return fd;
}
-/* sndbuf should be set to a value lower than the tx queue
- * capacity of any destination network interface.
+/* 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 default, given a 1500 byte MTU.
+ * a good value, given a 1500 byte MTU.
*/
-#define TAP_DEFAULT_SNDBUF 1024*1024
+#define TAP_DEFAULT_SNDBUF 0
int tap_set_sndbuf(int fd, QemuOpts *opts)
{
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)
{