From 570a75410197226e0985dfacddd69012acb14368 Mon Sep 17 00:00:00 2001
From: Louis Royer <infos.louis.royer@gmail.com>
Date: Fri, 21 Jun 2024 10:44:04 +0200
Subject: [PATCH] wip

---
 internal/ctrl/rules-registry.go         | 15 +++++++
 internal/netfunc/headend-encaps-ctrl.go | 60 +++++++++++++++++++++++++
 internal/netfunc/packet.go              | 12 +++++
 3 files changed, 87 insertions(+)

diff --git a/internal/ctrl/rules-registry.go b/internal/ctrl/rules-registry.go
index 426e236..9f5a0cc 100644
--- a/internal/ctrl/rules-registry.go
+++ b/internal/ctrl/rules-registry.go
@@ -7,6 +7,7 @@ package ctrl
 import (
 	"fmt"
 	"net/http"
+	"net/netip"
 	"sync"
 
 	"github.com/gin-gonic/gin"
@@ -26,6 +27,20 @@ func NewRulesRegistry() *RulesRegistry {
 	}
 }
 
+func (rr *RulesRegistry) Action(dstIp netip.Addr) (jsonapi.Action, error) {
+	rr.RLock()
+	defer rr.RUnlock()
+	for _, r := range rr.rules {
+		if !r.Enabled {
+			continue
+		}
+		if r.Match.DstIpPrefix.Contains(dstIp) {
+			return r.Action, nil
+		}
+	}
+	return jsonapi.Action{}, fmt.Errorf("Not found")
+}
+
 func (rr *RulesRegistry) GetRule(c *gin.Context) {
 	id := c.Param("uuid")
 	iduuid, err := uuid.FromString(id)
diff --git a/internal/netfunc/headend-encaps-ctrl.go b/internal/netfunc/headend-encaps-ctrl.go
index a1191ad..70d35da 100644
--- a/internal/netfunc/headend-encaps-ctrl.go
+++ b/internal/netfunc/headend-encaps-ctrl.go
@@ -6,6 +6,10 @@ package netfunc
 
 import (
 	"fmt"
+	"github.com/google/gopacket"
+	"github.com/google/gopacket/layers"
+	gopacket_srv6 "github.com/nextmn/gopacket-srv6"
+	"net"
 	"net/netip"
 
 	"github.com/nextmn/srv6/internal/ctrl"
@@ -25,5 +29,61 @@ func NewHeadendEncapsWithCtrl(prefix netip.Prefix, rr *ctrl.RulesRegistry, ttl u
 
 // Handle a packet
 func (h HeadendEncapsWithCtrl) Handle(packet []byte) ([]byte, error) {
+	pqt, err := NewIPv4Packet(packet)
+	if err != nil {
+		return nil, err
+	}
+	if err := h.CheckDAInPrefixRange(pqt); err != nil {
+		return nil, err
+	}
+	action, err := pqt.Action(h.RulesRegistry)
+	if err != nil {
+		return nil, err
+	}
+	src := net.ParseIP("::")           // FIXME: don't hardcode
+	nextHop := net.ParseIP(action.SRH) // FIXME: allow multiple segments
+	ipheader := &layers.IPv6{
+		SrcIP: src,
+		// S06. Set the IPv6 DA = B
+		DstIP:      nextHop,
+		Version:    6,
+		NextHeader: layers.IPProtocolIPv6Routing, // IPv6-Route
+		HopLimit:   h.HopLimit(),
+		// TODO: Generate a FlowLabel with hash(IPv6SA + IPv6DA + policy)
+		TrafficClass: 0, // FIXME: put this in Action
+	}
+	// FIXME: allow multiple segments
+	//segList := append([]net.IP{seg0}, bsid.ReverseSegmentsList()...)
+	segList := []net.IP{nextHop}
+	srh := &gopacket_srv6.IPv6Routing{
+		RoutingType: 4,
+		// the first item on segments list is the next endpoint
+		SegmentsLeft:     uint8(len(segList) - 1), // pointer to next segment
+		SourceRoutingIPs: segList,
+		Tag:              0, // not used
+		Flags:            0, // no flag defined
+		GopacketIpv6ExtensionBase: gopacket_srv6.GopacketIpv6ExtensionBase{
+			NextHeader: layers.IPProtocolIPv4,
+		},
+	}
+
+	// Encapsulate the packet into a new IPv6 header
+	buf := gopacket.NewSerializeBuffer()
+	if err := gopacket.SerializeLayers(buf,
+		gopacket.SerializeOptions{
+			FixLengths:       true,
+			ComputeChecksums: true,
+		},
+		ipheader,
+		srh,
+		gopacket.Payload(pqt.Packet.Layers()[0].LayerContents()),
+		gopacket.Payload(pqt.Packet.Layers()[0].LayerPayload()),
+	); err != nil {
+		return nil, err
+	} else {
+		// Forward along the shortest path to B
+		return buf.Bytes(), nil
+	}
+
 	return nil, fmt.Errorf("Not yet implemented")
 }
diff --git a/internal/netfunc/packet.go b/internal/netfunc/packet.go
index 239440b..7608384 100644
--- a/internal/netfunc/packet.go
+++ b/internal/netfunc/packet.go
@@ -11,7 +11,9 @@ import (
 
 	"github.com/google/gopacket"
 	"github.com/google/gopacket/layers"
+	json_api "github.com/nextmn/json-api/jsonapi"
 	"github.com/nextmn/srv6/internal/constants"
+	"github.com/nextmn/srv6/internal/ctrl"
 )
 
 type Packet struct {
@@ -72,6 +74,16 @@ func (p *Packet) CheckDAInPrefixRange(prefix netip.Prefix) error {
 	return nil
 }
 
+// Returns the Action related to this packet
+func (p *Packet) Action(rr *ctrl.RulesRegistry) (json_api.Action, error) {
+	dstSlice := p.NetworkLayer().NetworkFlow().Dst().Raw()
+	dst, ok := netip.AddrFromSlice(dstSlice)
+	if !ok {
+		return json_api.Action{}, fmt.Errorf("Malformed packet")
+	}
+	return rr.Action(dst)
+}
+
 // Returns the first gopacket.Layer after IPv6 header / extension headers
 func (p *Packet) PopIPv6Headers() (gopacket.Layer, error) {
 	if p.firstLayerType != layers.LayerTypeIPv6 {