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authorMohsin Kazmi <sykazmi@cisco.com>2020-07-06 18:03:41 +0000
committerBenoƮt Ganne <bganne@cisco.com>2020-07-07 14:44:53 +0000
commit4834a66b7b3ef73e486c40ea9d8e36cc2e09c473 (patch)
tree37c468c21923b97a3cf1205ba26c9a5fc9f33fcc
parent190983de619e340a148cff8b1b1d8c9e0cd8c95a (diff)
tap: fix the tun sndbuf value for kernel 4.20 and later
Type: fix From kernel 4.20, xdp support has been added in tun_sendmsg. If sndbuf == INT_MAX, kernel executes xdp data path for tun driver which assumes packets are ethernet frames. This patch is avoiding the xdp data path in kernel by setting the sendbuf value < INT_MAX. Signed-off-by: Mohsin Kazmi <sykazmi@cisco.com> Change-Id: Ia4aa54b177b96d56a2d513d18d26ca01d5b88929
-rw-r--r--src/vnet/devices/tap/tap.c20
1 files changed, 16 insertions, 4 deletions
diff --git a/src/vnet/devices/tap/tap.c b/src/vnet/devices/tap/tap.c
index cbdbbe9e..fa5eef1 100644
--- a/src/vnet/devices/tap/tap.c
+++ b/src/vnet/devices/tap/tap.c
@@ -139,7 +139,7 @@ tap_create_if (vlib_main_t * vm, tap_create_if_args_t * args)
tap_main_t *tm = &tap_main;
vnet_sw_interface_t *sw;
vnet_hw_interface_t *hw;
- int i, j, num_vhost_queues;
+ int i, num_vhost_queues;
int old_netns_fd = -1;
struct ifreq ifr = {.ifr_flags = IFF_NO_PI | IFF_VNET_HDR };
struct ifreq get_ifr = {.ifr_flags = 0 };
@@ -151,6 +151,7 @@ tap_create_if (vlib_main_t * vm, tap_create_if_args_t * args)
int tfd = -1, qfd = -1, vfd = -1, nfd = -1;
char *host_if_name = 0;
unsigned int offload = 0;
+ int sndbuf = 0;
if (args->id != ~0)
{
@@ -179,11 +180,22 @@ tap_create_if (vlib_main_t * vm, tap_create_if_args_t * args)
{
vif->type = VIRTIO_IF_TYPE_TUN;
ifr.ifr_flags |= IFF_TUN;
+
+ /*
+ * From kernel 4.20, xdp support has been added in tun_sendmsg.
+ * If sndbuf == INT_MAX, vhost batches the packet and processes
+ * them using xdp data path for tun driver. It assumes packets
+ * are ethernet frames (It needs to be fixed).
+ * To avoid xdp data path in tun driver, sndbuf value should
+ * be < INT_MAX.
+ */
+ sndbuf = INT_MAX - 1;
}
else
{
vif->type = VIRTIO_IF_TYPE_TAP;
ifr.ifr_flags |= IFF_TAP;
+ sndbuf = INT_MAX;
}
vif->dev_instance = vif - vim->interfaces;
@@ -330,9 +342,9 @@ tap_create_if (vlib_main_t * vm, tap_create_if_args_t * args)
vif->tap_fds[i], hdrsz);
_IOCTL (vif->tap_fds[i], TUNSETVNETHDRSZ, &hdrsz);
- j = INT_MAX;
- tap_log_dbg (vif, "TUNSETSNDBUF: fd %d sndbuf %d", vif->tap_fds[i], j);
- _IOCTL (vif->tap_fds[i], TUNSETSNDBUF, &j);
+ tap_log_dbg (vif, "TUNSETSNDBUF: fd %d sndbuf %d", vif->tap_fds[i],
+ sndbuf);
+ _IOCTL (vif->tap_fds[i], TUNSETSNDBUF, &sndbuf);
tap_log_dbg (vif, "TUNSETOFFLOAD: fd %d offload 0x%lx", vif->tap_fds[i],
offload);