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StackNode refactor: add offsetToIP argument to Encapsulate

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This commit is contained in:
Patricio Whittingslow
2025-12-19 00:38:28 -03:00
parent eaa36a589a
commit 1554b89a08
22 changed files with 180 additions and 94 deletions
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internet/definitions.go
+13 -8
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@@ -11,18 +11,21 @@ import (
// StackNode is an abstraction of a packet exchanging protocol controller. This is the building block for all protocols,
// from Ethernet to IP to TCP, practically any protocol can be expressed as a StackNode and function completely.
type StackNode interface {
// Encapsulate writes the stack node's frame into carrierData[frameOffset:]
// Encapsulate writes the stack node's frame into carrierData[offsetToFrame:]
// along with any other frame or payload the stack node encapsulates.
// The returned integer is amount of bytes written such that carrierData[frameOffset:frameOffset+n]
// contains written data. Data inside carrierData[:frameOffset] usually contains data necessary for
// The returned integer is amount of bytes written such that carrierData[offsetToFrame:offsetToFrame+n]
// contains written data. Data inside carrierData[:offsetToFrame] usually contains data necessary for
// a StackNode to correctly emit valid frame data: such is the case for TCP packets which require IP
// frame data for checksum calculation. Thus StackNodes must provide fields in their own frame
// required by sub-stacknodes for correct encapsulation; in the case of IPv4/6 this means including fields
// used in pseudo-header checksum like local IP (see [ipv4.CRCWriteUDPPseudo]).
//
// offsetToIP is the offset to the IP frame, if present, else its value should be -1.
// The relation offsetToIP<=offsetToFrame should always hold.
//
// When [net.ErrClosed] is returned the StackNode should be discarded and any written data passed up normally.
// Errors returned by Encapsulate are "extraordinary" and should not be returned unless the StackNode is receiving invalid carrierData/frameOffset.
Encapsulate(carrierData []byte, frameOffset int) (int, error)
Encapsulate(carrierData []byte, offsetToIP, offsetToFrame int) (int, error)
// Demux reads from the argument buffer where frameOffset is the offset of this StackNode's frame first byte.
// The stack node then dispatches(demuxes) the encapsulated frames to its corresponding sub-stack-node(s).
Demux(carrierData []byte, frameOffset int) error
@@ -38,10 +41,12 @@ type node struct {
currConnID uint64
connID *uint64
demux func([]byte, int) error
encapsulate func([]byte, int) (int, error)
encapsulate func([]byte, int, int) (int, error)
proto uint16
port uint16
remoteAddr []byte
// remoteAddr will be set on active(outbound) port connections
// that require an ARP to set the remoteAddr beforehand.
remoteAddr []byte
}
type handlers struct {
@@ -166,13 +171,13 @@ func (h *handlers) demuxByPort(buf []byte, offset int, port uint16) (*node, erro
// encapsulateAny finds a node suitable to write and encapsulates the package.
// If no data is sent it returns the last error encountered.
func (h *handlers) encapsulateAny(buf []byte, offset int) (_ *node, n int, err error) {
func (h *handlers) encapsulateAny(buf []byte, offsetIP, offsetThisFrame int) (_ *node, n int, err error) {
for i := range h.nodes {
node := &h.nodes[i]
if node.IsInvalid() {
continue
}
n, err = node.encapsulate(buf, offset)
n, err = node.encapsulate(buf, offsetIP, offsetThisFrame)
if h.tryHandleError(node, err) {
err = nil // CLOSE error handled gracefully by deleting node.
}