From 76c7bc51b7b02c4ba83c0a064c3629bb5ee91340 Mon Sep 17 00:00:00 2001 From: Tony Gong Date: Tue, 7 Jul 2020 16:13:21 -0700 Subject: Set IPv4 ID on all non-atomic datagrams RFC 6864 imposes various restrictions on the uniqueness of the IPv4 Identification field for non-atomic datagrams, defined as an IP datagram that either can be fragmented (DF=0) or is already a fragment (MF=1 or positive fragment offset). In order to be compliant, the ID field is assigned for all non-atomic datagrams. Add a TCP unit test that induces retransmissions and checks that the IPv4 ID field is unique every time. Add basic handling of the IP_MTU_DISCOVER socket option so that the option can be used to disable PMTU discovery, effectively setting DF=0. Attempting to set the sockopt to anything other than disabled will fail because PMTU discovery is currently not implemented, and the default behavior matches that of disabled. PiperOrigin-RevId: 320081842 --- pkg/tcpip/transport/udp/endpoint.go | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'pkg/tcpip/transport/udp') diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go index cae29fbff..0584ec8dc 100644 --- a/pkg/tcpip/transport/udp/endpoint.go +++ b/pkg/tcpip/transport/udp/endpoint.go @@ -612,6 +612,13 @@ func (e *endpoint) SetSockOptBool(opt tcpip.SockOptBool, v bool) *tcpip.Error { // SetSockOptInt implements tcpip.Endpoint.SetSockOptInt. func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error { switch opt { + case tcpip.MTUDiscoverOption: + // Return not supported if the value is not disabling path + // MTU discovery. + if v != tcpip.PMTUDiscoveryDont { + return tcpip.ErrNotSupported + } + case tcpip.MulticastTTLOption: e.mu.Lock() e.multicastTTL = uint8(v) @@ -906,6 +913,10 @@ func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) { e.mu.RUnlock() return v, nil + case tcpip.MTUDiscoverOption: + // The only supported setting is path MTU discovery disabled. + return tcpip.PMTUDiscoveryDont, nil + case tcpip.MulticastTTLOption: e.mu.Lock() v := int(e.multicastTTL) -- cgit v1.2.3