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Update MTU value for ethernet devices.

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L2 MTU includes both payload and ethernet header. gVisor has supported setting
data link layer MTU, it will be  up to users to set up proper value for a
device's MTU if a larger value is expected.

By doing the change, gVisor will be consistent with runc:

```shell
# runc
root@cec4d7238802:/# ip link set dev lo mtu 1234
root@cec4d7238802:/# ip link list dev lo
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 1234 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

# runsc before the change.
root@7cd89278d414:/# ip link set dev lo mtu 1234
root@7cd89278d414:/# ip link list dev lo
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 1220
    link/loopback 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff

# runsc after the change.
root@e811c5851226:/# ip link set dev lo mtu 1234
root@e811c5851226:/# ip link list dev lo
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 1234
    link/loopback 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
```
PiperOrigin-RevId: 684746090
This commit is contained in:
Jing Chen
2024-10-11 01:36:07 -07:00
committed by gVisor bot
parent 56ccc08f37
commit 35d3c6eb73
4 changed files with 7 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files
pkg/tcpip/link/ethernet/ethernet.go
+1 -4
View File
@@ -54,10 +54,7 @@ func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
// MTU implements stack.LinkEndpoint.
func (e *Endpoint) MTU() uint32 {
if mtu := e.Endpoint.MTU(); mtu > header.EthernetMinimumSize {
return mtu - header.EthernetMinimumSize
}
return 0
return e.Endpoint.MTU()
}
// DeliverNetworkPacket implements stack.NetworkDispatcher.
pkg/tcpip/link/ethernet/ethernet_test.go
+2 -10
View File
@@ -143,21 +143,13 @@ func TestMTU(t *testing.T) {
maxFrameSize: 0,
expectedMTU: 0,
},
{
maxFrameSize: header.EthernetMinimumSize - 1,
expectedMTU: 0,
},
{
maxFrameSize: header.EthernetMinimumSize,
expectedMTU: 0,
},
{
maxFrameSize: header.EthernetMinimumSize + 1,
expectedMTU: 1,
expectedMTU: header.EthernetMinimumSize,
},
{
maxFrameSize: maxFrameSize,
expectedMTU: maxFrameSize - header.EthernetMinimumSize,
expectedMTU: maxFrameSize,
},
}
test/rtnetlink/linux/setlink_test.sh
+1 -1
View File
@@ -20,7 +20,7 @@ source "$(dirname "$0")/rtnetlink_test.sh"
# Create a new veth pair in the current namespace and change the MTU.
ip link add name test_veth01 type veth peer name test_veth02
ip link set test_veth01 mtu 3000
ip link show test_veth01 | grep -E "mtu (2986|3000)"
ip link show test_veth01 | grep -E "mtu 3000"
ip link del name test_veth01
# Check that test_veth02 has been destroyed.
if ! wait_for ! ip link show test_veth02; then
test/syscalls/linux/socket_netlink_route.cc
+3 -5
View File
@@ -302,13 +302,11 @@ TEST_P(NetlinkSetLinkTest, ChangeMTU) {
req.ifm.ifi_index = loopback_link.index;
req.rtattr.rta_type = IFLA_MTU;
req.rtattr.rta_len = RTA_LENGTH(sizeof(uint32_t));
req.mtu = 1500;
ASSERT_NE(req.mtu, loopback_link.mtu);
req.mtu = loopback_link.mtu + 10;
EXPECT_NO_ERRNO(NetlinkRequestAckOrError(fd, kSeq, &req, sizeof(req)));
// See b/348220986, this is a known issue. The interface MTU is slightly
// different because of the package header size.
loopback_link.mtu = 1486;
// Update the local loopback_link's MTU to the requested value.
loopback_link.mtu = req.mtu;
// Verify the new MTU.
struct searchrequest {
struct nlmsghdr hdr;