refactor: replace addr.HostAddr hierarchy with tagged union addr.Host (…

…#4346)

Replace the `addr.HostAddr` type hierarchy, consisting of the `HostAddr` interface and the `HostNone`, `HostIPv4`, `HostIPv6` and `HostSVC` implementations with a single type `addr.Host`, representing all the different host address types as a tagged union ("sum type"). This uses, and follows the spirit of, the `net/netip.Addr` types to represent IP addresses for both IPv4 and IPv6.

The `addr.Host` type is a simple value type, which can be created and copied without heap allocations and can be used in comparisons and as map keys.
In addition to replacing all uses of `addr.HostAddr`, the new `addr.Host` type is used in the `slayers.SCION.Get/SetSrc/DstAddr` interfaces, as well as in the DRKey infrastructure. Using a consistent representation of the addresses allows to get rid of duplicate functionality and a number of address conversions, e.g. in `snet`.
In contrast to the `addr.HostAddr` interface, the new `addr.Host`  does not implement the `net.Addr` interface. In particular, service addresses were passed through layers requiring a `net.Addr`. Use `snet.SVCAddr` in these cases.

Additionally, add a new `addr.Addr` type representing a full SCION address (ISD, AS and host address), including parsing functionality. This definition is identical to the `snet.SCIONAddress` type, which is now only kept as a type alias for compatibility.

Future work:
- `pkg/addr` is a public API and should have a more SCION-specific and less clash-likely name, e.g. `saddr`
- replace `snet.SCIONAddress` by  `addr.Addr`
- adopt using `addr.Addr` in the ping, traceroute etc tools, in place of the ill-fitting use of `snet.UDPAddr`.
- add `addr.MustParse{ISD,AS,IA}` for completeness sake (currently in xtest package)
- get rid of the IP-slice to `netip.Addr` conversions by gradually increasing the adoption of `netip.Addr` and related APIs

control/beaconing/writer.go

@@ -37,7 +37,7 @@ import (
 
 // Pather computes the remote address with a path based on the provided segment.
 type Pather interface {
-	GetPath(svc addr.HostSVC, ps *seg.PathSegment) (*snet.SVCAddr, error)
+	GetPath(svc addr.SVC, ps *seg.PathSegment) (*snet.SVCAddr, error)
 }
 
 // SegmentProvider provides segments to register for the specified type.

control/config/BUILD.bazel

@@ -11,7 +11,6 @@ go_library(
     importpath = "github.com/scionproto/scion/control/config",
     visibility = ["//visibility:public"],
     deps = [
-        "//pkg/addr:go_default_library",
         "//pkg/drkey:go_default_library",
         "//pkg/log:go_default_library",
         "//pkg/private/serrors:go_default_library",

control/config/drkey.go

@@ -20,7 +20,6 @@ import (
 	"strings"
 	"time"
 
-	"github.com/scionproto/scion/pkg/addr"
 	"github.com/scionproto/scion/pkg/drkey"
 	"github.com/scionproto/scion/pkg/private/serrors"
 	"github.com/scionproto/scion/private/config"
@@ -118,7 +117,7 @@ func (cfg *SecretValueHostList) Validate() error {
 			return serrors.New("GENERIC protocol is not allowed")
 		}
 		for _, ip := range list {
-			if h := addr.HostFromIPStr(ip); h == nil {
+			if _, err := netip.ParseAddr(ip); err != nil {
 				return serrors.New("Syntax error: not a valid address", "ip", ip)
 			}
 		}

control/drkey/grpc/drkey_service.go

@@ -299,7 +299,7 @@ func validateASHostReq(meta drkey.ASHostMeta, localIA addr.IA, peerAddr net.Addr
 		return serrors.New("invalid request, req.dstIA != localIA",
 			"request_dst_isd_as", meta.DstIA, "local_isd_as", localIA)
 	}
-	dstHost := addr.HostFromIPStr(meta.DstHost)
+	dstHost := net.ParseIP(meta.DstHost)
 	if !hostAddr.Equal(dstHost) {
 		return serrors.New("invalid request, dst_host != remote host",
 			"dst_host", dstHost, "remote_host", hostAddr)
@@ -320,7 +320,7 @@ func validateHostASReq(meta drkey.HostASMeta, localIA addr.IA, peerAddr net.Addr
 		return serrors.New("invalid request, req.SrcIA != localIA",
 			"request_src_isd_as", meta.SrcIA, "local_isd_as", localIA)
 	}
-	srcHost := addr.HostFromIPStr(meta.SrcHost)
+	srcHost := net.ParseIP(meta.SrcHost)
 	if !hostAddr.Equal(srcHost) {
 		return serrors.New("invalid request, src_host != remote host",
 			"src_host", srcHost, "remote_host", hostAddr)
@@ -335,8 +335,8 @@ func validateHostHostReq(meta drkey.HostHostMeta, localIA addr.IA, peerAddr net.
 	if err != nil {
 		return err
 	}
-	srcHost := addr.HostFromIPStr(meta.SrcHost)
-	dstHost := addr.HostFromIPStr(meta.DstHost)
+	srcHost := net.ParseIP(meta.SrcHost)
+	dstHost := net.ParseIP(meta.DstHost)
 
 	if !((meta.SrcIA.Equal(localIA) && hostAddr.Equal(srcHost)) ||
 		(meta.DstIA.Equal(localIA) && hostAddr.Equal(dstHost))) {
@@ -353,13 +353,13 @@ func validateHostHostReq(meta drkey.HostHostMeta, localIA addr.IA, peerAddr net.
 	return nil
 }
 
-func hostAddrFromPeer(peerAddr net.Addr) (addr.HostAddr, error) {
+func hostAddrFromPeer(peerAddr net.Addr) (net.IP, error) {
 	tcpAddr, ok := peerAddr.(*net.TCPAddr)
 	if !ok {
 		return nil, serrors.New("invalid peer address type, expected *net.TCPAddr",
 			"peer", peerAddr, "type", common.TypeOf(peerAddr))
 	}
-	return addr.HostFromIP(tcpAddr.IP), nil
+	return tcpAddr.IP, nil
 }
 
 func getMeta(protoId drkeypb.Protocol, ts *timestamppb.Timestamp, srcIA,

control/onehop/addr.go

@@ -35,7 +35,7 @@ type Addr struct {
 	// Egress is the interface over which the remote AS should be reached.
 	Egress uint16
 	// SVC is the service anycast address of the designated service in the remote AS.
-	SVC addr.HostSVC
+	SVC addr.SVC
 	// NextHop is the router that owns the egress interface.
 	NextHop *net.UDPAddr
 }

control/segreq/helpers.go

@@ -30,7 +30,7 @@ import (
 
 // Pather computes the remote address with a path based on the provided segment.
 type Pather interface {
-	GetPath(svc addr.HostSVC, ps *seg.PathSegment) (*snet.SVCAddr, error)
+	GetPath(svc addr.SVC, ps *seg.PathSegment) (*snet.SVCAddr, error)
 }
 
 // CoreChecker checks whether a given ia is core.

daemon/cmd/daemon/main.go

@@ -121,7 +121,7 @@ func realMain(ctx context.Context) error {
 	defer rcCleaner.Stop()
 
 	dialer := &libgrpc.TCPDialer{
-		SvcResolver: func(dst addr.HostSVC) []resolver.Address {
+		SvcResolver: func(dst addr.SVC) []resolver.Address {
 			if base := dst.Base(); base != addr.SvcCS {
 				panic("Unsupported address type, implementation error?")
 			}

daemon/drkey/grpc/BUILD.bazel

@@ -16,6 +16,7 @@ go_library(
         "//pkg/proto/control_plane:go_default_library",
         "//pkg/proto/drkey:go_default_library",
         "//pkg/scrypto/cppki:go_default_library",
+        "//pkg/snet:go_default_library",
         "@org_golang_google_protobuf//types/known/timestamppb:go_default_library",
     ],
 )

daemon/drkey/grpc/fetcher.go

@@ -22,6 +22,7 @@ import (
 	sc_grpc "github.com/scionproto/scion/pkg/grpc"
 	"github.com/scionproto/scion/pkg/private/serrors"
 	cppb "github.com/scionproto/scion/pkg/proto/control_plane"
+	"github.com/scionproto/scion/pkg/snet"
 )
 
 // Fetcher obtains end-host key from the local CS.
@@ -34,7 +35,7 @@ func (f *Fetcher) ASHostKey(
 	meta drkey.ASHostMeta,
 ) (drkey.ASHostKey, error) {
 
-	conn, err := f.Dialer.Dial(ctx, addr.SvcCS)
+	conn, err := f.Dialer.Dial(ctx, &snet.SVCAddr{SVC: addr.SvcCS})
 	if err != nil {
 		return drkey.ASHostKey{}, serrors.WrapStr("dialing", err)
 	}
@@ -59,7 +60,7 @@ func (f *Fetcher) HostASKey(
 	meta drkey.HostASMeta,
 ) (drkey.HostASKey, error) {
 
-	conn, err := f.Dialer.Dial(ctx, addr.SvcCS)
+	conn, err := f.Dialer.Dial(ctx, &snet.SVCAddr{SVC: addr.SvcCS})
 	if err != nil {
 		return drkey.HostASKey{}, serrors.WrapStr("dialing", err)
 	}
@@ -84,7 +85,7 @@ func (f *Fetcher) HostHostKey(
 	meta drkey.HostHostMeta,
 ) (drkey.HostHostKey, error) {
 
-	conn, err := f.Dialer.Dial(ctx, addr.SvcCS)
+	conn, err := f.Dialer.Dial(ctx, &snet.SVCAddr{SVC: addr.SvcCS})
 	if err != nil {
 		return drkey.HostHostKey{}, serrors.WrapStr("dialing", err)
 	}

daemon/fetcher/fetcher.go

@@ -126,7 +126,7 @@ type dstProvider struct {
 }
 
 func (r *dstProvider) Dst(_ context.Context, _ segfetcher.Request) (net.Addr, error) {
-	return addr.SvcCS, nil
+	return &snet.SVCAddr{SVC: addr.SvcCS}, nil
 }
 
 type neverLocal struct{}