CA-82314: networkd: introduce Linklocal6 IPv6 address mode

This commit redefines the IPv6 address mode "None6" to mean "no IPv6 address at
all, not even a link local one", and introduces the new mode Linklocal6, which
means "only IPv6 address, except a link local one".

Previously, it was not possible to get networkd to remove the link-local IPv6
address from an interface.

When a link local IPv6 address is requested, it is derived from the interface's
MAC address as commonly done.

Signed-off-by: Rob Hoes <[email protected]>
Imported-by: Jon Ludlam <[email protected]>

Author: Jon Ludlam

lib/network_utils.ml

@@ -234,6 +234,42 @@ info "Found at [ %s ]" (String.concat ", " (List.map string_of_int indices));
 			Some (ip, prefixlen)
 		with Not_found -> None
 
+	(* see http://en.wikipedia.org/wiki/IPv6_address#Modified_EUI-64 *)
+	let get_ipv6_interface_id dev =
+		let mac = get_mac dev in
+		let bytes = List.map (fun byte -> int_of_string ("0x" ^ byte)) (String.split ':' mac) in
+		let rec modified_bytes ac i = function
+			| [] ->
+				ac
+			| head :: tail ->
+				if i = 0 then
+					let head' = head lxor 2 in
+					modified_bytes (head' :: ac) 1 tail
+				else if i = 2 then
+					modified_bytes (254 :: 255 :: head :: ac) 3 tail
+				else
+					modified_bytes (head :: ac) (i + 1) tail
+		in
+		let bytes' = List.rev (modified_bytes [] 0 bytes) in
+		[0; 0; 0; 0; 0; 0; 0; 0] @ bytes'
+
+	let get_ipv6_link_local_addr dev =
+		let id = get_ipv6_interface_id dev in
+		let link_local = 0xfe :: 0x80 :: (List.tl (List.tl id)) in
+		let rec to_string ac i = function
+			| [] -> ac
+			| hd :: tl ->
+				let separator =
+					if i = 0 || i mod 2 = 1 then
+						""
+					else
+						":"
+				in
+				let ac' = ac ^ separator ^ Printf.sprintf "%02x" hd in
+				to_string ac' (i + 1) tl
+		in
+		to_string "" 0 link_local ^ "/64"
+
 	let get_ipv4 dev =
 		let addrs = addr dev "inet" in
 		List.filter_map split_addr addrs
@@ -254,13 +290,16 @@ info "Found at [ %s ]" (String.concat ", " (List.map string_of_int indices));
 			ignore (call ~log:true (["addr"; "add"; addr; "dev"; dev] @ broadcast))
 		with _ -> ()
 
+	let set_ipv6_link_local_addr dev =
+		let addr = get_ipv6_link_local_addr dev in
+		try
+			ignore (call ~log:true ["addr"; "add"; addr; "dev"; dev; "scope"; "link"])
+		with _ -> ()
+
 	let flush_ip_addr ?(ipv6=false) dev =
 		try
-			if ipv6 then begin
-				ignore (call ~log:true ["-6"; "addr"; "flush"; "dev"; dev; "scope"; "global"]);
-				ignore (call ~log:true ["-6"; "addr"; "flush"; "dev"; dev; "scope"; "site"])
-			end else
-				ignore (call ~log:true ["-4"; "addr"; "flush"; "dev"; dev])
+			let mode = if ipv6 then "-6" else "-4" in
+			ignore (call ~log:true [mode; "addr"; "flush"; "dev"; dev])
 		with _ -> ()
 
 	let route_show ?(version=V46) dev =

networkd/network_server.ml

@@ -194,20 +194,30 @@ module Interface = struct
 					Sysctl.set_ipv6_autoconf name false;
 					Ip.flush_ip_addr ~ipv6:true name
 				end
+			| Linklocal6 ->
+				if List.mem name (Sysfs.list ()) then begin
+					Dhcp6c.stop name;
+					Sysctl.set_ipv6_autoconf name false;
+					Ip.flush_ip_addr ~ipv6:true name;
+					Ip.set_ipv6_link_local_addr name
+				end
 			| DHCP6 ->
 				Dhcp6c.stop name;
 				Sysctl.set_ipv6_autoconf name false;
 				Ip.flush_ip_addr ~ipv6:true name;
+				Ip.set_ipv6_link_local_addr name;
 				Dhcp6c.start name
 			| Autoconf6 ->
 				Dhcp6c.stop name;
 				Ip.flush_ip_addr ~ipv6:true name;
+				Ip.set_ipv6_link_local_addr name;
 				Sysctl.set_ipv6_autoconf name true;
 				(* Cannot link set down/up due to CA-89882 - IPv4 default route cleared *)
 			| Static6 addrs ->
 				Dhcp6c.stop name;
 				Sysctl.set_ipv6_autoconf name false;
 				Ip.flush_ip_addr ~ipv6:true name;
+				Ip.set_ipv6_link_local_addr name;
 				List.iter (Ip.set_ip_addr name) addrs
 		) ()
 

networkd_db/networkd_db.ml

@@ -88,7 +88,7 @@ let _ =
 							| Some addr -> ["gatewayv6", Unix.string_of_inet_addr addr]
 						in
 						mode @ addrs @ gateway
-					| None6 -> []
+					| None6 | Linklocal6 -> []
 				in
 				let data = datav4 @ datav6 in
 				List.iter (fun (k, v) -> Printf.printf "%s=%s\n" k v) data