From 9fca3640f9743862c4fa1f25e3cce5b026e7c2a5 Mon Sep 17 00:00:00 2001 From: Neil Alexander Date: Wed, 20 Nov 2019 22:11:52 +0000 Subject: [PATCH 1/2] Fix couple of issues with MTU calculations --- src/tuntap/tun.go | 19 +++++++------------ src/tuntap/tun_linux.go | 8 -------- 2 files changed, 7 insertions(+), 20 deletions(-) diff --git a/src/tuntap/tun.go b/src/tuntap/tun.go index ffee63b..c9a627a 100644 --- a/src/tuntap/tun.go +++ b/src/tuntap/tun.go @@ -170,22 +170,17 @@ func (tun *TunAdapter) _start() error { nodeID := crypto.GetNodeID(&boxPub) tun.addr = *address.AddrForNodeID(nodeID) tun.subnet = *address.SubnetForNodeID(nodeID) - tun.mtu = current.IfMTU - ifname := current.IfName - iftapmode := current.IfTAPMode addr := fmt.Sprintf("%s/%d", net.IP(tun.addr[:]).String(), 8*len(address.GetPrefix())-1) - if ifname != "none" { - if err := tun.setup(ifname, iftapmode, addr, tun.mtu); err != nil { - return err - } - if tun.MTU() != current.IfMTU { - tun.log.Warnf("Warning: Interface MTU %d automatically adjusted to %d (supported range is 1280-%d)", current.IfMTU, tun.MTU(), MaximumMTU(tun.IsTAP())) - } - } - if ifname == "none" || ifname == "dummy" { + if current.IfName == "none" || current.IfName == "dummy" { tun.log.Debugln("Not starting TUN/TAP as ifname is none or dummy") return nil } + if err := tun.setup(current.IfName, current.IfTAPMode, addr, current.IfMTU); err != nil { + return err + } + if tun.MTU() != current.IfMTU { + tun.log.Warnf("Warning: Interface MTU %d automatically adjusted to %d (supported range is 1280-%d)", current.IfMTU, tun.MTU(), MaximumMTU(tun.IsTAP())) + } tun.isOpen = true go tun.handler() tun.reader.Act(nil, tun.reader._read) // Start the reader diff --git a/src/tuntap/tun_linux.go b/src/tuntap/tun_linux.go index d3e9c85..b591832 100644 --- a/src/tuntap/tun_linux.go +++ b/src/tuntap/tun_linux.go @@ -27,14 +27,6 @@ func (tun *TunAdapter) setup(ifname string, iftapmode bool, addr string, mtu int } tun.iface = iface tun.mtu = getSupportedMTU(mtu, iftapmode) - // The following check is specific to Linux, as the TAP driver only supports - // an MTU of 65535-14 to make room for the ethernet headers. This makes sure - // that the MTU gets rounded down to 65521 instead of causing a panic. - if iftapmode { - if tun.mtu > 65535-tun_ETHER_HEADER_LENGTH { - tun.mtu = 65535 - tun_ETHER_HEADER_LENGTH - } - } // Friendly output tun.log.Infof("Interface name: %s", tun.iface.Name()) tun.log.Infof("Interface IPv6: %s", addr) From d06c40ad19dca10fa0c106be3cffe88ec1f0ea41 Mon Sep 17 00:00:00 2001 From: Neil Alexander Date: Wed, 20 Nov 2019 22:40:48 +0000 Subject: [PATCH 2/2] Use existing constant --- src/tuntap/tun.go | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/src/tuntap/tun.go b/src/tuntap/tun.go index c9a627a..d5bed52 100644 --- a/src/tuntap/tun.go +++ b/src/tuntap/tun.go @@ -102,7 +102,7 @@ func DefaultName() string { func DefaultMTU() int { ehbytes := 0 if DefaultIsTAP() { - ehbytes = 14 + ehbytes = tun_ETHER_HEADER_LENGTH } return defaults.GetDefaults().DefaultIfMTU - ehbytes } @@ -119,7 +119,7 @@ func DefaultIsTAP() bool { func MaximumMTU(iftapmode bool) int { ehbytes := 0 if iftapmode { - ehbytes = 14 + ehbytes = tun_ETHER_HEADER_LENGTH } return defaults.GetDefaults().MaximumIfMTU - ehbytes }