[FIX]fix GetRule method https://github.com/google/nftables/issues/114 && add GetTable and GetChain method to get specific data by name && add test files

.gitignore

@@ -0,0 +1 @@
+.idea/

README.md

@@ -1,6 +1,7 @@
 [![Build Status](https://github.com/google/nftables/actions/workflows/push.yml/badge.svg)](https://github.com/google/nftables/actions/workflows/push.yml)
 [![GoDoc](https://godoc.org/github.com/google/nftables?status.svg)](https://godoc.org/github.com/google/nftables)
 
+## 1. Introduction
 **This is not the correct repository for issues with the Linux nftables
 project!** This repository contains a third-party Go package to programmatically
 interact with nftables. Find the official nftables website at
@@ -11,14 +12,70 @@ implemented in pure Go, i.e. does not wrap libnftnl.
 
 This is not an official Google product.
 
-## Breaking changes
+## 2. Breaking changes
 
 This package is in very early stages, and only contains enough data types and
 functions to install very basic nftables rules. It is likely that mistakes with
 the data types/API will be identified as more functionality is added.
 
-## Contributions
+## 3. Contributions
 
 Contributions are very welcome!
 
 
+## 4. Examples
+
+### 1. Get common data types of Nftables
+
+#### 1.1. Get table by net family and its name
+
+```go
+conn := nftables.Conn{} // start up a conn
+
+table, _ := conn.GetTable("nat", nftables.TableFamilyIPv4)
+fmt.Println(table.Name)
+```
+#### 1.2. Get chain by chain's name
+
+```go
+conn := nftables.Conn{} // start up a conn
+chain, _ := conn.GetChain("POSTROUTING") // get chain
+fmt.Println(chain.Name)
+```
+
+#### 1.3. Get set and set's elements by table and set's name
+
+```go
+conn := nftables.Conn{} // start up a conn
+
+table, _ := conn.GetTable("nat", nftables.TableFamilyIPv4) // get table
+
+
+set, _ := conn.GetSetByName(table, "dest_addrs") // get set
+fmt.Println(set.Name)
+
+eles, _ := conn.GetSetElements(set)
+fmt.Println(eles)
+```
+
+#### 1.4. Get rules by table and chain
+
+```go
+    conn := nftables.Conn{} // start up a conn
+    
+    table, _ := conn.GetTable("nat", nftables.TableFamilyIPv4) // get table
+    chain, _ := conn.GetChain("POSTROUTING")                   // get chain
+    
+    rules, _ := conn.GetRule(table, chain) // get rules
+    for _, rule := range rules {
+        fmt.Println(rule.Table.Name, rule.Table.Family, rule.Chain.Name, rule.Handle)
+        // unpack exprs
+        for _, expr := range rule.Exprs {
+            fmt.Println(expr)
+        }
+    }
+```
+
+### 2. Insert common data types of Nftables
+
+**wait for update**

chain.go

@@ -205,6 +205,20 @@ func (cc *Conn) ListChains() ([]*Chain, error) {
 	return chains, nil
 }
 
+// GetChain gets a chain by name
+func (cc *Conn) GetChain(name string) (*Chain, error) {
+	chains, err := cc.ListChains()
+	if err != nil {
+		return nil, err
+	}
+	for _, chain := range chains {
+		if chain.Name == name {
+			return chain, nil
+		}
+	}
+	return nil, nil
+}
+
 func chainFromMsg(msg netlink.Message) (*Chain, error) {
 	chainHeaderType := netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_NEWCHAIN)
 	if got, want := msg.Header.Type, chainHeaderType; got != want {

rule.go

@@ -84,7 +84,10 @@ func (cc *Conn) GetRule(t *Table, c *Chain) ([]*Rule, error) {
 		if err != nil {
 			return nil, err
 		}
-		rules = append(rules, r)
+
+		if r.Table.Name == t.Name && r.Table.Family == t.Family && r.Chain.Name == c.Name {
+			rules = append(rules, r)
+		}
 	}
 
 	return rules, nil
@@ -293,6 +296,7 @@ func ruleFromMsg(msg netlink.Message) (*Rule, error) {
 		switch ad.Type() {
 		case unix.NFTA_RULE_TABLE:
 			r.Table = &Table{Name: ad.String()}
+			r.Table.Family = TableFamily(msg.Data[0])
 		case unix.NFTA_RULE_CHAIN:
 			r.Chain = &Chain{Name: ad.String()}
 		case unix.NFTA_RULE_EXPRESSIONS:

table.go

@@ -45,6 +45,23 @@ type Table struct {
 	Family TableFamily
 }
 
+// GetTable gets a table by name and family
+func (cc *Conn) GetTable(name string, family TableFamily) (*Table, error) {
+	cc.Lock()
+	defer cc.Unlock()
+
+	tables, err := cc.ListTables()
+	if err != nil {
+		return nil, err
+	}
+	for _, table := range tables {
+		if table.Name == name && table.Family == family {
+			return table, nil
+		}
+	}
+	return nil, nil
+}
+
 // DelTable deletes a specific table, along with all chains/rules it contains.
 func (cc *Conn) DelTable(t *Table) {
 	cc.Lock()

tests/get_data_test.go

@@ -0,0 +1,52 @@
+package tests
+
+import (
+	"fmt"
+	"github.com/google/nftables"
+	"testing"
+)
+
+// Get table by net family and its name
+func TestGetTable(t *testing.T) {
+	conn := nftables.Conn{} // start up a conn
+
+	table, _ := conn.GetTable("nat", nftables.TableFamilyIPv4)
+	fmt.Println(table.Name)
+}
+
+// Get chain by chain's name
+func TestGetChain(t *testing.T) {
+	conn := nftables.Conn{} // start up a conn
+	chain, _ := conn.GetChain("POSTROUTING") // get chain
+	fmt.Println(chain.Name)
+}
+
+// Get set and set's elements by table and set's name
+func TestGetSet(t *testing.T) {
+	conn := nftables.Conn{} // start up a conn
+
+	table, _ := conn.GetTable("nat", nftables.TableFamilyIPv4) // get table
+
+	set, _ := conn.GetSetByName(table, "dest_addrs") // get set
+	fmt.Println(set.Name)
+
+	eles, _ := conn.GetSetElements(set)
+	fmt.Println(eles)
+}
+
+// Get rules by table and chain
+func TestGetRules(t *testing.T) {
+	conn := nftables.Conn{} // start up a conn
+
+	table, _ := conn.GetTable("nat", nftables.TableFamilyIPv4) // get table
+	chain, _ := conn.GetChain("POSTROUTING")                   // get chain
+
+	rules, _ := conn.GetRule(table, chain) // get rules
+	for _, rule := range rules {
+		fmt.Println(rule.Table.Name, rule.Table.Family, rule.Chain.Name, rule.Handle)
+		// unpack exprs
+		for _, expr := range rule.Exprs {
+			fmt.Println(expr)
+		}
+	}
+}