config: iproto section for instance config

This section describes the instance iproto configuration.

Part of #8778

NO_DOC=will be added later
NO_CHANGELOG=will be added later

src/box/lua/config/instance_config.lua

@@ -267,6 +267,39 @@ return schema.new('instance_config', schema.record({
             end
         end,
     }),
+    iproto = schema.record({
+        -- XXX: listen/advertise are specific: accept a string of
+        -- a particular format, a number (port), a table of a
+        -- particular format.
+        --
+        -- Only a string (without further validation) is accepted
+        -- for now.
+        listen = schema.scalar({
+            type = 'string',
+            box_cfg = 'listen',
+            default = box.NULL,
+        }),
+        advertise = schema.scalar({
+            type = 'string',
+            default = box.NULL,
+        }),
+        threads = schema.scalar({
+            type = 'integer',
+            box_cfg = 'iproto_threads',
+            box_cfg_nondynamic = true,
+            default = 1,
+        }),
+        net_msg_max = schema.scalar({
+            type = 'integer',
+            box_cfg = 'net_msg_max',
+            default = 768,
+        }),
+        readahead = schema.scalar({
+            type = 'integer',
+            box_cfg = 'readahead',
+            default = 16320,
+        }),
+    }),
 }, {
     -- Any configuration data should contain a version of the
     -- config schema for which it is written.

test/config-luatest/instance_config_schema_test.lua

@@ -192,3 +192,27 @@ g.test_log = function()
     local res = instance_config:apply_default({}).log
     t.assert_equals(res, exp)
 end
+
+g.test_iproto = function()
+    local iconfig = {
+        iproto = {
+            listen = 'one',
+            advertise = 'two',
+            threads = 1,
+            net_msg_max = 1,
+            readahead = 1,
+        },
+    }
+    instance_config:validate(iconfig)
+    validate_fields(iconfig.iproto, instance_config.schema.fields.iproto)
+
+    local exp = {
+        listen = box.NULL,
+        advertise = box.NULL,
+        threads = 1,
+        net_msg_max = 768,
+        readahead = 16320,
+    }
+    local res = instance_config:apply_default({}).iproto
+    t.assert_equals(res, exp)
+end