Set zone for link-local IP6 addr. Use numerical format (i.e., %3, not…

… %eth0)

Documentation updated as well, to usage of IP addresses

addressresolver.go

@@ -170,7 +170,7 @@ func addressResolverCallback(
 	clnt := resolver.clnt
 
 	// Generate an event
-	ip := decodeAvahiAddress(caddr)
+	ip := decodeAvahiAddress(IfIndex(ifidx), caddr)
 	evnt := &AddressResolverEvent{
 		Event:    ResolverEvent(event),
 		IfIdx:    IfIndex(ifidx),

doc.go

@@ -439,6 +439,24 @@ If this flag is in use, the following changes will occur:
     default [ProtocolIP6], to be consistent with other Avahi API
     (see section "IP4 vs IP6" for details).
 
+# IP addresses
+
+This package uniformly uses [netip.Addr] to represent addresses. Unlike
+[net.Addr], this format is compact, convenient and comparable.
+
+When addresses are received from Avahi (for example, as a part of
+[ServiceResolverEvent]), the following rules apply:
+  - IPv4 addresses are represented as 4-byte netip.Addr, not as
+    16-byte IP6-mapped IP4 addresses.
+  - Link-local IPv6 addresses come with zone. For zone, numerical,
+    not symbolic, format is used (i.e., fe80::1ff:fe23:4567:890a%3,
+    not fe80::1ff:fe23:4567:890a%eth2)
+
+When address is sent from application to Avahi, the following
+rules apply:
+  - Both genuine IP4 and IP6-mapped IP4 addresses are equally accepted
+  - For IP6 addresses, zone is ignored
+
 # The Poller
 
 [Poller] is the helper object that allows to simplify the event loop

glue.go

@@ -11,6 +11,7 @@ package avahi
 
 import (
 	"net/netip"
+	"strconv"
 	"unsafe"
 )
 
@@ -39,7 +40,7 @@ func makeAvahiAddress(addr netip.Addr) (C.AvahiAddress, error) {
 }
 
 // decodeAvahiAddress decodes C.AvahiAddress
-func decodeAvahiAddress(caddr *C.AvahiAddress) netip.Addr {
+func decodeAvahiAddress(ifindex IfIndex, caddr *C.AvahiAddress) netip.Addr {
 	var ip netip.Addr
 
 	switch {
@@ -52,6 +53,10 @@ func decodeAvahiAddress(caddr *C.AvahiAddress) netip.Addr {
 		ip = netip.AddrFrom16(*(*[16]byte)(unsafe.Pointer(&caddr.data)))
 	}
 
+	if ip.Is6() && ip.IsLinkLocalUnicast() {
+		ip = ip.WithZone(strconv.Itoa(int(ifindex)))
+	}
+
 	return ip
 }
 

hostnameresolver.go

@@ -231,7 +231,7 @@ func hostnameResolverCallback(
 	resolver := (*cgo.Handle)(p).Value().(*HostNameResolver)
 
 	// Generate an event
-	ip := decodeAvahiAddress(caddr)
+	ip := decodeAvahiAddress(IfIndex(ifidx), caddr)
 	evnt := &HostNameResolverEvent{
 		Event:    ResolverEvent(event),
 		IfIdx:    IfIndex(ifidx),

serviceresolver.go

@@ -229,7 +229,7 @@ func serviceResolverCallback(
 	clnt := resolver.clnt
 
 	// Decode IP address:port
-	ip := decodeAvahiAddress(caddr)
+	ip := decodeAvahiAddress(IfIndex(ifidx), caddr)
 
 	// Decode TXT record
 	txt := decodeAvahiStringList(ctxt)