mirror of
https://github.com/qdm12/gluetun.git
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Zhurik
41 lines
1.2 KiB
Go
41 lines
1.2 KiB
Go
package pmtud
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import (
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"net/netip"
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"github.com/qdm12/gluetun/internal/constants"
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"github.com/qdm12/gluetun/internal/constants/vpn"
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pconstants "github.com/qdm12/gluetun/internal/pmtud/constants"
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)
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// MaxTheoreticalVPNMTU returns the theoretical maximum MTU for a VPN tunnel
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// given the VPN type, network protocol, and VPN gateway IP address.
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// This is notably useful to skip testing MTU values higher than this value.
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// The function panics if the network or VPN type is unknown.
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func MaxTheoreticalVPNMTU(vpnType, network string, vpnGateway netip.Addr) uint32 {
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const physicalLinkMTU = pconstants.MaxEthernetFrameSize
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vpnLinkMTU := physicalLinkMTU
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if vpnGateway.Is4() {
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vpnLinkMTU -= pconstants.IPv4HeaderLength
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} else {
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vpnLinkMTU -= pconstants.IPv6HeaderLength
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}
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switch network {
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case constants.TCP:
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vpnLinkMTU -= pconstants.BaseTCPHeaderLength
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case constants.UDP:
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vpnLinkMTU -= pconstants.UDPHeaderLength
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default:
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panic("unknown network protocol: " + network)
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}
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switch vpnType {
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case vpn.Wireguard, vpn.AmneziaWg:
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vpnLinkMTU -= pconstants.WireguardHeaderLength
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case vpn.OpenVPN:
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vpnLinkMTU -= pconstants.OpenVPNHeaderMaxLength
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default:
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panic("unknown VPN type: " + vpnType)
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}
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return vpnLinkMTU
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}
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