From 01820a672e37471f2e06e518e0ea4df983b5375c Mon Sep 17 00:00:00 2001
From: Timo Beckers <timo.beckers@klarrio.com>
Date: Fri, 17 Nov 2017 09:19:40 +0100
Subject: [PATCH] Set veth MTU using CALICO_LIBNETWORK_VETH_MTU

---
 driver/network_driver.go | 24 +++++++++++++++++++++---
 utils/netns/netns.go     |  3 ++-
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/driver/network_driver.go b/driver/network_driver.go
index f3e565f..00983e6 100644
--- a/driver/network_driver.go
+++ b/driver/network_driver.go
@@ -8,6 +8,7 @@ import (
 	"sort"
 	"strings"
 	"time"
+	"strconv"
 
 	"github.com/pkg/errors"
 	libcalicoErrors "github.com/projectcalico/libcalico-go/lib/errors"
@@ -29,6 +30,7 @@ const DOCKER_LABEL_PREFIX = "org.projectcalico.label."
 const LABEL_POLL_TIMEOUT_ENVKEY = "CALICO_LIBNETWORK_LABEL_POLL_TIMEOUT"
 const CREATE_PROFILES_ENVKEY = "CALICO_LIBNETWORK_CREATE_PROFILES"
 const LABEL_ENDPOINTS_ENVKEY = "CALICO_LIBNETWORK_LABEL_ENDPOINTS"
+const VETH_MTU_ENVKEY = "CALICO_LIBNETWORK_VETH_MTU"
 
 // NetworkDriver is the Calico network driver representation.
 // Must be used with Calico IPAM and supports IPv4 only.
@@ -42,6 +44,8 @@ type NetworkDriver struct {
 
 	DummyIPV4Nexthop string
 
+	vethMTU uint16
+
 	labelPollTimeout time.Duration
 
 	createProfiles bool
@@ -72,6 +76,20 @@ func NewNetworkDriver(client *datastoreClient.Client) network.Driver {
 		labelEndpoints: strings.EqualFold(os.Getenv(LABEL_ENDPOINTS_ENVKEY), "true"),
 	}
 
+	// Check if MTU environment variable is given, parse into uint16
+	// and override the default in the NetworkDriver.
+	if mtuStr, ok := os.LookupEnv(VETH_MTU_ENVKEY); ok {
+		mtu, err := strconv.ParseUint(mtuStr, 10, 16)
+		if err != nil {
+			log.Fatalf("Failed to parse %v '%v' into uint16: %v",
+				VETH_MTU_ENVKEY, mtuStr, err)
+		}
+
+		driver.vethMTU = uint16(mtu)
+
+		log.WithField("mtu", mtu).Info("Parsed veth MTU")
+	}
+
 	if !driver.createProfiles {
 		log.Info("Feature disabled: no Calico profiles will be created per network")
 	}
@@ -377,10 +395,10 @@ func (d NetworkDriver) Join(request *network.JoinRequest) (*network.JoinResponse
 	hostInterfaceName := "cali" + prefix
 	tempInterfaceName := "temp" + prefix
 
-	if err = netns.CreateVeth(hostInterfaceName, tempInterfaceName); err != nil {
+	if err = netns.CreateVeth(hostInterfaceName, tempInterfaceName, d.vethMTU); err != nil {
 		err = errors.Wrapf(
-			err, "Veth creation error, hostInterfaceName=%v, tempInterfaceName=%v",
-			hostInterfaceName, tempInterfaceName)
+			err, "Veth creation error, hostInterfaceName=%v, tempInterfaceName=%v, vethMTU=%v",
+			hostInterfaceName, tempInterfaceName, d.vethMTU)
 		log.Errorln(err)
 		return nil, err
 	}
diff --git a/utils/netns/netns.go b/utils/netns/netns.go
index 55ae5ee..38c4824 100644
--- a/utils/netns/netns.go
+++ b/utils/netns/netns.go
@@ -11,10 +11,11 @@ import (
 	"github.com/vishvananda/netlink"
 )
 
-func CreateVeth(vethNameHost, vethNameNSTemp string) error {
+func CreateVeth(vethNameHost, vethNameNSTemp string, vethMTU uint16) error {
 	veth := &netlink.Veth{
 		LinkAttrs: netlink.LinkAttrs{
 			Name: vethNameHost,
+			MTU: int(vethMTU),
 		},
 		PeerName: vethNameNSTemp,
 	}