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-rw-r--r--net/tap-linux.c13
1 files changed, 9 insertions, 4 deletions
diff --git a/net/tap-linux.c b/net/tap-linux.c
index f7aa904..ff8cad0 100644
--- a/net/tap-linux.c
+++ b/net/tap-linux.c
@@ -82,12 +82,17 @@ 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)
{
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