MTU: set interface mtu tap

This patch introduces standard command line 'set interface mtu' for setting the MTU
for tap devices. It allows user to set the mtu in between 68 to 65535 bytes
aligned to what linux kernel supports for tun/tap devices.

Right now tapcli set the same MTU size for each tap interface. But it should be set
and configure to per interface rather than per tap instance.

Change-Id: I81b7f3ad95ca56d585907ff8f51d9935a428e01b
Signed-off-by: Mohsin Kazmi <sykazmi@cisco.com>

1 files changed, 39 insertions, 26 deletions

diff --git a/vnet/vnet/unix/tapcli.c b/vnet/vnet/unix/tapcli.c
index d17d09dcbdb..596f8d184ab 100644
--- a/vnet/vnet/unix/tapcli.c
+++ b/vnet/vnet/unix/tapcli.c
@@ -515,39 +515,48 @@ static u32 tapcli_flag_change (vnet_main_t * vnm,
 {
   tapcli_main_t *tm = &tapcli_main;
   tapcli_interface_t *ti;
-  struct ifreq ifr;
-  u32 want_promisc;
-
-  ti = vec_elt_at_index (tm->tapcli_interfaces, hw->dev_instance);
 
-  clib_memcpy (&ifr, &ti->ifr, sizeof (ifr));
+   ti = vec_elt_at_index (tm->tapcli_interfaces, hw->dev_instance);
 
-  /* get flags, modify to bring up interface... */
-  if (ioctl (ti->provision_fd, SIOCGIFFLAGS, &ifr) < 0)
+  if (flags & ETHERNET_INTERFACE_FLAG_MTU)
     {
-      clib_unix_warning ("Couldn't get interface flags for %s", hw->name);
-      return 0;
+      const uword buffer_size = VLIB_BUFFER_DATA_SIZE;
+      tm->mtu_bytes = hw->max_packet_bytes;
+      tm->mtu_buffers = (tm->mtu_bytes + (buffer_size - 1)) / buffer_size;
     }
+   else
+    {
+      struct ifreq ifr;
+      u32 want_promisc;
 
-  want_promisc = (flags & ETHERNET_INTERFACE_FLAG_ACCEPT_ALL) != 0;
+      memcpy (&ifr, &ti->ifr, sizeof (ifr));
 
-  if (want_promisc == ti->is_promisc)
-    return 0;
+      /* get flags, modify to bring up interface... */
+      if (ioctl (ti->provision_fd, SIOCGIFFLAGS, &ifr) < 0)
+        {
+          clib_unix_warning ("Couldn't get interface flags for %s", hw->name);
+          return 0;
+        }
 
+      want_promisc = (flags & ETHERNET_INTERFACE_FLAG_ACCEPT_ALL) != 0;
 
-  if (flags & ETHERNET_INTERFACE_FLAG_ACCEPT_ALL)
-    ifr.ifr_flags |= IFF_PROMISC;
-  else
-    ifr.ifr_flags &= ~(IFF_PROMISC);
+      if (want_promisc == ti->is_promisc)
+        return 0;
 
-  /* get flags, modify to bring up interface... */
-  if (ioctl (ti->provision_fd, SIOCSIFFLAGS, &ifr) < 0)
-    {
-      clib_unix_warning ("Couldn't set interface flags for %s", hw->name);
-      return 0;
-    }
+      if (flags & ETHERNET_INTERFACE_FLAG_ACCEPT_ALL)
+        ifr.ifr_flags |= IFF_PROMISC;
+      else
+        ifr.ifr_flags &= ~(IFF_PROMISC);
 
-  ti->is_promisc = want_promisc;
+      /* get flags, modify to bring up interface... */
+      if (ioctl (ti->provision_fd, SIOCSIFFLAGS, &ifr) < 0)
+        {
+          clib_unix_warning ("Couldn't set interface flags for %s", hw->name);
+          return 0;
+        }
+
+      ti->is_promisc = want_promisc;
+    }
 
   return 0;
 }
@@ -788,7 +797,9 @@ int vnet_tap_connect (vlib_main_t * vm, u8 * intfc_name, u8 *hwaddr_arg,
   {
     vnet_hw_interface_t * hw;
     hw = vnet_get_hw_interface (tm->vnet_main, ti->hw_if_index);
-    hw->max_l3_packet_bytes[VLIB_RX] = hw->max_l3_packet_bytes[VLIB_TX] = tm->mtu_bytes - sizeof(ethernet_header_t);
+    hw->min_supported_packet_bytes = TAP_MTU_MIN;
+    hw->max_supported_packet_bytes = TAP_MTU_MAX;
+    hw->max_l3_packet_bytes[VLIB_RX] = hw->max_l3_packet_bytes[VLIB_TX] = hw->max_supported_packet_bytes - sizeof(ethernet_header_t);
     ti->sw_if_index = hw->sw_if_index;
     if (sw_if_indexp)
       *sw_if_indexp = hw->sw_if_index;
@@ -1149,7 +1160,9 @@ tap_connect_command_fn (vlib_main_t * vm,
     vnet_hw_interface_t * hw;
     hw = vnet_get_hw_interface (tm->vnet_main, ti->hw_if_index);
     ti->sw_if_index = hw->sw_if_index;
-    hw->max_l3_packet_bytes[VLIB_RX] = hw->max_l3_packet_bytes[VLIB_TX] = tm->mtu_bytes - sizeof(ethernet_header_t);
+    hw->min_supported_packet_bytes = TAP_MTU_MIN;
+    hw->max_supported_packet_bytes = TAP_MTU_MAX;
+    hw->max_l3_packet_bytes[VLIB_RX] = hw->max_l3_packet_bytes[VLIB_TX] = hw->max_supported_packet_bytes - sizeof(ethernet_header_t);
   }
 
   ti->active = 1;
@@ -1187,7 +1200,7 @@ tapcli_init (vlib_main_t * vm)
   tm->vlib_main = vm;
   tm->vnet_main = vnet_get_main();
   tm->unix_main = &unix_main;
-  tm->mtu_bytes = 4096 + 256;
+  tm->mtu_bytes = TAP_MTU_DEFAULT;
   tm->tapcli_interface_index_by_sw_if_index = hash_create (0, sizeof(uword));
   tm->tapcli_interface_index_by_unix_fd = hash_create (0, sizeof (uword));
   tm->rx_buffers = 0;