From 32b823fcdb00a7d6eb5ddcd378f19a659edc3da3 Mon Sep 17 00:00:00 2001 From: Kevin Krakauer Date: Sun, 7 Jun 2020 13:37:25 -0700 Subject: netstack: parse incoming packet headers up-front Netstack has traditionally parsed headers on-demand as a packet moves up the stack. This is conceptually simple and convenient, but incompatible with iptables, where headers can be inspected and mangled before even a routing decision is made. This changes header parsing to happen early in the incoming packet path, as soon as the NIC gets the packet from a link endpoint. Even if an invalid packet is found (e.g. a TCP header of insufficient length), the packet is passed up the stack for proper stats bookkeeping. PiperOrigin-RevId: 315179302 --- pkg/tcpip/stack/registration.go | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'pkg/tcpip/stack/registration.go') diff --git a/pkg/tcpip/stack/registration.go b/pkg/tcpip/stack/registration.go index 94f177841..5cbc946b6 100644 --- a/pkg/tcpip/stack/registration.go +++ b/pkg/tcpip/stack/registration.go @@ -168,6 +168,11 @@ type TransportProtocol interface { // Wait waits for any worker goroutines owned by the protocol to stop. Wait() + + // Parse sets pkt.TransportHeader and trims pkt.Data appropriately. It does + // neither and returns false if pkt.Data is too small, i.e. pkt.Data.Size() < + // MinimumPacketSize() + Parse(pkt *PacketBuffer) (ok bool) } // TransportDispatcher contains the methods used by the network stack to deliver @@ -313,6 +318,14 @@ type NetworkProtocol interface { // Wait waits for any worker goroutines owned by the protocol to stop. Wait() + + // Parse sets pkt.NetworkHeader and trims pkt.Data appropriately. It + // returns: + // - The encapsulated protocol, if present. + // - Whether there is an encapsulated transport protocol payload (e.g. ARP + // does not encapsulate anything). + // - Whether pkt.Data was large enough to parse and set pkt.NetworkHeader. + Parse(pkt *PacketBuffer) (proto tcpip.TransportProtocolNumber, hasTransportHdr bool, ok bool) } // NetworkDispatcher contains the methods used by the network stack to deliver -- cgit v1.2.3