feat(siit): Initial version (#8188)

* feat(siit): Initial version

Signed-off-by: Michée Lengronne <michee.lengronne@coppint.com>

* cleaner readme

Signed-off-by: Michée Lengronne <michee.lengronne@coppint.com>

* linting and generating

Signed-off-by: Michée Lengronne <michee.lengronne@coppint.com>

* improving README and removing a useless case

Signed-off-by: Michée Lengronne <michee.lengronne@coppint.com>

* improvements

Signed-off-by: Michée Lengronne <michee.lengronne@coppint.com>

* improvements

Signed-off-by: Michée Lengronne <michee.lengronne@coppint.com>

* linting

Signed-off-by: Michée Lengronne <michee.lengronne@coppint.com>

* New fixes

Signed-off-by: Michée Lengronne <michee.lengronne@coppint.com>

* improvements

Signed-off-by: Michée Lengronne <michee.lengronne@coppint.com>

* improvements

Signed-off-by: Michée Lengronne <michee.lengronne@coppint.com>

---------

Signed-off-by: Michée Lengronne <michee.lengronne@coppint.com>

plugin/siit/setup.go

@@ -0,0 +1,138 @@
+package siit
+
+import (
+	"net"
+
+	"github.com/coredns/caddy"
+	"github.com/coredns/coredns/core/dnsserver"
+	"github.com/coredns/coredns/plugin"
+	"github.com/coredns/coredns/plugin/pkg/upstream"
+)
+
+const pluginName = "siit"
+
+func init() { plugin.Register(pluginName, setup) }
+
+func setup(c *caddy.Controller) error {
+	siit, err := siitParse(c)
+	if err != nil {
+		return plugin.Error(pluginName, err)
+	}
+
+	dnsserver.GetConfig(c).AddPlugin(func(next plugin.Handler) plugin.Handler {
+		siit.Next = next
+		return siit
+	})
+
+	return nil
+}
+
+func siitParse(c *caddy.Controller) (*SIIT, error) {
+	_, defaultPref6, _ := net.ParseCIDR("64:ff9b::/96")
+	siit := &SIIT{
+		Upstream:   upstream.New(),
+		IPv6Prefix: defaultPref6,
+	}
+
+	for c.Next() {
+		args := c.RemainingArgs()
+		if len(args) > 0 {
+			return nil, c.ArgErr()
+		}
+
+		for c.NextBlock() {
+			switch c.Val() {
+			case "ipv6_prefix":
+				if !c.NextArg() {
+					return nil, c.ArgErr()
+				}
+				pref, err := parseIpv6Prefix(c, c.Val())
+
+				if err != nil {
+					return nil, err
+				}
+				siit.IPv6Prefix = pref
+			case "eam":
+				pref, err := parseEam(c)
+
+				if err != nil {
+					return nil, err
+				}
+
+				if siit.Eam4 == nil {
+					siit.Eam4 = make(map[string]net.IP)
+				}
+
+				siit.Eam4[pref[1].String()] = pref[0]
+			default:
+				return nil, c.Errf("unknown property '%s'", c.Val())
+			}
+		}
+	}
+	return siit, nil
+}
+
+func parseIpv6Prefix(c *caddy.Controller, addr string) (*net.IPNet, error) {
+	ip, pref, err := net.ParseCIDR(addr)
+	if err != nil {
+		return nil, err
+	}
+
+	// Test for valid prefix
+	n, total := pref.Mask.Size()
+	if total != 128 {
+		return nil, c.Errf("invalid netmask %d IPv6 address: %q", total, pref)
+	}
+
+	ip16 := ip.To16()
+	if ip16 == nil {
+		return nil, c.Errf("invalid IPv6 prefix %q", addr)
+	}
+
+	// RFC 6052 §2.2: only these lengths are valid.
+	switch n {
+	case 32, 40, 48, 56, 64, 96:
+		// ok
+	default:
+		return nil, c.Errf("invalid prefix length %q: must be one of /32, /40, /48, /56, /64, /96", pref)
+	}
+
+	// RFC 6052 §2.2: byte 8 (bits 64-71, the "u" octet) is reserved and
+	// MUST be zero for every valid prefix length — including /96, where
+	// it's still part of the operator-configured prefix bits.
+	if pref.IP.To16()[8] != 0 {
+		return nil, c.Errf("invalid prefix %q: reserved octet (byte 8) must be zero", pref)
+	}
+
+	return pref, nil
+}
+
+func parseEam(c *caddy.Controller) (map[int]net.IP, error) {
+	args := c.RemainingArgs()
+	if len(args) != 2 {
+		return nil, c.ArgErr()
+	}
+
+	pref0 := net.ParseIP(args[0])
+	if pref0 == nil {
+		return nil, c.Errf("invalid IP address: %q", pref0)
+	}
+
+	if pref0.To4() == nil {
+		return nil, c.Errf("invalid IPv4 address: %q", pref0)
+	}
+
+	pref1 := net.ParseIP(args[1])
+	if pref1 == nil {
+		return nil, c.Errf("invalid IP address: %q", pref1)
+	}
+
+	if pref1.To4() != nil {
+		return nil, c.Errf("invalid IPv6 address: %q", pref1)
+	}
+
+	pref := make(map[int]net.IP)
+	pref[0] = pref0
+	pref[1] = pref1
+	return pref, nil
+}