Add POST functionality to add set elements

Signed-off-by: Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>

nft.go

@@ -12,6 +12,8 @@
 package main
 
 import (
+	"bytes"
+	"errors"
 	"github.com/google/nftables"
 	"log"
 	"net"
@@ -25,22 +27,67 @@ func (nfterr nftError) Error() string {
 	return nfterr.Message
 }
 
-func handleNft(task string, set string) (any, error) {
+func handleNft(task string, givenSet string, givenAddress string) (any, error) {
 	nft, err := nftables.New()
 	if err != nil {
 		log.Println("handleNft():", err)
 		return "", err
 	}
 
-	if task == "get" {
-		nftResult, err := getNftSetElements(nft, set)
-		if err == nil {
-			return nftResult, nil
-		}
+	set, err := getNftSet(nft, givenSet)
+	if err != nil {
 		return nil, err
 	}
 
-	return "", nil
+	var element []nftables.SetElement
+
+	if task != "get" {
+		address, _ := parseIPAddress(givenAddress)
+		if address == nil {
+			return nil, errors.New("invalid address")
+		}
+
+		element = []nftables.SetElement{
+			{
+				Key: []byte(address),
+			},
+		}
+	}
+
+	var retmsg string
+
+	switch task {
+	case "get":
+		nftResult, err := getNftSetElements(nft, set)
+		if err != nil {
+			return nil, err
+		}
+		return nftResult, nil
+
+	case "add":
+		contains, err := containsNftSetElement(nft, set, element)
+		if err != nil {
+			return nil, err
+		}
+		if contains {
+			return "already", nil
+		} else {
+			err := nft.SetAddElements(set, element)
+			if err != nil {
+				log.Println("handleNft() add failure:", err)
+				return nil, err
+			}
+			retmsg = "added"
+		}
+	}
+
+	fErr := nft.Flush()
+	if fErr != nil {
+		log.Println("nftablesHandler: failed to save changes: %w", fErr)
+		return nil, fErr
+	}
+
+	return retmsg, nil
 }
 
 func getNftTable(nft *nftables.Conn) (*nftables.Table, error) {
@@ -77,7 +124,7 @@ func getNftSet(nft *nftables.Conn, setName string) (*nftables.Set, error) {
 	}
 	foundSet, err := nft.GetSetByName(foundTable, setName)
 	if err != nil || foundSet == nil {
-		log.Printf("Set lookup for %s failed, cannot proceed: %s", setName, err)
+		log.Printf("Set lookup for %s failed: %s", setName, err)
 		return nil, err
 	}
 	log.Printf("Found set %s", foundSet.Name)
@@ -85,13 +132,7 @@ func getNftSet(nft *nftables.Conn, setName string) (*nftables.Set, error) {
 	return foundSet, nil
 }
 
-func getNftSetElements(nft *nftables.Conn, setName string) ([]string, error) {
-	set, err := getNftSet(nft, setName)
-	if err != nil {
-		log.Printf("Could not retrieve set elements")
-		return nil, err
-	}
-
+func getNftSetElements(nft *nftables.Conn, set *nftables.Set) ([]string, error) {
 	setElements, err := nft.GetSetElements(set)
 	if err != nil {
 		return nil, err
@@ -107,3 +148,20 @@ func getNftSetElements(nft *nftables.Conn, setName string) ([]string, error) {
 
 	return returnElements, nil
 }
+
+func containsNftSetElement(nft *nftables.Conn, set *nftables.Set, element []nftables.SetElement) (bool, error) {
+
+	existingElements, err := nft.GetSetElements(set)
+	if err != nil {
+		return false, err
+	}
+
+	for _, existingElement := range existingElements {
+		if bytes.Equal(existingElement.Key, element[0].Key) {
+			log.Printf("Existing element found %v", existingElement.Key)
+			return true, nil
+		}
+	}
+
+	return false, nil
+}

nftables-http-api.go

@@ -12,6 +12,7 @@
 package main
 
 import (
+	"encoding/json"
 	"flag"
 	"github.com/gorilla/mux"
 	"gopkg.in/yaml.v3"
@@ -66,6 +67,10 @@ func (authMiddleWare *authMiddleWareMap) Middleware(next http.Handler) http.Hand
 	})
 }
 
+type addressPayload struct {
+	Address string
+}
+
 func main() {
 	flag.Parse()
 	log.Print("Booting ...")
@@ -86,7 +91,7 @@ func main() {
 	log.Print("Listening on ", listen)
 
 	router := mux.NewRouter()
-	router.HandleFunc("/set/{set}", handleSetRoute).Methods("GET")
+	router.HandleFunc("/set/{set}", handleSetRoute).Methods("GET", "POST")
 
 	authMiddleWare := authMiddleWareMap{make(map[string]string)}
 	router.Use(authMiddleWare.Middleware)
@@ -101,13 +106,37 @@ func handleSetRoute(w http.ResponseWriter, r *http.Request) {
 	set := params["set"]
 	log.Printf("Processing authorized %s request from %s for set %s", method, r.RemoteAddr, set)
 
-	if method == "GET" {
-		nftResult, err := handleNft("get", set)
-		if err != nil {
-			doReturn(w, http.StatusInternalServerError, "nftables failure")
+	switch method {
+	case "GET":
+		nftResult, err := handleNft("get", set, "")
+		if err != nil || nftResult == nil {
+			doReturn(w, http.StatusInternalServerError, err.Error())
+			return
 		}
-		if nftResult != nil {
-			doReturnSet(w, http.StatusOK, "", nftResult.([]string))
+		doReturnSet(w, http.StatusOK, "", nftResult.([]string))
+
+	case "POST":
+		var payload addressPayload
+		decErr := json.NewDecoder(r.Body).Decode(&payload)
+		if decErr != nil {
+			doReturn(w, http.StatusBadRequest, decErr.Error())
+			return
+		}
+
+		nftResult, err := handleNft("add", set, payload.Address)
+		if err != nil || nftResult == nil {
+			doReturn(w, http.StatusInternalServerError, err.Error())
+			return
+		}
+		switch nftResult {
+		case "already":
+			doReturn(w, http.StatusOK, "already exists")
+		case "added":
+			doReturn(w, http.StatusCreated, "ok")
+		case nil:
+			doReturn(w, http.StatusInternalServerError, "failure")
+		default:
+			doReturn(w, http.StatusInternalServerError, "unhandled result")
 		}
 	}
 }

utils.go

@@ -32,7 +32,7 @@ type ResponseSet struct {
 
 func doReturn(w http.ResponseWriter, status int, text string) {
 	var response any
-	if status == http.StatusOK {
+	if status == http.StatusOK || status == http.StatusCreated {
 		response = Response{RResult: text}
 	} else {
 		response = Response{RError: text}