fix(client): pack all zero netmask

An IPv6 netmask prefix of 0 is distinct from the Mask's zero case, and
should be encoded into the netlink message. This matches the behavior of
libipvs.

client_linux.go

@@ -512,7 +512,7 @@ func packService(svc Service) func() ([]byte, error) {
 		case svc.Netmask.Is4():
 			ae.Bytes(cipvs.SvcAttrNetmask, svc.Netmask.AsSlice())
 		case svc.Netmask.Is6():
-			if ones := svc.Netmask.Bits(); ones > 0 {
+			if ones := svc.Netmask.Bits(); ones >= 0 {
 				b := make([]byte, 4)
 				nlenc.PutUint32(b, uint32(ones))
 				ae.Bytes(cipvs.SvcAttrNetmask, b)

client_linux_test.go

@@ -5,9 +5,11 @@ package ipvs
 
 import (
 	"io"
+	"net"
 	"net/netip"
 	"os"
 	"testing"
+	"unicode"
 
 	"github.com/cloudflare/ipvs/internal/cipvs"
 	"github.com/cloudflare/ipvs/netmask"
@@ -17,6 +19,7 @@ import (
 	"github.com/mdlayher/netlink"
 	"github.com/mdlayher/netlink/nltest"
 	"gotest.tools/v3/assert"
+	"pgregory.net/rapid"
 )
 
 const familyID = 0x24
@@ -282,6 +285,55 @@ func TestServices(t *testing.T) {
 	}
 }
 
+func TestService_PackUnpack(t *testing.T) {
+	rapid.Check(t, func(t *rapid.T) {
+		svc := rapid.Custom[Service](func(t *rapid.T) Service {
+			family := rapid.SampledFrom([]AddressFamily{INET, INET6}).Draw(t, "Family")
+			var addr netip.Addr
+			var mask netmask.Mask
+
+			switch family {
+			case INET:
+				addr, _ = netip.AddrFromSlice(rapid.SliceOfN(rapid.Byte(), net.IPv4len, net.IPv4len).Draw(t, "Address"))
+				mask = netmask.MaskFrom(rapid.IntRange(0, 32).Draw(t, "ones"), 32)
+			case INET6:
+				addr, _ = netip.AddrFromSlice(rapid.SliceOfN(rapid.Byte(), net.IPv6len, net.IPv6len).Draw(t, "Address"))
+				mask = netmask.MaskFrom(rapid.IntRange(0, 128).Draw(t, "ones"), 128)
+			}
+
+			return Service{
+				Address:   addr,
+				Netmask:   mask,
+				Scheduler: rapid.StringOf(rapid.RuneFrom(nil, unicode.Letter, unicode.Number)).Draw(t, "Scheduler"),
+				Timeout:   rapid.Uint32().Draw(t, "Timeout"),
+				Flags:     Flags(rapid.Uint32().Draw(t, "Flags")),
+				Port:      rapid.Uint16().Draw(t, "Port"),
+				Family:    family,
+				Protocol:  Protocol(rapid.Uint16().Draw(t, "Protocol")),
+			}
+		}).Draw(t, "svc")
+
+		ae := netlink.NewAttributeEncoder()
+		ae.Do(cipvs.CmdAttrService, packService(svc))
+		p, err := ae.Encode()
+
+		assert.NilError(t, err)
+
+		ad, err := netlink.NewAttributeDecoder(p)
+		assert.NilError(t, err)
+
+		var out ServiceExtended
+		for ad.Next() {
+			if ad.Type() == cipvs.CmdAttrService {
+				ad.Do(unpackService(&out))
+			}
+		}
+
+		assert.NilError(t, ad.Err())
+		assert.DeepEqual(t, out.Service, svc, cmp.Comparer(NetipAddrCompare))
+	})
+}
+
 func TestDestinations_Pack(t *testing.T) {
 	type testCase struct {
 		name        string

testdata/rapid/TestService_PackUnpack/TestService_PackUnpack-20240707010805-1321460.fail

@@ -0,0 +1,77 @@
+# 2024/07/07 01:08:05.415620 [TestService_PackUnpack] [rapid] draw svc: ipvs.Service{Address:netip.Addr{addr:netip.uint128{hi:0x0, lo:0x0}, z:(*intern.Value)(0xc00011c0a8)}, Netmask:netmask.Mask{mask:0x0, z:2}, Scheduler:"", Timeout:0x0, Flags:0x0, Port:0x0, FWMark:0x0, Family:0xa, Protocol:0x0}
+# 2024/07/07 01:08:05.416260 [TestService_PackUnpack] assertion failed: 
+# --- out.Service
+# +++ svc
+#   ipvs.Service{
+#   	Address:   s"::",
+# - 	Netmask:   s"invalid Mask",
+# + 	Netmask:   s"0",
+#   	Scheduler: "",
+#   	Timeout:   0,
+#   	... // 5 identical fields
+#   }
+# 
+v0.4.8#30582461511489384
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