udp: Add udp_set_source_membership binding + improve udp_set_membership

- Allows the interface argument of udp_set_membership to be nil (meaning a NULL const char* passed to uv_udp_set_membership). This was needed to be able to port the libuv multicast join tests
- Adds a binding for udp_set_source_membership (contributes towards #410)
- Ports the test-udp-multicast-join and test-udp-multicast-join6 tests from libuv

docs.md

@@ -1884,7 +1884,7 @@ Get the remote IP and port of the UDP handle on connected UDP handles.
 **Parameters:**
 - `udp`: `uv_udp_t userdata`
 - `multicast_addr`: `string`
-- `interface_addr`: `string`
+- `interface_addr`: `string` or `nil`
 - `membership`: `string`
 
 Set membership for a multicast address. `multicast_addr` is multicast address to
@@ -1893,6 +1893,23 @@ the string `"leave"` or `"join"`.
 
 **Returns:** `0` or `fail`
 
+### `uv.udp_set_source_membership(udp, multicast_addr, interface_addr, source_addr, membership)`
+
+> method form `udp:set_source_membership(multicast_addr, interface_addr, source_addr, membership)`
+
+**Parameters:**
+- `udp`: `uv_udp_t userdata`
+- `multicast_addr`: `string`
+- `interface_addr`: `string` or `nil`
+- `source_addr`: `string`
+- `membership`: `string`
+
+Set membership for a source-specific multicast group. `multicast_addr` is multicast
+address to set membership for. `interface_addr` is interface address. `source_addr`
+is source address. `membership` can be the string `"leave"` or `"join"`.
+
+**Returns:** `0` or `fail`
+
 ### `uv.udp_set_multicast_loop(udp, on)`
 
 > method form `udp:set_multicast_loop(on)`

src/luv.c

@@ -184,6 +184,9 @@ static const luaL_Reg luv_functions[] = {
   {"udp_bind", luv_udp_bind},
   {"udp_getsockname", luv_udp_getsockname},
   {"udp_set_membership", luv_udp_set_membership},
+#if LUV_UV_VERSION_GEQ(1, 32, 0)
+  {"udp_set_source_membership", luv_udp_set_source_membership},
+#endif
   {"udp_set_multicast_loop", luv_udp_set_multicast_loop},
   {"udp_set_multicast_ttl", luv_udp_set_multicast_ttl},
   {"udp_set_multicast_interface", luv_udp_set_multicast_interface},
@@ -488,6 +491,9 @@ static const luaL_Reg luv_udp_methods[] = {
   {"bind", luv_udp_bind},
   {"getsockname", luv_udp_getsockname},
   {"set_membership", luv_udp_set_membership},
+#if LUV_UV_VERSION_GEQ(1, 32, 0)
+  {"set_source_membership", luv_udp_set_source_membership},
+#endif
   {"set_multicast_loop", luv_udp_set_multicast_loop},
   {"set_multicast_ttl", luv_udp_set_multicast_ttl},
   {"set_multicast_interface", luv_udp_set_multicast_interface},

src/udp.c

@@ -120,12 +120,26 @@ static const char *const luv_membership_opts[] = {
 static int luv_udp_set_membership(lua_State* L) {
   uv_udp_t* handle = luv_check_udp(L, 1);
   const char* multicast_addr = luaL_checkstring(L, 2);
-  const char* interface_addr = luaL_checkstring(L, 3);
+  const char* interface_addr = lua_isstring(L, 3) ? lua_tostring(L, 3) : NULL;
+  luaL_argcheck(L, lua_isstring(L, 3) || lua_isnil(L, 3), 3, "expected string or nil");
   uv_membership membership = (uv_membership)luaL_checkoption(L, 4, NULL, luv_membership_opts);
   int ret = uv_udp_set_membership(handle, multicast_addr, interface_addr, membership);
   return luv_result(L, ret);
 }
 
+#if LUV_UV_VERSION_GEQ(1, 32, 0)
+static int luv_udp_set_source_membership(lua_State* L) {
+  uv_udp_t* handle = luv_check_udp(L, 1);
+  const char* multicast_addr = luaL_checkstring(L, 2);
+  const char* interface_addr = lua_isstring(L, 3) ? lua_tostring(L, 3) : NULL;
+  luaL_argcheck(L, lua_isstring(L, 3) || lua_isnil(L, 3), 3, "expected string or nil");
+  const char* source_addr = luaL_checkstring(L, 4);
+  uv_membership membership = (uv_membership)luaL_checkoption(L, 5, NULL, luv_membership_opts);
+  int ret = uv_udp_set_source_membership(handle, multicast_addr, interface_addr, source_addr, membership);
+  return luv_result(L, ret);
+}
+#endif
+
 static int luv_udp_set_multicast_loop(lua_State* L) {
   uv_udp_t* handle = luv_check_udp(L, 1);
   int on, ret;

tests/test-udp.lua

@@ -169,4 +169,78 @@ return require('lib/tap')(function (test)
       end))
     end)))
   end, "1.27.0")
+
+  -- return a test function reusable for ipv4 and ipv6
+  local function multicast_join_test(bind_addr, multicast_addr, interface_addr)
+    return function(print, p, expect, uv)
+      local uvVersionGEQ = require('lib/utils').uvVersionGEQ
+
+      local server = assert(uv.new_udp())
+      assert(uv.udp_bind(server, bind_addr, TEST_PORT))
+      local _, err, errname = uv.udp_set_membership(server, multicast_addr, interface_addr, "join")
+      if errname == "ENODEV" then
+        print("no ipv6 multicast route, skipping")
+        server:close()
+        return
+      end
+      assert(not err, err)
+
+      local client = assert(uv.new_udp())
+
+      local recv_cb_called = 0
+      local function recv_cb(err, data, addr, flags)
+        assert(not err, err)
+        p(data, addr)
+
+        assert(addr)
+        assert(data == "PING")
+
+        recv_cb_called = recv_cb_called + 1
+        if recv_cb_called == 2 then
+          server:close()
+        else
+          -- udp_set_source_membership added in 1.32.0
+          if uvVersionGEQ("1.32.0") then
+            local source_addr = addr.ip
+            assert(server:set_membership(multicast_addr, interface_addr, "leave"))
+            assert(server:set_source_membership(multicast_addr, interface_addr, source_addr, "join"))
+          end
+          assert(client:send("PING", multicast_addr, TEST_PORT, expect(function(err)
+            assert(not err, err)
+            client:close()
+          end)))
+        end
+      end
+
+      server:recv_start(expect(recv_cb, 2))
+
+      assert(client:send("PING", multicast_addr, TEST_PORT, expect(function(err)
+        assert(not err, err)
+      end)))
+    end
+  end
+
+  test("udp multicast join ipv4", multicast_join_test("0.0.0.0", "239.255.0.1", nil))
+
+  test("udp multicast join ipv6", function(print, p, expect, uv)
+    local function can_ipv6_external()
+      local addresses = assert(uv.interface_addresses())
+      for _, vals in pairs(addresses) do
+        for _, info in ipairs(vals) do
+          if info.family == "inet6" and not info.internal then
+            return true
+          end
+        end
+      end
+      return false
+    end
+
+    if not can_ipv6_external() then
+      print("no ipv6 support, skipping")
+      return
+    end
+
+    local testfn = multicast_join_test("::", "ff02::1", nil)
+    return testfn(print, p, expect, uv)
+  end)
 end)