spice-qemu-char: write to chardev whatever amount it can read

[qemu.git] / net / tap-linux.c

diff --git a/net/tap-linux.c b/net/tap-linux.c
index b6f1fad5e44fd33e02e4be3367754c0c0ff6bb1f..c6521bec344bec393b6204f9b9a9afb722daf363 100644 (file)
--- a/net/tap-linux.c
+++ b/net/tap-linux.c
@@ -31,15 +31,18 @@
 
 #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("/dev/net/tun", O_RDWR));
+    TFR(fd = open(PATH_NET_TUN, O_RDWR));
     if (fd < 0) {
-        fprintf(stderr, "warning: could not open /dev/net/tun: no virtual network emulation\n");
+        error_report("could not open %s: %m", PATH_NET_TUN);
         return -1;
     }
     memset(&ifr, 0, sizeof(ifr));
@@ -52,11 +55,13 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr, int vnet_hdr_required
             features & IFF_VNET_HDR) {
             *vnet_hdr = 1;
             ifr.ifr_flags |= IFF_VNET_HDR;
+        } else {
+            *vnet_hdr = 0;
         }
 
         if (vnet_hdr_required && !*vnet_hdr) {
-            qemu_error("vnet_hdr=1 requested, but no kernel "
-                       "support for IFF_VNET_HDR available");
+            error_report("vnet_hdr=1 requested, but no kernel "
+                         "support for IFF_VNET_HDR available");
             close(fd);
             return -1;
         }
@@ -68,7 +73,11 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr, int vnet_hdr_required
         pstrcpy(ifr.ifr_name, IFNAMSIZ, "tap%d");
     ret = ioctl(fd, TUNSETIFF, (void *) &ifr);
     if (ret != 0) {
-        fprintf(stderr, "warning: could not configure /dev/net/tun: no virtual network emulation\n");
+        if (ifname[0] != '\0') {
+            error_report("could not configure %s (%s): %m", PATH_NET_TUN, ifr.ifr_name);
+        } else {
+            error_report("could not configure %s: %m", PATH_NET_TUN);
+        }
         close(fd);
         return -1;
     }
@@ -77,24 +86,32 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr, int vnet_hdr_required
     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)
+int tap_set_sndbuf(int fd, const NetdevTapOptions *tap)
 {
     int sndbuf;
 
-    sndbuf = qemu_opt_get_size(opts, "sndbuf", TAP_DEFAULT_SNDBUF);
+    sndbuf = !tap->has_sndbuf       ? TAP_DEFAULT_SNDBUF :
+             tap->sndbuf > INT_MAX  ? INT_MAX :
+             tap->sndbuf;
+
     if (!sndbuf) {
         sndbuf = INT_MAX;
     }
 
-    if (ioctl(fd, TUNSETSNDBUF, &sndbuf) == -1 && qemu_opt_get(opts, "sndbuf")) {
-        qemu_error("TUNSETSNDBUF ioctl failed: %s\n", strerror(errno));
+    if (ioctl(fd, TUNSETSNDBUF, &sndbuf) == -1 && tap->has_sndbuf) {
+        error_report("TUNSETSNDBUF ioctl failed: %s", strerror(errno));
         return -1;
     }
     return 0;
@@ -105,18 +122,64 @@ int tap_probe_vnet_hdr(int fd)
     struct ifreq ifr;
 
     if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
-        qemu_error("TUNGETIFF ioctl() failed: %s\n", strerror(errno));
+        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)