctl failed: %s", strerror(errno));
return -1;
}
return 0;
}
int tap_probe_vnet_hdr(int fd)
{
struct ifreq ifr;
if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
error_report("TUNGETIFF ioctl() failed: %s", strerror(errno));
return 0;
}
return ifr.ifr_flags & IFF_VNET_HDR;
}
int tap_probe_has_ufo(int fd)
{
unsigned offload;
offload = TUN_F_CSUM | TUN_F_UFO;
if (ioctl(fd, TUNSETOFFLOAD, offload) < 0)
return 0;
return 1;
}
/* Verify that we can assign given length */
int tap_probe_vnet_hdr_len(int fd, int len)
{
int orig;
if (ioctl(fd, TUNGETVNETHDRSZ, &orig) == -1) {
return 0;
}
if (ioctl(fd, TUNSETVNETHDRSZ, &len) == -1) {
return 0;
}
/* Restore original length: we can't handle failure. */
if (ioctl(fd, TUNSETVNETHDRSZ, &orig) == -1) {
fprintf(stderr, "TUNGETVNETHDRSZ ioctl() failed: %s. Exiting.\n",
strerror(errno));
assert(0);
return -errno;
}
return 1;
}
void tap_fd_set_vnet_hdr_len(int fd, int len)
{
if (ioctl(fd, TUNSETVNETHDRSZ, &len) == -1) {
fprintf(stderr, "TUNSETVNETHDRSZ ioctl() failed: %s. Exiting.\n",
strerror(errno));
assert(0);
}
}
void tap_fd_set_offload(int fd, int csum, int tso4,
int tso6, int ecn, int ufo)
{
unsigned int offload = 0;
/* Check if our kernel supports TUNSETOFFLOAD */
if (ioctl(fd, TUNSETOFFLOAD, 0) != 0 && errno == EINVAL) {
return;
}
if (csum) {
offload |= TUN_F_CSUM;
if (tso4)
offload |= TUN_F_TSO4;
if (tso6)
offload |= TUN_F_TSO6;
if ((tso4 || tso6) && ecn)
offload |= TUN_F_TSO_ECN;
if (ufo)
offload |= TUN_F_UFO;
}
if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
offload &= ~TUN_F_UFO;
if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
fprintf(stderr, "TUNSETOFFLOAD ioctl() failed: %s\n",
strerror(errno));
}
}
}